Electric or gas band mill

So I have priced up a bandmill from Linn and I am looking forward to taking the next step. My question is gas or electric?
- I do not plan on going mobile so that is not a factor.
- I have a 15hp rotary phase converter and enough power in the shop I am building to run it.
- I live on 5 acres but would like to keep the noise down for my nieghbors

So I am leaning towards electric but I am very consernced about the clutching issue. When you run electric on a bandmill what do you do when you exit the cut??? Do you just keep the band going full speed? Is it possible to have an electric clutch? Do you just turn it off and restart on the next cut?

What do you guys think?

P.S. I have a 10hp 3 phase motor already. Will that be underpowered for cutting through 24" of hardwood? How would 10hp electric compare to gas?

10HP would be equivalent to a 15-17HP gas engine, if I'm remembering right. That's not really a scientific or mathematical conversion though, more of a real-world and depends on the end application of the engine/motor. It isn't as much a horsepower issue though as a torque issue and how much work can be done. With an electric motor, if you load it up a bit, the motor will just draw a few more amps of electricity from the mains and keep on chuggin' along. When it comes to an internal combustion engine, you encounter several limiting factors such as displacement, fuel type/delivery, porting, rotational mass, etc; not to mention that you have pistons constantly changing direction whereas a motor is constantly rotating in the same direction. So basically, if you load an engine to the point that it can't maintain its ideal torque RPM, there just isn't much you can do about it, whereas an electric will be able to compensate somewhat and maintain torque by drawing more power - albeit at the expense of life expectancy.

An electric clutch should be no problem at all, especially in the 10HP range. I don't know who might carry such a thing in the USA, maybe Tractor Supply or Harbor Freight going by some of the other stuff they carry. In Canada we have a store called Princess Auto which is great for such things. A go-kart or farm equipment shop should be able to sort you out. Many newer lawn tractors have electric clutches on the blades; you might be able to find a wrecked unit, or even order a replacement one straight from Husqvarna etc. You could also try scavenging the electric clutch from an automotive air conditioner compressor - might have to try a few to find one that will work with your driveshaft size with minimal modification though. I have a couple old ones here I've been keeping around for my bandmill project.

Your phase converter doesn't have a variable-frequency generator (slang term = "Freq Drive") built into it, does it? Many commercial models do now, and not always the expensive ones. If so, you can use that to change the speed of the motor much more easily.

I'd recommend against leaving the band running full-speed out of the cut all the time; I realize I don't even own a bandmill yet, but it just seems it would be extra wear-and-tear on all moving parts if nothing else, and probably a safety issue as well.

Can8ian,

My personal thoughts are that electric is much quieter, however you need 3 phase to get the power needed, as you probably know as you have the phase converter. The 15HP converter is needed for the 10HP motor, also, as you might know. At least for band mills as they require quite a bit as they spin up. I think the rule is the you can start a motor that is 2/3rds the size of the RPC (idler) motor.

The best would be having 3 phase electric with enough amps for the motor you want to run. I run quite a bit of 3 phase equipment at my house (woodworking and metalworking equipment), and the phase converter can be a tad annoying, humming in the background. Most of my equipment is smaller so I only have a 7 1/2HP RPC, with a 5HP motor being the largest I use on it. Even with the RPC, I bet the noise is lower on the electric motor. The RPC I use was built by Anderson, I think in Arizona, but I bought it from someone else used.

A 15HP motor would be ideal for a sawmill, and I think that is what WoodMizer puts on their LT40s, but could be wrong. I have seen 5HP and 10HP electric motors on smaller sawmills, so you would be ok with one, but a 15HP would give you a bit more power, IMO. You could always upgrade later, and 3 phase motors are cheap, cheap, cheap, typically on the used market as so few can use them and most commercial shops will buy a new one to replace them if they go out. More often than not people converting over to single phase dump them for cheap.

So if I had variable speed I could use a centrifugal clutch. I don't know what the benifit to that would be? I really think I want a 15hp motor but I probably can't use my 15hp phase converter for it. This is the model of phase converter that I bought

http://www.americanrotary.com/15-HP-rotary-phase-converters.html

The only thing I did differently is I provided the motor that I got off CL for $75 and it saved me about $600.

With the wider boards I am going to be cutting I think I would be disapointed with anything under 15hp. Also power company sais 15hp motor is the max I can run on my service.

I may be stuck with gas (story of my life).

Can8ianTimber said:

I really think I want a 15hp motor but I probably can't use my 15hp phase converter for it.

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Probably not, since certain equipment needs more to start, and band saws are typically one of those. A tablesaw could work, although you rarely find a tablesaw with a 15HP motor on it. The only way would be to try it, but any motor that needs to spin up to speed will typically fit into the 2/3rds the size of the idler motor, in my experience. This includes lathes, band saws, as far as I remember. The Phase-O-Matic site has some good info on that.

Can8ianTimber said:

With the wider boards I am going to be cutting I think I would be disapointed with anything under 15hp. Also power company sais 15hp motor is the max I can run on my service.

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Yes, the problem is the actual amps, I was lucky to get a low amperage idler motor that will run on a 20 amp 220v single phase circuit. Most of them require 23 amps for the motor, but *some* are 19 amps.

As I mentioned before, the best world is when you have enough amps to run the 3 phase outright, IOW, a large enough 3 phase circuit that you don't even need a converter on...Next best is having as much amps as you need for the converter/idler and as you start getting into 10HP-15HP you start stressing most circuits, unless your in a large industrial complex. At least my experience. As I recall as 20HP motor will draw close to 70 amps, that is almost an entire circuit that most homes have where I live (125 amp is common). A 15HP motor will need right around 40 amps, as I recall. Is your 220v single phase a 40 amp circuit?

I have a 10hp electric on mine and I have no clutch. I just let it run. Is that the way I wish it was ? nope. I dont know if my motor would hold up to a bunch of restarts ? I have had to have the capicators replaced several times on my planer motor and was told frequent restarts could be to blame ?
I have had people tell me all I need to do is add a 2nd electric motor ( same hp and rpm ) that I could turn on only when needed ??? I dont know if thats a good idea or not ? I dont know alot about electricity but seems like I have been told I could use a dc motor if I wanted variable speed and could just turn a dial and go from full throttle to a stop ? If thats the case ? a 20hp dc would be at the top of the list if I build another.

Backwood said:

I have had people tell me all I need to do is add a 2nd electric motor ( same hp and rpm ) that I could turn on only when needed ??? I dont know if thats a good idea or not ? I dont know alot about electricity but seems like I have been told I could use a dc motor if I wanted variable speed and could just turn a dial and go from full throttle to a stop ? If thats the case ? a 20hp dc would be at the top of the list if I build another.

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Actually, now that you mention it, there is a guy on ebay that has a twin electric motor conversion for the Norwood mills.

One thing about using a Rotary Phase Converter is that you can have up to 3x to supported amount running at any given time. So in Can8ian's case if he has a 15HP RPC, you can safely run a 10HP motor on it of most any type which includes a sawmill which need to kick up to speed. However, you can run 30HP on that RPC setup.

If it is possible to use 2 motors, you could use these 2 together on the same RPC, so that you could have 2 x 10HP motors running in tandem as Backwoods suggests.

Not only would that be an answer to your amp/hp problem, it might run smoother than one larger 15HP motor, IMO.

Here's their website, the company is Eastern Compact Equipment Center Inc. Worthy to note that their conversion is single phase and requires a 50 or 60 amp circuit for the dual 5HP setup. The RPC gives you the advantage of allowing for up to 3x the HP running at the same time, on the same circuit.

Hope that helps.

EDIT: Here's a video on YouTube of the Quiet Runner:

http://www.youtube.com/watch?v=FOp9iv2plKY

I love it. Just got done reading through his website. That should be easy enough to put together. All I would have to do is find another 10hp 3phase motor with the same RPM and the clutch system looks pretty simple.



Looks like he approximates a loss of about 10% power with the double motor set up.

Can8ianTimber said:

I love it. Just got done reading through his website. That should be easy enough to put together. All I would have to do is find another 10hp 3phase motor with the same RPM and the clutch system looks pretty simple.

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I agree, and a dual 10HP setup will give you a very nice mill, indeed. You should be able to find another 10HP motor on craigslist for about $50-$100 I bet.

Can8ianTimber said:

Looks like he approximates a loss of about 10% power with the double motor set up.

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Even so, 10% from a 20HP system is not too much. Either way, you don't get anymore speed out of it, you get torque, that's where the gains are. I bet a dual 10HP system would easily pull the 1900a/210 rather than the 190a.

I run a 10 hp 3 phase on the mill I built. 3 phase service, 120/208 About 18 years now, same motor. How many thousands of BF, I have no idea. In frozen red oak, 24" dia, I wish I had 15 hp. So, I feed a little slower. At the end of the cut, I push the red 'stop' button. Run the head back, lower, turn the log, whatever, then I push 'start' & make another cut. I can do a thousand BF/day alone, when I want to. With no time clock or bottom line to make I really don't care. Not running the blade continuously, they last a long time. I sharpen some 12 times before I find a crack. It's not always how many BF a day you can do, it's how good the ones you get done are.

Mike Van said:

I run a 10 hp 3 phase on the mill I built. 3 phase service, 120/208 About 18 years now, same motor. How many thousands of BF, I have no idea. In frozen red oak, 24" dia, I wish I had 15 hp. So, I feed a little slower. At the end of the cut, I push the red 'stop' button. Run the head back, lower, turn the log, whatever, then I push 'start' & make another cut. I can do a thousand BF/day alone, when I want to. With no time clock or bottom line to make I really don't care. Not running the blade continuously, they last a long time. I sharpen some 12 times before I find a crack. It's not always how many BF a day you can do, it's how good the ones you get done are.

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Wow that is what I am talking about!!! 18 years on one electric motor. Think of how many gallons of gas you have saved.

I was really hoping to pull the electric mill guys out of the woodwork and I like what I am hearing. Well I think my mind is made up. Now I just have to finish my shop so I can get to the mill. Planning on pouring the concrete on Friday so it is getting close.

Backwood said:

I have a 10hp electric on mine and I have no clutch. I just let it run. Is that the way I wish it was ? nope. I dont know if my motor would hold up to a bunch of restarts ? I have had to have the capicators replaced several times on my planer motor and was told frequent restarts could be to blame ?
I have had people tell me all I need to do is add a 2nd electric motor ( same hp and rpm ) that I could turn on only when needed ??? I dont know if thats a good idea or not ? I dont know alot about electricity but seems like I have been told I could use a dc motor if I wanted variable speed and could just turn a dial and go from full throttle to a stop ? If thats the case ? a 20hp dc would be at the top of the list if I build another.

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Heh, good luck finding such a motor or even a power cable capable of feeding it. 20 X 746 = 14,920 Watts. Assuming 24V DC input, that would mean the wire would be carrying 621 Amps. So you'd need a double set of 4/0 wire feeding it (and a single 4/0 strand is about half an inch diameter).

TraditionalTool said:

I agree, and a dual 10HP setup will give you a very nice mill, indeed. You should be able to find another 10HP motor on craigslist for about $50-$100 I bet.

Even so, 10% from a 20HP system is not too much. Either way, you don't get anymore speed out of it, you get torque, that's where the gains are. I bet a dual 10HP system would easily pull the 1900a/210 rather than the 190a.

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Well, you can get some more speed since the added torque would allow you to bump up the pulley size a bit if you needed to. But bandsaws aren't like chainsaws - faster isn't always better. Bands have an ideal FPM speed that should be maintained whether you have enough torque to run faster or not.

the only trouble with runing 2 3 ph motors would be starting them both at the same time. you will need to start one motor, then the other. so add another idler clutch between the motors, so both motors start under no load conditions.
all motors draw the most amperage during startup, for about a second or two a 10 hp can draw 170 amps or more, then drop back to 8 or 10 amps with no load, check the id plate on the motor your going to use, there should be a box with FLA and a number, that is the full load amperage that the motor will draw under heavy load. a 10 hp should be around 40 amps.
running 2 motors i doubt you will ever need full load amps. you are supplying the equivant of over a thirty hp gas engine
another plus with running 2 motors the second motor helps balance the voltage across the legs in the 3 ph circut, reducing the amount of run capictors needed. to balance the legs. this also lets the motor run more efficently.

jim

brad is right about blade speed stick wit the recomended speed we had all kinds of problems on a 36" vertical mill when we first got it. the guy that had it before kept the origanal drive pulley and replaced it with one 2 " smaller, put the fpm through the roof. we went through 5 blades before we found out what was making them come apart.

jim

You don't necessarily have to use a motor with the same HP as the first motor, either. At the mill I used to work at, the chipper had a 200HP 480V motor to begin with; it was deemed insufficient so they added a 125HP (if I'm remembering right) helper motor to it. The 200 started first and the smaller one a few seconds later after the chipper head was up to speed.

For two 10HP motors you wouldn't need too much of a startup delay between them, especially if they're starting up under no-load conditions. They would get up to speed pretty quickly and the inrush current wouldn't last very long. Something that could help with a lot of starts and stops is to put a large inductor coil in the circuit; these help mitigate current spikes when a load is introduced, and will help out your circuit breakers too. In industrial applications these are often called "reactor" coils. I built a big inductor like this with some 4-gauge wire and the core from a microwave oven transformer and put it in my stick welder on the electrode line - I noticed a big difference right away; there isn't nearly as much dropoff when the arc is first struck and it's easier to keep a nice steady arc now.

Brmorgan said:

Well, you can get some more speed since the added torque would allow you to bump up the pulley size a bit if you needed to. But bandsaws aren't like chainsaws - faster isn't always better. Bands have an ideal FPM speed that should be maintained whether you have enough torque to run faster or not.

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I guess my point was that just adding a motor wouldn't give you anymore speed, you would just have 2 motors worth of torque on the wheels. In the same sense you won't change the speed on a chainsaw without changing the rim/sprocket. I see a lot of folks trying to get their chainsaws as fast as they will go at WOT, and some people like myself just don't care about pure speed...when I'm cutting a dovetail on a house log, I'm wanting to be precise, not fast. When I'm brushing a log I don't need the RPMs up at 15000, that's not going to give me control.

In that sense I completely agree with what you say about FPM. Machinists are very specific about the FPM when they are cutting, and those same principals apply here on a sawmill.

The other point related to FPM, is gas vs. electric which may be different. I don't know but this will be dependent on the motor(s) the Can8ian is using. That would be something to check. As I recall, Linn offers both electric or gas on the 1900a/210 (the largest sawmill) so just make sure you have the same RPM motor which you plan to use. I'm sure Gary will provide you with that info. Otherwise his pulley that he provides might be the wrong size.

If you watch that video it looks like he has it set up with two on and off switches. The way I imagin it is to have the clutch disengaged and start the first motor (that way the only load on it is turning the other motor). Start the second motor and then engage the clutch. Am I missing something?

Can8ianTimber said:

If you watch that video it looks like he has it set up with two on and off switches. The way I imagin it is to have the clutch disengaged and start the first motor (that way the only load on it is turning the other motor). Start the second motor and then engage the clutch. Am I missing something?

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Yes, but his are single phase, so it's different. Jim does make a good point about the 3 phase, because although you can have 3x running on the RPC, you can only start one at a time. You only need to start one though, the second one doesn't need to use the capacitors in the RPC, AFAIK, the 3rd leg will already be going once the idler is running.

I believe your plan as stated will work fine, to engage the clutch after both are running.

EDIT: come to think of it, you might be able to run a single 15HP motor by doing that same start/engage-clutch routine, that I don't know for certain.

Blade speed in FPM can be as important as how much hp you have on it. I was 5400 fpm as built, and on Tim Cooks advise slowed up to 4800. It made a difference, less draw in amps. Don't skimp on bandwheel size if you want good blade life. I run 24" cast wheels. The electric is clean & quiet. My mill is all inside this barn

remember that the inrush amperage for a 10 hp motor starting is going to be twice that of a 5 hp. the only reason i suggest an idler between the motors is if both motors are belt connected the second motor becomes the load on the first motor, which will increase the amount of amperage needed to start the first motor. i hope this makes sense.
another thing is you may not need the second motor all the time. consider the size and type of timber you are going to saw, softwoods up to 20" may only need the one motor to maintain a good feed rate. when you get into bigger stuff then kick in the second motor. no use in running a motor you don't really need, but it's nice to know it's there if you need it. mike van could give more insight in to when the extra torque would come in handy.

nice set up mike