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Old 08-16-2007, 01:55 PM   #1
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Default CO27 brush question and advice needed.

I rebrushed my CO27 for the previous club meet and replaced with Trinity
4503 "99 plus" brushes.
Motor ran well but lacked pace compared top other guys even dropping/increasing my gearing/roll out
I had the com cut and ran in another set of 4503 and was getting just on 7 amp draw on a motor checker and 7.6amps on teh ICE charger at 6v
I changed the brushes again and put some copper shunted silver laydown brushes from TOP Racing.
On teh ICE it keeps switching off as the amps go straight above 10amps
I put softer springs and still it pulls more than 10 amps.
This is also after i bedded in the brushes.

Is this good ???
any advice welcome.
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Old 08-16-2007, 02:36 PM   #2
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start off by measuring your amperage at 2v
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Old 08-16-2007, 02:46 PM   #3
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can u elaborate a bit more please
Should i take note of amp draw in 1 volt increments from 2v - 6v ?
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Old 08-16-2007, 02:58 PM   #4
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Most people, when comparing no-load amp draw, only compare the amp draw at 2 volts.
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Old 08-16-2007, 03:07 PM   #5
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OK and what would be looking for and why ?

My motor at 2v is drawing +-7.74amps after breaking in brushes with red springs .
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Old 08-16-2007, 03:44 PM   #6
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Quote:
Originally Posted by razzor View Post
OK and what would be looking for and why ?

My motor at 2v is drawing +-7.74amps after breaking in brushes with red springs .
It's not bad. If it is not binding on the bushings, it probably could use a little brush hood alignment. Also check to make sure the brush hoods are nice and clean (inside), as that is where most of the power is transferred to the brush. I use a rubber com stick to scrub them out between major overhauls.

I know that motor man for Team Kwik uses f-lines for brushes, however, I don't know what is actually available in your neck of the woods...
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Old 08-17-2007, 01:57 AM   #7
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Thanks for that but what would be considered to be a good amp draw at 2v ?
And why ?
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Old 08-17-2007, 07:30 AM   #8
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Razzor, I would say 7.5 amps at 2 volts is pretty good. The reason you want to see higher amp draw is because that is indicative of good brush to comm contact. Of course high amp draw can be caused by binding in the motor but if the motor is spinning freely then generlaly high amp draw is good up to a point. Too high and there is something wrong. If you are looking at 27T motors then red/green springs will give a little less amp draw than red/red but maybe only .2 to .4 amps. When I'm building motors I run them on a checker after break-in and usually see around 8 amps at 2.5 volts - sometimes close to 9 amps. Amp draw isn't everything but it is a good indicator of whether or not the motor is going to run OK or not.
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Old 08-17-2007, 07:55 AM   #9
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Thanks for that
all these small things can help us be better racers after all knowledge is power
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Old 08-17-2007, 09:30 AM   #10
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It's hard to tell motor performance until tested on the track. Good motors usually pull at least 6 amps and 6600 rpm or more at 2 V no load. However I've heard plenty of stories of "dog" motors on the dyno that were great on the track.

A good starting point for CO27 in touring car is purple pos/red neg springs and F brushes.

If you want a lot of knowledge, try

http://www.rctech.net/forum/showthre...motor+forum%22

This is a huge stock motor thread called "Stock Motor Forum" with a lot of information about stock motors. I would start at the end and read backwards.

Another slightly older forum is on rccars.com, the Big Jim's Motor threads

http://www.rccars.com/forums.php?act...um&forum_id=19

where you can spend hours learning about motors. Thankfully there's some good summary posts that get you 80% of the way there.
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Old 08-17-2007, 09:33 AM   #11
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I personally never put to much faith in amp pull on a motor test for I had some that have pulled high amps only to be dogs on the track. I have had it work the other way as well. I personally just build it, put it back in the car and just run it. It will either be good or it will be crap and you will know right away when it is in the car on the track.
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Old 08-17-2007, 04:08 PM   #12
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Thanks swopemike for the links.
Ive done a search but seemed to ave missed that thread ,good info there
The RCcars thread is ok although a bit old.

Lets see how the motors run tomorrow when i get some practice and play with gearing.
I bought another CO27 and a Fantom stock this afternoon.
The Fantom is Epic based like the CO27 but silver in colour.
On the dyno figures the two motors are very similar with the fantom having 1500 more RPM at 5v.
After running in brushes, bushes etc... the Fantom was getting 5.2amps and the CO27 4.9amps at 2v.
quite a bit down on my other CO27 at 7.7amps.
Will see what my experimenting does tomorrow.

Thanks again guys
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Old 08-17-2007, 05:52 PM   #13
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thats why no load testing means completely nothing. The only real place to test is on the track.

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Old 08-17-2007, 06:30 PM   #14
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Zap the magnets, The Co27 is only strong for about 4 runs. The magnets get weak.
And A pack of atomic powered batteries would help.
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Old 08-19-2007, 12:10 PM   #15
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Unfortunately. very few people have magnet zappers and the magnets will certainly last longer than 4 runs. It's not the number of runs that weaken magnets - it is heat. The magnets in all stock and 19T spec motors are pressed ceramic magnets which are generally considered to have max operating temp of about 250 F I believe. So don't run your motor hot and you magnets will be happy. Still, they all lose SOME strength from the normal heat of running the motor - more heat = more loss. Using a pull test a new zapped magnet will have a pull of around 350 gm and after several runs they seem to flatten out and stabilize at a pull of around 300 gm or so. This is just as measured on my uncalibrated gauge that I use for magnet testing.
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