6WD chain path

[Bill_Hancoc]

This year we are throwing around the idea of 6WD and i was wondering what other teams had done as far as chain paths go. We plan on having 2 separate dewalt motor/trans setups on each side for a total of 4. we do no plan on putting those through any sort of gearbox after that and dont plan on using any other type of transmission. What would be some different ways of doing the chain so that both motors for each side are powering all 3 wheels.
Thanks for the help

[Dylan Gramlich]

do this and it will be simple yet effective.

take a few pieces of paper, cut out pieces for your wheel and trans. then place them on the ground like how you will mount them. then take string and mock it up as chain.

that should help you out.

[sanddrag]

The best way to do this is have the Dewalt gearboxes direct drive your center wheel axles by means of flexible coupling (I recommend aluminum 3 jaw spider couplings made my Lovejoy and sold through Applied Industrial). Then just run a chain from the center to the front, and from the center to the back, on each side. If you have to, you can really drive any wheel from the Dewalt, but the centers are preferable because they are always in contact with the ground (if the center wheels are offset relatively lower than the rest). If you have to space to do it, you should avoid having 6 chains. It is more potential failure points.

EDIT: I missed the "total of four" thing

[Billfred]

Last year, 1293 did 6WD off of the Kit gearbox. We ran two chains off of the gearbox, one to the rear wheel and one to the center wheel, which then ran a chain to the front wheel. Worked beautifully--even when we threw chains from balls riding into the frame (a problem we fixed with bolts), we never threw enough chains to immobilize ourselves.

[lukevanoort]

In our 2006 'bot we used 6WD drive with the KOP tranny and frame. Our robot had its gearbox between the center and rear wheel with two chains, the "interior" one ran from the tranny to the center wheel, then front, then back to the tranny, the "exterior" one went to the center, then rear, then back to the tranny. There is a picture on the robot's FIRSTwiki entry that might help make sense of my description. The upshot of this layout was, with just two chains, we achieved pretty good redundancy, and any one chain could drop and maintain 5WD (really 4WD) capability, which was handy several times.

[Cody Carey]

Direct drive the middle wheel from a live axel, and run chain out to the other two, that way... no single chain failure can cost you an entire drive side. The only downfall is that you have to make custom hubs for the middle wheels.

In the below diagram... the blue is the chain, the black rectangles are the wheels, and the yellow boxes are the Dewalt Trannys. The middle wheel would be driven by the grey box, which is the live axel... The outlying wheels would be driven by chain and ride on dead axels.


Edit: I know that this would only use two of the motors... but it would be very easy to go with a setup like the one below as well:

You would just need to machine more hubs...

[Madison]

Originally Posted by Bill_Hancoc

This year we are throwing around the idea of 6WD and i was wondering what other teams had done as far as chain paths go. We plan on having 2 separate dewalt motor/trans setups on each side for a total of 4. we do no plan on putting those through any sort of gearbox after that and dont plan on using any other type of transmission. What would be some different ways of doing the chain so that both motors for each side are powering all 3 wheels.
Thanks for the help

I think most people have so far misunderstood this question, but please correct me if I've done so.

I would put each transmission between a set of wheels. The chain would run from an outside wheel to the transmission, then onward to the center wheel. This would result in two chains driving the center wheels such that, if one transmission were to become inoperational, all three wheels on each side would continue to be driven.

If you're considering shifting the Dewalt transmissions through multiple gears, consider what measures you'll need to put in place to ensure that each of the two gearboxes on a side shift in synchronization. If they don't shift simultaneously, you will be attempting to drive the center wheel at two different speeds and you may throw a chain or stall the system or any number of other really bad things.

Edit: Cody's second example is close to what I'm suggesting. My understanding of the Dewalt transmissions is that they still require a 'final ratio' to make them viable, so directly connecting its output to a wheel seems like an implausible arrangement.

[sanddrag]

Cody's second example seems redundant for the centers. I haven't decided if that is a good idea or not.

Couple questions. Will the centers be lower? Will you be shifting the trannies?

[ChuckDickerson]

For some reason I think having two separate gearboxes (in this case Dewalts) connected by chains such that both gearboxes are driving all three wheels may be a bad idea all together. What happens if one of the gearboxes goes bang? Unless the gearbox fails in such a way as to allow "free wheeling" the second gearbox would then be trying to drive a more than likely jammed gearbox and would itself be more than likely to go bang.

[Cody Carey]

Ahhh... Thanks for pointing that out

Yes, connecting the output directly to a live shaft is a terrible Idea, and would probably not work. I overlooked that, sorry. You would have to run chain from the gearboxes to the driven axels, and provide the correct ratio between the sprockets used in order to use the live axels, and that is overly complicated.

Would something like this be more appropriate?

[Jonathan Norris]

Originally Posted by DeepWater

For some reason I think having two separate gearboxes (in this case Dewalts) connected by chains such that both gearboxes are driving all three wheels may be a bad idea all together. What happens if one of the gearboxes goes bang? Unless the gearbox fails in such a way as to allow "free wheeling" the second gearbox would then be trying to drive a more than likely jammed gearbox and would itself be more than likely to go bang.

But how is that different than if the two gearbox's are geared together in the first place? I would recommend gearing them together at first if possible, but if you are using cim's why not just go with the KOP gear box? If you are using these gearbox's for shifting you may want to talk to teams that have done this before. There is a lot of power coming from the CIM motors, and I am not totally confident that those gearbox's can handle that stress. I think 188 had a tough time with those dewalt gearbox's last year on the drive (I may be wrong).

[ChuckDickerson]

Originally Posted by Jonathan Norris

But how is that different than if the two gearbox's are geared together in the first place?).

If two separate Dewalt gearboxes are on two separate CIM motors (or FP or whatever) and connected together by chains (or gears) and one of the motors/gearboxes fails for whatever reason (busted gearbox, fried motor, bad wiring connection, dead Victor, etc.) then the other Dewalt transmission is going to have a tough time turning the dead gearbox because it is geared down. If instead the two CIM motors are connected in one gearbox (like the KoP gearbox) and one of the motors fails the second motor has an easier time just turning motor that isn't working. The difference is whether the motors are connected before or after being geared down.

Originally Posted by Jonathan Norris

I would recommend gearing them together at first if possible, but if you are using cim's why not just go with the KOP gear box?

My point exactly.

[Cody Carey]

Originally Posted by DeepWater

The difference is whether the motors are connected before or after being geared down.

As long as they are both geared the same after the reduction, the motor in question should have the exact same difficulty turning the "dead" motor, except for any friction added by the drive train, right?

(Nowhere near right, proof of concept)
Before reduction:

The live motor outputs 10 units of force, and the "dead" one outputs 5 units of resistance against that force, so 10-5= 5 units of force being translated to the drivetrain, or Half of what was put into it.

After:

The live motor outputs 100 units of force, and the "dead" one outputs 50 units of resistance against that force, so 100-50= 50 units of force being translated to the drivetrain, or Half of what was put into it.


True?


Edit: This is assuming that no worm gears or anti-backdrive pins are in place.

[Bill_Hancoc]

Originally Posted by M. Krass

I think most people have so far misunderstood this question, but please correct me if I've done so.

I would put each transmission between a set of wheels. The chain would run from an outside wheel to the transmission, then onward to the center wheel. This would result in two chains driving the center wheels such that, if one transmission were to become inoperational, all three wheels on each side would continue to be driven.

If you're considering shifting the Dewalt transmissions through multiple gears, consider what measures you'll need to put in place to ensure that each of the two gearboxes on a side shift in synchronization. If they don't shift simultaneously, you will be attempting to drive the center wheel at two different speeds and you may throw a chain or stall the system or any number of other really bad things.

Edit: Cody's second example is close to what I'm suggesting. My understanding of the Dewalt transmissions is that they still require a 'final ratio' to make them viable, so directly connecting its output to a wheel seems like an implausible arrangement.

Correct, as far as shift syncro. we plan on putting the two motors lose together and using a single shift arm to shift both of them...mixed in with a little air powered magic i think i will work.

Originally Posted by sanddrag

Cody's second example seems redundant for the centers. I haven't decided if that is a good idea or not.

Couple questions. Will the centers be lower? Will you be shifting the trannies?

Our main goal is to be able o shift the trans's, we do no plan on lowering the middle wheel since we would use less grippy wheels on the outer ones.

To all the people that say to use the KOP Gbox we have used it in the past and had poor results with it and overall didnt like it because if its high wieght and a few other problems we had with it.

We have used the dewalts before(last year) and had good results from them, other than i few problems we caused ourselves.

[Gary Dillard]

How about something like Cody's layout number 1 (direct driving the center wheel, chains fore and aft) except instead of using one motor you gear 2 motors together like this

The setup shown has 4 "wheels" per side, with the fore and aft wheel driven by the belt; you could do the same thing with 3 wheels and chain, using the center gear to drive the wheel rather than the 2 outboard gears.