Why no 4 wheel drive on roads?
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RoostersGarage
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After clocking close to 200,000 miles in an AWD Subaru with the silicon drive technology, I can say that was a terrible design. Apply too much torque and the viscous coupling locks up, enabling 4 wheel drifts. When it got cold, it didn't work as well as when it was hot outside and I really wanted it to work better in the winter when driving on ice. I went a lot of places in that car and a lot of times didn't have to think about the road condition. However, I was in a loaner automatic while mine was in the shop and their automatic system was 100 times better than the old faithful silicon drive system. The automatic/electronic version was better in every way, except when something broke. I even noticed a power difference between the two and the automatic/electronic system seemed to have more power. I can only imagine there were mechanical losses in those couplers.
That's my point about tractors. They are already expensive enough, and for the average buyer the old faithful mechanic 4wd system is very good. When you're looking at a 35 hp tractor or less, there's not much power to lose. Not to mention those tractors are bought by homeowners and everything is already expensive enough. I can absolutely see a need for a full time 4wd system in big tractors that aren't trailered from one field to the next, or haul the crop to the market on the roads.
That's my point about tractors. They are already expensive enough, and for the average buyer the old faithful mechanic 4wd system is very good. When you're looking at a 35 hp tractor or less, there's not much power to lose. Not to mention those tractors are bought by homeowners and everything is already expensive enough. I can absolutely see a need for a full time 4wd system in big tractors that aren't trailered from one field to the next, or haul the crop to the market on the roads.
LouNY
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How about small trucks and tractors, that is a drivetrain that I have wished for for a long time.
A decent sized battery pak, a small diesel tuned for economy at a couple of different rpm's driving a generator
to power the vehicle and recharge the battery.
It could supply the AC power and the vehicle heat.
Jims1025R
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One other thing to remember, on a hard surface, if you're in 4WD, too fast into a corner, and you come off the throttle quickly and/or apply [rear wheel] brakes, the front wheel is now providing braking through the drivetrain, which you did not intend. The now braking front wheel won't steer as well, and tends to want to induce a rollover in a turn when slowing.
PILOON
Super Star Member
You will have no doubt noticed that most tractors have smaller wheels up front.
Being smaller they will wear faster than the rears and that's why they usually are slightly oversized than if a perfect match, usually by about 5%.
They refer to this as 'lead'. i.e., they lead by 5%.
I would assume when fronts are 'near bald' there is no longer any binding.
To have a true full time 4 wheel drive you'd need all 4 wheels to be the exact same size.
Being smaller they will wear faster than the rears and that's why they usually are slightly oversized than if a perfect match, usually by about 5%.
They refer to this as 'lead'. i.e., they lead by 5%.
I would assume when fronts are 'near bald' there is no longer any binding.
To have a true full time 4 wheel drive you'd need all 4 wheels to be the exact same size.
RoostersGarage
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Always!! That means when mud is stuck on the backs but not the fronts, the full time 4wd system would be fighting this difference and have to allow slippage somewhere.
Agvg
Elite Member
Nissan e-power is close, no diesel but all electric drive train with a gas engine and battery.
ning
Elite Member
They could all 4 be different sizes, but you'd get a lot of wear in the differentials unless you had gearing to compensate for the different wheel sizes.
Note that I'm not saying it's reasonable to do what I stated.
DieselBound
Elite Member
I was advocating diesel-electric way back when Priuses were coming on the scene. But as far as for a tractor... Whereas a transportation vehicle can be viewed as operating two-dimensionally a tractor would be operating three-dimensionally.
How to load balance across travel and loader work (PTO operations tend to fairly constant) would be tricky. Maintaining sense of and actual fluidity might be tough.
Electrical stuff can be a lot more sensitive to harsh environments than flat-out metal.
How to load balance across travel and loader work (PTO operations tend to fairly constant) would be tricky. Maintaining sense of and actual fluidity might be tough.
Electrical stuff can be a lot more sensitive to harsh environments than flat-out metal.
LouNY
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Big mine and off road equipment has been that way for years,
Agvg
Elite Member
Much easier to regulate an electric motor.
DieselBound
Elite Member
I look at huge tires like that and get anxieties over a puncture!
DieselBound
Elite Member
I agree, but I was mostly commenting on what Lou had said:
A decent sized battery pak, a small diesel tuned for economy at a couple of different rpm's driving a generator
Hybrids, other than diesel-electric trains, use batteries. That means storage, buffer storage. How to design/spec for a lot of loader work? Would seem that more batteries would have to be used, which then starts pushing up against the size available for the diesel engine. Regulation is one thing, having enough power to meet the various tasks, and do so fluidly, is another...
Agvg
Elite Member
If your genset is way to small vs the electric drivetrain you will have problems, on a tractor a hybrid will not generate to much power, except maybe with extensive loader use or road use, here in Europe where tractors is constant used on public roads you have a potential for energy preservation, if this potential is big enough to make it economical viable is a another question.
DieselBound
Elite Member
Most tractors on this site aren't roaded. I've roaded mine, but sparingly. And some folks around me do also. But all in all it doesn't constitute enough of the overall demand/function that added complications from hyrbidization is going to offset.
If you look at large corporate operations the move is always toward larger (for volume) an more specific machinery. Refer to the picture Lou posted.
Agvg
Elite Member
The road use if tractors are a very clear difference between US and Europe. Here a tractor with a trailer behind almost the default way to transport things if the distance is not to long.
Don't know how many rigs like the picture I meet on a day but it's quite a few.
DieselBound
Elite Member
Yup. Definitely NOT a CUT! 
We have various big rigs running equipment to/from various sites, but material is mostly hauled with a truck: manure trailers are run behind tractors, though. People around here tend to keep their big tractors in the soil and working.
We have various big rigs running equipment to/from various sites, but material is mostly hauled with a truck: manure trailers are run behind tractors, though. People around here tend to keep their big tractors in the soil and working.
apologize for the obvious, to relieve my '92 4x4 toyota pu switching back to 2wd, i come to a full stop, reverse & it will usually do the trick
on the tractor, either by reversing, or by slightly lifting the ft end w/FEL will disengage a stuck 4wd. thinking my limited slip ft end also helps w/the 4wd binding. love the higher end M series...
on the tractor, either by reversing, or by slightly lifting the ft end w/FEL will disengage a stuck 4wd. thinking my limited slip ft end also helps w/the 4wd binding. love the higher end M series...
