3573 replies to this topic

[havlicek]

I haven't done a Mura in a while, and I had a particularly clean old pink Mura that was just begging for attention Sometimes, rather than go for the bling, a motor is clean enough that leaving it with some "patina" seems like the "right" thing to do...this motor was such a case. This motor is also a good example that, with a little luck, you can find motors that really need very little work to take them from being an old-but-interesting slug to strong performers. The Mura stuff generally was made from excellent quality parts...and swapping out the arm can result in a real performer!



The motor had little evidence of ever having been run. The endbell was clean and the screw holes showed no sign it had ever been mounted in a chassis. The lead wire tabs had no solder on them and there was virtually no brush track on the com...just some discoloration from when I gave it a spin and maybe the previous owner. Upon removal of those stooopid pin tabs or whatever they were called, this is what I found:



You get a very nice Mura .007" lam arm with their nice thick insulation coating, a great com and a nice straight shaft. Magnets measured nice and strong (between 1100 and 1200 or so on my meter) so I didn't even zap them! Even the magnet position in the can confirmed that centering the arm in the field was going to be a piece of cake. The stock wind turned out to be 50T/#29awg and while that would be a comfortable wind as far as reliability...it sure wasn't inspiring, even with the healthy advance pf the com. So it was time to strip the arm and head off into rewinding land



The naked truth above shows just how nice the arms in these old Muras were. No matter what the actual wind was, you got the "good stuff". Anyway, since Mura had already sorted out most of the major flaws of the Mabuchis by this time (endbell material and hardware, larger "36D" sized brushes, magnets, arm, com etc.) and there being a lot more potential performance-wise in the setup (although these motors could tend to run warm)...I decided on a #27 wind as a significant step (or steps!) up from stock, but still not a "hot lap special" .



It's not the neatest wind, but metering it...it's .175 ohms (exactly!) per pole, which should put it solidly into "pretty-danged-zippy" territory! Keeping in mind that I planned on using the stock setup with no more mods, I figure that's about as close to "race motor" as I should go! Since the basic Mura motor was already good to go, all that was needed was to reassemble the thing. I didn't even polish the endbell hardware...just made sure the hoods were aligned. The air-gap was suitably tight and the bushings had almost no wear. Spinning it up, the motor was a completely different animal than it had been...LOTS of revs and torque on hand.



The motor could easily be taken further into "race territory" with the usual additional doo-dads for longevity and maybe some more RPMs, but I like the fact that it has retained ALL of it's original DNA. Whoever winds up getting it, could stick this thing in a period-chassis just as-is and have a bunch-o-tire-spinning-fun...OR...add more race-goodies. Until it gets "the call", it will stay just like it is and I really hope it doesn't get "upgraded" at all Amazing how far Mura lept ahead in just a couple of years...and this was just the beginning!

-john

[Pablo]

I just never get tired of this stuff
Wait til Ken Botts sees it, he's gonna flip out !

[havlicek]

Thanks Pablo

-john

[One_Track_Mind]

Hi John
Great job on this little jewel!
And NO! I never put any power to this motor or mounted it to a chassis.

[havlicek]

Ack Brian...I get so much stuff from people as trades or even gifts, I sort it and then tend to forget where it came from! Tell you what, before anyone asks for it, check your PMs

-john

PS...next up a BIG WIRE Mura...just because.

[One_Track_Mind]

Sounds like this PINK will be coming back to OHIO!

[Alchemist]

Hi John,

I know I'm as fond of the vintage Mura motors as you are. Through your experience rewinding some of the newer motors like the SCX, Falcon, TSRF, JK Hawk etc., do you feel any of them have comparable quality arms and comm's like the vintage Mura stuff? Just curious.

Thank you John!

Ernie

I'm looking forward to the "Big Wire" Mura - oh yeahhhhhhhh!! "Just because" is a good enough excuse to me - LOL!!!

[havlicek]

I know I'm as fond of the vintage Mura motors as you are. Through your experience rewinding some of the newer motors like the SCX, Falcon, TSRF, JK Hawk etc., do you feel any of them have comparable quality arms and comm's like the vintage Mura stuff? Just curious.

Hi Ernie.

That's really an "apples and oranges" kind of comparison. The modern mini motors are disposeable and have been made purposely NOT to be reused after they've been "used-up". As such, it would surprising to find such high quality stuff in them. Even so, they offer some pretty serious performance at a pretty amazingly low price point. Thanks to very small and strong magnets, metal endbell (or no endbell at all depending on how you want to look at it), and modern manufacturing techniques, modern racers looking for good cheap fun have all kinds of options. The crazy thing is, there are good parts that can be salvaged from these motors even though they have been designed to be used and tossed...mostly the can and magnets. The arms and coms "could" be used for rewinding, though they're not worth the effort and even so, once you remove them from the motor to rewind...what motor would you put them back in? You would have to build something for the arm to fit which would be more effort than any possible reward.

The Mura stuff was really all "top-shelf". The motors were made to opened and refurbished. The end bells were made from an excellent heat resistant and tough material, with the hardware replaceable. alignable and easily modified. The magnets were strong although heavy as was the can. The arms were really great and even their low end stuff had the same great stacks and coms. There really is no way to fairly compare the two types, but that's because they were designed with two completely different objectives.

-john

[Prof. Fate]

Hi

You may remember a while ago when the HAWK 7 came out, there was a lot of complaint about the things blowing. And I bought a couple for the flexi racing. The conventional wisdom of the time was that they were inferior to the high buck 16ds used in one class, and the Falcon 7s in another, thus, I made a deal. I wanted to do a "death test" on these motors.

I got 16 hard hours out of one, before it just "lost a step". The second one was nicknamed "the zombie" because it just would not die. I got over a dozen good races out of it AND another 24 hours of play time running.

On a cheap motor.

Back in the day, with those high quality Mura stuff, I NEVER assumed any motor I build was going to give me more than 2 races or a race and an hour of practice.

Fate

[Pablo]

Very cool, Rocky.

What gearing/wheel OD's did you use ?

[havlicek]

I got 16 hard hours out of one, before it just "lost a step". The second one was nicknamed "the zombie" because it just would not die. I got over a dozen good races out of it AND another 24 hours of play time running.

On a cheap motor.

Back in the day, with those high quality Mura stuff, I NEVER assumed any motor I build was going to give me more than 2 races or a race and an hour of practice.

There is no meaningful comparison there, so I don't get the point. The Mura race motors "back in the day" would have been hot winds pushing heavy cars. The modern mini motors are good performers... though people specifically don't want them to go any faster in many cases. I would hazard a guess that modern C-can and strap racers still don't get more than a race or so out of their motors without a tear down...and they're still of a much higher quality than the minis.

-john

[Prof. Fate]

Hi

I was just ruminating about the costs and quality and the things we take for granted today.

In the 60s, stock out of the box $2.50 mabuchi wasn't considered a "throw away" either, but we still assumed that they would not live more than a couple races even in piano wire lightweights. So, these cheap chinese bits amaze me.

The JK flexi 25, 4:1 with 760s for the Kingleman.

[havlicek]

Oh...gotcha Rocky. They do represent an awfully appealing value, even though I have a hard time with anything that has been designed to be discarded. It seems that more and more "stuff" we use has been designed with that in mind with computers being one huge example. For a long time now, people have gotten used to spending a grand on a computer (or more!) and tossing it in three years (or less!). Throwing out motors with rare earth magnets, copper and whatever else just doesn't sit right with me. Then again, there's no such thing as a "TV repair shop" anymore either...or even small appliance repair shops.

-john

[don.siegel]

Yes there is John - well, there used to be... when we moved into our new apartment 8 years ago, a shop in the neighborhood the local shoe-repair/key shop also did electronics repair, and in fact did an excellent job on a broken VCR of ours... But when we asked a year or two ago about a TV problem, the woman explained that they had dropped the electronics repair stuff, because there just wasn't the demand anymore, certainly not enough to make stocking the parts worthwhile... In fact, shoe repairs are also falling by the wayside, since few people resole their shoes anymore (including me - haven't worn leather-soled shoes in years!).

Must admit I'm with you on the folly of our throw-away society, and don't get me started on printers and ink...

Actually, I'm not sure that the original Mabuchi motors, at $2.50 or $3 apiece, were really intended to be repaired and/or refurbished, and I'm sure Mr. Mabuchi never expected his motors to become the hop-up medium of choice for thousands of crazy teenagers!

Don

[havlicek]

Hi Don,

I couldn't agree with you more. Regarding the Mabuchis...I doubt very much that they were designed to be repaired and/or hotrodded as well. After all, that would be hurting their bottom line as people would buy less motors. Then again, I also doubt that a primary consideration with toasters was ever making sure they could easily be repaired. I mean after all, who ever went shopping for a blender and didn't buy one because they thought it would be difficult to repair? The difference here is that the mini motors have been purposely designed not to be repaired, it's a matter of degree as opposed to the older motors (and other modern motors) being designed so as not to prevent repair/refurbishing. The Muras on the other hand...whether by chance or by intention were designed in such a way that they encouraged people to open them up and have at it. The one exception is those darned pin tabs

-john

[don.siegel]

... and that's what old nail-clippers were designed for!

Don

[zipper]

I used wire cutters with sharpened jaws - still use them to remove tight sitting body pins.

[boxerdog]

I read once that there is a personality type that is referred to as "preservationist", and I guess a lot of us fall into this category. I just think a motor should have replaceable brushes, comms that can be restored, a solid endbell and parts available. I hadn't really considered the environmental side of tossing all of these Falcons in the dumpster, but it's certainly something to consider as well.

The Mura platform kept things interesting for a long time...other than the pin tabs or rivets or whatever. We all cut up these cans looking for the perfect shape and plugged in dozens of arms from many talented winders. It was and is a great piece of slot car history.

[Prof. Fate]

Hi

Well, you remember the story from a decade ago by Larry and I about "cheetah on steriods". This HAWK story has me looking at the boxes. I THINK I have an old "Pcan-Xcan" endbell that might pop in, and make it rebuildable. It cannot use the original arm anyway, I am just toying with the idea of a super light can with neos and, perhaps an X12 arm for another "frankenmotor".

I do have the parts and the technology!

Fate

[havlicek]

I had been aiming at getting a "big wire" Mura together (another just for the heck of it motor for no one in particular), so I started the arm yesterday and finished it off a little while ago. When I had mentioned "big wire", I should have said..."really big wire" because I dun dooed a #23:



Wind is 17T / #23 awg and resistance is way down in stoopid land...pretty much a dead-short, within oh say .030 ohms of a nuthin Blank is by Bill Bugenis with a drill blank shaft, as is the com. I did a little experiment on this one I've been wanting to try for a while. Instead of drilling it to static balance it, I polished the individual pole faces. It's not the most efficient way to do things as it took a while to do...carefully! I don't know that it is better or worse than drilling, but it did work surprisingly and is an option when there's not much meat to drill into without worrying about weakening the arm.

I have a nice Mura setup I did a while ago and bagged for just such an occasion, so this thing should be a real fire-breather. I just have to open up the end bell hardware a little for shunts and spring insulation, but I'm considering sending this one out for dynamic balancing because it's such a scary arm.

-john

[Pablo]

I polished the individual pole faces

Do you mean you removed material from the outer faces of the stacks ?
If so, wouldn't that mean the airgap on some poles is less or more than the others ?
Would that do strange things to the airflow and/or mag field ?

[Don Weaver]

John,

Either you're going to have to start racing G7's or AA/FC drag cars !

Don Weaver

[havlicek]

Hi Guys,

Pablo:

If so, wouldn't that mean the airgap on some poles is less or more than the others ?
Would that do strange things to the airflow and/or mag field ?

Maybe. In truth, the arm was close to balanced as-is as the coil patterns worked out pretty near perfect. I used a Scotchbrite pad in the Dremel to remove a little material from the pole faces...but maybe a thousandth or so. Of course, it's probably not balanced as it would be if done on a dynamic balancer...but it's pretty close You have to figure that arms that have big ol' holes on them must also have some sort of negative consequences to both the field and the airflow as well...not to mention the old ones that were ground-balanced and still seemed to run pretty well

Don:

...yep, this one should be interesting when it comes time to fire it up. I'll be wearing a Nomex suit and standing behind a blast shield

-john

[Pablo]

Hey Don W, put it in your retro F1 and scare the daylights out of people in practice......tell em it's the new Falcon 9
You could burn up the track with it

Thanks for the reply, John, makes sense.

[Victor Poulin]

John, that thing is gonna be one bad mother