why is a BSM limited to a 30 some inch log?

[headleyj]

What limits this? What I don't get is this
BSM:
- 23hp motor (optional I know)
- thin blade ~ 12' long total blade length
- max log diameter ~ 34"

CSM:
- 8.5 hp (3120xp let's say)
- wider cut with ripping chain
- you can run what....a 48" bar or bigger on an alaskan? ~8' long total length


Why with more hp and a thinner blade (less friction I'd think) can't they make a BSM capable of slabbing wide stuff like the Alaskan?

What am I not thinking of here? Thanks.

 

[BobL]

What limits this? What I don't get is this
BSM:
- 23hp motor (optional I know)
- thin blade ~ 12' long total blade length
- max log diameter ~ 34"

CSM:
- 8.5 hp (3120xp let's say)
- wider cut with ripping chain
- you can run what....a 48" bar or bigger on an alaskan? ~8' long total length
Why with more hp and a thinner blade (less friction I'd think) can't they make a BSM capable of slabbing wide stuff like the Alaskan?
What am I not thinking of here? Thanks.

The problem with a really thin narrow blade is the wider the cut the more it will wander so if you want to slab real wide on a band saw you need to use a wider and thicker blade.
But then you also need comparatively more grunt.
Look here www.garymkatz.com/ontheroad/hulloaks.htm

 

[headleyj]

The problem with a really thin narrow blade is the wider the cut the more it will wander so if you want to slab real wide on a band saw you need to use a wider and thicker blade.
But then you also need comparatively more grunt.
Look here www.garymkatz.com/ontheroad/hulloaks.htm

WOW - that blade is what a foot wide and cuts 6' diameter stuff.

so with a BSM that can cut a 34" log (bout half of 6') why isn't the blade 6" wide (bout half of the blade width on that huge sawmill)

Maybe it's not a linear relationship (log diameter to blade width)??

 

[Brmorgan]

WOW - that blade is what a foot wide and cuts 6' diameter stuff.

so with a BSM that can cut a 34" log (bout half of 6') why isn't the blade 6" wide (bout half of the blade width on that huge sawmill)

Maybe it's not a linear relationship (log diameter to blade width)??

No, there are other factors. For example, a larger blade is much stronger, so it can be run at a higher tension so the band can run faster and stay on track - you can push a lot harder on the blade without it deforming. It isn't uncommon to see those big bands running with well over 12,000 lbs. tension on them. But boy do they turn into shrapnel real fast if they break at that speed and tension! I've seen 1 square foot pieces embedded in the ceiling at one mill I used to work at.

 

[headleyj]

No, there are other factors. For example, a larger blade is much stronger, so it can be run at a higher tension so the band can run faster and stay on track - you can push a lot harder on the blade without it deforming. It isn't uncommon to see those big bands running with well over 12,000 lbs. tension on them. But boy do they turn into shrapnel real fast if they break at that speed and tension! I've seen 1 square foot pieces embedded in the ceiling at one mill I used to work at.

so in order to cut a wider log you need;
- a wider "throat" on the BSM ,which means
- a wider and longer blade, which means
- more tension needed, which means
- more hp required to push it

understand.

OK riddle me this;
why if a BSM is capable of a max log diameter of say 34", is the max board width only 24" or so?

 

[Can8ianTimber]

The real test is the throat. That is where the blade will wander. The max log size is more about how much you can wittle off in the outer round of the log while not exeeding your throat capacity. I have seen guys on woodmizers (b/c of the cantelever head) wittle down 42" logs by taking small cuts and rotating several times until the log is small enough to cut cants.

 

[headleyj]

I want the ability to slab large stuff (trees 40-48") - that's the only thing stopping me from a BSM. A helluva CSM would do it though

After the slabbing is done, it'll inevitibly (sp?) lead to posts, beams, etc when I build a barn and another shelter for the implements - hence the desire for a BSM

I really can't want to get both, pocketbook can't handle it.

 

[headleyj]

another ? ya'll may have missed:

If it can take a 34" log - why is the max board width 24"?

 

[Can8ianTimber]

another ? ya'll may have missed:

If it can take a 34" log - why is the max board width 24"?

Here is a picture that illistrates it a little better.

The cut width depends on the distance between the roller guides.
The log size depends on the distance between the saw frame.
The reason most mill makers don't make it wider is b/c they have learned that it is very hard to keep the band cutting strait at that width.

 

[headleyj]

Here is a picture that illistrates it a little better.

The cut width depends on the distance between the roller guides.
The log size depends on the distance between the saw frame.
The reason most mill makers don't make it wider is b/c they have learned that it is very hard to keep the band cutting strait at that width.

makes perfect sense now that I see it - thank you!!!!

 

[jdrum]

how are your construction skills. if you have acess to the size timber you say,i would go for the csm first. do a lot of reading hear, the alaskan mill will give you your timbers, then mill 2" slabs and resaw the slabs for 2x4, 6 8 10.
that will give you the framing for sheds to get the TOYS under cover. and when you get ready for a bsm ( ether buy or build ) you allready have something to slab the big logs down to fit your bsm.

 

[headleyj]

how are your construction skills. if you have acess to the size timber you say,i would go for the csm first. do a lot of reading hear, the alaskan mill will give you your timbers, then mill 2" slabs and resaw the slabs for 2x4, 6 8 10.
that will give you the framing for sheds to get the TOYS under cover. and when you get ready for a bsm ( ether buy or build ) you allready have something to slab the big logs down to fit your bsm.

Construction skills are good I'd say. Buddy who's a machinist/ fab guy suggested the same thing.

Argh, just can't decide. Called the local mill - 27" max there.

I think I'll start with the CSM for the big slabs - that's what I want to do 1st and that's the ONLY thing the BSM won't do. Hell I may change my mind in an hour who knows.....

 

[BlueRider]

I think that the 34" size limitation has more to do with the fact that these tye of bans saw mills are portable and that is going to limit the distance between the wheels to the width of the trailer. max trailerable width is 8'. As others have siad you want a wider and thicker blade for a wider cut. this requires larger diameter wheels. so on that 8' wide bsm you might need 30" wheels which would give you 36" cut. the only way you could go biger is if the mill head would pivot 90* once you had the mill on site.

 

[Mike Van]

Some of it's about money too, and what most people are going to saw. How many 4 ft dia. and up sawlogs do most bandmillers come across? I've had one or 2 in 20 years of doing this. The hp has to do with speed of cut, my 10 hp three phase will saw down a 12" wide pine cant in 15 seconds, oak maybe 25? And do it 8 hours, day after day. Some guys have both, a huge slabber csm and bandmill. Me, I couldn't imagine cutting 1" boards with a csm. One board for me, one for the sawdust pile ?

 

[BobL]

Me, I couldn't imagine cutting 1" boards with a csm. One board for me, one for the sawdust pile ?

It's not quite 1 to 1, especially if one uses lopro chain but it's still not good.

I was trying to convince a friend of mine who wanted to mill a heap of logs into 1" boards with a CS mill that he was going to waste a lot ood. When I told him that after he had milled 100 logs he would have about 25 logs worth of sawdust to deal with he finally saw the light.

 

[huskyhank]

snipped.........

But then you also need comparatively more grunt.
Look here www.garymkatz.com/ontheroad/hulloaks.htm

>>>>> THAT <<<<<<

is the most wonderful link I have seen for quite a while.
If they will allow it, I will visit that next time I am in Oregon.

 

[BobL]

>>>>> THAT <<<<<<

is the most wonderful link I have seen for quite a while.
If they will allow it, I will visit that next time I am in Oregon.

Did you note the max length of lumber they can cut! 85 ft

 

[huskyhank]

Did you note the max length of lumber they can cut! 85 ft

Oh yeah!

I might swoon if they do give me a tour.
I'll have an ambulance on stand by.

 

[redprospector]

What limits this? What I don't get is this
BSM:
- 23hp motor (optional I know)
- thin blade ~ 12' long total blade length
- max log diameter ~ 34"

CSM:
- 8.5 hp (3120xp let's say)
- wider cut with ripping chain
- you can run what....a 48" bar or bigger on an alaskan? ~8' long total length


Why with more hp and a thinner blade (less friction I'd think) can't they make a BSM capable of slabbing wide stuff like the Alaskan?

What am I not thinking of here? Thanks.

Well, here's my take on it.
The manufacturers that are selling their mills have to look at economics. How many people that are looking to buy their first band mill are looking for one under $10K?
The first mill I built would cut 34" between the guides, and it did it with 1 1/4" blades. But it cost a lot more to build than the one I have now.
A fully hydraulic mill with a diesel engine that will cut a 36" log can cost well over $40K. How much would it affect sales if they built that mill to cut a 48" slab, but the price had to go up $15K?

The blades we use (1 1/4", 1 1/2") will cut very wide stock if it is kept in good shape. The biggest problem with these blades is that we (including me) don't fully understand what it takes to keep them in that kind of shape.

Just my $0.02

Andy

 

[Brmorgan]

so in order to cut a wider log you need;
- a wider "throat" on the BSM ,which means
- a wider and longer blade, which means
- more tension needed, which means
- more hp required to push it

understand.

OK riddle me this;
why if a BSM is capable of a max log diameter of say 34", is the max board width only 24" or so?

Well, I guess it probably comes down to the fact mills aren't really designed to cut a log directly in half across its widest axis/diameter, since it's a really poor way to go about sawing a log in the first place, except for specialty purposes. So, if you have a 34" log to begin with, by the time you square it up into a cant and get rid of all the wane, it will be pretty close to the maximum cut width.

As for cutting wider logs in general, you can do it with narrower blades but the feed rate must be lowered accordingly; also the cutting efficiency is even more affected by tooth set and sharpness. You'll also want to go with a lower-tooth-count blade, with bigger gullets for better chip/dust clearance. Same idea as using skip chain on long saw bars. To that end, the reason it takes more horsepower to drive a bandmill is largely that expectations are (rightly) different. I MIGHT get 1"/sec on a 36"+ wide cut with my chainsaws, but a bandmill owner would be awfully disappointed with that kind of feed rate. You can drive a band with a 5 HP Chinese knockoff engine if you want to; there are guys on Youtube doing it. It'll just take longer and probably not cut quite as smoothly. Also, keep in mind that with a chainsaw you have the bar to guide the chain in a straight cut. If you wanted to emulate a wavy bandmill cut, put an .058 chain in a worn .063 bar sometime... Or file one side of cutters at 10° and the other at 25°.