pump and motor size ?

[captjack]

Hello

We are starting a log splitter project and have acquired a 26x5x2 cylinder off a dozer.

I am leaning toward a 28 gpm pump to increase cycle time.

What size motor should I be looking for to run such an animal?


We might end up building something like this instead of a regular splitter with a 6 way wedge.

YouTube - the best wood splitter


its kinda of a neat idea - would like to see it on some knotty oak !

 

[captjack]

we are looking for fast cycle times with this splitter as well as power.

 

[J_J]

16 HP

 

[LD1]

There is no short answer. There are a few variables you need to consider first.

The formula is GPM x PSI divided by 1714 x efficency.

So the variables you need to consider are

1. What is the max PSI of the pump.

2. Is it a single stage 28GPM or a two stage???
If it is a 2 stage like this one Haldex Hydraulic Pump — 28 GPM, 2-Stage, Model# 1080036 | Pumps | Northern Tool + Equipment
Then the 28GPM would likely be at a reduced psi, something like 650psi. And the full 3000PSI would be at a reduced GPM, probabally around 4 or 5. (that website does not list the specs)

If a two stage, you would need to calculate both ways. But northern tool shows a 12HP motor as a minimum.

But if you want a single stage pump, It will require more HP.

28x3000=84000
1714x85% eff=1456
84000/1456= about 58 HP to run. I am sure this is not what you want. But it gives you an idea how to use the formula.

 

[captjack]

The more i look into this the more things come into play. First the valve for a 28 gpm pump are expensive ! we are going to make a log lift as well as a hydraulic wedge.

I was happy to go with a 22gpm pump but i think the 26x5x2 ram will not move as fast as I want it to.

is there a way to figure out cycle times ? if I can get away with the 22gpm pump it would save me a ton of money

thoughts ?

 

[LD1]

calculate the volume of the cylinder.

5/2=2.5
2.5squared =6.25
6.25 x pi x 26" length=510 square inches

508/1728 to concert to cu/ft =.29

.29 x 7.48 gal per cu ft = 2.2 gallons of fluid

then just a little math frome there using a 22 gpm pump, it would take 6 seconds to extend. slightly less on the return due to being less volume because of the cylinder rod. You can figure the area of the cylinder rod and subtract it from the total area and figure it exact if you want.

So you are looking ar roughly a 11 second total cycle time with the pump in "high" gear

 

[kennyd]

Jack, use some of these calculators to help in your decision: Baum Hydraulics Corp :: Spec Calculator

 

[AKKAMAAN]

And the full 3000PSI would be at a reduced GPM, probabally around 4 or 5. (that website does not list the specs)

All Haldex two stage pumps are flow rated at 3600rpm
This pdf have all the displacement data for all pump combinations...

Small gear displacement 0.465 cui/rev
Large gear displacement 1.395 cui/rev
High flow>>(0.465 + 1.395)*3600/231=28.98 gpm
low flow>> 0.465*3600/231=7.24 gpm

Low pressure adjustable between 400-900psi>>high flow power=6.77-15.23hp

Low flow/high pressure power at 3000psi=12.67hp

 

[LD1]

All Haldex two stage pumps are flow rated at 3600rpm
This pdf have all the displacement data for all pump combinations...

Small gear displacement 0.465 cui/rev
Large gear displacement 1.395 cui/rev
High flow>>(0.465 + 1.395)*3600/231=28.98 gpm
low flow>> 0.465*3600/231=7.24 gpm

Low pressure adjustable between 400-900psi>>high flow power=6.77-15.23hp

Low flow/high pressure power at 3000psi=12.67hp

You didn't figure the 85% efficenty into the equation.

Thus with that figured in, you would need 7.96-17.91 on the highflow and 14.9 on the low flow side taking 85% efficency into account.

 

[AKKAMAAN]

You didn't figure the 85% efficenty into the equation.

Thus with that figured in, you would need 7.96-17.91 on the highflow and 14.9 on the low flow side taking 85% efficency into account.

The total efficiency is 100% minus the volumetric losses and mechanical friction losses, added together. Volumetric pump efficiency is factor that depend on pressure and fluid viscosity. With very low pressure and high viscosity, efficiency gets closer to 100%


The pump rating is with out calculating efficiency...that's right, but you do not have to add more HP because pump is leaking internally (inefficient)....your 85% volumetric inefficiency factor will reduce flow out put....15% of theoretical flow will leak back to suction side.... That do not take extra HP....the only extra HP needed is for the mechanical friction losses, in bearings, pump gears etc.

You can use the efficiency factor to calculate the required pump displacement, to calculate a NET flow output...