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-   -   pic: Monocoque Treads (http://www.chiefdelphi.com/forums/showthread.php?t=78032)

AndyB 06-08-2009 17:17

pic: Monocoque Treads
 

sgreco 06-08-2009 17:17

Re: pic: Monocoque Treads
 
Wow, very nice render.

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

Good stuff though, I like it.

Akash Rastogi 06-08-2009 17:27

Re: pic: Monocoque Treads
 
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:

R.C. 06-08-2009 17:32

Re: pic: Monocoque Treads
 
Quote:

Originally Posted by Akash Rastogi (Post 869395)
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.

-RC

sdcantrell56 06-08-2009 17:42

Re: pic: Monocoque Treads
 
That is an absolutely beautiful render. I too am curious about how the tread is driven though.

EricH 06-08-2009 17:58

Re: pic: Monocoque Treads
 
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?

AndyB 06-08-2009 18:45

Re: pic: Monocoque Treads
 
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.

Akash Rastogi 06-08-2009 21:53

Re: pic: Monocoque Treads
 
What's the wall thickness of the various rails and the electronics pan?

AndyB 06-08-2009 23:20

Re: pic: Monocoque Treads
 
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.

Nick Lawrence 06-08-2009 23:59

Re: pic: Monocoque Treads
 
That kind of reminds me of the 2006 robots that NiagaraFIRST built.

-Nick

Akash Rastogi 07-08-2009 00:03

Re: pic: Monocoque Treads
 
Its also pretty similar to the frame 25 uses on their beautiful drivetrains.

Fe_Will 07-08-2009 00:07

Re: pic: Monocoque Treads
 
Looks like a good reason to not allow bumpers...

artdutra04 07-08-2009 00:10

Re: pic: Monocoque Treads
 
Quote:

Originally Posted by AndyB (Post 869448)
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.

...

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.

AndyB 07-08-2009 00:29

Re: pic: Monocoque Treads
 
Quote:

Originally Posted by Akash Rastogi (Post 869456)
Its also pretty similar to the frame 25 uses on their beautiful drivetrains.

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.

Akash Rastogi 07-08-2009 00:34

Re: pic: Monocoque Treads
 
Quote:

Originally Posted by AndyB (Post 869463)
I actually think I drew the most inspiration from team 1024's 2008 chassis as far as the fold pattern goes.

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

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

Mind sending the CAD over for reference? :)


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