Armature Selection

[ryan540]

Should i be picking armatures with the least balancing holes and straightest windings?

[HurricaneLarry]

Absolutly not. I would grab the crappiest arm in the lot. Those are the ones that usually are the fastest. Just ask Doug"Bulldog" Bauer.

[Monty @ B.O.W.]

Actually, its quite difficult, impossible actually, to pick a fast armature by looking at it. However, there are still a few things you need to look at which may influence purchasing decisions.

1st) Timing - The timing is frequently different from that marked on the package! Practice by using a timing guage for a while, and soon you will be able to tell within a degree or two by eye. Check all three segments, as the timing can vary a bit from pole to pole due to less than perfect slotting of the comm. Reject an armature where one slot is definitively wider than the others. Also reject armatures that have epoxy filling the slots - they will slow down prematurely due to brush dust shorting.

2) Pretty windings don't mean much, but watch out for loose windings. These will, at best, shift easily making the balance less accurate. At worst, they can be tossed at high speed, end of armature.... Loose windings can hide under the tag, so look there too.

3) Tag - Many of you are now aware that ProSlot had a problem with tags a few months back. The bright white material they went to for cosmetic purposes wasn't all that compatible with the epoxy at higher temperatures, and the tags would turn up MIA. ProSlot will repair arms with missing tags at no cost to the racer. Meanwhile, on older tags, or on the new ones, there was and always will be the possibility of tags that just don't get tucked in well to the windings and are epoxied only along the edges. This is a possible failure point, of course, and it just gets worse on higher power.

4) Holes - After balancing thousands of armatures, I can say DEFINITIVELY that size doesn't matter (unlike in certain other matters), at least not to performance. It CAN matter to reliability, particularly on lightweight blanks like the ProSlot Millennium and Koford TriStar. Even then, its not so much the depth of the hole as whether it is well centered. Some theory here: The material removed to correct balance represents lost magnetic mass to the pole in question, and this should be a negative factor. On the other hand, less metal in the electromagnet decreases inductance, a positive factor. It is likely that the two cancel out. One other factor in favor of large holes is lighter weight, thats real, moving, subject to inertia weight! We drill gears and hubs, no? There's only one other factor I can think of, which is that bigger holes will allow more air to be moved around the armature. This is good for cooling, but costs a bit of power.

5) Comm wrappings - Like the wire, these can also be loose, so look out for it. Also, sometimes the factory slaves cut into the thread while re-slotting the comms (done to remove that excess epoxy mentioned in point #1).

Good luck, and have fun taking hours to scan the raceway's stock for minor defects...

[ryan540]

Tanks for your help. Do you know where i can get a timming gauge from?

[Zippity]

Gill A - that's where I got mine :)

[ryan540]

Sweet, might have to send him some mail...

[eap9]

Hello Monty.

Have you ever thought of writing "How To" books on slot cars? I am sure its going to be a hit!

[Bobhardt]

Monty,
I notice you talk about one slot being wider than others on some arms. I found this on a group 27 arm that I had slow down on me. This arm was always a good one until now. Now it just fills the slots with brush material. I've tried recutting it but just as I suspected, it didn't help. What causes one slot to get wider during the life of an arm? I'm sure this wasnt like this originally. One of the slots is much wider now. Could too much heat cause this? BTW, Your posts are always informative and interesting reading. Thanks......

[Rotorranch]

Bob....it sounds like the com on your arm may be "lifting" a segment. I'm assuming the com isn't "capped". I had a 27 arm toss a segment not long back when going for the track record on the 65 ft tri-oval at Speedway SlotCars. The car got loose and buzzed the motor pretty good, and ran about 1 1/2 more feet before it locked up! :(

It's my opinion that a lifted com segment is usually because of an over rev of the motor. The other possibility would be a poorly assembled com from the factory.

I know I won't run any more non capped coms in 27 or Open!

Rotor

[Bobhardt]

Rotor,
Thanks for the reply. What do you mean by "capped"? Are you talking about the black material at the end of the com?

[Rotorranch]

All of the capped coms that I've seen have a small, insulated aluminum collar around the end of the com next to the endbell. I think the "black material" you are refering to is the phenolic material of the com, and not a cap.

Rotor

[eap9]

Hello Rotor.

You are right about the capped armature being the way to go for grp27/7 racing. One thing I noted though is that if you true the arms, its best not to cut material from the aluminum cap as it gets weakened.

For Bobhart:

Most armatures that are capped comes from Camen. I am not aware if Koford or PK offer capped armatures.

[ET37]

All Pk arms are capped

[HurricaneLarry]

Not all PK arms are capped, wheat boy.


talk to you soon.

[weedracer]

I'm guessing that the arm with the differing slots is a Koford, right?

I've had quite a few that have had one slot like the Grand Canyon and another that a razor blade wouldn't fit into.:confused:

I haven't tried to make the narrow slots wider, but I do have to clean out the slots a few times during break in, as they get filled with brush dust and short out.

The arms run great thereafter though, so it's just another one of the concessions we need to make.

I just don't buy them anymore if they have one or more very narrow slots.

http://www.ezboard.com/intl/aenglish/images/emoticons/smokin.gif

P.S. Since when are there non-capped PK arms??

[Bobhardt]

Weed,
Thanks for the info. Yes it is a Koford, and 1 of the slots is wide as the grand canyon and the other 2 are very very narrow. I'll try cleaning it out a few times while breaking it in and then see how it acts. I was just going to throw it away. I was just curious as to what caused this because it wasn't like this until the last time I raced it.
Thanks for everyone's help......

[eap9]

Hello Weed.

Whats the most ideal way of cleaning the slots? And are you saying that arms with very narrow slots are no good?

[weedracer]

I didn't say that at all, in fact they run great sometimes.

I clean them out with the tip of an x-acto knife, follwed by a blow from a can of air.

What I meant is that its a hassle I could live without.... the slots should be equal....they always were.:confused:

http://www.ezboard.com/intl/aenglish/images/emoticons/smokin.gif

[Dan P]

Has anybody seen the article in the new SCB about cutting coms (making the diameter smaller) to increase timing? Seems like an awfully drastic measure to me, why not just buy a higher timed arm to begin with? Heck, I shed a tear with every pass of my com cutter, knowing I'm shaving a few laps off the arm (cheapskate that I am!)
But, are there real advantages to smaller diameter coms? Seems I remember reading something about this at Rudy Garriga's site, I'll have to go back and check...........

[Bobhardt]

Dan,
I read the article also but I think the they were intending for us to be aware that the timing does advance when we cut the com. Not just to cut the com to advance the timing. Gear ratios for the same arm might change after each time the arm is reconditioned. Thats the way I took it anyway.

[ryan540]

Anybody got a picture of a timming guage??

[Dan P]

That's not the way I took it.
It says right on the cover, "Use your com cutter for faster lap times", on page one it says "Who would have thought you could use your com cutter for performance, rather than just maintanance", and in the article itself, the writer says, (paraphrased) "Some people use arms right out of the bag and that's fine if it works for you but if not, try something else"............

It's a good article, don't get me wrong. I learned that timing changes with com diameter. BUT, as a hop-up tip? Not for me. I'd rather crank the endbell 'till it's perpendicular with the can!:p

[oldweirdherald]

Cut comms just to get advanced timing???

Even HG Wells wouldn't use his time machine as a shortcut to his own funeral!

(kinda profound... huh?) :rolleyes:


Crank up the Wayback Machine, Sherman! - Mr. Peabody's gonna stretch his arms! :D