Engine and pump sizing for wood splitter

jcook5003 · Nov 30, 2015

Hey guys-

After moving into my first owned home, I've started using a woodstove for my primary heat. As such I'd like to build a wood splitter.

I have a nice HEAVY I-Beam on the farm to use for the basis but I need help with pump and engine sizing.

I'd like to use a 4x24 cylinder.

I already have a really nice almost 0 hour Honda GCV160 motor from a pressure washer. It's rated on the net as 4.5-5.5 horsepower depending who you believe, is it enough motor?

I don't know enough about pump sizing and stuff for hydraulics. I was hoping someone coukd point me to some calculations or advice on sizing my engine HP and pump to my cylinder.

Thanks in advance.
Josh

mikefromnh · Nov 30, 2015

It'll pull an 11 gpm two stage 'log splitter' pump.

LD1 · Nov 30, 2015

Yep, 11gpm 2-stage.

HP=(GPM x PSI)/(1714 x Efficiency)

Gotta do 2 calcs for 2-stage pumps.

You can reverse the formula to solve for GPM as follows

(HP x 1714 x EFF)/PSI

A typical 2-stage only flows high flow up to ~650psi so example

(5.5HP x 1714 x 85% eff)/ 650psi = 12.3 GPM

Look the specs of the pump up to find the max pressure and what the GPM is at max pressure and plug the numbers in for that also.

IF you get a larger motor, you can get a 16gpm or 22gpm pump and really make a fast cycle. As is your looking at about 13 seconds with a 11gpm, 9-10 seconds with a 16gpm, and 7-8 seconds with a 22 gpm

jcook5003 · Nov 30, 2015

LD1 said:
Yep, 11gpm 2-stage.

HP=(GPM x PSI)/(1714 x Efficiency)

Gotta do 2 calcs for 2-stage pumps.

You can reverse the formula to solve for GPM as follows

(HP x 1714 x EFF)/PSI

A typical 2-stage only flows high flow up to ~650psi so example

(5.5HP x 1714 x 85% eff)/ 650psi = 12.3 GPM

Look the specs of the pump up to find the max pressure and what the GPM is at max pressure and plug the numbers in for that also.

IF you get a larger motor, you can get a 16gpm or 22gpm pump and really make a fast cycle. As is your looking at about 13 seconds with a 11gpm, 9-10 seconds with a 16gpm, and 7-8 seconds with a 22 gpm

Thanks for that info. Very helpful.

The real question is will the cycle time really make a huge difference?

If you all were doing it would you upgrade engines or use the existing Honda? I have an affinity for Honda small engines as they typically start on the first pull. Plus the price is right.

If I buy an engine I probably can't spring for a new Honda it'll have to be a Harbor Freight.

oldpilgrim · Nov 30, 2015

the 11 gpm pump will be fine as said. Almost all commercially avail splitters have 11gpm pumps, with the 4x24 cylinders and engines around the size of yours.

The cycle time is mostly the same or a few seconds different between brands but isn't really too important as you generally only go into a log a few inches before it splits. The cycle times specd are full length strokes so the shorter strokes actually used when splitting really aren't that noticeable.

jcook5003 · Nov 30, 2015

Very good info. Thanks.

mikefromnh · Nov 30, 2015

If it was me I'd sell the honda and get a 13hp Harbor freight Chonda to go with a 22gpm pump.

I'd rather have a horizontal engine on a log splitter. Not that you can't use a gcv... Just not my first choice.

jcook5003 · Nov 30, 2015

mikefromnh said:
If it was me I'd sell the honda and get a 13hp Harbor freight Chonda to go with a 22gpm pump.

I'd rather have a horizontal engine on a log splitter. Not that you can't use a gcv... Just not my first choice.

Any reason not to use a vertical shafts engine? If I'm building the mounting system does it really make any kind of difference?

Just hate to buy something when I have something servicable, but I'm open to good reasoning.

LD1 · Nov 30, 2015

horizontal or vertical dont make much difference IMO. Seen both, used both, worked on both.

The sole reason for getting a different motor if you do, would be more HP to couple a larger pump to it and make it cycle faster.

I like speed, and splitting wood is the worst part of the firewood process IMO. If you aint splitting much and in no hurry, the 11gpm is fine and sure beats a maul/axe