New mill shopping - HP

[jdonovan]

So new here, and new to sawmills.... I'm pouring over all the makers marketing materials and have a few questions.

I've probably read 300 threads now, but really haven't seen this asked/answered.

It looks like once you get to the middle of the personal sawmill range, the mills don't physically get much bigger, or handle a larger log. Some additional automation and work saving features also start to become standard, but the biggest change seems to be a larger engine.

It seems that higher cutting rates are directly tied to engine HP?

Generally speaking would 2 mills using the same blade cutting the same tree cut at roughly the same rate if they had the same HP? Or are there other factors to consider?

I know torque factors into this too, and I've been looking at engine specs, and HP/Torque curves... and diesel vs gas at the same HP behave a bit differently, but I'm just trying to get some generalizations.

[tcsmpsi]

In all honesty, I too am a bit unsure as to what degree additional HP would benefit the same mill set up.  I have seen a lot of threads where a wide variety of folks have praised additional HP, have increased their HP with praises, etc. but have not 'heard' what exactly the additional HP has accomplished.  For simplicity, in the case of a manual mill with the engine running nothing but the saw,  I wonder of the actual gain in more HP. 

My mill currently runs with a 13 HP Kohler engine.  The only times I have ever dragged the engine rpm down, is trying to cut too fast in  difficult hardwood.  Perhaps more HP would push a more dull blade through, but will/would it do so without adverse consequence? 

Admittedly, I've only been running a bandmill for 5 yrs.  However, I have been running saws of many differing types and applications for a wee bit longer.  In the beginning, mostly running 1 and 2 H(human)P saws, the fundamental application of sawing became apparent.  It the blade ain't sharp and properly set, you ain't sawing.  Might be able to force it in a tearing mode, but the cut will suffer, not to mention one's back and shoulders.  Summarily, a small fellow can saw as much as fast as a fellow twice his size and strength, all other things being equal.

I am thinking that perhaps if cutting through the middle of a log or otherwise where there is significant weight upon the blade, more HP might be advantageous over placing a few small wedges strategically.  But then, that does not relieve the pressure on the blade, which inevitably would transfer stress throughout the component structure.   All this, I can understand as being 'acceptable' in a production milling environment.

[Bandmill Bandit]

HP is a factor but hardly the only factor.

To try summarize it in a single post would be preposterous but the Forum has a lot of info that will help you.

i can tell you that the 28 HP Kohler  V twins have no shortage of  torque and are better then some of the diesels in the same power range for both torque rise and holding power. I really like my LT40HDG28.       

[Magicman]

HP/torque is what pulls the blade through the log.  Yes, larger is better.  Put a bit of reverse psychology to your question.  If you started getting smaller engines, you would quickly find that you could no longer maintain your production level.

Is my sawmill overpowered with a 40 HP Diesel? Probably.  Would I want less? No.

[Bandmill Bandit]

HP/torque is what pulls the blade through the log.  Yes, larger is better.  Put a bit of reverse psychology to your question.  If you started getting smaller engines, you would quickly find that you could no longer maintain your production level.

Is my sawmill overpowered with a 40 HP Diesel? Probably.  Would I want less? No.

Yes Magicman I am with you HP thing. Power and handling speed is the biggest reason  I want to move up the the LT50 but that will have to wait a bit yet.

I have 28 ponies pulling my band. Is it over powered? no! is It under powered? I don't find it to be. Would I like more power? Yes! would the answers be the same if I had the LT50? Absolutely!

Power does have an affect on production in terms of feet per minute of travel while in operation but MBF per day has many factors that impact it as much and some times more than HP.

[sgschwend]

Generally speaking would 2 mills using the same blade cutting the same tree cut at roughly the same rate if they had the same HP? Or are there other factors to consider?

My 2 cents worth:
There is a lot of knowledge in setting up a saw.  So if you were to assume each maker sets up that same saw the same then the HP would have an effect on cut speed.  However this assumes the saw can handle the stress. 

The deflection on the saw increases as the force on the saw increases. This cause the saw to bow out of the cutting plane; cut quality will suffer. You have read about wavy cuts, in and around knots and changes in the grain.

I would suggest you investigate all of the step in cutting.  They all contribute to the production rate and how hard one works to obtain it.  It is my opinion that certain mills are optimized for certain sizes of logs.  It would be good to know that too.

[Kcwoodbutcher]

One thing to note about saws with larger HP is that in most mills as the HP increases the diameter of the wheels increase.  I know a hobby mill runs a much smaller wheel than a production mill. This allows the blade speed to increase an thus cut faster.  A small HP engine trying to push the blade at a high speed would quickly bog down whereas a larger engine with lots of torque will keep the speed steady.  The larger HP engine also allows the mill to run a larger blade with deeper gullets which can take a more aggressive cut.

[ladylake]

 I was making a lot of 20" wide cuts in oak today that made my 28.6 HP Isuzu diesel work hard, with my old 27 hp I'd have been cutting WAY slower, diesels have more torque per HP.  Gotta like the fuel milage of a diesel, a little less than 1/2 GPH cutting 300 bf per hour in oak  all day, had excellent help.  Steve

[jdonovan]

Thanks for the answers, they generally track what I was figuring, but wanted to hear from the experts.

I need to arrange for some local sawmill visits and see some of the mills I'm considering in operation, and see the general work flow in real life.

A sawmill is a lot of money to put out  and I would like to make as well informed a decision as I can.

[bandmiller2]

Pretty much HP=production,to be efficient a band or circular saw should be fed at rate to utilize each tooth and gullet to their capacity and that takes ponies.With low HP mills you must slow your feed to not drag down the saw/band speed which can lead to diving, poor finish, and fine sawdust problems also your teeth dull faster.Sure light HP will work but not as well as a good sized engine or motor with enough torque. Frank C.

[Brad_S.]

More hp allows you to run thicker bands and thicker bands have more beam strength, allowing you to push the saw faster. The thicker bands need the larger diameter wheels to minimize fatigue from bending, that's why larger mills have larger wheels.

[MartyParsons]

Hello,
Horse power give you more options. Keeping the blade speed correct in the cut is where HP helps. It also gives the operator more options in blade thickness and hook angles.
When the 25 hp LT15 came out we did a drag race between the 15 hp LT15 and the 25 hp LT15. The 25 hp LT15 was always about 2 ' ahead of the 15 hp. Is 2' important? These are the questions you will need to ask before you purchase a mill.
Keeping the blade sawing will produce more lumber at the end of the day, week or year. The larger mills will have features or options that will improve you bd/ft per hour. Options like Debarker or mud saws may not improve the cutting speed but you may not need to change the blade as often. Options also let the machine do some of the work so you or the support crew can stay busy doing more improtant things. Like Board Return, faster hydraulics etc.
I have been working with a mill with throttle control and looking close at blade RPM changes with different densities of wood. I changed the blade speed to slower rpm and the cut improved but I got out of the power peak of the engine so when I increased saw head speed I did not have the hp to do so. Here we would need to change the engine pulley size to keep the same rpm on the engine and slowing the band speed. The problem is I wanted to increase band speed in other woods like RO.
Hope this helps!
Marty

[Kansas]

Most of your time is spent in turning the log, reading the log, returning the head, loading a log, unloading lumber, positioning the head. Percentage time spent actually cutting is small. On our other mill, they insisted putting a 100 horse motor on it. With a 2 inch band, I think its way overkill. I don't know that it actually hurts anything. Just more weight to move back and forth.

[tcsmpsi]

In making wider cuts, this is where more hp I can see as a more plausible benefit.  In cutting wider wood, as well as the more difficult hardwood, though it generally takes a slower feed (as determining hp only benefit), I find that putting in a new blade, increases that significantly.  Though my mill is a manual feed, with some woods, if I put in a new blade, I have to hold the feed back (certain differences in density, grain, etc.  Now, when it is a matter of increased HP and increased RPM, then certainly the speed difference becomes notable (removing wood from the cut faster).

And, as has been stated, 'would I want less hp than I have'?.....Nope.   ;D

There again, it is what a person needs for their use, weighed out with the initial financial burden, maintenance cost (time and money), blade cost, etc.   I am looking at getting a new mill works head as a spare, for I know the time is coming, since I have replaced nothing on the mill thusfar, other than typical maintenance, for a nice, time-consuming rebuild.  In the last 5yrs, I have cut a bit of wood.  Plus, they have upgraded my mill some (different guide roller adjustment, more variety of hp  ;D, and 30" steel band wheels).  I have studied quite thoroughly, and my set up works very effectively and efficiently for my needs...so far.  There is always the possibility I may be pulled more toward milling as its own financial input.  Then, I would certainly be looking toward the most effective/efficient for that.

The notable majority of my milling is with less than 16" diameter logs.  Certainly, if I could order up 14" end to end, nice straight logs, that would be my optimum, as a 1 human power log turner.   :D

[Chuck White]

Happy Birthday Frank


I think that the efficiency of a mill starts to go away at a certain HP.

In other words, you can add a larger HP engine, up to a point, then when you add too much HP, the profits seem to decrease.

Do in part to greater fuel consumption.

[rph816]

I noticed a decided difference between the 15 HP TK1220 and the 25 HP TKB-20.  Both run 1.25" blades with similar cutting capacities, wheel diameters, etc.  I know that blade quality/sharpness and setup will be a big determiner of cut speed and quality but you certainly would do better to have some extra power.  I would say anything less than 15 HP is just slowing you down.  25-40 HP is plenty unless you are stepping up to bigger wheels and bands. 

Ryan