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Originally Posted by DieselDoctor
Jonathan, I'm not arguing here, I agree with all your statements about traction
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Stan, (That is the right name isn't it? Hope so.) I didn't think you were arguing. I was pretty sure you understood, as you made the comment about it needing walking suspension like a truck. You made a couple statements that prove you understand (below). You and Green stripe (sorry bud, I can't recall your name) seem to get it. I broke down some responses below.
Quote:
Originally Posted by DieselDoctor
but in a semi truck tandem axle with the power divider unlocked, doesn't the wheel with the least traction see the power output due the the differential in the power divider?
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[QUOTE=Green stripe wide frame;434518]In a semi with the power divider locked you get power
being transfered to both axles but still have open differentials, just like a 4 wheel drive pick up locked in 4 wheel. With it locked in, you have it right it goes to the wheel with the resistance. [QUOTE]
Yes, this is correct. Green stripe answered it very well!
Now, for discussion and explanation purposes, an all wheel drive vehicle (AWD) has a transfer case just like a pickup would and it has a differential between the front and rear axles just like a power divider in a truck axle. The power divider is just that, a differential, between the two axles. (Further explanation for other readers.) Yes, on a tandem drive (twin screw as it's called) if one wheel loses traction, all power goes to that wheel and it spins. If you lock in the power divider, then it locks the differential between the two axles and equal power will go to both axles. So, if one wheel spins, the differential in that axle will supply power to the slipping wheel, but power will still be supplied to the axle with no slip and you can drive out. If you have a case of two wheels spinning (one on each axle) then the power divider lock will have no effect. You will also have to lock the differentials to get power going to all 4 drive wheels equally. I know you guys covered it, and understand, but I just wanted to go into it a little farther.
Quote:
Originally Posted by DieselDoctor
If the power divider is locked in and the rear centers are no spins, then all four drive correct?
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Yes, but even with the divider unlocked, all four drive equally unless you are 1.) turning. Or 2.) you have wheel spin.
Just to reiterate, with the divider locked, it supplies power (solid shaft) to both axles equally. Only reason not to have it locked all the time is so that it steers easier.
Quote:
Originally Posted by DieselDoctor
So in the case of this project, because the back rear axle is positively driven by the shaft passing directly thru the front rear, wouldn't the back one still be driving even if the front one was totally off the ground and spinning?
There is no lost motion or disconnect of the driveshaft as it passes thru the front hydro.
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Yes. That is absolutely correct. One axle can come completely off the ground, and as long as both tires on the opposite axle are still in solid contact, then it will still drive.
Quote:
Originally Posted by DieselDoctor
Even so, with no suspension at least one or two of the four rear tires will most likely be off the ground most of the time on rough terrain. I think it's a cool project too and like you would like to see the OP succeed.
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Quote:
Originally Posted by Green stripe wide frame
You'll need three drive wheels on the ground for this thing to move. Unless you put a spool in one carrier.
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Yes, both of these are correct. 3 wheels will need to be in contact, OR one whole axle. So, if the correct 2 come off the ground, it will still drive. More on this below.
Now, it wouldn't seem that this would really be an issue. But believe me, go off road with a twin screw truck, and even with suspension, and a loaded trailer, it doesn't take much to get one wheel on each axle to lose traction. Kick the power divider in and it gets much better, but even then, it still isn't very hard to lose traction. Example: I was backing a semi into my driveway at home last fall. Just backing off a gravel road, into a gravel drive that goes just slightly uphill, and lost traction altogether. Once a wheel spun, it dug a hole, and wham! Stuck. Power divider in, (truck doesn't have diff lock) and it still couldn't do it. I finally got the truck to move forward just enough, that I could pull forward and go back again (a little faster this time) and got into the drive. But it really is amazing how with a big truck, with suspension, and plenty of weight, it will spin out and your done. That's why I'm so certain that this thing will need at least some sort of flex between the two axles. One tire on it goes up on a hill/bump whatever, it can pull traction from two wheels pretty quick. Now, if the truck had ag tires on it.... maybe it would have been fine. Again.... with those ATV tires, there may just be enough wheel flex to make it work. I haven't been around JD Gators much, but they are an ATV with tandem drives. I do not know what type of drive system they have, but they seem to work pretty well. Also, Terra Gator makes a 5 wheel sprayer/spreader that has a tandem drive rear. It doesn't have any suspension on the rear, but it has floater tires which have a lot of give. I would also assume since it's an off road vehicle, that it has both a divider lock, and diff lock.