And another sawmill build thread...

[ljohnsaw]

I have a cabin build thread going (no building yet, just moving dirt and such) where I mentioned I was building a sawmill (bandmill).  So, here is the official build thread...

I started my build quite some time ago (almost embarrassed to say close to 2 years... ).  I made one set of track (16') and cut the material to make two more (16'-6" and 8') that will plug into each other giving me a total cut length of around 35' that I need for some massive beams that will be spliced together to make five 54' beams.

I've posted this picture before - this is the bed/track I've completed so far.  The rail is 2x3x¼ angle iron sitting on some #5 'C' profile iron on 2x4x¼ box beams.  The jacks are 2,000 lb rated that I got for free from a friends scrap (12 of them).  The log stops and dogs are not installed in this picture.  The log bunk design is borrowed from another FF member's build.
 

 

DISCLAIMER: YES, I will install blade guards!

So here is the head.  I had to suspend it from my ceiling joists in my garage to lay it down to remove it.  It stands seven feet tall and my garage header is 6'8"   It is made from a salvaged computer rack (uprights) and some salvaged 2x2 thin wall frames that were originally 4'x8' but I made them roughly 2'x8'.  This is a vertical mill - you can cut the trees while they are still standing 

  

Setting it up on the track

 

I salvaged some gearing from some large rolling file cabinets that were being thrown out at my old work.  Combining a bunch, I made this hoist setup.
 

 

  

The head is pretty darn heavy so I added a "tool balancer" that has about 40lb of lift, running through the block giving me 80+lb of lift.  It is the white thing hanging at the top with the ¼" cable.  I have a smaller 25lb one on the other side.  If I let the hoist go, it will descend slowly.

 

I have a 2.5hp treadmill motor running it.  I cut a double V groove (to match the pulley installed on the back of the tire rim) in the flywheel.  It measures out a 8" and is turning the 14" pulley attached to 21.5" doughnut spare tires.

 

 

I parted out a scissor jack to make the blade tension system.  The hubs are from the rear end of a front wheel drive Toyota.  They pivot to adjust tracking and a small bolt sets the angle (on the wheel side).  The blade tracks really well.

 

 

More pictures to come.  I just noticed I didn't get the blade guides (home made).

I had picked up a redwood tree (three 8-9' lengths) a while back and they have been paitenly waiting on my mill build.  They ended up getting a little dry rot but were a good exercise for my mill.  It cut true (though not completely square) with no wave.

 

Issues:  I designed the drive system ratios because of what I read about blade speed.  My calcs were based on the need for about 60mph (5,000 fpm) top end.  I used the motors top rated rpm.  I haven't had the guts to run it flat out yet.  My ratio gives about 4.26 times the speed the tread mill thinks the old belt is moving.  The tread mill maxes out at 10mph, or tire speed of 42.6mph (3,750fpm) blade speed.  I've run it up to 5.5mph (6 once or twice).  It cuts quite well at that speed but starts to bog down.  The logic in the controller doesn't want to make quick adjustments (for safety of the runner), so it has a bit of trouble catching up if I bog it too much.  If I keep running at 4.5 mph or better, it keeps up until it pops the circuit breaker on the controller (15amp).

Several times, it has gone into a runaway mode - not sure why.  It will just keep getting faster until the breaker pops.  It usually pops about 6.5mph (~2,500fpm).  But it sure cuts fast when it is moving that fast.

Options:  I like running on electric and have a couple of options.
1) I could redo the ratio to halve the tire speed so the motor will need to run faster giving more torque.  I think that will solve the bogging and circuit popping issues.
2) I might have a DC controller that would work for this motor.  However, it wouldn't have the feedback loop to try and maintain a set speed.  I would have to "play it by ear" when cutting.

Option 3 would be to install a 7hp gas engine I have laying around (I think it runs).  While this would make it completely portable, it would be heavier, noisier and I would need to rework the belting ratios.

Comments or suggestions?

[Kbeitz]

You could make a cheap fixed one speed DC power supply for your motor.
And if you still need more power you could hit up the junkyard for another motor and have two
mounted at the same time.

[thecfarm]

Sounds like it cuts good.

[Magicman]

   You have lotsa hardware in that build.

[ljohnsaw]

The DC controllers that I have are only good to 1hp so no-go on a replacement.

Here is the blade guides.  The idle side only has to do a little down pressure because when I redid the blade tension setup, I move the idle wheel down a little.  Those bearing stay nice and cool.

 

 

The drive side has a bit of down pressure and the bearing does get a bit warm.  When I start running coolant, it will be getting a good bath and should be ok.

 

 

The red handles lock the side to side movement, bolts lock the tilt angles and in/out against the blade movement.

Update on operation:  I ran the unit up to to speed.  When it hits 7.1 mph (treadmill speed), the 15 amp breaker pops so there is not enough power to run the mill in the current configuration.  I was able to set the speed to 5.5 and keep it going (bogging down) to 4.5 or so.  That let me cut some boards from the 8' redwood log.  It took way too long - the treadmill console has a timer on it - one board took 6 minutes, the next about 5.  As Tim the Toolman would say, "more power!, Arrh arrh arrh".

I'm planning on mounting up a 7hp Subaru engine from a power washer and see how that goes.  I'm using 1.25" Woodmizer blades - any recommendations on the blade speed with this size engine?

[Ox]

Pretty impressive build, I must say!  I think going to the gas engine will be better for now but I think you'll still want and need more power for any kind of efficient milling.  I bought a Honda clone from Harbor Freight, the 13hp 420cc engine and I'm very happy with it.  Those engines now have raving reviews and I agree.  With the 20% off coupon and 2 year replacement warranty with no questions asked it came out to around $380 if I remember correctly.  I realize that it's easy for me to spend your money but I'm just sharing what I know to work well.  They also have at least a 5hp electric motor there for around $200.  I actually had an employee tell me that when the two years is about up to just blow the engine up and come back and get a new one.  Can you imagine?  My conscience wouldn't allow me to do that and I said that.  He said that's what all the contractors around there do.  I just politely shrugged it off and continued on.  Kbeitz's idea of running 2 motors together would be easy enough to do and would probably work just fine as well!

[Kbeitz]

I got a 13hp Honda engine on my homemade mill. My band wheels are 17" dim.
My ratio is 5 to one . Hope this helps.
Note.
I need to run WOT so I don't get waves. So maybe 4 or 4.5 to one might be a little better.
I wont change my mill because it's working great at WOT.
Maybe someone can help me out. I not the best with math.
But the way I look at it my blade is running at 4533fps.
3200RPM engine speed  X 17 inch wheel  divided X 12 to get feet = 4533... Right

[Kbeitz]

I got a 13hp Honda engine on my homemade mill. My band wheels are 17" dim.
My ratio is 5 to one . Hope this helps.
Note.
I need to run WOT so I don't get waves. So maybe 4 or 4.5 to one might be a little better.
I wont change my mill because it's working great at WOT.
Maybe someone can help me out. I not the best with math.
But the way I look at it my blade is running at 4533fpm.
3200RPM engine speed  X 17 inch wheel  divided X 12 to get feet = 4533... Right

Opps... Wait... I think I forgot to also divide that by my 5 to one ratio.
That would take me down to 906 FPM

[Kbeitz]

Wow... I never looked at my speed before... My speed looks slow...
So I googled it and came up with this...

Here are some guidelines: 8 hp max speed 3,500 fpm, 12 hp max speed 4,000 fpm, 16 to 18 hp max speed 4,500 fpm, 25 hp max speed 5,000 fpm, 30 hp and above max speed 5,500 fpm.

off this link...
https://www.cookssaw.com/index.php/increase-portable-sawmill-profits-a-production/how-fast-should-a-bandwheel-turn

I cant beleve my saw cuts so good. Unless my math is off... Anyone want to check ?

[ljohnsaw]

The 7hp motor I have I received from my neighbor.  He hadn't run it in a number of years.  I found a gas tank with a bit of water and tons of rust.  The carb bowl was packed with rust and the fuel cutoff valve wouldn't budge.   I happened to have parted out a Honda lawnmower (bent crank) and saved the carb.  It fit but is rotated a little.  Rebent the governor linkage and it fired right up (once I turned the gas valve the right way! )  Only problem is the linkage is backwards, wants to run flat out!  But it runs

[gww]

Kbeitz
The forum caculator has you at about 3000 fpm =/-.  It is located at the toolbox icon at the bottom of all the adds on the left of your screen.  It does the math for you and for me and I would be losts without these types of caculators.
gww

[Kbeitz]

Kbeitz
The forum caculator has you at about 3000 fpm =/-.  It is located at the toolbox icon at the bottom of all the adds on the left of your screen.  It does the math for you and for me and I would be losts without these types of caculators.
gww

Thanks...,  But thats not going to work for me ...
My system has a jack shaft so I have 4 pulleys .
That program uses 2.

[gww]

K
Got you, well that takes me out of the ball game,  Member "Stroker" figured my jackshaft speed out for me.
gww

[Den-Den]

I got a 13hp Honda engine on my homemade mill. My band wheels are 17" dim.
My ratio is 5 to one . Hope this helps.
Note.
I need to run WOT so I don't get waves. So maybe 4 or 4.5 to one might be a little better.
I wont change my mill because it's working great at WOT.
Maybe someone can help me out. I not the best with math.
But the way I look at it my blade is running at 4533fps.
3200RPM engine speed  X 17 inch wheel  divided X 12 to get feet = 4533... Right

3200 engine rpm / 5 to one ratio = 640 wheel rpm
17" dia wheel X 3.14 / 12 = 4.45 ft per revolution of wheel
640 rpm x 4.45 ft/rev = 2848 ft/min
Assuming that I understand your rig.

[Kbeitz]

I got a 13hp Honda engine on my homemade mill. My band wheels are 17" dim.
My ratio is 5 to one . Hope this helps.
Note.
I need to run WOT so I don't get waves. So maybe 4 or 4.5 to one might be a little better.
I wont change my mill because it's working great at WOT.
Maybe someone can help me out. I not the best with math.
But the way I look at it my blade is running at 4533fps.
3200RPM engine speed  X 17 inch wheel  divided X 12 to get feet = 4533... Right

3200 engine rpm / 5 to one ratio = 640 wheel rpm
17" dia wheel X 3.14 / 12 = 4.45 ft per revolution of wheel
640 rpm x 4.45 ft/rev = 2848 ft/min
Assuming that I understand your rig.

You got it...
I forgot to do the X 3.14 ...
Thanks.

[Ox]

Did you guys notice me over here in the corner silently nodding my head in solemn agreement as if I knew what you were talking about?

Numbers... 

I'm very glad there's so many capable members on this forum.

[Den-Den]

ljohnsaw:
Very nice work on the fabrication, you have spent some time on this.  You are seriously underpowered with the treadmill motor.  It probably could be made to work but your fabrication efforts deserve a bigger, better motor or engine.  Whatever power source you end up with; you need to match the power with band speed.  Two guys have cut big logs with a pit saw, that is less than one horse power.  The blade speed of a pit saw is no where near that of a commercial bandmill.  Lower power needs lower band speed so that the power is not wasted on friction and making fine dust.

[plowboyswr]

Did you guys notice me over here in the corner silently nodding my head in solemn agreement as if I knew what you were talking about?

Numbers... 

I'm very glad there's so many capable members on this forum.

  my wife refers to me as a human calculator. 

[Ox]

Plowboy - I surely am envious.  Being good at ciphering would make my life quite a bit easier.

[ljohnsaw]

I'm waiting on some dual v-belt pulleys - should be in by Friday. 

I redid the linkage on the replacement carb and the 7hp engine runs as it should.  Has a nice low, smooth idle and a solid top end.  I changed the oil once it warmed up - wasn't too bad for sitting so long.  I pulled the electrics off my mill and was surprised.  I forgot how heavy the tread mill motor was!  I think the gas engine is lighter!  I mounted the gas engine, added a throttle cable over to the operator side along with an additional cut off switch.

Now I need to make a pulley on a lever to engage the belt for a positive engagement.  The single grove clutch I have is too small of a shaft diameter anyhow.  And make the blade guard.  And, according to may son, paint it all the same color