Shorten ESC Wires????????
 

Hi guys... Quick question...

for ages if needed ive cut or shortened the wires that come from the esc to the motor to make things more tidy within the car...

BUT...

was in my local model shop and we got onto talking about this and they said don't shorten them as it effects the motors performance???

IS THIS TRUE???

i dont understand this as i've studied electrical engineering and as far as i can figure out shorter wires = less resistance = more power going to the motor... i know that you'll never notice this small increase in power but i was then looking into how a brushless motor works and still i couldn't come to a conclusion on how shortening the wires effects the performance and again looking through the internet there are mixed results...

DOES ANYONE HAVE A DEFINITE CONCLUSION????

im no electrical engineer but i would say bollocks lol always cuts mattys to what ever lenght needed

I suppose if the wires were of differing lengths there would be a slight timing problem but not noticeable.

yea thats wat i was thinking if the wires were different lengths then yea that might throw things off a bit and the other thing i was thinking if the timing was effected by the wire length then again the difference would be minuscule and i cant see it even making a difference in motor performance because of the smallest difference...

It's difficult to see which Laws of Physics would fit that argument! Just in case there is, my logic for saying it doesn't matter is that the speedo sees the signals from the sensors in order to fire the coils and fires them. The coils react and that turns the rotor which the sensors then see and tell the speedo which then fires the coils....

Since it is a closed-loop system (providing you are running sensored, of course) it wouldn't matter how long the wires were, the sensor/speedo feedback loop will react to what is actually happening. If the wires are long and that reaction is slowed, the sensors won't see the rotor move and won't tell the speedo which won't fire the coils...

We probably need an expert to tell us definitively, but this sounds like a million other pub conversations - mostly not allowing the truth to get in the way of a good story! The killer argument for me is that, if it were the case that short wires were slower, none of the cars in the WC used by the top drivers would have short wires - and they all do!!!

You studied electrical engineering and you let someone in a model shop tell you that long wires is good?? wow!! :o

There's no way no how that I can think of that would say long wires are good. There is an argument that says all 3 should be the same length - however, I've always gone with the idea that I'd prefer it to look neat - so never worried about that one.

I think we deal with quite rugged electrical components in RC, even if we run wires of diffrent lengths we deal in mm not meters,It may make the very slightest diffrence, but don't think we would ever notice as the car goes round a track:lol:.
So yes the basic theory is prob correct,

As electric current moves at about 300000km per second (speed of light and even then it does not actually travel it pushes the electons in the wire along) a centimeter or so shorter would make no difference at all. if there was an esc that could detect that then we could not afford it.

Yea thats what has had me absolutely stumped the past few days...

For years i've always made things as neat as possible and that means cutting wires to suite and yea i know it sounds stupid me saying that i study electrical engineering and yet someone says something and i believe it... it really had me stumped as i couldn't figure out why it would effect it... and the other thing that put me off was looking though out the web and getting mixed results...

But all in all i think thats that question answered and finished... and ill be honest... I didn't even think about the sensor lead... DOH!!! rookie mistake!!!

This would of really saved time... hahaha

cheers guys!!!

Actually, electrons only move at about 10 ms-1 because as you push one electron into one end of a cable you get an almost instantaneus electron out of the other end. It's not the same electron but that doesn't matter.

There isn't just the slightest, tiniest possibility that the blokes in the model shop saw you coming and are even now laughing into their beers??!! You're not under 20 with a slightly youthful look while they are over 50 with tattoos and crew cuts... and a bit streetwise...

Just a thought... :D

To be really anal about it electrons move about 84mm a day.

Its actually impossible to say how fast they move as they don't occupy a well defined space, they have a probabilty of existing in a particular region of space but may actually be anywhere in the universe. Also, uncertainty principle states that if you do know their exact whereabouts you know very little about how fast they are going (and vice-versa).

But in the real, macroscopic world, a wire of a few mm more or less will have no noticeable effect. As said, there is an argument for keeping them the same length, but I can't see an argument for keeping them the same length as they came with out of the box.

when we get a new esc out of the box are the wires a calculated length? are they cut to the most optimal length? I suspect not,I think they just supply a length that will fit into most cars they think the esc will go into,

I can just see page 12 of an instruction book advising of the calculation required to work out the speed of your electrons in the universe at your reqired length of wire:D

So to make things clear. Including the speed of sound, if I stand on the rostrum closest to the speaker and shorten my motor wires will I get off the start line quicker? :lol:

CORRECT!!! :thumbsup:

this thread really should of been called 'what speed do electrons travel within my esc wires'

hahaha :woot:

I've run motor wires so short that you have to unsolder them in order to remove the motor lol.

never had a problem when I did that. I tent to leave them with a few inches now so the motor can easily be moved out of the way or adjusted for pinion size changes, etc.

In my opinion, every electrical (not electronical) consist mostly of just 5 possible components.

supplys: voltage source, current source
users: resistor (also wires), capacitor, spool.


Now every wire that is usually onsidered as a conductor is actually a resistor following Pouillet's law: the resistance of a conductor is directly proportional to its resistivity (a) and to its length (L) ; and is inversely proportional to this conductor section (S).
R = a x L/ S
R is the electrical resistance of the conductor in ohms
a is the matter resistivity in mm²/ m
L is the conductor length in m
S is the conductor section in mm²

Note: Depending on its diameter, the cable section is calculated as follow:
S=pi x d²/4
Depending on its radius, the cable section is calculated as follow:
S= pi x r²
Examples of a values in mm²/m at 20°C:
Copper 0.017
Silver 0.016
Alu 0.028
Iron 0.1

SO SHORT AND THICK WIRES GIVE THE LOWEST RESISTANCE!



When a current runs through a conductor, this conductor heats up. That’s what we call the joule effect.
This heat production is directly proportional to:
- The time during which the current goes through the conductor
- The square of the current intensity
- The resistance value

This is expressed by the following formula:
Q= R . I² . t Q in joules R in ohms I in amperes t in seconds

KNOWING THIS, IT'S BEST TO USE SHORT AND THICK WIRES BECAUSE THEY GIVE THE LOWEST RESISTANCE THUS LESS HEAT!

This in turn affects the resistance as explained by Mathiessen’s law, which can be expressed as follows:

Rt = R (1 + α t)

Rt is the resistance value at temperature t
R is the resistance value at 0°C
α is the conductor temperature coefficient
t is the temperature difference in centigrade degrees

Some α values:
- Copper, aluminium 0.004
- Tungsten 0.0065
- Silver 0.00377
- Bronze 0.0005

AND AGAIN THE SAME APPLYS


SO WHY MAKE THE EFFORT TO USE SHORT THICK WIRES?

WELL, IN THE END IT ALL COMES DOWN TO RESISTANCE!

TO PUT IT SIMPLE, IF A 100AMP CURRENT PASSES THROUGH A 0.01OHM WIRE U LOSE 1VOLT!

YOUR MOTOR IS THEN RUNNING ON JUST 7.4VOLTS.:cry:

I think you all missed the most important thing.

This guy lives in Ireland!!! LOL

I said "We probably need an expert to tell us definitively,...". Enter Sleenad. Job done. :thumbsup:

We are not worthy...

WOW!!! I AM TOTALLY BRAIN DEAD!!!

after that post i am totally shocked... i think we got our expert!!! and being honest i never considered the voltage drop when looking at wires!!! and serious a drop in 1V... wow...

and yea ill be honest... coming from NORTHERN ireland (sorry i just always like doing that) we tend to use the phrase 'that'll do rightly' basicly in proper english it translates to 'that will do...'

(at least thats the way i roll !!! :D )

I was actually expecting someone to crunch the numbers for the electrics in their car. CHILL guys!

Hey, I was going a little over the top with the numbers to make the point that it does matter which wires you use, just not for us mortals.

For those wanting to know some real numbers, let's say:

Copper wires: a=0.017
Length 20cm=0.2m
Diameter=3mm
Temperature=20°C

R=(0.017*0.2*4)/(pi*3²)=0.0005Ohm

Thus the voltage drop is actually 100A*0.0005Ohm=0.05V per wire.

For a 4000kV motor that's 4000*0.05*3= 600rpm

But still, for the top drivers, that is important. For us mortals and me as an amateur, I don't care.

So if you shorten the wires to half the size, the loss is cut in half also.

And don't forget, you probably loose most by using connectors.

All that said, I never cut the wires and use connectors, just because I like to switch and this way is the easiest (be it messiest) way for me.

But then again, it wouldn't matter anyway because my driving is, to say the least hilarious.:woot:

Why times 3? Because there are 3 wires? - thought only 2 were conducting at any time?

Wow!
 

I didn't know Oople could get so academic!

There was silly me thinking that shortening my wires would mean less struggle when trying to fit my sleek bodyshells...

:confused:

Whilst your maths is correct, you do assume that 100A is being drawn continuously which is not the case. You'll get this draw in very small pulses but if you were really drawing 100A all the time most speed controller fet pcbs would have melted way before 100A was flowing.

Bottom line is any voltage drop seen would occur for a small period of time.

Schrodingers cat?

I totally agree imull, but every time you gun the throtlle, you're drawing the amps, so in all you got more power to use coming out of the corner.

And as most corners have a few of those ...

But as stated before 99.999% of us won't notice the difference.

:thumbsup:

bazinga

What I dont understand is this.

If Atsang studied electronic engineering, why did he not know what sleenad said.
:confused:

I've got a degree in electronics and design stuff for a living and I had to go back to the text books to find references to the equations sleenad called up, as it's much more in the electrical domain. They really are separate subjects! :thumbsup:

This is a funny hobby! Short wires, low resistance gold connectors and 90c batteries for absolute maximum power then choose a 6.5 turn motor because a 5.5 turn is too powerful. Spend a fortune on lightweight carbon fiber parts and then add a load of lead weight to weight it back down. Ceramic bearings to reduce resistance and then add a bit of drag brake on the Esc for some rolling resistance on track.:)

with how much power is available to us now and the capacity of modern batteries etc, it all really doesnt matter that much anymore, back in the eighties running 1200sc's and 1400 scr's, every millimetre of wire and every ounce of weight mattered if you wanted to get to the end of the race without dumping. oh it is so nice not to have to clean your brushes between races anymore, i bet you dont see many people charging thier 7.2's by dumping them across a 12V car battery any more either!!

Yea these arent really the everyday equations that i work with from day to day... and being honest its the type of thing i would really look up either...

and again am only partly through my degree... so looks like i still have a lot to learn... :thumbsup:

Electrically speaking, its all about losses, more losses = heat build up = thermal cut out/damaged electrics.
And the more power you can deliver, the more heat you get.

And as for weight, that's all about choice. Many racing cars (1:1) can be made to drop in well below their classes lower weight limit. So they play with weight distribution/ballast (where its allowed) to improve handling.

So its not just this hobby, its anything that goes forwards under power.

They even spend millions making sure your 1.0L econobox commuter car has minimal losses/optimum heat rejection and good weight distribution. (well, in most cases.......)

This is A Level physics stuff. For homework I would like you all to read through this page and attempt the problems at the bottom

http://en.wikibooks.org/wiki/A-level...d_Conductivity

(Teaching physics is what I do!)

OK, are you implying that my car is crashed and racing at the same time?!!! I wish it was... :lol:

I guess that comes down to if you've taken your eye off the car for a second. In that second your car could exist in both states..........


Normally the sound of crunching carbon fibre tells me which state my car is in though.

:lol: Wise words

Big bang theory? (i missed the other replies :) )