Tuesday, August 07, 2007

Corally SP12X Diff Nut Trick

I have noticed a few people suffering from the diff nut coming loose on the SP12X. Unlike other diffs, the Corally uses a carbon nut on a carbon threaded shaft. There is no lock nut as such and the location of the diff nut is reliant on the nut/thread friction and the grip offered by the serrated locking washer.


The Corally diff is one of the best I have used with a great smooth and reliable action provided by the outer thrust race that comes as standard. I have a tip here that will solve or prevent the diff nut coming loose. Before we start be warned!!!!

Warning 1. The tiny thrust race balls are NOT captive within the spacer and its "game over" if these go on the carpet!

Warning 2. I am going to do stuff with superglue, fingers, carbon parts and tissue paper. We need to make sure that all 4 of these components are separate at the end of the process.

Step 1. Read Warning (1) above and strip your diff down. We want the shaft.

Step 2. Place a small drop of super glue on the threaded part of the shaft and then quickly and evenly wipe it into the thread with tissue paper, forming a smooth and thin (very thin) layer coating of super glue over the thread. Do not allow super glue to touch the non threaded parts of the shaft.






We are not looking to fill up the thread groves with glue here. The objective is to use the glue coating to slightly oversize the thread.

I used a standard viscous super glue off the DIY shop shelf. I would worry about the "Orion" type of watery thin cyano that is popular for mounting rubber tyres. Introduce a drop of this and it can capillary itself all over the the thread, the shaft, your car, your fingers and the work table! That's Warning (3).

Step 3. Wait Wait WAIT for the glue coating to fully dry before you try the nut on the thread. You really do not want to superglue the nut to the shaft here! Try the nut on the shaft, it will now feel tighter. Ideally you want it to fell tight enough to be difficult to turn using your fingers alone but easy with your diff spanner. I repeated step 2 a couple of times until my nut was "locky" enough.

Step 4. You may now find the spur gear bearing will not pass over the thread as you have slightly increased the outer diameter with the super glue coating. This is easy to rectify. Just rotate the shaft by hand while holding the thread with some fine abrasive paper wrapped around it. This will remove some of the super glue and reduce the outer diameter of the shaft whilst keeping the coating in the thread groves.

Job done!


A final tip. I alway loosen the diff off after the end of a meeting. This prevents the O ring being over squashed and distorted.


Cheers


Mark

3 comments:

Matthew said...

awesome tips, keep them coming :)

I too have an sp12x (Corally spec)
running the standard front though :)

James said...

Hi Mark

I run CarpetOval.com, a forum for 1/12th oval racers, and I LOVED your article on how to fix chunked tyres, it was brilliant. Actually, I found your site when looking forsetup advice for an L4 rear end, which I run on one of my oval cars, and that too was really helpful.

I was wondering if you'd have any objections to me posting your article on fixing chunked tyres on my site for our 4000-odd members to enjoy - it's a really great How-To. You'll be given proper credit and a link back to your blog, of course....

Thanks

James
CarpetOval
theflame@gmail.com

James said...

Hi Mark

I run CarpetOval.com, a forum for 1/12th oval racers, and I LOVED your article on how to fix chunked tyres, it was brilliant. Actually, I found your site when looking forsetup advice for an L4 rear end, which I run on one of my oval cars, and that too was really helpful.

I was wondering if you'd have any objections to me posting your article on fixing chunked tyres on my site for our 4000-odd members to enjoy - it's a really great How-To. You'll be given proper credit and a link back to your blog, of course....

Thanks

James
CarpetOval
theflame@gmail.com