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single belt or double belt?

Started by Kurban, March 18, 2014, 08:15:40 PM

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Kurban

I am planning to assemble my sawmill soon. I have not seen a discussion of the belt requirements. I am planning to use a 10 HP 3-phase electric motor as the main power source and 21" trailer tires for the band wheels.

Question: Is a single belt adequate or should I go for double belt pulley? The issue is re;evant because if I weld the pulley to the rim, it is easier to to so with a single belt pulley. Not to mention the centrifugal clutch pulley issue.

Sal.

ladylake

 I'd go with a double, you might get by with a single if the smallest pulley was around 7 or 8 ".    Steve
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blackfoot griz

What size belt are you thinking about using? Can't you use a shaft with a keyway?

While you don't want to be smoking belts all the time, going with too much belt can be really costly. Not long ago, I had a customer that bought  a Dodge 15:1 gear reduction box from me.  It lasted 2 weeks instead of many years.  When looking in to it, the unit(running 8-10 hours daily) was going through a belt every 3 months or so. Unknown to the boss, one of the employees doubled the belt.  The end result is that the double belt far exceeded the capacity of the gearbox.  Instead of trashing a $15 belt, they trashed a $2500 gear box.

You have any pictures of your setup?

bandmiller2

Sal, a centrifugal clutch won't work on a motor as it always runs at its rated speed, an engine will idle and allow the clutch to release. I have a 15hp three phase motor and two "B" series belts and have never detected any slippage. I have a belt idler flat pulley to tighten and release the belts so I can start the motor unloaded. Your tires have a lot of weight to start turning so I would recommend two belts and an idler setup so the motor can start unloaded or you may be tripping breakers on startup. Frank C.
A man armed with common sense is packing a big piece

morgoon

While not electric

I have been using a single belt for a long time with a 14 hp Wisconsin and a snowblower style idler. Two belts would give you peace of mind though I think.

I'll try to get pics tomorrow
Homemade bandsaw, made by my mentor and dear friend Unto...who turned 85 this year

And I just made my first longbow...awesome

chopperdr47

This might be a little involved for what you are wanting but it helped me figure what I needed to transfer 60 hp.

http://www.flexco.com/filebase/es/src/Installation_Instructions/v_belt_selecguide.pdf
If ya ain't got what ya need, use what ya got

Larry

As Steve implied it is the small pulley that limits horsepower transfer.  Grainger has a handy dandy chart to pick belts.  You can't get there with a "A" belt.  With a "B" belt the smallest pulley for 10 HP is 6.6".  If you add a "X" to the belt size that means cogs and higher horsepower transmission.  With a "BX" you can use a 5.8" pulley.  Can't use a cog belt with a manual clutch as they are too grabby.

I've found the chart conservative for most applications.  The problem with a sawmill is you can stick the band in a wide cut and squall the belt.  That's because your 10 HP motor can put out maybe 15 - 20 HP before the circuit breaker trips.  Once you squeak the belt that puts a slick spot on it and it will slip next time even easier.

So, I might bite the bullet and go with a banded (two BX belts tied together) "BX" belt for peace of mind and long term economy.
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

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YellowHammer

Not being a belt expert, I would look to conventional electric power tools for guidance.  Every one of my electric shop tools over 5hp has at least a double belt, or a wide serpentine style single.  An LT40 has a joined triple main drive belt.  Not saying a single belt wouldn't work, but it seems like a double belt would be preferable.  It's very important that the main drive belt doesn't slip, it can cause a lot of weird problems when sawing. 
YH
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morgoon

Well I can post up a couple pics of my mill drive in the morning that is a copy to a sister mill that runs 10hp 3ph on a single belt..

It runs thru a homemade phase converter if that makes a difference in final hp.

My mill is a temp spare tire design as well, however I have been considering an engine swap for more hp.... But this discussion has me wondering about pulley size and adding a second belt to reduce slippage.

Perhaps that is a new thread... I only mention it to say I'm not 100% happy with my cut speed but it does cut well.
Homemade bandsaw, made by my mentor and dear friend Unto...who turned 85 this year

And I just made my first longbow...awesome

pineywoods

If you run wide enough tire for a bandwheel, just run the drive belt around the tire instead of buying big expensive v belt pulleys. Sounds crazy, but I saw a pto driven genset that used a car tire and wheel for the large pulley, with the v belts running on the tire tread.  Worked good, especially if you use a double belt.
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Dave Shepard

I was told at the industrial shop that a B series belt will transmit 7.5 electric HP. Do you have an industrial supply house around where you are getting your belts and sheaves? They should be able to lead you in the right direction. Why do you want a centrifugal clutch on an electric motor?
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Magicman

Quote from: Dave Shepard on March 19, 2014, 12:50:58 PMWhy do you want a centrifugal clutch on an electric motor? 
I agree.  Reply #3 was very informative.
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morgoon

https://forestryforum.com/gallery/displayimage.php?pid=154139

I have to learn how to post pics...I just ran out of time tonight

If you look in my gallery at the only pic you will see my idler set up.

As mentioned my mill is a copy of one that runs a 10hp 3ph motor and the drive is similar

The electric mill is buried under snow and about an hour away so I won't have a pic for while :(

I have a pulley the same size as the temp spare rim behind the rim, that is bolted on in 6 spots to drive the sawhead as a single assembly.
Homemade bandsaw, made by my mentor and dear friend Unto...who turned 85 this year

And I just made my first longbow...awesome

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