XRAY XB808 gearing
 

I picked up a used XB808 and I'm planning on using the Castle MMM and 2200kv motor out of an EREVO (because I have one). What gearing would you recommend for 4S?

Thanks.

http://www.scriptasylum.com/rc_speed/_top_speed.html

Play with the numbers in there, gear for 35-40mph

That's a great site. unfortunately I don't know how to calculate for ballooning of the tires. According to that 16T should get me 50mph, seems a bit high though. Might pick up a couple in the 12-16 range and check and see how my temps are. 12-14-16 should be fine right? or should I go 12-13-14... for more versatility?

Well the 12-14-16 will offer the greater range, and the 12-13-14 will offer greater resolution of adjustment. Maybe go with 13-14-15 to start. It's a good idea to make adjustments up or down by one tooth at a time and this is a compromise between both sets of pinions. Start at 40mph and see what kind of temps you get.

For ballooning I usually leave it at 0 or put a small number like .125 or .25

Once you go past 40-45mph the numbers in the calc start getting unrealistic because factors like drag, friction, wind resistance, etc. increase exponentially and start having a much greater effect on slowing the vehicle down.

P.S. love your avatar, when I was growing up we had two Dachshunds and they were the best little dogs I ever knew.

ok thanks a lot

Im running a 15T pinion on the 2200KV motor, works great no temp issues no problems!

Sounds good I can get Mod 1 pinions for $6 each so I'll get a spread of about 4 and see.

Thanks.

Give the RCM pinions a try. They are $10 but worth every penny IMO.

Very tru, that's what im using

I'm using Losi Mod 1 pinions. Picked up 11,12,13. Tried the 12 and after a couple of laps the motor temped at like 108-110.

Only problem I'm having is I'm using the wrong screws I guess to hold motor to motor plate and the motor moved away from the spur a couple of times.

AFAIK you´re supposed to use metric M3 screws, this means 3 milimeter diameter.

any special length? Someone at the track suggested using star washers to keep it from backing out. Problem is I have no idea where to find them.

*update* ok took her out to the track and ambient was probably 85-90 and I ran 10 mins and temped the motor. The can was about 130 and at the pinion was 150. This is with 12/42 gearing. Guess I've found my sweet spot for this track :)

ok so does anyone think I'm undergeared at 12/42 running 2200kv Castle motor on 4S? Was discussing this on another forum and was told "undergeared will take the motor out if its efficiency range, cause heat possibly, and diminish run time"

I have a 13 tooth pinion available to try in it. Guess I'll give it a shot and see what that does. Not entirely sure what speed to gear for. At the last big race the A Main Pro buggy winner averaged 19.5 mph over a 30 min main (nitro). This is the only track I've ever run on so I don't know if it's a "fast" track or not. With 12/42 my theoretical top speed is like 30 mph. Maybe it's undergeared?

Differential Ratio: 4.3
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 42
Pinion Tooth Count: 12
Total Voltage: 14.8
Motor KV: 2200
Tire Diameter (inches): 4.5
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0
Spur/Pinion Ratio: 3.5 : 1
Total Ratio: 15.05 : 1
Tire Circumference (inches): 14.14 inches (359.08 mm)
Rollout: 0.94:1
Total Motor Speed: 32560 RPM
Vehicle Speed: 28.96 mph (46.52 km/h)
Effective KV Value: 2200
KT constant: 0.61 oz-in/A
Motor Torque: Amperage not specified...
Final Torque: Amperage not specified...
Final Power: Amperage not specified...


Just looking for some insight.

Thanks.

Most will gear for mid 30's for top speed when racing. I find a 35mph gearing works well for smaller tracks and closer to 40 for larger tracks.

Ok I'll get some more pinions and gear it 15/42 that should get me 36ish and give that a try.