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4wd update with question
RallyHarry - 31/8/05 at 09:28 PM

Hi Guys.

Still trying to get my head around using hydraulics (from parker) to get power to the front wheels and the supercharger, almost there ...


But I have to get an answer to another question before I can put it to rest:
Would it be feasable to use a chain running from the back ( rear axle) to the front diff, the distans would be approx. 2.5 meters (chain length 5+ meters) running in a central tunnel with some type of chain guide.

Is the distance to long ?

DP (of dpcars.net) runs a chain in a plastic "jig" but it's far shorter.

Cheers

Liam - 31/8/05 at 10:37 PM

Wow the hydraulic drive sounds like a cool project. A number of 2WD motorbikes have been produced this way, inlcluding an R1 so it must have some potential!

I cant imagine a chain from front to back axles would be a good idea as you will allow no speed differential between the front and back. Have you considered flipping the engine 90 degrees and chain driving a centre diff. The rear output could couple straight to the rear diff with a propshaft to the front.

Liam

mark chandler - 31/8/05 at 10:42 PM

Suzuki sj jeeps have a nice little transfer box thats prop driven from the primary gearbox, how about dropping one of those in and keeping it simple ?

Liam - 31/8/05 at 10:43 PM

Like this... Rescued attachment 4x4bec.JPG
Rescued attachment 4x4bec.JPG

Liam - 31/8/05 at 10:50 PM

And of course the twin engined extension. I'd love to build a car with this layout in the future... Rescued attachment 4x4twinbec.JPG
Rescued attachment 4x4twinbec.JPG

Liam - 31/8/05 at 10:52 PM

quote:
Originally posted by mark chandler
Suzuki sj jeeps have a nice little transfer box thats prop driven from the primary gearbox, how about dropping one of those in and keeping it simple ?


I'd expect that to break if you wanted to transmit actual power through it . But maybe it'd work? You'd still have the problem of the front and rear axles locked together with 4WD engaged. Maybe OK for an off-road middy bec...

Liam

crbrlfrost - 1/9/05 at 02:22 AM

I would have a hard time recommending running a chain that long. I would imagine rather unpleasant reactions due to slack take-up, quick throttles inputs, and of course the possibility of a breakage. Seems like there should be a better way, but I don't know the layout you're attempting to use. Best of luck!

kb58 - 1/9/05 at 05:19 AM

quote:
Originally posted by Liam
And of course the twin engined extension. I'd love to build a car with this layout in the future...


The problem is the final output from the engine sprocket is already geared down, expecting to drive a tire to a max speed of, oh, 150mph. This with a sprocket gear ratio of ??? (I'm not sure). With your approach you've introduced two gear reductions. First is the sprocket-to-sprocket on the center diff which give a reduction of perhaps 5:1. Then it runs through *another* set of gears in the diffs of say, 3.5:1. This may very well gear the engine down way too much, ending up with a 50mph top speed. You'll need to know what the stock bike sprocket reduction ratio is first, then figure out what you have to do with your two ratios to make it work out.

Don't feel bad, I only know this because I too thought it would be a great project myself until I ran into this issue. It's doable, but at perhaps too high a price to deal with the gearing issue. I do like the approach though because it essentially gives you a high-reving V8 without the expense of actually building a V8 block for the engines.


[Edited on 9/1/05 by kb58]

RallyHarry - 1/9/05 at 07:57 AM

So if no better ideas, I'll put the chain derivative in the bin then ... ( or on the shelf until something smart comes up:-)

A great benefit with hydraulic motor driving the front diff is that you can regulate how much power you want to the front with an electronic valve, the bigger difference between the outputshaft RPM and the drivaxel RPM (spin) the more power is moved to the front, from about 30% to 50%

The penalty is cost and weight

Cheers

kreb - 1/9/05 at 06:44 PM

I'm trying to figure the basic problem with Liam's arangement (Besides weight). If you have clutch-type differentials at either end, what would be wrong with it?

I'm not so sure about the BEC, but it might work well with something like a subbie.

Can you straighten this fellow (me) out?

silex - 2/9/05 at 06:47 PM

Not wanting to put a dampner on your idea - I know first hand this type of system can work well, but you may want to rethink using mechanical drive to the front rather than hydraulic.

If you are doing this because its of technical interest, I'm sure you will have alot of fun, but the performance will never quite match that of mechanical drive due to the additional losses in the system you will have.

Using the EPC-valve (Electronic Position Control) you basicaly effect the displacement of the pistons in the pump which have the effect of producing high torque/lower speed at maximum displacement and lower torque/high speed at minimum displacement and a mixture of everything in between. Parker would provide you with this output curve.
The engine revs will also effect the speed as well as the EPC valve as the pump would be driven from the engine (variable revs = variable flow).

You would need the following bare minimum for your system...

1. Hyd Pump
2. Hyd Motor
3. Oil Tank
4. Oil Cooler (the oil will get VERY hot)
5. Pressure regulator
6. A bunch of hoses

As well as finding somwhere for your hydraulic tank, you do need to think about the oil cooler - this will probably be about the same size as the cars radiator.

You will more than likely have to run with a car engine rather than a bike - hydraulic drives tend to crave engine torque, it would generaly kill a bike engine.

Also - the cost, this will not come cheap if you but new parts.