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The good ol' "13UO" Mabuchi


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#1 havlicek

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Posted 18 November 2017 - 08:36 AM

  The littlest Mabuchi found it's way into the hearts (*and cars) of a good number of kids.  It was easy to drive (*ie: slower'n molasses in January), lightweight and could fit into the smallest/skinniest cars as an inline.  Try and make it go faster with either a dewind or a rewind though, and it was an exercise in frustration.  The end bell, short of doing the kind of things no kid could do back then, was pretty much a no-go...but at least the motors were can drive, so there's that anyway.  The magnets are/were (*even by Mabuchi standards) absolute junk, and there weren't any alternatives, at least not sold for slot cars.  Now, we can do all sorts of things to these motors...even if the aim is to still have them be pretty stock looking from the outside and fit right into vintage brackets and cars.  That's my M.O. here.  

The starting point is a generic plated version.  You power up one of these things and it's amazing they could even push a car:

IMG_2319.JPG

So, I took apart the motor, toss the original quasi-"magnets", strip the can of it's very thin plating, remove the rotating can bushing, trim a set of poly-neos (*the similarly-sized modern ceramics are excellent for these too) to fit and epoxy them in:

IMG_2320.JPG

I also did something a little different here.  Removing the rotating bushing for a fixed oilite eplacement (*builders sometimes just glued the rotating bushing in place) helps keep things more solid, but that leaves a bunch of space in the can.  I stacked two oilites (epoxying them together) for extra bearing-length, MAKING SURE that everything was aligned, and then embedded both in epoxy so they're both locked-into the can as a unit.  After that, I faced the inside of the bushing-stack to make sure there was a "true" face for the arm to ride against.  To be safe, I decided to do all this in two steps, to avoid fouling the inside of the two oiltes with epoxy-bleed/seep.

IMG_2321.JPG

On the outside, it all remains "pretty" stock looking, but most importantly, the motor's stock dimensions remain intact.

IMG_2322.JPG

Like I said earlier, the end bell (*without changing the whole arrangement, or even substituting a modern one) is pretty much a "brickwall", but that doesn't mean that this motor can't be MAJORLY improved.  All things considered, and to wind up with a motor that's still "pretty much" a 13UO, I'll do a #30 wind here (65/30).  With a Tradeship com and a shorter stack, there will be plenty of RPMs and brakes in a smooth, reliable Mabuchi.


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#2 Geary Carrier

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Posted 18 November 2017 - 11:43 AM

Hi John,

 

How accurately do you weigh the resin and hardener for the 100/17 mix ratio of the Duralco 4461?

 

How critical is the mix ratio to obtain the desired properties of the cured epoxy?

 

Is there a minimum batch size that you mix or have you found the performance of the cured epoxy independent of batch size?

 

How critical is the curing schedule for obtaining the desired properties of the cured epoxy?

 

 

Thanks,

g


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#3 havlicek

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Posted 18 November 2017 - 01:50 PM

Hi John,

 

How accurately do you weigh the resin and hardener for the 100/17 mix ratio of the Duralco 4461?

 

How critical is the mix ratio to obtain the desired properties of the cured epoxy?

 

Is there a minimum batch size that you mix or have you found the performance of the cured epoxy independent of batch size?

 

How critical is the curing schedule for obtaining the desired properties of the cured epoxy?

 

 

Thanks,

g

 

 

Hi Geary,

 

None of the above involves 4461, it's all JB Weld so far, which is about the best "general use" epoxy that's widely available...so long as you don't mind "battleship gray".  :D

Still:

The 4461 is fairly tolerant of mixes away from the stated ratio.  A little more catalyst and the stuff will harden a little faster.  A little less, and it will take a bit longer.  Way too much catalyst and the stuff can foam...even after you think it's cured.  Way too little catalyst, and the stuff can never fully harden, but for either of those scenarios, you have to be pretty far off.  I use disposable plastic syringes for both the resin and hardener, and don't measure the stuff anymore after years of using it.  I seem to pretty well "land" on the right mix ratio by eye (*and I count the drops of catalyst that I add to a nickle-sized blob of the resin).

Of course, achieving the right strength and heat-tolerance is dependent on the right mix ratio...to some extent.  How much?...beats me.  Like I said, it all seems to work well for me.

Batch size doesn't seem to be all that important, as I use really small quantities for a "batch".  Sometimes I use much smaller amounts for the odd "special" job aside from potting armatures, like keying/bonding bushings  or bearings to end bells.

Cure schedule also doesn't seem to be all that critical.  While 4461 CAN cure at room temp, that takes a while.  I always speed-cure the stuff by warming it to around 200F.  

***Like most 2-part resins, the materials DO have a definite shelf-life.  As it gets older, mix ratios can start to slightly change, as does the way it cures.  You can GREATLY extend the life of the material by keeping it cold.  I only keep the syringes out at room temp (*each of which can do a lot of armatures), and keep the bulk of the material in a small "apartment fridge" in the garage.

 


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#4 Geary Carrier

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Posted 18 November 2017 - 03:31 PM

Thanks John...


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#5 havlicek

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Posted 18 November 2017 - 04:21 PM

You're most welcome Geary!

Speaking of 4461, the end bell on this motor was minty...EXCEPT for the typical cracking around the bushing.  These bushings are not just tiny, they are also not a great fit for the shaft in the first place.  On this NOS motor, the bushing was about ready to fall out...NOT COOL!  So, I decided to try something I've been meaning to investigate in the past.  I rummaged-around in my pile o' stuff and found some tubing that was close to a fit for the outside of the end bell around the bushing area.  I reamed the ID of the tubing until it was a tight press-fit.  Then I drilled itty bitty holes in the end bell and cut off the piece of tubing so it would be proud of the end of the end bell...drilling some itty bitty holes in that too.  Then I put some 4461 around the bushing and reinstalled it so that I could see epoxy just coming out the holes.  Then I coated the inside of the piece of tubing and pressed that onto the end of the end bell.

When all that was cured, I clamped the end bell in the milling machine and trimmed the end down to around the end of the end bell.  Just the fact that the brass ring stayed put while machining it makes me feel good that everything is locked in place pretty danged well.  The bushing/end bell plastic and brass reinforcing ring should all be bonded and keyed to each other.  The motor actually feels slightly better just spinning an armature in it, and with the can end being the drive end, this should help the motor live a longer and happier life.

IMG_2323.JPG

 

Sometimes (not all that often) a plan actually works!  :)


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#6 havlicek

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Posted 18 November 2017 - 08:50 PM

BTW, with so many of all Mabuchis...NOS or already run...having the end bell crack, this seems like a good fix.  For brass brackets, opening-up the center hole some should be do-able.  For the cast alloy and magnesium frames...maybe a little grinding.  You're NOT actually bonding to the Mabuchi plastic, so drilling the holes is really where it's at.  The lo-viscosity of the 4461 seems to be an asset here, but I think regular Devcon might work fine.


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#7 Racer36

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Posted 18 November 2017 - 11:18 PM

I think I may have a home for this when it is done......
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Dennis Dominey

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#8 Kim Lander

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Posted 18 November 2017 - 11:24 PM

I love the one  you did for me John....cool little motors.


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#9 Geary Carrier

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Posted 19 November 2017 - 01:19 AM

Hi John,

 

You've designed an innovative fix for all those cracked end bells, well done...

 

You could also thread the ID of the brass ring and screw it on with your Forbidden Planet micro spanner.

 

 

Thanks,

g


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#10 havlicek

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Posted 19 November 2017 - 07:31 AM

 

 

You've designed an innovative fix for all those cracked end bells, well done...

 

 

Well, I don't know how innovative it is Geary, but thanks!  The concept seems awfully simple, and one way or the other, enclosing the end bell around the bushing with some sport of metal seems like a natural thing to do.  I didn't want to use the end bell mounting holes for a bushing strap as in the Champion "Orange Picker", because that creates as many problems as it solves.  The only difficult thing here is figuring out a way to keep this all together, because you can't bond to the very slippery end bell plastic of the Mabuchis.  Here, the ring and the bushing are actually bonded to each other through the plastic and keyed to the plastic.  It seems pretty danged solid, and shouldn't cause much of a problem for mounting the motor in the traditional way (* a circlip on the can end and a screw or two on the end bell to stop it from rotating and give it rigidity.

While I've done some of these hotter, a #30 wind still seems like the best choice for much improved performance and reliability.  We're still dealing with the same basic motor as the stock 13UO here, just mods that should help improve the durability of the platform.  Again though, having a set of what are functionally the equivalent of the later Mura metal "hoods" arrangement here, one of the actual good things almost never mentioned about the 13UO is offset by the fact that they still sit on the same melt-o-matic plastic.  The challenge with the 13UO is to get a solid peformance bump within the limitations of the basic motor's flaws.  Magnets, MUCH better bushings in the can (*driven end) and a solid way to keep the end bell together should all work towards that end.  In this motor, a 65/30 arm will be a big deal!


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#11 havlicek

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Posted 21 November 2017 - 07:31 PM

...and Bam!  Well, actually, I had to wind two arms.  The first one took more than I'm comfortable with to true the Tradeship com, which would mean a shorter life.  So I wound a second one, and then it was "Bam!".

With the neos, these little guys seem to have really good torque.  With modern ceramics, they skew more towards RPMs.  As-is, with a 6530 wind, this is a just-under-one-amp motor, and you don't want to go much hotter (if any) than that here!  Because of the freaky-backwards/upside down hood arrangement on these things, it took my like 4 or 5 tries to wind a set of springs.

IMG_2325.JPG IMG_2326.JPG IMG_2327.JPG

 

-john


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#12 Geary Carrier

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Posted 22 November 2017 - 12:50 AM

Nice-very nice...


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#13 Jaeger Team

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Posted 22 November 2017 - 03:00 AM

Hi John,

your's project syntax is smart, clean and powerful as usual. If I can ask what the airgap is?


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Maurizio Salerno

#14 havlicek

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Posted 22 November 2017 - 06:05 AM

Hi John,

your's project syntax is smart, clean and powerful as usual. If I can ask what the airgap is?

 

 

Hi Maurizio,

     Last I checked (*as I was building the motor) the airgap was around a total of .025"...or something like .0125" per side.  I didn't take final measurements when I was assembling, but that should be about right.  These little motors always wind up being more work than doing an FT16D...they're just weird in several ways.  I get a kick out of them when they're done though, because I remember how frustrating they were for me as a kid.


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#15 Jaeger Team

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Posted 22 November 2017 - 07:20 AM

I have identical memories and feelings. 

Ciao !


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#16 Racer36

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Posted 22 November 2017 - 08:07 AM

This little gem is on its way to my house.

 Thanks John!


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#17 havlicek

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Posted 22 November 2017 - 08:26 AM

Thank YOU Dennis!


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