3573 replies to this topic

[Phil Irvin]

GREAT.....
Most of the new stuff comes when looking "outside the box"..Ya never know what you will find when you look UP...NOT AT YOUR SHOES..

WAY TO THINK
PHIL I.

[Krash]

Honey,

I need to run to Home Depot and get some...um...um hinges to fix that night stand door for you

K.

[Champion 507]

John, am I one of the two?

That looks like great stuff. I need to replace the kitchen sink and disposer, so when I make a trip to Home Depot for parts I will surely look for (and probably buy) the stuff.


Doug Azary,
rewinder not currently active due to WAY TOO MANY things on my plate right now.

[havlicek]

Hi Guys,

With some of the pieces of the arm puzzle falling into place, an easy yet effective arm insulating coating has been a niggling detail. Epoxy works, but isn't exactly easy and from what I've seen you still have to round those sharp corners at the ends of the stack for more security. Other coatings work to a degree, but powder coating (or whatever that stuff is) with a good cure like the arms I got from Bill Bugenis is the best way. Still, that's not exactly easy or cheap...even the small "kits" available require pretty hefty cure and they cost a couple of hundred bucks. If this thread is about anything, it's about "kitchen table" technology that people can use to get good results. I think this goop fits in well with all that and look forward to others trying it and reporting what they find. On the temperature rating, even if the 2,000 degree thing is way optimistic, I think we'll be fine I'd send you all some of this stuff becauser there's enough in one container to do hundreds of arms...but the postage would be more than the $5 it cost to buy. I think I'm going to thin it some more next time as it's easy to "build" the stuff and should be even neater.

John, am I one of the two?

Absolutely Doug Actually, I think the whole club is here in the last few posts The only thing I would have liked better would have been if this stuff came in either white or another light color. The contrast helps make it easy to see if you're winding things neatly...but black works.

-john

[Phil Irvin]

It says it will stand 2000 DEG. heat and bond all to all.... With it thinned. Would it work as well as epoxy going in & bonding?

[havlicek]

Hi Phil,

If you mean "instead" of epoxy...I really really doubt it. Epoxy has some special characteristics/physical properties before and after curing that this stuff doesn't. I have no real evidence, but I'm not looking to replace epoxy anyway. One thing seems clear, this stuff is sold as "bonding metal to metal. On magnet wire, the coating is plastic of various types and this stuff probably doesn't bond nearly as well to plastic. Hey...you never know though until you try, but I'm happy with what epoxy does. This stuff seems like a very workable insulating coating though, and applying epoxy to the arm and coil after winding seems like it will only enhance the strength of it.

-john

[Alchemist]

Awesome find John!

You can even use this stuff as a temporary muffler repair. Here's the tech sheet for it: http://www.rutland.c...document_24.pdf

[chaparrAL]

DID I SEE IT THINS WITH SIMPLE WATER! Sight for sore eyes! We will see , I have the ovens to test this stuff, 1800 F if need be! Gotta get some and i will report back. Thanks John!

[havlicek]

Hi Ernie,

Thanks for linking to the tech sheet. Suggesting it can be used as a temporary muffler repair tells me not only that it bonds very well to metal...but that the bond is also probably pretty tolerant of vibration as well.

Hi Al,

Go for it As I had mentioned earlier, I will be thinning it out a bit more next time to try and get a more even but even thinner coating. It went on pretty thin on my first test, but the fact that it will start to air dry as you're working with it tells me that even if you slightly over-thin it, you can easily build a second coat as you're working. Of course, it you go way thin, the surface tension of the product may be so reduced that it starts to bead-up instead of cover. It takes very little additional water to noticeably thin the stuff, so go slow. Then again the stuff is so cheap, you can feel free to experiment and waste it.

-john

[Robert V.]

That cement looks like good stuff i may have to give that a try. I have question on rewinding my Mura arm i would like to have the timing neutral so if i put in a chassis running the other way in the future it will not over heat, on this Mura arm how do i know if the timing is neutral or at least close, do i line up the tabs center with the stacks or center it in between the stacks, wright now the copper tabs are not lined up with the stacks or centered between them.

[havlicek]

Hi Robert,

To get the timing "neutral", just visually set the com tabs exactly centered between the poles of the arm...not on the poles. The reason I say "centered" in quotes is because all arms will spin at least a teensey weensey bit better in one direction whether the timing is neutral or not. Even if you're off by a couple of degrees, it won't matter as to the longevity of the arm. The above goop (or something else taking it's place) is even more important on post Mabuchi arms with no stack insulators. The Mura arm you'll be working on has the benefit of having a good solid coating in there...but you can still have problems with shorts. On a coated arm like the Mura (and if you have some spare wire to experiment with), why not try winding the arm and testing it for shorts as you proceed from pole to pole to see if you even need to apply a coating. Also, don't get frustrated if the arm gives you trouble, I may be able to help with some more parts and then you can consider this arm as a practice arm...which is always a good thing. When I first started rewinding again, I thought to myself..."this was easy when I was a kid, it's going to be a piece of cake for me now". A couple of years later and I'm still working things out

-john

[Robert V.]

Thanks again for the info John, that's what i need to know to continue, i have already stripped the windings they came off pretty easy now i am working on opening up those little copper tabs and those are giving me more trouble than the windings but i will keep at it, you are wright about that Mura arm it has some kind of green coating which i will make shore to leave in place.

[Alchemist]

What's interesting is that it is "water-based" but yet the tech sheet reads:

"Limitations:
Not for exterior use. Do not add water. Does not expand or contract."

[Robert V.]

Well here is the rewound Mura arm it uses 60 turns of 30 gauge i cleaned the stacks and comm and then tested the motor up to 7 volts just to see what would happen it runs pretty smooth and should get better after i install new brushes and they break in, i still need to epoxy the arm then i will test it again to full power. I am amazed it runs as good as it does, that's the stripped Mura can in the back round.

[havlicek]

Two thumbs waaaaaaay up Robert! It's a little bit of a risk running them uncoated, but what the heck...you can wind as many as you like You've done a great job on this car and now it will be running with a motor that YOU wound. How cool is that!

-john

[Robert V.]

Thanks John, i agree it is cool that i will have a car running with the motor i wound, the track i race at i don't think any body will even try it maybe now they will.

[Krash]

Finished this one up tonight, S16D double wind with 35 turns of 30 AWG.

Epoxy, Static Balance, CommCut. It is very light on one pole, makes me wonder if I miscounted the number of turns?
Winds are not as tight as I would have liked.

I need to build it up and see how it runs.

Critiques welcome.



K

[havlicek]

Hi Kelley,

The wind looks aces, and a double to boot! Dang...things are really moving here of late, before you know it we might start a movement I see what you're talking about with the amount of balancing you had to do and it's probably not the winds because you'd have to be off by a whole lot. A resistance check (even with a not very accurate meter) would show that much of a difference. A wise man once told me that being off by a good amount is often the shaft and not the kind of imbalance we're thinking of (thanks Rick ). I'll tell you what though, the workmanship looks fab on that arm. You very well might toss a chunk of the stack with that much drilling because of the point angle of drill bits...been there more than once myself In any case, I'm stoked to see such cool winds from you and Robert!

-john

[Robert V.]

Great work Kelley. that arm looks outstanding.

[Krash]

John,

As I was finishing up the balancing tonight I was wondering what you use to drill the arm and how.

I used a "center drill" common item in metal working used for drilling a type of countersink hole and also a pilot hole. Center drills are more rigid than a normal drill bit and don't bend or wonder as easily. I just used the bottom point of the drill not getting to the tapered part. They come in different sizes from very small to large, I started with a #2 and endedup going to a #3 to remove enough material.



K

[Pablo]

Very nice looking, Krash.
What kind of balancer did you use ?
As John said, a couple of turns discrepancy would not make the balance that far off.
Epoxy looks great

[Champion 507]

Robert V. -
On your question of neutral timing: I've both seen and wound arms with what appeared to be 0º timing, yet they usually sounded faster or ran better in one direction. I don't have any scientific test equipment so I have to rely on the sense of touch, my eyes and my ear "tachometer". When testing your newly finished arm in your motor, look at the endbell and run your motor in one direction, then the other and notice which direction the brushes appear to arc less. That is usually the same direction the motor likes to run the best also. If it sounds the same in both directions, run it in the direction that has less brush arc.

Kelly -
It looks like you wound one of those Chinese arms from ProSlot and did a MIGHTY FINE job of it. I have seen and wound Chinese arms from Parma that were way off balance even after I stripped all the wire off and cleaned them up. It may be that the epoxy or whatever they coated the blank arm with was applied too heavily in one area causing the unbalance. I've rewound Parma S16D's and the last one I did looked like Swiss cheese after I balanced it because it was so bad on one pole. I even added 2 more turns of wire and extra epoxy to the other poles to try to make up the difference. It helped but I still had 3 deep 1/8" diameter holes in the stack to try to balance it out. Being an S16D, it had been balanced previously, but only 3 tiny drill marks in it...certainly not enough to throw it off that much. It obviously was not properly balanced from the factory. From all I could tell, the arm shaft was straight.

[havlicek]

Hi Kelley,

The method you see with the very shallow but wide cuts on factory arms is from some sort of an endmill. I don't own a milling machine or a drill press so I use 1/16" drill bits to make my first holes. If I need to take off more, then those 1/16" holes become pilot holes for larger bits. I use as little depth on the larger bits as I can to just keep countersinking the original holes but still producing enough of a pilot so the next larger bit won't walk on me. By doing this, I keep trying to produce a wider but still shallow hole. Different profile arms can tolerate more or less depth and width when drilling so I try and keep the shape of the stack in mind when I'm drilling. I'm familiar with the center drill you use but don't see an advantage over using different sized straight drill bits. It looks like it might actually be more difficult to avoid excessively weakening the stack.

When testing your newly finished arm in your motor, look at the endbell and run your motor in one direction, then the other and notice which direction the brushes appear to arc less. That is usually the same direction the motor likes to run the best also.

Hi Doug,

That sort of makes sense, but there are other things at play (I know you know all this...just digging in a little deeper for the sake of conversation) when you run a motor in that would cause arcing...brushes needing breaking-in, the way the brushes fit in their hoods or carriers (sloppy), the alignment of the hoods to the com (how square), even mismatched springs...as well as the condition of the com if it hasn't been recut. It seems that any or several of these factors could make a motor that is fairly "neutral-timed" seem to run better in one direction if not corrected. On the other hand, if the motor is very close to neutral timing and has been well set up with at least some break-in in one direction...then it should arc less in that direction! So this test on a new motor might actually indicate that more needs to be done...on a prepped and broken in motor, the outcome will sort of be predetermined.

Hi Pablo (another rewinder!),

He made a super-nice balancing block from a single piece of machined aluminum using drill rod bearing surfaces...slick! It's very much like a version of the Tradeship balancer Rick T has.

-john

[Robert V.]

Thanks for the info Doug, i agree even if you set the timing 0 it may still be off but i am not concerned i just want the motor to run good enough in either direction so it doesn't melt down.

[Bill from NH]

"I'm familiar with the center drill you use but don't see an advantage over using different sized straight drill bits. It looks like it might actually be more difficult to avoid excessively weakening the stack."

I first bought center drills to drill round stock for turning between centers on a lathe. The advantage of using one over an ordinary drill bit is that since the shank is a larger diameter, you'll have less bit deflection & breakage when using a drillpress or miller to make holes. If using a hand drill, this advantage might be negated somewhat, but I've never bent or broken a center bit in 40 yrs. I don't think stack weakening is an issue here.