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-   -   KV and TURNS conversion (https://www.rctech.net/forum/electric-road/249663-kv-turns-conversion.html)

bluephi1914 10-25-2008 06:53 AM

KV and TURNS conversion
 
I am new to electric

and was wondering if there is a conversion chart for KV vs. turns



7700kv = ? turns
6900kv = ? turns
5700kv = ? turns
4600kv = ? turns

shadow102 10-25-2008 07:20 AM

Quote:

Originally Posted by bluephi1914 (Post 4976559)
I am new to electric

and was wondering if there is a conversion chart for KV vs. turns



7700kv = ? turns
6900kv = ? turns
5700kv = ? turns
4600kv = ? turns

If you go to the novak website they have a brushless motor chart which lists the kv of each of there motors. It will give you a rough estimate of number of turns

bluephi1914 10-25-2008 07:40 AM

Thanks .. checking them now

sosidge 10-25-2008 08:40 AM

Quote:

Originally Posted by bluephi1914 (Post 4976559)
I am new to electric

and was wondering if there is a conversion chart for KV vs. turns



7700kv = ? turns
6900kv = ? turns
5700kv = ? turns
4600kv = ? turns

Fundamentally there is NO conversion. It is two entirely independent ways of rating a motor.

Turns are strictly the construction. KV is an indicator of the no-load performance.

Rather like trying to compare two car engines, one based on capacity, the other on the maximum RPM.

Depending on the way a motor is wound, the magnets and other parts, its KV can be significantly different.

For regulated racing, the KV is meaningless - most most motors that are listed with KV only are not built to the ROAR specs anyway.

mac853 10-25-2008 09:40 AM

I think this question is not so "properly".

I could share with you about our case, since the beginning of season the rules is allowing 23T Br or 11.5R BL(with at most 4000kv) in the track, so everybody thought is fair then easy to follow.
But later organizer decided to put the rules as only 4000kv or below instead of 11.5R, just because in the market has some difficulty to find exactly 11.5R motors rather than 13.5R. The other main reason is from different makers, turn and KV don't match, for example: 9.5r of maker A could be equal KV as 13.5r of maker B; then the unfair situation is here.

snoopyrc 10-25-2008 09:50 AM

There are lots of things that contribute to the actual power of a motor. Its really best to look at the wind (like 13.5BL or 19t) as just one factor of the construction. Theres also the size of the rotor and the strength of the magnetic field. The size of the wire also comes into play. Like the actual guage of the wire itself.

It would be great if there was some standard of rating power. Like ?oz of torque and ? RPM at 7.4 volts. Then you could also add a 7.2volt rating and a 4.8volt rating.

Dragonfire 10-25-2008 08:39 PM

The Kv rating is meaningless to the racer. Motors need to be compared in turns as opposed to Kv. I have run mod motors from a few different manufacturers and all 4.5s go similar as do 3.5s. A speedpassion 3.5 has a Kv rating over 12000 while the LRP is under 10000. On the track they feel different but turn around the same results in lap times.

The tried and proven system of performance by turns is still the best way to go.

Drift Demon 10-27-2008 11:59 PM

i agree with mac853, it should be measured in kv. though, the 'turn' rating is great gearing wise, but i would also like to know what power the motor i buy is producing. i also believe the kv rating is a great indication as to what torque range the motor is in, more kv less torque, less kv more torque...

Here's a good example. mates got an xbr ex 8.5 (4500kv), & ive got mm vortex 7.5 (4250kv). geared nearly the same, i thought i would gear mine slighty higher considering mine is a lower turn motor. he just kills me everytime on the track, he's got it geared perfect. now, if i were to gear mine the same as his, i would have heating issues, & he'd still kill me because torque is very similar. not all same 'turn' motors are created equal...

mac853 10-28-2008 12:30 AM

My problem, is also other and is common for everyone:
-Why so much brands don't report the KV chart of their motors?

If they do that, we should have more choice then the organizers and ourselves feel more "safety" for none of us will be disclassified for problems of motor in the scrutineering.

sosidge 10-28-2008 04:43 AM

Quote:

Originally Posted by Drift Demon (Post 4985986)
i agree with mac853, it should be measured in kv. though, the 'turn' rating is great gearing wise, but i would also like to know what power the motor i buy is producing

KV is NOT a measure of power. Only a measure of RPM per volt.

Example - a 380 sized motor at 5000KV is going to make a lot less power than a 540 sized motor at 5000KV. And depending on the construction, two 540 motors rated at 5000KV may make significantly different power also.

Dragonfire 10-28-2008 05:48 AM

Quote:

Originally Posted by sosidge (Post 4986494)
KV is NOT a measure of power. Only a measure of RPM per volt.

Example - a 380 sized motor at 5000KV is going to make a lot less power than a 540 sized motor at 5000KV. And depending on the construction, two 540 motors rated at 5000KV may make significantly different power also.

Correct... As I said the number of turns is the way to go. With mod motors I have they all have to be geared differently to get the best out of em... as motors have always been this way I'm surprised ppl think one is better or worse because of it...

And as for power.. power is torque*rpm so a motor with lots of rpm could have great power if it has decent torque to go with it. On the other hand a very torquey motor could be better with signicantly less rpm. Which one is better? Well that all depends on what you prefer for feel and how you gear it. My exp with brushless is the extra torque they have over brushed motors slows you down a little in corners in tighter corners or low grip tracks. Thats why I run SP motors as they feel similar to brushed motors.

mok 10-28-2008 09:33 AM

Quote:

Originally Posted by Dragonfire (Post 4978060)
The Kv rating is meaningless to the racer. Motors need to be compared in turns as opposed to Kv. I have run mod motors from a few different manufacturers and all 4.5s go similar as do 3.5s. A speedpassion 3.5 has a Kv rating over 12000 while the LRP is under 10000. On the track they feel different but turn around the same results in lap times.

The tried and proven system of performance by turns is still the best way to go.

I'm not entirely sure about KV being meaningless.

An example...

I used to race an LRP 3.5T @ 9800 KV under the 5 cell rules. At 6.0V this puts the RPM of this motor at 58800rpm. Now I have switched to running lipo @ 7.4V this would give the same motor an RPM figure of 79560. With this motor I had a bit too much wheelspin and gearing the motor didnt necessarily help with this.

What I want now is a motor thats very close to what I was running, but I figure that at least 10% less RPM will help. So basically, I am looking for a motor that runs to around 50000-55000 RPM.

This is where KV ratings IMHO are useful. I could just say that getting an LRP 4.5T (being less turns) would be a better motor for me. In actual fact, the LRP 4.5T would be only 1000 rpm less (7.4x7800=57720). This tells me I am looking for a motor with less KV than the LRP 4.5T and my choices boil down to SP 5.5 @ 55500rpm, Novak 5.5 @ 54760 or the SP 6.5 @ 50320. In some instances I am looking at 2 turns on the motor to find an equivalent.

Point being, KV has a valid use in determining what motors are in a suitable range, especially when you're looking for something very specific such as in the example I have given above. I just wouldnt discount the KV figure as a useful spec of the motor. Although to be honest, I think that power, winds, KV, rpm @ x.x V, current draw and other stats are all important as each other.

-Mark

BIGTRUX 02-15-2010 01:28 PM

Isn't KV usually non sensor and turns sensored? I know that does not help but that is what I always thought..?

Profoxcg 10-18-2011 11:05 PM

^ I would like to know the answer please.

Jstall7543 10-28-2011 12:36 AM

Quote:

Originally Posted by BIGTRUX (Post 7009193)
Isn't KV usually non sensor and turns sensored? I know that does not help but that is what I always thought..?

The sensors have nothing to do with the kv rating, they let the esc know the position of the rotor. As far as Know.


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