Scaffolding poles + old VW bits + Rotary engine....
Discussion
PhillipM said:
The only problem is they still go for a fair price, and obviously the tranmission is no good for a longitudinal install without locking off the 4wd system. And I don't like turbos 
The other issue is we need to keep the torque output down and hence the shock loadings through the shafts. So.... lots of revs instead.
Gearings not too bad, we have had to be careful with selecting boxes and diffs just because, as you say, it can knock you well out of the useable range on the 'box, but it's looking pretty good at the minute, we end up geared a touch no the low side (flat chat at about 125mph), but there's an option to go longer with the supercharged car which I think would pull it (155)
Stop typing and get building then - I want to see how it works The other issue is we need to keep the torque output down and hence the shock loadings through the shafts. So.... lots of revs instead.
Gearings not too bad, we have had to be careful with selecting boxes and diffs just because, as you say, it can knock you well out of the useable range on the 'box, but it's looking pretty good at the minute, we end up geared a touch no the low side (flat chat at about 125mph), but there's an option to go longer with the supercharged car which I think would pull it (155)
rhinochopig said:
Watchman said:
Sorry if I sound naive... but can't you use any FWD setup by installing the differentials upside down?
What you could possibly do is to run a transverse engine and box longitudinally and use the half shafts to drive the diffs at each end. With clever packaging of ancillaries over the gearbox you could probably even out the lopsided weight distribution too. The co-driver might moan about having his gonads friction heated by a rotating prop-shaft but everyone has to suffer for their art. Goes off to see whether anyone's ever tried it
Edited by rhinochopig on Thursday 29th January 10:58
I've got an idea for a "hydraulic" hang on front axle, because for off road racing you really only need to be 4wd at low speed, either when climbing through/across/over large obstacles, or to get out of low speed corners smartly. Basically, take a pokey engine (2.3turbo 4cyl with ALS to keep mass down) std transaxle style transmisison to drive rear axle. Using a variable displacement pump hung off the front pulley of the engine with electronic control of that displacement to give you "speed" control on the front axle, and hence an active torque split..........
Max_Torque said:
rhinochopig said:
Watchman said:
Sorry if I sound naive... but can't you use any FWD setup by installing the differentials upside down?
What you could possibly do is to run a transverse engine and box longitudinally and use the half shafts to drive the diffs at each end. With clever packaging of ancillaries over the gearbox you could probably even out the lopsided weight distribution too. The co-driver might moan about having his gonads friction heated by a rotating prop-shaft but everyone has to suffer for their art. Goes off to see whether anyone's ever tried it
Edited by rhinochopig on Thursday 29th January 10:58
I've got an idea for a "hydraulic" hang on front axle, because for off road racing you really only need to be 4wd at low speed, either when climbing through/across/over large obstacles, or to get out of low speed corners smartly. Basically, take a pokey engine (2.3turbo 4cyl with ALS to keep mass down) std transaxle style transmisison to drive rear axle. Using a variable displacement pump hung off the front pulley of the engine with electronic control of that displacement to give you "speed" control on the front axle, and hence an active torque split..........
To be honest, I was wondering whether to do something similar with the 2wd Max, albeit using a 20kw motor up front driving through a pair off shafts off a swappable lithium battery pack - either engaged via a switch on the dash or via speed sensors, just to give it 4wd out of corners/in the s
te and then back to 2wd again.
te and then back to 2wd again.PhillipM said:
To be honest, I was wondering whether to do something similar with the 2wd Max, albeit using a 20kw motor up front driving through a pair off shafts off a swappable lithium battery pack - either engaged via a switch on the dash or via speed sensors, just to give it 4wd out of corners/in the ste and then back to 2wd again.
^^^This is a "technically" better solution these days.te and then back to 2wd again.It's also "technically speaking" going to be bl**dy expensive.......
I think you'd want a little bit more than 20kW as that is just 895N tractive effort at 50mph (0.065g on a 1400kg vehicle). Bumping that to 50kW, would be 2237N / 0.16g at 50mph)
Speed tractive effort Front axle Accel
[mph] [m/s] [N] Kg G
5 2.23 22374.1 2281.6 1.630
10 4.47 11187.1 1140.8 0.815
15 6.70 7458.0 760.5 0.543
20 8.94 5593.5 570.4 0.407
25 11.17 4474.8 456.3 0.326
30 13.41 3729.0 380.3 0.272
35 15.64 3196.3 325.9 0.233
40 17.88 2796.8 285.2 0.204
45 20.11 2486.0 253.5 0.181
50 22.35 2237.4 228.2 0.163
55 24.58 2034.0 207.4 0.148
60 26.82 1864.5 190.1 0.136
65 29.05 1721.1 175.5 0.125
70 31.29 1598.2 163.0 0.116
Yeah, weight isn't an issue, I can put 20kw through a pair of sprag clutches so no diff to worry about, but it still needs 4 new CV's buying, and the motor and battery pack wasn't cheap when I toted up last..
Not too worried about it being 20kw Max, since it's only when the cars ploughing through peat and bog at 5-10mph that it really struggles, and on the way out of 2nd gear corners so 20-25mph ish, at 50mph she's got some traction from somewhere and going anyway
Plus the extra acceleration is going to help the rear grip, and unless there's another car on a rope behind it's not 1400kg
Was an idle thought a long while back mind, but I don't think it'll happen, too many pennies.
Not too worried about it being 20kw Max, since it's only when the cars ploughing through peat and bog at 5-10mph that it really struggles, and on the way out of 2nd gear corners so 20-25mph ish, at 50mph she's got some traction from somewhere and going anyway
Plus the extra acceleration is going to help the rear grip, and unless there's another car on a rope behind it's not 1400kg
Was an idle thought a long while back mind, but I don't think it'll happen, too many pennies.
Edited by PhillipM on Thursday 29th January 23:04
Why not just take a VW/audi or Subaru 4wd box and mod the rear drive of the gear box to run a prop forward. Should be a lot easier than electric or hydraulic stuff. Would be off the self components with a load if engine choices (including v8s or even a v10!!!!) 
Also if you use the audi/VW stuff could you not use the clutch system they use on the rear wheels for the front?
Also if you use the audi/VW stuff could you not use the clutch system they use on the rear wheels for the front?
chuntington101 said:
Why not just take a VW/audi or Subaru 4wd box and mod the rear drive of the gear box to run a prop forward. Should be a lot easier than electric or hydraulic stuff. Would be off the self components with a load if engine choices (including v8s or even a v10!!!!)
Also if you use the audi/VW stuff could you not use the clutch system they use on the rear wheels for the front?
The problem with the scooby box is that it will have the engine hanging right out the back if you put it all in backwards, and if you put it in fowards, then you have to reverse the direction of the prop output and get it forwards past the engine.Also if you use the audi/VW stuff could you not use the clutch system they use on the rear wheels for the front?
Another issue is that 4wd gear boxes are often mechically biased to drive one set of outputs more than the other and if you put it in "backwards" that messes things up.
Using a haldex IS an interesting idea, but it comes down to how you get the drive to it.
Max_Torque said:
chuntington101 said:
Why not just take a VW/audi or Subaru 4wd box and mod the rear drive of the gear box to run a prop forward. Should be a lot easier than electric or hydraulic stuff. Would be off the self components with a load if engine choices (including v8s or even a v10!!!!)
Also if you use the audi/VW stuff could you not use the clutch system they use on the rear wheels for the front?
The problem with the scooby box is that it will have the engine hanging right out the back if you put it all in backwards, and if you put it in fowards, then you have to reverse the direction of the prop output and get it forwards past the engine.Also if you use the audi/VW stuff could you not use the clutch system they use on the rear wheels for the front?
Another issue is that 4wd gear boxes are often mechically biased to drive one set of outputs more than the other and if you put it in "backwards" that messes things up.
Using a haldex IS an interesting idea, but it comes down to how you get the drive to it.
Still have the issue of getting the propshaft past the engine though then, it's a bit of a pain in the arse, those V6 cars we made, we had to run the prop backwards from the Sadev boxes, and not wanting to compromise on lifting the engine to accomdate the prop, we actually ran it through the engine sump with it offset just enough to miss the crankshaft on one side and the oil pickup on the other - was a pain in the arse to be honest.
PhillipM said:
Still have the issue of getting the propshaft past the engine though then, it's a bit of a pain in the arse, those V6 cars we made, we had to run the prop backwards from the Sadev boxes, and not wanting to compromise on lifting the engine to accomdate the prop, we actually ran it through the engine sump with it offset just enough to miss the crankshaft on one side and the oil pickup on the other - was a pain in the arse to be honest.
Have you looked at the setup BMW did in the AWD 3 series in the 1980s? Mercedes used a very similar system on the E-class at the same time. It was a transfer case with a viscous centre diff that bolted to the gearbox tail. That would probably work a bit better - it's fully mechanical on the BMW as well, and has output shafts at both ends rather than an integrated diff like the Subaru box. Drop boxes are easy to come by but you still need to get the shaft past the engine, either you end up putting dog legs in and joints and then compromise both the shock load load the shaft will absorb and some power, or you have to offset the engine and/or diffs - the latter isn't really feasible given the amount of travel required.
It's easy with a FWD box and longitudinal engine, or transaxle and a transverse engine, but it does mean a lot more work finding suitable ratios and the packaging becomes difficult - but, I think it's worth a shot, I've a few tricks up my sleeve with the current buggy yet to get the cooling requirements and sizes down which we'll try over this season, if they work, it makes fitting everything in the 4wd much easier.
It's easy with a FWD box and longitudinal engine, or transaxle and a transverse engine, but it does mean a lot more work finding suitable ratios and the packaging becomes difficult - but, I think it's worth a shot, I've a few tricks up my sleeve with the current buggy yet to get the cooling requirements and sizes down which we'll try over this season, if they work, it makes fitting everything in the 4wd much easier.
Edited by PhillipM on Monday 2nd February 01:47
I think I understand the Subaru "problem" now.
I assume the front and centre diffs are inside the gearbox so unless you spin the crank the other way, you can't really turn the whole assembly around and use it mid-mounted. And even then, if the centre diff is a viscous coupler, it might not work in reverse.
I assume the front and centre diffs are inside the gearbox so unless you spin the crank the other way, you can't really turn the whole assembly around and use it mid-mounted. And even then, if the centre diff is a viscous coupler, it might not work in reverse.
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