3573 replies to this topic

[havlicek]

Rather than start a new thread every time I wind an arm, I figure it's better to keep it all in one place. Hopefully others will add to the thread too. To start, here's one I just did. I ordered some unfinished arm blanks from Mura, the stack is spaced so they can be either can or endbell drive:

-wind = 55 turns/#28 awg
-timing = +15 degrees adv
-Overall length = 1.099"
-Diameter = .517"
-Stack = .465"



-john

[JerseyJohn]

As Always, Sweet John.

[havlicek]

Thanks Joe! I did another #28 (a pair of endbell drives) for Joe Connolly. This one goes like this:

wind - 53 turns #28 awg
Overall length - 1.093"
Stack Diameter - .514"
Stack length - .467"
Current draw - 1.2amps @ 12V
Resistance - .4 ohm



-john

[Horsepower]

John, that is an absolute MASTERPIECE of motor architecture! Beautiful! I sure wish I had you as a friend in 1966. Most (or all) of mine either threw the windings , or when I learned to use epoxy, melted the comms......

[havlicek]

John, that is an absolute MASTERPIECE of motor architecture! Beautiful! I sure wish I had you as a friend in 1966. Most (or all) of mine either threw the windings , or when I learned to use epoxy, melted the comms......

Thanks also Gary...believe me, the arms I did back then didn't look or run as nice as these. My friends didn't care though, we were all happy just to "smoke 'em if you got 'em"...and we did smoke a few These #28's are pretty mild winds, they get spicy when you get down to 45 turns or so (.2 ohm or less) and push the timing. These should be a lot more forgiving though and after some break-in should be pretty easy to manage. I'd still like to get a hold of some class h epoxy or better in a clear/amber formula...but have pretty much given up on that.

-john

[Quickerthanyu]

This epoxy your using.. What is it rated up to temperature wise?

Thanks

[havlicek]

This epoxy your using.. What is it rated up to temperature wise?

Thanks

it's just regular OTC hardware store stuff, rated for 200° F. I try to optimize it by pretty careful over-curing (20+ minutes at 200 and then turn off the oven and let the arm stay in during the cool-down) and by using as little as possible, but it's definitely the weak link in all this. Even the magnet wire is rated at between 350-400° F ( 180-200°C ). Why...can you get me some of the high-temp stuff?

-john

[Horsepower]

John- I saw this when snooping around at industrial stuff. Maybe it would be good for the arms. They offer a free sample, and it says class H.
http://efipolymers.t...t...0&forward=1
This is the amber stuff available in pints, 600f! http://www.cotronics...tr/pdf/4460.pdf
One other thing I forgot to mention-I use J.B. Weld (not the quik weld) for armatures I've done and none has ever let go. They claim it will resist up to 500 degrees.

[havlicek]

Yep...I've seen that and many others as well. This particular material is black and requires a long elevated temperature cure...6 hours at 250 or 24 hours at room temp. They also list it as a moderate viscosity which wouldn't be as good at penetrating the coils as a low-vis material. I've done a lot of googling on this from time to time and have found suitable materials and even confirmed that they've been sold to the slotcar motor industry, but only in quantity...and no samples

-john

[havlicek]

I recently got a hold of some short Mura blanks that came with Kirkwood coms. Ron gave me some ideas about winds for these things as well as uses. I did one up today (a #25awg) and they make one heckuva high-pitched whine! I have no idea how fast the thing is spinning...but it's fast as...well really fast. I'm told that's the whole idea here...more RPMs but less torque. The arm blank itself is of seemingly really good quality...at least as good or better than the current stuff I've been using. Surprisingly, the thing doesn't seem to get particularly warm...at least running at low voltage for several minutes. The Kirkwood coms are visibly out of round when new and take quite a bit of careful effort to get them trued-up. They sure are beefy though. So here's "shorty #1" :



-john

[Quickerthanyu]

I was actually hoping you had some of that secret good stuff! lol

I'm still hoping to find something that will hold up to 800 degrees or more, but i just havent been able to find anything of the sort.

If you find something, definetlly let me know, I'd love to get my hands on some!

[havlicek]

I was actually hoping you had some of that secret good stuff! lol

I'm still hoping to find something that will hold up to 800 degrees or more, but i just havent been able to find anything of the sort.

If you find something, definetlly let me know, I'd love to get my hands on some!

Hi Josh,

800 degree or more epoxy is unecessary on the face of it. I know it makes for good advertising and all...but way before you get close to 800 degrees...a whole lot of other stuff will already have failed If you don't care too much about looks, you can use JB Weld for that lumpy-grey appearance . If I ever do get some high(er) temperature rated epoxy, I'll be sure to post the source here though. BTW...there are some polyester resins that meet that service spec (class h) as well, but again getting them in small quantities is the problem. Now if we can get together 100 folks we can get $1000 worth of "the good stuff"

-john

[Horsepower]

Hmmm,I thought Duralco™ 4460 low viscosity 600 degree would have been ideal in the trial pints.

[Quickerthanyu]

well... I'd use it for current G7 racing... Currently Koford boasts of its 800degree epoxy, and that stuff is extremely strong.. Which has given Koford the edge in G7 racing.

JB weld isnt strong enough for G7 arms, its not even strong enough for holding in Cobalt Mags....

[havlicek]

Hmmm,I thought Duralco™ 4460 low viscosity 600 degree would have been ideal in the trial pints.

I may wind up trying the Duralco, the only problem I see is that the cure time is long and with a low-vis epoxy that might mean baby-sitting the arm and flipping it until it gels enough to not run all over the place which would be difficult. Still...it seems to pretty much fit the bill otherwise.

well... I'd use it for current G7 racing... Currently Koford boasts of its 800degree epoxy, and that stuff is extremely strong.. Which has given Koford the edge in G7 racing.

The Koford material probably has other properties besides the heat rating that make it such a good choice (like the bond strength you mention). 800 degrees is probably way beyond the actual need as far as temperature goes. If a motor ever got that hot...or close...the body would probably melt just from being even fairly close to it. Even pure lead melts at just a little over 600 degrees F.

JB weld isnt strong enough for G7 arms, its not even strong enough for holding in Cobalt Mags....

It's really not the bond strength that's probably a problem with JB Weld. For one is is a "no-sag" formula and that alone makes it a bad choice. On an electrical coil (such as a motor arm), there are plenty of places for the epoxy to get into if it's low-enough viscosity that absolute bond strength for most types would be fine. JB Weld not working on cobalt mags is probably more about it just not being compatible with the magnet material. There are some great epoxies (most) that will not bond well to aluminum also. That's only a guess but if JB Weld has failed in that application, I'd just use what everyone else is using.

-john

[havlicek]

I just got in some Duralco 4461 and have high hopes for the stuff (we'll see). I opted for the 4461 over the 4460 even though it's "only" rated for 500°F, because of the much more forgiving and realistic cure schedule. I don't really have the facility to leave an arm baking for 4 hours or so as the Mrs. likes to do things like...cook dinner Still, the 4461 should be just fine...I think. 500°F is nothing to sneeze at as long as all it's other properties fit the bill. Stay tuned.

-john

[Ron Hershman]

I just got in some Duralco 4461 and have high hopes for the stuff (we'll see). I opted for the 4461 over the 4460 even though it's "only" rated for 500°F, because of the much more forgiving and realistic cure schedule. I don't really have the facility to leave an arm baking for 4 hours or so as the Mrs. likes to do things like...cook dinner Still, the 4461 should be just fine...I think. 500°F is nothing to sneeze at as long as all it's other properties fit the bill. Stay tuned.

-john

Do not bake your arms in the over you eat out of.... that is very dangerous and I do not recommend it.

Go get yourself a 30 or 40 dollar "toaster" over for doing your arms in and bake them somewhere out side your house... like in the garage, shed or somewhere out of the house.

Epoxy during it's curing gives off toxic fumes and leaves behind lot of other stuff you don't want in your body/system.

I learned the hard way.

[Rick]

John. I did some testing a few years ago about racing open motors. They can be raced at 300 degrees for a very short period of time, anything over that is toast and that is an open 24-25 gauge arm, now bring the wire down to 29 gauge or smaller and that 300 degree operating temp is a MUCH much shorter run time.( if the arm can indeed stand it for more than a few seconds) ERGO: 600 degree glue should be more than adaquate.

[Ron Hershman]

Depends on the wire your using and the rating of the coating. ML wire class 220 is good for 428 F before it fails or so they claim. Armor poly is good for 392 F Thermaleze wire is only good for 311 F

Double "build" or double coated wire does not double the temp rating. It only double the amount of electrical insulation.

If you epoxy is rated at 500 F and your wire at 311F....... your will have a failure at 312 F as the epoxy does nothing for the coating on the armature.

The epoxy is used to keep the wires from moving.

Temp ratings on epoxy mean nothing..... it the tear, tensile strength you are looking for...the higher...the better. That's the problem in finding good epoxy for Group 7 arms.

800 f epoxy means nothing..... if your motor ever got to 800 F...there would be other major problems before the epoxy let go.

The biggest failure in armatures is the "work up" meaning the steps and processes in epoxing the arm and curing it correctly.

Lots of arm MFG's have great epoxy...they miss something in the work up process that leads to failures.

[Rick]

Double "build" or double coated wire does not double the temp rating. It only double the amount of electrical insulation.

I remember people from all over calling me in the 90's for some of those heavy insualtion Int. 15 arms Mura had.

[havlicek]

Go get yourself a 30 or 40 dollar "toaster" over for doing your arms in and bake them somewhere out side your house... like in the garage, shed or somewhere out of the house.

...already done Ron. I "Amazon'd" a cheapo Proctor Silex for like $35.

John. I did some testing a few years ago about racing open motors. They can be raced at 300 degrees for a very short period of time, anything over that is toast and that is an open 24-25 gauge arm, now bring the wire down to 29 gauge or smaller and that 300 degree operating temp is a MUCH much shorter run time.( if the arm can indeed stand it for more than a few seconds) ERGO: 600 degree glue should be more than adaquate.

10-4 Rick, I tried to make that point earlier myself and as Ron pointed out also...the insulation on the wire itself as well as a whole lotta other stuff will fail long before you get to even 500° F.

...as Ron so well said:

800 f epoxy means nothing..... if your motor ever got to 800 F...there would be other major problems before the epoxy let go.

The biggest failure in armatures is the "work up" meaning the steps and processes in epoxing the arm and curing it correctly.

-john

[havlicek]

Well this Duralco stuff looks to be "the bee's knees". It's significantly less viscous than your normal hardware store stuff and penetrates really well. You can actually see the part you started on run into the windings as you work on the rest of the arm. Also, instead of running down the arm on the outside as the other stuff tends to do, this stuff doesn't present any problems at all since it penetrates the windings and tends to stay put bceause of that as long as you don't put too much on. It's also exceptionally clear, has no odor and even though it requires a lengthy cure time to reach full strength does in fact gel fairly quickly with heat. That means in not too much time you can continue to work on the arm balancing it, final polishing and whatnot. The stuff is expensive, but even the "small trial kit" is enough to do probably several hundred arms...at least

-john

[Jerk]

I wish I had half the know-how of you guys !! Iwould love to learn how to make my own arms..

[havlicek]

I wish I had half the know-how of you guys !! Iwould love to learn how to make my own arms..

...me too. When I see the stuff that Rick, Jairus, Gascar/Dennis, Steve O'Keefe etc. does, I just shake my head in wonder. When I started fooling-around with this stuff I built some chassis (mostly steel from saw and scraper blades, but some aluminum/composite stuff too) and painted some bodies that are probably OK at best. Somehow I got re-interested in winding arms like I did when I was a kid...seemed a natural part of this whole "retro" thing. Even though a LOT of people wound their own arms in the old days, factory arms took the whole market and people didn't bother any more. To a certain extent, the factory stuff got so good that people couldn't produce competitive arms at home, but that's no different from chassis. Regular people don't have the tooling to make CNC and laser-cut parts out of exotic materials, but they can make great chassis that perform exceedingly well anyway. After all...1:1 racing involves rules and limitations that define classes and so do slot cars.

So I got involved in the arm thing and have gotten some support and some of the usual..." you can't do that because...blah blah blah". That only made me more determined than ever to do a good job. Even this one (very) small aspect of slot cars has turned into way more effort and expense than I had envisioned...but the arms are really getting there with relatively little equipment and more perseverence than know-how These are NOT the arms I wound as a kid, but the thrill is the same. "Know how" comes simply from "doing".

-john

[NJ Racer]

What about coating the stack prior to winding, any thoughts?