9 replies to this topic

[Slot Car Rod]

I was telling Eric that I was running out of early Mura C can motors to restore.  He suggested I try some Mura B can motors.  He said they ran pretty good back then.  Here is a B can-powered car I restored.

 

I do not know who built this nicely built chassis.  The motor was cleaned up.  It was a little rusty.  The motor looks to have a 25 single machine wound armature.  The can is cut up.  Racers have told me the cut up can increases revs and reduces weight.  The motor draws lots of amps but runs cool.  The reputation with B can motors back then was they ran hot.  Eric's first question regarding this car was, does the motor run cool?

 

The car is run with modern black tires (not shown).  The car is easy to drive and handles well.  Power delivery is very linear, and power is equivalent to a NCC20-powered car.  The car responds faster in the turns than a Mura A can-powered car of the same period, in my opinion.

 

I used a McLaren Mk8B body that was lying around.  The body has the sloped tire opening line (behind the front tires) back to the rocker area and indentations for the high wing struts.  I did not follow the sloped fender lines with the Sharpie pen.  

 

 

The rear spoiler is from an Aguirre air control kit.  The Aguirre Lexan material is more flexible than Champion brand sheet Lexan.  

The front spoiler is made of Mylar.

 

 

3/32nd front axle and 1/8" rear axle.  I added the Associated-style wheels.

 

Brass tire dressing shield.  Original lead wires.

 

  

 

Front spoiler adjusted.

 

[Bill from NH]

Nice restoration Rod! It's a nice clean chassis build buy whoever built it. Nothing really jumps out at me about it other than the size of the motor box. It probably was built for A-can motors. I have a few B-can motor parts to build, but in the day, I never ran any. So I really have no experience with them, other than hearing they ran hot. Some racing friends did run them.

[NSwanberg]

What is with the bars soldered across the top side of the B-can at both ends? Some mysterious attempt to make these motors work?

[Tex]

What is with the bars soldered across the top side of the B-can at both ends? Some mysterious attempt to make these motors work?

that is odd..... maybe to maintain body clearance to aid in airflow into/through the motor(?)...

[old & gray]

What is with the bars soldered across the top side of the B-can at both ends? Some mysterious attempt to make these motors work?

 

In the later stages of the B Can the top and bottom of the can were milled down (20/40 were .020 top and bottom, .040 sides) maybe this was reinforcement for a very thinned down can. 

[Larry Labounty]

 

In the later stages of the B Can the top and bottom of the can were milled down (20/40 were .020 top and bottom, .040 sides) maybe this was reinforcement for a very thinned down can. 

Do remember the B can just not the time period they were out? Was it in 68 /69

[old & gray]

Do remember the B can just not the time period they were out? Was it in 68 /69

 

Early 1969, first were the two hole thick cans (.040) later the rectangular hole like this one. Early ones had the 16D brushes, later came the change to 36D brushes.

[Bill from NH]

The 2-hole cans were thicker than those with the rectangular cutouts, whether they were milled ir not. Some with rectangular cutouts were milled on the inside.

[dc-65x]

Nice restoration Rodney.    

 

Here's a bit of B-can info I put together in a thread 15 years ago:
 

Here are the 5 basic B-cans I am familiar with:
 
 
 

 
From left to right, the first version has .040" thick sheet metal, 2 small vent holes per side and one square hole near the comm:
 

 
The second version changes to one rectangular vent hole per side only. It still uses .040" thick material:
 

 
Now things get more interesting. The third version gets the top or the top and bottom milled down usually to .020" thickness:
 

 
Here's a comparison of the standard and "20/40" milled can showing the difference in height which is pretty dramatic:
 

 
The fourth and I guess final attempt at making a successful Pro motor was the "circular milled" can. It is also milled but to .030" top and bottom and goes back to 2 vent holes per side. Vents in the sides of the can for brush cooling were also added. They also added an axle clearance cutout and releaved some of the back of the can on one side for can drive applications. I think this version was the last ho-rah for the "B" in the Pro races:
 

 
The cool thing is the milling of a .560"+ diameter feature inside the can inline with the armature to increase clearance between it and the can:
 

 
The last version I have is what I call the "C-can of B-cans". It has a lot of features the famous Mura 2-hole C-can has. It's made of the same .030" thick material. It has the nice axle clearance cut out and the bearing support area on the back of the can is much smaller. I thinking this one might have been more of a "Group" motor like the NCC 20 this can came from:
 

 
Another big thing is the can is shortened quite a bit from the previous 4 versions .995" length to about .945". Here's how much shorter the final version (in the middle) is:
 
 
 
A disclaimer : This is just my small sampling of B-can evolution presented for entertainment only .

[Bill from NH]

The last version was used in the '70s for Mura's Group 15 motors with the pink cans. Those ran well without any heat issues. They were my weekly race motors from '70 to '76.