15 replies to this topic

[chasbeeman]

Recently was upgrading one of the JK 1/32 F1/Indy type flexi chassis and had purchased some NOS 64 pitch bronze crown gears. I believe that the pinion I used was Faas or Koford, the mesh didn't feel smooth and was wondering who the original manufacturer of the crown gears was.

I'm needing some advise on matching the correct pinion to avoid damaging the gear. I know that these gears were for F1 Rurosport cars so if any Eurosport racers could advise on how to smooth out the mesh it would be greatly appreciated!

[garyvmachines]

Hay Chazz,

Try running the pinion and crown together... slowly... and use toothpaste as lube.
The grit in the tooth paste should seat them...

If it works you owe me one of those gears!!!
 
GAV

[Cap Henry]

Are they 72 pitch possibly?

[Bill from NH]

Those crown gears were made by Sonic. They are 64 pitch. We used them in the early 2000s on some Plafit-powered 1/32 scratchbuilt F1s.

[chasbeeman]

Don't think a 72 pitch crown exists but not 100% sure. The teeth look to be 64.

[MSwiss]

They are Sonic.

When we raced the Red Fox F1 cars, one or two guys used these.

I don't remember if they used a 64 or 72P pinion.

[MSwiss]

PS: Whatever it was, they would have used GT1, which later became ARP.

Your mesh might be somewhat predicated by the arm shaft/axle alignment.

[Phil Hackett]

Sonic made them. There weren't that many made and it's amazing to me they still show up 15 years later. They were cut as 64 pitch but because of the geometry of the gears, needing to have XX number of teeth with a given size OD, they didn't mesh well with the smallest 64p pinions. Some racers found that 80 pitch pinions worked well with them. 72 pitch wasn't available at the time.

 

As for the "proper" pinion: use what works! That bronze is some pretty tough stuff.

 

Also.... be aware... If I remember correctly (IRC) those gears might be offset .020" from centerline of the axle (lower motor shaft relativ to axle) so that might also be a reason for the unsmooth mesh.

[chasbeeman]

Thanks Phil. I will experiment with the offset and check again. I had originally been using a 7 tooth pinion and what you described about the geometry may be the answer. I'm going to try an 8 tooth next.
 

[MSwiss]

What kind of motor are you going to use?

[Phil Hackett]

Thanks Phil, I will experiment with the offset and check again. I had originally been using a 7 tooth pinion and what you described about the geometry may be the answer. I'm going to try an 8 tooth next.

 

The 7t will not work very well at all. If you can use a 9t or larger it would be even better. 8t pinions (on a 2mm shaft) are still a compromise on tooth geometry, 9s or larger are correct geometry.

[chasbeeman]

Hawk 7 is currently the only legal motor per our club rules.

[MSwiss]

I think you'll want to use a bigger pinion.

[munter]

If the gears are offset then they will only mesh nicely on one side of the pinion. Correct?

 

The grit in the toothpaste should seat them...

 

I better check my toothpaste for grit, it has been pretty smooth lately.

[James Wendel]

We currently use those gears for our hardbody club racing program here in Oregon. The gears are are special order item from Sonic. I have had good success with ARP tapered pinions. As mentioned above, 9-tooth works better than 8-tooth, which works better than 7-tooth (7s are not tapered).
 
Truly dedicated racers break-in gear sets with fine valve grinding compound, turning the axle assembly by hand, working the rough spots back and forth until they smooth out. I have done that many times, but I hate using abrasive that close to the motor bushing and axle bearings.
 
The quick and dirty alternative is to set the mesh snug and blip the motor a few times. Back off the gear and you're good to go. Results vary, but often you get good to excellent results with this simple method. It is important that the axle and motor shaft be in the same plane... no hypoid applications.

[Phil Hackett]

The gears you refer to look the same but are not the same as the small gears shown in the picture in this thread. Those small gears (28t?) were specialized.
 
Yes, the offset gears will not really mesh "the otherway." Offset gears are cut to run on"one side" and not the other. For reference, check out an automotive differential and imagine the ring gear on the other side. Won't work (nevermind the spiral teeth) but in the case of slot cars we're making differences in very small increments, not inches.