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Hammered RPM

Started by bandmiller2, June 26, 2008, 05:50:40 AM

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bandmiller2

Do any of you guys know how much leaway in RPM is allowable in a headsaw??Say your blade is hammered for 600 rpm could you do 550 to 650 without too much trouble.Is it better to be a little over than under,or do you have to be right on.Thanks Frank C.
A man armed with common sense is packing a big piece

bigmillman

I asked this same question to the man who hammers my head saw:  I can run my head saw with a diesel engine (UD 14) at 600 RPM or a steam engine at 500 RPM and he said that is not a problem.  He said the higher the RPM the more critical it is too keep the blade at the proper speed.  Some of the big mills around here run their head saws much faster than what we are talking about.

Take Care,
Stacey Freeman
Freeman's Mill

BBK

We always ran 550rpm. The sawdoc ( Piper Saw in Central City Kentucky) always said we were good for 50 rpm over/under.
I love Farming, Logging, Sawmilling, Fishing, and Hunting.

Ron Wenrich

I think the saw performance would depend on how you saw.  Although my saw is hammered for 690 RPM, I know I lose some rpm under load.  How much, I don't know.  I do know that the drop in RPM is dependent on log size, hardness of wood, log quality, and the condition of your saw teeth.

I've seen some sawyers that nearly hang a saw trying to keep up with some mythical feed rate.  Their RPMs drop, and the saw lays over.  That opens the saw and it heats up and the problems get worse.

50 RPM over/under sounds like a good number.  You just have to put the other factors in there as well.
Never under estimate the power of stupid people in large groups.

Tom

.......and therein comes some of the "Art" of being a sawyer.  :)

amberwood

good timing on the subject. I am looking at building a small circular saw, with 20-36" blades. How do you  determine the correct arbor/tip speed? Is a there a rule of thumb?

DTR
MS460 Magnum
MS250
DAF CF85-430
ASV RC-85 track loader

bandmiller2

DTR,according to Lunstrum you should have 8000 to 9000 feet per minute rim speed for hardwood and 2000 more for softwoods.That seems a little high to me of course thats for production mills.Tell us what your planning may be a problem finding a blade that small most that size are for cordwood saws and cross cut.Usally around 40" is as small as your going to find inserted tooth headsaws,those are for Belsaw mills.Frank C.
A man armed with common sense is packing a big piece

bandmiller2

Milling always seems to be a seat of your pants operation the books will get you in the ball park but fiddle dee dee gets you right on.Nice to know theirs some wiggle room if the blade seems to lay over, up the speed a little ,if its starts to look a little snakey try slower.Every mill I've ever seen the blade slowes down some in the cut you'd have to have a really big honken diesel to do outherwise.For chuckles i may put a tach on the mill I'am building to read arbor speed.Frank C.
A man armed with common sense is packing a big piece

amberwood

It is bit of a "special". I have good access to small diameter, 6" or 150mm pine log, and have some market for 4"*4" heart in cant. I am considering building a very small twin saw, or half a quad box, twin blade scragg etc etc. I have some 19.5" blades avail ex 8" Lucas Mill, or can upsize to 32" off the Mahoe main wheel. Both proven blades that are readily available and easily retoothed/repaired.
I have looked at commercially avail saws and they are just too much machine or too much $$ for the product I am now considering. A larger unit that could process log up to 350mm would be ideal but again $$ really kicks in.

It would be a two pass process with a return belt, sharp chain drive. The over-riding factor is the amount of power I have available. I am capped by an 80kva genset, and that pretty much limits feed speed or blade size.

19.5" blade running @ 2850rpm direct coupled to the drive motor runs a tip speed of 14500fpm.

Any input greatly appreciated.

DTR

MS460 Magnum
MS250
DAF CF85-430
ASV RC-85 track loader

bandmiller2

DTR, you know what your doing ,sometimes its hard to know how far along the mill lane someone is from a few words good luck and keep us posted.Frank C.
A man armed with common sense is packing a big piece

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