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Gearing and temp advice

Gearing and temp advice

Old 06-30-2014, 10:48 AM
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Hihave only been racing buggies since jan of this year and had problems when i started so i endedup in mod with a castle sct motor and esc which i've been getting better with but am trying to get a 2nd buggie going in 17.5 blinky to run 2 classes. Since i dont want to fry my new lrp motor and works team esc here's the question, I read where hartson won stock nats with 33-72 gearing with the same motor which is 5.67 fdr,lrp says to start at 6 fdr,i tried 5.85 (32-72) fdr and it got pretty hot after about 4 min. I then droped to 6.24 (30-72) and its pretty warm but not near as hot as it was. Did hartson use different timing than stock setting and which way would he have gone? I dont know about timing on the motor and waht it does as far as temps go. Thanks for any help!
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Old 06-30-2014, 01:46 PM
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Every motor is a little different, even if you're talking about the same brand/model of motor. It's always best to start at a conservative gearing and work your way up. Most motors come to life with a little bit of added timing on the can, but not all.

Adjusting the timing in the positive direction (so, 5 degrees more, 10 degrees more, etc.) allows the motor to reach higher top RPM at the sacrifice of torque, heat and battery power. So, all things being the same, a motor with 20 degrees of advanced timing will be able to achieve a higher RPM than one set to 0 degrees (or whatever stock is for the motor), but will run hotter and eat up more of your battery.

I would start at a conservative gearing and try to up the timing 5 degrees at a time and see how it temps. You want to stay below 150 degrees.

One thing you need to make sure is that your transmission is butter smooth and not biding. Bad bearings or binding can overheat a motor in a blink of an eye. You're comparing yourself to a nats winner who has setup and maintenance down to perfection, so make sure yours is as well before you go for his setup
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Old 06-30-2014, 02:28 PM
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Originally Posted by metalnut View Post
Every motor is a little different, even if you're talking about the same brand/model of motor. It's always best to start at a conservative gearing and work your way up. Most motors come to life with a little bit of added timing on the can, but not all.

Adjusting the timing in the positive direction (so, 5 degrees more, 10 degrees more, etc.) allows the motor to reach higher top RPM at the sacrifice of torque, heat and battery power. So, all things being the same, a motor with 20 degrees of advanced timing will be able to achieve a higher RPM than one set to 0 degrees (or whatever stock is for the motor), but will run hotter and eat up more of your battery.

I would start at a conservative gearing and try to up the timing 5 degrees at a time and see how it temps. You want to stay below 150 degrees.

One thing you need to make sure is that your transmission is butter smooth and not biding. Bad bearings or binding can overheat a motor in a blink of an eye. You're comparing yourself to a nats winner who has setup and maintenance down to perfection, so make sure yours is as well before you go for his setup
Car is in good shape B4.2ft Am used to running the mod car turned down a bit so the motor never gets very hot have noticed the esc getting warm if turned to 0 timing (its set stock with 10*) but for me runs nice for me at 5. But wanted to see what a sensored 17.5 motor was like but dont want to over do anything either if you know what i mean. Just tried it with a little boost and was suprised how fast it is but the motor is pretty warm again so i guess ill be turning that back down. thanks for the input!
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Old 06-30-2014, 03:11 PM
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At stock nats (I ran same race at same track) it is all blinky, so first make sure your ESC is on blinky mode (not boosted), and you should be able to start with 20 degrees or so of timing on the can assuming your trans is smooth and not binding. Your gearing looks good to start where you are now. Per the manual, it says start at 32/75 which is 6.09:1.

As stated earlier, more timing on the can means more heat. Also assume that Hartson had other mods (bearings, lightened drivetrain, etc) that reduced drag vs. what you have. This would have allowed him to run the gearing he did. Likely he ran about 20-30 degrees of timing on the motor as that is where i have seen him run on club racing nights.

Suggest you make sure your drivetrain is as smooth as possible, start at as close to 6:1 as MFG suggests, put the timing back to 10 degrees on the motor, and go from there.
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Old 06-30-2014, 07:02 PM
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Originally Posted by HBRob View Post
Also assume that Hartson had other mods (bearings, lightened drivetrain, etc) that reduced drag vs. what you have. This would have allowed him to run the gearing he did. Likely he ran about 20-30 degrees of timing on the motor as that is where i have seen him run on club racing nights..
with a 17.5 does a lighter drive train really mean that much? Especially as far as heat and performance of the motor go?
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Old 06-30-2014, 09:20 PM
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Sure does when running stock. Allows you usually to go up a tooth in the gear as well as allows for a smaller lighter battery. Of course you have to make other adjustments to get it there as well. I now run a b5m with pucks, cut gears, bearings, etc, etc to reduce rotating mass and overall weight. Car is just below minimum and I have to add weight to get it to minimum.

But with that said, nothing replaces skill. I could have the lightest high tech car out there and could hand someone like hartson a 20 year old car running nicads, he would still probably beat me. That guy is just a machine.
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