I’m beginning the design of a fairly hefty outdoor robot. Initial design numbers are saying the robot will have to weigh 50-70lbs to carry the 30lb payload for 2-3 hours.
I allready have two, 200W planetary gear reduced AC motors, parts ordered for the motor controllers, vision system, microprocessors, SLA 12V batteries (plan to use 60AH for motors, 10AH for brains).
My question is; Will the tank tracks offered by lynxmotion hold up to a robot that big?
My calcs say ~30lb/ft of torque to carry 100lbs up a 30% slope, neglecting friction. Can the tracks/sprockets handle that much force?
Has anyone else produced a robot that big?
Both the three and two inch tracks will hold up to that no problem.
So will the sprockets if they are used in pairs.
is there a data sheet with numbers? I dont want to get several hundred dollars into some lynxmotion tracks to find they dont suit my needs.
I have no problem believing the tracks can hold up to the forces involved, there is plenty of interlocking pieces to spread the force.
My main concern is the sprokets. Worst case is the robot traversing a steep slope with 100LB load. that means 20+lbs lateral force per sprocket. I’m not convinced those plastic gears could handle that for too long.
I’ve personally tested the lynxmotion sprockets on a 120 lb rover, 3 feet long carrying a 100 lb payload. 2 pairs of 11 tooth sprockets on front and back, so 4 front, 4 back each side and 6" idlers on the bottom. They presented no flexing or fatigue whatsoever.
I also could jump on the rover while it was moving the sprockets held up fine.
Trust me, the track and sprockets are more than strong enough for your application. I’ve attempted to destroy these components to find their failure point. But stopped trying after torturing them with 3 hp motors and 220lbs of load.
Nope, the idlers were lawn tractor tires. And I doubled because of the design I used. The robot had a 7 foot track section on each side.
2 on each end would work fine for anything under 120 lbs.
I do not have any exact specifications for you, but Jim (Robot Dude - main guy @ Lynxmotion) said that the tracks and supporting equipment can hold hundreds of pounds (assuming no obvious mechanical design flaws).
Sorry if I ask alot of questions, I’m anengineer and I am used to having a proper spec sheet so I can design around any weak points in the product. In this case I need to rely on other peoples experiences with this product, in use on large-ish robots.
Evolution:
Were you using 2" or 3"?
Were the tracks tensioned or did they hang slack on the top run?
Is there any problem with the track moving off center from the non-sprocketed idlers when traversing on a slope?
Any other key learning would be greatly appreciated.
This tested was with the 3 inch track. Never any derailing issues, and the tracks were tensioned across the top end shafts. No center idlers used on top in this test.
Rest assured, it would take more force than a 120lb robot, with even the strongest motors, could provide to even come close to break the links lengthwise. And their sideloading is equally impressive. For lateral compression, we are talking hundreds and hundreds of pounds.
In all actuality, although they may look “plastic” and limited in abilities, they are extreme overkill for small rovers. These tracks are more than capable of handling the forces that any 120lb rover can dish out.
Whether or not you will require sprockets for the bottom level of the track module will depend on your design length, tension and height. Height most importantly and length second. Anything over 24" long and 9" tall should probably have lower sprockets to maintain proper tracking.
If you use a 2 shaft track module, you will not need sprocketed idlers in the middle unless you plan to exceed 24" center to center.
Evolution:
Your awesome. Thanks for the quick replys.
I am planning on running the tracks lengths longer than 24 inches. I think I will be purchacing 6 lengths in total (138 inches total). But I was hoping to use the 2" wide stuff. it’ll be a $84 difference in cost just for the six track lengths. I guess I’ll be using sproketed idlers.
Thnaks again.
