Brushless Rota's
 

Does anyone have a definitive explanation of what effect different size rota's have on the pickup/top end in a brushless motor. I have some different sizes to try but need to know the effects of usin 12/13/13.5 mm etc. Mr Sleigh has explained this to me, along with Chris Yardy, but my memory is pretty vague.

Ta

Si

I'm sure they gave you a really intelligent and clever answer - but from what I can see it's just less torque since there is less leverage on the rotor because of the smaller diameter magnet - like using a shorter or longer spanner. I assume they rev a little higher too.
I only have the big sintered rotor for my nosram motors - and it's too powerful for lil old me.

Larger diameter (or more importantly, less air gap) = torque
Smaller Diameter (bigger air-gap) = RPM

smaller diam rotor = less bottom end and more rpm - very free running off-power, weaker brakes(but you have to gear it lower)

large diam rotor = more torque, less rpm + much more drag brake, killer brakes! (so you gear it higher)

if you changed rotor without changing gearing the change would be pretty massive, but the change in gearing normally makes the change less noticeable

I think the main thing is the amount of bottom end rip you get with a big rotor and the amount of brakes both drag and pull back brakes with a big rotor, some like it, some don't

Im lookin to get the best for 2wd. I know i ran the same as you at Oz Chris, but gotta get the balance right in the Speed Passion ones now!

I prefer small diam rotor in 2WD, I actually really liked the bonded rotors in 2WD, but its all sintered now so I choose the one with the weakest magnets (12.5mm)

worth remembering, with the larger diameter and the taller gearing, you will get things a tad hotter too, but in the end, the aim isn't to make the car quicker, but to change how the power comes in....

on the flip-side, the bigger the rotor the more efficient it is at producing the power so I don't think the heat will change much.

think of the rotor diam like the piston bore of an engine, bigger = more power

but maybe unlike an engine (im no engine expert) bigger = less rpm

Chris, the 12.3mm spec motor rotors are now legal too ;)

G

Don't you get more RPM just because they are lighter? :eh?:

G

it is swings and round-abouts, depends on your driving I guess.

Did LRP/Nosram always produce the differing rotors, or has this only recently been introduced?

tricky ran somthing diffrent at the end of 07 didnt he?!

I hope not:

26/03/2007 - date approved

Wrapped bonded magnet 14.0 supplied:-8.5T, 7.5T, 6.5T, 5.5T. Varnished sintered magnet in:- 4.5T & 3.5T approved.


27/08/2007 - date approved

4.0T approved.


27/04/2008 - date approved

Rotors:- Bonded 14.0. Sintered 12.3, 12.5, 13.0, 14.0.


So - unless he was using a sintered in a 4.5T or 3.5T he souldn't of have at a BRCA event.....

G

Si - it's a tough call for 2wd. For "on power" you want the 12mm (IMHO), as Chris said it gives smoothest bottom end. However (and this is a driving style thing), when you then back off, it will run on more into the corner - which is something that would give more of an issue for me, as i don't use much breaks. You can also adjust the timing, just to through another curve ball in!!

what do i know

More than you should maybe? ;););)

G

or maybe some one was on about somthing else
im just a dumb welshman who knows nothing:)

you know how to support a shit team :woot:

lets see what happens tonight