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A cruel irony regarding old Mabuchi motors


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#1 havlicek

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Posted 04 November 2017 - 08:58 AM

With "serviceable" (*much less NOS) FT16D end bells being about as rare as hen's teeth at this point, it's a real annoyance that the earlier FT16 (*ie: used in the "Russkit 22" type and others) end bell is still "around" and in my "pile o' stuff" is still "there".  These had the brushes riding directly on the end bell plastic and secured by the flat hoods which were riveted to the plastic, as well as having the spring post positions "reversed" from the much better (*but still pretty bad) FT16D arrangement.

When the rules for a given race or series allows, I have done conversions on these end bells that not only takes care of the goofy original design, but also allows for the use of the 36D (modern standard) brushes and a wider diameter com.  Having long been a subscriber to Steve Okeefe's "vintage style" notion that (basically), getting close enough is a good thing, I think this is a good way to go.

The idea here is really simple, but the execution is a little on the fiddly/difficult side...mostly when it comes to assembly.  You remove the rivets and hardware by grinding-off the inside "flanged" ends of the rivets and then grabbing the outside rivet heads and rotating/twisting/pulling them out.  The two resulting holes wind up right where they will be needed for securing the new hardware, which in this case is from a Parma D motor.  The other two holes get drilled using the hardware as a guide.  On the outside/top, the hardware is spaced from sitting directly on the plastic with a set of phenolic washers underneath (excellent heat-resistance and non-heat-conducting properties), and a couple more under the screw heads.  The same thing goes for the inside.  **Of course, all the molded bits that guide the brushes as well as the spring posts themselves are removed.  I have done this with an X-Acto knife in the past, but it's easier and far more precise to mill them off, so that's what i did here.  There's also clearance on the inside already there for two of the nuts...just barely, and you have to grind a little of the same for the other two.

A last touch is that I use spring post sleeves for the posts, and to make them self-centering and a better fit for the screws, they have been fitted internally with aluminum tubing that's a nice snug "push fit" for the ID of the post sleeves.  The whole deal gets screwed to the end bell with 1-72 machine screws and nuts.  Assembling this all while holding the various bits is a pretty funny and annoying thing at the same time.  One of those things where you wish you had three or four really small hands, but it's all do-able with patience.  I also used Loctite (regular CA glue is also fine) to help insure everything stays put.

The result insulates the hardware from melting the plastic (*at least somewhat!), allows for the larger brushes and modern springs.  The stock magnets from any old Mabuchi FT16D are good for up to a #29 wind, and certainly a "warm" #30 in the 60 turn range, but going any warmer than that is never a good idea for a motor that will actually be raced in anger.
 

Here's a shot showing the finished end bell next to a Russkit "22" with the original end bell:

IMG_2298.JPG

 

 

Here's a side-shot showing the new hardware "spaced" just slightly above the plastic for some "melt insurance":
 

IMG_2299.JPG


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#2 Lone Wolf

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Posted 04 November 2017 - 10:44 AM

Nice idea and execution.

 

I'm certainly no motor expert but what would happen if you ran the big brushes with the original "22" style com.

 

Would it run?


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#3 Jairus

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Posted 04 November 2017 - 11:01 AM

That's a good point Joe and one I have always wondered about.

Doubt wear would be a problem... but it changes the timing a bit keeping one stack activated for longer periods.
Is it really a "problem"?
In the past motor builders would steal 36D brush hardware in order to have the better/larger brushes.  Yet, arm rewinders still used the smaller com.... ?  Am I right?


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#4 havlicek

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Posted 04 November 2017 - 12:34 PM

Nice idea and execution.

 

I'm certainly no motor expert but what would happen if you ran the big brushes with the original "22" style com.

 

Would it run?

 

Hi Joe.  While it might run "OK", there would be a lot of "overlap" of such a narrow com with those much wider brushes.  A similar thing happens with the very narrow coms and wide brushes in some of the modern Chinese motors.

 

 

That's a good point Joe and one I have always wondered about.

Doubt wear would be a problem... but it changes the timing a bit keeping one stack activated for longer periods.
Is it really a "problem"?
In the past motor builders would steal 36D brush hardware in order to have the better/larger brushes.  Yet, arm rewinders still used the smaller com.... ?  Am I right?

Hi Jairus,

     The wear characteristic might change some.  The original FT16 brushes seem to be a little softer than the brushes that came with the FT16D, much like those in the FJ13UO seem.  Also, the FT16 brushes are a different size (I think smaller if I remember correctly) from the FT16D brushes.  The FT36D and modern brushes seem to be a better compound in general.  ***Also, as the brushes "seat" and wear, the amount of overlap increases as the wide brush face starts to wrap around the com further.

     On the smaller com and what builders and rewinders used, guys like Philippe, Steve, Rick, Don and others would know far more than me.  I just have some things I've noticed about all this:

1)Narrow com and narrow brushes = good performance and high revs (*all other things being equal)
2)Narrow com and wide brushes = decreasing performance (*but I have avoided that whenever I could, so I don't have a bunch of results)
3)Wide com and narrow brushes = good performance and less RPMs
4)Wide com and wide brushes = good average performance and RPMs, along with good wear (*which can be significantly affected by how well the brush hoods fit the brushes, to avoid off-center brush wear).

Old Mabuchi FT16D, 26D and 36D brushes were really good and consistent.  Some modern brushes can be less so, but are mostly as good or better.  Anything more than that, and you'd have to ask a racer or builder above my pay-grade!  :D


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#5 Lone Wolf

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Posted 04 November 2017 - 02:37 PM

Thanks John,

 

Thing is, I never use my cars long enough for the brushes to wear out anyway  :D

 

A few trips around the track or down the strip and I'm done  :)

 

As you mentioned the early brushes are indeed smaller. The size is shown in MM. These can be used in the "23" style brush holders if you dress them. They also fit 26D in my experience.

 

Box of 10,000 has lasted a while now.

 

Thought you would like to see this just for shits and giggles.

 

These are the early style, notice the December 16th,1962 date code.

 

Don't know this company but these are pretty high quality. No deterioration after 55 years and they work great. In short bursts anyway  :)

 

DSC02025.JPG

 

DSC02026.JPG


Joe Lupo


#6 havlicek

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Posted 04 November 2017 - 02:53 PM

Joe...I have a lot of the ones you sold me left...like a LOT.  They are indeed very high quality and I use them for both FT16D and 26D motors (*with some dressing for whatever application).  I've never had a bad pair, and they are not overly soft at all.  On close inspection, they are beautifully formed too.


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#7 Lone Wolf

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Posted 04 November 2017 - 03:01 PM

John, I had forgotten that you had got some of these from me  :dash2: I thought I was showing you something new.

 

If I repeat myself just let me know.

 

If I repeat myself just let me know.

 

If I repeat myself just let me know.


Joe Lupo


#8 havlicek

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Posted 04 November 2017 - 03:55 PM

No worries Joe!  I was simply pointing out how good they are in case someone is in the market!  Thanks again for them though!


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#9 havlicek

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Posted 05 November 2017 - 10:23 AM

There are more ways to skin a cat than just one.  If you check these sorts of things (translation: if you are similarly afflicted), you might find that the old Mura hardware (here I used "B" bottom plates) is a close "match" for the Mabuchi D sized motor end bell. 

*Once the hoods are removed and the top of the end bell is machined (or just cut with an X-acto blade) flat, you find that the rivet holes line-up well with the larger spring post hole on the hoods.

*The little "tabs" that extend the bottom plates towards the com are slightly wide to fit the end bell, so they require a little trimming.

*Like wise, the hoods have little side "lips" that need to be trimmed to fit into the end bell openings.

*Aside from the fiddly nightmare of assembling everything as in the above, you just need to drill a second hole.

*Finally, this all puts the hoods too close together for the larger diameter com, so I carefully opened-up the internal clearance.  It wouldn't make much sense to go through all this and still have to use a smaller diameter com like a Tradeship with the wider "36D-sized" brushes.

You don't get the double-overhead spring arrangement, but at least the look is a little more "vintage-y" with the hardware being from the same decade.  :D  With the plates and hoods spaced just off the plastic using the same phenolic washers, you get some more heat-insurance of course.  So both of these methods serve several purposes in upgrading the Mabuchis.  You save some of the original DNA, can use the larger brushes and commutators, get at least some better heat-resistance, and wind up with hoods that can be aligned.

Doubtful that anyone would have done all this to a Mabuchi back then when the Muras were readily available and far better.  Now, with the Mabuchis having become more scarce, perverted little exercises like this almost make sense.  :D

IMG_2300.JPG


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#10 Jairus

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Posted 05 November 2017 - 11:00 AM

Well, I like it.  Plus I have a bunch of those old endbells.


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#11 havlicek

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Posted 05 November 2017 - 11:26 AM

Well, I like it.  Plus I have a bunch of those old endbells.

 

 

Thanks Jairus.  The earlier end bells ARE way more "around" than the FT16D end bells.  All this is kind of a pain to do, but at least it's a way forward...for now!


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#12 Rob Voska

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Posted 05 November 2017 - 11:34 AM

Can they be 3d printed?  The technology is always getting better along with the materials........



#13 havlicek

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Posted 05 November 2017 - 12:55 PM

Can they be 3d printed?  The technology is always getting better along with the materials........

 

 

Of course they can, but the materials that I see don't seem better than what Mabuchi used, maybe not even as good.  Heat-tolerance and rigidity are of course very important.  While some companies are doing 3D printing with metals and even composites, that'as industrial type stuff.  These things would need to be produced and sold for maybe $5 a throw.  Moreover, 3D printing seems best suited (*if the material is suitable) for short runs or a dozen or two.

Anyway, you don't really even need to be fluent in CAD.  A clean example can be 3D scanned to produce the file for printing


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#14 Ramcatlarry

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Posted 05 November 2017 - 01:22 PM

One of the obvious uses of 3D printing is to alter design details that were the failure point of an old part.  Increasing the bushing area for (new standard) bushing/bearings and brush hardware makes a lot of sense to me.  Alternate endbells were made to try the Pittman style brushes and springs for several can sizes.


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#15 havlicek

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Posted 05 November 2017 - 04:19 PM

One of the obvious uses of 3D printing is to alter design details that were the failure point of an old part.  Increasing the bushing area for (new standard) bushing/bearings and brush hardware makes a lot of sense to me.  Alternate endbells were made to try the Pittman style brushes and springs for several can sizes.

 

 

Well, yes, but those changes themselves can cause problems.  For example, the "Hong Kong" Mabuchis had a much more robust end bell around the bushing (and a much better plastic to boot!), much like the Champion design.  The problem there is that a LOT of chassis were made specifically for the Mabuchi end bell.  Even scratch-builders have fits figuring out how to make them work, and they're mostly using simple bent metal brackets.  The most common 3D printing materials can't handle temps up to the boiling point of water, many even less!  Think about that for a second, it's common to boil Mabuchi end bells in water to dye them a different color.  Actually, doing that seems to have a beneficial effect on the Mabuchi material.  3D plastics/polymers can't even match that.

Some of the end bells made for the Pittman style brushes seem to have been made from a slightly better material, although that brush style is awful...far worse than the Mabuchi.  That right there is a humorous little tidbit from back in the day!  :D


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