27 replies to this topic

[Alchemist]

I would like to know what your thoughts are, in reference to wire gauge when setting up the motor lead wires please.  

 

Is it dependent on the motor being used? A 16D motor as opposed to the mini can motors, or even hotter motors like the Group 7 or custom winds? Or is 18 awg wire good enough for all motors.

 

Why is it that you no longer see (at least I haven't lately) double wire per terminal lead wire setups? Not as efficient as a heavier wire gauge perhaps?

 

Again, your thoughts are appreciated.

 

Thank you.

 

Ernie

[Big Booty]

Depends on how much voltage you want to drop along the leadwire before it gets to the motor.  

 

Lets assume you have a 4" leadwire from guide to motor. So total length of both wires is 8". Lets look at some different AWG. Lets pick 18, 24, and 28 AWG.  The resistance would be:

 

18AWG = 0.004 milliohms or 0.000004 ohms

24 AWG = 0.017 milliohms or 0.000017 ohms

28 AWG = 0.043 milliohms or 0.000043 ohms

 

Lets say your motor draws 10 amps under full load (maybe a S16D may draw that much but I doubt it??), since V = i x R we will drop a total voltage along the lead wire of:

 

18AWG = 0.00004 V

24 AWG = 0.00017 V

28 AWG = 0.00043 V

 

You're going to need a pretty sensitive multimeter (read bloody expensive multimeter) just to be able to measure that difference. If using a 12V track voltage I'm sure some people will tell you they can feel the difference between 11.99996 V (using 18AWG) and 11.99957 V (using 28 AWG) wire but I'm not one of them.

[Bill from NH]

Today, I wouldn't be wiring any motor hotter than a ceramic C-can with an X12 arm.

 

Generally, as long as the wire feels flexible enough, I wouldn't pay much attention to its gauge. I would say any quality 18 ga wire would cover all my needs. For some of the club/homeset motors, I might use the smaller 20 ga or even the Marklin train wire, whatever size it is. I don't drag race, but if I did, I might use a quality 16 ga wire.

 

I  ran double and triple sheaths of leadwire years ago. It takes more work to install it properly. I think they fell out of favor because you have two or three times as many joints to possibly break as you have with a single sheath of wire. Plus today's market has lots of competitors selling premium single sheath leadwire.

[Samiam]

Why is it that you no longer see (at least I haven't lately) double wire per terminal lead wire setups?  Not as efficient as a heavier wire gauge perhaps?

 

Because the A Main guys don't do it. Even if it doesn't make a 1/1000sec per lap difference, if the A Mainers do it, everybody would copy it. Or complain about it on Spacebook.   

[Michael Rigsby]

I've been using silicone R/C wire lately in my builds. Been using 20 gauge on FK and stock Hawk 6 motors in all classes, and 18 gauge on anything  bigger. 

 

Works well, very flexible, solders well, and haven't had any issues at all. Not to mention that it's available in bulk lengths much cheaper than packaged wire sold for slot cars.

 

Most FK and stock Hawk 6 motors won't peak out over 2.5 amps unless there is a major problem with the arm, and anything up to a S16D will be well within the operating range of the 18 gauge wire I use.

[Mbloes]

A bunch of cool electrical stuff.

 
I love posts where I need to use my brain.

[MSwiss]

Like the above posts mention...

 

Guide return and not breaking too quickly should be your criteria for lead wire.

 

You won't see an increase in car speed by using larger wire, or double or triple wire.

[Ramcatlarry]

Real old school used multiple wires to increase amperage to the rewind motors of the day. 

 

Not sure when the modern silicone insulated wire came into the wide use of today, but it really works with most motors we use. If anything, we can now downsize the gauge to save weight and keep it more flexible with many of the lighter amp draw motors and homeset motors. 

 

The PVC insulated wires are stiff and will break more frequently

[John C Martin]

I've been using the Ultra Lite lead wire from Kelly Racing for years.
 
Solder the wires onto guide , then I'll slide a piece of heat shrink 1/16" x 1/2" long down to the guide, notch it back about 1/8" to cover all the exposed wire, and super glue it down on the guide.Leaving as much insulation as you can to glue to the guide helps as well. Then I'll use a little heat from the iron tip to shrink the wrap on the wire after the glue has dried. Without the heat shrink, forget it... it'll break really fast..
 
Will work for any motor S16C or less for sure.
 
Saves about 3 grams and has great return flex. I can't detect any power loss, doubt there is any. But 3 grams is a worthwhile difference, at least on Retros.

[smichslot]

Essentially right.

 

I agree with the conclusions that seems to be reached here: no reason to use extremely thick leadwires.

 

However, I think that Big Booty is too liberal with the zeros.

 

*** an example: #18 is equal to 0.8 mm², which has a resistance of 0.021 ohm per meter., which is the same as 21 millimohms per meter. 8" is the same as 0.2 m, which means the resistance of the leadwire in Big Booty's car will be 0.2 x 21miiliohm = 4 milliohm, or 0.004 ohm.

 

Consequently a load of 10A will cause a voltage drop of 0.04V, or 40 millivolt, which is 1,000 times more that he found.

 

But I agree that its a voltage drop that is relatively insignificant. It's less than one foot of choke.

 

Steen

[Big Booty]

Sorry fat fingers on the calculator buttons.  Yes you are correct Im out by a factor of 1000.

 

18awg = 0.04V drop at 10 amp draw.

[Eddie Fleming]

Not a question of wire gauge, but what are the groups thoughts on the very stiff lead wire that makes the guide very hard to turn?

[Big Booty]

I arrange the leads so that there is a self centering action but I wouldnt describe it as stiff.  Stiff is bad.  The guide is wanting to turn and if you prevent this from happening something has to give.

[John C Martin]

Eddie I tried some also didn't like it . The drift in the outside lanes was good but the tighter lanes it won't work. I believe they can be to limber as well as to stiff. A quick perfectly centered guide is what you want..Rather have the guide opening in the chassis itself opened a little more for forward and back movement and slight side to side ..in my head it absorbs some shock of the slide in the side of the slot and joints.

[Eddie Fleming]

I understand John and my thoughts are much like yours, but I have seen it used with some success. I just don't like the idea and was wondering what others thought of it.

[Wayne Thomas]

I am using selver wirer for leads on my cars

[Gator Bob]

To the original question:

 

22 AWG.

[tonyp]

I played around with the stiff wire. It seemed better on a couple of chassis but not on others. I thought it made an improvement on some chassis but only on a king track.

[Gator Bob]

When you guys speak of 'stiff wire' are you referring to the red/wht wire from Ralph Thorne?

 

Tony, IIRC you were also using RTR wire on your 'Championship' Stock Car.

[Eddie Fleming]

Yes Bob, the red and white stuff.

 

I don't know who sells it other than Ralph.

[tonyp]

On the holly hill oval cars run better with a tight guide. Cars come over corners tighter. On that track you don't even need the guide to turn.

[Matt Sheldon]

I played around with the stiff wire. It seemed better on a couple of chassis but not on others. I thought it made an improvement on some chassis but only on a king track.

Steering dampner

[macman]

TQ works for me...

[John C Martin]

Same length wire PER SIDE. Top wire is TQ --1.5 grams. // Middle wire is RTR. --1.1 grams // Bottom wire is KELLY RACING -- 0.2 grams ...(w/ wire shrink )
So x 2. And I put that weight saving to better use..
Instructions See post 9

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[Gator Bob]

What gauge is the Kelly wire?