Need Help With 1 Hp Motor

JR49 said:
Just had another thought Bob, I've read posts where guys complain about stripping a tooth or two when using a blade with too few teeth on thin material. My motor would certainly stall out, and possibly blow a breaker before it would pull hard enough to break a tooth. What do ya think?
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The momentum of the spinning motor would suffice to break one tooth before the motor stalled.
 
I agree with John. By the time the motor stalls, the tooth is gone.
 
JR49 said:
My H.F. 4X6 bandsaw has the original 1 HP motor that it came with. Don't know how much use it's had as I got it used. Today, while cutting a steel plate 5" wide by 1" thick (this took longer than any piece since buying it), when it got almost to cutting through the bottom, the blade stopped. I assume, as it was cutting through a tooth caught and jammed the blade. I lifted up on the saw and the blade began moving again. I figured that the belt was slipping, because surely, the motor has enough power to slip the belt, especially since I run the belt pretty loose to make speed changes easy. But, to my surprise, it was not the belt, the motor was stopping, and as soon as I lifted the blade up it started turning again. I tried this a few more times and each time the motor stalled rather than slip the fairly loose belt. Are these H.F. motors that underpowered? The motor temp was about 138* F. with a laser thermometer, if that makes a difference. Is this motor junk? I would think with a little more power the blade should have pulled right through the cut. Does this motor have replaceable brushes, and would worn brushes cause the lack of power? I can probably fix it If you electrical gurus tell me what to fix. If need be, I can get a new motor, cause the saw is in really good shape, but I'd rather fix this one if I can. Please Help! Thanks, JR49
EDIT, Forgot to say, blade is 10-14 TPI, so there were plenty of teeth in the cut
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I have the same saw, I would expect the blade to stall cutting thick steel plate.I drip cutting oil into the cut and if the blade stalls ,lift the saw til the blade runs full speed.I rarely change speeds,leave it on the middle pulley.If you cut a lot of thick steel,use the slow speed pulley .
One other thing,especially since you bought the saw used.Change the transmission oil. There are 6 hex bolts on the cover.Remove them and the cover.Get as much of the goop out of the case as you can.Check manual for oil,I believe it calls for 120 weight oil.I bought it at a Napa store.Makes a big difference,especially in cold weather where the motor won't turn over if it is cold in the shop.
I doubt that the motor needs work. My saw is 9 years old ,motor still running strong.

mike
 
JR49 said:
Jim, I can't believe I did this at 10:30pm. Just went out and took a picture, using a flashlight, so quality is poor. Correct me If I'm wrong but this is the only info on the motor, and I think it is saying that this is only a 120 volt motor. Will check back in the morning. JR49View attachment 111487
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Yup, you are correct, 120V only. But the HP marking is a bit optimistic on their part, that is a 1/3 HP motor (maybe a 1/4), not 1 HP. 6.4 AMPs at 120V = just a bit less than 1/3 HP. a 1 HP motor would draw about 13.6 amps.

That explains a lot. That motor would stall easily.

.
 
Is there a capacitor on that motor Jim? Maybe it's toast-
Mark S.
Mt. View, Ca
 
markba633csi said:
Is there a capacitor on that motor Jim? Maybe it's toast-
Mark S.
Mt. View, Ca
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According to the picture on the manual, yes. You could be right, I hadn't thought of that. Good call! :encourage:
 
Unless it is a capacitor run motor, the capacitor is not in the circuit after the motor starts. The symptom of a bad capacitor is the inability to start turning. If the motor starts to stall, the start circuit would kick in again and give some additional torque but at that point, it is probably too late anyway.
 
Another thought, if you are using an extension cord, make sure it is heavy enough. A light gauge cord will decrease the amount of power delivered to an already anemic motor. A 20ft, 16 ga. extension cord will drop your available power by 4% at 6 amps. Every little bit helps (or hurts, depending on your point of view).
 
To add to Jim's comment concerning the hp rating, 6.4 amps x 120 volts is 768 watts which is just over 1 hp. but this is input power. What you are interested in is output power which has to take into account losses in the motor. Some machine manufacturers use the input power in their specs because it makes the machine look better. To make matters worse, some use peak input power. This occurs briefly during startup or when the motor stalls, neither condition being useful in assessing the machine capability. My old Hoover vacuum blatantly claims 3.1 peak hp while the motor plate states 10.1 amps which is about 1.6 hp input. Conversely, my 4x6 saw motor states 3/4 hp output with a current draw of 12.5 amps which equates to about 2hp input and is a lot closer to reality.

The takeaway on this is when you are evaluating a machine, know which power figure the manufacturer is quoting. If possible, try to get the run current spec. The input power is .16 x the input current and the output power will never be as great as the input. Jim's figure of about 35% efficiency is probably a good rule of thumb.

Bob
 
RJSakowski said:
To add to Jim's comment concerning the hp rating, 6.4 amps x 120 volts is 768 watts which is just over 1 hp. but this is input power. What you are interested in is output power which has to take into account losses in the motor. Some machine manufacturers use the input power in their specs because it makes the machine look better. To make matters worse, some use peak input power. This occurs briefly during startup or when the motor stalls, neither condition being useful in assessing the machine capability. My old Hoover vacuum blatantly claims 3.1 peak hp while the motor plate states 10.1 amps which is about 1.6 hp input. Conversely, my 4x6 saw motor states 3/4 hp output with a current draw of 12.5 amps which equates to about 2hp input and is a lot closer to reality.

The takeaway on this is when you are evaluating a machine, know which power figure the manufacturer is quoting. If possible, try to get the run current spec. The input power is .16 x the input current and the output power will never be as great as the input. Jim's figure of about 35% efficiency is probably a good rule of thumb.

Bob
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Good explanation Bob, thank you.
 
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