427 The last issue worth mention ing, discovered during trial runs of the Hammering Mechanism after its  integration,  was its sensitivity to improper  twisting of  the Wire H elix with respect to the Payload  Compartment and  Outer Casing. The Wire H elix, which is  a handcrafted component, is prone to be not fully  repeatable and each mechanism required individual adjustment of the twisting angle inside the Outer  Casing . The only way to do i t is to properly tension it by twisting its fixation points  - one with respect to the  other . The direction of twisting is of  a high importance and i t cannot be too tight  since it would interfere with  Spring Support and Brake S pring and also not too wide, since it would start sliding on the Outer C asing or  even block the movement of Suppressor Mass ( while expanding too much while being compressed  during  hammering) . The unpredicted influence of that tensioning was encountered during trial runs – Wire Helix  when tensioned against its coil direction (in the direction that causes its  diameter  expanding) creates a  twisting torque on the Suppressor Mass as well. This is not noticeable until the actual movement of masses  begins and Suppressor Mass can undesirably slightly twist back, resulting in a situation where the forkshaped features of the Tongue Ass embly partially collide with the accelerating Hammer Assembly (namely  Hammer Lock Pins) . This was called a bottle- neck effect since Hammer Lock Pins for a very short time are  pressed on one side by an edge of the Hammer Housing slot and corner of a fork -shaped feature in the  Tongue Assembly. This cannot stop the Hammer, but can decelerate it and result in damped hammering  action. The actual event sequence is shown in Figure 18 a. The effect can be easily omitted when the  Suppressor Mass will always be pulled by the Wire Helix in the direction indicated in Figure 18 b. 

a)         b)   Figure 18. a) Sequence of Hammer Lock Pin movement including bottle -neck effect; b) Rear part  of Suppressor Mass and  Wire Helix. Arrow indicates in which direction S M should be properly  pulled by Wire Helix to omit bottle -neck effect      Conclusions    The article presented the actual summary of main technological features of the Hammering Mechanism for   the HP3 mole penetrator. Particularly , principle and justification for drive spring s location was discussed,  which should always provide stabilized pulling force on the Hammer. DC Motor operation characteristics were improved by Cam’s profile optimization and confirmed with actual tests and current records. Also the principle for Cam prof ile design and optimization were provided with 30 ° initial slope inclination requirement.  Significant attention was paid to the lubrication process, which was particularly important for the  simplification of the design and increase of its reliability. Uncommon coatings were provided like sputtered MoS 2 on Tungsten alloy or on plasma nitrided Titanium a lloy, supported by results of tribological tests.  Some wear of MoS 2 on Hammer Lock Pins  was experienced and additional Braycote  601EF lubrication  was provided  to improve the wear resistance and durability of the coatings. Beside s lubrication, the bearing  description was discussed  including the especially interesting design of a very small Roller ( Ø9.2x14.9 mm)  with total of 34 rotating parts that can take over axial and radial loads. Last but not least , the novelty of the  design was the Launch Lock system that  allows for multiple locking and unlocking of the mechanism without  necessity of penetrator’s disassembly.     Problematic areas of the design were a dditionally highlighted. Tungsten alloy selection and its durab ility for  high impact application was provided. E ncountered problem with cracking of the material were indicated,  which was solved by particularly intensive inspection process on each phase of parts development. Also