Home built bandsaw mill

[jmc]

</font><font color="blue" class="small">( calculating roughly, taken the saw band blade is 3 centimeter wide and the projected bearing surface (equals the wheel diameter) is 55 cm, and the pressure is 2.75 bar (2.75 kg per square centimeter) the max. strain that the tire could put on the saw blade would be 8318 kilogram... I assume /forums/images/graemlins/grin.gif that 8.3 metric tons will do the trick here...)</font>

Renze,

I think a lot of that calculated force is soaked up in stretching the sidewalls of the tire and, therefore, never reaches the blade.

Probably, if you ran that same calculation on the total force in 4 car tires that support the weight of the car, the car's weight would be so small in comparison that there should be almost no tire deflection. Yet the tires do compress because most of that pneumatic force is stretching the sidewalls. (I think.)

John

 

[Renze]

JMC,

Yes you're correct... but i said "rough calculation" and didnt mention the word deflection... Anyways my point was made, a tire is able strain the blade more than what is healthy for it... Anyways in practical situations that much tire deflection wouldnt be wanted because it will soak engine power. With a more realistic stretch on the saw blade, lets say 100 N/mm2 the 2.75 bar inflated tires can do their job without excessive power soaking deflection.

About the car tires, the projected bearing surface of the tire, if there was NO deflection, would be theoretically just a pencil mark as long as th tire is wide !!
As soon as the tire starts to deflect it will get more projected bearing surface.

the band saw blade bears on a projected surface of 55x3 cm is 165 cm2
The tires i was talking about are exactly 165 mm wide, which is 16,5 centimeter. that means that the saw blade has the same projected bearing surface as a tire that deflects untill it gets a 10 cm long flat end on the ground... A car would be difficult to steer at 50 mph with that contact area...


So 5 hp isnt enough, and with 15 hp you have more than enough ?? would a 10 to 12 horse engine be the optimum between hp and sawing capacity ?

 

[KYErik]

I think a 10 hp electric would have enough power, but I'm not sure that a 10 hp gas would have enough. From what little I understand about electric motors and gas motors is this, a 10 hp electric motor can do the equivalent work as a 15-20 hp gas motor because the electric motor can be overloaded slightly whereas the gasoline hp value is absolute maximum at wide open throttle.

Anybody else out there heard of this? Or maybe I have been misled into thinking this...

I now have a 220 volt 1 hp electric motor on a front tine garden tiller. It seems to till just about as well as when it had the original 3 hp gas engine on it. The electric motor has overload protection but I never have tripped it while tilling. It does take a bit of planning to make sure that I don't hit the power cord while tilling /forums/images/graemlins/shocked.gif

 

[Renze]

You can compare electrical motors to tractor engines: they are made to deliver 100% of power for extended times. truck engines can deliver 75% of their power continuous, while passenger car engines are 50%, according to John Deere Mannheim R&D. (i've read this in The Furrow, JD sales lecture)

Small gas engines arnt build to be loaded 100% continuously.

Hey i have another question about band saw blades, how long does it take before they need resharpening, and can you resharpen them with an angle grinder mounted in a special jig ? How much do companies ask for sharpening a band blade ?

How often do they break ?

and compared to chainsaw mills, wouldnt you wear out a lot of chainsaws in short periods of time when you make so many hours on them ?

I read the pros and contras for, and against band saw vs circular saw vs chainsaw mill and i decided to think about it a little more and hear people's advice /forums/images/graemlins/smile.gif

 

[Clyde]

Renze - Depending on the amount of dirt embedded in the log, a person with steady sawing could possible expect 4 hours on one blade. Push a dull blade beyond that and you will start to experience wave and heat buildup on the blade. If I'm doing alot of custom sawing and my blade supply is getting low, I send 15 blades at a time to Woodmizer for resharpening. I usually run an inventory of 250 blades. I have an agreement with Woodmizer that if the blade, determined by width of the blade and the number of teeth missing, they automatically replace it and charge me for a new blade. Price per blade and with shipping equates to around $8.00 per blade. Price for a new blades plus tax and shipping equates roughly to $23.50 per new blade. I did buy the Woodmizer sharpener and setter with the machine and I still use use it in my slack periods. The sharpener has a disc that the sharpener follows and it runs across the entire profile of the blade. Small stress fractures are ground out this way before they become a source of failure to the entire blade. The setter allows me to set my own pitches for frozen wood, soft wood, fibrous wood, or hard woods like dry oak. Incidentally, green wood is preferred to saw over dry logs. I find that after 4 sharpenings, a blade will probably break during that period. With 2,600 lbs of tension, the blade breaking is like an M80 going off as the entire head assembly is relieved of this tension. Then you toss the blade, put on another in less than 3 minutes, and off you go again. With over 9,000 hours on my machine, I think I've seen most of the problems one might encounter. I'm always interested in seeing another manufacturers machine actually sawing. I seldom see ways that Woodmizer could have made theirs any better but sometimes I do. Hope this answers some of your questions. - Clyde

 

[Renze]

Thanks, Clyde ! So here is some more rough calculating from the numbers you mention:

4 hours per sharpening, 4 sharpenings before they snap, is 16 hours on a blade. 4 sharpenings at WoodMizer cost 8 dollar x4 is 32 dollar. The new blade costs 23.50 plus 32 dollar for sharpenings is 55,50 dollar for 16 hours of sawing. which is about 3.47 dollar per hour.
That doesnt sound too bad.

What's the life expectancy of a chain saw ? when i have my chains cut at the local smith i will pay less and the chain lasts longer. I estimate the cost of chain, and sharpening will be half that of the woodmizer.
But how many engine hours can a chainsaw engine make ? 250 ??? what's the price of a new chainsaw ? and how much higher are the fuel costs for a 2 stroke engine vs a diesel ?

I think i need to get in touch with woodmizer Germany for sawblades...

 

[Renze]

Oh one more question:

How wide are these sawbands ? I have contacted a professional tool sharpening company. They say they can sharpen band saws up to 30 mm wide.

I think it's cheaper to have them sharpened locally than sending them back and forth by mail every time...

 

[KYErik]

Renze,

I originally thought of building a chainsaw mill, but the thicker kerf (cut) of the chainsaw chain will require more hp or really slow down the cutting speed.

I believe that my blades are 1.25" wide (this includes the tooth).

 

[KYErik]

Chainsaw engine fuel consumption- I would guess that a 2 stroke chainsaw engine would burn at least twice as much fuel as a diesel engine doing a simular amount of work. Add the extra power needed for the wide kerf and it would probably be closer to 4X the amount of fuel that a diesel would burn driving a thinner bandblade.

A "nice" chainsaw (Stihl etc.)with a 24-30 inch bar would probably be around $500-600.

 

[Clyde]

The most common Woodmizer blade is the 1 1/4", with a .021 tooth set. Left, right and the raker tooth. Blade thickness is .045". Woodmizer is constantly testing new blades with the higher powered engines they are now running. Right off hand, I don't know if there are any Woodmizer Resharp centers available to you without the shipping charges putting you into bankruptcy. I'm sure there are very competent sharpening shops that could do this for you. If you have ever watched a sawmill sharpen their bandsaw blades, you might have noticed that the grinding wheel touches every profile of that blade. This helps to grind away fractures in the metal that are just starting to form. Another option for you would be to keep your eyes on Ebay for a used blade sharpener and also the setter for the tooth pitch. A properly sharpened and set blade leaves no saw marks in the board - just a sort of fuzz from the wood grain as it ran other than parallel to the blade. I have tried other blade manufacturers blades and every one of them had some good things/bad things but the Woodmizer blade outlasts all of the others. Best of luck to you and keep asking questions if you have them. Clyde