I’m in the process of building a 70-120 lb robot. It’ll have a footprint of 1’x2’, probably 70 some pounds without any payload and a theoretical top speed of 31 mph, assuming I use the bigger 3.75" sprocket as the drive wheel. I’d just like to know the ratings on the treads and sprockets, especially tensile strength, weight and speed. The robot will (theoretically) be able to produce up to 600 lbf of force on the ground at peak output but realistically around 350 lbf when you account for losses in the gears and run the motors at a safer current.
If you’re curious as to what it does, it’s just a chassis based off of a South Korean K2 tank.
I plan on using it as a platform to develop all my other robotics projects on.
Also, if my fears are realized and the tracks and sprocket aren’t strong enough, could you point me in the right direction to look for a place to get master links from bicycle chains by the hundreds or how to separate links from bicycle chains? I can easily get the sprockets, it’s just that the appropriate chain for them is expensive. So I could make something like this:
If you’re interested in the project(s), I’ll post a website in this thread by this summer. It’ll have mechanical and electrical schematics for almost every project.
The tracks we offer can withstand quite a bit of load, but the sprockets are intended to be used for small to medium sized robots and 120 lbs would likely have them crushed. Most of the robots we have in that weight range use custom tracks (which unfortunately we cannot offer separately). We don’t have a specific supplier for bike chain. We’re also looking for a reliable source for tracks / sprockets for larger robots.
So you’re saying the weight of 120 lbs would crush the sprockets?
What if I used a trapezoid track design with the driving sprockets off the ground like in a modern tank? That way none of the weight is on the sprockets and only on the idler wheels. I can get 2" idler wheels from an old conveyor belt laying around.
Would it be too much torque and destroy the sprocket teeth?
Also, you could try buying parts from amazonsupply.com, or mcmaster.com they have all kinds of ANSI chain and sprockets. They’re a bit pricy but if you buy in bulk the prices should be drastically cheaper.
I think the double pitched sprockets and chain should do the trick for heavier duty tank treads. That’s what I’ll probably end up using.
We prefer to purchase products which can be more directly used in robots; while a chain can be modified heavily to be used as a track, we’d much prefer to add something more custom designed. It’s hard to say if you don’t put the weight of the robot on the sprockets themselves if they can work; they have never been tested to that weight before, so it’s a bit of an unknown. Perhaps if you used two pairs of sprockets side by side it would distribute the weight more evenly.
Making my own isn’t the problem, it’s just these tracks looks nicer and would be much cheaper, a big part of this project is aesthetics. I’ll probably end up making my own with double pitch sprockets and an alternating link type tracks like on real tanks.
I am wondering how you mounted the drive sprockets? I notice the passive idler hubs for the passive shafts. Did you use the 6mm/4mm Lynxmotion hubs for mounting the drive sprockets? I can’t find any great pictures online.
