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Cordwood saw question

Started by Bruno of NH, January 14, 2024, 12:44:15 PM

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Bruno of NH

I want to convert this pto saw to a gas engine
1st question I have a kholer 7.5 hp engine would that be enough?
2nd question Can I just take out the pto gear box and put the pulley right on the engine shaft and run it that way ?

Lt 40 wide with 38hp gas and command controls , F350 4x4 dump and lot of contracting tools


Do you have more pics of the saw that show more of the setup?
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others


I don't know of any reason why you couldn't.
However, the speed that you feed the stock to be cut and the type of wood it is and the blade sharpness may dictate your results.
Also the pulley ratios (motor to input shaft) would need to be in the 3600/540 ratio.  (I'm assuming the engine max. speed is 3600 RPM and that the max. recommended blade speed is 540 RPM) personally I would not suggest spinning the blade of one of those toys faster than 540 RPM unless it is recommended by the manufacturer.  Note: I'm assuming your engine is gas and gets it maximum power at full speed (3600 RPM).  The thing that would help you with that engine is if you could add a flywheel or two to the system to try and maintain the speed while cutting.  As an FYI I own one of those toys.

W-M LT40HDD34, SLR, JD 420, JD 950w/loader and Woods backhoe, V3507 Fransguard winch, Cordwood Saw, 18' flat bed trailer, and other toys.


Bruno of NW  I don't think your 7.5 Kohler will handle it. The one I built I run a 13 HP Honda on it and it loads it right up. I have the engine running to a jack shaft and then from the jack shaft to the blade shaft to get the proper speed on the blade. I do run the engine wide open. I forget the exact speed they want the blade shaft running. Sorry no pictures and its in a shed on a farm fifteen miles away with many snow drifts in the field.

Bruno of NH

I have no problem buying a new engine for it
Lt 40 wide with 38hp gas and command controls , F350 4x4 dump and lot of contracting tools

Woodside Kai

I've also got one with a 13hp and wouldn't want any less power.  Thick slabs will bog mine down if fed too fast.


The only thing that I can say about running a cord wood saw, is wear a face shield on your hard hat helmet.
I had mine on when a piece of wood come up from the table and hit me in the face (shield).
Others were killed by such a thing happening.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Gere Flewelling

Bruno- I have a similar cordwood saw that I originally had powered by a Wisconsin engine when I first built it as I did not have a tractor. I had it built onto a trailer. It worked well for a long time, but as I was eventually able to afford a tractor I converted it to a TPH unit and run it off my PTO.  Based on my experience I would suggest that you need to find some kind of a clutch system for your motor to enable you to disconnect the engine from the saw to allow for starting of the engine without turning the saw.  This could be as simple as having a belt tensioner setup with an over center lever to engage and disengage.  The Wisconsin engine I used back then had a mechanical clutch that worked like any clutch on a piece of machinery.  As far as belt speed, I would suggest you leave the right angle gear box in place and add a pulley system to the input side of the gear box.  This will give you better options to slow down the engine speed to match the 540 rpm's the gear box was designed for.  Plus this will allow you to keep the small pulley on the saw arbor to allow more room for table travel.  I have found it quite a challenge over the years to keep the belts from slipping on the arbor during big cuts.  This requires considerable tension on those belts.  I would not want to be loosening the tension to release the drive on those belts.  If you use pulley size on the input side of the gear box you can put the larger pulley on the gearbox and smaller one on the engine and have room for a tensioner to work there.
Many people have concerns about these type of saws, but I prefer this type of saw for cutting up firewood to a chainsaw. I have used mine for over 40 years now and after cutting up many hundreds of  cords of firewood, I can honestly say that I have had many had many more close calls with my chainsaws than with the circular saw.  It requires a great amount of common sense be used when ever sawing.
My cordwood saw is one of the first  "success stories" I ever had at attempting to build my own piece of equipment to use in the firewood process.  The JD tractor is handy to power it now but I do miss the sound of the old V-4 Wisconsin with a straight pipe when the governor opened up.  Kind of like the sound of of a Harley to some.   
Good Luck with your conversion!
Old 🚒 Fireman and Snow Cat Repairman (retired)
Matthew 6:3-4

Don P

A friend sent a link to a neat one just the other day. It had a hit and miss engine hooked to it. That old Fairbanks-Morse ran at 400 rpm.


Some important bits of info to figure this one out.  The tooth speed of the circular saw is generally set around  9000 to 10000 feet per minute for efficiency of cut and sawdust removal.
So the size (diameter) of your saw blade is important to work this out to see if you need to gear the pulleys ratio connection of the engine.  For the size of the engine - off hand I ran a 28 inch carbide saw on a 15 hp engine and upgraded to 20hp twin with very satisfying results.


Easy does it

Bruno of NH

At this point I think I will do what a friend did.
He found a low hr 2wd kubota diesel tractor for $600 and runs his off that. I'm was trying to not tie up the tractor I have now on the saw.
Lt 40 wide with 38hp gas and command controls , F350 4x4 dump and lot of contracting tools


I think you will be much happier with a small Kubota tractor to power the saw rig.The flywheel effect alone will be a plus.
Good Luck
1997 WM Lt30 1999 WM twin blade edger Kubota L3750 Tajfun winchGood Health Work is my hobby.

Gere Flewelling

I ran my saw for a while on a JD 750 (around 20 hp). It worked great and had plenty of power for sawing hardwood. Gave that tractor to my son so I am back to running it on the bigger tractor. Wise choice sticking with the tractor in my opinion.
Old 🚒 Fireman and Snow Cat Repairman (retired)
Matthew 6:3-4


I've got either a 32 or 36" buzz saw that has been adapted to a three point or a stake down .A Ferguson TO-20 does fine but a John -Deere 70 will really spin it .. I haven't used it for decades .You can cut 10-- 12" stuff with it if you can lift the log .I'm not certain I still can ,not even going to try .I've got little chainsaws for that these days.

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