band wheels - the great debate

[flip]

I got my stuff from a local bearing shop but found a better deal at...

www.indiana-fan.net

Shafts ame from...

www.linnlumber.com

Flip

[Tom]

There is an optimum speed for any given "pitch" band.  It is measured in feet per minute by determining the distance traveled by a single tooth.  A band mill is configured to maintain this band speed.  

If you have a 10 horse engine that drives the blade at 5,000 fpm and replace it with a 20 horse engine.  It doesn't follow that that you now run your blade at 10,000 fpm.  The optimum speed for the blade will still be 5,000 fpm.  The extra  horsepower just lets you take a bigger bite with the teeth and better optimize the efficiency of the blade before the engine begins to bog.  

You will get to a point of counter-production on horsepower too.  In that case, you begin using a different band.  It's the balance of horsepower, band-wheels and band that makes a good saw.

large band wheels are easier on the band and benefit  the saw in the cut by overcoming the slowing effects of knots, etc.  They also serve another purpose.  They are what is responsible for the "throat" size of the saw.  Being able to saw wide boards is more of a matter of length of band.  Being able to split a 24" cant and have the top piece pass through the saw's throat is dependent on the distance between the top and bottom of the band, as well as the hardware that supports it.   To get the 16" tall throat of some saws requires a wheel with a large diameter.  In this case, the wheel is for configuration, not for band efficiency.

[Modat22]

This discussion reminds me of an audiophile discussion on using power supplies with huge storage capacitors and torroid transformers verses lightweight switching power supplies.

Having huge capacitors allows a reserve of power for a split second high bass output from the speaker where a switching supply generates the power with a slight lag.

Same discussion about different technologies.

[Tom]

Yep.  Just like that.........  .........  only different.  :D

[slowzuki]

It is a similar concept, some electrical circuits are the same as mechanical circuits for solving.  The capacitor is the electrical spring, resistance is drag, and inductance (transformers and coils) are mass.

[Buzz-sawyer]

i'm kicking around the idea of building a larger saw, i'm trying to figure out the pros and cons of the wheel design...

TRAILER / BOAT TIRES
pros

• lower cost

Much lower for econmy minded project....
[li]no band lube needed[/li]  Nope you still need band lube...even homey uses gallons of it...seen so myself
[li]supposedly reduced band breakage[/li] I believe it does
[li]easy to get large diameter wheels to extend band life[/li] yep
[/list]

cons

• more difficult to drive the drive wheel

why? same labor involved in rigging steel or rubber
[li]needs to be turned true[/li] Nope it really does not...well within reason if it shows lumpy some folks run em of the line.....a simple task to spin it it and set a stationary cutter to turn it like a lathe
[li]needs to be balanced[/li]Thats easy...just do it after ya shave em if you need to
[li]needs tow-in set in the tires to keep the bands walking straight[/li]Pretty simple to rig and only a very minute amout is needed...dont steel wheels do the same?[/list]

[logwalker]

The crown on either wheel is what controls tracking. Toe-in does not explain what is going on. The crowned wheel needs to be able to pivot on a vertical axis to get the blade to track to the desired position. I have a 36" vertical bandsaw that only has a crow on the top wheel. Kinda surprised me when I noticed it. As for the rotating mass, it helps to keep the blade tensioned evenly around the band and keeps it cutting straighter. How many times have we said it now?  LW

[flip]

If you've ever had toe problem you'll know toe has everything to do with it, ask me how I know and why I took my mill back to TK to get adjusted.  Rotating mass has nothing to do with tension on a band unless imbalance is a factor.  The more surface area a drive or idle wheel is in contact with the band is better but ultimately the band is what controls tension if runout in the wheels is not a factor.

I'm done talking about this: my opinion, you will be better served using sheaves with belts than tires or solid steel wheels.  You'll get more bang for the $$.

[Dan_Shade]

i kind of like the sheave idea better too....  now i'm only stuck with figuring out diameter of the sheaves, i'm having trouble finding anything larger than 19", is this big enough, of should I press for 24".

[mike_van]

Dan, I bought Browning Poly V 24" dia sheaves, About 1 1/4" face, cut a polyV belt & used bandsaw tire cement to hold it on. 10 years ago? Can't remember. Never had a problem with them.  Taper hubs for any size shaft too. I'd have to dig to find an invoice, but that price i'm sure is history.

[Dan_Shade]

where did you get them from, Mike?  I'm sure they aren't cheap....

[Tom]

Here in Jacksonville, the large sheaves are handled by a Pump company that sells to Industrial users who build and rebuild pumps. They stock all manner of sheeves, belts, shafts, gearing, etc. 

http://www.powerandpumps.com/

Perhaps you might have something like that close to you.

[mike_van]

Well, you made me dig for that invoice Dan, but I was curious too, couldn't remember. Is that where the grey hair comes from?   I bought one in 1990 for 195.00 from Chase & Cooledge in Holyoke Mass. , The other in 1995 for 245.00 from Olmsted Flint in W. Springfield Mass.  I had man made steel wheels, 24", neither was true, that was why I bought these. If you search Browning on google, retailers or distributors, etc., you should be able to come up with something. I see in Cooks catalog that they sell wheels, 19" is 245.00, 26" is 399.00 & 30" is 449.00.  Oh, on the path to the Browning one's I bought, I had an old wheel at the farm, 24"dia, I cut it to width on a brake drum lathe, bored it the right size, and made a tire from conveyor belting. Boy, did it run smooth - about a log & a half, then it let loose - about 8 pieces came out the bottom of the guard. It was a thin rim cast steel, probably weighed 10 lb. or so. The Browning's are about 45 lb. or more each.  The max. rpm is cast in the rim, I was 5500 sfpm and still safe. I did go to 4800 sfpm on Tim Cooks sugestion, found it  cut better there.

[Larry]

There's a company that makes steel band wheels...I've seen em advertize in some of the trade magazines.  Sorry I read and toss so don't have one on hand.  Pallet News or something like that.  Maybe somebody has one laying around.

I've bought old Crescent shop band saw's with wheels in the 28" to 36" range.  Price ran from $10 to couple hundred.  Course you would have to run a tire and glue it on for a sawmill, and I don't know how it would hold up.

The production grade re-saw's I've seen are all running steel.  Iffen I remember right the WM LT 300 runs steel also.

[logwalker]

The change in tension that I am referring to is when the blade slows down due to increased load and the rotating mass of the idle wheel and all the band after the cut is still driving at the original speed. It can throw enough slack, or reduce tension enough to allow the blade to deflect and create a wave. That is my understanding but maybe I am wrong. Who knows for sure. Not me.  :D

[Dan_Shade]

i hear you on the pulley blowing up, Mike, that's why I want to do it right...  my education sometimes hinders me a bit, but it helps me make better decisions (most of the time)....

i'll start scraping some cash up and go from there....

that's an interesting point, lw, there could be something to it....  physics is never simple, that's why physicists always assume the worst of it to be a specific value!

[Dan_Shade]

you're going to shoot me, mike.... you have a part number?

i found a browning pdf catalog on their website, it's got like 123 pages of sheaves with different bushings, etc!!!

i'm going nuts!!!

[low_48]

Well, I'm a woodworking guy  and run a 5 axis cnc router at work. I've been thinking about baltic birch plywood wheels. I can machine within a few thousandths of an inch, cut any pattern of spokes or holes I want, machine bolt patterns for mounting, etc.... Maybe you fiberglass after machining to limit problems with blade cooling water? I imagine that you would want large steel "washer" plates at the hub to add stiffness. I looked at roller chain gear sprockets at the local farm store, nice hub, lots of places for bolts, etc...... What do you guys think? Anyone want to place orders? :D :D :D It would be nice for someone else bring them up to speed first .  ;)

[jpgreen]

Take your wheels and use them for a green sand cast mold out of aluminum.. 8)

[mike_van]

Dan, # 6L240Q on the sheave & 765L6 on the belt - The weight is 47.5 lb. ea. without a bushing. My powders damp from all the rain, so you're safe for now !  :D

[Modat22]

I remember seeing a large bandsaw mill made using plywood sheaves on the net a few years ago. Seems to me that the guy made the sheaves from layers of ply, installed a metal hub and coated the things in fiberglass. Afterward he has to cut the crown using some homemade cutter on a shaper.

I'm thinking the sheaves where 40 inches. I'll have a look on the net today and see if I can find that one again.



Update. I looked all over the place for that sawmill that had the homemade plywood sheaves and didn't find it. Perhaps it didn't work out and failed catastrophically and it was removed from the web or I just dreamed that I saw it.

[Tom]

You saw it.  I've seen it too.  It's just hidden in the multitudes of personal sites.  I recall this as someone's personal website or home page.

[Dan_Shade]

are 19" sheaves too small?

[Tom]

Dan

Aren't Woodmizers sheaves about 18 or 19 inches in diameter?   They have built some mighty good cutting mills with that size of sheave and created a defacto standard of a 13'2" band as well.   Seems to me those figures would get you into the ballpark of being able to use a lot other people's off-the-shelf blades and stuff.  It might even let you take advantage of some pre-tested (proven) engineering.

why re-invent the wheel?

I didn't say that.  :D :D

[Dan_Shade]

that's kind of what I'm getting at, Tom... who small is too small?

i'm an engineer by trade, so getting the most out of things is what it's all about, then again, i'm also too lazy to go back and figure out how many times around a given diameter before the metal will theoretically break!

I know bigger is better, but bigger is not always best