bechs14

iTrader: (1)

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?

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.

bechs14

iTrader: (1)

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.

sands

You are talking too loud for me to hear you.

ALL CAPS MEANS YOU ARE SHOUTING!!!!

sosidge

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.

hogdaddy77

iTrader: (2)

What is the best way to break in a new motor?

hogdaddy77

iTrader: (2)

can a cobra stock com 2000k lathe cut a Monster Stock's comm?

sosidge

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.

DrOlds

iTrader: (4)

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)

sosidge

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.

bechs14

iTrader: (1)

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.

DT-Skyline

How about giving Trinities Monster Stock Pro a try?

Still Bill

iTrader: (16)

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.

DrOlds

iTrader: (4)

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.

danjoy25

iTrader: (38)

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.