Talk to me about gears and other mechanical stuff - Page 1
Forum section: electronics / general

author: Red Squirrel
author_rank: Super Contributor
timestamp: August 03, 2016, 03:35:25 am
content: If I want to build something that uses gears, chains etc... what is some good info to know, what is a good place to buy stuff like this? Are there standards on sizes and such, how does it work?Just toying with this at the moment, but I was thinking it would be neat to build a heavy duty telephoto mount system that uses gears and stepper motors (or just manual crank to keep it simple) to control it. That way you can dial in to a part of the sky and use a remote or buttons or something to slowly move to accurately get a shot, instead of manually dealing with a regular tripod and bouncing all over the place. Kinda like a satellite dish. Could get fancy at some point and have it track objects in the sky as well. Like try to catch the ISS or other moving things in the sky, then have it lock in, then you do a long exposure or for something like a plane, even a few single shots (this would be set ahead of time on the camera and manually controlled). Could make for a rather interesting project. I just know absolutely nothing about gears, as far as where to look, what to look for, etc. I mean, I understand how they work, just not how the industry works as far as standards and stuff. I imagine there are some. Kinda like how there are standards for screw sizes etc.Not really electronics related, but figured you guys may know about this, especially those of you into robotics. (something else I want to play around with at some point too)

author: Rerouter
author_rank: Super Contributor
timestamp: August 03, 2016, 04:19:39 am
content: From the sounds of it, you need it to be very stable and precise,To this end, i would say a chain is out of the picture, it would either be direct gears or more likely a worm gear approach, to sufficiently reduce the turning rate vs the input rotational rate,Now with steppers you will need to keep feeding them a holding current or you will loose some of your precision,Now tracking very fast objects like the ISS, that is hard, if you just want to be in the right part of the sky, not so much,As for where to get them built, or buy them, personally a few times i've made moulds out of lego gears and poured them in steel, but there are likley far better approaches out there,

author: DTJ
author_rank: Super Contributor
timestamp: August 03, 2016, 04:30:42 am
content: Take a look at Sterling Instruments / Stock Drive Products website - lots of tech info. They used to print a great handbook on mechanical parts and give it away, I think this has stopped though.http://www.sdp-si.com/http://www.sdp-si.com/resources/elements-of-metric-gear-technology/Spend some time looking at online catalogs:http://www.minibearings.com/Check out robotdigg, they have some very inexpensive mechanical parts but no tech info.

author: Galenbo
author_rank: Super Contributor
timestamp: August 03, 2016, 12:07:28 pm
content: Quote from: Red Squirrel on August 03, 2016, 03:35:25 amDefine rpm, precision, couple,... minimum, nominal, maximal values.Like in: "I want to build something that uses capacitors, transistors and resistances."Quote from: Red Squirrel on August 03, 2016, 03:35:25 amthere are indeed standards for miniature gears from a watch, and for 20-tonne gears for megawatt hydro plants.Like in: there are standards for MHZ antennas, and for KW invertors.

author: Red Squirrel
author_rank: Super Contributor
timestamp: August 04, 2016, 01:01:30 am
content: Quote from: Rerouter on August 03, 2016, 04:19:39 amYeah I'm thinking something that would have a rather large gear, and then a small worm drive connected directly to a stepper. That would do one axis, then have a similar setup for the other axis. Of course you'd want to setup some kind of movement limiter so the wire of the second axis does not tangle. Never used steppers before, do they just work on pwm? Faster the pulse, faster they go? Ex: each pulse makes it step? Or do they work differently?

author: mathsquid
author_rank: Frequent Contributor
timestamp: August 04, 2016, 01:55:29 am
content: I've seen a number of projects where people build a worm gear telescope mount using a 3/8" or 12mm screw as the worm, and making the worm wheel by using a tap as an inexpensive hobber. Here's one example:http://astronomyasylum.com/gears.html. Googling for "telescope tap hobbing" (without the quotes) will turn up more info.

author: Red Squirrel
author_rank: Super Contributor
timestamp: August 04, 2016, 03:50:18 am
content: I was thinking of some kind of DIY solution too. Maybe even wooden wheels with some kind of rubber on them for grip. This would not be precise without any kind of video feed back to tell it to go more a certain way etc, but would work fine for something manually operated to simply dial in to a spot on the sky... which honestly is probably my more realistic solution for the first version, can always go all out later and find a way to process live HDMI output from the camera to determine how to move. Ex: follow something in the sky. Essentially it would compare the last image with current live view, and determine how much to move until a certain target aligns with last pic. This would be done at say, 1 sec intervals. Or even more often.Another option I'm thinking is just buy random gear sets off ebay, then build the design around that. If I type "gears" or similar search terms I get all sorts of stuff. Not sure what to do for shaft and stuff though. I don't have any tools to do any kind of machining. Guess I could improvise as I go.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: August 04, 2016, 05:26:13 am
content: Quote from: Red Squirrel on August 04, 2016, 03:50:18 amIf you are familiar with how the tuning capacitor and knob were connected on old radios (basically pulleys and a tensioned string as a belt) you might find something like that more practical as a starting point. You can put together a working system without precision machining. By using non-stretching strings/belts you can avoid backlash type problems and get good repeatable results. You first decision should be how you want to measure position and achieve control. One approach is open loop. Use a stepper motor and count steps. This can work if you can establish the starting point with a limit switch or other device. The other approach is to use some type of encoder- a pot, an optical encoder or something else. Both approaches have pluses and minuses. What you understand and feel comfortable with has a lot of weight, but needs to be tempered by the performance you need/desire to have.Gear systems require precision mechanical fabrication and assembly that is not easy to do outside of a good machine shop, particularly if you want low backlash and low friction at the same time.

author: DTJ
author_rank: Super Contributor
timestamp: August 04, 2016, 10:53:05 am
content: Quote from: CatalinaWOW on August 04, 2016, 05:26:13 amStainless steel multistrand fishing trace is useful for that sort of thing. Cheap & easy to get hold of as well.

author: denelec
author_rank: Regular Contributor
timestamp: August 04, 2016, 11:28:58 pm
content: This Canadian company sells robots and robot parts (gears, motors, sensors, servos, electronics, etc...).http://www.robotshop.com/ca/

author: Red Squirrel
author_rank: Super Contributor
timestamp: August 04, 2016, 11:51:08 pm
content: Oh wow totally forgot about that site, I remember finding it once and going through it just to look at all the interesting stuff. I do want to play around with robotics too at some point. Going to brainstorm some ideas and see if this is a project I want to take on. Probably more a long term thing, my garage time is very short lived as it's not conditioned space. I need to change that some day.

author: TerraHertz
author_rank: Super Contributor
timestamp: August 06, 2016, 04:49:49 am
content: http://www.smallparts.com.au/I've only bought from these guys once, but they have an AMAZING range of stuff. They're in QLD, fast online mailorder.Some machinist forums:http://tomstechniques.com/links/Great lists of fabrication linkshttp://www.chaski.org/homemachinistForum, enthusiasts of all skill levels and disciplines of the metalworking hobby.http://www.machinistblog.com(and forum)http://www.homemodelenginemachinist.comhttp://www.practicalmachinist.comhttp://bbs.homeshopmachinist.nethttp://madmodder.nethttp://www.hobby-machinist.com/I'm in kind of the same position - accumulating bits for a 'kind of' 3D printer construction project. Odd in that it needs to be rather big, and also allow for other types of working head. I'd decided the primary axis (1st one, moving the most mass) will use sprocket chain for long travel and allowing drive along 4 edges for rigidity.OK so I needed a lot of sprocket chain. Bicycle chain type should be strong enough. Promptly came across someone throwing out a pile of scrapped garage door openers, that use looooong sprocket chains. Such a funny coincidence, as I've never seen so much sprocket chain in one place before. Now I definitely have more than enough chain (pic).Edit: Oh, and search on Aliexpress and other Chinese sites for terms related to 3D printers. For example:Steel Round BarCNC Supported Shaftcnc linear shaftcnc lead screwcnc rollerFlexible Shaft Couplingcnc skating blockcnc Linear Ball Bearing Blocklinear rail guidelinear bearing blockconcave bearing

author: jh15
author_rank: Frequent Contributor
timestamp: August 06, 2016, 04:56:47 am
content: Just look for a used goto telescope like a meade lx200. many people bought one and it gets as much use as an exercise machine. Besides being a good scope, everyone mounts cameras to them.That's the easy way.If you are interested in gears and chains, I wish the best for you. I learned so much from Erector Set brand in the 60's and the Boston Museum of Science.