Mamba 5700 brushless gearing help

[HixX]

Hi all,
I've fitted a 5700 Mamba to my Worlds and are struggling to find the right gearing, has anyone any experience with this motor and the BJ4?

[BenG]

This is the equivelant of a 9 turn motor, so follow the gearing in the BJ4 manual for a 9turn

[jimmy]

I've not seen the Mamba nor have I any idea what the 5700 motor is compared to the LRP motors I have used. But from what I know the brushless systems rev more and dont like to be over geared. I'd suggest 15t pinion on the kit spur like I use with the LRP 3* and go from there.

[footey]

ive got a gtb 6.5 in with a 18 pinion on kit spure is that to big

[Rob Fitzgerald]

Just this minute been playing with one in my XXX CR try 2 of 3 pinions smaller than you would normally use with a 12 or 11 as a starting point.

[Richard Lowe]

I'm guessing the Mamba 5700 relates to 5700kV (which towards the slower end of brushless motors)? Jason suggests a 17t for a 2* Reedy/LRP motor which I believe are 6500kV rating, so I'd start on a 17 or 18t with the Mamba.

OT:- I've just noticed on the Novak site they have/are releasing a 3.5 (10500kV!) brushless motor

[jimmy]

Wonder if the current speed controllers will actually handle that motor ?

What KV is the 3* richard, any ideas ? I was told 13:00 ratio for that motor in 4wd, which is 15t. I thought it might be undergeared but but it was great.

[Chris Doughty]

Jimmy,

http://www.lrp-electronic.com/e/lis/

the 3-star is 7,700 KV, their 4-star is something like 8,600 Kv

[jimmy]

Ah right.. Richard is probably about right then with is gearing.

[Richard Lowe]

I'm not that sure actually Jimmy to be honest, I got the kV rating from the Tower website, but I've just spotted now that they have the 1, 2, 3 and 4*'s all rated at 6500kV in their descriptions

Novak give kV ratings on their motors, assuming the Reedy/Novak motors are similar speeds...

Novak Reedy kV
3.5 - N/A - 10500
4.5 - 4* - 9000
5.5 - 3* - 7400
6.5 - 2* - 6400

I have NO IDEA if those are correct, just an (un?!)educated guess.


:::edit::: Mr Doughty to the rescue

My guesses were'nt too far off

[jimmy]

Are the LIpo packs legal for racing yet ?
They seem to be a lot of money, but if you CAN charge then and run them / charge run / charge run... then I guess you'd only need a couple of packs maximum.

[HixX]

Thanks for the help guys. I tried a 16T today but from the sound the tranny was making I assume the motor was flat out. I will try a 17T tomorrow and measure the motor temps again. Apparently you gear brushless for top end only as torque isnt an issue providing you dont overcook the motor.

The only brushed motor I have owned was a 19 double, bought about 25 years ago . I had no idea how to gear rc cars then and I still dont now. Seeing as i want to start racing at some point, I guess its something I need to get my head round