# chainsaw mill engine/ideas



## Devon7234

Im starting to draft some chainsaw mill ideas. Ive got access to a few engines that are in good shape; 5 HP go kart, 7 horse power lawn mower,and a 5.5HP lawn mower. Im looking to attach a 20 inch bar too. Ive been searching quite a bit and havent had much luck on the internet regarding power,hp,rpm, speed values. Though, I pulled out an old mechanics textbook from the library and did a few calculations. 5HP sounds good. ideas?


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## TexasTimbers

The 7 horse would be better provided it's in good shape. I'd love to build a 4-stroke slabber with one of the engines I have lying around. I have a Detroit 6v71 that would make a doosy! ha. Actually it's been one of my intended projects for years but I have no shortage pf them. 

If you'll be using a 4 stroke you'll obviously want to fabricate something with a stationary frame versus handheld. I might offer some ideas later kinda busy monetarily. If you pursue this I'll be watching - it's been on my list of things to do before 2050 for quite some time. 





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## jeffreythree

It would be nice to see someone actually finish one and document it. Lots of talk and started ones out there, but not many finished ones. I think the 7 is the best option since you will have to make up for 2 stroke engine speed by using a sprocket that will take more oomph. Also, 20 inch seems a little small unless you are only cutting really small trees.


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## Devon7234

gotta hit the textbooks and find some conversions. out of the two homebuilt mills ive seen online, the user`s specifications are grossly inaccurate. biggest issue im dealing with in the design is how to in fact quarter saw the logs. if im going to go through the process of building one, may as well make it fully functional.


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## bugman1954

*quartersawing a log*

One technique I've done is make the first cut through the pith of the tree before the cut is complete put a strap around it on the cut end to hold the two halves together. Then put another strap on the log after completing the cut and roll it 90 degrees. Make second cut quartering the log. You have to be moving the straps to not cut them.


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## woodnthings

*Am I all wet on this*

I don't think a 4 stroke lawn mower engine or other small HP turns fast enough, like a 2 stoke with screamin' RPMs. That's my experience with those. I've held the governator back and listened to them scream, but that's not their intended operating range. Sure you can gear them up but you lose torque to gain RPMs.
Second a chain saw mill requires more *power* to make a cut than a bandsaw mill because the blade is wider. I have an older chain saw Pioneer, with 1/4" wide teeth, but it has a lot of power. It was a 24" but I put an 18" blade on it. The newer saws have narrow blades, just like the thin kerf table saw blade, they require less power to make a narrow cut, taking out less wood per tooth.
A bandsaw mill uses a much thinner blade than a chain saw mill and may get away with a 7 HP engine, minimum as far as I can tell. The better saws start at 13 HP and go up. So I think this is mixing apples and oranges with regard to power requirements, but I could be wrong. :blink: bill


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## TexasTimbers

woodnthings said:


> I don't think a 4 stroke lawn mower engine or other small HP turns fast enough, like a 2 stoke with screamin' RPMs. . . . *power* . . . but it has a lot of *power*. . . . they require less *power *. . . . mixing apples and oranges with regard to *power *. . .


You hit upon the key Bill - but specifically it's *torque *that makes a 4 stroker king. To get the rpm's for a csm with a 4 stroke you step it up with gear reduction (larger on the crank smaller on the bar). 

I haven't built one so let me say that right off. I've been involved in the design and discussion of them many times but one thing that has always been common among most of us is the desire for torque. Torque is king in drag racing and also cs milling. The engine needs to be a vertical shaft of course because to turn a corner with a belt and pulley setup or transfer box causes too much power loss. 

Listen how effortlessly this 4 stroke lawnmower engine powers through this beam without so much as a whimper. 







Now listen how hard (and LOUD!) and how much more effort it takes a 2 stroke to suffer through a log compared to the 4 stroke. And the rpm's of the 2 stroke sound about double what the 4 stroke is turning. 







I realize there's variables but pound for pound torque really is king. Just remember a 4 stroke can get generate more rpm's through mechanical manipulation, but a 2 stroke cannot generate more torque by upping the rpm's.






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## Devon7234

I spent a good two hours today researching chainsaw mills. I still haven't come across a build that implements physics and mechanics to maximize the use of a build :thumbdown:. You would have to be out of your mind to strap a small 2 stroke engine onto some guides and mill lumber all day. I know some two stroke engines are tough, but to sustain the necessary RPM to make efficient cuts is moronic. That www.pfladsch.de guy's video below is idiotic. Is he tearing along at maybe 4 feet a minute? Regardless all I can say is if you're thinking of building one, don't waste your time on the internet looking at other people's engine plans. Stick to the engineering and physics messages boards and research all the mechanics yourself. At least this way when you run your mill you are concentrating on cutting the wood and not worrying about having the chain pop off and wrap around your neck.

I assume ft-lb of torque is generally calculated at the arbor of the chainsaw sprocket? I'm going to try to call Stihl again tomorrow and see if they have any decent technical specs. I figured if I install and geard an engine comparable to their largest chainsaw model, I can't go wrong.


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## Devon7234

hey texas, do you have a technical specs of chainsaws reference? Stihl wasnt really willing to hand over their mechanical engineering specifications. I know their best saws run at 20ish meters per second with 7hp and 10k rpm. I want to graph and derive a few equations as to find the min/max for ft-lbs torque in relation to chainspeed with regards to a change in rpm and HP. simple calculus could yield some golden numbers!


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## Daren

I might as well consolidate these threads since something like this has been discussed before. dirtclod whips out some fancy math etc. And we talk about other things to consider,might be worth a read...http://www.woodworkingtalk.com/f26/slab-mill-7401/



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## TexasTimbers

Devon7234 said:


> I spent a good two hours today researching chainsaw mills.


Do you honestly believe 2 hours of research can even scratch the surface of even basket weaving? It's certainly not enough to formulate a plan to build a csm, much less educate you on the topic to any degree. 




Devon7234 said:


> I still haven't come across a build that implements physics and mechanics to maximize the use of a build . .


The laws of physics are not _implemented_. They simply exist. Your _design _must be implemented to work as efficiently as possible within the constraints of these laws, but you cannot decide to build something hoping to force the laws of nature to conform to your design. 




Devon7234 said:


> You would have to be out of your mind . . . is moronic. . . is idiotic. . . . don't waste your time on the internet looking at other people's engine plans.



I don't understand why you're so negative rhetoric about what others have done and are doing successfully. You seem to be saying everyone who has built a csm outside the parameters of you imagined design ideas are idiots and morons, because they haven't based their designs on complex formulas and calculatins of hp/torque/rpm ratios . . . but yet you are asking for guidance because by your own admission you do not have a clue how to go about it. Furthermore, you are using technical terms in ways that frankly make little or no sense at all. 



Devon7234 said:


> . . . I know their best saws run at 20ish meters per second with 7hp and 10k rpm.


This is incorrect and is information which is readily available on Stihl's own website, plus a thousand other places on the internet. 



Devon7234 said:


> . . simple calculus could yield some golden numbers!


Maybe calculus is simple to you but it's Greek to me. But you can't present yourself as Einstein, calling everyone who uses a 2 stroke engine as a CSM idiots and morons and expect to have the red carpet rolled out. You can look at my past posts where I have always said smaller chainsaws won't hold up to heavy CSM use, and I have also said I don't even like to use my 395XP as a mill too much even though I do at my own risk. But I also use some manners in the way I say it because I know there are plenty of guys who do use small chainsaws to mill with and I don't want to offend them much less call them "morons" or "Idiots" because they are certainly not either. They are simply making do with what they have and I salute them for at least doing something other than jacking their jaws. 

You do realize what the purpose of a csm is, don't you? It is to mill wood and make lumber and timber, not to win a blue ribbon at the local Boy Scout Build-a-Rama. Maybe some guy who is milling his trees using a 70cc saw is not making the best use of his saw at first blush, but if that's his only option then perhaps he's making the best use of it after all. 

So I guess the best answer I can give you is the one you gave to yourself.



Devon7234 said:


> Stick to the engineering and physics messages boards and research all the mechanics yourself. At least this way when you run your mill you are concentrating on cutting the wood and not worrying about having the chain pop off and wrap around your neck.









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## Devon7234

Modern physics and engineering mathematics as an answer to ALL of your statements. I'm done with this thread. But I will end it with this.

Teams of engineers dedicate thousands upon thousands of hours into the design and manufacturing of a product. They can only account for so many variables. Take in account a chainsaw chain. "Will the user oil the chain properly? Will they tighten it in accordance with saw guidelines? Will they sharpen it? Will they try to remove links from it when it stretches and reassemble it with a hammer and nail? What if it gets wet and rusts?"

There are only so many variables that can be accounted for within reason. I can assure you, "Will the user strap this chainsaw chain onto a 30 inch bar attached to a 15 horse power vertical shaft engine equipped with a gear reduction/enlargement sprocket and run it at a similar RPM with similar ft-lbs of torque?" is NOWHERE to be found in the planning and production of the equipment. I really hope you don't feel as if you can compensate for your lack of physics and mathematics knowledge with logging/milling and assume you can build a safe working set-up. I'm not berating you because all of this academic knowledge is available free and you can learn it over the course of a few weeks. I guarantee after you do a bit of reading and appreciate the numbers you will realize exactly what I'm getting at.


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## woodnthings

*This struck me as uninformed as best*



Devon7234 said:


> I spent a good two hours today researching chainsaw mills. I still haven't come across a build that implements physics and mechanics to maximize the use of a build :thumbdown:. You would have to be out of your mind to strap a small 2 stroke engine onto some guides and mill lumber all day.


The owners of chain saw mills all over the world, thousands of them, do this all day long! :yes:



Devon7234 said:


> "Will the user strap this chainsaw chain onto a 30 inch bar attached to a 15 horse power vertical shaft engine equipped with a gear reduction/enlargement sprocket and run it at a similar RPM with similar ft-lbs of torque?" is NOWHERE to be found in the planning and production of the equipment. I really hope you don't feel as if you can compensate for your lack of physics and mathematics knowledge with logging/milling (real world experience?) and assume you can build a safe working set-up.


So what if they do, and someone probably will.
Real world experience and the market place will "correct" any engineering flaws in a product in no time at all. Neither engineers or consumers cannot suspend the laws of physics, the "weakest link in the chain" will be revealed. There are 3" Aramid fiber ropes pulling the largest ships in harbors all over the world with great success. Who would have thought it possible?
American innovation has always tested the limits of physics and improvements come about this way in the field as well as in the laboratory, so I don't get your point.

If someone does what you say above and forgets to oil the chain it probably will fail...operator error, as they say.So what, it happens. I've had chains stretch, and come off but never fail. If putting a noisy 2 stoke engine on the end of a 60" bar is such a terrible idea why it being done on a regular basis? Torque is torque, tension is tension and the chain doesn't know the difference between a 2 stoke or a 4 stroke.

If you want to build a chain saw mill and use what ever combination of chain or engines you want, go right ahead and post the results of it, otherwise it's an arm chair debate and will remain so. Prove your point in other words, for those of us in the real world, not the theoretical. As was stated in a previous post, the chain saw mill fills a need for a light weight, portable mill that can saw widths not practical with any other device. End of discussion....
probably not! :smile: bill


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## TexasTimbers

Devon, you make many incorrect assumptions. 



Devon7234 said:


> . . . your lack of physics and mathematics knowledge with logging/milling . . .


Whatever gave you the impression I'm devoid of knowledge regarding the laws of physics and mathematics? Because I did not choose to play along with your fantastic idea of the necessity to fill large chalk boards full of formulas and hypotheses before I mill the next log with my chainsaw? Just because someone doesn't jump in the water with you doesn't mean they can't swim circles around you. 



Devon7234 said:


> "Will the user oil the chain properly? Will they tighten it in accordance with saw guidelines? Will they sharpen it? Will they try to remove links from it when it stretches and reassemble it with a hammer and nail? What if it gets wet and rusts?"


Oh my. Who will take care of these imbiciles and idiots and morons who have been millling more lumber in their sleep than most have even dreamt about while awake? What kind of men do you think undertake such an endeavor as chainsaw milling? Men who try to impress others with endless streams of senseless gobble-dee **** and never take action? No Devon, most of the men who invest their hard earned money into such serious tools learn to take care of them. If they don't then they'll learn real fast they need to get into academia where _doing _is not a requirement. 



Devon7234 said:


> I'm not berating you because all of this academic knowledge is available free ....


:confused1: Academic knowledge huh? In the words of my good friend Bill aka woodnthings . . . _"How's that workin' out for ya?"_ :lol:

(That was one of the funniest replies I had ever seen. I still laugh when I think about it.)



Devon7234 said:


> I guarantee after you do a bit of reading and appreciate the numbers you will realize exactly what I'm getting at.


All you're getting at is my bad side. I haven't been so brutally honest with someone in a thread like this in a long long time. It's hard to reply with any kind of intellectual meat because you seem to be off in your own other world. I mean, ignorance can be fixed, and humility can be learned, but you just can't fix stubborn. 



It just dawned on me what's going one here. Man you really had me there for a while! All this while I thought you were actually serious with all this grade hocus pocus, but now I realize you're just pulling my leg. Good one Devon! I love a practical joke as well as anyone. I owe ya buddy - you got me good.  :thumbsup:





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## mrbentontoyou

i have been idiotically making awesome lumber with my chainsaw until i have the cash and more importantly space to set up a band mill, at which point i will still have to use the csm for logs over a certain diameter. I must be out of my mind! looking at my piles and stacks of lumber, (close to 1300 b/f right now) as they season, knowing that they were acquired with sweat and about $1000 of hardware i really do feel a fool. i sure do wish i had spent this entire time trying to figure out how to build a better mousetrap instead of milling all this lumber.


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