Outrunner question

[sikeston34m]

Originally Posted by lincpimp

Ok Sike, I have ordered the cooling fan for my redcat, I will do the same if I go with the dual outrunner hb ls.

Here is the math from briang's speed calc with the 4120/14 on 6s:

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 1
Pinion Tooth Count: 1
Total Voltage: 22.2
Motor KV: 660
Tire Diameter (inches): 4
Tire Ballooning (inches): 0
Total Ratio: 3.30769 : 1
Tire Circumference (inches): 12.57 inches (319.19mm)
Total Motor Speed: 14652 RPM
Vehicle Speed: 52.71 MPH (84.68km/h)


and with 10s:

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 1
Pinion Tooth Count: 1
Total Voltage: 37
Motor KV: 660
Tire Diameter (inches): 4
Tire Ballooning (inches): 0
Total Ratio: 3.30769 : 1
Tire Circumference (inches): 12.57 inches (319.19mm)
Total Motor Speed: 24420 RPM
Vehicle Speed: 87.86 MPH (141.13km/h)


Just wondering if you think the motors can hold up to 25k rpm? I am sure that the rest of the drivetrain can.

They "probably" can. If the ESC can keep up. The switching rate for 25,000 on an outrunner is like 100,000 rpm on an inrunner.

I believe they are balanced well enough, BUT I also believe that it comes down to a matter of keeping heat in check.

I wrote AXI another email asking about the best way to remove the stator from the bearing holder. Here's what they said:

"Dear James,

I must say that to remove the stator pack from bearing holder without damage is not easy but even mode difficult is to rewind the stator succesfully.

If you want to try to remove the stator pack than use heat. About 160 degrees of Celsius. At this temperature the glue can be released.

Usually this temperature dmage the grease in bearings so bearings need to be replaced.

In case you succesfully pull out the stator from bearings holder you can try to rewind. I really don't recommend this. Many people tried but no one succesfully."

Anyway, My point is, if you get it too hot, it's gonna come apart!

10S exceeds the ratings of the 4120/14. If you wanna "sneak" up on it, checking with a temp gun and taking baby steps, I'm sure you can find the point where heat really starts to be an issue.

I wouldn't just sock it on 10S and "see" though. You might be disappointed. If you are sure you want to run 10S, then I would choose a lower KV.

PS.......plan on changing that diff ratio to 4.3:1 Redo your figures with that and see what you come up with.

[sikeston34m]

Are you sure about that tire size?

[lincpimp]

Originally Posted by sikeston34m

Are you sure about that tire size?

Yeah, my onroad 1/8 tires are 4 inches tall.

[sikeston34m]

Oh ok, I'm sure that gearing will work then.

I was thinking the truggy tires would be 5.75"

Cool

[lincpimp]

I shall start gathering parts, and maybe make the motor mounts. Did you find dogbone cups that would fit a 6mm shaft? If so let me know, as that will be easier than try to drill them out!

[sikeston34m]

Originally Posted by lincpimp

I shall start gathering parts, and maybe make the motor mounts. Did you find dogbone cups that would fit a 6mm shaft? If so let me know, as that will be easier than try to drill them out!

All the E maxx and Revo stuff is 6mm.

[lincpimp]

Thanks, I think I have some left over cups from my emaxx builds!

[lincpimp]

Why the change to 4.3:1?

I know that you had to do it on the revo, but I am running a smaller tire than you, 4" versus 5.75" on your revo. My overall gearing to the road is lower than yours is on the revo. Or is there some other reason I am not thinking of (very likely!)