I was watching the history of monster trucks a few days ago, and on the show they said that in the old days they would break axles left and right with those huge tires... then they started using a planetary gear axle system that puts way less stress on the axle and made it easier for the tires to turn with less needed power.



so why hasn't anyone done this on a regular rockcrawler? it seems like this kind of system would eliminate the need for dual cases/low gears.

any thoughts?

 

Portal (gear reduction) axles are not uncommon in rock crawling. Planetary axles like Rockwells, UniMog, and Volvo are out there on the trails...

Below is a link to the Volvo donor vehicle.

http://www.volvoadventures.com/Laplander_C303spec.html

For a Toy, the Volvo or Mog axles offer the best clearance, and aren't a lot wider than stock axles. A 2-1/2 ton Rockwell will make your rig almost impossible to roll due to the enourmous weight. To me, the big draw back to a Rockwell is it's width...

 

ahh.. ok.. I didn't realize that was the way portal axles worked...

it's seems like they could make some sort of "bolt on" planetary for any solid axle though...

 

there was a thread the otehr day about this... it was for a bolton kit for a jeep axle d60..... also that type of drive is what half the winches use as a drive system

 

here it is https://www.yotatech.com/forums/show...ight=jeep+axle

 

well, how about that... somebody's already doing it... too bad they cost $8000

 

hey now... now the messenger

 

Has anyone tried a 4wheel hydraulic system? Unlimited ground clearance, no need for transmission, unlimited crawl ratio.....might be heavy though.

 

I believe hydraulic isn't street legal so the only ones who would build that up are hardcore rockcrawlers...but then I also believe hydraulic isn't legal in the competitions either.

Anybody have links to how a rockwell works. I've been trying to figure that out forever now. Diagrams would be nice. I found a jpmagazine article, but that didn't help much.

 

I'm not certain about Volvo, but Unimog axles are NOT planetary. They simply have a set of normal gears for ~2:1 reduction at each end. On Rockwells other than the odd input arrangement at the third member I've seen no sign of any additional gearing in them. Anyone is welcome to prove me wrong with pictures...



Oh, and don't forget about the HMMV, it also has hub reduction gearing.

 

Very simple. Unless it can be found in a production vehicle in bountiful numbers, it won't make it into your average rig.

 

True, a Rockwell isn't a planetary reduction, but IMO it fits into the same class by virtue of it's double reduction. The R/P gearset drives an intermediate gear that, in turn, drives the bull gear. With a final ratio of 6.71:1, it's perfect for tires above 40" dia.