Jammin CRT - middle diff
 

Hello and sorry for my bad english, but i come from germany :neutral:

I have one question:

Can i use the Kyosho 46 tooth nylon spur without any modifications on my CRT middle diff ? And when not, what i have to do ?

My Setup now: 12xl / Kontronik 80-6-18 / gearing 16/62 / on 5s lipo or 16 cells NiMh !!!

With the Kyosho 46 i will use 12/46 or 13/46...

Thanks for your help...

Nova-Neo

Yes the kyosho spur will fit the crt diff cup, you may need a paper gasket, as the crt might use an o-ring to seal with the current steel spur ear. Or you can use some sort of silicone or other glue to make a seal.

Just make sure that you lower the pinion tooth count to compensate for the smaller spur, but it looks like you have already figured that out!

Okay fine, thanks for your help :wink:

I think it works:

Now 62/16 = 3,87 and then 46/12 = 3,83 or 46/13 = 3,53 for a little bit more speed !

I just reused the oring with my kyosho spur and it worked fine. I had to use a 10t on 4s. You might want to get an 11t just incase.

The combination 5s and XL/12 works fine.

I have more rpm with this as with the combination 4s and XL/10 ore ist this a error in my reasoning !

I think 5s and Xl/12 is a little bit to much :oops:

You have about 1k rpm more with the 12xl on 5s. Still a bit low on the motor speed though, 25k rpm is about 10k rpm less than most run the xl feigaos at.

Sorry my mistake, i want to say XL/11 !!!

@lincpimp:

what do you think is the best XL with 5s lipo in jammin ? Lower than XL/12 ?

Personally I would run a 9xl, but it depends on the speed you want. Is it fast enough now for you? A 9xl on 5s lipo with the appropriate gearing will easily do 40mph. A 10xl may run slightly cooler, but not as fast. I geanerally try to keep the motor rpm at around 35k. That seems to be the best place for the xl motors, much less and the gearing puts too much stress on the motor trying to get to 40mph, and much more and the motor produces too much heat. Feigaos are very picky about gearing and voltage, they have a small window to work properly. I like to have my vehicles to run at 40mph, and max motor speed of 35k rpm lets me do that with reasonable gearing.

Have you used this yet:http://scriptasylum.com/rc_speed/_top_speed.html it will allow you to play with combos in oreder to find the best match of equipment.

Here is the calc readings with your first setup with the stock spur:

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 62
Pinion Tooth Count: 16
Total Voltage: 18.5
Motor KV: 1390
Tire Diameter (inches): 5.75
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0.0164
Spur/Pinion Ratio: 3.88 : 1
Total Ratio: 12.81731 : 1
Tire Circumference (inches): 18.06 inches (458.83 mm)
Total Motor Speed: 25715 RPM
Vehicle Speed: 34.32 mph (55.13 km/h)
Effective Speed Rate: 1.86 mph/V (2.98 kmh/V)
Estimated Adjusted Speed: 33 mph (53 km/h) - 4% loss
Effective KV Value: 1390

35mph is pretty good, especially for racing.

Here is the setup with the kyosh spur and 12t pinion

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 46
Pinion Tooth Count: 12
Total Voltage: 18.5
Motor KV: 1390
Tire Diameter (inches): 5.75
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0.0164
Spur/Pinion Ratio: 3.83 : 1
Total Ratio: 12.67949 : 1
Tire Circumference (inches): 18.06 inches (458.83 mm)
Total Motor Speed: 25715 RPM
Vehicle Speed: 34.69 mph (55.73 km/h)
Effective Speed Rate: 1.88 mph/V (3.01 kmh/V)
Estimated Adjusted Speed: 33 mph (53 km/h) - 4% loss
Effective KV Value: 1390

Pretty much the same as the stock spur.

Now if you step up to a 9xl, you can gear lower, like an 11t pinion. This will give much better performance, as the motor rpm is higher, right at 35k max, and the mechanical load is less due to the lower gearing. Plus you will pick up 5mph or so.

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 46
Pinion Tooth Count: 11
Total Voltage: 18.5
Motor KV: 1853
Tire Diameter (inches): 5.75
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0.0092
Spur/Pinion Ratio: 4.18 : 1
Total Ratio: 13.83217 : 1
Tire Circumference (inches): 18.06 inches (458.83 mm)
Total Motor Speed: 34280.5 RPM
Vehicle Speed: 42.39 mph (68.1 km/h)
Effective Speed Rate: 2.29 mph/V (3.68 kmh/V)
Estimated Adjusted Speed: 40 mph (64 km/h) - 6% loss
Effective KV Value: 1853