It is posted here on GrabCAD.
Any feedback is greatly appreciated.
Love the use of 3112T31. Almost perfect COTS; just need to drill out the 1/4-20 thread and tap 5/16-24.
Are those cylinders strong enough? There will be side loads …
Would really love to see a parts breakdown, and a cad for the modules and where in the chassis they attach. I love the idea of making the kop chassis upgradeable!! Hopefully Andy sees this thread and gets up with the op on the design. Would be an outstanding option to have available for teams.
Each one, with some wiggle room, should lift about 45 lbs at 110ish psi. Side loads shouldn’t be an issue do to the lack of hard mounting on the rod. Using the lifting eyes should just allow it to slip, right?
The amount of lever arm that is created by the module with only one mounting point in sheet metal would be a bigger concern to me. Then again, maybe the omnis won’t allow much side load due to the fact that they are omnis…
But you only have 60 psi to use.
I am assuming that the butterfly pivot point is at the axis rubber tread wheel; if it’s anywhere else, please disregard.)
I agree about the side loads (and won’t those be minimal with the omni wheels in the first place?), but max FRC working pressure (caveat rule changes) is 60 psi, reducing the lift to about 26.5 lb. As this is applied at a lever arm nearly twice the distance from the pivot, this should be enough.
Nubs are cool. I generally favor using FTC parts in FRC when it is feasible.
However, in this application I would replace them with flange nuts like these, and use 3/8" bolts for both omni axles and lift points.
Man I was feeling good about my ability to do math in my head… turns out you have to start with the right numbers.
Nice Design and modification of an existing chassis. I like the idea a lot, but I have a few comments on this implementation:
What do you use for chain/belt tensioning? as far as I can see there is none yet, which will lead to problems.
Right now it looks like the Chain you use to go from wheel to omni wheel is larger than the diameter of the wheel. The sprocket is just under the wheel, so the chain will certainly be touching the carpet. This would be bad for several reasons, the least of which is it is currently illegal to have metal touching the carpet.
Finally I think the plates you use to attach the omni wheel to the standard wheel are too weak. There is almost nothing keeping the two plates from parallelogram-ing. You have defined them so they remain parallel, but when the feel large sideways loads they will move to be a parallelogram instead of a rectangle. This wouldn’t be too much of a problem except for the fact that you have chain running through these, so if it parallelograms while you move, it is a recipe for the chain to jump.
These are just some thoughts I had after looking at the grabcad for five minutes, so it is very possible I am wrong. This is just my gut reaction after looking at the design.
As far a belt tensions, the kit bot doesn’t have them and if this is using the same geometry I see no reason for it to need them, the chain I’m not sure about.
If I understand the design correctly the outside plate of the kit base would still be included and that would prevent the modules from parallelograming.
Overall I like the design and the idea of being able to upgrade the kit is something I’ve wanted to do for a while.
