R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Electric On-Road

Reply
 
Thread Tools Search this Thread
Old 05-25-2011, 04:46 PM   #1
Tech Rookie
 
Join Date: May 2011
Posts: 3
Default Help, motor overheating..

Hi,

I've just started doing electric cars, recently doing petrol but have stopped that now and concentrating 100% on electric. Now I've built up a car, got a 14t motor with a decent esc. And I'm running a 120t spur and 43t pinion. It goes great, very speedy, even going faster than my mates petrol rc car.. But the motor seems to overheat alot (the esc is fine and doesnt overheat), is there anything I can do to solve this problem?? Is my spur/pinion ratio right??

Thanks for any help,

Dave
wtrdave is offline   Reply With Quote
Old 05-25-2011, 06:09 PM   #2
Tech Champion
 
Join Date: Nov 2001
Location: Hawaii, USA
Posts: 7,186
Default

What car is it?
InspGadgt is online now   Reply With Quote
Old 05-25-2011, 10:14 PM   #3
Regional Moderator
 
CarbonJoe's Avatar
 
Join Date: Jul 2006
Posts: 2,661
Default

Without more details, we'd just be guessing.

First, what temperature is "overheating"? But, if you're convinced you're overheating the motor, you're most likely geared to high. Drop 5 teeth on the pinion and try again. If still too hot, drop some more teeth.
__________________
*** The Gate - Celebrating 8 years at the same location ***
The difference between genius and stupidity is that genius has its limits. - Albert Einstein
Understeer is when you hit the wall with the front of the car and oversteer is when you hit the wall with the rear of the car
CarbonJoe is offline   Reply With Quote
Old 05-26-2011, 04:59 AM   #4
Tech Rookie
 
Join Date: May 2011
Posts: 3
Default

Quote:
Originally Posted by InspGadgt View Post
What car is it?

Sorry, its on a Tamiya TA04

I dont really get the whole pinion/spur thing with the ratio n that...

All I have is 120T and 83T spurs, and 43T, 42T and 23T pinions, I'm assuming I need to buy some more??

Also I cant put my finger on the motor after a few seconds of touching it, I hear if you cant touch it for less then 5 seconds its over heating... This is on a brushed motor by the way.

Thanks,
Dave
wtrdave is offline   Reply With Quote
Old 05-26-2011, 09:41 AM   #5
Tech Elite
 
oeoeo327's Avatar
 
Join Date: Oct 2008
Posts: 3,630
Trader Rating: 74 (100%+)
Default

Given the limited amount of information we have, the recommendation of dropping a few teeth on the pinion gear would be the first course of action. Usually, too large of a pinion gear would be the first reason a motor overheats. Since your car has a 2.123 internal transmission ratio, and the gear ratio of your spur and pinion choice equals 2.79, your total gear ratio calculates to 5.92:1 (in other words, your pinion gear rotates 5.92 times for each time the tires make one full rotation).

You've also mentioned that you're using a 14 turn brushed motor; if we knew exactly which motor you have, we'd be able to help you make a more informed decision about gearing the car properly. However, 5.92 isn't too far off for a 14 turn motor in a 4WD touring chassis, provided that the motor doesn't have its endbell timing turned all the way up. If you've adjusted the timing, try a 40 tooth pinion and see if the motor runs cooler. If the motor still continues to overheat, drop a few more pinion teeth until you're comfortable with the motor temperature.
__________________
Founding member of the Solid Gold Racing Team - Mediocrity, redefined...
oeoeo327 is offline   Reply With Quote
Old 05-26-2011, 07:42 PM   #6
Suspended
 
Join Date: Feb 2011
Posts: 6,240
Trader Rating: 1 (100%+)
Default

5.92 fdr is more for 19t motors. A 14t motor should be geared closer to a 12t motor( 7.1 fdr) to start, and then geared higher if the motor stays too cold.
bertrandsv87 is offline   Reply With Quote
Old 05-26-2011, 07:56 PM   #7
Suspended
 
Join Date: Feb 2011
Posts: 6,240
Trader Rating: 1 (100%+)
Default

With 120t spur you will probably need 35t to 41t for some gearing flexibility... Good luck....
bertrandsv87 is offline   Reply With Quote
Old 05-27-2011, 04:06 AM   #8
Tech Rookie
 
Join Date: May 2011
Posts: 3
Default

Thanks for the help, as it all helps as I am very new to this.

Motor: LRP GT4 14x2

ESC: Nosram Magnum Power Reverse

Battery: 4300 mAh NiMh

I'd rather get the right ones as I dont have too much money to spend on pinions/spurs.

Thanks,
Dave
wtrdave is offline   Reply With Quote
Old 05-29-2011, 10:12 PM   #9
Tech Apprentice
 
RsageD's Avatar
 
Join Date: Apr 2011
Location: Malaysia
Posts: 51
Default

My motor overheats too.

TF5 RTR, 5.5t ezrun. Spur at 78, Pinion at 24. FDR is 8.125.

The auto cutoff stops my car after a 6 min run.

By the way, What about timing? i have no clue about this. Its now set on default but a fellow racer at the track said to lower it.

Thanks in advance!
RsageD is offline   Reply With Quote
Old 05-30-2011, 01:56 AM   #10
Tech Adept
 
Join Date: Aug 2010
Posts: 217
Default

What temperature do you consider to be overheating? It'll probably go to 120 before the enamel wire starts to give up. I know you say you can't touch it but even 60c is going to feel almost untouchable. If it smells like the magic smoke is trying to escape then keep putting smaller pinions on until satisfied. Other than that back the timing down.
YZFAndy is offline   Reply With Quote
Old 05-30-2011, 07:31 AM   #11
Tech Apprentice
 
Join Date: Sep 2009
Posts: 66
Default

Yeah, overheating is when the cables go off from the motor, and that's damn hot!!
Normally you start with a high total gear ratio, eg. 7.5
Then you lower the gear ratio by adding one or two teeth to the pinion
Skynet is offline   Reply With Quote
Old 05-30-2011, 07:59 AM   #12
Tech Apprentice
 
RsageD's Avatar
 
Join Date: Apr 2011
Location: Malaysia
Posts: 51
Default

Quote:
Originally Posted by Skynet View Post
Yeah, overheating is when the cables go off from the motor, and that's damn hot!!
Normally you start with a high total gear ratio, eg. 7.5
Then you lower the gear ratio by adding one or two teeth to the pinion
When u say lower as in more for pickup like my current FDR is 8.125. Right? Thanks Skynet
RsageD is offline   Reply With Quote
Old 05-30-2011, 08:01 AM   #13
Tech Apprentice
 
RsageD's Avatar
 
Join Date: Apr 2011
Location: Malaysia
Posts: 51
Default

Quote:
Originally Posted by YZFAndy View Post
What temperature do you consider to be overheating? It'll probably go to 120 before the enamel wire starts to give up. I know you say you can't touch it but even 60c is going to feel almost untouchable. If it smells like the magic smoke is trying to escape then keep putting smaller pinions on until satisfied. Other than that back the timing down.
What are the effects of dropping the timing besides that the motor will run cooler? Sorry, i dont understand the timing for brushless motor.

Are they like engines so they run smother and proper burning of fuel etc.?
RsageD is offline   Reply With Quote
Old 05-30-2011, 11:05 AM   #14
Tech Elite
 
Rick Hohwart's Avatar
 
Join Date: Sep 2003
Posts: 3,935
Default

Quote:
Originally Posted by wtrdave View Post
Sorry, its on a Tamiya TA04

I dont really get the whole pinion/spur thing with the ratio n that...

All I have is 120T and 83T spurs, and 43T, 42T and 23T pinions, I'm assuming I need to buy some more??

Also I cant put my finger on the motor after a few seconds of touching it, I hear if you cant touch it for less then 5 seconds its over heating... This is on a brushed motor by the way.

Thanks,
Dave
If you can touch the motor for a few seconds it is not overheated.
Rick Hohwart is offline   Reply With Quote
Old 05-30-2011, 11:18 AM   #15
Tech Adept
 
Join Date: Aug 2010
Posts: 217
Default

Quote:
Originally Posted by RsageD View Post
What are the effects of dropping the timing besides that the motor will run cooler? Sorry, i dont understand the timing for brushless motor.

Are they like engines so they run smother and proper burning of fuel etc.?
By reducing timing you will have a less rpms but should have more torque and overall efficiency is increased. Overall power is reduced but sometimes you can back timing down and not see any lose. I would start at minimum timing and work your way up. Generally by increasing timing you find a point where the motor wont make any more power but heat start to rise suddenly.
YZFAndy is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
Gear Ratio help nhodd Electric Off-Road 13 04-03-2009 04:59 PM



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 10:54 AM.


Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net