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The Mura "Green" C-can motor


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#1 havlicek

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Posted 28 February 2016 - 06:27 PM

Undoubtedly one of the iconic slot car motors, and to me one of the sexiest. Recently doing a Mura "B" got me to thinking I haven't done a Green Can in a while... so it was "off to the races", figuratively speaking.  

Before building an arm/pressing lams, you need a set-up. Hunting through my "pile-o-stuff", I was able to come up with some likely candidates. While not as difficult to come up with as the "B" motor stuff (and I have zero of the 16D "A" stuff), clean Green Cans and the proper magnets, etc., is getting kinda slim. So I got me a pretty clean-looking can and went about stripping it, cleaning it, flattening it... just generally undoing all the stuff that racers did to these things. Most often I'll use a fresh oilite in the can because it's hard to justify the cost with what people are willing to pay, but on this one I figured what the heck (*besides, I can always say no!). I also cleaned the magnets of all the old glue.  

 

So, aside from paint, all I have to do if get together an endbell, although that too takes some doing! Step one:

one_zps5lmjr1kz.jpg
 
Like I said... these are some sexy motors!
 
-john


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#2 team burrito

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Posted 28 February 2016 - 10:04 PM

i just put this one on eBay today:

 

s-l1600.jpg

 

The original endbell was too damaged and had to be replaced with the new style.


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#3 havlicek

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Posted 29 February 2016 - 06:31 AM

Nice one, Russ!  

BTW, the endbell in the background is "representative" of the sort I have kicking around. It has a mish mash of components that are of the general period. The top bussbar has been radically shortened for body clearance and the front one is (I believe) a Champion or other brand, but has obvious advantages for those reeeeaaaalllly low bodies. I don't know that I'll be using either of them, but maybe. I'll sometimes cut the bussbars a little myself... or let the car builder do it if need be. But all the hardware needs to be removed and cleaned. I prefer button head screws that take the standard sized allen wrench such as I used in the "B" motor build. The Mura screws can be a little short on the spring posts, and you'll often find the plastic ruined on the posts because the screw was tightened a wee bit too much.  

 

The magnets here are the right ones for this can... long and strong. In stock form, they yield a "hole" here around .525'-ish. A little on the tight side for the modern lams I have that are .518". The Mura arms were .510", but I'll make up an arm that is on the long side... maybe even .500" long or just under to go with the long magnets, and probably finishes at around .512"-.515" diameter. Keeping things neat and tight means that I don't have to wind a crazy hot arm here to wind up with a motor that "sings soprano." A #26 will definitely work, but I often wind up grabbing the #27 wire for all kinds of motors.

 

-john


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#4 Bill from NH

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Posted 29 February 2016 - 09:37 AM

One thing I did to the Champion, Mura, and other plate style buss bars was to use a small pair of needlenose to rotate the end 3/16" 90 degrees. That way I had a flat horizontal shelf to solder leadwire to rather than trying to solder it to a vertical surface. It made motor changing during a race event go quicker with fewer burns. On round wire buss bars, I would turn back the last 1/8" or so 180 degrees to make a small soldering shelf.


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#5 havlicek

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Posted 29 February 2016 - 08:46 PM

Well... the arm is done. I built a stack around .480" long and did a 26t/26 wind. This may not "dim the lights in Fresno", but it for sure will make them flicker. Comes in at comfortably less than .1 ohm... or .081 ohms to be precise.  

Now while it's off being ground and balanced, I can work on the endbell and spiffying-up the can.

arm%20comp_zpsc4nc9zlu.jpg
 
-john
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#6 rodslot53

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Posted 01 March 2016 - 07:16 AM

Hi John,

How do I identify a Green can from other Mura cans? What are the benefits of a Green can?

Thanks,

Rod.
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#7 havlicek

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Posted 01 March 2016 - 08:05 AM

Hi Rod,
 
The Mura "Green Can" is the two-hole model. Later, and up to today, the C-can became the standard and there have been a seemingly endless number of designs... some more "open", some heavier and more "closed", but the dimensions aren't far off from the original.

The "Green Can" endbell had a different tower than later designs from Mura and others, and a lot of motors were sold with Mura end bells and slightly different hole designs when the C-can took off.  

Now, other Mura motors had "two-hole" designs besides their C-sized motor, and to make things even more confusing, some people reamed out the two holes on the Green can as well as some of the others to make them larger. Before the C-sized "Green Can", the Mura "B" motor became available in a seemingly endless number of variations. Being significantly wider and not as tall (from top flat to bottom flat) as a C motor, the "B" was a tight motor... so tight that some had radii milled into the interior top and bottom flats for a wee bit of extra clearance! 

The "B" was prone to running pretty warm, especially when loaded with heavy-artillery armatures (those guys were nuts... god bless 'em! :D ). The "C" sized "Green can" was a refinement of the "B", being taller and narrower, and had better clearance and "breathing".  The endbell hardware (especially the hoods) on the "B" and "C" are pretty much interchangeable, although the bottom plates on the "B" are wider because of the short/fat dimensions of the "B".  

While the "Green Can" magnets are interchangeable with modern "C" motor magnets height-wise, the "Green can magnets" are longer. Since the right magnets are getting scarce, a lot of people will just install modern C-can magnets, which is fine and all, but can change armature "centering". Modern C-can endbells will also fit the "Green Can", so that's another way to tell. Modern C motors are a bit shorter, in both the endbell and (I think) the can, but you can usually fit a modern C armature in the Green can by sliding the magnets around and using spacers.

That's pretty much all I can think of. The experts here (of course Philippe, Tony, and Rick T) probably have more info!
 
-john
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#8 havlicek

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Posted 01 March 2016 - 08:07 AM

... back on this build. The motor was spoken-for pretty much right after I posted the thread, and I was told to don't spare any expense. Now... that doesn't mean I'll be looking for diamond-encrusted elephant ears, but I'll do whatever I can to include all "the goodies."
 
-john
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#9 n.elmholt

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Posted 01 March 2016 - 07:25 PM

Hi John,

 

Inspired by your build, I was looking through my stuff in search for a Green can, but only one can met the criteria of being able to receive a modern endbell.

This can is also higher (17mm) than the usual C-can (16mm) - but this one is SHORT!!

 

WP_20160302_001.jpg

 

The picture is not perfect as you cant see the actual difference in length between the "mystery" can and the red standard C-can, but the "mystery" can has a total length of 22.5mm compared to the red can that has a length of 24.2mm 

 

So this is not a Green can - but what is it ?? - I remember vaguely that Philippe has mentioned shortened cans for 1/32 cars in 1969 (?)  - could it be one of those ??

 

Niels 


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#10 Bill from NH

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Posted 01 March 2016 - 08:14 PM

The width of the mystery can's endplate tells me it's a shortened "A" can of some type. It could be one of those mentioned by Philippe, but I don't have any of those for comparison. Is that a modern Parma endbell on it?

 

In the late '90s the Parma brush hoods on those were too big for a 36D motor brush. The later Parma 16D motors had hardware that was better fitting.


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#11 n.elmholt

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Posted 01 March 2016 - 09:05 PM

I think this is a newer Parma endbell - it's similar to the horrible green Parma endbell, but a bit thicker.
 
Niels

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#12 havlicek

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Posted 01 March 2016 - 09:24 PM

Could be a Mura "Magnum"... another Mura two-hole can, that I "think" fit a D-sized endbell, which is what you have on there.  

I believe the "Magnum" used some goofy soft magnets that pretty much fell apart if you looked at them cross-eyed. Using a modern "D" endbell would be a good way to cobble together a "frankenmotor", asnd in my view... entirely in the spirit of what racers did.   :D
 
-john
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#13 team burrito

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Posted 01 March 2016 - 09:30 PM

... back on this build. The motor was spoken-for pretty much right after I posted the thread, and I was told to don't spare any expense. Now... that doesn't mean I'll be looking for diamond-encrusted elephant ears, but I'll do whatever I can to include all "the goodies."


I have a pair of elephant ears, if you need them.
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#14 Marty N

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Posted 02 March 2016 - 12:48 AM

.835" is the ID of the Green can. I certainly haven't tried them all but seems more modern "C" cans are .840" save the one oddball Pro Slot .860" Drag can.

At any rate most C bells fit the Mura Green. I wonder if that is a hold over from the original C specs? Why make a new mold for a .005" change in OD? These bells are even "standard" on the .860" variant.
 
Anyway. Love the 26t/26. Pretty arm... as always.
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#15 havlicek

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Posted 02 March 2016 - 08:24 AM

Yeah, Marty, and even the Mura endbells are a very snug fit on the Green Can.

 Also, and to confuse matters even more, the Green Can metal is somewhat thicker than typical modern C-cans. Since modern magnets will fit, these discrepencies are all "in the ballpark" in machinst terms (a few thousandths here or there. In carpenters' terms (a 1/32" here or there)... they're "the same".   :)
 
-john
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#16 Guy Spaulding

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Posted 02 March 2016 - 10:39 AM

The Green Can was very conducive to modifications when USRA allowed cutting and only required that the overall dimensions remain original.

You couldn't do this with a "new breed" can. :dash2:

Grp15 motor.JPG
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#17 TSR

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Posted 02 March 2016 - 08:39 PM

The Mura C can and D can can easily be mixed up, but here are a few pics to clearly distinguish them. These are all D size, their overall dimensions identical to those of a Mabuchi FT16 or a Parma 16D motor:

mura_d_size.jpg

D-can on left, smaller C-can on right. The difference in size is that of the thickness of the Mura D size magnet shim.

bulk 1998.jpg

And side view:

bulk 1997.jpg

The B-can is basically a squashed D-can, but is also a bit wider. It is also lower than a C-can.

1167.jpg

When Mura made their "Magnum 88" magnets for their Mabuchi FT16D motors, they needed a shim to fit tight. Hence these "Semi Can" shims slipped inside the outer housing. They also found their way inside the "Magnum 1000" can, a D size can made by Mura in 1968 from modified tooling owned by Tradeship.

mura-story-18 (2).jpg

A "B" endbell (left) is wider than a "D" endbell (right). This "D" endbell is the copy of the Mabuchi made by Tradeship with the Champion-style pent-roof brush holders later copied by Mura.

bulk 953.jpg

I hope that this helps.
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#18 Marty N

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Posted 02 March 2016 - 10:09 PM

Somebody needs to start making this can again. :yes3: 


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#19 Roger Schmitt

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Posted 02 March 2016 - 10:56 PM

How many do you want?

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#20 Samiam

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Posted 02 March 2016 - 11:07 PM

Whatayah got?


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#21 olescratch

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Posted 02 March 2016 - 11:56 PM

I'd like to know the answer to that question also!!!
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#22 havlicek

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Posted 03 March 2016 - 06:45 AM

I have a pair of elephant ears, if you need them.

 
Hi Russ.  

Thanks very much! I do have a set or two here... so hang on to them, there aren't many of those left either.


The above post by Philippe is of course... wonderful!
 
-john
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#23 Samiam

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Posted 03 March 2016 - 07:05 AM

A nice set of E-ears are getting hard to find. If we show a demand maybe Rick B will look into re-popping them along with buss bars?
Sam Levitch
 
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#24 TSR

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Posted 03 March 2016 - 02:02 PM

There were several styles of "Elephant Ears", some overhead, some with only one overhead with the other on front of the motor.

There were quite a few companies which marketed these, should not be to difficult to find.

Philippe de Lespinay


#25 Samiam

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Posted 03 March 2016 - 02:36 PM

I'm referring to Mura's Elephant Ears. There were other heat sinks by a myriad of makers. But the unique look of those huge Mura EEs defined the era I started racing. Built Mura C-cans, tagged arms, Red Dot magnets, production brass n' wire chassis, and orange tires.

 

And the entire raceway reeked of oil of wintergreen and burnt epoxy. :)


Sam Levitch
 
"If you have integrity, nothing else matters, and if you do not have integrity, nothing else matters."
    Robert Mueller, special counsel (2013)
 
"... because people have got to know whether or not their president is a crook."
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"Fool me once, same on... shame on you. Fool me... you can't get fooled again."
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