How much HP is too much for a 14" Bandsaw?

[CW]

Yes.

[Nova]

It depends. Most 14" bandsaw have a problem providing enough tension for a

3/4" blade without the frame flexing. Given a situation where a 2 HP motor would be beneficial, unless the saw was designed to handle that size motor, the frame of the saw would most likely flex, dropping the tension on the blade and result in a barreled cut. Hopefully that's the worse that would happen.

Grizzly's tech support was iffy on a 1.5 HP on my G1019 and had a definite "no" on a 2 HP.

-- Jack Novak Buffalo, NY - USA (Remove "SPAM" from email address to reply)

[Roy Smith]

The only time you really need the power and tension is when you're resawing, and when you're resawing, there's usually very little material on one side of the blade. So, it seems to me you could solve the frame flexing problem by having a removable strut which could be fitted as a compression member between the upper frame and the table when resawing.

I've never seen such a thing on a bandsaw, but I find it hard to believe nobody else has thought of it before me. Does such a thing exist?

[Larry Jaques]

On Thu, 23 Dec 2004 19:27:06 -0500, Nova calmly ranted:

The motor horsepower shouldn't be of any concern (unless too small.) I'd think the size of blade and the resultant tension required would be the limiting factors.

Did they say why? Were they saying no to the combo or to the larger motor? My guess is the former, not the latter.

[Nova]

Blade friction. When you start resawing lumber where the power is needed a larger motor, say 2 HP will torque the frame. It will still pull the blade through the wood but with the flex the blade will "bunch up" above the drag. A smaller motor will stall before this happens. With my G1019 with the riser i got the distinct impression from Grizzly's tech support it would be risking snapping the frame with a 2 HP motor.

If you mean the combo of the G1019 and a 2 HP motor, yes the saw was designed for a 3/4 HP motor. I don't know if the riser kit figured in, but I imagine it would. The tech says a 1 HP wouldn't be a problem, 1.5 was questionable and 2 HP was out.

-- Jack Novak Buffalo, NY - USA (Remove "SPAM" from email address to reply)

[Larry Jaques]

On Thu, 23 Dec 2004 20:36:43 -0500, Nova calmly ranted:

Blade friction?!? The motor drives the lower wheel which drives the blade and the upper wheel goes along for the ride. Whether you have a 0.5 or a 5.0 hp motor should make little difference, since the weight of the blade and upper wheel will be the same mass no matter what motor.

No, I meant the wider blade and higher tension. But did you tell him you'd be using low-tension Suffolk Timberwolfs? (Or were you?) How much difference in mass could the longer/wider blade make? 8 ounces? That slim margin would easily be quintupled by extra tension on the original bandsaw with the original spring. Inertial mass _can't_ be it.

[Mark Jerde]

Well...... ;-) I made it 2/3 rds of the way to a mechanical engineering degree before switching to computer science. As an "inganeering" student I lernt alot about "conservation of energy" and the like. ;-)

If you hook up a 1 HP motor and it turns the band saw at "X" FPM, and then you hook up a 2 HP (or 10 HP or 100 HP or 10M HP) motor and it also turns the saw at "X" FPM, what is the larger motor doing to consume more electrons? Radiating heat? Shooting arcs in the air? Writing its congressperson? It takes the same amount of power to spin the same machine at the same speed, so if there is a difference in electrons sacrificed by the different sized motors it has to be due to efficiency differences in the motors and/or the motors sending the electrons off to do other things.

When my 14" Jet BS is running but not actually cutting wood, I haven't noticed the motor housing glowing red, or sparks jumping out of the motor, or letters to congresscritters coming out of the motor. Therefore I have to conclude that the motor is consuming only enough electrons to keep the the band saw mechanisms turning at a constanst speed against the forces of friction in the bearings, the unwillingness of the band saw blade to be bent and unbent, and the link belt groaning and complaining as it is bent and straightened. If you ignore internal differences in motors and hook up a

100 HP motor to the same Jet 14" band saw and it also drives the BS at the same speed, it is impossible for the difference of a single electron to flow through my electric meter -- unless the larger motor is shunting additional electrons elsewhere.

When idling at a stoplight, I'll bet a Chevette and a Corvette are

*producing* basically the same HP, even though there is a substantial difference in their maximum HP. ;-)

-- Mark

P.S. Those who finished engineering degrees are invited to correct my mis/mal understandings. ;-)

[Mark Jerde]

File the patent. This looks like one of those "Why didn't I think of that???" things. ;-)

-- Mark

[J. Clarke]

Just picking nits, the Corvette will be consuming more fuel because the larger engine has more and larger bits rubbing together and thus more friction. The difference will be small though.

[Nova]

Start up current. Have you ever seen a 2 HP motor wired for 110 volts dim the lights while it spins up? I agree that once the motor spins up the running current difference is only that needed to keep the more massive armature turning and overcoming more friction of the larger bearings of the bigger motor, but I imagine you could run a 1/2 HP motor for 15 minutes on the current drawn by 2 HP motor on start up alone.

-- Jack Novak Buffalo, NY - USA (Remove "SPAM" from email address to reply)

[Nova]

The blade friction is still there and has to be overcome. Unless the blade slips on the wheels the torque is taken by the frame. Think of it as pushing a rope which is the reason for barreled cuts.

I normally use a 1/2" Timberwolf blade which Suffolk recommended for the saw. I tried there 3/4" and as Suffolk predicted the saw can't handle the tensions produced by the added blade friction of the extra 1/4" blade width while resawing. It is especially noticeable when attempting to saw "green" lumber (i.e. milling short logs into boards) which has more of a tendency to bind the blade.

-- Jack Novak Buffalo, NY - USA (Remove "SPAM" from email address to reply)

[Guess who]

I think that the difference involved occurs when both are under load. A bull and a mouse can pull a small toy behind them a the same speed if the bull takes it slow and easy. If the toy sticks against something, the mouse will stall. The bull will destroy the toy, the something, and anything else that gets in the way. It's smart to not overdo it.

[Larry Jaques]

On Fri, 24 Dec 2004 08:49:06 -0500, Nova calmly ranted:

I think of it as the wheel pulling the teeth down, into the wood. The majority of the tension on the blade is between the table and the bottom wheel on the downward side. Since the wheels are connected, there may be a very minor amount of "pushing", but the fact that the band is laying on the -outside- of the wheels precludes much of that. Any attempt at pushing would simply make space between the blade and the wheel, and that could come only if there was no tension on the blade at all. No, it is my understanding that barrel cuts are the result of insufficient tension on the blade.

The only part I can see being stressed by having a larger motor would be the lower wheel (major) and its bearing (minor). Startup might be quicker, creating higher initial (and inertial) stress, and it would be able to do more work when making heavy cuts while resawing. The upper wheel and frame are merely used as guides for the band.

I just don't buy that C-frame flex thing at all. Wider bands and the higher tension needed to run them would be the only cause of frame stress that I can see. No, I take that back. The frame may have more stress AT the lower wheel bearing mount during heavy cuts. The wheel being slightly deflected upward up would also result in lower tension on the blade, with the tension spring attempting to take up that slack.

Maybe the guy at Griz could expand on his concerns. I'd be very interested (despite having their old heavy-duty 18" G1012.)

Yeah, and they make resaw blades for both green and dried wood, with different set, hook angles, gullet depth, etc. for each one.

[George]

How about this:

The free-wheeling upper wheel gets ahead of the driven, but loaded lower, causing the blade to bunch into the gap. Doesn't take much difference in speed to start the process, which then increases in effect as the bunched part slows....

[Duane Bozarth]

George wrote: ...

The upper wheel isn't free-wheeling, it's driven/pulled by the blade...the blade makes the wheel move, not the other way round...

[Duane Bozarth]

...

You've got it except you're overlooking the fact that the blade is pulling on the outside of the upper wheel which is applying torque to the frame...as the motor applies more power to the blade this gets transferred to a higher load which could in extreme case, cause the support to fail...

[Roy Smith]

On the other hand, the upper wheel has rotational inertia. It's an interesting dynamics problem to figure out exactly what happens if you get the whole system up to speed and then place drag on the downward-moving blade.

[Larry Jaques]

On Fri, 24 Dec 2004 11:57:37 -0600, Duane Bozarth calmly ranted:

How could the inertial mass of the blade and aluminum wheel (under 10 pounds would be my highest guess) cause any more tension on the frame than the tension adjustment spring, which is in the hundreds of pounds? I still don't buy it, but I would like to hear the Griz tech's explanation.

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[Duane Bozarth]

Not a tremendous amount, however, as the mass of the wheel isn't all great...

But, you're correct, it's a fairly complex dynamical system if one accounts for all effects including blade slip, stretch, ...

[Duane Bozarth]

Larry Jaques wrote: ...

It's not the inertial mass we're talking about here...it's the extra torque exerted by the larger motor when more force is exerted (particularly suddenly) by the blade through the material...