138 replies to this topic

[MSwiss]

Yeah, lots of cool info in that issue of MRJ.

Along with Howie and some of the other Pro's, some of the independent's from the Arco race, are still racing.

Dan D., now in Florida, and locally, Neal Isler is one the top hardbody racers at Chicagoland.

I also got a kick out of seeing Ray was still using a thumb controller.

Also, that Dave Bloom was called Designs by Dave.

I'll have to ride by that address one day, and see if the original house exists.

[dc-65x]

Yup Mike, that was such a cool issue I posted it all instead of just Howie's race report. Glad you guys enjoyed it.

 

Steve's been working on the motor box for the chassis and I've been working on the motor itself. Sandy Gross sent me this Cobra (Mura) 1-hole can, new in the package. Howie used a 2-hole can in the race but we think this period Korrect, Cobra can is the way to go:

 

 

Then this period Cobra RTR showed up on eBay and I saved the pictures. Check out the motor:

 

 

 

Whenever I can, I try NOT to open up rare sealed items. If I have to I will but this time I had a plan to make my own 2-hole can shown below. The Cobra can is for reference. I used a 2-hole Mura can, a piece of brass rod and nice fresh bearings:

 

 

First the endbell and can were drilled and taped for 0-80 pan head stainless steel machine screws:

 

 

Rather than using a clearance hole in the can I tap both the can and endbell at the same time. With the screw biting into the steel can it will be much harder to strip it, especially with fine machine screw threads. Also, the pin tabs that Mura originally used bit into both the can and endbell:

 

 

Fresh bearings were epoxied into both the can and endbell...........

 

 

.............clear 2-ton epoxy on the endbell...........

 

 

..............and JB Weld on the can bearing (note the motor mounting screw holes have been filled):

 

 

Even though the can bearing was a tight press fit, I could rock it slightly in the can. I used an armature size pin gage to align the bearings before the epoxy set up. I forgot to photograph the actual process so a different can and endbell are shown below for these photos:

 

 

Here's how much misalignment could be present:

 

 

Here's the can modified to 1-hole style and masked off ready for paint. One area of the can got tinned with solder and masked off where it will be soldered into the chassis:

 

 

I got super lucky with the paint color. This is virtually a perfect match:

 

 

Here's the finished can next to the original:

 

 

I'm pretty happy with the way it turned out:

 

 

 

Next up will be the "semi-can" and magnets...............

[Pablo]

[SlotStox#53]

Wow! Talk about lucky color match

What did you use to fill the 2nd hole Rick?

*edit* looks like you used the brass rod

[dc-65x]

I should have shown the process.............but I cut brass plugs and fitted them flush with the INSIDE of the can. They sat proud above the outer surface of the can and were soldered in with a healthy fillet of solder. Then I filed and sanded everything down flush. After priming, to my surprise, the seam disappeared.

[SlotStox#53]

It's like you leaded in the can/seam like in auto bodywork. Came out really well & those beefy Mura bearings look great!

[dc-65x]

Here are the components for the magnet setup. A .015" Mura "semi can shim" packaged by Dynamic, Versitec magnets and Certus top and bottom magnet shim spacers:

 

 

My "Big Dog" zapper made sure the magnets were fully charged:

 

 

The can, endbell and shim were all given witness marks so they could be reassembled in the same orientation. Then I used JB Weld to epoxy the magnets to the semi can shim. I was careful to avoid gluing those Certus shims in place. Once the epoxy had cured I slipped the shims out so I could use them to space the magnets on future builds:

 

 

After the magnets were honed I could slip out the now "one piece" semi can and magnets so the can could be painted:

 

 

Next up is the coming to grips with the hard to find Mura endbell........

[dc-65x]

Mura 16D (A-can) endbells are as rare as hen's teeth.....at least in like new condition.

 

The used ones have often had a soldering iron melted into them by inept attempts at lead wire installation. The plastic spring posts will melt even on the second generation "white" versions. They are also cut up, ground on, acid stained, have the screw holes stripped out and otherwise turned to junk.

 

The first version of Mura "unmeltable" endbell was a very dark grey color and the plastic that was used, well, melted! A short time later, Mura changed to a "white" color plastic with a higher melting point.

 

Some time after that Mura came out with another version with the screw in spring posts and sheet copper brush hoods we're used to seeing even to this day.

 

Here is a new REH assembled motor which used the later version endbell and a loose endbell that I acquired a decade or so ago. Unfortunately, these motors are now gone:

 

 

I'm going to use the loose endbell above but make it look more like the "plastic spring post" version as you'll seen in a comparison photo coming up.  It will also need a color change to black.

 

Here are the parts I'll be using, the new endbell and hardware, a fresh Mura bearing, stainless steel machine screw hardware (no self tapping junk), vintage Mabuchi brushes, Certus light brush springs and teflon tube brush spring insulation:

 

 

First up, all the screw holes are tapped 2-56..........

 

 

...........and the holes chamfered with a 1/8" carbide counter sink:

 

 

Whenever possible, I install a fresh bearing even on a dissembled new motor. In my admittedly limited experience, new motors had the bearings "line bored" (read hogged out) to make the armature spin freely with the factory installed (read out of alignment) bearings. The difference in "fit" between a fresh bearing and one removed from a "new" motor is pretty dramatic.

 

OK, next up it's time for the color change to black. My second attempt at dyeing vintage plastic parts. The first attempt failed. This time I have some instructions and I'm feeling lucky

 

 

Stay tuned............

[SlotStox#53]

Are you making sure Mrs. Rick is out of the house before dyeing plastic parts? Or do you have permission?

Shame you missed out on that listing for the 2 unmeltable endbells would of had a nice fresh one to work with .

[dc-65x]

Hi Paul,

 

Those 2 endbells went for REALLY big money on eBay. Weren't they close to $200?

[SlotStox#53]

Hi Paul,
 
Those 2 endbells went for REALLY big money on eBay. Weren't they close to $200?

Something crazy like that or there abouts Sooo not fair

Thought you'd be in with a good chance but last minute sniper saw to that!

[dc-65x]

SUCCESS! And I didn't even destroy the kitchen.

 

While the pot of dye was bubbling away I even threw in a couple of white guide flags. Everything turned out great. The funny color in the picture is just lighting weirdness. The parts are a deep black color:

 

 

My first test piece was an old endbell that had blotchy orange stains. It came out looking like new! I don't know yet if other colors of dye would restore old endbells but black sure does.

 

My technique for future projects will be:

 

First of all, forget foil lining the pot and the little strainer to hold parts. Use a simple piece of piano wire attached to the part.

 

1.  Pour dye into pot

2.  Heat dye until it bubbles

3.  Put in part

4.  Look at part every few minutes

5.  When part looks good rinse it off with water

 

DONE.......I love it.

 

 

 

[dc-65x]

Before assembling the endbell the stock brush hood on the left got squared up as shown on the right:

 

 

The brush spring retainer gets a "hooked" shape and the brush spring slot is opened up a bit and chamfered:

 

 

Most importantly, the screw and brass cup that act as a brush spring post need to be replaced with something that looks like the brass spring post protector used on the earlier version endbells. I lathe turned brass bar stock into a spring post that hides the screw:

 

 

I also found some little fiber washers in a Strombecker Hemi Rewind Motor Kit that fit under the spring post to insulate it from any current flow and thus any heat when used with Teflon brush spring insulation and shunt wires shown below:

 

 

The finished endbell:

 

 

 

Here's a comparison of what will be seen when the motor is installed in the car. Early endbell on the left and my hybred version on the right:

 

 

Now, where's that Sandy Gross Cobra armature.............

[dc-65x]

Time to finish off this motor............

 

The Certus .014" brush springs needed tweaking as shown on the right:

 

 

Shunt wires are from strands of modern lead wire:

 

 

The shunt wires can be tucked in nice and tight and don't have to stick out past the sides of the motor like rabbit ears:

 

 

The brush springs and spring posts are completely insulated from current. You can touch the power supply leads to the brush spring coils and the motor will not run:

 

 

Hopefully this will help keep the motor together. It still seems to run hot though.............

 

Here's the heart of the beast, a Cobra (Mura) 27-28 double wind from Sandy Gross:

 

 

She's a beauty and really sings on the power supply. I gave it one light "fuzz cut" on the comm lathe to clean up 50 years of corrosion:

 

 

Here's the finished motor:

 

 

 

 

Wheels and tires coming up.............

[SlotStox#53]

Looks like you just stepped out of the wayback with a motor fresh from Cobra

[dc-65x]

Thanks Paul. The motor is all NOS parts except for the "faux" one-hole can. This motor really does "sing" on the power supply.

 

I experimented with 3 similar but used arms in the same setup. I cleaned them, polished the shafts and trued the comms. They all suffered from vibration or "buzzing" at various RPMs. I hate to mess with the "look" of these vintage arms but I think it's time to break down and send them off for re-balancing for future builds.

 

Anywho, for wheels and tires I found some "re-purposed" REH fronts. They appear to be Weldun wheels with an unknown hard rubber front tires:

 

 

I'm also using some "mystery" rear wheels that look very similar to Weldun's and some "Crispy Critter" blue donuts. I cut off the inside flange and thinned down the front flange as shown on the wheel on the left:

 

 

Here's the finished product:

 

 

Okie Dokie, there's much more to come but for now, my work here is done..................

[SlotStox#53]

Crispy critter blue donuts!? They really were inventive with the names of slot car parts back in the day

With a bit of buffing those wheels really come to life .

[Howie Ursaner]

Wow , that motor looks like it just came out of the factory, only better. Really love watching this project come together. This one should be a good runner . 

[Steve Okeefe]

Bend on a Wire

 

Time to get the chassis started.  First will be the foundation of nearly every early anglewinder chassis; the motor box.

 

However, bending a precise motor box out of 1/16” piano wire depends on being able to bend piano wire precisely.  Let’s address that first.

 

One reason why it can be so difficult to locate bends exactly is something fabricators call “bend allowance”.  Bend allowance is the amount of wire required to go around the radius of the bend, which must be more than zero.  Even though it is a very small amount, it is subtracted from the length of the wire, so it shifts the bend inward, and off the bend mark.

 

You can see this yourself by bending a piece of scrap wire and measuring the result.  Take a straight piece of 1/16” piano wire and place two marks exactly one inch apart near the center of the length.  Now, bend the wire precisely at each mark, forming a “U” shape.  Tweak the legs parallel and measure the distance between them; you will find it is always slightly less than one inch.

 

If you bend several pieces of wire precisely and consistently, you will find it is always the same amount less than one inch, plus or minus a few thousandths.  That means you can determine the exact bend allowance and build it into your measurements when you place the bend mark.  It depends entirely on precision and consistency and that’s why it is so important to use a purpose-built wire bender and not just a heavy-duty pair of pliers.

 

Here are some photos of the wire bender I use:

 

The box – this is a “Z” Bender, marketed by Hangar 9.

 

The tool itself – long handle, high mechanical ratio pliers with massive jaws intended for bending hard wire.

 

The “stock” jaws – as the name implies, this will make a “Z” (double) bend in the wire and must be modified to make only one bend

 

The modified jaws – these have been shaped so I can bend up to .078” piano wire.

 

Now, on to developing the motor box for Howie’s chassis.  Two other things are needed to get the job done:

 

A Sharpie Ultra-Fine point marker and a good quality six inch straightedge rule with 1/32” graduations.

 

Like most builders, I use the R-Geo jig block and I am also partial to using my own mechanical drawings.  Here I’ve made a drawing of part of the R-Geo block in the same scale as the chassis drawing.

 

Superimposing a line set at 18 degrees, I look for the pin positions needed to duplicate it with my straightedge.  Looks like position 10 with a brass tube sleeve on the left and position 5.5 on the right.

 

Next I extract the motor box from the chassis drawing and place it on the R-Geo block drawing:

 

 

Seeing that the motor angle lines up, I calculate the left and right spacing and draw all these lines, in pencil, on my R-Geo block:

 

 

Going back to the drawing I calculate the distances between the bends, add in my known bend allowance, and I’m ready to start the iterative (aka trial-and-error) process of working out the final dimensions.  I’m looking for the “sweet spot” where everything fits comfortably within the lines.  I measure, mark and bend, measure mark and bend, etc.

 

Several iterations (about two hours) later:

 

 

Each one of these motor boxes is an experiment that didn’t produce the result I wanted, so I would tweak the dimensions and try again.  There are three tweakable and two fixed bends with four straight sections between them.  I’m sure that produces Umpty-Jump Gazzilion combinations. However, with each experiment I gained a better understanding of the geometry of this motor box and closed in on the dimension set that produce a motor box identical to the original.  Here’s one I like:

 

 

 Now, before I forget, I document all the dimensions.  As MythBuster Adam Savage once said: “Remember kids, the only difference between screwing-around and science is writing it down!”  Here’s the drawing set:

 

 

 

 

 

But… we’re not done yet.  This is a team effort and the other members have to be happy with the results.

 

Here’s the side gap I built in:

 

Looks like about .032” or so.

 

Here’s the end gap:

 

About the thickness of a piece of paper.

 

Here’s the knee bend position:

 

Right on the corner of the motor.

 

I sent these photos off to Rick for his input.  He asked for changes.  This is no problem now that I’ve got the geometry figured out.  I sat down and bent ONE additional motor box with modified dimensions calculated to produce what Rick was asking for.  Here are the results:

 

Slightly reduced side gap:

 

Only a few thousandths difference, hard to see, but note the rail is farther from the pencil line.

 

Increased end gap:

 

Rick wanted .015” or so; there you go, Rick.

 

Knee bend position moved slightly aft:

 

About .032” to accommodate adjustments in the motor position.

 

Rick’s happy, I’m happy, Howie’s happy.  As my daughter-in-law says, “Life is good”.

 

Motor boxes are not hard if you adopt a disciplined approach and have a good wire bender.  Write down what you discover and don’t forget the bend allowance. 

 

Next time I’ll install the motor bracket and brace, can-side brace and build up the center section.

[SlotStox#53]

Steve, thanks for showing the maths,science and trial & error that goes into motor box creation!

May have to invest in a pair of those wire bending pliers.

[Eddie Fleming]

Steve

 I ordered a set of those pliers today. 

Do you get a full 90 bend in .062 wire or do you tweek it after?

[Steve Okeefe]

Paul,

 

You're welcome

 

I too struggled with motor boxes (using the big pliers) same as most everyone else during the time period this chassis comes from.  Wow; if only we had easy access to these kind wire benders then...

 

 

Eddie,

 

Just a reminder, you will have to modify the "stock" pliers to make only one bend at a time.  It's very important that you shape the jaws as close to the photo as you can.

 

To answer your question; yes I can get more than 90 degrees.  That brings up another detail, and another word: "springback".

 

Apologies in advance if I'm explaining something you aready know about, I'm just expanding on my post.

 

Springback is where you bend a piece of sheet metal (or piano wire) to a certain desired angle, but when you release the bending pressure, the bend in the workpiece "springs back" a few degrees.  It's normal for this to happen.

 

When you bend any piece of metal, you're stretching the outside of the bend and compresssing the inside.  In hard wire (such as piano wire) it sets up tremendous stresses in the bend (explaining why it so hard to bend it in the first place) and the "springback" is the metal trying to relieve as much stress as possible.  If it didn't spring back a little it would likely fracture.

 

For a 90 degree bend, I normally bend a little past 90, let it spring back whatever it wants, then tweak to the final angle. 

 

One more thing - watch out for the "Gotcha" gremlin!

 

After I fabricate chassis parts out of piano wire, I usually tin them to protect them from rust (and as a bonus it makes soldering later on MUCH easier - it's worth the effort).  In the process of heating and cooling however, the bends will usually creep a little; so a 90 degree bend becomes 92 or 93 degrees.

 

It's just the wire trying to relieve more of the stress, and an easy task to tweak the bend back to 90, but if you forget to check, that beautiful motor box you made, that fit in the jig a few moments ago, now may not fit at all...

[SlotStox#53]

Tin the wire and watch out for the Gotcha gremlin, check

Had a few attempts with regular pliers and marking off my Ricks Jig with the lines you did in the Texas two rail thread

[Half Fast]

Orthodontists pliers will bend piano wire quite nicely as well. .062 is tough on your hands though.

 

Cheers

[Howie Ursaner]

This is some very intersting stuff.I love to see "the process"  that this project requires. Steve and Rick are true masters. I just laid out the metal, cut it  chopped it, cobbled it as fast as i possibly could, ran to the track and raced it. Then i cut it up to build the one for next week's race.lol