Sheet Metal vs KitBot

[Ether]

Originally Posted by DinerKid

We have done 6 wheel rocker, mecanum and 8 wheel rocker and even Ackerman drive with the kit-bot chassis.

Did you use independently steerable swerve modules for the Ackermann and compute the inside/outside Ackermann steering angles in software, or did you design a mechanical linkage capable of doing that?

[DinerKid]

Originally Posted by Ether

Did you use independently steerable swerve modules for the Ackermann and compute the inside/outside Ackermann steering angles in software, or did you design a mechanical linkage capable of doing that?

We used a mechanical linkage to do it. It was actually 4 wheel Ackerman (don't know if this setup has a different name). The front wheels would turn one way and the back wheels would turn the opposite way, while the inside and outside wheels also compensated for the variable radii of the turn.

We did this for Lunacy and it was really cool when it was working however we had some massive issues with some couplings we were using (the tolerance needed to be tighter than we thought) which prevented us from ever getting to really show it off in competition.

~DK

[Ether]

Originally Posted by DinerKid

We used a mechanical linkage to do it. It was actually 4 wheel Ackerman (don't know if this setup has a different name). The front wheels would turn one way and the back wheels would turn the opposite way, while the inside and outside wheels also compensated for the variable radii of the turn.

Did your team ever post a paper or a presentation with some details?

[DinerKid]

Here is a picture of it partially built. We didn't ever put together a presentation or anything like that. The helical couplings were what really made it happen for us.

~DK

[AdamHeard]

The drivetrain is an iteration of what weve run for a few years now. We collaborated with 1323, so they inherited our design.

You are correct that it is not welded. This made it faster and easier four us to build as welding has always been a bottleneck for us.

Originally Posted by Andrew Schreiber

Adam, I've been meaning to ask you about your DT actually. I know that 973 and 1323 were very similar this year (how similar were they btw?) and I know that 1323 did not weld their frame. Did 973 weld their frame and have you found any major benefits to a welded frame over a bolted together frame?

Edit: apparently I'm an idiot, it just LOOKED bolted in the picture. Questions still stand but disregard my incorrect information.

[Andrew Schreiber]

Originally Posted by AdamHeard

The drivetrain is an iteration of what weve run for a few years now. We collaborated with 1323, so they inherited our design.

You are correct that it is not welded. This made it faster and easier four us to build as welding has always been a bottleneck for us.

Were there any major downsides to not welding it?

[AdamHeard]

Originally Posted by Andrew Schreiber

Were there any major downsides to not welding it?

It did make it a big uglier, as we put bolted some "endplugs" inside the frame rails, and then the crossmembers bolted to them. So we had some bolts and holes where we usually have nice clean frame.

Other than that, no. It worked out great. It was identical to this frame here, minus the intake and crossmember.

[sanddrag]

Originally Posted by DinerKid

Here is a picture of it partially built. We didn't ever put together a presentation or anything like that. The helical couplings were what really made it happen for us.

~DK

Whoa. Those couplings are not meant to flex that far.

[Ian Curtis]

Originally Posted by sanddrag

Whoa. Those couplings are not meant to flex that far.

Which is probably what led to this:

Originally Posted by DinerKid

We did this for Lunacy and it was really cool when it was working however we had some massive issues with some couplings we were using (the tolerance needed to be tighter than we thought) which prevented us from ever getting to really show it off in competition.

OTOH, FRC robots have such short lifespans it is kind of neat to see things used outside of their original purposes. (Obviously though, you've got to do some testing to demonstrate that it will actually perform)

"I don't care about what it was DESIGNED to do... I care what it CAN do." -Gene Kranz during Apollo 13

[DinerKid]

Originally Posted by sanddrag

Whoa. Those couplings are not meant to flex that far.

We got them from Helical Products Company and this was one of the main things we discussed with them. The couplings we had were operating within their spec. we worked a lot with that company that year and I can assure you that it was not their fault. The shafts that we had put into the wheel side of the coupling were a few thousandths undersized, not enough for us to worry too much we figured we would have enough adjust-ability by tightening the end of the coupler. We were wrong. What ended up happening was the coupling would spin but the shaft was not held tight enough so the wheel shaft didn't spin along with it. It was in no way an issue of over angling the coupler or an issue with the quality of the coupler. Helical Products Company was a great recourse for us and in the end we made a fatal error.

~DK