Motor starting jolt

Nelson Collar

Maybe start the motor with the drive to your lathe disengaged. After the motor is up and running engage and run the lathe. The application  that motor is designed for, it will have that torque start because the way it is wired. I would just use it and and enjoy the lathe.
Nelson

On Monday, December 25, 2017, 5:31:21 PM EST, Steven Schlegel sc.schlegel@... [SOUTHBENDLATHE] wrote:

Would it be best to add resistance to the starting windings or in series with the capacitor? Based on the math, that wouldn't affect the phase, it would decrease the current in the starting winding, and is dirt cheap.

I'm way out of my league here, so please, everyone, provide some comments on what I just said.

Steven

On Dec 25, 2017 1:16 PM, "'Jim B. ' Jim@... [SOUTHBENDLATHE]" wrote:

Be careful about REDUCING the capacitance.

The starting circuit is a series RLC circuit.

The REACTANCE of a capacitor INCREASES as the capacitance go’s down.

X= 1/(2*pi*f*C)

It also cares a negative sign.

So Z= R+ X(l)-X(c) Where Z is the total reactance of the starting circuit.

This, smaller capacitator, COULD increase the starting current.

It depends on which side of resonance you are.   Resonance is when (X(l)=X(c))

If the manufacturer could save money by supplying a smaller capacitator without effecting reliability I think they would.

The starting circuit provides a local phase that is phase shifted from the house phase. This creates a rotating field that starts the motor. Without it, the local phase,  the roter would rotate to the nearest stator field and lock there.

The ideal situation for maximum torque would be when X(l)=X(c). This would produce 90 degrees of shift.   At this point the current through the starting field would be maximum.. Due to manufacturing variations  and cost considerations this may or may not be your case.

I would try paralleling another capacitor with clip leads to see if it helped. Bigger C means less reactance and a starting field with less phase shift so, perhaps, less starting torque.

Of course going to a small cap will eventually result in a large capacitive reactance which will have a similar effect. A very small cap would resemble an open circuited capacitator  in the starting circuit.

A very large capacitator would resemble a shorted capacitator in the starting circuit.

Jim B.

 Virus-free. www.avast.com

Oren

Thanks Gary for taking the time to research my exact motor. I ran the experiment with a long extension cord and noticed some improvement, but still unsatisfactory jumping motion at startup. I finally found a really cheap 2wire extension cord and with the aid of an old 3 to 2 wire adapter added it to the line...voila! It now is smooth at startup.
I must say I’m baffled. If the start capacitor is 10 times the run capacitor, I don’t see how a reduction in line voltage would reduce the large surge coming from the start capacitor. I’m assuming the start capacitor is fully charged prior to switching the motor on, perhaps this isn’t the case? If the start capacitor has a bleeder on it and is uncharged when the motor is switched on I get it, but I would think there would be a delay for the capacitor to charge prior to the jumping around...it feels instantaneous.
I guess I don’t really have to understand why, but now I need to know how to wire the thing. Do I buy a resister and place in the hot side of the line input? Any guess as to what size? Will I be reducing my running power or generating significant heat? Obviously I’m still over my head on this.
I guess this experiment proves that a good motor starter would work, but they appear more expensive than selling this motor and buying a different one.
Thanks for all your help and to everyone who has responded.
Oren

ww_big_al

Oren,

Before you go any further take a volt meter and measure the voltage at the receptacle. Measure between the hot -> neutral and Hot -> ground. In one garage I had a 120v receptacle wire for 240v. Also you may have a power problem in your house. That’s not common but it does happen.

AL

From: SOUTHBENDLATHE@... [mailto:SOUTHBENDLATHE@...]
Sent: Thursday, December 28, 2017 1:55 PM
To: SOUTHBENDLATHE@...
Subject: RE: [SOUTHBENDLATHE] Motor starting jolt

Thanks Gary for taking the time to research my exact motor. I ran the experiment with a long extension cord and noticed some improvement, but still unsatisfactory jumping motion at startup. I finally found a really cheap 2wire extension cord and with the aid of an old 3 to 2 wire adapter added it to the line...voila! It now is smooth at startup.

I must say I’m baffled. If the start capacitor is 10 times the run capacitor, I don’t see how a reduction in line voltage would reduce the large surge coming from the start capacitor. I’m assuming the start capacitor is fully charged prior to switching the motor on, perhaps this isn’t the case? If the start capacitor has a bleeder on it and is uncharged when the motor is switched on I get it, but I would think there would be a delay for the capacitor to charge prior to the jumping around...it feels instantaneous.

I guess I don’t really have to understand why, but now I need to know how to wire the thing. Do I buy a resister and place in the hot side of the line input? Any guess as to what size? Will I be reducing my running power or generating significant heat? Obviously I’m still over my head on this.

I guess this experiment proves that a good motor starter would work, but they appear more expensive than selling this motor and buying a different one.

Thanks for all your help and to everyone who has responded.

Oren

Oren

I had the same issues on the bench when I was wiring the motor so pretty sure it was a motor issue, not a circuit issue. But following your suggestion I just checked the outlet where the lathe plugs in...both hot to neutral and hot to ground read 110 on the nose. I probably should have started by checking the outlet. Thanks for the advice.

Ondrej Krejci

By using an extension cord, increasing the resistance and lowering the voltage to a single phase induction motor, eventually the motor will burn up.
Leeson generally makes motors for heavy duty applications; i.e. hard to start loads that require high torque.
Switching starting capacitors may or may not work.  You can take the motor to a repair shop for real advice.
There´s no logic behind wasting money on a VFD, unless you want to rewire the motor to run on three phase, if possible.
The best solution is to buy a motor rated for your particular application.

Best of luck,

OK

On Thursday, December 28, 2017 2:49 PM, "'arknack' arknack@... [SOUTHBENDLATHE]" wrote:

Oren,
Before you go any further take a volt meter and measure the voltage at the receptacle. Measure between the hot -> neutral and Hot -> ground. In one garage I had a 120v receptacle wire for 240v. Also you may have a power problem in your house. That’s not common but it does happen.
AL

From: SOUTHBENDLATHE@... [mailto:SOUTHBENDLATHE@...]
Sent: Thursday, December 28, 2017 1:55 PM
To: SOUTHBENDLATHE@...
Subject: RE: [SOUTHBENDLATHE] Motor starting jolt

Thanks Gary for taking the time to research my exact motor. I ran the experiment with a long extension cord and noticed some improvement, but still unsatisfactory jumping motion at startup. I finally found a really cheap 2wire extension cord and with the aid of an old 3 to 2 wire adapter added it to the line...voila! It now is smooth at startup.
I must say I’m baffled. If the start capacitor is 10 times the run capacitor, I don’t see how a reduction in line voltage would reduce the large surge coming from the start capacitor. I’m assuming the start capacitor is fully charged prior to switching the motor on, perhaps this isn’t the case? If the start capacitor has a bleeder on it and is uncharged when the motor is switched on I get it, but I would think there would be a delay for the capacitor to charge prior to the jumping around...it feels instantaneous.
I guess I don’t really have to understand why, but now I need to know how to wire the thing. Do I buy a resister and place in the hot side of the line input? Any guess as to what size? Will I be reducing my running power or generating significant heat? Obviously I’m still over my head on this.
I guess this experiment proves that a good motor starter would work, but they appear more expensive than selling this motor and buying a different one.
Thanks for all your help and to everyone who has responded.
Oren

Oren

On further examination, I’m pretty sure my Leeson 110088.00 is not capacitor start capacitor run, rather it is capacitor start induction run...not sure if this would change the analysis or not...the small gauge extension cord definitely smoothed it out...
Thanks,
Oren

Nelson Collar

running on a less than proper wiring will burn it up way before its time.

On Thursday, December 28, 2017, 6:34:53 PM EST, obolt@... [SOUTHBENDLATHE] wrote:

On further examination, I’m pretty sure my Leeson 110088.00 is not capacitor start capacitor run, rather it is capacitor start induction run...not sure if this would change the analysis or not...the small gauge extension cord definitely smoothed it out...

Thanks,
Oren

comstock_friend

"Part of the process included a new Leeson 1hp capacitor start motor, which I was really looking forward to. But, the damn thing starts with such a jolt that it almost seems dangerous for the lathe, or at the least, disruptive to doing close tolerance work. "

The South Bend recommended horsepower for 9" A, B and C models is 1/2 HP. You're only twice too big and powerful and wonder why it's hopping around???

John

Oren

Ok, I’ve read a lot and got lots of advice from this board, and talked to my local motor shop. Thought I’d share my conclusions in case anybody else finds themselves with a similar problem.

1 I bought a great Leeson 1hp farm duty motor but it is very high torque at startup and thus a poor choice of motors for this application.

2 Reducing the starting capacitor size on a capacitor start/induction run motor is generally a bad idea. Likewise, Running the motor continuously on low voltage or occasionally on very low voltage is a bad idea.

3 a motor controller would probably solve the problem but costs more than I paid for the used, like new motor (\$100)

4 I wired my shop with heavier gauge wiring than necessary, exacerbating the problem of high startup amperage. An experiment with extension cords showed that the motor could be calmed by reducing line wire size.

5 My16 gauge 8 ft extension cord is rated for 13 amps. My motor draws 14 amps at full load. while running the lathe unloaded the measured voltage at the motor is the full 110 volts. Any voltage drop will only happen while actually cutting. Since typically a 1/2 hp motor is sufficient for my lathe, I’m assuming that if I operate it correctly it should never load the motor more than 50% thus rarely reducing running voltage.

6. So, I’m going to run through my 16 gauge 8 ft extension cord. If I trip the motor thermal protection, I’ll remove the extension cord until the heavy cutting is finished, trying to minimize starting and stopping the lathe.

7. If it all fails, I’m out \$100. At least I haven’t damaged the lathe with the large starting jolts.

Oren

Oren

I couldn’t agree more that a 1hp motor is oversized for this lathe. However, I believe the belts plus proper operating procedure provide all the protection necessary to protect the lathe from any excess horsepower. I already own the motor and I’m trying to use it.
There is no law of physics that makes 1 hp motors start with a jolt and 1/2 hp motors start smoothly.
My old wood lathe was 1 1/2 hp and started smooth as silk.
The problem is with the type of motor, not the hp.

Nelson Collar

Happy New Year

On Friday, December 29, 2017, 2:53:32 PM EST, obolt@... [SOUTHBENDLATHE] wrote:

Ok, I’ve read a lot and got lots of advice from this board, and talked to my local motor shop. Thought I’d share my conclusions in case anybody else finds themselves with a similar problem.

1 I bought a great Leeson 1hp farm duty motor but it is very high torque at startup and thus a poor choice of motors for this application.

2 Reducing the starting capacitor size on a capacitor start/induction run motor is generally a bad idea. Likewise, Running the motor continuously on low voltage or occasionally on very low voltage is a bad idea.

3 a motor controller would probably solve the problem but costs more than I paid for the used, like new motor (\$100)

4 I wired my shop with heavier gauge wiring than necessary, exacerbating the problem of high startup amperage. An experiment with extension cords showed that the motor could be calmed by reducing line wire size.

5 My16 gauge 8 ft extension cord is rated for 13 amps. My motor draws 14 amps at full load. while running the lathe unloaded the measured voltage at the motor is the full 110 volts. Any voltage drop will only happen while actually cutting. Since typically a 1/2 hp motor is sufficient for my lathe, I’m assuming that if I operate it correctly it should never load the motor more than 50% thus rarely reducing running voltage.

6. So, I’m going to run through my 16 gauge 8 ft extension cord. If I trip the motor thermal protection, I’ll remove the extension cord until the heavy cutting is finished, trying to minimize starting and stopping the lathe.

7. If it all fails, I’m out \$100. At least I haven’t damaged the lathe with the large starting jolts.

Oren

Guenther Paul

I agree with Nelson. If this motor has a capacitor i would check if it is the right one. Take it to a electric motor repair shop if you don't know how to sice the capacitor  Happy new year. Don't drink and drive

GP

From: "Nelson Collar nel2lar@... [SOUTHBENDLATHE]"
To: "obolt@... [SOUTHBENDLATHE]" Sent: Friday, December 29, 2017 4:01 PM
Subject: Re: [SOUTHBENDLATHE] Re: Motor starting jolt

Happy New Year

On Friday, December 29, 2017, 2:53:32 PM EST, obolt@... [SOUTHBENDLATHE] wrote:

Ok, I’ve read a lot and got lots of advice from this board, and talked to my local motor shop. Thought I’d share my conclusions in case anybody else finds themselves with a similar problem.

1 I bought a great Leeson 1hp farm duty motor but it is very high torque at startup and thus a poor choice of motors for this application.

2 Reducing the starting capacitor size on a capacitor start/induction run motor is generally a bad idea. Likewise, Running the motor continuously on low voltage or occasionally on very low voltage is a bad idea.

3 a motor controller would probably solve the problem but costs more than I paid for the used, like new motor (\$100)

4 I wired my shop with heavier gauge wiring than necessary, exacerbating the problem of high startup amperage. An experiment with extension cords showed that the motor could be calmed by reducing line wire size.

5 My16 gauge 8 ft extension cord is rated for 13 amps. My motor draws 14 amps at full load. while running the lathe unloaded the measured voltage at the motor is the full 110 volts. Any voltage drop will only happen while actually cutting. Since typically a 1/2 hp motor is sufficient for my lathe, I’m assuming that if I operate it correctly it should never load the motor more than 50% thus rarely reducing running voltage.

6. So, I’m going to run through my 16 gauge 8 ft extension cord. If I trip the motor thermal protection, I’ll remove the extension cord until the heavy cutting is finished, trying to minimize starting and stopping the lathe.

7. If it all fails, I’m out \$100. At least I haven’t damaged the lathe with the large starting jolts.

Oren

Nelson Collar

Now to add fuel to this subject. I put a Industrial Baldor 1 1/2 hp 1725 on my 10K. I have it mounted under the bench and belt up to a counter shaft in the position of the original motor to drive the horizontal mount drive. I put a two speed pulley on the motor and with that power and the lower rpm make a very nice running machine. I enjoy the speed and the power.
Nelson

On Friday, December 29, 2017, 4:37:39 PM EST, Guenther Paul paulguenter@... [SOUTHBENDLATHE] wrote:

I agree with Nelson. If this motor has a capacitor i would check if it is the right one. Take it to a electric motor repair shop if you don't know how to sice the capacitor  Happy new year. Don't drink and drive

GP

From: "Nelson Collar nel2lar@... [SOUTHBENDLATHE]"
To: "obolt@... [SOUTHBENDLATHE]"
Sent: Friday, December 29, 2017 4:01 PM
Subject: Re: [SOUTHBENDLATHE] Re: Motor starting jolt

Happy New Year

On Friday, December 29, 2017, 2:53:32 PM EST, obolt@... [SOUTHBENDLATHE] wrote:

Ok, I’ve read a lot and got lots of advice from this board, and talked to my local motor shop. Thought I’d share my conclusions in case anybody else finds themselves with a similar problem.

1 I bought a great Leeson 1hp farm duty motor but it is very high torque at startup and thus a poor choice of motors for this application.

2 Reducing the starting capacitor size on a capacitor start/induction run motor is generally a bad idea. Likewise, Running the motor continuously on low voltage or occasionally on very low voltage is a bad idea.

3 a motor controller would probably solve the problem but costs more than I paid for the used, like new motor (\$100)

4 I wired my shop with heavier gauge wiring than necessary, exacerbating the problem of high startup amperage. An experiment with extension cords showed that the motor could be calmed by reducing line wire size.

5 My16 gauge 8 ft extension cord is rated for 13 amps. My motor draws 14 amps at full load. while running the lathe unloaded the measured voltage at the motor is the full 110 volts. Any voltage drop will only happen while actually cutting. Since typically a 1/2 hp motor is sufficient for my lathe, I’m assuming that if I operate it correctly it should never load the motor more than 50% thus rarely reducing running voltage.

6. So, I’m going to run through my 16 gauge 8 ft extension cord. If I trip the motor thermal protection, I’ll remove the extension cord until the heavy cutting is finished, trying to minimize starting and stopping the lathe.

7. If it all fails, I’m out \$100. At least I haven’t damaged the lathe with the large starting jolts.

Oren

rlm_mcv

Put the motor on EBay and sell it, if you dont like how it starts.  Or take it to a motor repair/rewind shop and do some trading for a 1/2 or 3/4.  They might have an instant reverse motor you would truly fall in love with.

Happy New Year

On Friday, December 29, 2017, 1:53:32 PM CST, obolt@... [SOUTHBENDLATHE] wrote:

Ok, I’ve read a lot and got lots of advice from this board, and talked to my local motor shop. Thought I’d share my conclusions in case anybody else finds themselves with a similar problem.

1 I bought a great Leeson 1hp farm duty motor but it is very high torque at startup and thus a poor choice of motors for this application.

2 Reducing the starting capacitor size on a capacitor start/induction run motor is generally a bad idea. Likewise, Running the motor continuously on low voltage or occasionally on very low voltage is a bad idea.

3 a motor controller would probably solve the problem but costs more than I paid for the used, like new motor (\$100)

4 I wired my shop with heavier gauge wiring than necessary, exacerbating the problem of high startup amperage. An experiment with extension cords showed that the motor could be calmed by reducing line wire size.

5 My16 gauge 8 ft extension cord is rated for 13 amps. My motor draws 14 amps at full load. while running the lathe unloaded the measured voltage at the motor is the full 110 volts. Any voltage drop will only happen while actually cutting. Since typically a 1/2 hp motor is sufficient for my lathe, I’m assuming that if I operate it correctly it should never load the motor more than 50% thus rarely reducing running voltage.

6. So, I’m going to run through my 16 gauge 8 ft extension cord. If I trip the motor thermal protection, I’ll remove the extension cord until the heavy cutting is finished, trying to minimize starting and stopping the lathe.

7. If it all fails, I’m out \$100. At least I haven’t damaged the lathe with the large starting jolts.

Oren

carbure2003

I have not read the whole chain of emails

If your motor is running on 220V, start over again the wiring on your motor

The first time I changed voltage on my atlas lathe, the electrician had wired the starting coil like if it was wired on 120V. The result was a very strong noise when starting the motor. The re wiring corrected the problem

---------- Original Message ----------
From: "r m rlm_mcv@... [SOUTHBENDLATHE]" <SOUTHBENDLATHE@...>
To: "obolt@... [SOUTHBENDLATHE]" <SOUTHBENDLATHE@...>
Subject: Re: [SOUTHBENDLATHE] Re: Motor starting jolt
Date: Fri, 29 Dec 2017 22:57:14 +0000 (UTC)

Put the motor on EBay and sell it, if you dont like how it starts. Or take it to a motor repair/rewind shop and do some trading for a 1/2 or 3/4. They might have an instant reverse motor you would truly fall in love with. Happy New Year On Friday, December 29, 2017, 1:53:32 PM CST, obolt@... [SOUTHBENDLATHE] <SOUTHBENDLATHE@...> wrote: Ok, I’ve read a lot and got lots of advice from this board, and talked to my local motor shop. Thought I’d share my conclusions in case anybody else finds themselves with a similar problem.
1 I bought a great Leeson 1hp farm duty motor but it is very high torque at startup and thus a poor choice of motors for this application. 2 Reducing the starting capacitor size on a capacitor start/induction run motor is generally a bad idea. Likewise, Running the motor continuously on low voltage or occasionally on very low voltage is a bad idea. 3 a motor controller would probably solve the problem but costs more than I paid for the used, like new motor (\$100) 4 I wired my shop with heavier gauge wiring than necessary, exacerbating the problem of high startup amperage. An experiment with extension cords showed that the motor could be calmed by reducing line wire size. 5 My16 gauge 8 ft extension cord is rated for 13 amps. My motor draws 14 amps at full load. while running the lathe unloaded the measured voltage at the motor is the full 110 volts. Any voltage drop will only happen while actually cutting. Since typically a 1/2 hp motor is sufficient for my lathe, I’m assuming that if I operate it correctly it should never load the motor more than 50% thus rarely reducing running voltage. 6. So, I’m going to run through my 16 gauge 8 ft extension cord. If I trip the motor thermal protection, I’ll remove the extension cord until the heavy cutting is finished, trying to minimize starting and stopping the lathe. 7. If it all fails, I’m out \$100. At least I haven’t damaged the lathe with the large starting jolts. Thanks for all your advice.Oren
____________________________________________________________
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Jim_B

One thing that has not been mentioned.
Loosen the belt.
Start the motor as it is.
Then tighten belt.
An extra step but no excess torque.

Sent from my iPhone-8
Jim B,

eddie.draper@btinternet.com

I wondered when someone was going to come up with that one!  I habitually use the belt tensioner as a clutch on my Myford ML7 and it works just fine, but that has a V belt drive.  Not yet discovered a down side to this approach apart from wear to the cam, which I've had to remedy by welding only once and took all of several minutes.

I tried it on our railway's SB 14.5" with underdrive by flat belt, and the belt doesn't always stay in place when it comes time to apply the drive.

I would point out that 3 phase motors also have a wide range of starting characteristics, not just single phase ones, and selection is again application dependent.  I noted in an earlier posting that the troublesome motor was described as "farm" rating.  Not an entirely helpful description!
Eddie

From: "Jim Jim@... [SOUTHBENDLATHE]"
To: SOUTHBENDLATHE@...
Sent: Saturday, 30 December 2017, 3:17
Subject: Re: [SOUTHBENDLATHE] Re: Motor starting jolt

One thing that has not been mentioned.
Loosen the belt.
Start the motor as it is.
Then tighten belt.
An extra step but no excess torque.

-8
Jim B,

George

The "farm duty" term is very helpful. It's very common in the US. Look at the WEG motor site for a complete description.
GEO.

On Saturday, December 30, 2017 3:10 AM, "Edward Draper eddie.draper@... [SOUTHBENDLATHE]" wrote:

I wondered when someone was going to come up with that one!  I habitually use the belt tensioner as a clutch on my Myford ML7 and it works just fine, but that has a V belt drive.  Not yet discovered a down side to this approach apart from wear to the cam, which I've had to remedy by welding only once and took all of several minutes.

I tried it on our railway's SB 14.5" with underdrive by flat belt, and the belt doesn't always stay in place when it comes time to apply the drive.

I would point out that 3 phase motors also have a wide range of starting characteristics, not just single phase ones, and selection is again application dependent.  I noted in an earlier posting that the troublesome motor was described as "farm" rating.  Not an entirely helpful description!
Eddie

From: "Jim Jim@... [SOUTHBENDLATHE]"
To: SOUTHBENDLATHE@...
Sent: Saturday, 30 December 2017, 3:17
Subject: Re: [SOUTHBENDLATHE] Re: Motor starting jolt

One thing that has not been mentioned.
Loosen the belt.
Start the motor as it is.
Then tighten belt.
An extra step but no excess torque.

-8
Jim B,