Re: pic: sheet metal 6WD
 

Great explanation :D

The loss of a continual flange will not only decrease the second moment of area, but will also "chase" the stresses to the ends of the flange.

Re: pic: sheet metal 6WD
 

If that's the case, what's your basis for saying it'd be okay to remove the bottom flange entirely?

Re: pic: sheet metal 6WD
 

Different design. The flange I said would be okay to remove was the bottom external flange. The top external flange used to mount bumpers will working in tandem with a properly mounted plate should, depending on material thickness, provide more than adequate structural integrity. That's why I said you could most likely remove that flange.

Re: pic: sheet metal 6WD
 

Ah. Did you use any kind of analysis to come to this conclusion? I'm trying to learn all I can here. :)

Re: pic: sheet metal 6WD
 

Not on this specific piece, though I re-designs our kicker plate (under roughly 300 lbf) to make it lighter and not deform. This was one of the things I frequently noticed.


This is with a continual .5 inch flange on the top and bottom, 100lbf, fixed constraints at the bolt holes.
http://picasaweb.google.com/11295163... 6928451693122

This with a 5 inch break in the top and bottom flanges, same load and constraints.
http://picasaweb.google.com/11295163... 6931950242546

Re: pic: sheet metal 6WD
 

Another way to strengthen a frame such as this is adequate attachment between the inner and outer drive plates. This combines them into a much larger, and much stronger beam (a ~3-4" tall I-Beam).

If you understand the basic concepts, you'll quickly see that rather trivial and easy changes in design can cause appreciable increases in strength.

Kajeeven, this isn't a criticism of your design, I would definitely classify your attachment as adequate. It's just a convenient place to mention such concepts... Too much what on this forum and not enough why.

I do highly recommend adding a single baseplate that attaches to all members of the frame, or at least the full length of the front/back crossmembers and inner drive rails. This will greatly increase the rigidity of your frame. Think of it as an infinite amount of crossupports, providing strength in whatever direction is needed at the moment. Also provides a very low CG friendly electronics mount.

Re: pic: sheet metal 6WD
 

The op may be looking at doing something different and lighter to mount their electronics (http://www.chiefdelphi.com/media/photos/27670) It would be possible to use cables under tension to mount your electronics to and use your frame (which should be pretty rigid in most cases) to ensure tension. Not only that but there is no fear of shorting out if you use a plastic coated cable.

Just saying, there are alternate ways of mounting electronics that many teams haven't looked into, all of these have the benefits and their drawbacks which must be considered.

Re: pic: sheet metal 6WD
 

To answer a few questions,

I went with 1/8in Al trying to avoid having to put plates around the axles for strength and having to deal with smaller pieces. Also I was hoping to have the side plates tapped so I might not need nuts and just adjust the clutch on the drill to not strip the treads when inserting bolts.

The chain is tensioned with a bent C-channel with extra flanges for strength that hug the axle and is pulled by one 5/16'' bolt. The chain can be tensioned up to 1''. If you look closely enough you can see it.

I don't believe it's possible to have the AM SS in line with each other.
I am using pneumatic shifting.
I positioned them sideways to have easy access to the encoder and shifter.
Speeds are 5 and 18 feet per second.

There is no base plate yet but will be once the function is decided and its worked around it. But the front and back plates connect the entire base together and act like a small base plate at the triangles preventing racking.

Sorry for the late response been busy for a while.

Re: pic: sheet metal 6WD
 

Overall, this is a solid looking design. I agree with previous recommendations that you don't cut away flanges for the gearboxes. It looks like you may have room to bend the flange towards the wheels. Also, depending on the manipulator required, you'll likely want an opening at the front of the frame.

I agree that using thicker material can be simpler than reinforcing thinner material. I'm not sure you should put threads into .125 aluminum though. It'll strip really easily. You should look into PEM nuts. They press into holes in your sheet metal and provide much stronger steel threads. We use them all the time. The correct way to install them is with a press, but we find just cranking them tight with a cap screw will seat the teeth into the aluminum just fine.

I like this design a lot! It looks like a great way to tension the chain. My only suggestion would be to put flanges at the front of the C-channel where the pull bolt goes through. Otherwise this area would bend quite easily. Also, why a 5/16" bolt? A 1/4" or even #10 bolt would be fine.

Triangles are good :)

Rob