Motor lengths and diameters.

[Shimmy]

Hey fellas...

I did a quick search, couldnt find the info I'm after.

I would like to know how much a difference does length and diameter make to brushless motors?

If I understand correctly, the torque comes from length?

How much difference would there be between, say a 4074 and a 4082?
Or for that matter a 3674 and a 4074?

I am going about my way to convert an MBX5T but not 100% sure on what motor to go for.

Ultimately I would like to go for the Castle 1717 at $70 but from what I can see and understand, there is no way it would fit and might be a bit too much power.

I am looking at going the leopard 4082 2.5Y 1250kv.
I am just bashing it at the moment, if that helps any.
I have decided to go for the HK 150a esc, not only because it is cheap but because I plan on waterproofing it (well, water resistance, it wont be submerged but will likely have the odd splash of water.
A Wye round motor would be better than a delta round motor for something as heavy as a truggy right?

Also, are there any tie down clamps or something for these long motors?
Something to hold the back end down solid so it doesnt move or bend or rip out the screws on a hard landing.

[nuz69]

The 4082 is a good motor for a truggy, use it with 6S lipo, should be plenty.
The delta/wye design doesn't change a lot of things, especially the kv, for the same turns number, a delta design provide more Kv. And Kv is directly linked to the torque per amp. (Kt.Kv = constant no matter the windings).

[suicideneil]

Length and diameter both make a difference, since a fatter rotor has as much of an effect as a longer one, so to does the number of magnetic poles the rotor has; hence why a 4 pole 43mm x 74mm motor is nearly twice as powerful as a 36mm 2 pole motor the same length. It's impossible to give exact figures because there are far too many variables.

Kv rating & voltage you intend to use will make a big difference too- for 4s lipo a ~1800-2200kv motor is great, for 6s lipo more like ~1400-1600kv is ideal. For your needs, something like the 40x82 leopard motor would be fine baring in mind kv rating & voltage choices..

[BrianG]

Slotted vs slotless design makes a difference too...

[brian015]

Originally Posted by Shimmy

Also, are there any tie down clamps or something for these long motors?
Something to hold the back end down solid so it doesnt move or bend or rip out the screws on a hard landing.

I use one of the HPI flux motor mounts to brace my 1527 (the motor is 4" long):

http://www.rcplanet.com/HPI_Motor_Mo.../hpi100903.htm

I bought mine on eBay.

[Shimmy]

Kinda forgot I made this thread, haha.

Anyways, thanks for the replies fellas.

I am planning on 6s, I did think of 4s for a while but figured 6s would be quite fun and should get longer run times.

At the moment, I think I am leaning towards the 1500kv motor, although I am still not 100% sure, I will be when I pay for it (possibly tomorrow or monday), only because then it will be too late to change my mind, haha.

One more question about the Wye vs Delta thing...
With a Wye wound motor, more timing is required to get it running right correct?
Could this chew into run time much?
I played around a little on my 3550 leopard wye wound motor, but dont really have something I could compare it to.
I noticed after putting the timing up it ran much better and cooler but it seemed the run time was a little shorter than usual (compared to a velineon 3500), I didn't actually time it though, and I was running it pretty hard.

As for the motor brace, that HPI one looks pretty good and study, probably the best option but I am not sure if they would fit on the MBX5T.
However I am thinking of the Losi 8E one or just run some high density foam underneath (shape it), havn't quite figured out how to stop it from going the other way though.

[nuz69]

A wye motor doesn't necessarily need high timing, only if it's used at high RPM and low load. 0 timing is fine for standard RPM range like 30-35K... Anyway the difference between 0 or 10° timing is pretty small.

[x-y]

for a truggy I think the 4074/4274/4082 are perfect ;)

[aqwut]

I always went by the efficiency of the motor compared to the weight of the motor (minus the weight of the heat sink)... The motor should be able to produce "X" amount of power in contrast to mass... but that's just me..