Calculating the Hp to cut with a bandsaw mill

[54Dutchman]

Is there a formula that gives the Hp required for a bandsaw mill ??? ???  I have seen one for circle mills where the rpm of the saw blade, diameter of the sawblade, tooth form, and feed rate of the wood where used; the circle mill calculation maximum Hp was limited by the tooth form in its ability to carry the sawdust out off the cut. 

[Ohio_Bill]

Dutchman, I don't know of a formula, but I have never built a mill. I have only owned factory built mills and have had from 15 hp to 42 hp on them. I can say more is better .I am sure there is an optimum blade speed and to maintain that you would have to slow down feed rate on the low hp end.

[Dave VH]

I can't seem to find the website that I looked at a couple of months ago that explains the speeds.  I remember that the band needs to be at least 3600ft-per-min, and no more than 6000ft-per-min.  I know that there is a happy medium somewhere.  The website talked about the lower the hp, the blade needs to go slower to take better advantage of what little torque you have, (that's where I'm at with a 13hp).  It read that the more hp you have then the faster you can go and still cut nice. 
  I don't know much, but I remember part of what I read, I'm sorry that I can't find that website anymore.  But blade speed and hp have to work together.  I know that it makes a difference whether you are using tires, or bandsaw wheels, (the whole rotating weight thing).
  Maybe if you told some of the other (smarter than me) guys more aspects of the design you might get some better informed answers.
  Good luck

[dgdrls]

Not sure on a "formula"  I only have 10 horse and WM builds the LT-10 with 7HP.

There are lots of small mills in this HP range.

Look this shop up,  I tend to think its more about wheel size and blade speed.

http://www.suffolkmachinery.com/

Best DGDrls

[54Dutchman]

I did find a general formula that works as long as the blade's capacity to cut (remove the cut wood) is not passed and all other factors are not changed (speed of band, knots, ect). :P
Bandmill - Horsepower

hp = fpm x doc x kf x sg x 100 ÷ 144 ÷ ade x 100

hp = estimated power required (hp)
fpm = feed speed (fpm)
doc = depth of cut (inch)
kf = kerf (inch)
sg = Specific Gravity
144 = 12 inch/feet squared
ade = arbor drive efficiency %

Specific Gravity:

Spruce = .35
Douglas Fir = .45
SYP = .47
Oak = .60

I looked at this to help choose a sawmill and the comments that buy as much Hp as you can afford made me think (dangerous thing to ponder ;D ;D ;D ;D) why ??? ??? ??? ???

[hookdrvr]

Dutchman, if your still looking, heres a formula I found.

http://www.woodproductsonlineexpo.com/content.php/677/2160/wood_products_bandmill_calculator.html

[dboyt]

Feed speed is generally the variable.  For any hp, there is a corresponding feed speed, but with manual mills, you'll learn to adjust the feed based on the width of cut, presence of knots, species, sharpness of blade, and how the engine sounds.  More power=higher feed speed.  You might consider less hook angle on blades if the engine is low hp, especially with hard woods.  It gives a less aggressive cut.

[bandmiller2]

Its kinda like the commuter rush you go as fast as you can, you should maintain engine speed and a straight cut. Low horse power works but you must slow down. Frank C.

[GeneWengert-WoodDoc]

54dutchman...

where did you find this formula?  I can see where it calculates the volume of wood removed in cubic feet per minute, but I do not see anything indicating the amount of horse power needed per cubic foot removed.  It therefore assumes 100 HP per cubic foot per minute.  I would appreciate finding how this was determined.  Also, I am curious about the term arbor efficiency.

Volume = fpm x kerf x depth of cut / 144 = cubic feet per minute

As SG is the density of wood compared to water, it is dimensionless.

Likewise, 100 / arbor efficiency in % gives a dimensionless number.

Thanks.

[charles mann]

i guess its digging up a dead horse. i would love to know too. more on the torque required to pull through the cut. which some of those figures come into play, such as kerf and wood density/ specific gravity. i want to go fully hydraulic, and the first place to start, is tq values. knowing how much tq it takes to pull the the blade determines the hydraulic motor required, then on to the pump, with enough flow/volume to feed the motor, plush drive any other hydraulics i.e. feed motor, raise/lower motor, cylinders for toe board and clamps. iv got the hp rating now, just need to find out the type of motor that has a long duty cycle and a pump that will keep up.