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Best use for Mura Blue Dot magnets?


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#1 gc4895

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Posted 01 January 2017 - 12:47 PM

I was digging through my stuff today looking to build a stap can X12 motor to fit into a GT12 chassis. I came across these magnets and I don't recall the specific application I purchased these for.

 

What is the "highest and best" application these can be put towards? I don't want to epoxy and hone these in this strap if they aren't the best choice. Hey, experienced motor builders, what do you recommend for these? Also, what should I be looking for to use in this strap project?

 

If memory serves, I bought these magnets back 1998-99.

 

muraa.jpg


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#2 idare2bdul

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Posted 01 January 2017 - 01:08 PM

These are vintage magnets, among the best in the 1970s but today's magnets offer better performance. if you can define what class you want to race in and what type of track you are going to race on you can get better answers. The fact that they are matched probably indicates they were later production likely after George Mura sold the company.

 

If you just want to run them in a strap motor most of those were used for Group 12 arms. The most common way blue dots were installed was with the Mura clips and shimmed to the preferred air gap.

 

If you decide to sell these to get modern magnets let me know I would probably be interested in buying or trading. 


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#3 gc4895

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Posted 01 January 2017 - 01:25 PM

Class: 

Only rule is X12 armature. Installed any way your heart desires.

Any chassis (my choice is a GT12 due to availability, durability, cost). 

Any body, wing excluded.

Track: Swoopy blue King. 


Mark Bauer

#4 old & gray

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Posted 01 January 2017 - 01:34 PM

I seem to remember these magnets as ones I used in the mid to late '90s for Group 12 wing cars with full C-cans.

 

For your strap 12 - check the length of the magnets, with a .350" long arm stack these magnets may be too long for your can; you might look for some of the "International 15" magnets, they tend to be shorter, lower, and lighter which will help handling.


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#5 Bill from NH

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Posted 01 January 2017 - 03:54 PM

The vintage blue dots of the '70s were Champion Blue Dots. Champion issued them after the DZs, but before the White Dots. Some people say the only difference between DZs, Blue Dots, & White Dots is the colors of the paints used for making the dots. The Mura Blue Dots are a lot newer, as Bob said.

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#6 Danny Zona

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Posted 01 January 2017 - 06:21 PM

I bet the DZs are badass... ha-ha.
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#7 havlicek

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Posted 01 January 2017 - 07:17 PM

Pretty much the same uses (C-can) as the Mura Red Dots.  "Cryogenizing" (some sort of mystical treating with ultra cold something or other... liquid nitrogen?) was supposed to impart magic qualities to the magnets. These came about before Mura evaporated, but as far as I could tell, they weren't any better than Red Dots... but Red Dots were/are good magnets anyway.
 
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#8 Bill from NH

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Posted 01 January 2017 - 08:01 PM

I think the Mura red dots and blue dots came about during the time that the Californian fellow Woody owned the company. I never bought either because I had made a trade for some RJR arms and magnets.

Bill Fernald

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#9 havlicek

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Posted 02 January 2017 - 07:01 AM

What is the "highest and best" application these can be put towards?

 
This is really best answered by saying... wherever they fit and work. I'm sure there must be stronger ceramics around today, but stronger isn't always better. The "dance" between the arm and the magnets is one thing, but what a racer prefers in terms of performance so he/she can drive the car the way they like is another.  

 

The Mura Red Dots and Blue Dots were no doubt mostly used in full can-type motors, and they could work well all the way up to big wire arms, just as earlier longer magnets that were no stronger did. They sure worked well with tamer winds also, and have a modern thin tip, pretty much as thin as you could have and still use U-clips to install them.  

 

As to length, magnets had already gotten shorter before these were a thing and arms from .440" to .460" long were the target, but no doubt people also installed shorter arms in setups with these magnets and they probably worked just fine.  

I know also that, as the older longer magnets became scarcer (see Steve Okeefe's "Vintage-style" thread), these and other similar magnets were installed in Green cans and other similar early C-cans with longer (say .500"-ish long) arms. Would they "work"?, sure.  

 

For a strap motor using ceramics, best to say that, if the motor is sized for "C" type magnets and armatures, the Blue Dots would work fine for many winds, but with gauss down because of the "can" being mostly gone, it might be better to look at what current similarly-sized magnets are available that might be stronger. Then too, an even shorter magnet could save you a little weight if you're looking to shave a hundredth of a second off your lap times.  

 

Last, look at the thickness of the magnet and how easy it will be to get to your target hole. You can always hone a too-thick magnet, but shimming can be a PITA in a strap, although that's less likely to be necessary.  

 

That's all I got!
 
-john


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#10 Mike Patterson

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Posted 02 January 2017 - 10:46 PM

Some people say the only difference between DZs, Blue Dots, & White Dots is the colors of the paints used for making the dots.


Yep.

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#11 gc4895

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Posted 03 January 2017 - 09:56 AM

John,

Thank you for the thoughtful reply. 

The "cryo" era I lived through with rifle barrels. There was a period of time that treating the rifled barrel with liquid nitrogen was thought to relieve the stresses imparted to the steel through the machining/cutting lands and grooves (rifling) process. The common wisdom was the center of the group would not change as the barrel heated. I don't believe this process is regarded as relevant today. I can't imagine what was expected from magnets. 
 
I will measure these but I think these may be sort of like cars from the '80s. Smog gear and bumpers added on top of '70s technology. These magnets are a time warp to an interim period in ceramic magnet technology.
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Mark Bauer

#12 old & gray

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Posted 03 January 2017 - 10:41 AM

While the "cryo' portion of Mura magnets may have been as effective as soaking in snake oil, I found a number of the motors I built with Muras ran smooth and cool.

Interestingly, once completed, the Mura motors would frequently give a 12 "click" feel, as if the arm segments were attracted to the tips rather than the center of the magnet.
Bob Schlain

#13 havlicek

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Posted 03 January 2017 - 04:58 PM

The "cryo" era I lived through with rifle barrels. There was a period of time that treating the rifled barrel with liquid nitrogen was thought to relieve the stresses imparted to the steel through the machining/cutting lands and grooves (rifling) process. The common wisdom was the center of the group would not change as the barrel heated. I don't believe this process is regarded as relevant today. I can't imagine what was expected from magnets. 
 
I will measure these but I think these may be sort of like cars from the '80s. Smog gear and bumpers added on top of '70s technology. These magnets are a time warp to an interim period in ceramic magnet technology.

 
Hi Mark,
 
I don't remember for sure... but I think I measured the Blue Dots and Red Dots strength and the numbers were pretty much the same after zapping. I will say that i think they'd make for a fine motor with most winds up to and including #25 wire.  

While there may be stronger ceramics around today, otherwise "equal" motors with either Blue Dots or Red Dots against the current best ceramics would probably be close. Unless someone is looking for the Blue Dots for a particular reason, I wouldn't think they're old enough to have any collector value, so enjoy them... stick 'em in a motor and let 'er rip!
 
-john
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John Havlicek

#14 boxerdog

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Posted 03 January 2017 - 06:54 PM

I guess I am 20 years or more behind the times, because I still use red/blue dots for longer stack setups like contenders, S16C etc. when I find them.

 

Hadn't noticed them being slower than anything else, maybe a little heavier. The strongest magnet does not necessarily produce the best motor in all cases, just a guess.

 

dc


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#15 SlotStox#53

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Posted 03 January 2017 - 08:25 PM

Totally different setup but a long way back I shoved a Mura wasp armature in a standard Johnson 13UO/ mabuchi 13D with standard weak magnets and the motor was amazing :D

Made the airfix 1/32 mini with brass & wire chassis fly!!!

#16 havlicek

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Posted 03 January 2017 - 09:22 PM

 

 

Hadn't noticed them being slower than anything else, maybe a little heavier. The strongest magnet does not necessarily produce the best motor in all cases, just a guess.

 

 

...and that would be a "bingo!".  :D


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John Havlicek





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