3573 replies to this topic

[MrWeiler]

A lot of racers think that if a little bit is good, more must be better.

MANY times that was you....

[havlicek]

Barney,

I remember when you posted that picture last time and my reaction is still the same..."b-b-bad to the bone"! Anytime you wanna play with a big wire arm just for grins (23/24/25), just dial 1-800-havlicek and I'll do my best for you.

-john

[Prof. Fate]

Hi

Mike and Mike, too often we tell the same stories!

sheesh.

A local hillclimb is run by plastic car guys who allow no foam, no glue, are always stripping the surface...no traction.

So, I was running a "legal" plastic NSR that had too much power for the surface and would spinn the tires all the way down the straight.

Why do you do that!

Cause if is fun?

A couple weeks ago, one of the owners was looking at my recently restored 1/32 Dynamic anglwinder. Asked "what is is legal for?" Some people have no fun in their souls.

Fate

[havlicek]

So Barney got me thinking (a dangerous thing!) with the picture of that cool skewed-lam arm of his. I took apart an old Mabuchi 16D arm and put on a new shaft and twisted the blank until it looked like the Big Jim arm in Barney's picture. I used a Mabuchi arm (hence the thicker lams) because those are the only ones I can get all the lams apart on without distorting them. I installed a recycled Mura com and got busy with some #25awg wire and wound up with this. It was a bit fiddly to get the blank skewed and winding was a little odd. I had to be a little more careful drilling/balancing as the center of the crown is skewed top to bottom as well and I didn't want to drill in the wrong place ..but doing the arm skewed didn't present any serious issues.



-john

[Jairus]

Weird to say the least but nicely done!

[dc-65x]

I like it! There was one like that in a R&C race report in 1966:



NEAT!

[havlicek]

Thanks Jairus...it was a bit strange working on it...I guess I'm just programmed to think..."straight"

Rick, wow, if I had known the idea went that far back I would have done something more appropriate for a Mabuchi like a 28awg. I do have a few black one hole Champions here that might work sorta...with some beefing-up. I also screwed-up a little on this arm, meaning to make the overall length around 1.150" and making it 1.115". Oh well, a coupla arm spacers will get me there

-john

[Bill from NH]

John, not to change the subject, but have you ever tried to grind balance an arm like Champion first did & later Joel Montague did on his X-12 arms?

[havlicek]

Hi Bill,

Yes I have, but I think it's sloppy looking. It's actually a safer way to do it as you can remove more weight with less risk of screwing things up. I have no idea which is less destructive to the field potential, but I think it's nice for things to look tidy and have been working on that for...months

-john

[Champion 507]

JUST SLIDE THAT BENCH GRINDER OVER HERE...I'LL BALANCE IT FOR 'YA!

(why do I feel like a bench ground rotor sandwiched in between two broken magnets? )

[don.siegel]

John,

The skewed arms actually go back a ways, and were typical of the Lindsay, a model train motor favored by early drag racers... Not sure what the advantage was supposed to be: I seem to remember something about smooth pickup, just what we need on a Blue King...

Don

[havlicek]

Hi Doug,

...what about a sawzall?

-john

Hi Don,

I remember seeing that very motor posted here...I think by you (?...the memory ain't what it once was I'm afraid) and believe I've seen other adapted factory motors like that, but don't recall seeing Mabuchi rewinds done with skewed arms until Rick posted that picture from 1966. Almost all of this stuff is lost on me even though I was slot racing by the mid 60's and only saw some of the padlock type motors besides the ubiquitous Mabuchi cans. If it weren't for guys like yourself, Rick, Philippe and others here who know about this stuff and even still have the hardware and old articles(!) to show, I wouldn't have a clue At this point, it's almost like I'm discovering for myself only now what many here have known for decades

From what I gather, and it makes some sense to me, the aim of the skewed arms was to reduce the cogging effect of the magnets by having each pole's coil remain energized slightly longer (as though it were a wider pole piece) as it passed by the magnet. The result may not have been any real advantage in terms of lap times and I assume that's why it never caught on. Still, it seems likely that it also wasn't a disadvantage and I figured it would be neat to reproduce one (and maybe some more in the future) to have for when someone wants to test one out. I'll probably do some more as either a 27, 28 or 29 just for giggles at some point, now that I'm familiar with them.

Thanks as always to you and Rick for the documentation and filling in the history!

-john

[Hworth08]

During the early Mabuchi era it was fairly common for the stack to be "self-skewing", even after being rewound with a little epoxy. I don't recall a motor ever changing after the arm skewed.

[Champion 507]

Almost all modern model train motors (primarily HO) have skewed arms. Where we don't care how much magnetic field "cogging" we have in our motors, it's a really bad thing for trains. The push in that hobby for the past 15 to 20 years or so has been for smoothness of running and operation. I know even some of the can motors that come in some of the better quality locomotives today bear a strong resemblance to a Parma Deathstar. The cans are almost identical except they have closed flat sides but the endbells are different. Almost always the arms are skewed and most of the time they are 5 pole but many are 3 pole.

I can see where some tracks you wouldn't want brute torque coming out of some corners and would want to smooth out the power curve of a motor by skewing the arm. Makes sense to me. Never tried it though.

[Prof. Fate]

Hi

I first saw skewing in an old train mag in the 40s that I was reading in my club's library as a kid. THESE days, train guys commonly have a power supply designed to not just give power, but dial up slowly to make the train more realistic as it pulls from a stop. That old article asserted THEN that the skew made it easier for a train guy operating the power by hand to produce the "prototypical" effect.

None of my skewed arms in the 60s produced a winning motor. So, I only did a couple, back in 63.

Fate

[havlicek]

...and yet another Mabuchi with a salvaged Mura com, new shaft and ...something "askew" This time a 27awg


-john

[Slotgeezer]

...and yet another Mabuchi with a salvaged Mura com, new shaft and ...something "askew" This time a 27awg


-john

Beautimous !!!!!

[Champion 507]

Mitey purty Mr. H.

[havlicek]

Thanks guys. I hope to have the time to spin them both up over the weekend. They both meter the way I would expect them to, but I am wondering if they'll behave any differently on the power supply. I blame this all on Barney

-john

[Slotgeezer]

..... I blame this all on Barney

-john

Barney's shoulders are pretty broad, so I'm sure he'll gladly take the "blame" !! LOL!

[havlicek]

Well I just gave them both a whirl on the power supply The 27 is very smooth, runs cool and draws only a little over 2 amps...it runs like a 27 I didn't have the nerve to spin the 25 all the way up , but even with the big wire and more aggressive timing (the 27 was only a little advanced) it seems to run fairly cool, smooth and draws just a bit over 3 amps. As you would expect, the 25 feels much more torquey and the revs are scarey...more of a "brute". The 27 feels fast and wants to rev. Considering these were done on Mabuchi blanks with recycled coms and replacement shafts, I'm very happy with the way they came out. If I had loose .007" lams to assemble the stacks from, they might be even better, although the improvement would probably be modest. Still, with these things...a little improvement here and there can add up. Of course, the real test to see what's what with the skewed lams would be to put these in a car and get some track time.

-john

[Champion 507]

John,

With what material did you replace the shafts?

[havlicek]

Hi Doug,

I used good ol' .078 piano wire which was often used for this application. I had done some with this before with mixed results, mainly because the surface of the wire isn't slick enough to make good static balancing doable. I fiddled around some and have come up with a process for polishing the shaft that works well enough without losing any measureable diameter. Believe it or not, piano wire in the lengths required for motor shafts can be very straight and is at least as hard as the shafts on vintage motors. It works very well for this purpose, is easy to get and is cheap. As long as you don't use the shaft for doing pull-ups or prying open cans of paint, it's fine

-john

[Michael Rigsby]

John,

I have a lot of expired Chinese Pro Slot 16D and S16D arms as well as some American arms that are no longer being used. If you would like them for any reason, I will be more than happy to send them your way. There are some American 16D arms and a couple of X12 arms that maybe you can use. Just say the word and you can have them to play with. I would rather give them to someone who can do some good with them than put them in the trash.

Michael Rigsby

[havlicek]

Hi Michael,

That's very cool! Even if only a few of them can be salvaged for blanks or parts, that's a few more than I have now! PM sent

-john