A New Heart for Big Blue

While turning some 20″ platters, I came to the realization that my beloved lathe needs a new heart. Not just any heart, a bigger, stronger, slower heart. Slower?

Yes, a new motor was in order for my lathe. The 2hp is good, but when turning large pieces at low speed, it lacks the torque needed. So, here is where the dilemma begins. My first thought was to get a 3 or 5hp motor with the same nameplate speed as my current/previous motor. But, then I have to replace the VFD (brain) with a unit that can handle the increased amperage of the bigger motor. AHHHHH!!!

Good thing I had more than one thought. Not initially realizing that motors come in many different RPM ranges, I proposed my situation to my local surplus dealer. He pointed to a LARGE 2hp motor that is a 870 RPM model. While he didn’t say it, I know he was thinking “That’s the one I tried to give you before.” DOH!!

So why would I replace my existing 2hp motor with another 2hp motor? The reason is due to the speed rating of each motor. The original is rated at 1700 RPM, while the new one is a 870 RPM unit. The hp rating of a motor is a result of RPM and amperage. This means that the new motor (870 RPM) has twice the torque of other unit! In addition to more torque, I’m still retaining similar spindle speeds on the lathe by putting a larger pulley on the new motor. If you can’t tell, I’m excited! Below are the two motors side by side. They seem to be playing nicely.

Well, that’s the why. Here’s the how.

This motor came with a key already in the arbor. I thought this was excellent until I had to remove it to accommodate the bushing and pulley style I used. So, here is a quick tip in removing a stuck key. DON’T GET A BIGGER HAMMER!!! I used a small plastic face hammer with a tiny screwdriver to try and pop the key out. After not having instant success, I grabbed the penetrating oil. I sprayed down the key and let it soak for a day. The next morning I tried again without success. Now I grabbed a pair of vice grips and a propane torch. After applying heat for maybe a minute I grabbed the key with the vice grips and rapidly tapped the vice grips with the plastic faced hammer. This lifted up the end of the key allowing me to use a small screw driver to pry the key out with little force.

Now on to attaching the pulley. I bought a keyed H-bushing and pulley from surpluscenter.com, mainly because it was affordable and fit my needs.

Having not used this type of pulley before, I did the stupidest thing possible when I initially tried to marry the pulley to the motor. I fully seated the bushing into the pulley and then fruitlessly tried to push the pulley onto the arbor. It wasn’t until this that I realized a H-bushing and pulley is tapered and not intended to be assembled in this manner. Luckily, I was able to separate the bushing and pulley using the jack screw holes on the bushing.

This time, I slid the pulley onto the arbor with the tapped holes facing away from the motor. Next, I slid the bushing in snug to the pulley and pushed the key into place. Now I used the provided screws to pull the bushing into the pulley until tight. I didn’t use a torque wrench, I just tightened until it seemed reasonable for the bolts provided.

It’s amazing how easily things work when you do it right…

Now to heave this beast onto the lathe. Mind you, the “small” motor was 79 pounds. The new motor is 120 pounds. That’s heavy when you have to hold it 5 inches off the ground and hang it on a few bolts. No, I don’t have a hoist or anything that would have made this an easy task. What fun!

Well, other than trowing some new belts on, this upgrade is wrapped up unless you want to hear about wiring… Ok, ok, I’ll tell you about wiring the motor. Before I took the original motor off, I tested the new motor. It is surplus after all, and wouldn’t I have been ill if I’d gone through all that work just to put the original motor back on. So, basically you follow the diagram on the motor for wiring. Use wire nuts and make sure you ground the thing. Ok, done! The heart transplant was a success!

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Comments

Scott Maddox says

May 13, 2016 at 6:57 pm

Mike,

This is WSM…William Scott Maddox, a woodturner from south Mississippi. I am interested in building or having built a large bowl lathe like yours, but unlike you, I have very little experience with such.

Do you or have you considered selling the plans for your lathe? I really like the build and footprint. Hope you will consider sharing your detailed plans for a price.

Thanks for listening,

Scott Maddox
Southern Turnings
Wiggins, Mississippi

- Mike says
  
  May 13, 2016 at 7:07 pm
  
  Hi William,
  
  Yes I do have plans for sale, they’re $200. Rather than copying my plans, I’d encourage you to adapt the approach I used to whatever materials you can acquire easily. I built my lathe the way I did partly because of the materials I had available. Feel free to email me if you have further questions and interest, Mike@woodshopmike.com. I’m glad you like my lathe!

A New Heart for Big Blue

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