Hi Larry, I tell you what I had in mind for the hydraulic circuit. I probably use a power steering pump (vane pump), I've checked these out and some them, especially the big diesel pickup's have a decent P/S pump in them. A good one will pump about 4 gpm @ 1,000 to 1500 psi., you can get the ones that use a remote tank and just swap the tank out for something that has a little more volume. As we know these P/S pumps are almost bulletproof and low cost. I would drive the pump from the other side of the crankshaft on my engine, the same way some of the external alternator kits mount. Another way is I've seen one of the members using a v-belt pulley (sheave) on the clutch side as well for an external alternator, either way would work.
I've already picked out a nice small hydraulic motor that would mount in the area of the brake calipers, picking up the holes for a bracket that would house the hyd. motor. For the other sprocket I would remove one of the dual rotors for the disc brakes, and use the bolt pattern to pickup the sprocket, then a short loop of chain, up to the motor spocket, and that should do it. I would pick a sprocket ratio that would come close to the rpm. I need to match to the rear tire. This is where a mech. tach, and a pressure compensated flow control valve would do the fine rpm tuning. This method should get it pretty close. I would just hard plumb it with some small flex lines. For forward and reverse I would use a 12v directional control valve with an open motor spool, with a detent position for float this will allow me to coast, as I would probably only engage the front wheel when needed. I'm using the solenoid type instead of the manual type because I'm using a 12v linear actuator to shift from forward to reverse on the transaxle, instead of running long cables to the back. So whenever I would shift the transaxle into forward or reverse the 12v solenoid would shift the spool in the DCV.
6x6, thanks again for your interest. Check my response to Larry for the hydraulic details, which is simplier I think that going mechanically (I think).
Hey Plott, howsit going? Yeah just waiting for spring, to get back on this projict. I just got back from the waterjet guys with my grousers for the tracks. Drop by when you get a chance.