I'm thinking about making a special purpose sawmill attachment using a chainsaw bar and running it with about a 7.5 hp electric motor. Will this be a totally custom mount, or is there something out there already? I think it will require a fairly big drive sprocket to get the chain speed. Thanks.
I have been contemplating some of the same stuff. I need to have a package cut off saw. $8k for a new one is nuts.
PC
Quote from: paul case on December 08, 2016, 07:35:51 PM
I have been contemplating some of the same stuff. I need to have a package cut off saw. $8k for a new one is nuts.
PC
I saw the price of those and thought the same thing, Paul. There's not much to them.
A lot will depend if your using a 1750 or 3600 rpm motor. I would seriously look into harvester bars sprockets and chain and their design speed. Frank C.
Most likely 3450 TEFC.
Typical chain speed on a chainsaw is about 4000 - 5000 ft/min. My Stihl and my Jonsereds both run at 4200 ft/min in normal operation with a 7 tooth sprocket.
For an Oregon harvester chain, speed range is between 3000 ft/min to 8000 ft/min. Recommended speed is 8000. This is 0.404 pitch, 0.063 guage.
When you get the heavier harvester chain moving at 8000 ft/min, the chances of a chain breaking and sending pieces flying goes way up.
Instead of mounting the sprocket directly on the motor, you could use a chain drive (short chain, 2 sprockets) to speed up the drive shaft.
Dave, I was considering building a slabber once, I was going to use a motor, and a belt/chain drive to a shaft with a pulley on one end and a sprocket on the other.
That way you can change the rpm of the drive axle.
I have one . I'll get a pic.
I built my sawmill using electric motor, see here:
https://forestryforum.com/board/index.php/topic,90578.msg1394410.html#msg1394410 (https://forestryforum.com/board/index.php/topic,90578.msg1394410.html#msg1394410)
I would strongly advise against using a chain, I tried it actually. 40 chain it was I think, but the rpms were too high for a chain, centrifugal forces dried the chain completely in about two cuts. V belt is your best bet, you can get pulleys from Surplus center to make any ratio you need.
I would run the chain slower than on a chainsaw. Remember the old gear reduction saws they cut well and seemed to stay sharp a long time. I still say go with harvester components at their design speed. Frank C.
Howdy,
How about something like this.
Regards
Gregg
Hi Dave, some lessons that I learned from my slabber project.
1 - yes, 7000 fpm on the chain will cut like a striped ape, but the chains don't last long!
2 - 4K fpm lasts much better.
3 - source your sprocket before you source your bar. The reason why is that the smallest harvester sprockets are wider diameter than the ends of most chainsaw bars, and your chain won't stay in the groove. You want a bar where the end closest to the sprocket is wider than the sprocket that you choose.
4 - if your bar is really long (6'+) be prepared for it to sag some in the middle. I ended up designing and fabricating a slightly cantilevered tensioning system that causes the center of the bar to bow up slightly when it's tensioned to help alleviate the sag.
3600 rpm motor with a 4" sprocket diameter will give you a chain speed of around 4K fpm.
Here you go ;D
(https://forestryforum.com/gallery/albums/userpics/22511/SAM_0999.JPG?easyrotate_cache=1481388043)
(https://forestryforum.com/gallery/albums/userpics/22511/SAM_0997.JPG?easyrotate_cache=1481387978)
(https://forestryforum.com/gallery/albums/userpics/22511/SAM_0998.JPG?easyrotate_cache=1481388009)
The time and date
are off.
You can see how it works.
So what's this sawmill attachment gonna be?
My first guess is a sawmill mounted edger.
My second guess is that it will be for crosscutting to end trim or make firewood with greater ease and accuracy.
My third guess is that you're taking on work as a whale butcherer and you have so many whales to be filleted that you want to make your sawmill able to make multiple cuts in a single pass.
It's number three isn't it?
Thank you for all the replies. What I need to do is cut a number of wide forked or curved logs for timber framing. I don't want to mess with a Granberg type mill or chainsaw power heads. A dedicated slabber would be ideal, but isn't in the budget or timeframe right now.
Not to hijack this thread but could this be done with a verticle shaft gas engine???
Sure, but it would have the same limitation of a 3,600 rpm shaft speed.
Quote from: Dave Shepard on December 11, 2016, 12:37:55 PM
Sure, but it would have the same limitation of a 3,600 rpm shaft speed.
Which is why most dedicated slabbers run a belt drive to a jackshaft, and mount the sprocket there. That way you can have whatever rpm out want on the sprocket, and it also isolates the bearings of the motor from the vibration of the chain cutting. You can put some big meaty bearings on the jack shaft, and they are easy to replace if they do wear out.
Dave, how wide of logs do you plan to cut? 7.5 hp might be a bit limiting unless they are fairly small logs.
http://www.engineeringtoolbox.com/electrical-motors-hp-torque-rpm-d_1503.html
Not sure if this is of any help but I built a chainsaw mill/slabber using an old vertical shaft garden tractor motor (13hp), a 28" chainsaw bar, milling chain, and a harvester sprocket. The chains runs at approx 7600 RPM (motor is at 3600RPM) using a combination of pulleys and a v belt.
No clutch required as I run the belt relatively loose. The only regrets/issues are not going to a bigger bar as the effective cutting width is only 21" and the way the bar is held in place. I ended up devising a weird contraption that pinches the end of the bar just before the tip when I could have simply drilled two hole through the bar and ran threaded rods through it.
(https://forestryforum.com/gallery/albums/userpics/42235/WP_20160227_001.jpg?easyrotate_cache=1481559404)
(https://forestryforum.com/gallery/albums/userpics/42235/WP_20160526_002.jpg?easyrotate_cache=1481559654)
Be prepared for the amount of sawdust generated!
Quote from: scsmith42 on December 12, 2016, 09:23:18 AM
Dave, how wide of logs do you plan to cut? 7.5 hp might be a bit limiting unless they are fairly small logs.
I'm cutting forked trees. The distancee at the tops of the fork might be 5.5 feet apart, but there won't be much actual wood to be cut. Think giant slingshots. Anybody know how much a Petersen DWS is?
Howdy Dave,
I'm not quite sure what I can post on here but, if you want to give us a call on the toll free 888-995-7307 we can get you a quote.
Regards
Gregg
Dave, it was in my plan to build dedicated slabber for my LT40 when I lived on the west side of the Cascades here in Oregon but now that I have moved to the east side the trees are not as big and I put the idea on hold. It was my plan to take the padded chair of the operator seat attachment and mount the slabber to it. I was planning to use an 18 horse vertical shaft lawn mower engine and gear it up using pullies and a jack shaft as Ianab described. This project is still on my to do list, but not nearly as close to the top as it was a couple of years ago.
Dave...Seems to me you're pretty handy with hand tools. if you only have 1/2 a dozen or so to make, sharpen your axe and chisels and dust off your mallet. If you're making them for a client, you can add a premium for being hand dressed. added bonus is that you can save your nickels for the next toy tool on the list.
yes, it can be done fairly cheap. I'll update my build tomorrow with pictures of where i'm at. if you have any question just PM me.
Levi