37 replies to this topic

[Noose]

I posted this in another thread and thought it might be good to create a separate thread / post for it. It works for me and it sure does help prevent motor and bushing burn-outs! I have never lost a gear and always have smooth gear meshes with both hypoid and non-hypoid set-ups. Showing how to do it is good and maybe we can do a little video on YouTube or something.

Note: This applies to the most commonly used Parma crown gears which are plastic. It won't hold true for metal gears.

1) Make sure the axle spins completely free in the bushings or bearings.

2) I make sure the fat end of the angled pinion is towards the motor and the tapered end is toward the crown gear. The teeth of the crown should touch the pinion just ahead of the rear of the pinion (the fat part) . Some like it in the front but I have seen more guys blow gears that way.

3) Set the crown against the pinion and lightly lock the set screw.

4) Turn the axle to see if there is some play all around. Almost all of the Parma crown gears are a bit out of perfect roundness. You need to find the high spot and that is the spot you want to make sure is set with the right amount of play.

5) The crown should just move slightly in this spot. If not, use your hand to turn the crown away from the pinion a bit and check again until you feel you have it right.

6) Lock the crown down and check the play all around again.

7) With a power pack hooked up, turn up the power until the motor starts to turn over slowly. Take a lighter and put the flame along the teeth and pinion for a short period of time. You can literally hear the the sound get quieter.

Do not overheat of course or you are going to melt the gear.

Works every time for me.

Also, I keep my gears separate. Gears used in hypoid position with Pro Slots or Falcons are kept separate from those aren't and separate from those used on TSRs, which turn the opposite way.

Added note: This is all meaningless if your chassis is weak in the back and you slam into someone/something or vice versa. Minimizing the chance of a bent bracket will always ensure the gear mesh stays good.

[munter]

Number seven..."Take a lighter..."

That's a new one on me but a good one, thanks.

[tonyp]

I suggest a torch lighter like for cigars, works better as you have more control of the flame. A Bic style's flame is blown out of the way by the turbulence created by the gear and tires.

[Noose]

Do your new ones have Lizards on them now instead of skulls?

[tonyp]

Still skulls...

[Noose]

I added he following to the above

Added note: This is all meaningless if your chassis is weak in the back and you slam into someone/something or visa versa. Minimizing the chance of a bent bracket will always ensure the gear mesh stays good.

[Bernie]

Thanks for the tip, Noose. Now I know why a lot of cars sound so much smoother than mine.

[gascarnut]

Added note: This is all meaningless if your chassis is weak in the back

And of course it is all meaningless if you are using Sonics or some other form of metal gear...

[Noose]

So noted above. Thanks, Dennis.

[One_Track_Mind]

Great info, Joe!

Didn't I read on here somewhere a long time ago about using toothpaste to help smooth out the gear mesh? Not sure if this was for metal gears or plastic? Maybe somebody recalls more then me?

[gascarnut]

Toothpaste does not help much on plastic gears, but will help a bit on bronze or aluminum.

And of course, you need to use a white toothpaste - clear gels won't do anything except make the car smell a bit better.

I have used Sonic aluminum drag gears in a hypoid inline bracket and they work fine after a little break-in with toothpaste or a very fine lapping paste, like a jeweler's paste. The deal with them though is to use the biggest crown gear you can for the ratio you want, so that the teeth do not have to be mutilated as much to adapt to the hypoid offset.

[One_Track_Mind]

And of course, you need to use a white toothpaste - clear gels won't do anything except make the car smell a bit better.

Thank you,

[Pappy]

Take a lighter and put the flame along the teeth and pinion for a short period of time.

Noose, since I don't smoke and I don't have a lighter, can I use a soldering iron?

[Noose]

Get Pablo's mini torch.

[Ron Hershman]

Noose, since I don't smoke and I don't have a lighter, can I use a soldering iron?

Make sure you grab hold of the hot end of the iron real tight.

[Mark Wampler]

I might add, that I spin the motor just as slow as possible without stalling. Now how to clean up the black soot afterwards?

[Noose]

If you have black soot you have the flame too close and the motor turning too slowly. A small amount might appear but it should rub off with your finger when done.

[Mark Wampler]

For non-smokers who don't have lighters (but lighter fluid ) use matches, but maybe investing in a throw-away lighter would make sense.

The speed of motor spin up might be up for some conjecture. It seems that a faster speed with a hot, soft plastic gear could be distorted during break in as opposed to the pinon properly forming an imprint or cast in the plastic.

Yep, I think a YouTube video would be a good idea,

[Bob Appelle]

We use a heat gun, It's much easier to control the heat, and no open flame in the house. I think a hair dryer on high might work also.

Bob

[Phil Smith]

Thanks, Joe! I'll have to try that.

[68Caddy]

Very carefully.

Sorry, I could not help myself.

Nesta

[hotrodlarry]

Sometimes I use valve grinding compound made for real scale engines.

A lighter? That's a new one.

[HarV Wallbanger III]

Just for you guys that have never tried heating the gears with a lighter ( I use a BBQ Bic).

Yesterday I put a new pinion and crown on my 1/32 car. At 5 volts it was showing .43 amps no load and after I did the BBQ on the crown it was showing .39 amps draw and the car was very smooooth... It is also a hypoid set.

Note you can also use the amp reading to get the best setup on your rear axle bushings!

[Zippity]

What is hypoid?

Somebody had to ask.

[HarV Wallbanger III]

Hey Zip...

Hypoid (as we use it here) is the arm shaft centerline is below the axle shaft centerline to allow the motor to sit lower in the chassis and flat. You heat the crown to allow it to re-mold (so to speak) so it will have a nice mesh on the pinion.

NOTE: The plastic 1/32 cars have gears molded in hypoid already to allow for the misalignment.

This is a matter of personal feelings, as some do not use hypoid and some do. I do.