Re: Live vs. Dead axles
 

We usually have used dead axles. One year when we cantilevered our front wheels, we went live.

Using dead axles allows you to use the axle as a structural member. I see that as one strong advantage. It does not take us very long to do a wheel swap (but I admit its longer than some of you live axle guys are describing).

As somebody already mentioned, there are some nice wheels out there (IFI's, AM's, etc) that are suited to the dead axle approach.

Ken

Re: Live vs. Dead axles
 

.. for ease of maintenance silly :)

Re: Live vs. Dead axles
 

Though I haven't tried this specifically, you could always get most of the benefits of both systems by using a dead axle, and a live, quick-change hub. That would permit you to remove the wheel from the hub, but keep the chains attached. It seems easy enough to do with a couple of dowel pins for transmitting torque, rather than the usual bolted-together wheels and hubs, or single-piece wheel-and-hub units; you just need a way to constrain the components axially.

Incidentally, Woburn robots have typically used dead axles, but that was often because it was more convenient to use cheap bearings/bushings in the frame, and better bushings/bearings (or even oiled wood bores!) on the shafting.

Re: Live vs. Dead axles
 

Like a car! I hadn't thought of it that way. A car has a live axle which ends with a faceplate that has 4-6 lug bolts. You mount your tire by sliding the tire rim onto the faceplate, and tightening the lug nuts. Instead of dowel pins, a faceplate with bolts sticking out would handle your axial and radial movement when you tighten the wheel down with nylon-insert nuts.


What came first: the student or the mentor?

Re: Live vs. Dead axles
 

Design is all about tradeoffs.
I just happen to TOTALLY disagree with the tradeoff you're making; but that is pretty much par for the course. ;)

Re: Live vs. Dead axles
 

We use dead axles for pretty much the same reasons. Plus, old habits die hard...

Re: Live vs. Dead axles
 

I think we've used both, but I've only worked on dead. I can see the benefits of live, but I'm with JVN in this, I like dead better than the idea of live. The efficiency, durability, and the fact that we already have the parts is worth loss of quick change capability. Tristan's idea is interesting though... I really need to register Inventor.

Re: Live vs. Dead axles
 

I can't stress enough how important it is for robot parts to swap in and out in a matter of seconds or minutes. I can't say we would be National Champions now, but I know we could have come alot closer if our CIM motors were an a more easy to access position and we had full spares on hand.

I like the idea of the modular wheel that sits on a permentantly mounted hub. This solution seems to give you the best of both worlds (but may add weight. again, a trad off.)

Re: Live vs. Dead axles
 

If you have the resources to do it, I really can't see much of a reason not to use a live axle setup with hex broached wheels and sprockets. It makes everything so much easier. In the time it would take to remove one or two wheels from a dead axle setup, you could replace every wheel on a live axle setup. Using hex shafts to transmit power to your wheels also eliminates any concern of keys slipping, etc.

Re: Live vs. Dead axles
 

Another reason for dead axle--resources, or lack thereof. And for the live axles, you still have to pull the axle partway out (or all the way, thereby making it hard) of the frame, if you have a closed-frame robot (frame outside the wheels). So it may also depend on your frame design which is easier to maintain. If you have your wheels on the outside of your frame, it's easier to maintain them, but they take a beating and must be live axled. Inside, it doesn't matter.

Re: Live vs. Dead axles
 

This was the first year sense I have been involved with 116 that we have used dead axles, and if we had swapped our front wheels to the AM Trick Wheels for improved turning, the front axles would have become live (we had our front axle's with a double bearing set up).
I prefer live axles for ease of maitenance and for ease of sensor application. 116 has, for the past several years, used shaft encoders (or attempted to) to help our autonomous navigation. Because of the dead axle situation this year, we couldn't simply add them to our drive axles this year, and they only spot we could with our simple set up would have been on the output shaft of our gearbox (but because of a lack of space and time we couldn't).
Id also have to say that having an open frame over your wheels is probably a much bigger factor in the ease of replacing your wheels, but a live axle system is alot easier, imho.

Re: Live vs. Dead axles
 

I voted live axle on this one.

The live axle design we have used the last 2 years is very simple, low cost, requires little machining resource, and has been maintenence free (not a single failure through 6 competitions last year and 2 so far this year)

I think in reality the real answer is whatever you can do best is what is best. From reading the various benefits of each system in this thread, both can be great for you if done properly. I can also attest that either can be a nightmare if done improperly or if problems arise.

Some reasons that our decision to use live axles is easy are cost and machining. We do not have the machining resources to make good wheels for dead axles, and cannot afford the off the shelf products offered by some vendors. Our wheels, bearings, shafts and sprockets were under $175 for a six wheel drive setup.

So analyze your budget and machining processes and go with whatever you can do best. (good design helps alot as well :) )

Edit** Here is a link to a picture of how our live axle is set up. There is one long key going through the wheel and sprockets for each shaft. http://www.joemenassa.com/Images/ROB.../IMG_2877.html


Rob

Re: Live vs. Dead axles
 

Dead axles are simple, lightweight, structural, and lend themselves to standardization of: bearings, sprockets, axle shafts, pillow blocks, axle spacers, etc. We used the same general construction for wheels, pick-up roller, and launcher.

I would like to see some examples posted of live axle designs that have been refined and are working well for those teams that use them.

Jay

Re: Live vs. Dead axles
 

i prefer the use of dead axles, i have had to deal with too many thrown and eploding keys