small robot chassis ideas?

Whelzorn

I am in the process of building a small robot that uses steper motors as the drive system. These motors are fine for the drive, they have 3200 g-cm of torque and are going to fit inside a chassis thats (idealy) 4" wide, 6" long, and 3" high, which fits the motors nice and snugly. The problem is the chassis. I need something that I can drill precise holes in and is perfectly straight with no tapers. The radioshack plastic project boxes looked like an option for a while, but they were tapered and the steppers would be at enough of a slant to screw up their precision, which is what this robot is being built for. In my past few robots, I have cut and bent sheet aluminum into a U shape and mounted continuous rotation servos on the sides (much like the BOE-bot, but a little larger). That will not work this time, because my bends tent to be tapered or slanted a bit, so I am looking for sugestions at to what I should use.

Thanks,

Justin W.

Steve Joblin

I use a combination of metal plates that are used in truss construction (you can get them at any home center store near where the lumber section is) and stand-offs.· I have also seen folks use heavy circuit boards as well (that is, you can actually use a circuit board for both the electronics as well as a chasis.· This only works for small robots like the size you described.

Robert Schwartz

If the robot isn't going to be very heavy, sintra is a pretty cool choice. Its decently strong at heigher wiidths, is easily worked, and is light.

awasson

For small robots I've been using bakelite (old pcb material) and plastic. I've also used ABS Plastic with a cement that melts and pretty much welds the pieces together. You can get it in various thicknesses. It's light and very easy to work with.

bobledoux

Go to a glass shop and ask for a scrap of "Store front channel." This is aluminum extrusion used to mount windows in business buildings.

At Crankorgan.com you can see it used for homebuilt CNC milling machines. Look at his "Brute" model.

Whelzorn

ok, thank you for your responses, It appears I'm going to have to look for some plastics, mabe heavy pcb's as steve described. I'l just get some angle brackets to hold them perpendicular to eachother.

bobledoux

If you choose printed circuit board material you don't need any extra stiffeners. Cut your pieces and miter the edges. Solder pieces together down the edges. An extremely strong joint can be made if you solder both sides. For additional strength you can solder triangle gussets at the end of each joint.

Whelzorn

hmmm... thats an interesting idea... etch the pcb so the edges still have copper and solder them... Thanks bobledoux, I'll experiment with that idea and see what I can do!

Jurgen

I usually use plywood for my chassis, but I'm in timber business so I got plenty of it

Jonathan Allison

I'm big on reusing what I already have, so this may not apply to everyone but here is an idea. Tear apart an old PC, normally there are a couple of extractable frames within them. The metal is steel so it can be bronzed if needed, and they are metric, which to me is a plus. Also you are sure to have a whole collection of screws etc to use when you are done!

Don't forget about printers they have some decent framing inside them as well. You are looking for 4x6x3 thats pretty close to the frame which holds CDROMs in.

Good luck

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Johnny

Robert Schwartz

Just took apart the psu (power supply) to an old busted computer, and the housing is about 6"x5" ish with like 3.5" walls on two sides. It seems to be aluminum, so it will be easy to work.