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  1. #1

    Orbital Steering and rear steering


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    Can some one explain to me how orbital steering and rear steering works, I just finshed my chassis class at school, tearing down,and rebuilding, the whole front suspension and steering of a tractor. I would like to get an idea each wo, I know a little on how the rear steering works, but have no idea how the front, orbital, steering works.

  2. #2
    its pretty much like the rear, except the orbital is what is directing fluid, and the pump is ran off the engine. how the orbital works, is beyond me.
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  3. #3
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    An orbital valve is a special valve which controls both fluid flow direction, but also the flow rate. A hydraulic steering system is very complicated and takes a lot of calculations to design to work good. You cannot just bolt random parts together. You need to select steering rams based on the weight on the axle, backspacing and width of the tires, effective radius of the steering mount on the knuckle in order to figure out what size cylinders you need. Next you have to decide what rate you want to be able to turn the wheel and how many turns from lock to lock, if you don't you can go faster than the steering system and it will lock the steering on you if you do. This will then let you know what components you can and can't buy. Orbital hydraulic steering is very important and also complicated, I suggest you look into it a lot before designing.
    "Far better is it to dare mighty things, to win glorious triumphs, even though checkered by failure... than to rank with those poor spirits who neither enjoy nor suffer much, because they live in a gray twilight that knows not victory nor defeat." -Teddy Roosevelt

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  4. #4
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    As stated above, with the front steering, the orbital controls the fluid flow that pushes the rams that, in turn, steer the wheels. Think of the orbital as a hydraulic pump only it is spun with the steering wheel instead of an electric motor. As you steer the wheel, you spin the orbital and it pumps fluid from one side of the rams to the other. Now, trying to do this by hand would take alot of strength, so the orbital unit has a power assist very similar to the power assist steering on a light truck or car. This power assist has a separate pump, driven by the engine that routes power steering fluid through the orbital. In fact many Monster Trucks actually utilize steering pumps from automobiles and light trucks, with minor modifications. The pressure in the power steering circuit provides additional force to spin the orbital, making it possible for the Driver to turn the steering wheel with minimal effort.

    With the rear steering, their is an electric hydraulic pump that pumps the fluid. This pump is controlled electronically that combines input from the Driver and sensors mounted on the rear steering arms. A toggle switch operated by the driver activates the hydraulic pump to push fluid in either direction, depending on which way the Driver pushes the switch. When the driver releases the switch, the electronic controls take over and use inputs from the sensors on the steering rams to steer the rear wheels back to center. This is the "Auto Center" function that most people refer to. Some Drivers have their Auto Center function activated by a second button, separate from the directional toggle switch. This gives the Driver control of when the auto center function takes over so that they can steer the rear wheels to a certain angle and keep them there until they choose for them to center.
    Monster Truck fan since 1980.
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  5. #5
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    Good explanation Scott, I didn't have the patience to sit down and type all that out. Christian
    "Far better is it to dare mighty things, to win glorious triumphs, even though checkered by failure... than to rank with those poor spirits who neither enjoy nor suffer much, because they live in a gray twilight that knows not victory nor defeat." -Teddy Roosevelt

    Christian Riedel
    Crew Chief-Stinger and Boogey Van
    Mechanical Engineer
    Admin of Monster Truck Fab forum

  6. #6
    Thanks for the info guys, though I still have some questions on the orbital steering. How is the steering wheel connected to the orbital valve, through hoses or a shaft. Also is there anymore mechcanical linkages like a pitman arm or drag link that turn the spindel, or does the hydraulic rams eliminate the need for them. Also is there diagrams anywhere for it.

  7. #7
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    The steering wheel is connected to the orbital via shaft. Remember, the Driver is essentially spinning a "pump" that moves the hydraulic fluid.

    Monster Trucks don't use a mechanical linkage, the steering is done strictly through the hydraulic system. At first thought, this would seem to be for reliability purposes. That is only part of the reason. While it is true, that hydraulic steering was first used on Monster Trucks to eliminate problematic steering boxes and other weak links, as well as reduce loading on the frame, hydraulic steering also offers the opportunity for a safety precaution. Today's Monster Trucks are required to have a pressure relief system that protects the Driver from getting the wheel wrenched out of there hands, possibly causing injury. Due to the incredible loads placed on the the steering, when a truck has an odd hit to one corner it can generate tremendous feedback through the steering. This feedback would be capable of snapping a Driver's wrist it weren't for the pressure relief that by-passes the orbital and absorbs the feedback. Additionally, the long travel suspension systems that today's Monster Trucks use would require very elaborate linkage systems to make a mechanical steering system work. I've seen it done on some large show trucks but those kinds of systems might be difficult to package on a Monster Truck, and as mentioned earlier, a mechanical system would send that dangerous feedback into the Driver's hands.

    I'm not aware of any diagrams of the orbital system on a Monster Truck but they are fairly simple systems. Just look it over at the next event you and take a couple pictures for review. It's easy to figure out. I suppose you could hunt around for some diagrams of hydraulic steering on earthmovers too, those would be pretty similar.

    As for the rear steering, extremely knowledgable MM Member, Viper Crew Chief, part-time Mad Scientist, and just all around good and helpful guy, Rolf Hanson, has made a schematic of the wiring for the auto center controls:

    [ame="http://www.esnips.com/doc/8942cb0e-4a3e-4b18-9df5-452342d0f66a/auto-center"]Rolf's Auto Center Diagram[/ame]
    Monster Truck fan since 1980.
    Those who are too weak to follow their own dreams will always find ways to discourage others.

  8. #8
    Thanks alot Scott, very informative, and the schematic on the rear steer wiring is awsome, again thanks for the help.

  9. #9
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    Today's Monster Trucks are required to have a pressure relief system that protects the Driver from getting the wheel wrenched out of there hands, possibly causing injury. Due to the incredible loads placed on the the steering, when a truck has an odd hit to one corner it can generate tremendous feedback through the steering. This feedback would be capable of snapping a Driver's wrist it weren't for the pressure relief that by-passes the orbital and absorbs the feedback.
    In '89 at Weedsport, NY Mike Wine had the wheel spin on him and basically bent his fingers to the back of his hand and I believe dislocated them.
    Did they not have the pressure relief system on Outlaw at the time?

    Sidenote: Bennett Clark drove Outlaw for Mike at that race.
    Chris Parrish


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