Post by Admin on Oct 15, 2007 11:27:18 GMT -4
I was recently asked how to plumb front and rear hydraulic steering so I thought I would post it here just incase anybody else was wondering. There are a couple of differant ways to go.
1 - Individual Control
This system uses 2 independant controls, 1 for each axle, so the the axles can be operated at the same time. The front axle would be controled by the Orbital valve like normal. The rear axle would be controlled via a 3 position toggle switch. This setup would also be similar to a system set up like mine to run a hydraulic winch instead of rear steer.
Parts
Pump - I recommend a P style saginaw pump with a remote reservoir. They are very common and easy to find. They are compact and easy to mount. The remote reservoir allows you to increase fluid storage "as needed". You will notice that in the plumbing diagram only one of the return ports on the pump is being used, the unused port can just be blocked off.
Warning - attached reservoir pumps may be sufficent for single axle hydraulic steering but in most cases will have insufficent oil capacity to support rear steer as well.
Reservoir - I would reccommend finding a scrap 5 ton or another heavy truck and robbing a reservoir from one of these. They are expensive new ($300) but just about every scrap yard has some form of heavy truck or bus in it. My reservoir is from a 1997 Freightliner.
Most common heavy truck reservoirs hold almost 1 gallon of fluid, have both supply & return ports, and have built in filters which can be found fairly cheap at any PFT.
Orbital Valve - You will want to use and open center power beyond type orbital valve. Also known as a 5 port orbital valve. This type orbital will divert any flow not being used by the front steer axle on to another use. Use of this type of orbital means that the rear steer will not be able to affect the front axle because the orbital will give the front steering priority and give the rear steering just whats left over. what this means is if your are cranking your front steering from lock to lock then very little flow will be directed to the rear. but vise versa if your not turning the steering wheel at all then full flow will be directed to the rear.
Warning - any device used after the orbital or supplied by the Power Beyond port will have to be of an open center design.
Control Valve - I reccomend the use of an electronicly operated 3 position control valve. An example would be Princess Auto part # 8046688 . They retail for $229.99. You could also use a manual control valve, but I don't reccommend this because it means running all the hoses into the cab and having a big control lever instead of a nice compact toggle switch.
Cooler - This is not really always nessecary, but every little bit helps. I bought a Mr. Transmission 24 000 lbs GVW transmission cooler at Canadian Tire and have been using that for the last year. It works good for me.
1 - Individual Control
This system uses 2 independant controls, 1 for each axle, so the the axles can be operated at the same time. The front axle would be controled by the Orbital valve like normal. The rear axle would be controlled via a 3 position toggle switch. This setup would also be similar to a system set up like mine to run a hydraulic winch instead of rear steer.
Parts
Pump - I recommend a P style saginaw pump with a remote reservoir. They are very common and easy to find. They are compact and easy to mount. The remote reservoir allows you to increase fluid storage "as needed". You will notice that in the plumbing diagram only one of the return ports on the pump is being used, the unused port can just be blocked off.
Warning - attached reservoir pumps may be sufficent for single axle hydraulic steering but in most cases will have insufficent oil capacity to support rear steer as well.
Reservoir - I would reccommend finding a scrap 5 ton or another heavy truck and robbing a reservoir from one of these. They are expensive new ($300) but just about every scrap yard has some form of heavy truck or bus in it. My reservoir is from a 1997 Freightliner.
Most common heavy truck reservoirs hold almost 1 gallon of fluid, have both supply & return ports, and have built in filters which can be found fairly cheap at any PFT.
Orbital Valve - You will want to use and open center power beyond type orbital valve. Also known as a 5 port orbital valve. This type orbital will divert any flow not being used by the front steer axle on to another use. Use of this type of orbital means that the rear steer will not be able to affect the front axle because the orbital will give the front steering priority and give the rear steering just whats left over. what this means is if your are cranking your front steering from lock to lock then very little flow will be directed to the rear. but vise versa if your not turning the steering wheel at all then full flow will be directed to the rear.
Warning - any device used after the orbital or supplied by the Power Beyond port will have to be of an open center design.
Control Valve - I reccomend the use of an electronicly operated 3 position control valve. An example would be Princess Auto part # 8046688 . They retail for $229.99. You could also use a manual control valve, but I don't reccommend this because it means running all the hoses into the cab and having a big control lever instead of a nice compact toggle switch.
Cooler - This is not really always nessecary, but every little bit helps. I bought a Mr. Transmission 24 000 lbs GVW transmission cooler at Canadian Tire and have been using that for the last year. It works good for me.