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Another channeled & chopped Mabuchi motor


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#1 havlicek

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Posted 22 January 2017 - 01:45 PM

Maybe better called a Murbuchi... or even a Murbuchicek.  :)
 
I set out this time to do things a little differently and come up with a motor that would have done a racer proud back in the day... and maybe even look sorta right for the period on the outside anyway.

First off, I sliced one of my favorite early Mabuchi 16D cans horizontally. After some cleaning and deburring, I got a rough can that's as close or closer than I've ever gotten one before. How close?... Well so close that the can tabs were sliced in half and both sides of those went right back together after brazing! Nobody is more surprised at this than I am.  
 
Here's a shot after the brazing mess was cleaned up, and I soldered a pair of shims to the inside of the can's two radiused sides. The silver stuff you see is solder that got outside when I soldered those two shims in place.  
 
This time I'm using a vintage Mura C-can endbell, and the shims will (after some figuring and measuring and figuring again... then hoping) make the Mura endbell a nice snug, but not too snug fit:

 

IMG_1934_zpsldvzqetn.jpg

Now, lest you think I embarked on this journey out of some quixotic quest for cheap thrills alone, there's a functional reason for all this stuff... but I do like doing one-off things for the heck of it as well!  
 
First off, the can is now shorter than a C-can in height. You can see that the endbell is proud of the can's flats, and it's hard to see, but it's not just a smidgen... it's enough to actually be a good thing in lowering the CoG of the motor, which would also help an intrepid scratchbuilder lower the CoG of an entire chassis.  
 
Notice the radiused corners of the stock Mura endbell in the above and following pictures. Those will give you an idea of what we're talking about here.  ou can also see the interior shim adapters for the Mura endbell, as well as where the can slice went right through the tabs. Oh and, I also had to match the can drilling to the existing holes on the Mura endbell. I hate doing that, but it came out fine this time (whew!):

IMG_1936_zpsoae7rmer.jpg
 
Here's a shot of the business end of the can with a nice bearing soldered-in. More goodness about doing things this way is that the endbell end of the can is well-reinforced by having those shims soldered-in to the inside, and the drive end of the can is reinforced by the bearing having been soldered-in.  
 
Of course, the magnets will be epoxied into the can as well which will further reinforce everything. The end result will be nearly as strong an the original uncut can for sure.  
 
At this stage, I still haven't drilled the can end for mounting, but I did notch the can to help the chassis builder get a few more degrees of angle out of the motor:
 
IMG_1937_zps3cmiu2xj.jpg
 
An interior shot with the bearing soldered-in, and strengthening the whole shebang:

IMG_1938_zpswostabqg.jpg
 
Next up, I first sanded the can down to get it pretty flat, and applied some JB Weld wherever needed to act as a coat of Bondo. Then that got sanded as well. I mean, fast is good, "custom" is good, but neat looking is good, too!  
 
You'll also notice that the endbell top and bottom have been sanded flush to the can's flats. No sense in having a not-so-tall can if the endbell is hanging out... or down. Oh and, the endbell is now a perfect snug "snap fit" to the can. By the way, this is the 'bottom" of the can and you're seeing what small amount of the magnet tabs are left:

IMG_1939_zpspddysoig.jpg
 
Next up, the can gets an undercoat of high-temp paint. The color doesn't matter, but it will serve two purposes. First it will give a smoother result, helping to fill-in even smaller details that the JB Weld can't do so well on. Second, JB Weld will often "telegraph" right through a top coat of paint. When the first coat of paint is wet-sanded (with #600), you get a smooth base, and one with the JB Weld sealed-in:

IMG_1940_zpshw81ok3n.jpg
 
After a second finish coat of hi-temp wrinkle black, and the endbell sanded flush and fixing the loss of color where it was sanded, it's pretty much a finished can:

IMG_1941_zpsiepadq2j.jpg
 
So, it's unique, strong and functional... plus significantly lighter than a Mura Green can. The other things here is that, installing a set of typical C-can magnets, you wind up with about a .580" "hole."  Wel,l boy howdy, that sounds about perfect for a .560" diameter arm!

IMG_1942_zpssc88etk4.jpg
 
So, while the outside looks pretty vintage (and of course, this sort of can surgery was not unknown back then), the inside will be "vintage style."
 
Whatever you call it, this motor will be a nice -ooking bomb! Next up, installing the magnets so I can build/space/wind a "heart" for this beast.
 
-john


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John Havlicek




#2 Steve Deiters

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Posted 22 January 2017 - 01:51 PM

Just when you think the world of rewind can't get any more off the hook...


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#3 havlicek

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Posted 22 January 2017 - 02:31 PM

Thanks a heap, Steve!  

 

I had this one last photo in the previous batch, and was going to save it to use with the next post, but I'll toss it in here. Building and making stuff always involves some sort of problem solving. Sometimes I don't think of better ways to do things until after I've already struggled with a dopey way to do things. :D  Anyway, this is how I sometimes set magnets' positions when it's appropriate.

 

To get both magnets the same distance back in a can, as well as to a particular distance, I don't have any high-tech stuff. What I do is to drill an endbell and install a couple of screws. These can be turned in so they stick into the can a set distance and can easily be adjusted and measure so they're both the same. Install the magnets with a set of clips, push in the end bell and... et voila! They'll slide right in to a set a correct distance and will be the same exact (or certainly close enough) place on both sides:

IMG_1944_zps3bb1p4v9.jpg

It's quick and dirty, but works perfectly. Also, it doesn't ruin the endbell. The holes aren't big enough to weaken the endbell and will be covered up by the hardware anyway.

 

I'm sure motor-builders have come up with better and more elegant solutions... this is just what I came up with.

 

-john


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#4 swodem

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Posted 23 January 2017 - 09:27 PM

Maybe better called a Murbuchi... or even a Murbuchicek.  :)


So if you had to do it all again, do you call that a Re-cek? ;-)

#5 MSwiss

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Posted 23 January 2017 - 09:43 PM

I doubt John will have a clue to what you are talking about, unless he does some Googling.
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Mike Swiss
 
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#6 swodem

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Posted 23 January 2017 - 11:31 PM

Oh no, nothing worse than a joke people don't get.  :-(



#7 havlicek

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Posted 24 January 2017 - 06:19 AM

What Mike said!

 

-john


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#8 havlicek

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Posted 29 January 2017 - 09:14 AM

So while I'm waiting for the arm to come back from grind/balance, I got busy on the last details of this build. First off, the paint "flashed" a little towards the can end... no doubt the paint was a bit heavier down there so it wound up looking a little shinier than the rest of the can... which bugged me. Instead of going back again and redoing what was a tedious paint job, I grit my teeth, squinted my eyes, held my breath and overshot the paint to see if I could even it out. Thankfully that worked fine!  

Last, I had to get the end bell hardware all squared-away. In keeping with the "scratchbuilt" theme here, I made up a set of buss bars. It's been a while since I had done this, so (again... thankfully) I had forgotten what a fiddly PITA that is to do. Cutting them out and then straightening it all to the scribe lines by nibbling and filing and sanding is one thing, but getting the two bends of the rear buss bar to work around the end bell plastic is a whole 'nuther thing... and that took longer than the actual cutting. Mark a little, bend a little, peen a little to straighten out the bend, re-bend a little, re-peen until it all works. The bends aren't as crisp and square as I would have liked, but not so bad at all.. .considering the brass I used is a little thicker than what Mura used. About 14 weeks later I got it. (OK, that was a little of an exaggeration.)

Anyway, I now have a completed set-up. When the arm comes back, it will be all ready for final assembly!

IMG_1946_zpsmglznvk7.jpg


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#9 havlicek

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Posted 19 February 2017 - 10:30 AM

... Bam!

13f04f25-4c82-4306-8a4c-42d4f4172e5c_zps

ccd857b1-33a2-4b28-8269-9c6f51cd5c83_zps
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John Havlicek

#10 Geary Carrier

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Posted 19 February 2017 - 11:52 AM

Hi John,
 
Love that black sinister look...
 
What method of balancing is used on this armature?
 
Why was this done as opposed to drill balancing?
 
Thanks,

g

Yes, to be sure, this is it...


#11 havlicek

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Posted 19 February 2017 - 12:18 PM

Hi Geary and thanks!

 
The arm was drill balanced (referring to the method of removing material from the stack, not the actual balancing technique itself).

 

In this case, a relatively large amount of material was removed from all three poles (double drill holes). It would seem like that's weird because the difference between the poles is much smaller, but the balancer probably was chasing an imbalance around the arm. That can happen sometimes!   :D


John Havlicek

#12 olescratch

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Posted 05 April 2017 - 01:05 PM

Do you remember the specs on the arm used in this build?


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#13 havlicek

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Posted 05 April 2017 - 04:23 PM

Hi John,

 

I'm pretty sure it was a #28 wind. On that diameter, it's 45-50 turns.


John Havlicek





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