47 replies to this topic

[Gator Bob]

Is this a "B" can?
Thick and heavy!

[Albert Bisaccia]

Bob,

Looks like a B can to me. If you need an endbell I'm sure I have them, I'm not sure if I have magnets but a friend of mine does.

Albert Bisaccia

[havlicek]

Yep... it's a "B" and a nice one at that... one of many variants.

-john

[TSR]

In mid-1969, Mura issued "milled" cans in an effort to reduce the magnetic effect of the low profile can on the armature (anyway that was the thinking). A new larger vent hole also became standard. Mura and Dart as well as Nutley and DB (Dave Bloom) marketed the same can.

It did not help and by then, Bob Green was already working on cutting down the 16D-size Mura can, fitting it directly over Arco magnets. This became the ticket a year later, and the B was history.

[Jairus]

I believe you meant to say "historic"!

[TSR]

Or hysteric...

The B was a giant technical failure for Mura, but is the darling of collectors today...

There are so many variations of this motor, there is a drawer full of them at the LASCM and I am still trying to reconcile the Mura catalogs with all the versions...

Mura was incredibly prolific as getting stuff out. The MPP series that followed the B fiasco is also amazing in itself.

[Gator Bob]

Help!

So,
The "A" can was a "D" size can?
All are two hole?

The "B" is a low profile "D"?
Both two hole and rectangular hole versions?

The "C" can is taller but shorter then the "B" or the "A" ?

"D" sized arms fit the "A" and "B"?

[zipper]

Had one of those in '70 with a green "bubble gum" Mura (S24) arm. What a hot thing!

Then, I thought the "circular milled" with two tiny holes came after that but it was here in Finland, everything was late. And just one arm is left from that old stuff.

[Jairus]

Bob,

The "B" is the shortest of all of them and the widest. The "C" is slightly taller than a "B" but about the same width as an "A". All can fit the same size arm if you use enough spacers because I have found the "C" to be a tighter space inside front to back.

[TSR]

The "C" is slightly taller than a "B" but about the same width as an "A".

"A" and "C" next to each other (see below)
Jairus, the C is quite narrower too... the "A" has to accommodate a thick steel shim on each side, the "C" does not.
The "C" is also shorter.

[Ron Hershman]

the "A" has to accommodate a thick steel shim on each side,

Technically... the A was not made to fit a shim... the shim was made after the magnets when from a thicker and taller dimension to a thinner and shorter dimension and the shim was created to move the magnets closer to the armature and take up the "space" between the top and bottom of the can in relation to the top and bottom of the magnets.

Then the C-can was made to fit the shorter height and thinner magnets without needing the shim.

[TSR]

the shim was made after the magnets when from a thicker and taller dimension to a thinner and shorter dimension

Ron,

I know what has been said before but at this time, we have zero evidence to prove the above, unless you have solid evidence to the contrary?

The very first issues of the Mura M400 series (the one with the olive-green can) have the shim. As far as I know (and please someone prove me wrong), all the early motors had the shim, all through 1968, then the second series in 1969. I have never seen any of these Mura motors, new or used, with such magnets. Even the weird Certus magnets need the shim. All, Mura 44 and 88, Tradeship, Certus, Dyna-Rewind... are pretty much the size of the Champion Arco and all need the full shim to fit in the Mura M400-series can.

The LAST issues of 1970, used in their RTR cars by Riggen, Dynamic, and Cobra/Phaze III, painted in medium metallic blue and with thinner magnets to clear the larger diameter (FT26-style) armatures, do not have the shim and the magnets touch top and bottom.

Six months before the Mura M400 motors came out, Mura had a series of Mabuchi rewinds using that very same shim (the whole of the 1967 summer in fact). This shim was also used by other rewinders. Dynamic sold the shim separately, with and without magnets. There are plenty of rewinds using this shim at the time, Lenz, U-Go, Chong... and at the same time, Dyna-Rewind also was using a top-bottom steel shim, and of course Champion had their one-piece job on all their FT16 and FT26 rewinds for the Arco magnets.

I believe that the "shim" was simply one of these things that rewinders used as a matter of fact and never even questioned it.

Let's not forget that Mura used the Fred Foyn, Tradeship can die to make theirs, and they did not have much of a choice about its overall size. Since their shim, designed for the Mabuchi motor, was already fitting nicely inside the new can, why would they even have investigated the need for new magnets since they already had the Magnum 88 right in stock?

(The B-can magnets are of course a whole different story).

[Gator Bob]

Dokk, when you say shim are you speaking of the "can in can" style or was there an additional shim/spacer behind the mags?

I dug out a used "A" can painted dark metallic blue but it has red and yellow mags and no shim of any kind, maybe "D" cans were swapped in.???

Also have a lime green, foil direction sticker, factory axle clearanced, small two hole "B" can with strong "click-ettey" (like ARCO) mags.

Two questions, were these motor specs defined buy can color? What color endbell and what wind was the lime canned motors?

The "B" has the lowest CoG, why did it bomb out?

It's like Mura soup with all the cans and endbells I have on hand.

[Ron Hershman]

Ron,

I know what has been said before but at this time, we have zero evidence to prove the above, unless you have solid evidence to the contrary?

All it takes is the parts and a set of calipers

The Mabuchi 16-D came out in 65 or 66?

The French can which became the Mura can should be the same inside dimensions as the Mabuchi 16-D can.

Take the magnets out of the early Mabuchi 16-D can and measure them.

You will find them to be a tad taller and thicker than the later magnets that were used in the "A" sized.

That simple

[Ron Hershman]

I dug out a used "A" can painted dark metallic blue but it has red and yellow mags and no shim of any kind, maybe "D" cans were swapped in.???



The "B" has the lowest CoG, why did it bomb out?

Maybe it has the early Mabuchi 16-D magnets in it They were thicker and taller.

Why did the "B" bomb out........ magnets plain and simple. The early version had "machined" magnets because Mura did not want to pay for the tooling and the machined magnets were not "radially oriented"..... this is bad.

After a year or so Mura started using "Versitec" magnets that they bought OEM which were "radially oriented".

This was better but still not the "fix"...... then the problem was in the arms and no one ever figured it out until it was years later

[TSR]

Dokk, when you say shim are you speaking of the "can in can" style or was there an additional shim/spacer behind the mags?

Yes, the "can in a can" as it was called.

I dug out a used "A" can painted dark metallic blue but it has red and yellow mags and no shim of any kind, maybe "D" cans were swapped in.???

That's the Group-12 motor I was talking about, came in 1970 to fit 26D-size armatures. The mags are much thinner, they would clear a "16D" arm by a mile.

The Mabuchi 16-D came out in 65 or 66?
The French can which became the Mura can should be the same inside dimensions as the Mabuchi 16-D can.
Take the magnets out of the early Mabuchi 16-D can and measure them.
You will find them to be a tad taller and thicker than the later magnets that were used in the "A" sized.
That simple

Ron,
Searching for truth here, not arguing for the sake of arguing.
OK, the stock Mabuchi magnets for the "16D" motor are of two types: the early magnets for both the FT16 (1963) and FT16D (1965) are the same and have a notch on their tops to allow the retainers stamped in one side of the can and a spring on the other side to do the job. But they were very weak.

The 1967 version of the FT16D with ball bearing and oval cooling hole had new magnets that appear to be identical to those used in the Igarashi "Hemi" motors, and are retained by inner sheet-metal springs, there are no more notches on one side of the can. But these were also very weak, while quite not badly. When Mura devised their "Magnum 44" magnets, these fitted the Mabuchi can but not quite well, and they are really "floating" in there, sometimes rubbing on the arm as they are off center.
The "Magnum 88" were stronger, but have the same problem. Both fit inside the "can in a can" full-contour shim, first used in these motors in the summer of 1967, at least 8 months before the new Mura "American" motors come out:



In 1968, when the Tradeship tooling was used, the shim fitted right in. The new Mura line came out in 1968, the very first motor being the M-444, and the WHOLE line that also includes the Cukras motors, has the shim.



In 1969, the upgraded motors (white endbell, tied comms on arms...) also have the shim. But the shim is much older than the Tradeship can... by at least 6 months.

Since I have all the necessary bits at hand, I will take precise measurements and report on my findings ASAP.

[TSR]

Maybe it has the early Mabuchi 16-D magnets in it They were thicker and taller.

No, they are very thin special mags for the big "26D" arms. I will take pics of all of these so that you can see the diff. I never did that in the past and maybe now is the time since the questions arise.

[Hworth08]

Then, I thought the "circular milled" with two tiny holes came after that but it was here in Finland, everything was late.

Could someone expand on the "circular milled" cans? I got a couple of these in the winter and had never seen one before.

[TSR]

Desperate attempt by Mura to do anything that could get that thing to work. The idea was to "reduce the magnetic field" as it is quoted in the period media.

[Gator Bob]

Dokk,
Love that 25 single with a 60 day warranty on a 60 minute (or less) motor. BTW: is that a one hole can?

Just noticed the Met. Blue can has mags painted red and yellow on both ends. An FT26 arm won't fit in this one, that would be cool as winter.

[TSR]

Dokk,
Love that 25 single with a 60 day warranty on a 60 minute (or less) motor. BTW: is that a one hole can?

No, Mura never had one like Champion did, because Mura never made a special order to Mabuchi.

Just noticed the Met. Blue can has mags painted red and yellow on both ends. An FT26 arm won't fit in this one, that would be cool as winter.

But the Mura Group-12 arm that is almost the same diameter, fits. When we say, a "26D" arm for these, it is because their Group-12 arm was much larger in diameter than the standard "16D" arms. I will have dimensions for you sometimes in the next 2 days.

[tonyp]

I hated having to run b cans when I raced for nutley. They were horrible. Almost never finished a 40 minute main, or at least never finished fast. I think the only one that ever won a race on the east coast was the time PVA won at nutley with the big brushes.

[Ron Hershman]

Ron,
Searching for truth here, not arguing for the sake of arguing.
OK, the stock Mabuchi magnets for the "16D" motor are of two types: the early magnets for both the FT16 (1963) and FT16D (1965) are the same and have a notch on their tops to allow the retainers stamped in one side of the can and a spring on the other side to do the job. But they were very weak.
...

Not arguing..... once upon a time I measured all this stuff.... the Mabuchi 16-D cans had/has the same inside dimensions as the Mura A can had/has. The endbells between the two interchange correct?

You forgot one Mabuchi magnet.... the one that had a single retaining clip that the magnets had notches in the center of the inside arc that the clip fit in and retained the magnets in place with the one clip and no clips at the top or bottom of the magnets once inside the can. No 26-D arm is fitting in that set-up as the mags are very thick.

Yes all of these original magnets were "weak" that's why stronger magnets were made and at thinner and lower dimensions.

[Ron Hershman]

I hated having to run b cans when I raced for nutley. They were horrible. Almost never finished a 40 minute main, or at least never finished fast. I think the only one that ever won a race on the east coast was the time PVA won at nutley with the big brushes.

Going from the little 16-D brushes to the 36-D brushes just made them burn up quicker......LOL

[Ron Hershman]

Could someone expand on the "circular milled" cans? I got a couple of these in the winter and had never seen one before.

There is two types of "milled' B Cans...... one you can see the "circular" pattern on the top and the bottom of the cans they did in one plunge by using a huge diameter tool. The other milled can was just "straight" milled with a smaller tool.

Then there is the B cans that were "honed" inside where you can see in the center of the can a circular pattern where they used a tool to thin the bottom and top of the can inside the can.... probably to give a bit more arm clearance.

Desperate attempt by Mura to do anything that could get that thing to work. The idea was to "reduce the magnetic field" as it is quoted in the period media.

They were going backwards and didn't know it at the time. B cans/sized motors could work today do to learning from the mistakes of the past.

The B can motors back then WERE NOT magnetically bound up.... the B can magnets both machined and radially oriented were weaker than the first C can magnets which when place in the first C cans and motors were more bound up than the B cans ever were.