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Old 12-03-2007, 08:51 PM   #1
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Default tires, rollout and motor question

i was racing last weekend on a asphalt ground. 2nd time racing.. i've noticed that some of the guys have really badly worn out foams (56-58mm dia) but yet come in 1st in every round. i was told that foam tires can be used all the way down to the wheels.. is that true?

if the diameter gets small, the rollout reduces as well, should i be changing the gear ratio to maintain the same rollout i want?

the reason why im asking this is because i've just bought a new komodo dragon 19t pro, it was fast when broken in brand new with brand new tires, but after cutting the comm and replacing with muchmore brush (cant remember which one but its non-serrated), the performance is much poorer when compared to brand new. is this due to, the brush? or worn out tires (58mm dia atm). i havent try out new tires yet as i dont have any in hand...
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Old 12-03-2007, 09:27 PM   #2
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"worn" tires have a thinner side wall, allowing for less sidewall flex and a better "feel". So the smaller the better!

yes, you would have to adjust gearing for roll out.

Did you cut the comm after you changed brushes?
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Old 12-03-2007, 09:59 PM   #3
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i cut the comms and changed brushes at the same time...
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Old 12-04-2007, 09:05 AM   #4
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Here's a link with almost all the motor set-up possibilities: http://rctouring.eu/electric_motor_set_up.htm

''By cutting your commutator the diameter will get smaller. This has a result of more timing. It's like every millimeter that the comm is cutten, is a degree more timing. Keep this in mind when you run 1 armature on a long race weekend with much runs. Your last runs, after cutting much of your commutator, will have more top speed and punch but will also less runtime! Calculate and experiment with giving less timing to prevent losing the race by a battery dumping failure''

The brush hardness could be also a factor, check the link.

Greetings Victor
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Old 12-04-2007, 09:20 AM   #5
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Quote:
Originally Posted by Victor A View Post
Here's a link with almost all the motor set-up possibilities: http://rctouring.eu/electric_motor_set_up.htm

''By cutting your commutator the diameter will get smaller. This has a result of more timing. It's like every millimeter that the comm is cutten, is a degree more timing. Keep this in mind when you run 1 armature on a long race weekend with much runs. Your last runs, after cutting much of your commutator, will have more top speed and punch but will also less runtime! Calculate and experiment with giving less timing to prevent losing the race by a battery dumping failure''

The brush hardness could be also a factor, check the link.

Greetings Victor
Thank you for the link! I like to use www.gearchart.com for my roll out! It's easy to use and allows you to print out a roll-out for you desired needs!
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Old 12-04-2007, 02:09 PM   #6
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Default motors

To get the most out of your motors when breaking in new brushes do this. Cut the comm to a nice finish, then break in the brushes at a low setting. 3 volts for 5 mins is good. Then to get the best performance out of your motor, take just a lite skim off the comm again. The motor should lite up.
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Old 12-05-2007, 06:44 PM   #7
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Awesome link Victor A!
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Old 12-05-2007, 09:42 PM   #8
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...something I use to do to keep track of my ratio (Before I used ROLLOUT)

If I had a known GOOD gear ratio for a certain motor...I always documented the starting tire size... Then as they wore, I'd calculate what percentage they had worn down...and gear UP that amount when possible.


61 mm to 58 mm for instance would be approx. a 5% size change.
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