Engine and pump sizing for wood splitter

[jcook5003]

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]

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

 

[LD1]

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]

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]

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]

Very good info. Thanks.

 

[mikefromnh]

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]

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]

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

 

[jcook5003]

I agree it's the worst part but anything I build is gonna beat the maul and wedge that I split 3 or 4 chords with this fall.

 

[LD1]

Time wise, factor how many times you would need to cycle the splitter to make a cord of wood.

For me, I have found that 400+/- pieces of wood are a cord based on the size I split.

Now some of them dont need split, and some of them yield 2 pieces for each cycle of the splitter. But I figure a fair average is 200-250 splitter cycles for a cord.

Dads splitter is 16 seconds, mine is 8. I cannot split twice as fast with mine, because there are alot of times I dont have to wait on the retract even with his slower splitter as I am grabbing another piece of wood. And rarely do you need to do a full cycle as well.

But figure if you can pick up 2 or 3 seconds per cycle, thats 10-minutes per cord. Not much, but when you split 20 cord a year, and sell wood, time is money and it adds up. I'd guess an average cord of wood takes me ~1hr to split with dads splitter, and ~45 minutes with mine.

 

[4570Man]

He is using a 4" bore cylinder not the more typical 5". 11 GPM on a 4" cylinder is pretty fast.

 

[escavader]

I'm building a faster splitter just cause I want to.when you start looking at the bigger pumps you also need a bigger hydraulic tank just FYI .im building mine right into the I beam on the splitter trying for at least 10 gallons.and I'm using a vertical shaft riding mower engine this time

 

[MossRoad]

I'm using my in-law's 30 year old splitter. Its got a 5hp briggs and the typical 24 x 4 cylinder. It works just fine, but can seem a bit slow, but in reality, when I bring a load of wood home, I dump them off the end of the trailer. I park the splitter next to the pile, turn one round on end for a seat and start splitting. As they split apart, I hit the retract and drop in the next piece as soon as the ram gets back far enough. I have to wait 2-3 seconds for that on 16" pieces. 2-3 seconds doesn't seem like much, but as others said, you do several hundred pieces and it adds up. For me, I use about 24 pieces of firewood per day when its cold.

24 pieces times 30 days = 720 pieces
720 pieces times and additional 3 seconds per pieces = 2160 seconds
2160 seconds divided by 60 seconds per minute = 36 minutes per month of heavy wood usage for me.
36 minutes times 4 months of heavy usage = 144 minutes
18 minutes times 2 months of lighter usage = 72 minutes.
144 minutes plus 72 minutes = 216 minutes, or about 3.6 hours more for the year VS a faster splitter.

Sometimes its nice to rest between pieces and sometimes I'm in a hurry and its annoying. But the splittter is free to me, I have the time, I'm not doing it for commercial sales, etc....

With that said, if I was building a splitter from scratch and had nothing to begin with, I'd go for a faster unit. If I already had smaller/slower components, I'd think about selling or swapping them for faster components.

 

[jcook5003]

Lots of valid points here. I guess maybe I'll shop around for a larger engine. If I find a deal before I start the build I'll upgrade and order the appropriate pump. If not. Slow and steady wins the race for me with the smaller Honda in already own.

Next question. Vertical shafts engines....how are you guys mounting them. I've got some ideas but always open for more.

 

[jcook5003]

He is using a 4" bore cylinder not the more typical 5". 11 GPM on a 4" cylinder is pretty fast.

Any reason to use a 5" over a 4"? Both seem sufficient for the intended use. 4" is readily available locally is why I decided on that size.

 

[4570Man]

I wouldn't turn down a faster cycle time, but I'm happy with mine. It is 13 seconds and I hardly ever have to wait on it. I would use the Honda motor you already have. My Grandpa has a ragged out Kubota G5500 lawn tractor which has a 16.5 hp Diesel engine. I want to use it for a parts donor to build a self propelled splitter with about 20 GPM pump.

 

[4570Man]

Any reason to use a 5" over a 4"? Both seem sufficient for the intended use. 4" is readily available locally is why I decided on that size.

At 2500 psi a 4" bore cylinder will push 31,000 pounds. A 5" cylinder at 2500 psi will push 49,000 pounds. The 5" cylinder will cost more, but you are only paying for that once. The major advantage to a smaller cylinder is with the same GPM it will cycle faster than the larger cylinder.

 

[triptester]

Lots of valid points here. I guess maybe I'll shop around for a larger engine. If I find a deal before I start the build I'll upgrade and order the appropriate pump. If not. Slow and steady wins the race for me with the smaller Honda in already own.

Next question. Vertical shafts engines....how are you guys mounting them. I've got some ideas but always open for more.

Pump mounts are are available for most horizontal shaft engines. For vertical shaft engines generaly require a custom pump mount.

 

[handirifle]

I too, would use what you have, unless you really need the speed (commercial?). I also have a 15hp vertical shaft riding mower engine that I plan someday to build a heavy duty splitter with, but that is down the road a bit. In the meantime I have a Honda 5hp with a 11gpm pump and 4x24 cylinder. It has done everything I can ask of it so far, and that includes occasional cross splitting. I also have a 5 gallon tank for fluid. Plan on getting at least a 10 gallon, as mentioned above.

Unless you really need the speed now, MossRoad had a lot of good points.

My plan for my upgrade, is when I "happen" across the materials needed to make the larger one. Also one BIG reason, I will build mine, is I want a horizontal/vertical model, and mine is horizontal only.