Marty wrote:i'm currently working on two RC10 projects. one with 6 gear and the other with stealth tranny. both will get a 17Turn Motor which i already have (Reedy and LRP).
The output drive ratio on the original 6-gear is 1.83:1 and the Stealth is at 2.25:1. You will need different gear ratios to achieve the same final drive ratio (FDR) if you are planning on using identical motors in both cars.
the trouble is .. i need spur and pinion gears. (i only have a 108T Spur and a 21 Pinion)
Well, the trouble is that it looks like you also have a 64-pitch spur gear and a VERY small 64p pinion, if not a 48p pinion. You will definitely need new pinions and spurs for both applications. Using 64p gears on a basher or off road car is a bad idea. The teeth are too fine, which is why 64p is left to carpet cars.
can someone who has a similar setup please let me know a basic spur/pinion "startup combination" - and where i can get it ?!?! ... and if the 17T is the wrong choice for the 6 gear let me know the answer to this problem.
A 17-turn motor will be fine for a 6-gear. We ran modified motors back then down to 11 and 12-turns, but we didn't have the voltage or power of today's motors and batteries.
The 6-gear tranny came with 32-pitch gears, and I think stock was 54t spur and 14t pinion. That was for a stock motor, and made the final drive ratio (FDR) on the 6-gear around 7.05. Keep in mind, that was for motors and batteries from 1985.
If you were using a contemporary 17t motor, you would want a bigger spur and a smaller pinion to compensate for the power curve. At the very worst, an 11 tooth pinion would be a necessity in 32p gears for that.
With 32p gears, you obviously have very limited choice for gearing, as well as being able to buy actual pinions and spurs at the local hobby shop. You can and should convert to 48p external gears on the 6-gear. The same stock setup ratio for 48p gears would be approximately 81/21 to give you a similar FDR of 7.05. An 81t spur is pretty much standard, unless you are using some wild modified motor.
With a FDR number, the higher the number, the "shorter" the gear ratio. This will give more bottom end punch, slower top speeds and longer run times. The lower the FDR, the "taller" the gear ratio, which will give more top speed, less bottom end torque and shorter run times. If any motor is geared too tall, you will overheat it, and potentially damage it. The rule of thumb for modified motors is that the lower the turns you have, the more power it produces, and the "shorter" the gear ratio will need to be to match the motor to the powerband.
For a 48p setup on a 6-gear, with a 17t motor (based on the stock gearing), I would start with a 81t spur and a 17t pinion. You will almost definitely need to adjust up or down from there depending on the motor heat generated and the speeds the car carries. If I recall correctly, our rule of thumb for starting to gear an RC10 with an 81t spur was to pick the same pinion as the motor turn, and work your way up or down from there (i.e., a 15t for a 15-turn motor).
The Stealth has a higher internal ratio than the 6-gear, so you will need to compensate a bit. To get to that "stock" 7.0 FDR with an 81t spur, you would need a 26t pinion [81/26 x 2.25 = 7.0 FDR].
The modified 17t FDR is 8.7 so to get that same FDR on the Stealth you would need an 81/21 [81/21 x 2.25 = 8.68 FDR].
is there a dust cover beside the original which fits the 6gear tranny?
Yes, a few different from JG, Parma and others, but they are increasingly difficult to find in original condition. There was someone here pulling replicas not that long ago, but I don't recall who was doing it.
Again, a bit wordy, but hopefully this helped explain basic gearing and the tranny internal drive ratios.
doug
