09-12-2008 14:53

gorrilla

Re: pic: FRC 1771 East (West) Coast 8wd drivetrain

what's the side rails made out of?



now if i can only come up with a south coast drive..........

09-12-2008 15:03

sdcantrell56

Re: pic: FRC 1771 East (West) Coast 8wd drivetrain

The frame is made up of 2"x1"x.125"thickness aluminum and 1"x1" aluminum all welded together. The entire frame right now without any work done to lighten it is 9lbs, and should be very stiff. I also have bumper mounts planned but I haven"t modeled them yet.

09-12-2008 16:20

Alex Cormier

Re: pic: FRC 1771 East (West) Coast 8wd drivetrain

Looks good but one question, how are you planning to run the chain? It looks like it will be a costly change during competition if you are planning on having the chain go through your support beams, I know it would be a lot easier to take the chain off as a whole instead of finding the master link and taking a chain off that way.

09-12-2008 16:34

sdcantrell56

Re: pic: FRC 1771 East (West) Coast 8wd drivetrain

If you look closely at the model, the round silver discs one the inside of the frame are actually sprockets bolted to the axles. The chain will run from the transmission to the 2 center wheels and then from the center wheels to the outer wheels. It will be incredibly easy to replace a chain although I doubt we will have to as I have never broken a chain. We will also be using 25 series chain. everything about this drivetrain is incredibly easy to work on. We can switch a wheel in a matter of seconds to keep the tread fresh. Also tensioning is super easy.

09-12-2008 16:39

AdamHeard

Re: pic: FRC 1771 East (West) Coast 8wd drivetrain

Quote:

Originally Posted by sdcantrell56 If you look closely at the model, the round silver discs one the inside of the frame are actually sprockets bolted to the axles. The chain will run from the transmission to the 2 center wheels and then from the center wheels to the outer wheels. It will be incredibly easy to replace a chain although I doubt we will have to as I have never broken a chain. We will also be using 25 series chain. everything about this drivetrain is incredibly easy to work on. We can switch a wheel in a matter of seconds to keep the tread fresh. Also tensioning is super easy.

09-12-2008 16:50

sdcantrell56

Re: pic: FRC 1771 East (West) Coast 8wd drivetrain

I chose not to direct drive a wheel so that we don't have to use custom gears or use an extra stage of gears. Also with this layout, the gear ratio can be switched very quickly by changing a sprocket size. This transmission uses almost no custom parts so it could be put together very quickly. I don't see enough benefit in directly driving a wheel to make it worth the machining effort. Also the way the motors are oriented at the bottom of the transmission helps lower the center of gravity more than if the motors were at the top of the transmission.

The wheels are actually incredibly simple. They will be made from a length of aluminum tube, and 2 separate plates of aluminum that will be laser cut to form the spokes. The entire thing will then be welded. The reason I did it this way is that we are sponsored by a sheet metal shop that does not have any cnc milling equipment, but has plenty of laser cncs, and the material to make these wheels is much cheaper than buying the billet necessary to machine a single piece wheel from.

09-12-2008 17:08

M. Mellott

Re: pic: FRC 1771 East (West) Coast 8wd drivetrain

I'm sure all 8 wheels are not touching the carpet, so which ones have been raised/lowered?

09-12-2008 17:25

sdcantrell56

Re: pic: FRC 1771 East (West) Coast 8wd drivetrain

the middle 4 wheels have been dropped by .175"

09-12-2008 17:34

MrForbes

Re: pic: FRC 1771 East (West) Coast 8wd drivetrain

Quote:

Originally Posted by sdcantrell56 The wheels are actually incredibly simple. They will be made from a length of aluminum tube, and 2 separate plates of aluminum that will be laser cut to form the spokes. The entire thing will then be welded.

09-12-2008 17:40

sdcantrell56

Re: pic: FRC 1771 East (West) Coast 8wd drivetrain

Yeah it is very simple and a lot cheaper. The spokes have a 7/16" hex cut in them that interfaces with a hex on the end of the axle. The wheels will be held on either with a bolt tapped into the end of the axle or with a ring clip. The axles are machined out of 7075 aluminum and have a hub on the opposite side to bolt plate sprockets so that we don't have to use hubbed sprockets, and we can have custom sprockets cut very cheaply (free )