Lynx motion track system

Darrenwj · December 23, 2020, 9:02pm

I am looking to change from tires to tracks on an existing robot I built for crawl space inspections. I keep catching small wires in the tires and they get wrapped around the axles so I’m hoping tracks will limit that. My question is are the sprockets and tracks durable enough for this use. The robot weighs about 13 lb total. I was going to use 3-in tracks with double sprockets. Any thoughts you might have would be a help. Thanks.

scharette · December 23, 2020, 9:28pm

Hi @Darrenwj,

Welcome to the RobotShop community!

Neat stuff! What are you using for vision/sensors, control, etc.?

Do note that doing such a change will (most likely) increase the amount of torque required per motor, especially for turning. Since you mention the robot being about 13 lbs, that could be significant and may require an upgrade to the motors (i.e.: either higher gear ratio or more powerful motors).

You may want to have a look at this.

@cbenson @dialfonzo Can probably offer more help on the mechanical side of things!

Darrenwj · December 23, 2020, 10:18pm

Thanks for the help! Here is a link to see the robot

Its powered by 4 12V 180RPM Geared High Torque Motors (Max. Torque 90Kg.cm). I have 2 ESP, one to control each side. I would change that to only 2 motors with the tracks. I think they should be able to handle the tracks. I am using a Hawkeye 4K split cam for live viewing and recorded footage. I have looked at the Lynxmotion gears and sprockets and was about to purchase but I just wanted to verify that they would be durable enough for this application.

scharette · December 23, 2020, 11:02pm

Haha! You prob. have an order of magnitude more power than you need. Even with a rule of thumb of ~22.5-30 kg-cm available for continuous use, you most likely have plenty of power available!

Darrenwj · December 28, 2020, 9:02pm

Any feedback on the quality of the lynxmotion tracks and sprockets? Has anyone used them and what are your thoughts? I want to use them on a crawlspace robot and need to know if these will be appropriate and durable. I was planning on using the 7" sprockets with 3" wide tracks. Thanks.

cbenson · December 29, 2020, 2:07pm

@Darrenwj The tracks themselves are very durable and you should not have any problem with the weight you mentioned. The sprockets too are very durable and a dual setup using MTS sprockets should be fine:

There are not many modular tracks available for a robot that size. The issue is that the teeth are not very high, so in larger robots, you will need to ensure there’s good contact around the sprocket with minimal slack, or else (as is often the case with tank tracks), the track might come off. Be sure to get the track length one track link longer than being “too tight”. You indicate it’s a 4WD robot, so the track should wrap around half of each sprocket, which is very good.

Care to share a photo or two of the current robot and provide some dimensions?

Darrenwj · December 29, 2020, 11:31pm

The chassis is 9 in wide and 11 in Long and 3 and 3/4 in tall. there’s 6 in tires on it and the whole thing with the camera is 10 in tall. so I like to tinker but this was my first robot project so it’s a little rough. It’s been a lot of fun building it though. I’m about to switch the camera to a firefly 8se. I can buy a remote so I can start and stop video and pictures from the radio. also going to build the servo mount a little different on top to make a little lower profile. I just picked up a 3D printer so I should be able to build something myself. Do you think I should leave all four motors in with the tracks or should I just use two?

cbenson · December 30, 2020, 1:16pm

Nice! RobotShop carried some rubber tracks, but they were eventually discontinued due to lack of demand. The last pair seems too small for your needs unless you were to make the sprockets quite small.

So, given the size of your creation, the main consideration is that the teeth on the MTS sprocket are not too tall, so having two side by side will help, but you’ll need to keep the track tensioned.

In regards to your question of using one or two motors per side, the approach would be to replace one with a free spinning shaft, supported by bearings? Keep in mind that turning a track vehicle takes quite a bit more power than wheels, so you might want to keep all four motors.

Darrenwj · December 30, 2020, 4:29pm

Having never built anything like this I’m concerned with using two motors on each side and the timing of those motors being in sync so that one isn’t pulling faster than the other. Of course I could simply slide this sprockets on there and try and see what happens first. That’s why I was going to reduce it to one motor on each side. So you think I should add an extra smaller sprocket on each side to use as a tensioner? I could add a 9-tooth sprocket in the center of either side to put tension on the top of the track. What do you think? I would make that one adjustable up and down to add or reduced tension.

cbenson · December 30, 2020, 4:50pm

Having never built anything like this I’m concerned with using two motors on each side and the timing of those motors being in sync so that one isn’t pulling faster than the other.

Understood this was the concern, and it will happen a bit, but the track should be able to take it.

So you think I should add an extra smaller sprocket on each side to use as a tensioner?

Before doing so, see how tight you can get it to one track segment close: at some point during assembly you’ll see it will be too tight to bring the ends of the track together, and while adding an additional segment the track might make it seem a bit loose. At that point, try it, and if it doesn’t work and the track comes off, then look into a tensioning system (like you said, one pushing against the track somewhere should do it).

Normally during the design process, you would factor in the track length so no tensioner is needed. For example, when creating the Lynxmotion MTS based on the A4WD1, the distance between motors was ever so slightly changed so that the tracks would not need a tensioning system:

Darrenwj · January 10, 2021, 9:32pm

I went ahead and ordered the sprockets and tracks and I’m pretty happy with the results. There’s a little bit of slack in the track but I’ve run it for about an hour over logs and up hills and through debris and I have yet to have a track come off.