Tuesday, February 18, 2014

Removing a Supernova Balance Wheel

The first time I had to remove the balance wheel from a Necchi Supernova, I was a bit confused.  I removed the nut but there was no torque washer underneath and the balance wheel would not come off the shaft tail.  When I finally learned, I took photos and now Frank is having the same issue so I decided to post those photos to help Frank and anyone else who hasn't figured this out yet.

STEP 1 - Loosen the two screws in the knurled nut and unscrew.

STEP 2 - The entire inner circle is the torque washer.

STEP 3 - Slide the washer off the shaft.

STEP 4 - Remove the belt and slide the balance wheel off the shaft tail.

Installation is the reverse of removal. If the balance wheel does not spin freely when winding a bobbin, try swapping the two screws in the knurled nut. One is longer than the other and that's how Necchi solved the problem of the torque washer being installed backward.


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Cheryl's Teapots2Quilting said...

Thanks. I really need to pull mine out and start cleaning her up.

frank_oc said...

Ed, your the best!
I'll try this over the weekend. It had me stumped. This along with the presser foot lift-tension adjustment will get my Supernova up to near perfect.

frank_oc said...

Well it turned out not to be quite that straightforward. When I removed the stop motion knob, the torque washer/plate did not budge.

Thanks to your confirmation that everything should be able to slide off together, I embarked on using a bearing puller to get both the balance wheel and torque washer/plate off together. I used a bearing puller that was large enough to reach behind and grab the balance wheel at the belt pulley shoulder, rather than pull from the outside rim. The screw shaft on my puller has a cone shaped bearing at the tip that was too large to fit through the torque washer, so I had to find a spacer that would allow the puller to push farther away from the shaft. A 7/16 nut was just right.

The balance wheel and torque washer/plate came off nicely. I expected to see more crud and/or corrosion built up, but I guess what little was there was enough to keep it from working. The way it seems to work is the stop motion knob presses the torque washer and balance wheel together against a clip on the shaft to lock things together. Although the torque washer doesn't rotate on the shaft, it has to slide back and forth to release the pressure. I cleaned the shaft and the inside of the bore surfaces with 2000 grit wet/dry sandpaper, wiped everything clean, Triflow sparingly all around.

Anyone who tries this, pay attention there is a thrust washer between the balance wheel and the shaft clip, and another between the balance wheel and the torque washer plate. I filed those flat, as they had some minor burs on them.

It is back together and working as it should. Back off on the stop motion knob, and the balance wheel spins without engaging the needle mechanism. Hooray!

I was surprised to find a groove on the inside of the balance wheel bore with a wick in it. The only way to oil it seems to be to remove the balance wheel. I'll try to remember to do it once a year or so.

Ed, thanks for the confirmation on the approach, and the confidence to forge ahead.