pic: Monocoque Treads

This is a monocoque frame with treads that I designed last offseason. I was sorting through some folders and found the render and thought I’d share it. The frame shown is made entirely from one sheet aside from the two crossbars. Looking back on it now, I don’t like the crossbar design, but I thought I’d share it anyways.

Rendered in Inventor 2009.

Wow, very nice render.

Excuse my ignorance, but how do you get power to the tread itself?

Good stuff though, I like it.

That looks amazing Andy. :yikes:

I’ll definitely have to take a crack at replicating that next week. RC’s thinking the same thing right now probably. :rolleyes:

WOW Akash, you read my mind:D But Andy, that looks SICK. ME LIKEEEE.


That is an absolutely beautiful render. I too am curious about how the tread is driven though.

It looks like the drive system is in the middle, where what seems to be an axle pokes out from a bearing. I’d say right above that is where the drive goes. Am I correct?

Yes Eric, you are correct. If you look closely, a bit of shaft is sticking out of the middle into the bay of the frame. I think my original intentions were to use a Gen 2 AM shifter but the shaft is standard 1/2" keyed, so direct drive would be possible as well.

What’s the wall thickness of the various rails and the electronics pan?

I’m not 100% sure on that. I found the cad file of the design and noticed that the wall thickness was .1in, but that’s hardly accurate. In a design like this, I’d probably use .08-.09" for 6061 aluminum or .03-.05" for some sort of galvanized steel. I’d probably use sheet steel just because it’s readily available to us.

I’ve never actually worked with sheet steel within FIRST robotics. I tried doing some research on it but couldn’t find much in terms of second hand experience. I’ve used chromoly steel back when I was with 269 but the properties of chromoly extrusion and galvanized sheet steel are probably pretty different as well. I’ve heard the number 3x the weight/strength when compared to aluminum but I have no clue if that’s correct or not. It was with chromoly extrusion compared to aluminum extrusion which is why we could use .035" wall thickness extrusion.

So to answer your question Akash, .08-.09" Aluminum or .03-.05" Steel.

Something interesting to point out now that I’m looking at the design more up close is how the rollers are set up. There are no crossbars inside the tread modules to add support. At least not any supports designed solely as crossbars… the axles for each roller are dead and the UHMW or UDPE rollers spin freely on them. This way, the roller acts as a crossbar support as well.

That kind of reminds me of the 2006 robots that NiagaraFIRST built.


Its also pretty similar to the frame 25 uses on their beautiful drivetrains.

Looks like a good reason to not allow bumpers…

One of the general rules of thumb when working with sheet metal is that aluminum sheets need to be 40% thicker to achieve similar structural properties. Since .080 to .090 wall thickness aluminum sounds about right for a well designed FRC frame, the equivalent steel thickness would be a little higher than your estimates, in the .060 to .063 range.

Depending on the actual alloy used however, these figures will vary.

Thanks for the info Art. I’ll keep that in mind for future sheet steel projects.

I actually think I drew the most inspiration from team 1024’s 2008 chassis as far as the fold pattern goes. However, I definitly took a few looks at the NiagraFIRST 06’ bots while designing this as well. At the time, we were seriously considering building this drive system. I contacted Karthik regarding belt selection and he highly recommended Gates belting over Brecoflex.

During kickoff last year, when they announced the slick floor surface, our team all looked at eachother with huge smiles because we thought for sure this design would be coming to life… and then 5 seconds later, they announced the rover wheels mandate.

I’m loving the fold pattern, the lightening pattern is what 25 uses.

Mind sending the CAD over for reference? :slight_smile:

You can download the cad at:


Speaking of 25, I have been looking closely at their 2006 drive lately. I like their use of ITEM/8020 with sheet/plate aluminum.

Sweet, thanks a lot :slight_smile:

I could def see myself converting this frame a little to use the Skyway bead-lok wheels 25 uses.

Some people definitely underestimate the use of 80/20.

Btw, did you use any additional rendering software/add-ins with SW for this?

Andy uses Inventor 2009 :wink:


Then I am definitely speechless. Best. Inventor. Rendering. Ever.

k, I’m done commenting now:o

I wish I still did… This render was done in Inventor 2009 but I’m now on 2010. Aside from the obvious compatibility issues, I hate the ribbon.

Thanks all for the kind words.