I need some help with a motor problem.

[Rata222]

I purchased a used 1/3 HP 1725 (sleeve bearings) motor to use on a drill press restoration. The motor/drill press runs fine at the three lower speeds - even under the load of drilling steel. The motor tachs at 1760 RPM. If I move the belt to the largest pulley on the motor – under no load- the motor will only rev up to 1100 RPM and you hear the centrifugal switch open and it will stay at that speed - for the few moments I dare run it.

If I remove the belt from the drill spindle pulley, the motor revs up to the 1760. I attempted to put a load on the motor, by pressing wood against the pulley, and it doesn’t bog down.

The start capacitor tested OK with ohm meter – but I replaced it anyway since it looked like it was starting to leak. I doubled checked the wiring per the diagram on the motor. I had put new bearings in the drill spindle on rebuild - it turns very smoothly – so I don’t believe that is the culprit.

The only thing that I can think of is with the larger drive pulley, is that he motor is starting slowerand the centrifugal switch is opening to soon) or Maybe being in the vertical position? Needs stronger springs? I know sleeve bearing are not the best to run vertically.

Does anyone have any ideas about what might cause this? Or what I might try to fix it?

Thanks. Jim

 

[jbobb1]

How's your belt tension when in this position?

 

[Rata222]

How's your belt tension when in this position?

I didnt think the belt seemed too tight. I can switch the belt between pullies fairly easily -But I have no more adjustment left to loosen it any more. With that thought - I will get a cogged belt (not as stiff) about an inch longer - and see if running the belt looser has an affect.

Thank you for that input - I had not even considered belt tightness or stiffness affecting the torque required to get the motor up to speed.

Jim

 

[jbobb1]

So, if you move back to the previous position, the motor starts as it should?
I would say if that's the case, you can rule out the possibility of start switch issues, as in the contacts being stuck together and the motor not getting out of the start circuit.

 

[markba633csi]

How about if you lean the drill press over so the motor is horizontal? See if perhaps the vertical position has anything to do with it.
Usually, ball bearing motors are used for applications like this, but it shouldn't affect the starting torque THAT much I would think
It's possible that one of the windings is partially shorted and isn't producing the full magnetic field. It's also possible that the original capacitor was already replaced once with a too-small value unit- I had this issue a while back
Also, is there an unusual amount of friction in the drill press spindle itself? I'm guessing you checked that already
-mark

 

[Rata222]

How about if you lean the drill press over so the motor is horizontal? See if perhaps the vertical position has anything to do with it.

Great Idea. I considered that the vertical mounting of the motor as a possible cause for problems - But I never thought about laying the drill on its side. So thank you. I tried that tonight. It did not fix the problem - but I can at least eliminate that aspect as the problem.

It's also possible that the original capacitor was already replaced once with a too-small value unit-

That is another thing I hadn't considered. I searched the motors model number for specs - but the results were sparse. - but will keep looking.
The new belt should be here tomorrow - Hopefully having a longer belt - allowing me to reduce tension- and the more flexible cogged style belt will allow the motor to spin up faster.
It seems odd that In the highest drive - The centrifugal start coil switch opens and the motor runs at 1100 RPM.
At what RPM should it open? Maybe stronger springs could be used to increase the RPM where the weights throw the switch.

Thanks all for your input, I will stay on it.
Jim

 

[Technical Ted]

Is there enough room in the drill press housing to flip both the pulleys? Currently, it is setup so the fastest speed is farthest away from the motor's bearings so there is more mechanical leverage working against the motor bearings. If you reverse the pulleys the fastest speed would be closest to the motor's bearings and you can see if this changes things. If it does, I would suggest checking the bearings and motor shaft for wear and proper lubrication.

If there is't any room to do this, it might still pay off to check the bearings and motor shaft, because it kind of sounds like a mechanical problem, not an electrical one. Also, check the spindle bearings to see if there is a lot of drag. A 1/3 HP motor may be a little on the small side. I have a 3/4 HP on my drill press and maybe the motor is just a little small? It looks like a fairly small drill press so maybe the HP is fine.

Just throwing out some thoughts...

Good luck,
Ted

 

[markba633csi]

Good idea about the springs- I can see why that might make sense. Worth a try
Also agree with Ted, 1/3 hp might be on the low side

 

[Winegrower]

The motor sounds fine. Look at the ratio of pulley sizes when the motor is on the large diameter. There must be a 3:1 ratio, looks like to me. That would mean spinning the spindle at about 1760*3=5280 rpm. Do you really need to do that? Perhaps just forget the higher speed and move on with other projects.

 

[markba633csi]

Winegrower has a point