pic: Sheetmetal 8wd

I hopped on the sheetmetal bandwagon after the 2415, 148/217, and 1902 debuts. Thanks JVN and James Tonthat for the sheetmetal learning process help.

Questions comment concerns are welcome as always.

Looks really cool! A few questions:
Why did you decide to do 4 gearboxes instead of 2, as 2 would probably save weight.
I cant tell from the pic, but how are those crossbeams attached? Are they made of bent aluminum? Was there a structural reason to put the front cross beam at an angle?
Also, what was the weight as it?
Again, looks great!

More importantly, when’s this showing up on Shaker’s doorstep? We need it before July…

Oh, it’s a render. Silly me. :wink:

Seems very complex considering how simple it could be…BUT…it looks awesome and 4 toughboxs with 4 cims is very powerful! If only i could have that drive i would enjoy playing with it.

There’s nothing complex about it. I’m kinda curious about what you mean. The drive itself is very simple direct drive and then the corners are dead axle chained to the direct driven wheels. If you mean the lightening pattern, then yes, I made it a bit too random. I will be changing it to be a bit more structurally sound.

I chose 4 nanos because it made for the shortest runs of chain. I’ve also been playing around with the versatility of the nano a lot lately. (We also have some laying around).

Total weight was 26lb. with everything and some parts being .125" along with .09" thick.

Oh and no the angle of the crossmembers was just aesthetics. They are also bent sheetmetal.


If you have a sponsor shop where all they do is make this kind of stuff all day, and you have the proficiency to design this kind of stuff well (I do not), then this is REALLY the way to build an FRC robot in a short amount of time. It is so fast and easy to burn (or jet) all this out because the actual amount of material removed is so small, compared to milling. The amount of time saved over milling and welding more solid-type parts can be tremendous.

I’m thinking that with 4" wheels I can rework the geometry a little and place the CIMs inside the modules and save some space while still keeping it direct drive.
Badal Rastogi uploaded this image to

The blue and white are 2791 colors.

One thing I would be worried about with this design: It looks like the crossmembers are only attached on their ends. Being c-channels, you would probably see a lot of flex in the whole chassis. It would likely survive through competition, but I would be hesitant to use it.

Since you are designing it with sheet metal, you have the unique ability to make very large structural members that are still very light. Monocoque style construction is something that can be employed fairly easily and will result in a very stiff, very strong chassis.

I know that 233 had a similar drive set up as you do hear this year, but ended up chaining the two gearboxes on each side together. I’m not sure exactly, but I think it was due to torque problems when the front 4 wheels lifted off the ground when crossing the bump. Just something to consider.

What program did you use?

Can I have the CAD files… I would love to show this to my team… Looks really nice btw…

Sheet metal chassis like look HUGE, but in reality are a lot of empty space. I’ve really appreciated the look of the 217 / 148 / 1114 robots the last couple of years - they simply look physically imposing because of the lack of open space: they look massive.

One question though on this type of constructive. I imagine one of the trickiest parts of making a sheet-metal frame of this sort is doing the force modeling to understand where you can and cannot remove material.

How are you going about that?

The entire pattern on this was done incorrectly and very hastily, I did not look at the loads that well. I am redoing the pocketing right now. Obviously I made all mounting holes like JVN said and then carefully pocketed leaving .75" in between everything in the second iteration. Mostly I’ve been studying the CAD from 148’s 07-09 bots along with a few others and just working off of that.

I also redid the assembly to make it monocoque. I’ll post it up later tonight.


Ok so I redid a lot of the suggested stuff and restructured the trussing.

Badal Rastogi uploaded this image to

Badal Rastogi uploaded this image to

Badal Rastogi uploaded this image to

It seems to me that you could easily cut the height in half and save a bunch of weight that way. Also you need to think about some type of belly pan both to mount electronics and to greatly increase the strength of the whole assembly.

Also the cutout in the middle could be decreased a bunch. It looks to me like the limit to ground clearance will be the area between the middle and outer wheels and not the area between the middle wheels. There no need in having the middle have way more clearance. It just weakens things and makes it more difficult to run chains, plus raises the area where you can mount electronics, thus raising the center of gravity of the whole thing.

I’ll have to change it tomorrow, haha, been spending too much time with CAD instead of studying for APs. The height for right now was just set to make the GDC and their 2010 bumper rules happy.

Thanks for the suggestions and changes everyone.

2791 is going to be VERY interesting next year with Akash and Chris mentoring the same team and passing on the knowledge they both have! Beautiful CAD. Which reminds me, I need to finish my wheels and frame!

Were there only problems when going over the bump? I’m considering this type of dual gearbox per side set up but would not use it to traverse anything with such a steep slope as the 2010 bumps.

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