A drone vehicle for performing maintenance on a railway system is provided. A drone vehicle control system is structured to utilize tie position data to position a drone vehicle workhead over at least a portion of a respective tie. The drone vehicle control system is further structured to actuate the drone vehicle workhead. The drone vehicle may be controlled by a drone vehicle control system linked, preferably by wireless communications, to a lead vehicle and a lead vehicle control system. The lead vehicle control system and the drone vehicle control system are structured to communicate with each other, with the lead vehicle control system providing the tie position data to the drone vehicle control system.

CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/827,596, entitled “Drone Vehicle,” filed on Jun. 30, 2010 which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to railroad tampers and, more specifically, to a tamping system utilizing a drone tamper that follows a lead tamper. 
     BACKGROUND OF THE INVENTION 
     Generally, a railroad includes at least one pair of elongated, substantially parallel rails coupled to a plurality of laterally extending ties which are disposed on a ballast bed. The rails are coupled to the ties by metal tie plates and spikes and/or spring clip fasteners. The ballast is a hard particulate material such as, but not limited to, gravel. Ties may be made from either concrete or wood. The ballast filled space between ties is called a crib. Concrete ties are typically spaced about twenty-four inches apart, whereas wood ties are spaced about nineteen and a half inches apart. However, ties may be “skewed” relative to the rails. That is, the ties may be crooked and not extend generally laterally, i.e. perpendicular to, the rails. 
     During installation and maintenance of the railroad, the ballast adjacent and/or under the ties must be “tamped,” or compressed, to ensure that the ties, and therefore the rails, do not shift. While it is the ballast material that is being tamped, it is common to refer to this operation as tamping a “tie.” It is understood that tamping, or otherwise having a tamper assembly engage, a “tie” means that the ballast adjacent/below the indicated tie is being tamped/engaged. As used herein, the tie(s) which are being tamped/engaged shall be identified as a “worksite tie.” When the tamper vehicle advances, another tie becomes the “worksite tie.” 
     A tamping device, and/or the vehicle that supports the tamping device, is called a “tamper.” As used herein, the vehicle supporting the tamper shall be identified as the “tamper vehicle.” The tamper vehicle typically supports at least a pair of tamper assemblies. Each tamper assembly typically consists of one pair of workheads. A workhead includes at least two vibration devices each with a pair of elongated, vertically extending tools structured to move together in a pincer-like motion as well as being structured to move vertically. The vertically extending, and more specifically, vertically descending tool may have a single prong or multiple prongs. A vibration device is coupled to each tool and is structured to vibrate each tool. As the tools are structured to move together in a pincer-like motion, the tools of each of the workheads are disposed on opposite sides of a tamper assembly centerline. In this configuration, a workhead may be disposed above a worksite tie with one or more tools on either side of the rail at the worksite tie. 
     Because it is desirable to tamp the ballast on both the inner and outer sides of the rail, each of the workheads may have two adjacent pairs of tools; one tool disposed on the outer side of the rail, and one tool disposed on the inner side of the rail. In this configuration, the tools disposed on one side of a worksite tie may share a vibration device. 
     Thus, a tamper assembly is structured to engage the ballast at eight locations at each worksite tie; one tool set engages the forward side of the tie on the outer side of the rail, one tool set engages the rearward side of the tie on the outer side of the rail, one tool set engages the forward side of the tie on the inner side of the rail, one tool set engages the rearward side of the tie on the inner side of the rail. This is repeated on the tie/rail intersection of the opposite side. 
     In another configuration, a workhead may be disposed above a rail with one tool set on either side of the worksite at the rail. In this configuration the tools on the outside of the rail are driven by one vibrator, while the tools on the inside of the rail are driven by a separate vibrator. This is also repeated on the tie/rail intersection of the opposite side. 
     Initially, the tools are generally vertical and parallel to each other. When actuated, each workhead moves vertically downward so that the tips of the tools, that are the lower, distal ends of the prongs, are inserted into the ballast to a predetermined depth. The depth is, preferably, below the bottom of the tie. The tools are then brought together in a pincer-like motion thereby compressing the ballast under the tie. Actuation of the vibration device further compresses the ballast under the tie. Once the vibration operation is complete, the tools are returned to a substantially vertical orientation and lifted out of the ballast. The tamper vehicle then advances to the next worksite tie and the operation is repeated. Typically, a tamping operation lasts about three seconds. 
     Some tamper vehicles use more than one pair of tamper assemblies. That is, one pair of tamper assemblies is disposed forward but adjacent the other pair of tamper assemblies on the tamper vehicle. When there are two pairs of tamper assemblies, and if one were to alternately identify the ties in a series of ties as being “odd” or “even” ties, one pair of tamper assemblies tamps the “odd” ties and the other pair of tamper assemblies tamps the “even” ties. Thus, multiple ties may be tamped at one time. 
     Where there are two pairs of tool heads, two configurations are commonly used. In one configuration, as identified above, the two pairs of tamper assemblies are disposed adjacent each other on the same tamper vehicle body. In this configuration, the two pairs of tamper assemblies typically operate on adjacent ties. One problem with this configuration is that when the ties are disposed too close to each other, or when one tie is skewed so that one end of a tie is close to an adjacent tie, the two pairs of tool heads may not fit into the space above the ties. If this happens, the operator must disengage one of the two pairs of tool heads and tamp the ties individually. These problems are typically encountered with wood ties. 
     In another configuration, the second pair of tool heads is disposed on a “chase” vehicle. The chase vehicle typically does not include various components associated with a complete tamper vehicle, e.g. a tie locator, track lifting devices, lining devices, clamps, reference system. Further, the chase vehicle typically requires its own tamper assembly operator. 
     SUMMARY OF THE INVENTION 
     The present concept is an improvement over the prior art and provides for a drone tamper having a control system and at least two tamper assemblies. The pair of tamper assemblies operates as described above. The drone tamper is controlled by a computer system linked, preferably by wireless communications, to a tamper vehicle. The tamper vehicle, and more specifically its control system, locates and tracks the location of ties and communicates this data to the drone control system. The drone control system tracks the location of the longitudinally shifting pair of tamper assemblies. The drone control system then actuates the tamper assemblies when the tool heads are located over a tie that has not been tamped by the tamper vehicle. 
     One aspect of the invention is directed to a drone vehicle for use with a lead vehicle for performing maintenance on a railway system. The lead vehicle includes a lead vehicle control system which has tie position data communicated thereto. The drone vehicle has a drone vehicle body having a drone vehicle propulsion device, a drone vehicle control system, at least one drone vehicle workhead structured to perform maintenance on the railroad, and a drone vehicle tie locator. The drone vehicle tie locator is in electronic communication with the drone vehicle control system. The lead vehicle control system and the drone vehicle control system are structured to communicate with each other, with the lead vehicle control system providing the tie position data to the drone vehicle control system. The drone vehicle control system is structured to utilize the tie position data to position the drone vehicle workhead over at least a portion of a respective tie. The drone vehicle control system is further structured to actuate the drone vehicle workhead. 
     Another aspect of the invention is directed to a maintenance vehicle which is structured to operate on a railroad. The railroad has a ballast bed; at least two elongated, generally parallel rails; and a plurality of ties, said ties disposed on said ballast bed, said rails being coupled to each of said plurality of ties. The maintenance vehicle has a lead vehicle and a drone vehicle. The lead vehicle includes a lead vehicle body, a lead vehicle propulsion device, a lead vehicle control system, at least one lead vehicle workhead structured to perform maintenance on the railroad, a lead vehicle tie locator and an associated lead vehicle encoder wheel. The lead vehicle tie locator and the lead vehicle encoder wheel are in electronic communication with the lead vehicle control system. The lead vehicle tie locator and the lead vehicle encoder wheel are structured to create tie position data, with the tie position data being communicated to the lead vehicle control system. The lead vehicle control system is structured to utilize the tie position data to position the lead vehicle workhead over at least a portion of a first respective tie. The lead vehicle control system is further structured to actuate the lead vehicle workhead. The drone vehicle includes a drone vehicle body having a drone vehicle propulsion device, a drone vehicle control system, at least one drone vehicle workhead structured to perform maintenance on the railroad, a drone vehicle tie locator and an associated drone vehicle encoder wheel. The drone vehicle tie locator and the drone vehicle encoder wheel are in electronic communication with the drone vehicle control system. The lead vehicle control system and the drone vehicle control system are structured to communicate with each other, with the lead vehicle control system providing the tie position data to the drone vehicle control system. The drone vehicle control system is structured to utilize the tie position data to position the drone vehicle workhead over at least a portion of a second respective tie. The drone vehicle control system is further structured to actuate the drone vehicle workhead. 
     Another aspect of the invention is directed to a drone tamper structured to operate with a tamper vehicle on a railroad, the railroad having a ballast bed; at least two elongated, generally parallel rails; and a plurality of ties, said ties disposed on said ballast bed, said rails being coupled to each of said plurality of ties. The tamper vehicle is structured to travel over said rails and includes a body, a propulsion device, a control system, at least one pair of tamper assemblies structured to tamp a tie, a tie locator and an associated encoder wheel. The tamper vehicle tie locator and the tamper vehicle encoder wheel are in electronic communication with the tamper vehicle control system. The tamper vehicle tie locator and associated tamper vehicle encoder wheel are structured to create tie position data, with the tie position data being communicated to the tamper vehicle control system. The tamper vehicle control system is structured to utilize the tie position data to position the tamper vehicle tamper assemblies over at least a portion of the ties. The tamper vehicle control system is further structured to actuate the tamper vehicle tamper assemblies. The drone tamper has a drone vehicle body structured to support at least one pair of tamper assembly workhead. The drone vehicle body is structured to travel over the rails. A propulsion device is coupled to the drone vehicle body and is structured to propel the drone vehicle body. At least one pair of tamper assembly workheads is coupled to the drone vehicle body. The at least one pair of tamper assembly workheads is structured to tamp the ballast. A control system is structured to operate the at least one pair of tamper tool heads. 
     Another aspect of the invention is directed to a drone tamper structured to operate on a railroad, the railroad having a ballast bed; at least two elongated, generally parallel rails; and a plurality of ties, the ties disposed on the ballast bed, the rails being coupled to each of the plurality of ties. The drone tamper is structured to travel over the rails. The drone tamper has a vehicle body structured to support at least one pair of tamper assembly workheads. The vehicle body is structured to travel over the rails. A propulsion device is coupled to the vehicle body and structured to propel the vehicle body. At least one pair of tamper assembly workheads is coupled to the vehicle body. The at least one pair of tamper assembly workheads is structured to tamp the ballast. A control system is structured to operate the at least one pair of tamper tool heads. A tie locator and an encoder wheel are in electronic communication with the control system, whereby the tie locator and the encoder wheel create tie position data. 
     Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which: 
         FIG. 1  is a side view of a tamper system. 
         FIG. 2  is an upward isometric view of a lead tamper vehicle. 
         FIG. 3  is a side view of a drone tamper. 
         FIG. 4  is an isometric view of a drone tamper. 
         FIG. 5  is a top view of a drone tamper. 
         FIG. 6  is an upward isometric view of a drone tamper. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As used herein, a “drone” or “drone vehicle” is a vehicle structured to operate without direct human control. 
     As used herein, a “worksite tie” is the tie located below a tamper assembly or tamper workhead. Thus, as the rail vehicle moves, different ties each become a “worksite tie” in turn. 
     As used herein, the “longitudinal” direction of the rail vehicle extends generally parallel to the direction of the rails of the railroad. Thus, the “lateral direction” extends generally perpendicular to the direction of the rails of the railroad. 
     As used herein, “forward” and “rearward,” as well as similar words, relate to the direction a rail vehicle is traveling. These words shall apply to the initial direction the rail vehicle is described as traveling and shall maintain their meaning even if a further description has the rail vehicle reverse direction. 
     As used herein “rail wheels” are wheels structured to support the weight of a rail vehicle. Other wheels, such as, but not limited to, wheels on a distance encoding device are not rail wheels even if such an encoder wheel travels along a rail. 
     As used herein, “coupled” means a link between two or more elements, whether direct or indirect, so long as a link occurs. 
     As used herein, “directly coupled” means that two elements are directly in contact with each other. 
     As used herein, “fixedly coupled” or “fixed” means that two components are coupled so as to move as one while maintaining a constant orientation relative to each other. 
     As shown in  FIG. 1 , a railroad  1  includes a ballast  2  substrate, which is typically a hard particulate material such as, but not limited to, gravel. A plurality of substantially parallel, elongated ties  3  are disposed on the ballast. One or more pairs of rails  4  are coupled to the upper side of the ties  3  and extend generally perpendicularly to each tie  3 . As is known, the rails  4  are typically coupled to the ties  3  by clips or spikes (not shown). As is further known, a tie plate  5  ( FIG. 3 ) is typically disposed between the tie  3  and the rail  4 . The tie plate  5  is typically a metal plate that extends substantially from the forward side of the tie  3  to the rearward side of the tie  3 . While it is understood that ties  3  may support any number of rails, only two rails  4 , a first rail  4 A and a second rail  4 B, are shown ( FIG. 5 ). In this configuration both rails  4 A,  4 B have an “inner” side, i.e. between the rails  4 A,  4 B, and an “outer” side, i.e. not between the rails  4 A,  4 B. The convention of “inner” and “outer” sides is applicable to any pair of rails  4 , even if there is an adjacent pair of rails  4  on the tie. That is, a location may be on the “outer” side of one pair of rails  4  even if there is a second, adjacent pair of rails  4  and the location is between the first and second pairs of rails. 
     As shown in  FIG. 1 , a tamper system  10  includes a tamper vehicle  20  and a drone tamper  100 . The tamper vehicle  20  includes a vehicle body  22 , a propulsion device  24 , a control system  26 , at least one pair of tamper assemblies  28  structured to tamp a tie  3 , a tie locator  30  with an associated encoder wheel  32 , and an operator cabin  34 . The tamper vehicle body  22  includes a frame  40  and plurality of rail wheels  42 . The tamper vehicle rail wheels  42  are coupled to the tamper vehicle frame  40 . The tamper vehicle rail wheels  42  are further structured to travel over the rails  4 A,  4 B. The tamper vehicle propulsion device  24  is structured to propel the tamper vehicle  20  over the rails  4 A,  4 B. 
     The tamper vehicle encoder wheel  32  is fixed to the tamper vehicle body  22  and structured to roll over one rail  4 . The tamper vehicle encoder wheel  32  accurately measures the distance the tamper vehicle  20  moves and the speed of the tamper vehicle  20 . The tamper vehicle encoder wheel  32  has a known, and fixed, diameter and produces a signal, or known quantity of pulses for each revolution. Thus, by tracking and recording the number of pulses, the distance the tamper vehicle body  22  travels from a known location may be determined. This data is the tamper position data. The distance the tamper vehicle body  22  travels, i.e. distance data, is preferably tracked from a local point at the maintenance/installation site. Further, by comparing the distance traveled to a set period of time, the speed of the tamper vehicle body  22  is known. While the tamper vehicle body  22  is moving forward, the tamper vehicle encoder wheel  32  is turning in a clockwise motion, as shown in the figures. The tamper position data and tamper movement data are converted to an electronic signal and communicated to the tamper vehicle control system  26 . 
     The tie locator  30  is disposed at the forward end of the tamper vehicle  20  and may be disposed on an extension that extends in front of the tamper vehicle body  22 . Two tie locators  30  may be positioned on the tamper vehicle  20 , with one positioned over each rail  4 A and  4 B to allow the tie locators to detect if a tie is skewed. Preferably, the tamper vehicle tie locator  30  is at a fixed distance from the tamper vehicle body  22  and more specifically from the tamper vehicle workheads  28 . The tamper vehicle tie locator  30  may be any such known device and, typically, is a metal detector  31  structured to detect the metal tie plate  5  disposed between each rail  4 A,  4 B and each tie  3 . As the tie plate  5  typically extends substantially from the forward side of the tie  3  to the rearward side of the tie  3 , such a detector  31  will typically record a peak when the detector  31  is over the middle of the tie plate  5  and therefore the tie  3 . The tamper vehicle tie locator  30 , and/or the detector  31 , is structured to produce “tie configuration data” representing the initial detection of the tie plate  5 , the peak detection of the tie plate  5 , and the final detection of the tie plate  5 . The tie configuration data may also include information relating to the spacing between adjacent ties  3  and the tie plates  5  disposed thereon. For example, if a tie  3  is skewed, i.e. one tie plate  5  on the skewed tie  3  is closer to the next tie  3  in the forward direction, information representing the orientation of the skewed tie  3  is included in the tie configuration data. The tie configuration data is converted to an electronic signal and communicated to the tamper vehicle control system  26 . 
     As the distance between the tie locator  30  and the encoder wheel  32  is known, i.e. both are fixed to the tamper vehicle body  22  and the distance there between can be measured, the location of each tie  3 , as well as the skew of each tie  3 , if any, can be tracked by comparing the tie locator  30  data and the distance data. The data representing the location of each tie  3  is the “tie position data.” The tie position data may include the tie configuration data. That is, the tie position data may include data regarding the profile of each tie plate  5  as determined by the detector. The tie position data is maintained in the tamper vehicle control system  26 . 
     The tamper assemblies  28  of the tamper vehicle  20  are similar to the tamper assemblies  128  of the drone tamper  100 . The following is a description of a single tamper assembly  28 ,  128  which may be used on either, or both, the tamper vehicle  20  and/or the drone tamper  100 . Further, it is understood that a tamper assembly  28 ,  128  is typically disposed over each rail  4 A,  4 B, however, only a single tamper assembly  28 ,  128  is described below. 
     Each tamper assembly  28 ,  128  includes at least one pair of tamper assembly workheads  50 ,  60 . As shown in  FIG. 2 , each workhead  50 ,  60  includes a vibration device  52 ,  62  and a pair of elongated, vertically extending tools  54 ,  64 . The vertically extending, and more specifically, vertically descending tools  54 ,  64  are elongated shafts which may have a single prong (not shown) or multiple prongs  56 ,  66 . The distal ends  58 ,  68  of the tools  54 ,  64  are structured to engage and pass into the ballast  2 . The tool distal ends  58 ,  68  may be generally flat plates that extend generally laterally to the rails  4 . When coupled to an associated vehicle, tamper vehicle  20  or the drone tamper  100 , and in a substantially vertical orientation, the tools  54 ,  64  are spaced wider than a tie  3  width apart, but not so wide as to be able to engage, i.e. contact, two ties  3  at once. That is, the tools  54 ,  64  are spaced to engage the ballast  2  on either side of a worksite tie  3  without contacting an adjacent tie  3 . 
     The at least one pair of tamper assembly workheads  50 ,  60  are movably coupled to the associated vehicle, tamper vehicle  20  or the drone tamper  100 , and structured to move vertically. That is, the tamper assembly workheads  50 ,  60  are structured to move between a first, upper position, wherein the tools  54 ,  64  do not engage the ballast  2 , and a second, lower position, wherein the tools  54 ,  64  do engage the ballast  2 . Preferably, when the workheads  50 ,  60  are in the second, lower position, the tool distal ends  58 ,  68 , are below the bottom of the worksite tie  3 . 
     The at least one pair of tamper assembly workheads  50 ,  60  are also structured to move the tools  54 ,  64  together in a pincer-like motion. Typically, the tamper assembly  28 ,  128  includes a tamper assembly mount  29  to which the workheads  50 ,  60  are pivotally coupled. The pivot pin (not shown) for each workhead  50 ,  60  extends generally laterally relative to the rails  4 . In this configuration, the tools  54 ,  64 , and more specifically the tool distal ends  58 ,  68 , are structured to compact ballast  2  below a worksite tie  3 . To assist in the compacting of the ballast  2 , each extending tool  54 ,  64  is coupled at least somewhat rigidly to a vibration device  52 ,  62 . When the vibration device  52 ,  62  is actuated, the tool  54 ,  64  rapidly vibrates thereby enhancing the compacting action of the pincer-like motion. 
     While a tamper assembly  28  may function with only a single pair of workheads  50  and  60 , it is typical to have two pairs, that is four, workheads  50 ,  60 ,  70 ,  80  per tamper assembly  28 ,  128 . The second pair of workheads  70 ,  80  include the same components as described above and it is understood that like reference numbers apply. That is, for example, the second pair of workheads  70 ,  80  includes tools  74 ,  84 . It is noted, however, that the workheads on the same side of the rail, i.e. forward or rearward of the worksite tie and inboard or outboard of the rail may share a vibration device  52 ,  62  ( FIG. 1 ). 
     In this configuration, a workhead  50 ,  60 ,  70 ,  80  may be disposed above a worksite tie  3  with one tool  54 ,  64 ,  74 ,  84  on either side of the rail  4  at the worksite tie  3 . That is, a first workhead  60  engages the ballast  2  on the forward side of the tie  3  on both sides of the rail  4 . The opposing/associated second workhead  50  engages the ballast  2  on the rearward side of the tie  3  on both sides of the rail  4 . The third workhead  80  engages the ballast  2  on the forward side of the tie  3  on both sides of the rail  4 . The opposing/associated fourth workhead  70  engages the ballast  2  on the rearward side of the tie  3  on both sides of the rail  4 . 
     Each vehicle, the tamper vehicle  20 , or the drone tamper  100 , preferably, has at least two tamper assemblies  28  with one tamper assembly  28  disposed over each rail  4 A,  4 B. The tamper assemblies  28  may be identified as tamper vehicle first tamper assembly  28 A, tamper vehicle second tamper assembly  28 B. As shown, the tamper vehicle first tamper assembly  28 A includes workheads  50 ,  60  and the tamper vehicle second tamper assembly  28 B includes workheads  70 ,  80 . Further, and as discussed below, there is also a drone tamper first tamper assembly  128 A and a drone tamper second tamper assembly  128 B. 
     The tamper vehicle control system  26  includes one or more programmable logic circuits (not shown) and may be identified colloquially as a “computer.” The tamper vehicle control system  26  includes a communication system  27  (shown schematically) that is structured to communicate with the drone tamper communication system  127 , discussed below. The tamper vehicle control system  26  is in electronic communication, typically by a hardwire and/or a wireless system, with the tamper vehicle propulsion device  24 , the at least one pair of tamper assemblies  28 , the tie locator  30  and the encoder wheel  32 . That is, the control system  26  sends data, including commands, to and/or receive data from the tamper vehicle propulsion device  24 , the at least one pair of tamper assemblies  28 , the tie locator  30  and the encoder wheel  32 . 
     In addition to collecting and tracking distance data, movement data, and tie location data, the tamper vehicle control system  26  is structured to control the tamper vehicle propulsion device  24  and the actuation of the tamper vehicle first tamper assembly  28 A, tamper vehicle second tamper assembly  28 B. Preferably, this operation is generally automatic. That is, based on the tracking distance data, movement data, and tie location data, the tamper vehicle control system  26  may engage the tamper vehicle propulsion device  24  to move the tamper vehicle body  22  into a position so that the tamper vehicle first tamper assembly  28 A and tamper vehicle second tamper assembly  28 B are disposed over a worksite tie  3 . The tamper vehicle control system  26  may then actuate the tamper vehicle first tamper assembly  28 A and tamper vehicle second tamper assembly  28 B to perform a tamping cycle at the worksite tie  3 . A tamping cycle begins when at least one of the tamper vehicle first tamper assembly  28 A,  28 B is actuated and includes a down thrust of at least one pair of workheads  50  and  60  or  70  and  80  so that the associated tool  54 ,  64 ,  74 ,  84  penetrates the ballast  3 , the closing and/or pinching of the at least one pair of workheads  50 ,  60 ,  70 ,  80 , the actuation of the vibration device  52 ,  62 ,  72 ,  82  associated with the at least one pair of workheads  50 ,  60 ,  70 ,  80 , the return of the at least one pair of workheads  50 ,  60 ,  70 ,  80  to a generally vertical orientation, and the withdrawal, or uptake, of the at least one pair of workheads  50 ,  60 ,  70 ,  80  and associated tool  54 ,  64 ,  74 ,  84 , i.e. the uptake of the tamper vehicle first tamper assembly  28 A,  28 B. Following a tamping cycle, the tamper vehicle control system  26  actuates the propulsion device  24  so as to advance the tamper vehicle  20  until the at least one pair of workheads  50 ,  60 ,  70 ,  80  are positioned over a subsequent worksite tie  3 . 
     The operator cabin  34  is coupled to the tamper vehicle body  22  and includes a control panel (not shown) coupled to the tamper vehicle control system  26 . The operator cabin  34 , which may be generally open or enclosed, is structured to accommodate one or more human operators. The control panel is structured to communicate, e.g. via displays, gages, meters etc. the condition of the tamper vehicle  20  and the drone tamper  100 . 
     As shown in  FIGS. 3-6 , the drone tamper  100  includes a vehicle body  122 , a propulsion device  124 , a control system  126 , at least one pair of tamper assemblies  128  structured to tamp a tie  3 , and a tie locator  130  with an associated encoder wheel  132 . Preferably, the drone tamper vehicle body  122  is not structured to transport a human. The drone tamper body  122  includes a frame  140  and plurality of rail wheels  142 . The tamper vehicle rail wheels  142  are coupled to the drone tamper frame  140 . The drone tamper rail wheels  142  are further structured to travel over the rails  4 A,  4 B. The drone tamper propulsion device  124  is structured to propel the drone tamper  100  over the rails  4 A,  4 B. 
     The drone tamper encoder wheel  132  is fixed to the drone tamper body  122  and structured to roll over one rail  4  or may be mounted to the idler axle of the drone tamper  100 . The drone tamper encoder wheel  132  accurately measures the distance the drone tamper  100  moves and the speed of the drone tamper  100 . The drone tamper encoder wheel  132  has a known, and fixed, diameter and produces a known quantity of pulses or other signal for each revolution. Thus, by tracking and recording the number of pulses, the distance the drone tamper body  122  travels from a known location may be determined. This data is the drone position data. The distance the drone tamper body  122  travels, i.e. distance data, is preferably tracked from a local point at the maintenance/installation site. Further, by comparing the distance traveled to a set period of time, the speed of the drone tamper body  122  is known. While the drone tamper body  122  is moving forward, the drone tamper encoder wheel  132  is turning in a clockwise motion, as shown in the figures. The drone position data and drone movement data are converted to an electronic signal and communicated to the drone tamper control system  126 . 
     The drone tamper tie locator  130  is disposed at the forward end of the drone tamper  100  and may be disposed on an extension that extends in front of the drone tamper body  122 . Preferably, the drone tamper tie locator  130  is at a fixed distance from the drone tamper body  122  and more specifically from the drone tamper encoder wheel  132 . The drone tamper tie locator  130  may be any such known device and, typically, is a metal detector  131  as described above. The drone tamper tie locator  130  also records a peak when the drone tamper detector  131  is over the middle of the tie plate  5  and therefore the tie  3 . The drone tamper tie locator  130 , and/or the drone tamper detector  131 , is structured to produce “tie configuration data” representing the initial detection of the tie plate  5 , the peak detection of the tie plate  5 , and the final detection of the tie plate  5 . This data is converted to an electronic signal and communicated to the drone tamper control system  126 . 
     The drone tamper control system  126  includes a communication system  127  (shown schematically) that is in wireless communication with the tamper vehicle communication system  127 . That is, the drone tamper control system  126  and tamper vehicle control system  26  are structured to communicate with each other. The tamper vehicle control system  26  is structured to provide tie position data to the drone tamper control system  126 . The drone tamper control system  126  is structured to provide data, generally relating to the condition of the drone tamper  100 , e.g. drone position data, drone movement data, configuration of tamper assemblies  128 A,  128 B, etc., to the tamper vehicle control system  26 . 
     The drone tamper control system  126  is structured to determine the location of the drone tamper  100  by comparing tie position data (which includes tie configuration data) provided by the tamper vehicle control system  26 , hereinafter “tamper vehicle tie position data,” with the tie position data (which includes tie configuration data) collected by the drone tamper tie locator  130 , hereinafter “drone tamper tie position data.” That is, because the drone tamper tie locator  130  is substantially similar to the tamper vehicle tie locator  30 , the data collected by the tamper vehicle detector  31  and the drone tamper detector  131  should be substantially similar. The tamper vehicle control system  26  will identify a location for a tie  3  having a specific set of tie configuration data. The tamper vehicle control system  26  will also identify a position for that tie  3 . When the drone tamper detector  131  detects a tie  3  having a substantially similar set of tie configuration data, the drone tamper control system  126  can determine the location of the drone tamper  100  relative to that tie  3  and, therefore, the location of the drone tamper  100 . The drone tamper control system  126  may constantly compare drone tamper tie position data with tamper vehicle tie position data to determine the location of the drone tamper  100  and/or, after the drone tamper control system  126  initially determines its position, the drone tamper control system  126  may utilize the drone tamper movement data to determine the location of the drone tamper  100 . 
     In the embodiment shown, the drone tamper  100  may include a work deck  134  structured to allow a worker to perform maintenance. The work deck  134  is not intended to support a human while the drone tamper  100  is in use. However, in other embodiments, the work deck may be designed to support a human during operation or travel, thereby allowing maintenance to be conducted during use. 
     As noted above, the drone tamper  100  include tamper assemblies  128 A,  128 B that are substantially similar to the tamper vehicle tamper assemblies  28 A,  28 B. Accordingly, the details regarding the configuration and operation of the drone tamper tamper assemblies  128 A,  128 B will not be detailed and the above discussion is incorporated by reference. It is noted that the drone tamper tamper assemblies  128 A,  128 B have the substantially the same components as the tamper vehicle tamper first and second assemblies  28 A,  28 B. Accordingly, it is understood that a tamper assembly reference number that is increased by “100” refers to a component of the drone tamper tamper assemblies  128 A,  128 B which is substantially similar to a component on the tamper vehicle tamper assemblies  28 A,  28 B. For example, as shown in  FIG. 6 , the drone tamper first tamper assembly  128 A includes workheads  170 ,  180  and the drone tamper second tamper assembly  128 B includes workheads  150 ,  160 . These elements are substantially similar to the tamper vehicle tamper first and second assemblies workheads  50 ,  60 ,  70 ,  80 , respectively. 
     The tamper vehicle  20  and/or the drone tamper  100  tamper assemblies  28 A,  28 B,  128 A,  128 B may include at least one a longitudinal positioning device  190 . This aspect shall be discussed with reference to the drone tamper  100 , but it is understood that similar components may be added to the tamper vehicle tamper assemblies  28 A,  28 B described above. Further, as the drone tamper first and second tamper assemblies  128 A,  128 B are substantially similar, this aspect shall be described with reference to a single drone tamper tamper assembly, that is the drone tamper first tamper assembly  128 A. Again, it is understood that substantially similar components may be included in the drone tamper second tamper assembly  128 B and that such components share a similar reference number followed by the letter “B.” 
     The drone tamper first tamper assembly  128 A may include a first longitudinal positioning device  190 A ( FIG. 5 ). The first longitudinal positioning device  190 A is structured to move the drone tamper first tamper assembly  128 A longitudinally relative to the drone tamper body  122 . The first longitudinal positioning device  190 A is structured to move the drone tamper first tamper assembly  128 A while the drone tamper body  122  is moving over the rails  4 , as described below. The first longitudinal positioning device  190 A includes a pair of tamper assembly rails  192 A, at least one (two as shown) longitudinal piston(s)  194 A, and a control device  196 A. The first longitudinal positioning device tamper assembly rails  192 A are a pair of elongated beams having an upper bearing surface  193 A. The first longitudinal positioning device tamper assembly rails  192 A are structured to support the drone tamper first tamper assembly  128 A, i.e. at least one of drone tamper assembly workheads  170  or  180 , and to allow the drone tamper first tamper assembly  128 A to travel longitudinally on the drone tamper body  122 . 
     The drone tamper body  122  includes elongated, longitudinally extending openings  195 A,  195 B on either side of the first longitudinal positioning device tamper assembly rail  192 A. The longitudinal positioning device tamper assembly rails  192 A,  192 B are disposed on either side of the associated opening  195 A,  195 B. The drone tamper first tamper assembly workheads  170  and  180  extend through the associated opening  195 A. The drone tamper second tamper assembly workheads  150 ,  160  extend through the associated opening  195 B. The drone tamper first tamper assembly  128 A is structured to be movably disposed on the first longitudinal positioning device tamper assembly rail bearing surface  193 A. 
     The first longitudinal positioning device longitudinal piston  194 A includes an outer cylinder, and a rod coupled to an inner piston member with seals (not shown) disposed within the outer cylinder. As is known, when a fluid is introduced behind the piston member, the first longitudinal positioning device longitudinal piston  194 A expands; when the fluid is removed, the first longitudinal positioning device longitudinal piston  194 A contracts. The first longitudinal positioning device longitudinal piston  194 A has a first end  197 A and a second end  198 A. The first longitudinal positioning device longitudinal piston first end  197 A is coupled to the drone tamper body  122 . The first longitudinal positioning device longitudinal piston second end  198 A is coupled to the drone tamper first tamper assembly  128 A, i.e. at least one of drone tamper assembly  150 . As noted above, the first longitudinal positioning device longitudinal piston  194 A is structured to expand/contract, that is, move between a first, short configuration and a second, long configuration. 
     The first longitudinal positioning device control device  196 A is structured to control the configuration of the first longitudinal positioning device longitudinal piston  194 A. The first longitudinal positioning device control device  196 A includes sensors  199 A (shown schematically) such as, but not limited to, a string potentiometer, that is structured to indicate the configuration, i.e. position, of the first longitudinal positioning device longitudinal piston  194 A. This data is the piston configuration data. The piston configuration data is created as an electronic signal and provided to the first longitudinal positioning device control device  196 A. The piston configuration data is used to determine the relative position of the drone tamper first tamper assembly  128 A. That is, the piston configuration data is used to determine the longitudinal position of the drone tamper first tamper assembly  128 A on the drone tamper body  122 . As shown, the first longitudinal positioning device longitudinal piston first end  197 A is coupled to the drone tamper body  122  at a location forward of the drone tamper first tamper assembly  128 A. Accordingly, when the first longitudinal positioning device longitudinal piston  194 A is in the first, short configuration, the drone tamper first tamper assembly  128 A is at a forward position relative to the drone tamper body  122 . When the first longitudinal positioning device longitudinal piston  194 A is in the second, long configuration, the drone tamper first tamper assembly  128 A is at a rearward position relative to the drone tamper body  122 . It is noted that a single longitudinal positioning device control device  196  may be used to control both the first and second longitudinal positioning device longitudinal pistons  194 A,  194 B. 
     The first longitudinal positioning device control device  196 A is further structured to receive tie position data from the drone tamper control system  126 . The first longitudinal positioning device control device  196 A is also structured to receive drone position data and drone movement data from the drone tamper control system  126 . The first longitudinal positioning device control device  196 A is structured to compare the tie position data, the drone position data, drone movement data and the piston configuration data, so as to determine the position of the drone tamper first tamper assembly  128 A relative to a worksite tie  3 . It is noted that because drone movement data is included, the first longitudinal positioning device control device  196 A is structured to move the drone tamper first tamper assembly  128 A while the drone tamper body  122  is in motion. That is, the first longitudinal positioning device control device  196 A is structured to maintain the drone tamper first tamper assembly  128 A in a substantially stationary location, e.g. above a worksite tie  3 , as the drone tamper body  122  is in motion, which is typically a forward motion. 
     Thus, at the beginning of a tamping cycle, the first longitudinal positioning device longitudinal piston  194 A is in the first, short configuration and the drone tamper first tamper assembly  128 A is at a forward position relative to the drone tamper body  122 . The at least one drone tamper tamper assembly  128 A,  128 B is then actuated and proceeds through the cycle described above regarding the tamper vehicle first and second tamper assemblies  28 A,  28 B. While the at least one drone tamper tamper assembly  128 A,  128 B is being actuated, the drone tamper body  122  is in motion, preferably a forward motion. During the actuation of the at least one drone tamper tamper assembly  128 A,  128 B, the longitudinal positioning device control device  196  compares the tie location data, the drone position data, drone movement data and the piston configuration data so as to control the expansion of the associated longitudinal positioning device longitudinal piston  194 A,  194 B toward the second, long configuration, thereby maintaining the at least one drone tamper tamper assembly  128 A,  128 B in a substantially stationary location, e.g. above a worksite tie  3 . That is, generally, the longitudinal positioning device control device  196  causes the associated longitudinal positioning device longitudinal piston  194 A,  194 B to expand at a rate whereby the at least one drone tamper tamper assembly  128 A,  128 B moves rearwardly over the associated longitudinal positioning device tamper assembly rails  192 A,  192 B at substantially the same as the speed as the drone tamper body  122  is moving forward over the rails  4 . Thus, the at least one drone tamper tamper assembly  128 A,  128 B remains in a substantially stationary location, e.g. above a worksite tie  3 , during a tamping cycle. Once the tamping cycle is complete, or at least once the associated tools  154 ,  164 ,  174 ,  184  are removed from the ballast  2 , the longitudinal positioning device control device  196  rapidly returns the associated longitudinal positioning device longitudinal piston  194 A,  194 B to the first, short configuration so that the at least one drone tamper tamper assembly  128 A,  128 B may begin the next tamping cycle. 
     While the above-described embodiment refers to a tamping vehicle  20  and a drone tamper  100 , the invention is directed to any type of track maintenance equipment which has a lead vehicle and one or more drones which follow. As previously discussed, the encoder wheel  32  is fixed to the lead vehicle body  22  and structured to roll over one rail  4 . The lead vehicle encoder wheel  32  accurately measures the distance the lead vehicle  20  moves and the speed of the lead vehicle  20 . The lead vehicle encoder wheel  32  has a known, and fixed, diameter and produces a signal, or known quantity of pulses, for each revolution. Thus, by tracking and recording the number of pulses, the distance the lead vehicle body  22  travels from a known location may be determined. This data is the “lead position data.” The distance the lead vehicle body  22  travels, i.e. distance data, is preferably tracked from a local point at the maintenance/installation site. Further, by comparing the distance traveled to a set period of time, the speed of the lead vehicle body  22  is known. While the lead vehicle body  22  is moving forward, the lead vehicle encoder wheel  32  is turning in a clockwise motion, as shown in the figures. The speed of the lead vehicle body  22 , or “lead movement data,” is determined either constantly (analog) or, more typically, many times each second (digital). The lead position data and lead movement data are converted to an electronic signal and communicated to the lead vehicle control system  26 . 
     The tie locator  30  is disposed at the forward end of the lead vehicle  20  and may be disposed on an extension that extends in front of the lead vehicle body  22 . Two tie locators  30  may be positioned on the lead vehicle  20 , with one positioned over each rail to allow the tie locators to detect if a tie is skewed. Preferably, the lead vehicle tie locator  30  is at a fixed distance from the lead vehicle body  22  and more specifically from the lead vehicle workhead  28 . The lead vehicle tie locator  30  may be any such known device and, typically, is a metal detector  31  structured to detect the metal tie plate  5  disposed between each rail  4 A,  4 B and each tie  3 . As the tie plate  5  typically extends substantially from the forward side of the tie  3  to the rearward side of the tie  3 , such a detector  31  will typically record a peak when the detector  31  is over the middle of the tie plate  5  and therefore the tie  3 . The lead vehicle tie locator  30 , and/or the detector  31 , is structured to produce “tie configuration data” representing the initial detection of the tie plate  5 , the peak detection of the tie plate  5 , and the final detection of the tie plate  5 . The tie configuration data may also include information relating to the spacing between adjacent ties  3  and the tie plates  5  disposed thereon. For example, if a tie  3  is skewed, i.e. one tie plate  5  on the skewed tie  3  is closer to the next tie  3  in the forward direction, information representing the orientation of the skewed tie  3  is included in the tie configuration data. The tie configuration data is converted to an electronic signal and communicated to the lead vehicle control system  26 . 
     As the distance between the tie locator  30  and the encoder wheel  32  is known, i.e. both are fixed to the lead vehicle body  22  and the distance therebetween can be measured, the location of each tie  3 , as well as the skew of each tie  3 , if any, can be tracked by comparing the tie locator  30  data and the distance data. The data representing the location of each tie  3  is the “tie position data.” The tie position data may include the tie configuration data. That is, the tie position data may include data regarding the profile of each tie plate  5  as determined by the detector. The tie position data is maintained in the lead vehicle control system  26 . 
     The lead vehicle control system  26  includes one or more programmable logic circuits (not shown) and may be identified colloquially as a “computer.” The lead vehicle control system  26  includes a communication system  27  (shown schematically) that is structured to communicate with the drone communication system  127 , discussed below. The lead vehicle control system  26  is in electronic communication, typically by a hardwire and/or a wireless system, with the lead vehicle propulsion device  24 , the workhead(s) (which may include, but not be limited to anchor squeezers, spike drivers, track stabilizers, crib booms, tie extractors, single and double brooms, and tampers), the tie locator  30  and the encoder wheel  32 . That is, the control system  26  sends data, including commands, to and/or receives data from the lead vehicle propulsion device  24 , the workhead(s), the tie locator  30  and the encoder wheel  32 . 
     In addition to collecting and tracking distance data, movement data, and tie location data, the lead vehicle control system  26  is structured to control the lead vehicle propulsion device  24  and the actuation of the lead vehicle workhead(s). Preferably, this operation is generally automatic. That is, based on the tracking distance data, movement data, and tie location data, the lead vehicle control system  26  may engage the lead vehicle propulsion device  24  to move the lead vehicle body  22  into a position so that the workhead(s) is disposed over a worksite tie  3 . The lead vehicle control system  26  may then actuate the lead vehicle workhead(s) to perform an appropriate cycle at the worksite tie  3 . 
     The drone encoder wheel  132  is fixed to the drone body  122  and structured to roll over one rail  4 . The drone encoder wheel  132  accurately measures the distance the drone vehicle  100  moves and the speed of the drone  100 . The drone encoder wheel  132  has a known, and fixed, diameter and produces a known quantity of pulses or other signal for each revolution. Thus, by tracking and recording the number of pulses, the distance the drone body  122  travels from a known location may be determined. This data is the drone position data. The distance the drone body  122  travels, i.e. distance data, is preferably tracked from a local point at the maintenance/installation site. Further, by comparing the distance traveled to a set period of time, the speed of the drone body  122  is known. While the drone body  122  is moving forward, the drone encoder wheel  132  is turning in a clockwise motion, as shown in the figures. The speed of drone body  122 , or “drone movement data,” is determined either constantly (analog) or, more typically, many times each second (digital). The drone position data and drone movement data are converted to an electronic signal and communicated to the drone control system  126 . 
     The drone tie locator  130  is disposed at the forward end of the drone  100  and may be disposed on an extension that extends in front of the drone body  122 . Preferably, the drone tie locator  130  is at a fixed distance from the drone body  122  and more specifically from the drone encoder wheel  132 . The drone tie locator  130  may be any such known device and, typically, is a metal detector  131  as described above. The drone tie locator  130  also records a peak when the drone detector  131  is over the middle of the tie plate  5  and therefore the tie  3 . The drone tie locator  130 , and/or the drone detector  131 , is structured to produce “tie configuration data” representing the initial detection of the tie plate  5 , the peak detection of the tie plate  5 , and the final detection of the tie plate  5 . This data is converted to an electronic signal and communicated to the drone tamper control system  126 . 
     The drone control system  126  includes a communication system  127  (shown schematically) that is in wireless communication with the communication system  127 . That is, the drone control system  126  and lead vehicle control system  26  are structured to communicate with each other. The lead vehicle control system  26  is structured to provide tie position data to the drone control system  126 . The drone control system  126  is structured to provide data, generally relating to the condition of the drone  100 , e.g. drone position data, drone movement data, configuration of the drone workheads, etc., to the lead vehicle control system  26 . The drone control system  126  is in electronic communication, typically by a hardwire and/or a wireless system, with the drone propulsion device  124 , the workheads (which may include, but not be limited to, anchor squeezers, spike drivers, track stabilizers, crib booms, tie extractors, single and double brooms, and tampers), the tie locator  130  and the encoder wheel  132 . That is, the control system  126  sends data, including commands, to and/or receives data from the drone propulsion device  124 , the workheads, the tie locator  130  and the encoder wheel  132 . 
     The drone control system  126  is structured to determine the location of the drone  100  by comparing tie position data (which includes tie configuration data) provided by the lead vehicle control system  26 , hereinafter “lead vehicle tie position data,” with the tie position data (which includes tie configuration data) collected by the drone tie locator  130 , hereinafter “drone tie position data.” That is, because the drone tie locator  130  is substantially similar to the lead vehicle tie locator  30 , the data collected by the lead vehicle detector  31  and the drone detector  131  should be substantially similar. The lead vehicle control system  26  will identify a location for a tie  3  having a specific set of tie configuration data. The lead vehicle control system  26  will also identify a position for that tie  3 . When the drone detector  131  detects a tie  3  having a substantially similar set of tie configuration data, the drone control system  126  can determine the location of the drone  100  relative to that tie  3  and, therefore, the location of the drone  100 . The drone control system  126  may constantly compare drone tie position data with lead vehicle tie position data to determine the location of the drone  100  and/or, after the drone control system  126  initially determines its position, the drone control system  126  may utilize the drone movement data to determine the location of the drone  100 . 
     In addition to collecting and tracking distance data, movement data, and tie location data, the drone control system  126  is structured to control the drone propulsion device  124  and the actuation of the drone workhead(s). Preferably, this operation is generally automatic. That is, based on the tracking distance data, movement data, and tie location data, the drone control system  126  may engage the drone propulsion device  124  to move the drone body  122  into a position so that the workhead(s) is disposed over a worksite tie  3 . The drone control system  126  may then actuate the drone workhead(s) to perform an appropriate cycle at the worksite tie  3 . 
     The communication between the control system  26  of the lead vehicle  20  and the control system  126  of the drone  100  is used to instruct the drone  100  to skip ties  3  on which the lead vehicle  20  has previously completed the work (e.g. appropriate squeeze pressure was reach for a tamper assembly of the lead vehicle) and to skip sections of the track which may not be required to be worked on, such as parts of a switch, crossings, etc. In addition, the communication is also used for and during travel of the lead vehicle and the drone(s). It is used to synchronize the encoder wheels at the arrival to the work site and during work cycles to make adjustments to the changing distances resulting from right hand or left hand curves. It is used for programming limits between the lead vehicle and the drone(s), such as, but not limited to: how close the drone can get to the lead vehicle before it should stop working and how far the lead vehicle travels before the drone may resume work. The drone control system communicates the drone position data to the lead vehicle control system. The lead vehicle control system compares the drone position data to the lead vehicle position data and controls the movement of the drone relative to the lead vehicle. 
     While the above-described embodiment refers to any type of track maintenance equipment which has a lead vehicle and one or more drones which follow, another embodiment is directed to a drone in combination with a gang of other equipment. In this embodiment, no lead vehicle is required and the tie locator is disposed at the forward end of the drone tamper. 
     The drone encoder wheel  132  is fixed to the drone body  122  and structured to roll over one rail  4 . The drone encoder wheel  132  accurately measures the distance the drone vehicle  100  moves and the speed of the drone  100 . The drone encoder wheel  132  has a known, and fixed, diameter and produces a known quantity of pulses or other signal for each revolution. Thus, by tracking and recording the number of pulses, the distance the drone body  122  travels from a known location may be determined. This data is the drone position data. The distance the drone body  122  travels, i.e. distance data, is preferably tracked from a local point at the maintenance/installation site. Further, by comparing the distance traveled to a set period of time, the speed of the drone body  122  is known. While the drone body  122  is moving forward, the drone encoder wheel  132  is turning in a clockwise motion, as shown in the figures. The speed of drone body  122 , or “drone movement data,” is determined either constantly (analog) or, more typically, many times each second (digital). The drone position data and drone movement data are converted to an electronic signal and communicated to the drone control system  126 . 
     The drone tie locator  130  is disposed at the forward end of the drone  100  and may be disposed on an extension that extends in front of the drone body  122 . Preferably, the drone tie locator  130  is at a fixed distance from the drone body  122  and more specifically from the drone encoder wheel  132 . The drone tie locator  130  may be any such known device and, typically, is a metal detector  131  as described above. The drone tie locator  130  also records a peak when the drone detector  131  is over the middle of the tie plate  5  and therefore the tie  3 . The drone tie locator  130 , and/or the drone detector  131 , is structured to produce “tie configuration data” representing the initial detection of the tie plate  5 , the peak detection of the tie plate  5 , and the final detection of the tie plate  5 . This data is converted to an electronic signal and communicated to the drone tamper control system  126 . 
     The drone tamper control system  126  includes one or more programmable logic circuits (not shown) and may be identified colloquially as a “computer.” The drone tamper control system  126  is in electronic communication, typically by a hardwire and/or a wireless system, with the drone tamper propulsion device  124 , the workhead(s) (which may include, but not be limited to anchor squeezers, spike drivers, track stabilizers, crib booms, tie extractors, single and double brooms, and tampers), the tie locator  30  and the drone tamper encoder wheel  132 . That is, the control system  126  sends data, including commands, to and/or receives data from the drone tamper propulsion device  124 , the workhead(s), the tie locator  30  and the drone tamper encoder wheel  132 . 
     In addition to collecting and tracking distance data, movement data, and tie location data, the drone tamper control system  126  is structured to control the drone tamper propulsion device  124  and the actuation of the drone tamper workhead(s). Preferably, this operation is generally automatic. That is, based on the tracking distance data, movement data, and tie location data, the drone tamper control system  126  may engage the drone tamper propulsion device  124  to move the drone tamper vehicle body  122  into a position so that the workhead(s) is disposed over a worksite tie  3 . The drone tamper control system  126  may then actuate the drone tamper vehicle workhead(s) to perform an appropriate cycle at the worksite tie  3 . 
     The control system  126  of the drone  100  is may be programmed to instruct the drone  100  to work on any or all of the ties  3 , e.g. to skip ties  3  on which the lead vehicle  20  has previously completed the work (e.g. appropriate squeeze pressure was reach for a tamper assembly of the lead vehicle) or to skip sections of the track which may not be required to be worked on, such as parts of a switch, crossings, etc. In addition, the communication is also used for and during travel of the drone(s). It is used to synchronize the encoder wheels at the arrival to the work site and during work cycles to make adjustments to the changing distances resulting from right hand or left hand curves. 
     The use of the lead vehicle and/or drone(s) has many advantages. As the control systems are automated, the costs associated with operators are greatly reduced. The use of the lead vehicle and/or drone(s) allows the production rate of the overall operation to be increased over the traditional dual or triple headed machines. The use of the lead vehicle and/or drone(s) also allows for more efficient and better quality work to be performed on wood or other ties which are closely spaced or skewed. 
     With the lead vehicle and drone(s), the vehicles are independent and the design of the vehicles is much simpler than a dual or triple workhead vehicle, thereby reducing the cost of manufacture and maintenance. The separation of the workheads between the lead vehicle and the drone vehicle allows for other operations to be conducted between the workheads as the vehicles operate. As an example, if the lead vehicle is unable to complete its operation because a tie is not properly attached to the rail, the tie may be identified so that workers may manipulate the respective tie prior to the workheads of the drone being positioned over the respective tie, thereby allowing the drone workheads to complete the operation. In addition, as the working components of the lead vehicle and the drone(s) can be identical, the number of parts required in inventory is reduced and the service time is decreased. 
     While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the claims appended and any and all equivalents thereof.