A system for maintaining even pressure on the middle wheel of an h drive system. Our Mechanism allows the center wheel of an H-drive to ride along linear bearings to compensate for inconsistencies in the floor, currently set at .5" of maximum travel, although the design is readily scalable to any travel required. The central wheel is attached to linear bearings mounted on steel guide rods, with down force provided by springs. The springs are set to be compressed only to half their initial length, as to minimize strain on the springs and increase their lifespan. Attached are the idw drawings of our parts, our McMaster Carr order, and screenshots of the suspension system. (Rod must be steel to avoid stick-slip, for better Coefficient of friction, and for increased rigidity. Also springs are calibrated for a small, 50 lb robot. Because springs are not fully compressed to improve reliablility, they should be rather strong…)https://www.dropbox.com/s/y3hdnpe6ygaw46x/WhitePaperFiles.zip?dl=0
This is a super cool system! Interesting to look at!
I’m surprised that you chose to put it between two springs. I think one spring with a linear pivot (like a hinge or the bushings on a car control arm) would be simpler and work better. Less likely to jam.
Also, your whole wheel load is cantilevered against the two sliding bearings. This looks like a potential problem to me.
And linear bearings are expensive too.
What was the thinking on that?
A very minor observation: PNG files are ill-suited for renders and photographs.
Attached is an 80K zip file for all 4 files in JPG format.
JPG.zip (79.3 KB)
We initially considered a pivoting system like you described; however, in our application it took up too much space, and we would’ve had to run a belt to the wheel, which would’ve been a nightmare to tension as the wheel isn’t fixed… as per the cost we already have some low friction oil impregnated bushings that have worked well for us in the past under similar moment loads. considering the cantilevered force is only on the roller portion of the omni wheels it shouldn’t be too big an issue. Also with the spring system we thought keeping the wheel perfectly vertical instead of slightly angled from the hinge would provide slightly better traction with the force evenly distributed. If we had space we would probably use the design you suggested, thanks for your feedback!
Technically that was an error; we used low friction linear bushings, much cheaper than specialized bearings…