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Sniper

Canadian Rust Bucket
Joined
Dec 26, 2007
Messages
1,916
Location
Ontario Canada
Been playing in the shop again. Built a gas powered chopsaw from a chainsaw. Works not bad, but need to change the gear ratio for a bit less speed and a bit more torque. Buzzed through a 2 x 2 x 3/16 th square tube fairly easy. Now the wrecking yard is going to give up parts a lot easier.;) Seen this idea in a "Farm Show Magazine" awhile ago and thought it just might be worth the effort. $100. bucks later I've got a chopsaw.:)
 

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Ahh-Cool! I'm a sucker for tools. What is the cutting Wheel sprocket/bearing/shaft from? A dead Chop saw?

Thanks

PA41
 
The saw itself is a factory refurbished unit I bought for $60.00 The sprockets are just regular parts from the 'hub/sprocket/belt pulley 'you weld it' stuff that a lot of places sell, nothing fancy. I went with a #35 chain and sprockets because of the tight area I had to get through. Some of the big old honkin saws have enough clearance for a belt and pulleys. Don't try to cut and weld on an old chainsaw bar, I did, and it won't work. What ever the outer layers are, the alloy gets real brittle right beside the weld and breaks very easy. So, I used what I had on hand, a 'U' shaped steel piece in place of the bar, (it was from a set of shelves, about 9 or 8 gauge thick. A bit less than 1/8th thick.) The arbour, bearing and shield are from an old off shore chopsaw that fried the brushes. The hole in the sprocket at the driven end was just a bit less than the teeth diameter on the clutch drum. Chucked it in the lathe and turned the teeth down to size, slid on the sprocket where the cutter chain would have road, and spot welded to each tooth. Put that part back together. Using one of the 'you weld it' hubs, I made it fit the arbour spindle by boring it out to fit the metric shaft. Put a key way in it, welded the second sprocket to it and assembled the works. Drilled the required holes and made standoffs so the shield would be positioned properly for side to side clearence. Put in a new blade, gassed it up and give it a try. The only thing I have to make a change to, is the outer sprocket, it needs to be as big as the room I have will allow. This thing would go into orbit if you firewalled it and let it freewheel. By gearing it down I can run it wide open, and be in the power band of the engine while increasing the torque. It was a bit of 'guess and by golly' engineering so I'm off the mark a bit that way. But, other than that, it looks like it will work as planned. A bit of lathe work is required, where the rest is regular cut, weld, drill. I had to offset the 'bar' by half an inch from the sloted tang that bolts on the saw so the outer hub/sprocket would line up, this would likely be different on other saws. With home brew stuff, no two are going to be quite the same.
 
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looks like a good way to remove those junk yard parts with ease:D

also looks like it can be converted back to a reg. chainsaw when ya get those parts back to the shop and need to build a fire in the shopstove:D
 
also looks like it can be converted back to a reg. chainsaw when ya get those parts back to the shop and need to build a fire in the shopstove:D

Actually your right. The the 'bar' section is just the same as a chain saw bar, remove the two nuts and it's off. Nothing needs to be modified on the saw itself, (except for the drive sprocket,) so a chain bar can go back on. The clutch drum/sprocket would be changed at the same time back to the cutter chain drum/sprocket. I have found an easy way to keep the engine from turning over when unthreading the clutch. Pull the plug, position the piston to the bottom of the bore, take a piece of clean 1/4 inch nylon rope, feed about a foot of it in the plug hole. Bring the piston up to the top, the rope will stop it from turning any farther, soft enough it won't hurt anything. So yeah, you can cut down trees or chop up cars with the same saw.:D
 
You're being altogether too humble! That deserves a build thread, if not here then some other forum?? But lots of us could/would make use of one of these! I can't convert your words into pictures (in my head). OH PLEASE, show us how! Perley
 
You're being altogether too humble! That deserves a build thread, if not here then some other forum?? But lots of us could/would make use of one of these! I can't convert your words into pictures (in my head). OH PLEASE, show us how! Perley

OK Perley, since you said "Please":D

I have to change the outer sprocket for a larger one to slow down the blade. Since it will be apart, I'll take pictures and explain how I went about it so you can see it. The parts you or others have on hand, or have available, might dictate a little different build approach, but the basics would still be the same. I'm heading to northern Ontario later today, so it will be a week and a half, maybe two weeks before I can have the pictures and info for you. See you then. Sniper
 
looks like a zombie chopping tool! haha awesome dude! wish i had one. would make removing parts very easy.
 
Ok, I've been back for a bit, but the saw has been out on loan for the last week and came home earlier today. Picked up a larger sprocket and found out I got the wrong center hole size. So things are on hold until get the proper one, think I may go a bit larger still since I have to remove the outer flange on the "bar" anyway. The sprockets I had on there were 20 tooth driven and a 16 tooth on the saw. Turned the blade way to fast and had little torque. The only reason for the small sprockets was the room I had to work with. But here are the pictures of how it was put together. The next person may have a lot better way of doing it. I'm going to shoot for at least a 3 to 1 ratio for gearing it down. That way the clutch will lock up and the engine will be up to speed and provide the required torque....hopefully. The idea works, just need to get the bugs out now. [;)

#1 Just a view before I took it apart again.
#2 Cover and clutch brake removed, small hole below studs is for chain adjustment pin to sit in.

#3 Clutch and sprocket.
#4 Can bearly see where tips of the chainsaw chain/sprocket were removed enough in the lathe so the #35 chain sprocket could be slipped over them. #35 sprocket was then tack welded to each clutch tooth.

#5 Outer end of bar with arbour and holder. Arbour came from old chopsaw.
More pictures coming!
 

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#6 Collar/hub was turned so there was a shoulder that would bear against the arbour bearing.

#7 Arbour
#8 Bar, arbour, shield.
#9 Cutting wheel side of arbour
#10 A 20 tooth sprocket was removed, a 30 tooth is larger than the 'bar' flanges will allow. Since I have to make some changes, I'm going to see if I can even go bigger on the the sprocket, decreasing the blade speed and improving the torque at the same time. Would like to get a 3 to 1 ratio...we will see! Stay tuned kids. :D
 

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One other option is you can run your barstool when not chopping something.LOL
Nice work, neat idea!!
large_motorized-bar-stool.jpg
 
Ok, finally got this rig redone with the lower drive ratio. It seems 3 to 1 works out quite well. I cut through a 1 X 2 X 1/8 wall tube with a 1/2 inch solid rod welded to the tube just as quick as a shop chopsaw. The last bit of work is a guard for the chain. I would imagine if it came out at speed, it would announce itself. (Hey you!! Whack...owww) So there you go, that's how I went about a home brew gas powered saw. If you try it, just remember...it won't care who you are, it can be dangerous, and it can bite, so be careful. Sniper
 

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well now you have to mount it like a chop saw!!! the electric ones wear out to quick!! say like you could make ie mount to the chop saw base, and it could also be removeable when needed, portable!!![;)
 
well now you have to mount it like a chop saw!!! the electric ones wear out to quick!! say like you could make ie mount to the chop saw base, and it could also be removeable when needed, portable!!![;)

I'm going to save that for the next guy.:D Think I'll quit while I'm ahead.;)
 

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