Speed up band?"

[Swede]

My "Amerika-Sågen" has a Vanguard 18hp engine. I can´t find the torque any longer at B&S site.
The band speed is now 24M/s (75 f/s.) with engine at 3400 r/m. I want to slow down the motor, the torque will be the same.
The kerf would never be more than 24" wide and normaly less than 12".
My engine newer slow down but when sawing a 5 years old oak I could hear it work in a kerf  18" wide.

Some says 20 M/s is right when sawing in bark. The blade dealer says 27-33 M/s is right in Wood. The Russian sawmills is speeded to 50 M/s with the same blade. (Suffolk silicone steel or Munkfors, 11/4",  P3/4")

How fast do you run your blades?

Swede.

[raycon]

I think mine are going 4000 feet per minute. I push my mill to the motor bogs then back off a hair.

My understanding is the less time in the log the longer life for the band.
Someone wrote/said that until you get to 24hp or so gas engines that the motor is what is slowing everything down. Feel your saw dust is it hot -- I can't even get my band hot (unless its in a knot or destroyed). Once the gullets on the band are packed then you have to back off on feed I'm no wheres near that. (Gullets pull the sawdust out of kerf - there is probably some sort of feed rate,band SFPM,gullet size  ,cant size, tpi chart somewhere --then again maybe not)

I'm looking for a bigger motor as I write this. I don't think you want to slow the band down.

[Swede]

Ray. Once I get smoke from my band, sawing the 5 years old oak logs. The band was dull and the the wheel (1 of four) that feed the saw begin to skid on the rail when I forced the feeding.
I know how dangerous it is to take sawdust in my hand ( if the band breake) so I try to avoid it. The few times I have taken the risk the sawdust have been lukewarm.

It sounds probable for me, less time in wood is best for the blade.

Swede.

[Swede]

........and i don´t want to slow down the band speed. I want to speed it up in relation to the engine´s speed!
But do i have enought torqe?
Do I get better production?

Why does somebody need 42hp. and in what logs do you make use of all that power?

Swede.

[EZ]

I tell my wife I need more power, she says why, I tell her more power means faster blade speed. Faster blade speed means faster sawing, faster sawing means getting done sooner. She told me I work to hard now, why would I want to work harder. Sometimes she just dont understand.
EZ

[Swede]

EZ  

Tell her about it when she wants a new vacuum cleaner!  

Or take her with you out to the sawmill and tell her to force the production when You have some big logs.

Swede.

PS. Put a dull blade on that day!

[Tom]

Wider throats require longer bands.  Longer bands require bigger wheels.  Bigger wheels require more horse power.

I've found, since my 2nd mill is bigger than the 1st, that it also helps you to saw faster.   There is a lot of stored power in the weight of a heavy spinning band wheel.  It helps to make the entry of the blade into the log and into knots and variations in grain more invisible to the engine.  The problem is that the energy is robbed from the wheels and needs to be replaced. If you are going to replace that energy and still drive the machine at the rated speed, you need a big enough engine to carry the load as well as put the energy back.

There are other jobs on a sawmill that must be done besides sawing. These are usually electric or hydraulic and the bigger the engine behind them, the stronger and faster they operate.

To load a log with a hydraulic pump driven by a  5 horse motor, with everything running at capacity, is functional.  The job will get done, but, not as fast as loading a log with a hydraulic pump driven by a 50 horse engine with everything working at capacity.

My larger engine allows me to load and turn logs faster, and work with larger logs too. It will increase the production of a person who wishes to use the equipment to capacity.

[Swede]

Thank You Tom. Most of it I´ll eat with the skin and fur. But "a longer band........" I belived it´s the widht and thickness. Big wheels always save the band up to any size but......OK.

If I put x kW into anything I know I get the same power out in any form. Most of it I goes to the blade, some as heat, vibrations a.s.o. If I put 18 hp in 10 Kg wheels I think I get out the same as in 100 Kg wheels. Am I crazy?
If I use 18 hp for the hydraulic loglifter.....dont I need a truck to get the logs at home again?

That heavyer bandwheels holds vibrations and  other variants from the blade seems probable. But I have no  vibrations in my wheels so I can´t lose much power that way.

Next time I´ll force the feeding untill the band breaks!   Hope I can find plates for the bandguides first, in Sweden or EU. It´s a long way to Canada. Some new should make me shure they are OK.

Or can I use anything other? Can i do them my self in the workshop? In what material? Brass is easy to work up and will be a kind of bearing. :-/

Swede. *thinkin again*

[Tom]

Swede,
I'm not sure I'm following you on the engine size question.

The longer band  is to create a wider throat for the sawmill. If the band is longer the wheels should be larger too.  The purpose is to make the area above the cutting portion deep enough to be of use and also to eliminate the sharp bends created by small band wheels.  It's not just the width of the throat that is important but also the depth of the throat.  The throat is that portion between the wheels and above the cutting portion of the blade.  All of those things are accumulative to requirre more horsepower but none are necessary make a saw function.

The plates on the guides are made from a very hard material. I was told that it was a tool steel harder than a file.  I have considered using an old file to make guide plates from just to see if it would work.  I'm sure it would.

Wood shop type band-saws use everything from steel to wood for guide material.  I don't think that the softer materials would make good guides on a sawmill because of the stresses.  Wear is definitely a concern and even the hardened tool steel plates will wear.  If they wear then I don't think something as soft as brass would stand up.  

I am only offering an opinion because I haven't tried it yet.

In response to your question ". If I put 18 hp in 10 Kg wheels I think I get out the same as in 100 Kg wheels. Am I crazy? "

No, your not crazy.  As a matter of fact you may know more about this than I do.  The reason I suggest that you need the larger horsepower is for recovery

You can put the energy in the wheel with an 18 horse engine.  Then you run into a part of a log that takes the energy from the wheel.  A heavy wheel, carrying more energy, will make the tough sawing spot more invisible to the engine but once lost, the energy must be replaced.  That's when the engine must be strong enough to replace the energy lost in the wheel and  continue the cutting as well.  The Wheel is acting as a shock absorber.  I don't know how else to describe what I am thinking.

[Swede]

Tom. Energi is indestructible, the problem is to tame it again.

I´ve also heard that the plates is made of tool steel and even of ceramic. Have used plastics some time building conveyors.  Close to frictionless in right combinations and with that no wear. F. ex. Acethal/Polyethylene. But it has to be free from grain and heat.

Brass/steel also make small  friction, You have it in most engines but there is oil between the two surfaces.
Perhaps I´ll better send Menominee an e-mail! (^__^)

Swede.

[raycon]

Following along the line of thought that  energy is indestructible.

If it takes a 8 hp  powered mill 10 minutes to cut something it may take a 80hp mill 1 minute. RPM of the band wheel held constant for both.

The 8 hp will be limited by how much material each tooth can cut per pass (not enough cutting force to fully utilize the blade - thats why a thinner band is recommended--puts more force in the cutting area --and the 8hp is not strong enough to damage the band ?)  and the 80 hp may experience limitation cause it can't evacuate the sawdust fast enough to allow a higher feed rate (gullet size).

Tom, sounds like you were describing an inertia wheel or flywheel a few posts ago.

I don't understand the question but I know I want more HP and if I used the vacuum analogy with my wife I'd be vacuuming not milling this weekend.

[D._Frederick]

I don't think that the band wheel are made heavy to store energy, a 200-300 lb. wheels would not have enough stored energy to hardly cut a revolution  of the band on a portable bandmill. They are made heavy so that they do not warp from the applied pressures.

[Tom]

Perhaps energy is indestructible but it can certainly be transferred to a place where you can no longer use it.  The energy in the engine is put into the wheels.  It is no longer available from the engine.  The engine must create more.

The energy from the wheel is transferred to the blade from the wheel when the blade contacts the wood.  That energy is no longer in the wheel and must be replaced.

If you disconnect the engine from the wheel then the blade will only cut wood as long as the wheel is able to spin.

If you reconnect this wheel to a smaller engine while it is still cutting, it may be able to continue cutting at a reduced capacity but the energy that the wheel had stored would never be replaced.

If you reconnect this wheel to a larger engine while it is still spinning, it will not only continue cutting at the original pace but the energy lost from the wheel would be replaced and there may even be some energy from the engine to spare.  That extra energy could be used for other jobs.

The energy that is in the wheel can be tapped much quicker than a governor on an engine can respond.  The governor on the engine can provide the power to saw at a certain speed but the momentum of the wheels can take some of the time lapse from the energy loss by providing instant power to get through a small tough spot like a knot.

Speeding up the band may or may not increase the ability of the band to saw properly.  Dropping the rpm's on the engine may decrease the available horsepower and decrease its responsiveness as well.

When Woodmizer first came out with their diesel powered mill it was run against an LTf30 and LT40 in a production test.  Both the LTf30 and LT40, with 18 and 24 horse gasoline engines,out-produced the larger diesel engine.

It was explained to me at the time that the more powerful diesel was over-running the blade.  I'm not sure what that meant but I have a feeling that they were running the blade faster to cut faster rather than cutting within the design spec's of the blade. It's how you use that energy that makes saw perform.


My wheels are 200 and 300 lbs respectively and  do carry enough energy to make a difference in the way the saw behaves in bad wood.   It must retain enough energy to carry the blade through at least one revolution and maybe more in normal situations.  While I don't have the instruments to measure it I have stuck the blade into a log without the engine powering it to see what will happen.  It will cut to a depth as deep as the blade width depending on how much pressure is applied.

[D._Frederick]

Tom,
I guessed about right, I figured that there would be enough kinetic energy stored to make one revolution of the band and would cut a band width. You are correct that the flywheel effect would be great enough to allow the engines governor to catch up on the energy demand. It results in a more constant rpm.

[Swede]

Ray
" if I used the vacuum analogy with my wife I'd be vacuuming not milling this weekend."  
http://www.forestryforum.com/cgi-bin/board/YaBB.pl?board=sawmill;action=display;num=1076061405;start=40;) Why don´t You this?

Tom, D._Fredrick; I´ve get that poits. Sorry for a possible language barrier. Now I´ll try to give you the right questions.

My wheels are Ø20", throat is 26" and this is all I need for the logs here. Logs is softwood and the kerf would never be more than 24" wide and normaly less than 12".
Now i run the engine at 3400rpm/17.5hp. The torque is about the same at 2700rpm but the hp is only about 15hp.
 

My engine newer slow down so what I´m actually asking for is:

1. What (good or bad) consequences would a transmission making higher band speed in relation to engines rpm. make.
2. What is the band speed at other saw mills and what´s then their engines torque and hp?
3. What should the power between 18 to 40hp make at my sawmill and my logs.

I think "marketing a new sawmill" not necessarily gives the same advices as practical experience and basic knowledge in this questions. However all advises are valuable.
And I´ll try to feed faster sawing next time, with or without new plates in the guides.

Swede.

[EZ]

Dont know if you guys can make any sense with what I'm about to say, I myself still dont understand it.
Years ago when I was racing in the 1/4 mile, I had a 396 big block that I built to the max, it was pushing the high 7 seconds. One winter I was rebuilding the transmission(auto) and came across an artical in a magizine about heavier flywheels. I turn a new flywheel and made it 9 lbs heavier than stock, the only thing I did with the trans. was replace the seals. That summer I ran the low 6's all summer.

My brother-in-law has a jeep with a beef up v-6 in it that he uses it for sand drags. I told him about the flywheel thing and he turned one that was 4 lbs heavier than stock. He put it in and his racing was, well you could run beside the jeep and keep up with it. Note, he was'nt a happy camper.
Like I said before, I just dont understand it.
EZ

[Fla._Deadheader]

 Hey Swede

I ain't no injuneer, so, I won't go into fisiks.

 This hear flywheel deally is purty simple. When y'all gots LOTS of power a flywheel can keep up the top speed of the enjin, whilst the enjin is squawlin an eatin up them logs.

 When the enjin is heavin it's kidneys tryin to keep the flywheel rotatin, thar ain't nuthin left to eat logs with, so ya gotta eeeez inta them there logs. Speed only counts when ya gots power.
 That's all I got ta say about that

[C_Miller]

I changed the pulley size on my 18 HP Briggs IC.  the blade speed increased and the feed rate increased but the engine spends more time in the governer so my gas milage went down.

I cut mostly smaller pine so it doesn't bother me to much, but for bigger stuff you need more engine. I'll probably go 25 HP when this one gets to tired.

C

[Neil_B]

Seems there is some controversy over blade speed. Not here but with the manufacturers.

I've been playing with speed to try and get my mill sawing better. I was in contact with a Lenox technician and they recommended 7000 sfpm on their 2" blades. Suffolk recommends 6800 or there abouts.
Now the controversy starts with the most recent Cook's sawmilling news. I had the URL but can't find it to post. Anyway, they are saying not to go over 5800 with the 2" blades, they also have speeds for the smaller blades, because you are losing available torque.
Now I'm really confused. I'm not sure what direction to take now cause it does saw a bit better at the higher speed. I'm now up to 6500 sfpm on mine. Only problem is that I changed the driven pulley and I'm sure it makes it harder to get everything started up to speed with a smaller driven.

I've got to upgrade to a heavier clutch on my unit so I'm thinking of going to a  bigger pulley on the clutch as opposed to a smaller driven pulley.

[woodmills1]

A flywheel acts as a moving mass to provide rotational inertia.  On a one cylinder 4 cycle engine it is absolutley necessary to allow the piston/rod/crank to make it around for the cycle to get to compression again.  The flywheel also tends to smooth out the delivery of power to what the engine is driving.  Most of the above posting is correct.  A flywheel too small for the application will not have enough inertia to let the motor work through when all of its power is required, however one that is too large makes the engine work at nearly full power just to keep it rotating.  With that torque monster 396 a bigger flywheel allowed for better initial application of power and I bet that thing really hooked up and launched from the line.  Small block chevies and V-6 engines tend to get their better power at high RPM so must work harder to keep that bigger flywheel rotating.  Trying to make that jeep move and the sudden hook up drags the motor down below its power band and it bogs out.

One more thing
linear momentum is mass x velocity

angular or rotational momentum uses another quantity called moment of inertia which  not only concerns mass but also the radius of the mass that is rotating.  Its symbol is I that is capitol eye  
It also involves angular velocity which is measured in something like RPM or degrees per second rather than something like MPH or feet per second.

angular momentum is moment of inertia x angular velocity

The reason I bring this up is because of the way  moment of inertia is calculated. It is somewhat confusing but in the simpliest case it is mass x radius squared.  Meaning  more mass makes more inertia but larger radius makes more inertia by the square.