Seeking help w/Grizzly 9729 Motor

[kennycrawford]

I own a Grizzly 9729 that I purchased new just over 2 and 1/2 years ago. Being my first machine I was pretty happy with the lathe aspect but disenchanted with the milling part. Long story short I now own a 9x19 lathe a BF20 mill and a Taig set up. Like I mentioned the 9729 as a lathe I thought was good.....until last week when the motor decided to not consistantly start. It also started making a "sparking" noise on start up. The motor will function if you start it spinning before energizing the start button. I even made a cut on it to see if the motor was producing power. I cleaned up the start motor contacts with a point file, because I found them pitted but that did not fix it. The capacitors don't show any signs of damage but then again I don't know if they would. I would not be opposed to using this opportunity to upgrade to a variable speed system but have no experience and don't know where to start. Any advice would be appreciated as to what some viable options may be.

Thank you,
Kenny

 

[Wizard69]

Hi Kenny;

There is a very good chance that the capacitor is shot. Chinese capacitors aren't known for durability.

The other possibility is that the centrifugal starter switch is hanging up. If you had the motor apart to inspect the contacts you could have checked the switch mechanism then. The idea with a capacitor start motor is that the cap is in circuit when the motor first starts. After the rotor ramps up to speed the switch should open.

By the way if the switch doesn't open you can burn out either the cap or start winding. So you should inspect the entire start circuit before randomly replacing the cap. If you don't have instrumentation you can always swap in a new cap and hope as a cap is a few buck as opposed a new motor.

To be honest I'm not convinced there is a lot of wisdom in repairing the Chinese motors on these machines. They are often of poor quality and over rated power wise. You would be better off buying a good USA made single phase motor.

Your other option is to install a VFD and put a three phase motor on the machine. This gives you the advantage if variable speed, soft start and other VFD features.

I own a Grizzly 9729 that I purchased new just over 2 and 1/2 years ago. Being my first machine I was pretty happy with the lathe aspect but disenchanted with the milling part. Long story short I now own a 9x19 lathe a BF20 mill and a Taig set up. Like I mentioned the 9729 as a lathe I thought was good.....until last week when the motor decided to not consistantly start. It also started making a "sparking" noise on start up. The motor will function if you start it spinning before energizing the start button. I even made a cut on it to see if the motor was producing power. I cleaned up the start motor contacts with a point file, because I found them pitted but that did not fix it. The capacitors don't show any signs of damage but then again I don't know if they would. I would not be opposed to using this opportunity to upgrade to a variable speed system but have no experience and don't know where to start. Any advice would be appreciated as to what some viable options may be. Thank you, Kenny

 

[kennycrawford]

If I were to want to swap out to a VFD motor, any advice on motor and compatible electronics. Would a DC motor work as well?
Kenny

 

[Tin Falcon]

I believe a dc motor would need a PWM (pulse width Modulator)
Canadian horsepower IIRC posted the schematics for one.
Tin

 

[Wizard69]

If I were to want to swap out to a VFD motor, any advice on motor and compatible electronics. Would a DC motor work as well? Kenny

As for a DC motor, it would certainly work but you may not have the performance you want. Cost wise there probably isn't a huge savings going with a DC motor. The controller will likely be a bit cheaper but the motors are likely to cost a bit more. In the end I'm not sure they are worth the trouble.

As for an AC motor, you need to find out what frame size motors the machine supports. If you want to put in a single phase motor to run with the same pulleys and so forth you need to know shaft size and horse power. It is possible that the motor is a metric frame motor but don't rely upon that.

If you want to go the three phase route it is a little more involved. First to get the power in the lower RPM range you need to size a larger motor than the machine came with. This may mean a three horse power motor in place of a one horse power. Then you have the issue of physically fitting the motor to the machine, new pulleys or boring out the old. As for the controller it needs to be sized for the motor.

 

[Philjoe5]

When the motor on my Grizzly 10 x 22 went south I took the opportunity to get lower spindle speeds by rigging up a 5:1 speed reducer coupled to a single phase AC motor.



The gearbox cost $100 USD and is going strong after almost 2 years. The motor is a Leeson ($200 USD). I was worried about coupling US dimensioned pulleys/belts/motor frames with metric stuff. No worries, you can make it all work together.

My mod is uncommon, most folks going the VFD route. I chose this mod because "It's as honest as a stove bolt". Everything is easy to get at and fix though I haven't had the need yet. Plus, now I have a low end spindle speed of 80 rpm.

Cheers,
Phil

 

[canadianhorsepower]

. The capacitors don't show any signs of damage but then again I don't know if they would.
to test your capacitor , disconnect the wires and short the terminal If it spark real bad it's good. if their is no
spark it's dead.
I would not be opposed to using this opportunity to upgrade to a variable speed system but have no experience and don't know where to start. Any advice would be appreciated as to what some viable options may be.

I don't know what part of the world your in but a simple and easy swap it replacing everything with a thread mill set up. You can get a used mill for $80.00 dollars Canadian and you have the motor pulley speed control board and 1.5 hp motor hard to beat

 

[kennycrawford]

Thanks for the ideas. I will check the capacitors today. I like the VFD idea and if I went that route I would not try and keep the motor in it's OEM location. My issue with VFD is lack of knowledge. The lathe is reversible in stock form with safety switches and relays that I am sure would give me an ulcer before I figured it out. I am looking at the treadmill option as I do have a motor that may work. The controller I do not have. Then there is all of those stock safety switches and relays again.

Thanks again,
Kenny