Crt.5 plastic spur

[lincpimp]

Interesting Brian, I may have found an easier way though...

Here we go, got bored and decided to find a decent plastic mod 1 spur to use. Found this in the tray of oddball spurs that I have laying around: 47t mod1 spur

So I cut the inside out of the plastic gear until it fit over the diff cup. Then took the stock steel spur and ground off the teeth and the smoothed the cup side so that it was flat.

Then I tried to drill the steel spur for holes to mount the plastic spur. That did not work, as the steel spur is super hard. I even tried to aneal the spur to soften it up, that did not work either. I ended up cutting slots with a fiber disk to place the screws. I clearanced the screw side for the countersunk screws and used nuts to hold the plastic spur on. Not pretty, but it works. I plan to clean it up with the dremel and dust it with some paint.

Side pic makes the spur look crooked, but it is not. I plan to have my machinist turn the centers out of a few more of these spurs, as mine is slightly not right, a little bit of wobble side to side, but it runs true front to back.

I then made some thin spacers to raise the bulks off the chassis, as the new gear placement does not fit in the chassis cutout. I like the further forward spur gear, as it gives more rooom to get the pinion on properly.







And a shot of it mocked up with the motor in the crt.5.

Originally Posted by lincpimp

Then I tried to drill the steel spur for holes to mount the plastic spur. That did not work, as the steel spur is super hard. I even tried to aneal the spur to soften it up, that did not work either. I ended up cutting slots with a fiber disk to place the screws. I clearanced the screw side for the countersunk screws and used nuts to hold the plastic spur on. Not pretty, but it works. I plan to clean it up with the dremel and dust it with some paint.

[/IMG]

I have made a some 1/8 scale plastic spur gear adapters similar to this. we didn't used to have the options we have now. I too discovered how hard it is to drill through these parts. What I discover is that you can dremel with a diamond bit in the spot you want to drill. Then you have to use bits designed for hardened steel. Available at most hardware stores. Drill press is a must. Buy at least few of them, they get dull or break and bounce off your forehead so be sure to wear safety glasses. No joke I had one bounce off my forehead at very high velocity.

What I did was take a spur. I think it was an ofna 47t steel spur. I stuck the spur in a drill and spun it against a grinder wheel to remove the teeth as evenly as possible. then drilled the holes to hold on a ofna 51t plastic spur. It worked very well.

It looks very similar to what you have.

[lincpimp]

I had some tin coated bits, but cobalt one would have been better. I actually like the slots, as they let the screw angle a bit, which aids in getting the nuts on. Not much room to work with, I had to use pliers to hold the nut as I screwed it. (can't wait to hear what everyone thinks of that last sentence)

I used a bench grinder to grint the teeth off, then put a screwdriver shaft thru the hole in the spur and held it against the grinding wheel. I used another plastic handle to slow the spin of the spur, and that evened out the area that I ground the teeth off. It is almost perfectly round, and that does not really matter, as nothing touches that edge.