Mounting of drive system

[mattotters]

On our bot the wheels has always been keyed to the axel shaft and this year we want to try to have the wheel spin on the axel we have the correct wheels set up i just want to know what is the best/most commen way to attach the wheel to the frame.

any tips pictures would be great =D

[EricH]

Originally Posted by mattotters

On our bot the wheels has always been keyed to the axel shaft and this year we want to try to have the wheel spin on the axel we have the correct wheels set up i just want to know what is the best/most commen way to attach the wheel to the frame.

any tips pictures would be great =D

Ah, going from a live-axle (axle turns the wheel) to a dead-axle (wheel turns on the axle)? Common methods include just using a bolt that only has thread on the end, or a steel shaft that is pinned in at both ends.

[Sam N.]

In 2006 we had our wheels spin freely on axles. The funny thing is that the axles were able to spin freely too. It worked!

Just make sure the bolts connecting the sprocket to the wheel are strong enough.

Sam

[mattotters]

Originally Posted by EricH

Ah, going from a live-axle (axle turns the wheel) to a dead-axle (wheel turns on the axle)? Common methods include just using a bolt that only has thread on the end, or a steel shaft that is pinned in at both ends.

I was personaly thinking of a pillow block with out berings, have you ever seen this?comments?

[EricH]

Originally Posted by mattotters

I was personaly thinking of a pillow block with out berings, have you ever seen this?comments?

I've seen pillow blocks, but my team has gone through the frame with an axle the past three years. I can't remember if we used bearings in our pillow blocks before then or not.

Edit: We used bearings on our 2004 robot, but we had some odd-shaped pillow blocks that year, and I can't remember how we mounted our front wheels. Can't find clear enough pictures of previous robots on CD to make the call there.

[MrForbes]

Really simple method is to just drill a hole in each side of the frame, and put a tube spacer on each side of the wheel bearing, and a long bolt thru the middle.

Better is to also add a tube between the bolt and the spacers and bearings, so the bolt can be tightened up all the way and not spin, as shown in the drawing.

[lukevanoort]

I'm actually planning on doing a bearingless pillow block style design this year (assuming the game calls for 6WD). Here's why: with a hole through the frame, you have to decide on the how much lower the centre wheel is when you make the frame; however, with a pillow-block style design, shims can be used to adjust the lowering. Since the amount of lowering is adjustable, we can then test for what gives us the best driveability. (It could also allow us to adjust the lowering before every match, but I'd rather avoid the trouble of doing that by just picking a good amount and sticking with it)

[krankin]

last year we had a shaft collar on the out side of the axle and a pipe acting as a spacer between the wheel and the frame. but we did have a very hard time lining the chain up.

[maclaren]

I think that a dead axle is the only way to go. The reason being is that the torque is moved out from a tiny key to a bolt pattern on the side of the wheel which causes less wear and problems and allows you to remove a lot of weight.

The method of using a "pillow block" with no bearings is a good method and the industry name for these are shaft hangers. On our 2005 robot we used a 5/8" aluminum tube axle with shaft hangers that had a socket head cap screw holding the axle in the shaft hanger and keeping it from spinning. If you want to use a aluminum axle I would recommend using a Rulon or PEEK Flanged plain nearing pressed into your wheels. Rulon and PEEK are PTFE(teflon) composite berings that are specifically designed for soft shaft materials. Many other beraings are designed for hard or very hard shaft materials such as hardened steel axles and those are heavy.

A nother way to do mount a dead axle if you are using palt side panels on your drive train is to tap the end of you axle and machine a flat in to the end of the axle and and then machine a corresponding shape into the face of the side plate and then drill a hole for the screw through the side plate. But this requires a lot of machining

If you do it right there is virtually no torque on the axle and if you make sure to have little to no unsupported length in the axle then it will have no chance to deform or bend. We even used a 1/2" aluminum tube axle on the front caster wheels that we had on our 2006 robot.

[EricH]

Originally Posted by maclaren

The method of using a "pillow block" with no bearings is the method of choice in my opinon and the industry name for these are shaft hangers.

I guess some folks just like using their frame as pillow blocks, and others just use the blocks.

Come to think of it, I can only think of one year in my five on the team that 330 has used blocks--we had an odd frame designed for the 6" step in 2004, and used blocks to lower the rear wheels.

[=Martin=Taylor=]

Originally Posted by mattotters

On our bot the wheels has always been keyed to the axel shaft and this year we want to try to have the wheel spin on the axel we have the correct wheels set up i just want to know what is the best/most commen way to attach the wheel to the frame.

any tips pictures would be great =D

Here's a picture of last year's prototype drive train.

Each axel is a 3/8" bolt riding on two pillow blocks. The pillow blocks have a slot milled in the bottom to keep them in-line with the 80/20, preventing them from twisting. The pillow blocks can slide in the 80/20 to tension the chains.

We used slightly larger aluminum tubes as spacers to position the wheels on the axels. We used this system last year and it worked really well. However, we'll be using canelivered wheels in 2008 and will therefore need to use live-axels.

[MrForbes]

Originally Posted by lukevanoort

I'm actually planning on doing a bearingless pillow block style design this year (assuming the game calls for 6WD). Here's why: with a hole through the frame, you have to decide on the how much lower the centre wheel is when you make the frame; however, with a pillow-block style design, shims can be used to adjust the lowering. Since the amount of lowering is adjustable, we can then test for what gives us the best driveability. (It could also allow us to adjust the lowering before every match, but I'd rather avoid the trouble of doing that by just picking a good amount and sticking with it)

1/8" is what you want, no need to go to too much trouble just to make it adjustable.

[EricH]

Originally Posted by squirrel

1/8" is what you want, no need to go to too much trouble just to make it adjustable.

How much drop you put in depends how much rock you want/need. I can't remember offhand how much 330 drops their center, or any other recommendations (I'd say 3/16, but that's way too much--more likely 3/32 or 3/64.)

[lukevanoort]

Originally Posted by squirrel

1/8" is what you want, no need to go to too much trouble just to make it adjustable.

I'd tend to agree, but I think it would be really handy to put a couple of current sensors on the drive motors and get quantitative numbers on how much difference it makes. Plus, adjustable pseudo-pillow blocks really aren't that much harder than what we'd be doing anyway. Assuming the kit frame doesn't change much, we'll probably be using the it next year, and to get less rock rock on it, we'd have to go to a pillow block style mount anyway, might as well adjust it.

[Ian Curtis]

Originally Posted by EricH

How much drop you put in depends how much rock you want/need. I can't remember offhand how much 330 drops their center, or any other recommendations (I'd say 3/16, but that's way too much--more likely 3/32 or 3/64.)

We drop 3/16. It gives us great turning, but it does rock enough to be annoying.