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Hydraulics,ICE Motors
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WiperMotor



Joined: 04 Sep 2006
Posts: 301
Location: SA,Australia


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Ok seeing I have just bought a pump I wanted to know what I could use as a valve? someone said to me that you had to use the steering box Confused or could I use a normal hydraulic valve?

and dose anyone know what sort of belt a syline r33 takes? Shocked

Post Sun Nov 26, 2006 3:56 pm 
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Glen
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if your using a petrol motor to drive the pump wouldnt you need some form of special valve otherwise the flow would just build up behind the valve and stall the engine ? (i guess thats why you need the steering pump valve)
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Post Sun Nov 26, 2006 5:03 pm 
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WiperMotor



Joined: 04 Sep 2006
Posts: 301
Location: SA,Australia


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I THINK there is a valve inside the pump itself (steering pump),or using a normal valve (like on tractors ect) it would divert the fluid back to the tank

Post Sun Nov 26, 2006 5:06 pm 
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Totaly_Recycled
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Joined: 15 Jun 2004
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power steering racks have a valve built into the steering gear box .when the steering is centered (ie no torque from the steering wheel ) the valve is open so the flow is from the pump through the valve and back to the pump.

when you turn the steering wheel there is a torsion rod betwen the steering wheel shaft and the stering box inside the valve body .

The torsion rod twists closeing a port and diverting the flow of oil through to one end of the ram and alowing the oil from the other end to go back to the pump.

As soon as you stop turning the steering wheel the ram stops extending torque is lost on the valve and the flow diverts back to the pump .turning the steering wheel the other direction reverses the flow of oil through the ram and it goes the other way.
once there is no torque on the steering wheel the oil flows from the pump through the valve and back to the pump.

If the steering is turned all the way until the ram is fully extended and torque is kept on the steering wheel then presure builds up in the ram and pump until a presure release valve built inside the pump opens and lets the exces presure go from the outlet to the inlet of the pump and the oil circulates under high pressure .

Post Sun Nov 26, 2006 5:50 pm 
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WiperMotor



Joined: 04 Sep 2006
Posts: 301
Location: SA,Australia


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Hummm I see,oh well I'll use a normal valve then! Thanks for the detailed reply! Smile

Post Sun Nov 26, 2006 6:00 pm 
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Totaly_Recycled
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Joined: 15 Jun 2004
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normal flow valve works the same way except that it isnt rotary the oil still goes from the pump through the valve and back to the pump when you move the lever you shift the flow to the ram or hydraulic motor you are powering .

you cant just put a single valve between the pump and the ram and close it as the presurte will build up and load the pump and your prime mover (i/c motor) contioniously .causeing heat and eventual boiling of the oil .

Post Sun Nov 26, 2006 6:20 pm 
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WiperMotor



Joined: 04 Sep 2006
Posts: 301
Location: SA,Australia


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I was thinking somthing like this


and a valve like this


I found this on the internet heh



?????

Post Sun Nov 26, 2006 7:48 pm 
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Valen
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nice schematic lol
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Post Sun Nov 26, 2006 10:42 pm 
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Totaly_Recycled
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Joined: 15 Jun 2004
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just need to add a resiviour

Post Sun Nov 26, 2006 10:51 pm 
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WiperMotor



Joined: 04 Sep 2006
Posts: 301
Location: SA,Australia


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quote:
Originally posted by Valen:
nice schematic lol
Thanks Laughing

there's a resivor on the back of the pump and the ram and hoses will hold some oil too

Post Sun Nov 26, 2006 10:59 pm 
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WiperMotor



Joined: 04 Sep 2006
Posts: 301
Location: SA,Australia


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it's been a while . . . . . .

well I now have the pump,motor,oil and I'm getting a nice stanless steel tank made up Very Happy ~1 foot square,now all I need is a valve and some hoses Confused

Post Fri Dec 22, 2006 11:41 pm 
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Totaly_Recycled
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You wont need a i foot square resivior .

The resivoir is mainly to take pulses and surges and to give the oil some where to go as a return for the pump and to alow for expansion in the system as the oil warms up, if you are only useing rams and the system isnt going to be run contionious all day then 250 to 500 ml would be a big enough tank.

I personaly would make up a small plastic tube type resivoir and set it up like a hydraulic ram so the cap is a piston . This way you fill the system till all the rams the pump hoses ect have no air in them then half fill the resivior .

The internal piston -cap has a small bleed screw -cap grip on it for bleeding and removing it to add more oil ,open the bleed screw push the cap -piston down the resivior until the oil starts to come out the screw - bleeder then close it , then use a spring that is strong enough to move the piston against the seal friction on top of it with another cap on the end ofthe resivior to hold the spring.

This then makes a non spilable resivoiur that has a pre-set presure from the spring that will keep the pump primed in any orientation.

The piston can slide up and down the resivior to allow for expansion or any small loses due to leaks , hose expansion or diferant volumes of oil flow from double ended rams etc.

Post Sat Dec 23, 2006 6:52 am 
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maddox



Joined: 21 Dec 2006
Posts: 786
Location: Belgium


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Pity I can't post any pictures yet (they on my dead hard disk), but recently I did do a bit on hydraulics for a UK roboteer.

Main issue with commercial hydraulics is the weight. A small valve like shown here can weight 2 kg, A ram with 50mm bore and 150 mm stroke of 10 kg isn't a big surprise either.

Basic information to remember is that the Robot wars rules (or Battlebots) impose a maximum pressure limit, and that is what we want to use. Because with high pressure we can reach high force from a small diameter ram.
The simplest, lightest and cheapest pumps are the gearpumps. These are found on lorry loading hatches and small (or cheap)forklifts.
These have a "normal" upper limit of 3000-4000 psi (depending on brand) that is why this is the current limit for the FRA on Hydraulic pressure.

Now, basic formula for hydraulic and the needed power is flow(liters/min)*pressure(bar)/500=power needed in Kilowatts.

A normal sized lorry pump is 4 CC/rev. with a top rev of 3000 rpm (standard commercial electric motor rev),This gives us 12L/min at top speed.
4000psi is 260 bar
12*260/500= 6.24Kw needed. Now, the pumps used in lorries aren't loaded so high, with good reasons. So the most of them will run on a 3 KW series wound motor.

So, reduce the pressure or the flow to get the best out of the motor/pump combination available, or match the pumpsize to the motor.

A bosch GPA 750 on 24V can drive a pump delivering 1.4L/min @260 bar. At 75% efficiency. This means you can drive this pump on 1 24V 3600mAh NiMH pack of a good brand.
Now, the size is 1.4L/min /3300 rpm. So a .42 CC pump is in order.
if this is not available, working with a gearing is an option.

Have fun with this information.

Post Sat Dec 23, 2006 4:00 pm 
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WiperMotor



Joined: 04 Sep 2006
Posts: 301
Location: SA,Australia


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no worries,Thanks for the help guys Very Happy Very Happy

Post Sat Dec 23, 2006 4:04 pm 
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WiperMotor



Joined: 04 Sep 2006
Posts: 301
Location: SA,Australia


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it would be cool to have a full hydraulic robot Very Happy

hydraulic drive and wepon Cool

Post Sat Dec 23, 2006 8:13 pm 
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