another way to underdrive(crawler)

[uninformed]

apparently the icelandic guys are running a engine driven hydraulic pump, a transfer case pto with hydraulic motor. putting the gear box in nuetral and driving through the transfer case.
any thoughts?????
serg

[daddylonglegs]

I remember reading in ''LandRover the unbeatable 4x4'' ( I can barely restrain myself ). where Rover special progects division did a similar thing way back in the late 1950's when they converted a few series 1's to airfield snow blowers.
Bill.

[ISUZUROVER]

Interesting (but probably expensive) idea - to do a lot of driving using this in tropical weather you would need very good cooling for the hydraulic system though.

[Dave J]

Lots of cooling, not necessarily, there are lots of hydraulic systems which work pretty hard with only a small reservoir and no cooling. You can work out how big a reservoir you need but i suspect it wouldn't be over the top (say 20L to 40L at an absolute stab in the dark).

Other problems would be oil starvation to the pump, would almost need a small elec booster pump and a surge tank to cope with extreme angles rocking etc (could run this through a mini radiator to get your cooling). Also a hydraulic motor won't over-run like a petrol or diesel will as it's speed is controlled by flow of oil through control valves. This could be a good thing though, I just think it could be a problem when you roll over a large rock and get "compression lockup" on the way down.

Oh yeah, and decent hydraulic motors are expensive.

Some thoughts. I think it is a great idea, you could have fingertip joystick-like instantly reversible drive. Why not go a step further and put a hydraulic motor onto each diff. No more driveshafts limiting travel, or pinion angles to worry about! Strictly crawling only rig though.

Or one on each wheel, now I am just going over the top.

dj

[Bush65]

apparently the icelandic guys are running a engine driven hydraulic pump, a transfer case pto with hydraulic motor. putting the gear box in nuetral and driving through the transfer case.
any thoughts?????
serg

What you are describing is a common hydrostatic transmission. With a variable volume (for different speeds), overcentre (for reverse direction) pump there would be no need of the gearbox.

These are generally closed loop systems (pump out to motor in, motor out to pump in) with a small reservoir and make-up pump to replenish internal leakage.

With a variable volume pump the heat generation is low - maybe more efficient than a conventional auto transmission!

[hook]

Maxi Drive.

http://www.4wdworld.com.au/products/max ... icunit.htm

mal told me "where the P.T.O. shafts cannot be fitted to power winches" due to the stearing being in the way with left hand drive.