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Brushed VS Brushless VS kV - Ratings

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Old 06-23-2009, 12:35 PM
  #1
SacramentoJoe
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Default Brushed VS Brushless VS kV - Ratings

Is there any way to compare, say, a good brushed 19-turn, a good 13.5 BL, and agood 3000 kV rating motor(or any other sizes)?

I am looking for ballpark equivalencies. I can't always find specs on every motor.
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Old 06-23-2009, 01:18 PM
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Default RE: Brushed VS Brushless VS kV - Ratings

Brushless is much more free gearing, so not really. It depends on what you are comparing, top speed, max power, starting torque, efficiency, etc.

The current brushless equivelencies for racing are 27-turn brushed = 17.5 brushless, 19-turn = 13.5 brushless. These are rather conservative on the brushless end, a very well maintained, top-end brushed can beat out a brushless per the comparison above. But this requires meticulous maintainance, like new brushes every race series (3x 5 minute runs) and a comm cut every third race. Brushless generally does have to be geared higher to keep up.

With brushless, there can be huge differences in terms of max power (as much as +25%), starting torque (same), and efficiency between one motor and another, ie. the Hacker E40 and the Novak pre-ballistic motors. Typically this is a tradeoff and there is not one 'perfect' motor that excels at all given traits. Except maybe the really high-end motors like Neus which cost in the $200. plus range. Also, the profile the ESC is set to can have a tremendous effect on the peak power going full-throttle from a dead stop, since with brushless the ESC controls the variable timing advance.

This is similar in concept to the fixed timing advance set with brushed, by rotating the endbell, except that a good variable timing advance profile need not sacrifice efficiency at the lower RPM band.

http://www.rctech.net/forum/electric...less-dyno.html
http://www.rctech.net/forum/electric...al-thread.html

These two links above give dyno test results to verify (experimentally) some of the statements Imade above, like the comparisons of the hacker E40 13.5 and the Novak 13.5 where the Hacker has significantly more starting torque and slightly more max power, the novak has better efficiency.


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Old 06-23-2009, 02:32 PM
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Default RE: Brushed VS Brushless VS kV - Ratings

Brushed cant compare, you take that 50 dollar 19T turn and do a 10 minute main, on 2s, no stops no nothing, might as well throw that 19t turn out because its useless, That brushless is good to go again & again & again
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Old 06-23-2009, 06:01 PM
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Default RE: Brushed VS Brushless VS kV - Ratings

So would it be in the ballpark to say

27t = 17.5t = 2500kV
19t = 13.5t = 3500kV
17t = 9.5t = 4500kV
12t = 3.5t = 5500kV
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Old 06-23-2009, 06:39 PM
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Default RE: Brushed VS Brushless VS kV - Ratings


Quote:
ORIGINAL: SacramentoJoe

So would it be in the ballpark to say

27t = 17.5t = 2500kV
19t = 13.5t = 3500kV
17t = 9.5t = 4500kV
12t = 3.5t = 5500kV
What are you comparing?
max RPM? max power? starting torque? top speed?

For instance the first two are somewhat equivelent in terms of max power and top speed, but the RPMs you get out of a brushed 27t and out of a brushless 17.5 are totally different. The 17.5 has much lower RPMs (but at the same time much more torque in general), it has to be geared significantly higher to get the same top speed as the 27-turn. We're talking gearing as high as 35/67 or 35/72 on a TC4, or such.

But yeah, ROAR says they are equivelent, then again just a year ago ROAR was saying it was 27t = 13.5t (brushless) and 19t = 10.5t (brushless).
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Old 06-23-2009, 06:59 PM
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Default RE: Brushed VS Brushless VS kV - Ratings

Your right access, the 10.5 is considered a 19T brushed motor, 13.5 and 17.5 can be geared a little differently.
21.5 is considered a crawler brushless motor, and the fastest brushless motor I have is either the 6.5 10T in my B44,
or the tekin 362 9T powerhouse in my 501 quite possibly too much motor but I can handle the speed.
8.5 or 7.5 is fine for a 2wd buggy or truck,
8.5=15T
7.5=12T
6.5=10T
5.5=9T
4.5=7T
3.5=5T

Watts is another thing I tend to look at too because that's how fast the motor will drain your battery.
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Old 06-24-2009, 10:46 AM
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Default RE: Brushed VS Brushless VS kV - Ratings

Quote:
What are you comparing?
max RPM? max power? starting torque? top speed?
Access, Thanks for the information and the links. I learned quite a bit from them and still have a lot more to read. That forum IS very RC technical.

I am looking for a decent brushless setup for my son's buggy. He has my old Money 19 turn (with maybe 1 more cut left on it) and he is just getting control of it when running a 2S Lipo (on our dirt track). I would like to get something around a 17 turn equivilent. I have a CC 4600 kV (what turn would that be? 5.5? 7.5?) in my truck (which is great with 6-cell NiMH but a bit too much with a 2S) and my neighbor has one in his buggy (and it is too much for that car under most of the conditions that we drive). So I am looking/comparing at all the different options. As Redvan said, I am moving to brushless because of the maintenance aspects of brushed, not neccesarally for the fastest system out there.

We drive/race on a homemade track that is extremely dusty and slippery now. Even with my ESC punch control set down, it is easy to spin out. After reading the threads, I wonder if has more to do with the sensorless motor that the amount of power. I just want something that he will have fun with and not get frustrated because he keeps spinning out. 10.5 and 9.5 seem in the ballpark, but I don't know if I can afford sensored.
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Old 06-24-2009, 01:31 PM
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Default RE: Brushed VS Brushless VS kV - Ratings

Novak Havoc is a good choice, a few months ago this was one of the 'low price leaders' and a good all-around system too.

http://www3.towerhobbies.com/cgi-bin...avoc&search=Go

2s / 8.5 or 2s / 10.5

It drives very nicely and is a favorite for racers. Sensored gaurantees a clean start which is nice especially if your track does stadium starts or something similar.

To control it, you just have to start using 'throttle discipline'. With nitro or old-style electric (brushed, not the best batteries) the throttle was essentially setting 'jerk', or acceleration-prime (the derivative of acceleration over time). Now with new electric the throttle is just the raw power going to the motor. It is near instant, there is very little response time. You must drive it like the response time is nothing.

You are always going to have hyper-acceleration with brushless and lipo, so you have to learn to 'walk' the throttle. Even the weakest setups (ie. 17.5) will still get to full speed in under 1-2 seconds if you have perfect traction. With nitro or with brushed you could rely on the system and gearing to limit power, you can't do that with brushless and lipo. If you make a sudden movement or drive with the 'jerk throttle' style it will lose control. It's like the difference between football and ballet, if you were to use the technique and mindset of a defensive linesman to try to perform ballet, it will be an utter failure every time.
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Old 07-23-2009, 05:13 PM
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Default RE: Brushed VS Brushless VS kV - Ratings

This is what I know from my own personal tests.. 17.5 Brushless vary from 1560Kv-2200Kv 13.5 about 800 rpm variable . 10.5 1200 rpm..8.5 1000+ rpm.. Thnyou have the even numbers ..

Ok with Brushed motors they were all over 27t 22,000-35,000(stockstar)..

And with Brushless 1 motor run to the next..The RPM's vary +/- 300-700 Rpm per volt..

Brushed not that much 100 rpm..

Every 4-8 months motor company comeout with better motors..

So just sitting here reading the above posts I see the same Motors esc 5%..5% bad luck- 90% DRIVER

Anyway just having a Good LOL..Their's a Alert The just Released some New stuff for us all to Buy hurry..LOL...

This is what I have fun with..XXX-T MF2 all graphite..Metel gear trans 100%-indoor carpet racing- Quark 110Amp brushless all motor ESC- Tekin Redline 17.513.5-Neo 1-2-3-4..E40 17.5- 6.5..Reedy N40 (3t)..Pulsee 17.5- 10.5..Every Tekin #series bruhless 632-537-532-448-357-358.Original Reedy NEO green and black can By far the fastest motor and most torque
MRC academy SB V2pro sbv Buggies and my Vulcan /Photon conversion. Batts RCM 2cell 3300mah Kokam 4500 mah 2 cell (no names)servo BMS Bmg631-661 mgs servos..
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Old 02-18-2010, 12:57 AM
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Default RE: Brushed VS Brushless VS kV - Ratings

cool info.

Is there way to figure out what wattage a motor is so you can figure WHAt darn lipo t o buy ?

being told to get a 4600 or 13.5 brushless for shortcourse 2s lipo and dont know what size lipo to buy, like 20/30C or a 25/40c or 30/50 4200mah, 5000mah
I know how to calculate amperage + watts but clue less in how to figure a KV or wattage

Anybody know this stuff ?

thanks
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Old 02-18-2010, 08:56 AM
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Default RE: Brushed VS Brushless VS kV - Ratings

i dont agree with brushed comparing to BL- ran a 15T orion, had to gear down for a short, twisty track but had to keep some speed for 2 straights(16T pinion) motor consistently 155-160 deg. ran a 17T with same gearing and track, 135-145 deg. that tells me the 17T has more torque, and less energy wasted. went with a 3500kv BL system, geared up to 18T pinion, had enough torque to lift the front wheels, more speed on both straights, under 100 deg, consistent. with BL systems there are three magnet poles fully energized and with brushed there is one full and two partial. the place where this is really evident was on braking- when you hit the brakes the motor is shorted to itself, so the strength of your magnets and winding configuration are what will give you good braking. with the brushed motors, id have to throw out the anchor between half and three-quarters down the straight to make the suzuki hair pin turn(anybody remember pole position for the 7800?) but with the BL i could wait untill i was past the three quarters mark.

there is an equation for in-oz per amp, but it doesnt include any variables for rotor or can size, it just uses kv rating so im a little hesitant on its accuracy.
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Old 02-18-2010, 12:33 PM
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Default RE: Brushed VS Brushless VS kV - Ratings

Quote:
ORIGINAL: savagecommander


there is an equation for in-oz per amp, but it doesnt include any variables for rotor or can size, it just uses kv rating so im a little hesitant on its accuracy.

Here's what I use... at least as a good way to tell the different in torque and performance between different brushless motors, also with a grain of salt, considering their physical size etc.. But generally this seems to work for me:

1320 / kv = in-oz of tq per amp.

2 examples:

Castle CMS ~5700 kv motor, max current of ~100 amps (and we all know they work as stoves too)
Fiegao 9L (longer can) ~2700 kv motor, max rated current of ~65 amps (Using in my Slash and Emaxx...double duty )


1320/2700 = 0.488 * 65 = 31.8 in-oz of torque

1320/5700 = .232 * 100 = 23.2 i n-oz of tq

So as you can see.. on paper....doesn't matter which motor I choose, both can be regeared to use in either my Slash or Emaxx. But experience has taught me the 5700 just plain sucked, even in my Rustler it would heat up if I tried to run 3s OR geared up for speed on 2s.

The Feigao 9L on the other hand with 3S lipo I can gear up to 27/78 in my Slash and it will pull wheelies and keep going to top speed of almost 40 mph and barely reach 150'F with that kind of abuse. Also, geared stock in a 3096 Emaxx I can wheelie and reach ~ 30 mph on 3S and hit that same temperature range after a run.

Then again there's always the Feigao 7 XL motor... longer can, gobs of torque...~2380kv, ~92 amps max draw

1320/2380 kv = .555 in-oz * 92 amps = 51 in-oz of torque. As you can see at least by these #s, this would be most better suited for the Emaxx or heavier truck while the other two wouldn't really do well.

These #s may or may not be real accurate figures, but I use them as a guideline to compare most sensorless motors that I am not familiar with. This works regardless of brand or turns, because you are taking the raw kv rating and using a math constant to figure out the torque index, if you want to call it that.

Now with that said, Novak's sensorless motors don't seem to quiet make sense if you were to look at just the #s using the above technique.. Doing the same math on the 10,000 kv Ballistic 3.5R motor, at ~100 amps it should be making half the tq of the 5700 Castle motor, and Im not sure realistically how much current it CAN pull. All I know is my brother runs it in his Bandit gear up around stock settings 25/78, 2s 3700 mah 20C lipo and that thing will not stop wheelying. Oh and all the while barely reaching 120-140*F at worst.
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Old 02-18-2010, 02:10 PM
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Default RE: Brushed VS Brushless VS kV - Ratings

Quote:
ORIGINAL: Speed Assault
cool info.

Is there way to figure out what wattage a motor is so you can figure WHAt darn lipo t o buy ?

being told to get a 4600 or 13.5 brushless for shortcourse 2s lipo and dont know what size lipo to buy, like 20/30C or a 25/40c or 30/50 4200mah, 5000mah
I know how to calculate amperage + watts but clue less in how to figure a KV or wattage
No, you're thinking of the problem kinda backwards.
Look at the vehicle you are powering, what you're doing with it, and choose the battery based on that.
Ie. for most tenth scales, get a battery that can accept 100A discharge. Maybe for a tamer setup, you can back off to 70A.

For minis get a battery that can accept at least 24A and 36A preferably. For eight scale, 100A or more.

And don't think that just b'cos it goes slow means you don't need a strong battery. It's acceleration that pulls the most current. If you do hard acceleration, even if you stop accelerating at 30mph you'll still be pulling a lot of current up to 30mph. So you still need a reasonably strong battery.

The best motors are maybe 85%-90% efficient and the worst motors are maybe 65% efficient. So in terms of power consumption, there's not a huge amount of difference between the absolute best and the absolute worst setups out there.
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Old 02-18-2010, 03:15 PM
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Default RE: Brushed VS Brushless VS kV - Ratings

thats the same one i use-
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Old 02-18-2010, 11:52 PM
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Default RE: Brushed VS Brushless VS kV - Ratings

In this day and age of RC, why are brushed motors still around? Brushless is so much better. Cost is a moot point because brushless motors last way longer than brushed motors...and they don't require the constant upkeep that brushed motors require. lol
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Old 02-19-2010, 12:22 AM
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Default RE: Brushed VS Brushless VS kV - Ratings

Before ROAR the brushed motors were ones like the mabuchi 540. A 'silver can' brushed motor that required no maintainance and would last 50 runs or more. This was the motor used for most of the racing done at different tracks.

Then ROAR came along and redefined 'stock'. The new 'stock' motors had a good deal more power, at the cost of higher maintainance (brushes, comm cuts, etc.) ROAR also designed a new 'spec' and modified class, which pushed the limits of brushed motors even more. This changed the field of electric racing. Rather than the lower power setups of the old days, it was higher power setups that required significant maintainance and supplies to run. All effort that went into brushed systems was focused on power and performance, not reliability or no-maintainance motors.

And once brushless was introduced for ground RC, brushed development pretty much stopped altogether. The only reason it still exists today is cost. But brushed did not have to become such a pain, it was most that ROAR and the push for performance while keeping the same can size and other motor parameters to conform with ROAR rules that made it so high-maintainance as compared to brushless.
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Old 02-19-2010, 12:33 AM
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Default RE: Brushed VS Brushless VS kV - Ratings

for the old ROAR rules a stock motor had to be 27t,sealed can" no comm cutting or timing changes", X degree's of timing, and running on bushings, if the can was disturbed it was considered illegal, only brush's were allowed to be changed so then came the cut"timed" brush .. a 17.5 will smoke the best of the stock motors ... if your set up properly!
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