R/C Tech Forums

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

Reply
 
Thread Tools Search this Thread
Old 02-10-2004, 11:55 AM   #1306
Tech Adept
 
Join Date: Nov 2003
Location: Mooresville, NC
Posts: 147
Trader Rating: 1 (100%+)
Default Motor Question

I use an LRP to run up my motors. I had a monster stock that ran at almost 8 amps at 2 volts. I took the motor apart, cut the comm, sprayed the arm, re lubed the bushings and put it back together with new brushes and it now only runs at about 4 and a half at 2. What could be causing such a fluctuation in the amps that the motor puts out at 2 volts?
bechs14 is offline   Reply With Quote
Old 02-10-2004, 04:03 PM   #1307
Tech Elite
 
sosidge's Avatar
 
Join Date: Dec 2001
Location: Bristol, UK
Posts: 3,865
Default

First off...

AMPS DRAWN AT NO LOAD MEAN NOTHING!

Second off...

A MOTOR THAT DRAWS MORE AMPS AT NO LOAD IS NOT FASTER - TRY PUTTING GLUE IN THE BEARINGS AND CHECK THE AMPS!

Your amp draw has gone down because the motor is running more efficiently. Less friction in the bushings, less arcing across the comm. Really not something to stress about.
sosidge is offline   Reply With Quote
Old 02-10-2004, 04:24 PM   #1308
Tech Adept
 
Join Date: Nov 2003
Location: Mooresville, NC
Posts: 147
Trader Rating: 1 (100%+)
Default

What about with a fan on. I'm not so sure about the glue but then again you are from overseas. They do some weird stuff over there. I'm not sure I agree with you though. I would have to say that a motor that runs at 10 amps at 2 volts seems to run a lot better than one that runs at 4 amps at 2 volts. Just a thought. Someone please explain without the sarcasim, as I am sure someone helped you when you were first starting out. You weren't an RC God overnight.
bechs14 is offline   Reply With Quote
Old 02-10-2004, 05:09 PM   #1309
Tech Addict
 
sands's Avatar
 
Join Date: Sep 2003
Location: Iowa
Posts: 620
Default

Quote:
Originally posted by sosidge
First off...

AMPS DRAWN AT NO LOAD MEAN NOTHING!

Second off...

A MOTOR THAT DRAWS MORE AMPS AT NO LOAD IS NOT FASTER - TRY PUTTING GLUE IN THE BEARINGS AND CHECK THE AMPS!

Your amp draw has gone down because the motor is running more efficiently. Less friction in the bushings, less arcing across the comm. Really not something to stress about.
You are talking too loud for me to hear you.

ALL CAPS MEANS YOU ARE SHOUTING!!!!
sands is offline   Reply With Quote
Old 02-10-2004, 05:37 PM   #1310
Tech Elite
 
sosidge's Avatar
 
Join Date: Dec 2001
Location: Bristol, UK
Posts: 3,865
Default

Quote:
Originally posted by bechs14
What about with a fan on. I'm not so sure about the glue but then again you are from overseas. They do some weird stuff over there. I'm not sure I agree with you though. I would have to say that a motor that runs at 10 amps at 2 volts seems to run a lot better than one that runs at 4 amps at 2 volts. Just a thought. Someone please explain without the sarcasim, as I am sure someone helped you when you were first starting out. You weren't an RC God overnight.
OK, sans sarcasm.

There is an impression that a motor that draw more amps under no load will be better on the track, and that tuning to get the most amps under no load is a "good" thing.

But consider what you're actually measuring here.

First of all, there's no load.

Consider the example of a Honda Civic and a Corvette at the stop lights (or traffic lights as us weird foreigners would call them).

Rev the cars up, and that Honda will scream away at 7,000rpm without hesitation, while the Corvette burbles at 5 or 6k.

Would you say the Civic is going to be faster? No, the true power comes into effect when you actually load up the engines by pushing the weight of the car, the Corvette will blow the Civic away (don't give me any of that "but if you had a Mugen head and pipe" rubbish).

Same with electric motors.

Revving them up under no load proves nothing.

Now I know amps drawn is more like fuel consumption than revs.

So lets look at it this way.

Lets assume an ideal world where the motor has no friction and no electrical losses.

Higher amps drawn by the motor at a certain voltage will mean higher power (P=IV, school physics).

But when you rev a motor at no load, it will go to it's maximum RPM for that voltage - but motors produce their maximum power at lower speeds (look at any dyno graph and you will see maximum power at about 2/3 revs).

So the amp reading you get is not the amps being drawn at maximum power.

And since motors are not ideal, friction and electrical losses can boost that amp draw, without actually improving performance.

Does that help?

PS I know what shouting is, the caps were deliberate, although I was not being fair to the poster and I apologise for that.
sosidge is offline   Reply With Quote
Old 02-10-2004, 07:59 PM   #1311
Tech Fanatic
 
hogdaddy77's Avatar
 
Join Date: Nov 2003
Location: Warner Robins, Ga
Posts: 846
Trader Rating: 1 (100%+)
Default

What is the best way to break in a new motor?
hogdaddy77 is offline   Reply With Quote
Old 02-10-2004, 08:11 PM   #1312
Tech Fanatic
 
hogdaddy77's Avatar
 
Join Date: Nov 2003
Location: Warner Robins, Ga
Posts: 846
Trader Rating: 1 (100%+)
Default

can a cobra stock com 2000k lathe cut a Monster Stock's comm?
hogdaddy77 is offline   Reply With Quote
Old 02-11-2004, 02:15 AM   #1313
Tech Elite
 
sosidge's Avatar
 
Join Date: Dec 2001
Location: Bristol, UK
Posts: 3,865
Default

I run motors on a 4-cell pack for a few minutes.

Is that a new or old lathe? Old "stock" lathes (as in 5 years or more old) are designed to cut sealed motors and won't do the job.

Now we have rebuildable stock motors like the Monster any "modified" lathe will do.
sosidge is offline   Reply With Quote
Old 02-11-2004, 09:03 AM   #1314
Tech Addict
 
DrOlds's Avatar
 
Join Date: Oct 2003
Location: Kansas City
Posts: 644
Trader Rating: 4 (100%+)
Default

Sosidge-Your take on amp draw makes perfect sense.Wouldn't it stand to reason that amp draw at no load is mostly a measure of parasitic loss? Wouldn't it make sense that the motor with less amp draw at no load would be faster?(provided the brush springs were stiff enough for the application)
DrOlds is offline   Reply With Quote
Old 02-11-2004, 11:06 AM   #1315
Tech Elite
 
sosidge's Avatar
 
Join Date: Dec 2001
Location: Bristol, UK
Posts: 3,865
Default

Quote:
Originally posted by DrOlds
Sosidge-Your take on amp draw makes perfect sense.Wouldn't it stand to reason that amp draw at no load is mostly a measure of parasitic loss? Wouldn't it make sense that the motor with less amp draw at no load would be faster?(provided the brush springs were stiff enough for the application)
I wouldn't say that less amp draw is the sign of a better motor either.

I could turn my example above upside down and you would get the same result - amp draw at no load means nothing.

Look at the motors fitted to a Mini T or Micro RS4. They draw very little amps - but they won't push a 1/10th tourer along very well.

I would advise anyone that a motor needs to be loaded for you to learn anything about it's performance.

You could use a dyno.

But the best dyno is the track.
sosidge is offline   Reply With Quote
Old 02-11-2004, 01:28 PM   #1316
Tech Adept
 
Join Date: Nov 2003
Location: Mooresville, NC
Posts: 147
Trader Rating: 1 (100%+)
Default

No offense taken. I just am new at this and sometimes it can be really frustrating when no one will give you a straight answer. It seems like everyone expects you to know everything from day one, when most people forget that they were in my place at one time. Someone helped them. All I ask is that someone explains to me like you did. Thank you and I appreciate that.
bechs14 is offline   Reply With Quote
Old 02-11-2004, 06:31 PM   #1317
Tech Regular
 
DT-Skyline's Avatar
 
Join Date: Jan 2004
Location: 24 Hour Fitness
Posts: 499
Send a message via AIM to DT-Skyline Send a message via Yahoo to DT-Skyline Send a message via Skype™ to DT-Skyline
Default

How about giving Trinities Monster Stock Pro a try?
DT-Skyline is offline   Reply With Quote
Old 02-12-2004, 09:38 PM   #1318
Tech Champion
 
Still Bill's Avatar
 
Join Date: Jan 2004
Location: Reno, NV
Posts: 7,237
Trader Rating: 12 (100%+)
Default

Quote:
Originally posted by DT-Skyline
How about giving Trinities Monster Stock Pro a try?
bechs14,

And then try the following laydown brushes and see what you like...
- Trinity 4499NT
- Reedy 767
- Reedy 766 (have not tried yet)
- Trinity 4504 cross cut (Oops! Thats for my Cameleon. I meant the 4505 for the Monster.)

Not sure which I like best my type of racing; but, I TQ'd and won my last two Sportsman Stock carpet races on the 767 and 4505 brushes, respectively, with stock springs on my Monster Pro. Otherwise, I cut the comm just before the brush serrations go bye bye (5-6 runs?).

Just starting with testing different springs too.
__________________
Constantly evolving CRC WGT and WGT-R/T...Carpet & Asphalt...All thanks to Team CRC.

And a pair of Associated B6 buggies for turf and clay tracks.

Last edited by JRX-S Bill; 02-12-2004 at 11:53 PM.
Still Bill is offline   Reply With Quote
Old 02-13-2004, 05:56 PM   #1319
Tech Addict
 
DrOlds's Avatar
 
Join Date: Oct 2003
Location: Kansas City
Posts: 644
Trader Rating: 4 (100%+)
Default Which motor for dirt oval?

I need help picking the right motor for my dirt oval truck.The track is pretty flat with a 120' drive line.I have been running P2K2 motors.I am wondering if I would be better off running Reedy MVP's.Green Machine 3's seem to be popular but I think something with a wider powerband would be better.Thanks in advance.
DrOlds is offline   Reply With Quote
Old 02-14-2004, 03:18 AM   #1320
Tech Champion
 
danjoy25's Avatar
R/C Tech Charter Subscriber
 
Join Date: Oct 2003
Posts: 5,149
Trader Rating: 37 (100%+)
Default Throttle response

Not sure if this is the correct thread but I run electric stock and just want to know if there is an advantage in throttle response if you use a high speed receiver (Futaba HRS). I know that steering is faster but I am more after the throttle advantages when compared to a normal receiver.
__________________
Awesomatix A800 & A800X/ Mugen MTX-5 / 3 Racing F113 / Kyosho RB5 / Kyosho Mini-Z
danjoy25 is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
19T Motor Forum Korey Harbke Electric On-Road 550 04-11-2009 08:27 AM
Stock motor sale !!!!CO27,P2k Pro, Monsters stock Marcos.J R/C Items: For Sale/Trade 36 06-27-2006 06:26 AM
Mod Motor forum Taz_S Electric On-Road 58 11-28-2003 12:58 AM
Stock Motor Forum JLMG1971 Electric On-Road 2 10-22-2002 03:07 AM
Stock Motor forum Taz_S Electric On-Road 62 09-14-2001 12:32 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 11:50 AM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net