Re: Mounting of drive system
 

A hex shaft is another option for a live axle. No "tiny" key required.

Re: Mounting of drive system
 

I'm sorry Im a nub, but does dead-axle have anything to do with using pillow blocks?
Pillow blocks are quite expensive on mcmaster-carr (about 30 bucks a piece)

is live-axle a more economical choice?

and with a live-axle, would you have to connect the sprocket to the shaft?

sorry for the nub questions

Re: Mounting of drive system
 

The easiest newbie way to do it is to mount the wheel on bearings on a "dead" axle that is just a bolt thru the frame. The sprocket then bolts to the wheel.

Whether or not you need blocks to mount the dead axle, depends on the design of your frame. The kit frame has flanges with holes in them designed for a bolt type dead axle. If you use that extruded stuff then you may need to make blocks or angled plates to mount the axle.

With a live axle, connecting the sprocket you can buy hubs, most teams who use a live axle make most of the parts themselves, it's not really a newbie appropriate thing to try unless you have good help.

here are some of the hubs, the keyed and hex hole type are what you might use

http://andymark.biz/hubs.html

Re: Mounting of drive system
 

Nothing really. What I'm talking about is a block of aluminum with a hole drilled partway though (like halfway maybe) so it can hold an aluminum shaft as a dead axle. Then, the block is mounted to the robot with bolts and its height can be adjusted with shims. Not really a pillow block in the traditional sense, but similar.
Generally no. A bolt through a hole in the frame can serve as a dead axle, with live you need keyed/hex/spline/etc shafts, bearings, pillow blocks, so on.
Usually yes. If you used gears for power transmission, you'd connect those to your shaft.

Nothing to be sorry for, everyone was a newbie sometime.

Re: Mounting of drive system
 

Dead axle systems are usually lighter then the live axle, and there's less moving parts.

Also, the drop of the middle wheel on a 6wd depends on the type of wheel used.

Re: Mounting of drive system
 

I wouldn't be so quick to say "usually". If live vs. dead is the only difference, then you're probably right. The axle moves in a live system, so that's one more moving part. But the live axle system I'm most familiar with has the axle itself as the gearbox output, saving several parts (sprockets and chains at least). You can just use a live axle in the same sort of application one might use a dead axle, but you get additional design options when you choose a live axle.

Re: Mounting of drive system
 

Take a close look at the front view of the module attached to this post.

Re: Mounting of drive system
 

Also, please take a close look at the 1st picture where it shows the tensioner and how we used shaft collars instead of spacers. It was a lot less hassle when it came to take everything apart.

Re: Mounting of drive system
 

Not only that, it was a good technical question that prompted further discussion. It has been a while since we've had a good live vs dead axel discussion.

Re: Mounting of drive system
 

Last year we used shoulder bolts as axels through the frame, which worked well.

Live and dead axle drivetrain
 

For the two years we've done 6 wheel (06, 07), Team 190 used both live and dead axles. The center wheels were driven using live axles with a keyed shaft and the end wheels were sprocket and chain driven from the center on dead axles.

Besides the gearing change between the years, the only major difference between the two drivelines was the chain path. In 06, we had a convoluted one to incorporate a system that got taken off the robot before ship, and after almost every match we were retracking a chain. In 07, we had straight chains with simple tensioners and never had any drivetrain problems (until we got to offseason demos and the bearing blocks had worked themselves loose).

The advantage to this system was that it was compact, as the center axle was just the output shaft after a gear reduction, and the outer wheels were just shafts bolted to the frame with wheels on them.