tire shear /rim crusher /logsplitter pump?

ak9 · Oct 30, 2011

About a year ago I refurbished a used log splitter using 12hp b&s vert shaft gas eng. with a new 16 gal /pm 2 stage splitter pump . It has a 4.5x1.75x25" tie rod cyl.. This set up had been working well for @ 40 ish hrs of use when the pump seal @ the shaft leaked & blew:confused3:I have a hyd. gauge that I watch & when shearing a tire does'nt go over 2000psi ( it could ,i don't whine the engine up that high )
So I'm searching to find another/ better hyd pump for my application . It seems when shearing a tire causes the most stress on the splitter as right before the bead shears, kinda like a difficult log to split then kinda pops free . I'm thinking this hyd shock repetively may have caused the seal failure? The rim crushing is easier than splitting most hard woods, surprisingly.
so, should I use a different type of gear pump? ... or vain pump ? or Do you think this pump was bad ??? little help ?

Ak9

tommu56 · Oct 30, 2011

ak9 said:
About a year ago I refurbished a used log splitter using 12hp b&s vert shaft gas eng. with a new 16 gal /pm 2 stage splitter pump . It has a 4.5x1.75x25" tie rod cyl.. This set up had been working well for @ 40 ish hrs of use when the pump seal @ the shaft leaked & blew:confused3:I have a hyd. gauge that I watch & when shearing a tire does'nt go over 2000psi ( it could ,i don't whine the engine up that high )
So I'm searching to find another/ better hyd pump for my application . It seems when shearing a tire causes the most stress on the splitter as right before the bead shears, kinda like a difficult log to split then kinda pops free . I'm thinking this hyd shock repetively may have caused the seal failure? The rim crushing is easier than splitting most hard woods, surprisingly.
so, should I use a different type of gear pump? ... or vain pump ? or Do you think this pump was bad ??? little help ?

Ak9

I think you pump was OK till you pushed over its limit.
What is the spec's on the pump?

Your releif valve in the cylinder valve should have taken the high presure and dumped it to the tank if it was set correctly.

You need a larger cylinder to give you more push pressure

4.5 " cylinder at 1800 psi = 28628 lbs
5"same pressure 35343 lbs
6" same pressure 50894 lbs

link to the calculator
Hydraulic Cylinder Calculator

I say invest in a larger cylinder instead of cranking the pressure up

J_J · Oct 30, 2011

Your pump should be able to achieve 3000 psi. Your relief on the valve will limit the pressure, so you might try setting the pressure limits up to about 2900 or 2950 psi. If you can not get that pressure by fully extending the cyl and holding, then you have some leakage somewhere.

47,713 lbs of force using a 4.5 cyl and 2 in shaft at 3000 psi.

ak9 · Oct 31, 2011

tommu56
I was considering a larger hyd cylinder or 2...not so much for more force but , for less speed under load. the cylinder on there now does the job but a little fast under load . this is the pump that blew

surplus center = 16 GPM 2 STAGE HYD PUMP
Brand new, MTE HYDRAULICS two stage HI/LO pressure hydraulic gear pump. Ideal for applications such as log splitters, presses and other equipment where rapid movement of the cylinder at low pressure is required prior to automatically switching to the high pressure mode to meet load requirements. The change from LO to HI pressure is automatic with the LO stage pressure preset at 500 PSI. Minimum of 8 HP required for gas engine use.

SPECIFICATIONS Displacement:
0.192 cu. in. / rev. HI press. stage
0.994 cu. in. / rev. LO press. stage
Pump Type Gear
Rotation CW
Pressure: 3000 PSI max.
Speed: 3800 RPM max.
Flow:
3 GPM HI press. stage
16 GPM LO press. stage
Unloading Pressure 500 PSI
Mount 4 bolt USA 4F17
Shaft 1/2" dia. x 1-1/2" long keyed
Rqd. Filtration 25 micron
Inlet Port 1" Hosebarb
Outlet Port 1/2" NPT
Size 6-9/16" x 4" x 3-11/16"
Shpg. 12 lbs.

jj
If I crank the rpm on the engine up the valve does by pass @ 2800psi .I have'nt been ruuning the motor at max rpm in an effort to keep the hyd cyl slower under load..(The engine will stall before by pass) I think I need to slow cyl.speed down a bit when the anvils come together and recieve load . It seems to me the seal should not have blown out with less than 3000psi. ?

ak9

J_J · Nov 2, 2011

You can make the cyl slow or fast by feathering the valve.

ak9 · Nov 3, 2011

tommu56
thanks for the baum site . what a wealth of Info there ... I used to have a bunch of sites like that saved and the lost um all when my PC crashed a few months ago

I am going to fab on another 4.5 " cylinder onto the machine .I did'nt want to increase the psi because I'm unsure the tierod cylinder i'm useing now is rated over 2500psi .
I probably will use another 2 stage gear pump 16gpm . So, with this new set up I 'll probably need a bigger resevoir for the added cyl.
jj
I took a gear pump apart mainly to get abetter understanding of it . The shaft seal on this gear pump was single lip ... thats it.. I'm not sure how much pressure it sees in use tho ,but obviously it sees fluid during use.What I might try is putting a dual lip seal on it and see if it holds ($4.65) ? Is there some seal internally to these gear pumps ( I did'nt see any when i took one apart ) or is it's seal more of close tolerence of the the components?
Yes fethering the valve i had been doing repetively ... I'm not sure if this caused pump seal failure do to pulse loads on it ? thanks

ak9

J_J · Nov 3, 2011

ak9,

From all that you have said, it appears to be a part failure. Feathering does nothing more than let a little bit of fluid through to the cyl.

You have potential pressure available when the pump is running, The pump only develops pressure based on the load, and when the load pressure is equal to the PRV pressure, it then relieves until the load is decreased.