Hydraulics and Custom Cars

[OoReFLuXoO]

There's definitely not a heat issue, they only run the pumps for under 30 seconds.

There's an On/Off toggle switch. ON - makes the car pressure spike up, when its up in the air, you hold the switch to the OFF position. Which opens the gravity return dump valve, to the reservoir.

With the right timing, you pressurize the system again. Assistance with the coil spring and you get higher. And repeat about 10-12 times.

If you were to open the pump right after, you could literally dip you hand in the oil right after no problems

 

[roadrunner1]

I suggest an ISO 32 fluid.

 

[tom slick]

Originally Posted By: OoReFLuXoO
I agree, it probably isnt as much as it seems.

Whats you opinion? Does the size of hose matter, I would imagine a smaller hose would take less fluid to move/fill the cylinder.

"Bigger gear pump with smaller hoses and cylinder diameter."
In theory it makes sense to me but, Im not an Fluid motion/hydraulic expert.

The ID on the cylinder is about 1.0" with an 8" stroke. So yeah, there's not really alot going on in there!


1/2" hose (-8) can flow up to 20 gpm and 3/8" hose (-6) can flow up to 12 gpm according to the Nomographic Chart.
Here's the math:
a 1"x8" cylinder has a volume of 6.3 cu.in
20 gpm is 71 cu.in per second
12 gpm is 46 cu.in per second
5 gpm is 19 cu.in per second

at 20 gpm it takes .09 seconds to fill that cylinder
at 12 gpm it takes .14 seconds to fill that cylinder
at 5 gpm it takes .34 seconds to fill that cylinder.

Looking at the pumps they use for hopping, they are fairly small compared to industrial/agricultural pumps. Even a 10 gpm pump powered by 220v is relatively large.

I'd bet they pumps are in the 5 gpm or less range. That would explain the common use of -6 hose.

 

[OoReFLuXoO]

Originally Posted By: tom slick
Originally Posted By: OoReFLuXoO
I agree, it probably isnt as much as it seems.

Whats you opinion? Does the size of hose matter, I would imagine a smaller hose would take less fluid to move/fill the cylinder.

"Bigger gear pump with smaller hoses and cylinder diameter."
In theory it makes sense to me but, Im not an Fluid motion/hydraulic expert.

The ID on the cylinder is about 1.0" with an 8" stroke. So yeah, there's not really alot going on in there!


1/2" hose (-8) can flow up to 20 gpm and 3/8" hose (-6) can flow up to 12 gpm according to the Nomographic Chart.
Here's the math:
a 1"x8" cylinder has a volume of 6.3 cu.in
20 gpm is 71 cu.in per second
12 gpm is 46 cu.in per second
5 gpm is 19 cu.in per second

at 20 gpm it takes .09 seconds to fill that cylinder
at 12 gpm it takes .14 seconds to fill that cylinder
at 5 gpm it takes .34 seconds to fill that cylinder.

Looking at the pumps they use for hopping, they are fairly small compared to industrial/agricultural pumps. Even a 10 gpm pump powered by 220v is relatively large.

I'd bet they pumps are in the 5 gpm or less range. That would explain the common use of -6 hose.



Good looking out on that one, I get a kick out of the technical aspect. When using this old style tailgate pumps. You have a choice of gear you want to use/install...

#9 = 6 Lpm / 1.585 Gpm

#11 = 7 Lpm / 1.849 Gpm

#13 = 9 Lpm / 2.377 Gpm

But of course that changes with the RPMs!

 

[Colt45ws]

http://www.finditparts.com/t/218/manufacturer/donaldson/products/241745/donaldson-p561140
30GPM, 5psi bypass, SAE-12 O-ring fittings.
http://www.apartsdepot.com/detail.cfm?part=1840719
Filter, 5.35" length, Synthetic media, Beta1000=10um (99.9%), Would reach bypass pressure at around 20GPM when clean.

 

[morris]

back in the early 70s i worked at Case in wichita in the experimental shop. we made a large prototype trencher with 2 closed loop pumps driving the tires. about 40-50 gal. they put a 10,000 psi gauge on the loop. pumps pressure limit setting was 5,000 psi. after 1 day of testing the needle was in an S shape

 

[OoReFLuXoO]

Originally Posted By: morris
back in the early 70s i worked at Case in wichita in the experimental shop. we made a large prototype trencher with 2 closed loop pumps driving the tires. about 40-50 gal. they put a 10,000 psi gauge on the loop. pumps pressure limit setting was 5,000 psi. after 1 day of testing the needle was in an S shape


[censored]!!

 

[OoReFLuXoO]

Originally Posted By: Colt45ws
http://www.finditparts.com/t/218/manufacturer/donaldson/products/241745/donaldson-p561140
30GPM, 5psi bypass, SAE-12 O-ring fittings.
http://www.apartsdepot.com/detail.cfm?part=1840719
Filter, 5.35" length, Synthetic media, Beta1000=10um (99.9%), Would reach bypass pressure at around 20GPM when clean.


Relatively inexpensive, work the experiment. And the benefits to reap!

It would have to be hidden, considering it wouldn't look pretty. Unless it was taken to a custom chrome shop!!

 

[camelCase]

Whenever I have any weird issues or needs with hydraulic fluids, I always give slfi a shout. They have quite a good selection of fluids to choose from and they are super friendly (which keeps me coming back).

I'd say try out one of their Anti-Wear hydraulic fluids in a 32ISO.
http://www.slfi.net/mineral-oils/hydraulic-oil


EDIT - I forgot to add - never add a filter before a hydraulic pump or at the discharge of a power piston. The added suction force required, if you were to put it before the pump, could shorten the life of that pump by over half.

 

[OoReFLuXoO]

Thats something to keep in mine.

I was debating of adding an internal screen filter on the gear pump itself to avoid and metal shavings getting pulled into the gear, check valves or solenoid valves.

 

[camelCase]

Originally Posted By: OoReFLuXoO
Thats something to keep in mine.

I was debating of adding an internal screen filter on the gear pump itself to avoid and metal shavings getting pulled into the gear, check valves or solenoid valves.


Careful.... too much filtering/screening before a pump can cause cavitation issues.

Clean the sump REALLY well and filter after the hydraulics. Catch all the crud before it goes into the sump.

 

[ac_tc]

I belive that there are nomerous no-no´s from
an hydraulic standpoint built in here..
Bouncing fex will create both pressure and vacuum spikes.
Foaming indicates that the fluid is mixed with air probabbly due
to a combination of a bad tank/ return line design and the fact tha the system isnt pressurised on both sides and therefore sucks air through the seals when it feels vacuum.
To makes thing worse you are probably way overspeeding the pumps
wich makes em work out side their design parameters.
Air in the oil makes your system work like a diesel engine...