Speed Calculator

[BrianG]

LOL CHC. :)

Anyway, the site seems to be back up (for now)...

[captain harlock]

Man!

I just calculated the speed of the 1940/9 in a 4wd 1/8 buggy with 6s lipos and 21T pinion with 44T spur and the speed was a bit overrated. I mean, its too good to be true. 88mph is too much!

[BrianG]

It probably is too good to be true. Remember I didn't account for wind resistance or weight. Although, if you enter the motor resistance and approximate amperage draw, the kv will drop some giving you a more accurate reading.

[captain harlock]

So, it's hard to get such a speed in a 1/8 buggy, eh?

[Sylvester]

With 6s.. yes, with 8s, you might go over! :)

[captain harlock]

One of my friends was able to get his kyosho to the 80s, but he is a hardcore nitro guy. There is a possibility with six lipos, but maybe I need to go high in the number of teeth for the pinion.

[jhautz]

Well Brian I was finally able to put your calculator to the test. I entered my setup on my Emaxx and it came back with 47 mph. It sure seemed faster than that though.

Well I got a GPS off ebay for a steal a couple weeks ago and I just took the setup out and tested the for real.

I'm pleased to report that in real life it came to 47.9mph. Thats darn close. Kinda freaky. One side note though... The test was done running in a grass field. On pavement i'm sure i could have squeezed another few mph out of it.

Just a quick testimonial to the accuracy of this tool you made. Nice job!


BTW: Of all the nitros that were out there bashing today, only 1 was able to register a 40mph run, and it was only 41.3mph and that was some guy beating his chest obout his $400 motor. Most were only running around 31-35mph.

[BrianG]

Well, that's nice to know. :) Depending on the motor you are using, it could have been using loaded kv values, which may not be totally accurate if you are not loading the motor the same amount as done when they spec'd it. Or, maybe you had some tire balooning.

Ahhh, I love hearing those stories about the "slow" Nitros. They had their day, but with technology the way it is, electric will eventually take over for all but the hardcore Nitro guys who for some reason actually like the fumes (Bleh!).

[glassdoctor]

We are here to RULE THE WORLD!!! HA HA HA HA HAAAA........

[BrianG]

Hey, aren't you still using Nitro in your Losi 8 truggy? Hmmm? ;)

[jhautz]

Are you trying to justify the 0.9mph inaccuracy. :005: This was a compliment.. Not a criticism. Man you are a perfectioninst. :rolleyes:


My setup. Emaxx w/ stock diffs and 2nd gear tranny, 5.8" Zombie-maxx tires (duct taped to reduce balooning), Lehner 1940/7 motor, BK12020 ESC, 5s TrueRC lipo (I assumed 3.5V/cell under load). 51T/16T gearing.

Heres the data output from you calculator:

Differential Ratio:	2.8461538461538462
Transmission Ratio:	1.7222222222222223
Other Ratio:	1
Spur Tooth Count:	51
Pinion Tooth Count:	16
Total Voltage:	17.5
Motor KV:	2239
Tire Diameter (inches):	5.8
Tire Ballooning (inches):	0.25
Motor Current Draw:	0
Motor coil Ω:	0
Spur/Pinion Ratio:	3.19 : 1
Total Ratio:	15.6242 : 1
Tire Circumference (inches):	19.79 inches (502.72mm)
Total Motor Speed:	39182.5 RPM
Vehicle Speed:	47 MPH (75.5km/h)
Effective Speed Rate:	2.69mph/V (4.31kmh/V)

[BrianG]

Lol, yeah, I guess I am at times. :dft001: I didn't take it as criticism, just trying to explain the discrepancy. :)

[glassdoctor]

Let's pile on Brian hee hee

[BrianG]

It's OK, I have broad shoulders... But be careful though, now that I'm getting older, I may break something. :)

[ncalenda]

Originally Posted by jhautz

My setup. Emaxx w/ stock diffs and 2nd gear tranny, 5.8" Zombie-maxx tires (duct taped to reduce balooning), Lehner 1940/7 motor, BK12020 ESC, 5s TrueRC lipo (I assumed 3.5V/cell under load). 51T/16T gearing.

To stop the balooning, do you put the duct tape on the outside?