119 replies to this topic

[Jesse Gonzales]

It was said in the 60's that the black filled comms had asbestos in them, the "New and Improved" light brown ones that replaced them used fiberglas. I never scattered any of the black ones, they usually threw solder or hurled epoxy. The brown ones went off like popcorn in the bank at Speed & Sport quite often. I bought every black filled comm I could find back then for customer arms as I could stand blowing an arm but a guy that just put down ten bucks for a hand wound arm on a Thorp blank would get irked. Arms were pretty cheap back then, at least for a kid that worked all his HS years and drove an MGB he bought and paid for was concerned.

 

The solder Lenz and Mura sold in little coils was pretty much pure lead.

 

Jess Gonzales

[brucefl]

isnt the weak link the 311 f degree wire coating which will fail almost immediatly under any load,so it doesnt matter if everything is rated higher like the solder or other components,if your plan is a test in futility,or you dont believe the coatings rating to be reality 311f,maybe its a +_,of 33%,and will hold for as long as the components?

 

well there a formula for epoxy for example they will endure brief excesses,but usually very short in duration.

 

also more likely than not without powder coat you will create impercievable microabrasions and short,and without encapsulating epoxy ,centrfical force will cause the winds to migrate,thus loosening and abrading/shorting.

 

why not invest in the 10cents worth of jb weld epoxy and a dollar in cheap higher temp wire available on amazon.com and make both laminate coating with the epoxy then coat windings.

 

but i guess this isnt the point,the point be to test the true limits of these less expensive lower tolerance supplies you have,i assume.

[brucefl]

jim greenaway used silver solder,so he could replace the commutators.

[havlicek]

Thanks John,

 

I'll check the runout on the comm and if it's close I will give it a go with a light polish.

Have at it then!  BTW, it's not *necessarily about "runout" (*non-concentricity of the com bore to the com OD)...although it may be in some cases.  I was more referring to "roundness", and I've had some that were "OK" and some that were almost "polygonal".  Either would cause brush-bounce though.  I was sometimes surprised after applying a sharpie to the com at how "not round" some of these were, while how some weren't all that bad.  The sharpie would tell (after the first light cuts) what's going on in vivid detail!

[Geary Carrier]

Well...I wailed on this poor arm and it didn't expire, yet.

 

I put this arm in the can with no comm phenolic and no spacers which gave about 20 mils of slop. The endbell hardware was not aligned, the endbell was not screwed to the case, the brushes were a bit tight in their holders and the comm had about 2 mils of eccentricity.

 

Started off at 12V and did 20, 2" full power blips, each one pulling about 6 amps. The motor started to get a bit warm.

 

Went up to 15V and did 20, 2" full power blips, each one pulling about 10 amps. The motor started to get a lot warmer...

 

Once again, if someone wanted to rewind something they could try this, just for fun...

 

[Phil Smith]

Have at it then!  BTW, it's not *necessarily about "runout" (*non-concentricity of the com bore to the com OD)...although it may be in some cases.  I was more referring to "roundness", and I've had some that were "OK" and some that were almost "polygonal".  Either would cause brush-bounce though.  I was sometimes surprised after applying a sharpie to the com at how "not round" some of these were, while how some weren't all that bad.  The sharpie would tell (after the first light cuts) what's going on in vivid detail!

 

I was thinking about that the other day. It seems the important thing about a comm is that it's *round* and *true to the armature shaft*. It could be conical, convex, concave, grooved, whatever, as long as it's round and true. The brushes would eventually wear to fit the profile and all would be good.

[havlicek]

 

I was thinking about that the other day. It seems the important thing about a comm is that it's *round* and *true to the armature shaft*. It could be conical, convex, concave, grooved, whatever, as long as it's round and true. The brushes would eventually wear to fit the profile and all would be good.

 

Not really.  Before the brushes could seat to the com, there would/could be excessive arcing caused by the conditions you mentioned, which would be a  bad thing.  Even so, what I referred to specifically with the Kirkwood coms is not any of those particular conditions, but more of what I called an almost "polygonal" surface...some flat areas and some closer-to-round areas, which would be a situation that no amount of "brush-seating" would correct, and would also lead to arcing because of "brush bounce".  In any case, having concentric and round coms is widely accepted as VERY important for good reasons!  About the best non-trued coms I've ever seen were those that Mura sold just before they evaporated under the name "Diamond Trued Coms", but they were strange for other reasons.

[MSwiss]

Comm concentricity is obviously important, but a small taper is not the end of the World.

 

I remember a case , at Koford, where a top Texas racer, Phil Bamberg, sent us his reconditioning, complaining another, previous reconditioner, had tapered his comms.

 

I asked him how they had run, and he said "great".

 

It was more a case of it triggering his OCD, and him worrying it might of "cost him a cut", on the life of the comm.

 

It was visibly tapered, IIRC, about .003" smaller, at the comm wrap, vs. the other end.

[brucefl]

Well...I wailed on this poor arm and it didn't expire, yet.

 

I put this arm in the can with no comm phenolic and no spacers which gave about 20 mils of slop. The endbell hardware was not aligned, the endbell was not screwed to the case, the brushes were a bit tight in their holders and the comm had about 2 mils of eccentricity.

 

Started off at 12V and did 20, 2" full power blips, each one pulling about 6 amps. The motor started to get a bit warm.

 

Went up to 15V and did 20, 2" full power blips, each one pulling about 10 amps. The motor started to get a lot warmer...

 

Once again, if someone wanted to rewind something they could try this, just for fun...

 

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nice job,destined to be a wall hanger.

to work another,day.

 

too pretty to demolish by fully testing its limits

[havlicek]

 

 

Once again, if someone wanted to rewind something they could try this, just for fun...

 

I'd go further Geary.  If someone wanted to try winding or rewinding, not getting involved with brazing, powder coating, buying a com cutter (*although having a com cut later on is cheap) or even learning static balancing...or bothering to send an arm out for dynamic balancing can all be set aside.  Doing just the winding and then soldering the com tabs so the arm can be spun-up is the best way to go...at first.  When that first arm comes to life, it's a pretty neat thing, and can inspire the person to dig deeper.  There are plenty of arms out there (16D arms are a good place to start) that can be stripped, and eBay can get a person coms good enough to do all this.

[brucefl]

Geary your arms look earilly like the legends arms(Big Jim Greenaway),the style of winding and the epoxy,real smooth,i couldnt it apart froms Jims,did he teach you his tricks,or you teach him your tricks,which is it?

[Dave Crevie]

You can use silver-bearing solder rather than braze if you are a little skittish about the higher temp. Way better than 60/40.

[brucefl]

So we know the wire,armature and commutator you used,what solder did you finally use and what epoxy,if you are willing to share(the epoxy looks great,great penetration and flow with no bubbles,did you heat cure,and pre heat arm below the insulations threshold,did you use a vacuum ?

[Bill from NH]

Bruce, the solder is indicated in post #1. i don't believe epoxy has been mentioned.

[Dan Miller]

Bump up the temperature rating of the insulation on your wire if you intend to up grade your welding technique and solder/braze material.  Hit the joint hard and fast while heat sinking the body of the commutator. When you dwell on the connection with a normal soldering iron you may be damaging the phenolic filler in the commutator as well as melting back the insulation on the wire, which can lead to problems of their own, depending on the armature as wound.

 

Check out what John has shared regarding welding. He has it pretty much down pat now days.

 

............ and please, cut the commutator.

[Geary Carrier]

 

I'd go further Geary.  If someone wanted to try winding or rewinding, not getting involved with brazing, powder coating, buying a com cutter (*although having a com cut later on is cheap) or even learning static balancing...or bothering to send an arm out for dynamic balancing can all be set aside.  Doing just the winding and then soldering the com tabs so the arm can be spun-up is the best way to go...at first.  When that first arm comes to life, it's a pretty neat thing, and can inspire the person to dig deeper.  There are plenty of arms out there (16D arms are a good place to start) that can be stripped, and eBay can get a person coms good enough to do all this.

 

This exercise was in point of fact designed so someone could go further... . The arm wind was purposefully aimed at pushing the HMP solder and low temp solderable wire past it's limits, with 15 volts as the final nudge.

 

If someone wanted to wind an arm they could use this information and results to get started on a proverbial shoestring.

 

Is this method as good as brazing and 200C wire, definitely not, is it worth a try...?

[havlicek]

Yep, understood Geary, and I've done more than a few posts like this one with the same aim in mind.  I'd love to see more people dig-in.

[Geary Carrier]

Geary your arms look earilly like the legends arms(Big Jim Greenaway),the style of winding and the epoxy,real smooth,i couldnt it apart froms Jims,did he teach you his tricks,or you teach him your tricks,which is it?

 

Hi Bruce,

 

You got me on that one...

 

 

So we know the wire,armature and commutator you used,what solder did you finally use and what epoxy,if you are willing to share(the epoxy looks great,great penetration and flow with no bubbles,did you heat cure,and pre heat arm below the insulations threshold,did you use a vacuum ?

 

The epoxy is somewhat similar to this: http://epoxymarket.c...onnectors-epoxy

 

The arm was cured @ 140C in air.

[gotboostedvr6]

Cured for how many hours?

[Geary Carrier]

Cured for how many hours?

 

Hi Dave,

 

It was cured for 1 hour.

[Geary Carrier]

On the other hand, if you would like to braze something, you certainly can...

 

[brucefl]

whats this,another arm with powder coating and larger wire size but still soldering?

[Geary Carrier]

Brazed from another thread...

[brucefl]

thats not solder?

 

do you believe the way you encapsulated the windings with epoxy is superior to johns encapsulating,yours is like armatures in the day and is heavier,would that be stronger in keeping windings from migrating or are both techniques equal.

 

yours appears as though floating in epoxy,with johns arms epoxy is barely noticable.

 

but it seems the more modern arms are like johns,your thoughts?

[Geary Carrier]

that's not solder?

 

do you believe the way you encapsulated the windings with epoxy is superior to johns encapsulating,yours is like armatures in the day and is heavier,would that be stronger in keeping windings from migrating or are both techniques equal.

 

yours appears as though floating in epoxy,with johns arms epoxy is barely noticeable.

 

but it seems the more modern arms are like johns,your thoughts?

 

Bruce, the comm tabs are silver brazed.

 

This is the first time I've tried this arm and wire combo and the epoxy was applied a bit too heavy. Thermal, aerodynamic and structural comparisons are best left to deep minds...