I've been using a Jet 16" Bandsaw for about 5 years. I've always had to take it slow with this saw while resawing. It would pop circuits and bog down. I rewired it for 220 and that made a big difference, but I still had to take it slow.
My current project requires me to build some bifold doors. The rails and styls are 2x6 Douglas fur. I need to bring the board thickness down to 1 1/16" and rather than run them through my plainer a bunch of times I am resawing them.
About halfway through the stack things went wrong. I hit a piece of wood that was not completely dry. My blade was starting to get dull by this time as well. Rather than stopping and sharpening the blade and going to a dry piece of lumber, I forced it and ended up burning out the capacitors on my motor. (No need to kick a man when he's down here fellas, I know what I did wrong.)
I've replaced the capacitors and the saw still has no power. I've come to the conclusion that some of the windings in the motor have broken from being overheated and the motor is toast.
I've researched the various motors from Jet. There are three that will fit the saw without having to fabricate a mounting.
=B7 The original 1.5 hp replacement at $230 =B7 The standard 1.75 hp off Jet's 18" model at $451 =B7 Or my favorite the 3hp option for their 18" Bandsaw at $533
I'm concerned about going back to a 1.5 hp because it always seemed under powered before. If I were to spend the money for a larger motor, I feel that I might as well go for the big Kahuna. This brings me to my questions.
1=2E Is there such a thing as too much power?
2=2E Could I cause more problems than I solve?
3=2E Is the 1.5 horse really enough power and I just suck at setup and that's why I had the problems to beguine with?
Do they show a 3-phase motor option for 3-5hp? If so, it should be less expensive and have more power. Get a single phase input VFD and have variable speed as well. Various other options come to mind but would not be a factory configured option. Respectfully, Ron Moore
My current project requires me to build some bifold doors. The rails and styls are 2x6 Douglas fur. I need to bring the board thickness down to 1 1/16" and rather than run them through my plainer a bunch of times I am resawing them.
About halfway through the stack things went wrong. I hit a piece of wood that was not completely dry. My blade was starting to get dull by this time as well. Rather than stopping and sharpening the blade and going to a dry piece of lumber, I forced it and ended up burning out the capacitors on my motor. (No need to kick a man when he's down here fellas, I know what I did wrong.)
I've replaced the capacitors and the saw still has no power. I've come to the conclusion that some of the windings in the motor have broken from being overheated and the motor is toast.
I've researched the various motors from Jet. There are three that will fit the saw without having to fabricate a mounting.
· The original 1.5 hp replacement at $230 · The standard 1.75 hp off Jet's 18" model at $451 · Or my favorite the 3hp option for their 18" Bandsaw at $533
I'm concerned about going back to a 1.5 hp because it always seemed under powered before. If I were to spend the money for a larger motor, I feel that I might as well go for the big Kahuna. This brings me to my questions.
Is there such a thing as too much power?
Could I cause more problems than I solve?
Is the 1.5 horse really enough power and I just suck at setup and that's why I had the problems to beguine with?
Yes. If the blade bogs down and the motor forces things then you may end up breaking or bending the wheels, pulleys, or frame.
1.5HP should be enough. Are you using the right blade? A blade with too many teeth will load up with sawdust and bind in the kerf. For resawing I use a sharp 3TPI blade and have no trouble resawing 6" hard maple with only 1HP.
Art
Is there such a thing as too much power?
Could I cause more problems than I solve?
Is the 1.5 horse really enough power and I just suck at setup and that's why I had the problems to beguine with?
My current project requires me to build some bifold doors. The rails and styls are 2x6 Douglas fur. I need to bring the board thickness down to 1 1/16" and rather than run them through my plainer a bunch of times I am resawing them.
About halfway through the stack things went wrong. I hit a piece of wood that was not completely dry. My blade was starting to get dull by this time as well. Rather than stopping and sharpening the blade and going to a dry piece of lumber, I forced it and ended up burning out the capacitors on my motor. (No need to kick a man when he's down here fellas, I know what I did wrong.)
I've replaced the capacitors and the saw still has no power. I've come to the conclusion that some of the windings in the motor have broken from being overheated and the motor is toast.
I've researched the various motors from Jet. There are three that will fit the saw without having to fabricate a mounting.
· The original 1.5 hp replacement at $230 · The standard 1.75 hp off Jet's 18" model at $451 · Or my favorite the 3hp option for their 18" Bandsaw at $533
I'm concerned about going back to a 1.5 hp because it always seemed under powered before. If I were to spend the money for a larger motor, I feel that I might as well go for the big Kahuna. This brings me to my questions.
Is there such a thing as too much power?
Could I cause more problems than I solve?
Is the 1.5 horse really enough power and I just suck at setup and that's why I had the problems to beguine with?
I appreciate any and all responses.
~Craig
I have the same saw. It too is wired for 220 and so-far I'm able to re-saw any wood I stuff in it. I do use a 3tpi 3/4" Lenox blade. Is only bogs down when the blade gets dull.
Thank you everyone for all your responses. I've been using 3 TPI =BE" blades I've purchased from various internet venders. I'll take your advice and replace the motor with the original 1.5hp and get a Lenox blade.
On 29 Oct 2006 15:38:01 -0800, "RCStrunk" wrote: ...
...
Yes, of course. But is upgrading to a 3HP motor too much power for the saw?
Let's look at some back of the envelope calculations here.
You've got a 16" bandsaw. That means the vertical force pulling the blade through the workpiece is the torque applied by the motor to the lower wheel divided by the radius of the wheel. _All_ of that force is resisted by the table and its supporting structure. None of it is seen by the upper wheel or the structure supporting the upper wheel.
So, for a worst case analysis, assume 100% efficiency in transmitting motor torque to a vertical load on the saw's table.
F = 12*T/R
Where: F = vertical load on the saw table (Pounds) T = Torque developed by the motor (Foot-Pounds) R = Radius of the saw's driven (lower) wheel (inches)
12 = Conversion factor from inches to feet
Since the radius of the driven wheel is constant, the maximum load on the saw's table will occur when the motor develops it's maximum torque. This will be the "Locked Rotor Torque" of the motor and will occur if/when blade binds in the workpiece and stalls the motor.
So what is the locked rotor torque of the motors you are considering. Since I don't know the specific motor, I looked at a typical 3HP 1725 RPM, 230v motor. (Baldor Model L3705) (Ref:
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) which has a locked rotor torque of 45 Foot-Pounds.
Plugging in those numbers:
F = 12*45/8 = 67.5 Pounds.
I have a Jet 16" bandsaw. I don't believe 70 pounds applied vertically to the table would have any detrimental effects on the structure of that saw. Nor do I believe 45 Foot-Pounds torque applied to the lower wheel would have any adverse effects. The 70 pound load would be reacted by the lower wheel mount and bearings. That would be my only point of concern, but without any specific information about those bearings, I would guess that additional load is within their capability. Note that the additional load of the 3HP is only 45 pounds more than that developed by a 1.5HP motor under the same circumstances (Ref: Baldor Model L3514M)
Only you can determine whether the $500+ cost of the 3HP motor is cost effective for you. But if you are worried about overloading the saw's components, I can only say that, except for the cost, I wouldn't hesitate to install a 3HP motor on my 16" bandsaw.
Yes Tom, the $500 question is the one posed by my loving wife as well. Is it worth it? I think I'm going to stick with my last post and get the 1.5hp. If I lose another motor after changing blade manufacturers, then I'll move to the 3hp motor.
Ack! Is it not a standard NEMA mount? Grizzly's motors are about half those figures. I'm sure they're spiffy motors and all, but you've already fried one of them already...
I have the older 18" model and thought it was underpowered with 1 1/2 hp at first. However, after reading Duginske's "Bandsaw Handbook" and giving the (still fairly new then) saw a good tune up and selecting the right blades, it can resaw just about anything I throw at it. 2x6 fir would be no trouble whatsoever. 10" Oak goes pretty easily. 10" Jatoba slows her down a good bit. 1 1/2hp is adequate for 90% of the things I do with it, the1.75hp would probably make it real close to 100% . However, for the price, it'd seem that the 3 hp is not a far cry from the 1.75, and both are substantially more than the 1.5. I really don't forsee any problems going with the 3hp. Let us know what you decide and how it works! --dave
My current project requires me to build some bifold doors. The rails and styls are 2x6 Douglas fur. I need to bring the board thickness down to 1 1/16" and rather than run them through my plainer a bunch of times I am resawing them.
About halfway through the stack things went wrong. I hit a piece of wood that was not completely dry. My blade was starting to get dull by this time as well. Rather than stopping and sharpening the blade and going to a dry piece of lumber, I forced it and ended up burning out the capacitors on my motor. (No need to kick a man when he's down here fellas, I know what I did wrong.)
I've replaced the capacitors and the saw still has no power. I've come to the conclusion that some of the windings in the motor have broken from being overheated and the motor is toast.
I've researched the various motors from Jet. There are three that will fit the saw without having to fabricate a mounting.
· The original 1.5 hp replacement at $230 · The standard 1.75 hp off Jet's 18" model at $451 · Or my favorite the 3hp option for their 18" Bandsaw at $533
I'm concerned about going back to a 1.5 hp because it always seemed under powered before. If I were to spend the money for a larger motor, I feel that I might as well go for the big Kahuna. This brings me to my questions.
Is there such a thing as too much power?
Could I cause more problems than I solve?
Is the 1.5 horse really enough power and I just suck at setup and that's why I had the problems to beguine with?
I certainly stand to be corrected, but I don't believe they are.
At one time I was considering installing a larger motor on my 16" Jet and took some measurements off the mount (face mounted). Since I didn't remove the motor or the lower wheel, my measurements were far from being precise.
Couldn't find any NEMA configuration that looked close enough. There was an IEC (Metric) configuration that was closer but due to the (im)precision of my measurements, I can't say with any certainty that the motor was/is an IEC mount. (couldn't find anything on the motor nameplate that said one way or the other.)
my 18" bandsaw has a 2hp motor and it seems to have adequate power for my uses. I don't resaw a lot though, so YMMV.
the pulleys and belts on your saw were engineered for 1.5hp. if you exceed that by too much what is likely to happen is that the belt will slip when you load it up- the motor won't bog down, but the power won't be transmitted to the blade and you'll be cooking belts if you do it a lot. in other words, the extra power will be wasted. you _could_ upgrade to a triple groove sheave and be able to use a 3hp motor on it, but make sure the bearings are rated for it and that the frame is stiff enough to be able to tension that properly.
An induction motor does not necessarily develop it's maximum torque at locked rotor, it is not at all uncommon for the maximum torque to be developed near the rated speed of the motor.
The torque applied to the lower wheel, and subsequently to the table & supports as you posit, will be multiplied in inverse proportion to the degree that the gearing, pulleys, etc. reduce the speed of the lower wheel.
Intuition here: Assume that 70 lbs downward force exerted through the blade is correct. I can easily grab hold of a seventy pound weight and lift it with one hand (OK, maybe not as easily as I could have 30 years ago.) I really doubt that I could grab hold of a 16" bandsaw blade, turn the saw on, and keep the blade from moving!
Not to say that the saw in question would not benefit from the 3 HP motor or necessarily be damaged by it; I would suggest looking at similar saws and seeing what size motors they use, or (dare I suggest it) calleing JET and asking them.
Yes, different classes of motors can have very different torque vs RPM curves. But, let's see what torque is being produced by any 3HP motor turning at 1725 RPM.
Power(P) = Torque(T) * Rotational Velocity(V) Or T(ftlb) = P(ftlb/sec) / V(radians/sec) But V(radians/sec) = V(RPM) * 2pi (radians/rev) / 60 (sec/min) where RPM is revolutions per minute Or V(radians/sec) = 0.1047*V(RPM) And Power(P) = P(HP) * (550 ftlb/sec)
So T(ftlb) = 550 * P(HP) / 0.1047 * V(RPM) Or T = 5253 * P/V
Where T = torque developed by the motor expressed in foot pounds P = power developed by the motor expressed in Horsepower V = speed of the motor expressed in revolutions per minute
For the motor referenced: P = 3 HP V = 1725 RPM Or T = 5253 * 3 / 1725 = 9.136
Draw your own conclusions.
You are correct, and is the place my original calculations ran afoul of an implicit and invalid, non-conservative assumption.
I implicitly assumed a direct drive/1:1 ratio between the motor and the saw's lower wheel. The force at the table should have been calculated based on the "power" available at the blade. Doing so, points the actual force at the table is approximately 2.3 times the original estimate.
Corrected calculations follow:
Assuming a 100% efficient transmission, the power available at the blade will be equal to the power developed by the motor.
Power(ftlb/sec) = Force(lb) * Blade Speed (ft/min) / 60 (sec/min) Or Force(lb) = 60(sec/min) * 550(ftlb/secHP) * Power(HP) / V(ft/min) Or F = 33000 * P/V
Where:
F = the downward force on the blade in pounds P = Motor power in Horsepower V = Blade speed in Feet/Minute.
For the Jet 16" bandsaw, the blade speed is advertised at 3000 fpm. Therefore, the downward force on the blade is given by
F = 33000 * P/3000 = 11 * P
If we assume no change in overall gearing and the 3HP motor turns the same speed as the stock 1.5 HP motor, the blade speed will remain the same. Therefore, the downward force on the blade, workpiece, and table when the motor is developing its rated horsepower at its rated speed is:
F = 11 * 3 = 33 pounds.
Now the torque developed by the motor under those conditions is, from above, 9.136 foot pounds. This gives an overall "gearing ratio" of
R = 33 (lb) / 9.136 (ft lb) = 3.612 (per foot)
Which is to say that each ft lb of torque at the motor develops 3.612 pounds of force at the blade. Or:
F = 3.612 * T
Now if we look at the locked rotor torque of the 3 HP motor I referenced (and other 3 HP motors could have greater or lesser torque with a locked rotor) we see:
F = 3.612 * 45 = 162.54 pounds.
My original back of the envelope calculations were very much in error and I apologize to all who have read it. Thank you again for pointing it out.
I would have to take a much closer look at the table supports, bearings and support for the lower wheel, and the torque characteristics of the specific motor to be used before I could comfortably recommend using a 3 HP motor on the saw.
As you say, that lift would have been much easier 30-40 years ago, but I also could do it - if I can get a good grip on it. However, attach that 70 pounds to the end of a 1/2 to 3/4 by .035 strip of steel. Can you pinch that strip between your thumb and finger like you would a bandsaw blade and lift the 70 lbs? If you can, you probably one of those people who crack pecans using just your thumb and forefinger. I know I can't - except maybe the "papershell" variety.
Anyway, the point is moot since the 70 lb figure was badly miscalculated and is closer to 170 than it is to 70.
Jet uses a proprietary mounting not a standard NEMA face. When I burned out the motor the first place I looked was Granger. I thought I could fab a new mount but decided I didn't want the extra challenge.
To make matters worse the bolt holes are in a diamond pattern not square. I don't know why Jet made the decision not to use a standard mount. I guess they want my return business...
I called Jet and they could not give me any information as to weather the 3hp would work or not. Nobody has tried it apparently. The 3hp will mount to the saw because the mounting brackets on both the 16" and the 3hp 18" saws are the same. Only the pulley that attaches to the motor needs to be replaced, because of different shaft sizes. Other than that the mounting is the same.
As to the motor sizes of other saws, I had found that most saws this size have a 1.5 hp motor. I found a 14" (can't remember the manufacture) that had a 2hp motor. Jet's standard 18" model comes with 1.75hp with the option of a 3hp.
Did some work for them at MSFC Huntsville back in the early '70s on the Space Shuttle Main Engine (SSME) Controller and Saturn V Launch Profile. Got tired and disgusted with the bureaucracy and left to do non-government stuff..
Well, of course I would use a vise grips pliers if I was inclined to actually attempt this. But since you mention it, 30 years ago, I could crack a pecan by hand. :)
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