34 replies to this topic

[havlicek]

... containing this little piece of jewelry, a silver commutator. It looks to be a very high quality thing and I plan on doing a G12 arm with it as long as welding it goes OK.  

 

Anyone want to remind me of the specs for that arm?

 

-john

[Zippity]

John,

 

Take a peek here

[havlicek]

Got it, Ron... thanks!

 

-john

[Dennis David]

That's a nice little chart!

[Samiam]

Nice gem. What is the raw OD?

[Marty N]

I recognize that part and the designer's work!! I'm pretty sure this guy could make pigs fly. (LOL)

[MSwiss]

Well, whoever designed it certainly saw a Koford S comm before. LOL.

John, FWIW that comm is a bit overkill for a wind as mild as a G12.

Of minor note, the slotting on one segment tapers in.

A bit odd since the slotting on the back side of the comm looks to be constant thickness and looking at it again the tapering is only on the metal, not the phenolic.

Anyway, be careful not to let any metal shavings get trapped in there when you cut the comm.

[havlicek]

Nice gem. What is the raw OD?

 

I don't know, Sam... I'll have to check it later and report back
 

John, FWIW, that comm is a bit overkill for a wind as mild as a G12.

 

Yeah, Mike... a little like squirrel hunting with a .50 cal, but I figured the nice thing to do was to offer to wind an arm with it and send it back. Because of the cost of the things, having been produced in such a small quantity (let alone out of silver), it's pretty great I was sent one... so I wanted to return the favor. He asked for a G12, so that's what I'll give him.
 

Of minor note, the slotting on one segment tapers in.

A bit odd since the slotting on the back side of the comm looks to be constant thickness and looking at it again the tapering is only on the metal, not the phenolic.

 
Yep, I noticed that as well... only when looking at the picture, my eyes (such as they are) didn't pick it up. It is a little odd since the slots seems perfectly square when looking at the bottom and it's easy to see which one is which because of the relationship to the keys/dovetails.

 

I always drag the back end of a #11 X-Acto blade through the slots after cutting the comm to remove built-up gunk in there.
 
-john

[Jairus]

Slot car porn.

 

(I love pictures of NOS stuff.)

[havlicek]

Me too, Jairus... but it's not "NOS", it's just "N"!

 

-john

[MSwiss]

John,

I didn't realize the G12 wind was a request.

That one slot is still perplexing. It doesn't seem logical/possible. LOL.

Maybe the owner will explain.

Yes, the backside of an #11 X-Acto has been the most typical tool to clear comm slots. Some guys argue using something metal can raise a burr. But I think that will quickly arc/wear away under power.

Occasionally, I would fashion something from mylar diaplane material to clean mine out, usually just before something like the Nats.

[havlicek]

I didn't realize the G12 wind was a request.

 
Yep, the sender really didn't expect anything in return, so I figured it was the least I could do.
 

That one slot is still perplexing. It doesn't seem logical/possible. LOL.

 
Yeah... I figure either the comm or the slitter moved at either the start or end (depending on how these things go) of the cut???
 

Yes, the backside of an #11 X-Acto has been the most typical tool to clear comm slots.

 
It can raise a burr if the slots are really thin or if the blade wiggles a little, but it hasn't seemed to be a problem. In this case, I figure it will not only clear the slots, but also make sure that one slot is at least the width of the blade at its narrow point. Honestly, I'm more worried about brazing the thing as I only have experience with copper.
 
-john

[Samiam]

John,

If you are worried about burrs just run a ballpoint pen down the slot.

[Coal Train]

Wow, that looks neat. The slots look a lot thinner than any standard comm out there.

Hypothetically speaking and just for shits and giggles imagine if the guy could get the winding wire sent to somewhere and get some pure silver wire in different gauges single coated insulated in poly thermelese which will be close to impossible or at least polymide insulated.

So many projects not enough lifetimes.

Well, at least we know there is one pure silver slot car comm in the world. I wonder what the difference in resistance will be compared to leading brands?

[MSwiss]

Sorry, but if silver was an advantage, the originator of that style comm, Stu Koford, would have done it years ago.

Even if cost was high, there would still be a market for it for qualifying.

[havlicek]

If you are worried about burrs just run a ballpoint pen down the slot.

 
 
Not me, Sam. Like I said, you can cause burrs, but I haven't had the problem or the old "ballpoint pen" method would have found its way into my subterranean lair.

As for performance advantages of silver, that's way above my pay-grade. One thing I can say is that it will make me even more careful than I normally would be!
 
-john
 
PS: Either way, it's certainly a lovely comm regardless of the material.   I'd be happy to lighten whoever's load by a hundred or so, even if "only" made of copper and they were burning a hole in their workbench.

[don.siegel]

Hi John, 
 
Interesting project, and yes, I'd be nervous about welding this one, too! 
 
It also reminded me that I had found a small bunch of Classic gold-plated comms, and I think I sent you one several years ago... does that ring a bell and did you ever do anything with it? Trouble is, it's just a standard Mabuchi comm, so not really made for anything high end, and the gold plating was probably about as thin as is humanly possible to do! 
 
Mike, I assume Stu would have tried gold too, if it had any real advantage... 
 
I assume that all the "silver" wire that Mura and other rewinders used at the time was silver plated and not pure silver...? 
 
Don

[havlicek]

Hi Don,  

 

It also reminded me that I had found a small bunch of Classic gold-plated comms, and I think I sent you one several years ago... does that ring a bell and did you ever do anything with it? Trouble is, it's just a standard Mabuchi comm, so not really made for anything high end, and the gold plating was probably about as thin as is humanly possible to do!

 
Gee... I can't for the life of me remember that, or what I may have done with it!
 

Mike, I assume Stu would have tried gold too, if it had any real advantage... 

 
Gold is actually not as good a conductor as silver and, being very soft wears easily. Gold's advantage over silver is that it doesn't oxidize/tarnish/rust, etc. That's why gold-plated electrical contacts are used. Silver, while being the best conductor does tarnish... I prefer my commutators to be made of platinum. 
 

I assume that all the "silver" wire that Mura and other rewinders used at the time was silver plated and not pure silver...?

 
I think it was only "silver colored". I think I saw where, for some really high-end applications, silver is used as a coating on some copper wire to reduce skin effect, but doubtful any of that stuff ever made it to a slot car armature. 
 
-john

[Pablo]

Thanks for the arm spec chart, Zippity. 

[Cheater]

FWIW Zippity's arm specs table has been listed in Slotblog's Links section under "Personal Slot Car Websites" for about four and a half years...

 

For future reference, here's a link to the entry:

 

Armature Wind Specifications

[havlicek]

Well... I got the deed done.  

 

The arm wound and most importantly welded with no drama at all. Actually, if I had to say what the difference was, I might think the silver was a little easier/more consistent to weld than copper... but that might be just because I was extra careful pulsing 55 amps through the thing.  

 

The arm is in the oven curing the epoxy and I'll just have to remove the powder-coat from the outside of the stack and cut the comm before sending it out for grinding and balancing. I'll shoot a couple of pre-balance beauty shots before sending it out.  

 

So far, so good!

 

-john

[SlotStox#53]

Sounds business as usual, John. 

Look forward to seeing your winding capped off with that cool comm. 

[havlicek]

Thanks, guys. 

Anywho, I got the arm cleaned up and the comm cut:

 

 

This is a 100% honest G12 arm.   The stack measured a bit over .350" before coating. I don't know how anyone would know if I took a lam off and then coated it, as it might still be just a smidge over the .350" spec, but I figure "honesty is the best policy".  

 

The wind is also exactly 50t/29 and I doubt anyone would know if it were a turn or two short. The finished arm measures .306 Ω and timing is approximately 22 degrees advance CCW.

 

Beats me how this compares to any other G12, but I suspect the arm will run just fine... it sure is a purdy thing anyway!

 

Oh... and it got one of my "reverse winds" to have everything end neatly back towards the comm.  

 

-john

[Zippity]

Beautiful.   

[Cheater]

John,

 

You are such an artist...