339 replies to this topic

[Gator Bob]

     Every once in a while, I'll go down to "the dungeon" and start looking at parts for inspiration.  Sometimes it's for a "more or less" correct project, sometimes it's for one of those "well, if I cut this and sand that, I might be able to fit the other doohickeys to the whatchamacallit" projects and sometimes it's for one of my "I don't give a dang" projects.  So last week, I found a pretty nice Mura "B" can with a butchered end bell.  The can got stripped and flattened, and I installed a nifty ball bearing in it rather than replacing the *REALLY* worn bushing, but the end bell's screw holes were all stripped and there was no hardware!?  Since Mura C hardware will fit (I know...the period police will gasp!), a running motor could easily be fashioned, but it would have to be an "I don't give a dang" motor.

    So, after staring at the pieces for a while, I started to look for some nice magnets and I do have some...BUT...I also started staring at some D-motor magnets which are PLENTY strong and sort of a good fit (actually...a little too tight with the thin metal "clips" normally used with those).  My demented brain (or what's left of it) started considering options and I came up with the formula: B+D+BDA/KDW= NP (B motor + D magnets + Big Diameter Arm divided by some Krazee Double Wind = New Project).  So I sez to myself..."self, make an arm and do a fairly stooooopid double wind, then stuff that thing in the B".  Being totally oblivious to the concerns regarding the B motor's proclivity for getting into BBQ territory, I dun-did me a #27 double wind on the .560" x .460" blank I cobbled together for this "I don't give a dang" project.  Welp...the arm is all done except for going out for balancing and it will be a fire-breathing sonofagun for sure...coming at .103 ohms.  Best part is, it meters precisely the same across all three poles.  Double winds (for me anyway) will usually have a point or two variance just because it's hard to keep them neat.  Here, the big diameter arm blank allowed me to get the right number of turns on there in only four layers like a normal single wind, so things stayed pretty neat...for a double wind anyway.  I'm going to look through my "pile-o-stuff" to see about a clean B end bell while it's out for balancing.  That way, even though it's so incorrect on the inside it would make a purist cry, it'll at least look the part on the outside  Anywho, this one oughtta really dim the lights in Fresno, since it's a #28 double wind!  So that's my story and...oh yeah...here's a super secret spy photo.  

 

 

-john

 

 

 B+BB+D+BDA/KDW= NP (B motor +Ball  Bearings+ D magnets + Big Diameter Arm divided by some Krazee Double Wind = New Project).  

[SlotStox#53]

Holy smokes John!!!! When you go crazy , you really go CRAZY! !! I love it

Have you got a car lined up for this fire breather to be chained into??

[havlicek]

Hi Paul,

 

 

 

Holy smokes John!!!! When you go crazy , you really go CRAZY! !! I love it   

Have you got a car lined up for this fire breather to be chained into??

 

Nope.  I don't really build cars anymore and this one will go up for sale when it comes back from balancing.  It's a concept I sort of just happened on when  staring at the parts.  I notice above that I say it's a #28 double and then also say it's a #27 double...now I don't remember exactly what I did, but at slightly just over a tenth resistance, I'm pretty certain it's a #28 double, as a #27 double would surely be under a .1 ohm.  It should be somewhat more well-mannered than a #25 single though, since that's typically the way these things work out...crazy revs but a "softer" torque curve and easier to get "hooked up".

 

-john

[SlotStox#53]

Gotcha So is the whole "crazy revs, but softer torque curve " thing the same for all double winds?

 

Reach the same overall result on the #'s side just with different characteristics

[havlicek]

Gotcha So is the whole "crazy revs, but softer torque curve " thing the same for all double winds?

 

Reach the same overall result on the #'s side just with different characteristics

 

That seems to be pretty much the case with doubles *as compared to their "equivalent single wind" Paul.  One of my eBay buyers told me that a doublewind was/is (?) a record holding drag motor because the torque is more manageable and the car can get better traction off the line.  I don't know if it's true or not, but it makes sense.

 

-john

[Gator Bob]

In theory it makes sense to me John.

 

Same resistance but 'in the field' it's a longer total piece of wire. The 2 different lengths of wire on a single pole means any given pole is energized twice and with a 'softer' application (charge/discharge) of 'Energy' in the total "Dwell Cycle"..

 

Although don't go by this ..... because when I used the term 'skin effect' a while back I was told to STFU by the experts.

Edited by Gator Bob, 11 May 2014 - 04:54 PM.

[havlicek]

Well...I just stick by what I know works by blowing stuff up Bob...you know...the old fashioned way!   A DC motor even as simple as these, is in actuality a mind-numbingly deep system.  You start to dig into how these things work and why the act the way the do, and your head will explode...

 

-three spinning electromagnets being energized in sequence (and with current changing directions)

-changing kinetic energy into electrical energy AND changing electrical energy into kinetic energy simultaneously

-being acted upon by a magnetic field whose distance and strength can be altered, enclosed in a steel can whose shape affects that same field

-a current path dependent on brush type, spring type and tension...plus end bell hardware

-movement (and current draw/efficiency) affected by balance/imbalance, bushing or bearing alignment, end play etc.

 

...and too many more things to consider.  Still, that doesn't even take into consideration the wind, com timing, lamination shape/thickness/steel type.  

 

-john

[Gator Bob]

Yup, for sure .... there is a lot going on in there  ... maybe that's why sealed motors are so popular.

If the 'vent holes' get banned to really seal'em up the we would "See no evil .. hear no less evil"

 

Pushing the limits the old fashion way   

Build'em  and then  'em up.

[havlicek]

shhhh...a baby Walnut ^{TM ,} just born and sleeping  (turning around and tip-toeing).

 

 

-john

[SlotStox#53]

Looking good John which lams are you using for this one?

[havlicek]

These are a wider crown lam Paul, but are the same OD (roughly .518") before grinding as most.  On this particular motor, I'm going to do a pair of arms...a #27 and a #29.  The 29 winds work really well in these little guys with the ceramic magnets, the #27 is getting pretty close to the edge.

 

-john

[havlicek]

     With things slowing down as the warm weather is here, I'm looking to do a modern C-can arm,  just because I haven't done any in a while.  Could be for drag or road race.  Ideas?

 

-john

[SlotStox#53]

Sounds like a fun project

Came across the 24# and 27/28# bubblegum arms I had safely tucked away in the motor box last night. Would something stout like that satisfy the criteria?

[Gator Bob]

Double 32 or maybe a good old (modern) GR20 wind?

[Samiam]

A tagged Gp-20 in a red can like MURA did it BITD. Stick it in a clear box glued to a H-Power card and you have an instant classic. I still break out my Gp-20 wing cars once in a while. Fun motors.

[havlicek]

G20 was a #27 wind right...like 38/27 or something?

 

-john

[Samiam]

Here's a handy chart John:

 

http://zippitynz.com...matureSpecs.htm

[havlicek]

Thanks Sam...38/27 is what I thought (or around there).  I'm going to do one up as soon as I clear away a little more work that came in here.

 

-john

[Bill from NH]

This motor chart was first created about 12-15 years ago by a MD wing car slot racer no longer involved in the hobby. I sent Zip a copy awhile back & he added some newer motors & has kept it updated ever since.

[havlicek]

Keeping it "old school" for a Blogger.  A #31 doublewind done on the stock Mabuchi (Russkit) stack.  The can was stripped, end bell tabs broken and ground, magnet tabs flattened and filled and painted "Hammered Green"...nice color I haven't used before.  Like the rest of the "Hammered" series, the paint seems to cure to a nice hard finish after baking.  This one I wet sanded after the first coat/bake job and did a second coat...why?...I don't really know.  The can bushing was also replaced and the old shaft replaced as well.  Commutator by Bill Bugenis.  I was going to silver solder this one because brazing with skinny wire kinda worries me, as one slip and you can vaporize the wire.  I put a new point on the electrode, went slow and careful and ...no problems.  Even a #31 double on this stack comes in at a healthy .246 ohms (measure perfect across all three poles)...hopefully everything will be A-OK with the stock/un-bulletproofed end bell!

 

 

-john

[SlotStox#53]

A thing of beauty John very nice looking double wind

[Don Weaver]

MINE!!!

 

Don Weaver

[SlotStox#53]

Nice motor Don!

[havlicek]

Yeah...the thing really has some stones.  Funny, I do so many scary motors...you forget how serious "even" a #31 double is.  

 

-john

[Marty N]

John, if you don't mind. How many turns was this wind?