# Gilbert Erector set 1913 motor



## BGHansen

Been awhile since I’ve posted a reproduction Erector set part thread. Here’s one that took quite a bit of time and involved a number of different parts that go into an assembly: circa 1913 Erector set motor. Here are a few pictures of the finished product.


Reproduction assembled 1913 Erector set motor





And it runs on 6V!




First, the obligatory history lesson. . . A.C. Gilbert introduced the Erector set in 1913. The sets came in various sizes numbering from No. 0 up through No. 8.  Sets No. 4 – No. 8 included a “kit” to build an electric motor. The construction was a bit involved, so the factory offered to assemble the motor for $0.50 if the child sent the parts back to the New Haven factory.

Here’s a snippet from the 1913 manual showing the construction of the motor.







The Gilbert company sold over 30 million Erector sets during their history. Why reproduce a motor? Turns out the 1913 motor is extremely scarce, there are less than 10 known to exist.  The last original motor to show up on eBay surfaced in 2007 and sold for $3500! I threw one on eBay and here’s where it ended.






Naturally, a reproduction is not worth anywheres near an original. I took on the project more as a learning experience than anything. I bought a Tormach 1100 CNC mill in July, 2019 and made heavy use of it to make the parts that make up the motor assembly. I still haven’t learned any CAD/CAM packages (have access to both Solidworks and Unigraphics) and plug along with G-code. Fortunately, the parts in this motor are relatively simple to plot out with my Post drafting machine, programming was fairly easy.

If you look at most small DC motors, the field magnet and armature are generally made from stacks of steel plates. Lots simpler to stamp out a pattern and stack them for thickness. This motor had field core and armature made from solid iron castings.

I have lots of photos, so this will take a few posts.  First part is the field core casting. I’m one of the lucky few to own an original motor.  And “NO”, I didn’t pay $3500! I noticed what looked like the armature and field core castings in a non-descript pile of parts. I didn’t ask the seller for more photos which would potentially create some competition on the bidding. Instead, I took a chance and won it for $40. You can imagine my sh*t-eatin’ grin when the package arrived; Yup, won most of a 1913 motor!  From there I measured/traced the part and made up a couple of drawings.

The original field core was made from cast iron. I went with A36 for the reproduction. The rough block is 2” x 4” x 1” thick. The original was also investment cast with probably a wax pattern. As a result, there was no parting line down the center of the part and no draft in the pattern as it wasn’t removed from the ceramic mold.  I tried a couple of methods for making the part.

My first attempt was to run the pattern to 1.1” deep in a piece of A36 bar stock 2” x 4”. Then band saw off the part and clean up the opposite face to a 1” depth. I snapped a couple of ¼” deep end mills with DOC of around 0.080” on a full-width cut at a feed rate of 4 IPM. I wrote a pre-drill routine to knock in a series of ¼” holes so the end mill had some relief.

I ended up using either a ¼” rougher or ¼” 4-flute carbide end mill to a depth of 0.55”.  Did one side, flipped the part and ran a mirrored routine to cut the opposite side.


First side done



Flipped the part and aligned the edges using a passive probe and parallel



First op was drilling a hole for end mill clearance



Rough hog out the hole with a 3/8" roughing end mill



Routine complete on the back side.




My alignment between cuts was not perfect, generally got within 0.005”.  There was a little step where the opposite side routines met. The step was metal-finished with a 2” x 42” belt sander.

The original part was investment cast and had a stipple finish from post-casting sand or bead blasting. I tried simulating this with an impact hammer, but even at 15 psi was getting too deep of a dimple. I ended up going with a double-cut carbide burr in a Foredom grinder. It worked out pretty well, took me about 20 minutes to go over the part to add some radii on the edges and hit the flat surfaces for a simulated sand/bead blasted finish. Wish I had a bead blaster, that might have done a better job quicker.


Wore rubber gloves and a full helmet while doing the surface finishing.  Lots of little slivers flying!



Finished part after grinding the surface.  The burr did a pretty good job giving a cast-like appearance


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## markba633csi

Wow. That thing really jogs my memory. Even though my Erector set was 60s vintage.
At the age of about 9 I built a small motor out of tin cans that resembled that one.  I still remember the thrill when it first ran.
I still have it somewhere- I really should dig it out- I'm sure it still works
Bravo Bruce! 
-Mark
ps 848 $ for a repro? I should start building those LOL


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## BGHansen

This second post will cover the construction of the armature. Like the field core casting, this part was originally made from cast iron. Again, no draft or parting lines on the part as it was investment cast likely from a wax pattern. I used 1 ¼” diameter 1018 for this part.


Set up with the 4th axis




This part was a natural for the 4th axis on the Tormach. I cut a prototype out of a polyethylene round, then went to the 1018. I’ve got a tail stock for my 4th axis, but was worried about running into the live center. The part is 1” long by 1 ¼” diameter; at that diameter a stick-out of 3” from the chuck worked fine without a tail stock. My 1018 stock was in 10” lengths (eBay win); it dawned on me late in the project to cut them to 5”. Then stick out 3”, cut 2.5” of the pattern, flip the round 180 and cut the back side.


End view of the prototype



And cutting the real deal





Finished up 4th axis work.  Rod stock is 5" long, part is 1" so some lathe work ahead



As an aside, I learned some features of the Tormach regarding the 4th axis. I set up the 4th for alignment by chucking up a round and swept the surface moving in X. Tapped the round to get it trammed in much like tramming a vise. I also swept the top of the round (trammed the Z) which fortunately was spot on, so no shimming of the 4th axis base was required.

I found the center of the piece by touching the side with a Haimer 3-D taster and moved up/down for the max needle movement. Zero’d Z and Y, then moved to the opposite side in Y, moved to a Z of zero, and jogged Y until the Haimer was zero’d. Noted that Y location, moved above the round and moved Y to half-way between Zero and my opposite side mark.  Zero'd the Y at the center of the rod. Then jogged down in Z until the Haimer zero’d and reset Z at zero (my CNC routine was written with Z=0 at the surface of the round, not the center).

Well, I for some reason went to the SETTINGS tab on the Tormach and discovered there is a 4th axis centering routine built into the machine! I have a passive probe for finding the edges and surface of a part. All of those routines are in a tab called PROBE/ETS. The reasoning for Tormach putting the probing routine for the 4th axis in the SETTINGS tab instead of the PROBE tab escapes me, but at least I now know where it is.


PathPilot has a built in routine for finding the center of your stock when using the 4th axis




Faced, parted and drilled the 5/32” center axle hole on the lathe. Then off to the CNC Bridgeport to machine a relief on the ends of the armature.


Facing the blank



Parting



Facing the parted side and cutting to length



Center drilling and drilling the axle hole





Secondary op to the ends of the armature



Yeah, have a little bit of work in store. . .





Lastly, did some surface finishing with a Foredom grinder. The original part was investment cast and post-casting sand or bead blasted leaving the finished part with a rough surface. A double-cut burr did a pretty nice job adding some radii and mucking up of the surface for a bead blasted finish.


Roughed up the surface for a bead blasted like finish and added some radii



Part prior to grinding on the left, finished part on the right


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## Braeden P

wow thats alot for a motor maybe start making and selling more?


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## BGHansen

Third part was the armature support/bearing brackets. These were originally made from 0.050” CRS and nickel-plated. I opted for 303 stainless steel in a No. 10 finish instead. The stainless in a No. 10 finish looks very close to nickel-plated steel and saves me from having to plate the parts.

I started this part by making a holding fixture for the Tormach. My plan was to make the part in three operations. First one would drill holes in the blank. Second operation cut the part to shape. The third operation drilled the hole for the armature shaft.


Spotting, drilling and tapping holes for the 3 operations in an aluminum holding fixture





Milling a pocket to capture the blank



Drilled and tapped holes for a "back stop" to locate the bracket by the base so the armature axle hole location was the correct height relative to the base






The part has its base bent to a 90 for screwing to a wooden-block base. I was worried about pre-drilling the hole for the armature shaft, then folding the flange for the base off a few thousandths and end up with a vertical alignment problem.  I opted for drilling the armature shaft hole after the base flange was bent so that surface could be used as the locator for the hole.


First op, drill holes and mill a clearance hole (no function, but the larger hole is in the original part)





Clamped the blank in place for the 2nd op which was cutting the profile



Bend the base



3rd op:  Bolt the blank to the fixture using the base as the locator for height and drill the armature axle hole







Next is the wooden base. The part originally had prick-punched holes to mark the screw locations for the various components. Another natural job for the CNC. The base was originally Cherry or Chestnut. I didn’t show the operations, but planed and cut blanks to size. A 30 deg. carbide engraver was used for the prick punching.


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## BGHansen

Next parts were similar, so both are described here. First, the armature commutator which had 3 brass contacts screwed to either a plastic or wooden cylinder. The OD was ½” so I started with some ½” brass tubing from Graingers. I took an oak dowel and turned it down to a slip fit into the tubing. Then epoxied the dowel into the tubing.


Turned the 1/2" dowel between centers to accept a piece of 1/2" OD brass tubing




Mounted the brass tubing in a 5C collet held in a hex collet block and carefully cut through the brass along the axis. Rotated the collet block two flats and repeated.


Slitting the contacts for the commutator





The screws connecting the armature wiring to the plates were tiny #2 wood screws. I drilled a line of #53 holes through the brass and half-way through the dowel. Again, rotated and repeated on the other 2 faces. Then went to the drill press and drilled the brass alone with a #43 clearance drill so the screws would slip through the brass and thread into the dowel.



Drilling the armature wire attaching screw holes






Sometimes better to be lucky than good. . . My ½” drill collar naturally slid over the brass, but it was also the same ½” length as the original commutator. Next step was to slip the drill collar over the brass/dowel and band saw a “chunk” off. Used a 2” x 42” belt sander to sand it to ½” in length.






Chucked up the ½” drill collar in the lathe and center drilled and drilled a 5/32” central hole for the axle. I left about 1/16” of the brass tubing setting outside of the collar on purpose. The dowel was ½” long, but the contacts were 7/16” long. The extended dowel is the insulator for the commutator as it sets up against the armature support brackets made above. They could have used a fiber washer to isolate the commutator, but went this route instead.


Center drilling the commutator while mounted in the drill stop



Drilling the 5/32" axle hole



Left a 1/16" of the commutator contacts out of the bushing for filing








I couldn’t find the #2 x 1/8” wood screws required, so made a little fixture to hold the ¼” ones I did find and sanded them to length. I pre-threaded the dowel holes with a full screw, so the sanded ones are screwing into pre-threaded holes. I can see silver-soldering or somehow permanently attaching a #2 screw to a screwdriver in my future. There’s just not a lot to grab onto with a #2 x ¼” screw.  It'd be nice to have a tap of sort for pre-threading the #2 holes.


Drilling a #43 clearance hole through the brass for the #2 screw



Finished commutator




The other similar part is the motor switch. It was the same sized diameter dowel or plastic cylinder as the commutator, but only used 2 of the brass contacts spaced on opposite sides. Pretty much the same process here as with the commutator.  In fact, the contacts were made from commutator contacts. I used a square collet block to hold the dowel and drilled a through hole for the contact screws and a half-through hole for the finish nail used as a switch handle.


Motor switches.  They use two of the commutator contacts and a finish nail for the switch handle




If the market supports more than 20 of these motors, I’ll make a couple of hardened drill bushings for the holes. It’d be a lot quicker to slip a collar over the tubing/dowel assembly and hand drill the #53 holes.


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## BGHansen

The commutator and switch brushes rub up against contacts made from brass. They are pretty simple to make with a shear and corner notcher. The majority of time was in the layout work. So, another natural for the CNC. My routines use a spring-loaded diamond engraver to scratch in the pattern. The brass blank was held to an aluminum base with double-sided carpet tape. I’m still a strictly G-code guy which worked well for these routines. I plug the length and width of the blank into the routine and hit START. The routine calculates the number of parts it can fit in the X and rows in the Y based on the blank size.



Let the CNC do the scribing of the contacts for the switch and commutator brushes.  Also spotted the screw holes for punching by hand.







I made the prototypes by doing the cutting to size first, then punched the screw holes for attaching the contacts to the wooden block. I found it much easier to do all of the punching with the blanks still together.









I used a corner notcher and Roper Whitney #218 punch press to do the appropriate trimming to size. The commutator brushes were bent by hand using a pliers. I lucked out a bit on the switch contacts as they could be gang-bent on the DiAcro brake and hand cut after the fact.


Cutting the commutator brushes



Bent the base flange by hand




Used a 1/2" square punch on the Roper Whitney to cut to the scribed line



Top row ready for shearing from the balance of blanks



Four rows ready for bending



Gang-bent the tabs on the DiAcro brake





Hand-cut to separate the parts


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## BGHansen

The motor had a ½” diameter pulley which was done on the lathe. Chucked up a ½” round, center drilled, and drilled the 5/32” axle hole. I used a DCMT (think that’s the bit) to cut the groove. I started to part the pulley before cutting the “V” groove so the width was marked. The pulley is 0.20” wide, lots easier to eyeball the “V” in the center with the width marked on the ½” round. Parted the pulley after the “V” was cut. Then a little clean up of the parted end with a 2” x 42” belt sander.


Center drilling and drilling the 5/32" axle hole





Pre-parting to mark the length of the part



Cutting in the "V" groove



Parting



And a few finished parts





I didn’t show it, but the commutator was pre-assembled to the armature shaft.  I center punched the 5/32” axle at the center of the commutator location for some friction and pressed the commutator on the shaft. Used a drop of polyurethane glue for belt and suspenders.

The armature and pulley were pressed onto the axle shaft. I didn’t show it, but used a ball peen hammer to slightly peen over the holes on one side of each part so they’d have some interference to the shaft.

The field core was originally wrapped with 20-gauge cotton-covered enamel wire. I found some on eBay and pulled out an appropriate length for the “kit” version of the motors. Same for the armature wiring which was 26-gauge. My manual dexterity isn’t the greatest for winding these things. I’m thinking about making up a spool/vise similar to what’s used to tie flies. Or, just offer a kit only.


All of the component for the motor




I can’t complain about what my first one sold for on eBay. In fact, the buyer took two (I offered an assembled motor and a kit). The next two bidders accepted offers also. Looks like I’ll be out making more parts. . .

Thanks for looking,

Bruce


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## Winegrower

Looks like your first unit was underpriced!   Really a cool and clever project.  

I remember the first motor I made, with wire wrapped nails...it was just magical when it actually worked.


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## BGHansen

Braeden P said:


> wow thats alot for a motor maybe start making and selling more?


Yup and yup.  First one on eBay sold for $848 which after eBay/PayPal fees netted around $735.  I offered two versions:  One assembled and one as a kit like it was originally sold.  The winning bidder took both.  I made offers to the number 2 and Number 3 bidders also which were accepted.  Up to around $2800 in profit at this point, so I'm up to about minimum wage in time spent on this project.  I figure the World-wide demand is for maybe 20, am working toward that number.  I've got 6 completed ones ready to go after yesterday's sales.  Trying to strike while the iron's still hot.

Bruce


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## francist

Nice work as usual, Bruce. I was especially intrigued to see your method for imitating the sand cast surface. I’ve been down that road many times too with varying degrees of success, but your results look great from here. Great job. 

-frank


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## markba633csi

I wonder what type of person buys it? Probably older, wealthy, had one as a kid.  Sentimental value, that sort of thing
I sometimes see stuff on Ebay I had as a kid and think about buying it, but then I go "the past is past, I've moved on"
One can purchase objects from the past but you can't recreate that time and place- those moments in time and life
-Mark


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## BGHansen

Winegrower said:


> Looks like your first unit was underpriced!   Really a cool and clever project.
> 
> I remember the first motor I made, with wire wrapped nails...it was just magical when it actually worked.


I know the feeling!  I was a little hesitant hooking it up to a battery pack and expected failure.  Much to my happiness it kicked over at 3V and really hums along at 6V.

Bruce


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## DavidR8

That is really fantastic work Bruce.


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## C-Bag

Funny how most see a big paycheck and I see hours and hours of work. I believe you when you say at $ 750 you’re around min wage. Just like with all your other Erector set things making all these parts without the stamping machines they used is quite a feat in itself.

Good job and thanks for posting all the details.


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## BGHansen

markba633csi said:


> I wonder what type of person buys it? Probably older, wealthy, had one as a kid.  Sentimental value, that sort of thing
> I sometimes see stuff on Ebay I had as a kid and think about buying it, but then I go "the past is past, I've moved on"
> One can purchase objects from the past but you can't recreate that time and place- those moments in time and life
> -Mark


That's exactly the market. I was a little surprised at what they went for, considering that in the end it's still a reproduction. But I'm more than happy to spend some time in the shop to meet the market demand.

Bruce


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## Janderso

Bruce,
I think you have out done yourself.
That is very interesting. A lot of work too!


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## Larry$

That's a great idea and project. Each new batch will have less time in them as you refine your processes. When you get to batches of 100 the Chinese will knock it off for $4.95 & free shipping.


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## hman

Bruce - Thanks again for a fantastic project description.  All the detail work that went into this motor is nothing short of amazing.  I'm always happy to see one of your lengthy posts ... but you've really outdone yourself with this one!


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## BGHansen

C-Bag said:


> Funny how most see a big paycheck and I see hours and hours of work. I believe you when you say at $ 750 you’re around min wage. Just like with all your other Erector set things making all these parts without the stamping machines they used is quite a feat in itself.
> 
> Good job and thanks for posting all the details.


Definitely a labor of love in most cases or a case of where I need something and make extras for sale.  Not all of them are winners for sure.  My bullheaded-ness really delayed this project.  My wife is a UG designer and offered MANY times to draw up the parts for me in CAD but I try to not draw her into my projects as she has enough of her own.  I'm still a G-code guy and manually tell the machine the path to follow.  It's pretty simple to know where the tangent points are on a right angle corner and add a radius.  But on a complex profile, not so much.

I did the original pattern for the field casting by tracing a part on paper.  Blew that up 4X and retraced the lines with a Post drafting machine.  Used a circle template to draw the curves and crudely marked the centers of the arcs.  Then measured up the tangent points for the starts/finishes of the arcs with the drafting machine.  Problem was, if I was off in my scale measurement by >0.003" the routine would error.  I spent hours fiddling with numbers to get it to run.  In retrospect, if my wife had drawn it in CAD, the routine would have run with very little debugging.

We have Solidworks and are going to draw the part up during the Christmas break.  She's really good on Unigraphics, so-so on SW, but it's just a short learning curve.  I'll hopefully get proficient enough at it to handle things on my own.

I was expecting around $250 per part and figure that's where the price will drop as I start meeting market demand.  I've got about 3 hours into each full assembly, though I'm not counting machine time as the field casting part is run lights out (about a 45 minute routine).  It's also very inefficient in a few areas, could get 10 minutes out of the routine with some tweaking.  I am usually doing the Foredom work on one part while another one is running so don't count machine time as I have plenty of other things to do while the mill is running.

There is some satisfaction in "completing the puzzle" too.  It keeps the mind active working on something and learning new things in the process or "work the problem" for a better way of doing things.  I tried doing some of the Foredom work with my die filer, but it yanked the part out of my hands and broke a file.  Problem is in work holding, need something more secure.  Or, use the right tool for the job.  I'll try a Harbor Freight air filer next.

Also looking at some fixturing for the end work on the armature pieces.  I currently set the part in the BP vise and manually make passes to cut 0.25" deep on the "T" surface.  Remove the part, rotate 120 deg. and repeat.  Then flip it over and do the opposite side.  It takes me 7 minutes to do that end clean up.  I'll probably "work the problem" by making a fixture to hold the armature and write a routine to do the cutting instead.  I'm thinking about holding the part on an aluminum plate with a pocket cut 1 1/4" round, maybe 1/8" deep.  That'll let the OD of the armature nest in place.  Run a #8 screw down the center of the 5/32" hole to clamp it down to the aluminum.  Have a fixed block that picks up one side of a "T" of the armature, and a second block on the opposite side with a screw that clamps the part in place.  It might not take much time out, but would keep me from hand-cranking the BP.

Anyway, I'm convinced regardless of our end motivation, keeping the brain active by working on projects is a good thing.  Lot's better use of my time than watching sports on TV or Netflix.

Bruce


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## C-Bag

BGHansen said:


> Anyway, I'm convinced regardless of our end motivation, keeping the brain active by working on projects is a good thing. Lot's better use of my time than watching sports on TV or Netflix.


Amen. The idea China would knock it off is often said but in the grand scheme of things not often done. There is just so much detail work that takes #1 a sample of the original, and #2 copying with original intent. That takes a level of attention close to obsessive and I’ve not seen that with things that are not in their culture. Like who’s going to die grind the frame to replicate a cast piece? But without that the discerning collectors would be immediately put off. 

You also have a great mixture of modern like the CNC to do the semi mass production while you do the detailed hand work. So if you were to look at it from a purely monetary standpoint how would they calculate the ROI? For a crude looking antique child’s toy? I would say you have the ultimate niche. You have been incredibly generous with your documentation on doing your process and have you seen others doing what you do? For me it just illustrates what a daunting task it is.

I LOVE seeing this kind of stuff because to all those who’ve gotten used to buying mass produced stuff and see something handmade and expecting mass produced prices it shows the amount of infrastructure, engineering and commitment it takes. I might have mentioned this before but my wife’s best friends husbands father used to own a metal shop. They had contracts to make metal parts for all kinds of stuff. He named off a bunch but the only ones that stuck were parts for the old Colman gas lantern and stove. They had huge machines that punched out 1,000’s of parts a day. I would have loved to go through a place like that and see how they did it.


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## Larry$

I was just funning you with the Chinese quip!
That said, a friend made things in wood that got knocked off. His work carefully made but in simple white boxes that he added a printed label to. The Chinese made a crude copy, put it in a 4 color picture box and it sold @ retail in this country for 50% of Ed's price.


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## C-Bag

Larry$ said:


> I was just funning you with the Chinese quip!
> That said, a friend made things in wood that got knocked off. His work carefully made but in simple white boxes that he added a printed label to. The Chinese made a crude copy, put it in a 4 color picture box and it sold @ retail in this country for 50% of Ed's price.


I figured that Larry$, but as one who’s been making a gadget for 34yrs now that phrase is one of the first things out everybody’s mouth upon looking at it, along with “I thought about this too!” And it hasn’t happened yet but it’s always in the back of my mind and I did expect it to happen. But I also don’t document anywhere how I do what I do.

 What’s interesting is usually after “I thought about something like this” and it will be knocked off, the next words were why don’t you have it made out of plastic? And you’d be smart to have it made in China. I’m not joking. So i can’t help but get triggered by it. I’ve heard of others in my wheelhouse the music industry being knocked off. Even with patents. And I know it happens. But the Chinese being astute entrepreneurs would look at something that has low startup cost and cheap to make and sell with unlimited market. I think I’ve seen those wooden boxes.


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## BGHansen

Larry$ said:


> I was just funning you with the Chinese quip!
> That said, a friend made things in wood that got knocked off. His work carefully made but in simple white boxes that he added a printed label to. The Chinese made a crude copy, put it in a 4 color picture box and it sold @ retail in this country for 50% of Ed's price.


You aren't too far off about the Chinese knock-offs.  At work right now eating lunch and don't see photos of it on my work computer, but I've got a small Erector set from Taiwan that was a Gilbert copy.  They even copied the manual page for page.  Girders, base plates, etc. were identical.  I'm guessing it was produced after the company went out of business in 1967 (sold the name and tooling to Gabriel Toys).  Must be someone saw a market though this set is the only one I've ever seen.

There are some guys in the collecting club who are pursuing sources in China for a number of parts.  Not to bore you with too much detail, but the most used part was a part number S51 screw - 1/4" long.  They varied the head style slightly through the years from 1913 - 1981.  Things like finish (nickel plated, zinc plated, cadmium plated, tin plated, gun blued, etc.) and head size changed periodically.  The only common thing was thread (8-32) and drive style (slotted).  A hard variation to find are the 1931/32 screws.  They were nickel-plated with a head about 7/32" in diameter.  The head was nearly spherical where others have a larger OD and are flatter.  These screws were primarily in the Hudson train sets as the head size needed to be small to fit into some areas.  Guys are getting quotes from suppliers in China for a source of these screws.  

By the way, here are photos of an original motor.  I recall these being from the eBay ad that sold for $3500.

Bruce


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## hman

Possibility for the cuts on the armature ... if you can turn your rotary table vertical, you could CNC mill each arm, then rotate the work 120º, rinse and repeat.  The only complex thing I can think of offhand is how to get the rotational position of each part "zeroed."

I've been doing a number of hand coded CNC projects myself.  But I first design on CAD, then move the cursor position at each intersection to get the X and Y.  The CAD software I'm using is a free but "crippled" version of what's normally a $2000 package.  No 3D output capability, so I wing it.  

Question ... is UG Unigraphics???

"Lot's better use of my time than watching sports on TV or Netflix."  Amen!


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## BGHansen

Good thought on using the 4th axis in the flat state. I metal finish the surface to get the cast look, if I'm off in alignment by 0.01" it wouldn't be the end of the world. 

Bruce


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## hman

PS - One of the delightful features of this particular motor is the "homebuilt" appearance of such features as a finish nail as used an operating handle. Definitely speaks to the culture of the day.


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## Larry$

Was the original casting iron?


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## BGHansen

Larry$ said:


> Was the original casting iron?


The armature and field core were originally cast iron.

Bruce


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## BGHansen

Some updates on the motor project.  First, I made a couple of hardened drill bushings for making the commutators and the holes for the switch cylinder.

Pretty standard stuff on the bushings, used a chunk of 7/8" drill rod.  Faced, center drilled, clearance hole drilled and bored to size.








One bushing has a little over 0.500" hole to slip over 1/2" brass tubing.  Brass contacts are screwed to the commutator base at 120 deg. angles.  Used a hex collet block to do the angular indexing; drilled a #53 and tap hole for a 10-24 clamp screw.  Figured as long as I was at the mill, overdid it and drilled six #53 holes and 10-24 tap holes.











Parted the bushings on the lathe after the mill work.  Flipped and faced to length.






Threw them into the heat-treat furnace to harden.  Left them full hard.



Commutator drill bushing has holes at 60 degrees, switch at 90's.



Goes much quicker sliding the drill bushing in place, then drill the pilot holes for #2 screws and a #43 through the brass.





Same process as described earlier in this thread.  The drill bushings are the length of the finished part.  I band saw off a "chunk" after the holes are drilled, then on to the 2 x 42 sander to flush the trimmed end to length.



Started using a stubby 5/32" drill to knock in the center axle hole.  Let's me skip the center drill step.




Thanks for looking, Bruce


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## BGHansen

Also did some tooling/fixturing for dressing the ends of the armatures.  The armatures had a secondary op to cut down the three legs so the wrapped wire doesn't stick out past the ends of the part.  Also, the tops of the "T"s are turned down around 0.030" so the center area is ~1.030" long and the tops of the "T"s are ~0.970".  That's so the center area can bear up against the armature bracket without the top of the "T" potentially hitting the bracket.

Hman had a good idea using the 4th axis on the flat.  Instead of mounting the 4th, I mounted the 3-jaw chuck.  Plan was to orient the parts off one of the chuck jaws, so it was trammed in before clamping the chuck to the table.


Swept a chuck jaw for angular orientation.



Used the Tormach's built in probing "find the center of a round boss" routine to establish X and Y.  




For those who don't do any CNC work, it's a WONDERFUL way to do repetitive operations.  In this case, the routine would be cutting a triangle to depth on the end of the armatures.  After that, it ran a circle across the top of the "T"s to relieve that area from hitting the armature bracket while the motor is running.  I used the probe to find the center of the chuck, and planned on using it to find the surface of the armature to establish Z=ZERO for the proper depth of cut.  Each armature needed to be machined on both surfaces, plus there were 20 or so parts to machine.  Figured the best way to get away with setting the height just once, plus be able to angularly orient the parts in the 3-jaw was to make a bushing/depth stop.

Started with a 2" round of mystery steel.  Faced, and cleaned up the OD.






Band sawed off a length and drilled a center clearance hole.




I used a planer gauge against the chuck surface to set the bushing flat.  Then faced to height and bored the center so an armature was a slip fit.









Then on to the Bridgeport to center drill, tap drill and tap a 10-24 clamp screw hole








In use, I'd tap the armature surface to be cut into the bushing and tighten the cap screw.  That set the surface of the armature flush with the surface of the bushing.





Couple of nice things about this set up.  The bushing is a known thickness, so the armature surface is also.  I probed the surface with an armature in the 3-jaw to set Z.  As long as I kept chips off my vise deck (my reference surface) and chuck jaws, setting subsequent parts should be spot-on in Z (saves continually probing the height).

The other nice feature is the armature/bushing could be clocked before tightening the 3-jaw to get the armature angularly oriented.  The bushing set on top of the vise jaws so the part didn't fall into the chuck.  I clamped a square to a 1-2-3 block for an alignment fixture.  Set the 1-2-3 block against the chuck jaw and rotated the armature/bushing until the "T" was flat to the square, then tightened the chuck.

Pull the bushing, hit "CYCLE START" and walk away.  I LOVE this CNC for this type of work.  The routine cut the legs of the "T"'s (triangular path) and did a 0.035" pass on the top of the "T"s.  Made relatively quick work of the stack of armatures.











Thanks for looking, Bruce


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## hman

Wonderfully creative!  I can't help wondering what the old A C Gilbert folks (or anybody from that era, for that matter) would have thought if they'd been able to catch a glimpse of CNC tools.  And too bad we don't have a "time machine" video viewer with which to glimpse the future.  Meanwhile, Happy New Year to all!


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## BGHansen

Get ready for a long-winded update on the 1913 Erector set motor project. I originally estimated the world-wide demand at around 20 motors. I made up 30 of them just in case. I’ve sold close to 25 of them to date with no advertising other than offering a few on eBay in two separate auctions. I brought a number of them to the Erector set collecting club’s national show and did well there. Well, time to fire up the presses and make some more. . .

One of the things I like about this hobby is trying to figure out better and quicker ways to do things. I didn’t take any pictures of it, but I’ve changed from a die grinder to a needle scaler to rough up the field magnet and armature. This chopped A TON of time out of the process; at least an hour of total time.

Another of the components that takes quite a bit of time is the commutator/motor switch. I originally made them by gluing a brass tube over an oak dowel (bottom of the first page of this string). I think the details are on the first page of this string. My original method required work on the mill, lathe and drill press. Then bench work to run tiny #2 screws into an oak dowel.

I’ve seen these motors with commutators/motor switches with the body made from an oak dowel or a reddish fiber material. My improvement for the next batch was to make a mold to cast the bodies of the commutator/motor switch. The mold would have the center axle hole cast in along with the threaded holes for the contact screws. I’d also make a die set to form the contacts.

First the mold. Plan was to use a product called “Pig Putty” for the mold material. It’s an epoxy putty that sets up in 3-5 minutes and gets hard in about 4 hours. The molds were made from aluminum.

The original part was about 0.5” long and cylindrical at a diameter of ~0.470”. One end had a taper on it which acted like a spacer washer. The contacts were short of the end of the base so they didn’t short out on a supporting bracket.

My mold design consisted of 5 pieces plus screws/nail. The screws/nail would be inserted into the main core so the threads/nail hole would be cast in. The main core was a ¾” OD round with the center drilled out/bored to 0.470”. Holes for the screws/nail (nail was the motor switch handle) were drilled through the core for inserting the screws/nail in place. Two end caps were made to seal off the ends of the mold: one with a square shoulder and the other with a tapered end. A bushing from 1” aluminum slips over the main core and acts as a retainer so the screws don’t squirt out of the mold as the epoxy is packed. The end caps also have a centered hole for the axle to pass through. The axle also acts as a plunger when inserted to pack the mold.


Mold body for the cylinder.  Drilled and bored the ID to size.  



On to the mill in a hex-collet block to drill clearance holes for the #2 screws that'll be inserted into the mold



Cut a groove in the mold so the heads of the screws were just sub-flush to the OD of the mold



Turning one of the mold end caps.  These were center drilled and drilled with a 5/32" through hole for the armature axle.



Turned the shoulder diameter to size and verified with the mold core



Set the center axle in place and progressively ground down the tips of #2 screws until they just cleared the axle.  Idea is the putty will harden around the screws.  After set-up, back out the screws leaving the threaded holes behind.



Boring a sleeve to fit over the mold core.  This bushing slips over the mold core after the screws are inserted and keep the screws from popping out as the mold is pressurized.



Checking fit of the retaining bushing with the mold core



Final mold pieces (retaining bushing, mold core, end cap with a tapered end, end cap with a flat end.




The photos of the mold construction were actually my prototype. I ended up making a couple of revisions to the main core and bushing to speed up mold making. I ended up making 3 molds for the commutator core and 3 more for the switch.

The original parts were a reddish insulating material I believe called “fish paper”. Pig Putty has a bluish-gray tint which I planned on painting after the fact with some red brick acrylic paint. Instead, a couple of drops of the paint were mixed into the putty as it was kneaded.

Molding goes pretty smoothly. Mix the epoxy, stick the rough cylinder in the mold core. Set the square-shouldered mold cap in place and press down on the epoxy with a pin slightly under 0.470”. This initially packs the epoxy into the mold; I’d apply pressure until the putty was squirting out of the core screw holes. Then set the screws/nail in place and drop the screw retaining bushing over top.  Repeat mold packing with the pin/ram.  Set the tapered end cap in place and insert the axle.  Tap down on the axle with a brass hammer until the mold starts to spread, then squeeze the mold tight again; putty would squirt out the opposite end cap from the axle. Repeat the axle tapping, mold squeezing until the axle entered the opposite cap.  The axle was driven through the opposite end cap and clamped together with a couple of wooden blocks and a C-clamp.


Cut off a chunk of Pig Putty and mix in a few drops of brick red acrylic paint



Put the putty in the mold core, set the flat end cap in place and push down on the putty with a pin/ram to pack out the mold.  I figured the air was gone when there's putty squirting out of the screw holes.



Insert the screws/nail (for the switch), set the retaining bushing over the mold core to keep from squirting the screws out and pack the mold again.  This would squeeze the epoxy putty tight around the screws.



Set the tapered end cap in place, squeeze the mold tight, then drive the center axle through the mold.  Note the putty driven out through the end cap.




Demolding after 4 hours was just a reverse of the operation. I used LPS 1 lubricant as a mold release on the mold pieces prior to inserting the epoxy.


Demolding started with driving the axle out with a brass hammer.  Then twist off an end cap, pull the retaining bushing and unscrew the #2 screws (and/or pull the nail).  Tap out the epoxy casting with a pin.







I'll go on to a part 2 for the contact die and final assembly.  Thanks for looking, Bruce


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## BGHansen

The contacts were done on my Tormach 1100. The base stock was 0.015” brass. The CNC routine used a diamond engraver and spotting drill to rough out the parts. The screw holes were punched with a Roper Whitney #5 hand punch. In retrospect, I’ll try drilling the holes on the mill with the next batch. I typically only punch holes in sheet metal, but maybe the brass would drill okay. Regardless, using the CNC to layout the contacts saves a ton of time over hand scribing.


Layout work takes time.  I used the CNC to scribe the contacts and center drill the screw hole which saved a lot of time.



Punched the screw holes with a Roper Whitney #5 Junior hand punch.  For the next batch, I'll try drilling the holes with the Tormach.



Cut the contacts into blanks ready for forming with a Tennsmith stomp shear and a hand shear.




The die set for forming the curve in the contacts was made from CRS. I figured the brass was soft enough to not need O-1. As you can see from the lathe/mill work, the die set was pretty simple so a second one from O-1 wouldn’t set me back too far.

The design here was a lower die mandrel at the ID of the contact and an upper die bored to the OD. The lower die was made from 5/8” stock with a center area turned down to 0.470” at the overall length of the contact plus a few thousandths. This gave a recessed area for the contact to set in before it was formed into an arc by the upper die. Otherwise, I was afraid the contact could rotate resulting in the edges not being parallel to the center of the commutator axle. I also machined in a pin in the lower die that the contact blank sets on. This keeps the contact from slipping off the lower die.


Turned the center of the round to diameter and a few thousandths longer than the contact.  Idea is to set the contact on this surface and hit it with a "U" shaped upper die to form an arc in the brass.



Found the edge of the step



Drilled an under-sized hole



Over-size reamer for a loose locating pin



Milled a flat on the bottom of the die so it wouldn't roll off my bench!



Retaining pin for the contact.  Left a nub that fits snuggly into the contact hole



Set the lower die on the pin so the nub just stuck out above the surface and parted.




The upper die was made from a piece of CRS.  Center hole drilled and bored to 0.500".  Parted and faced the upper die to length.  The "O" was milled into a "U" at the Bridgeport.


Drilled/bored a length of CRS to 0.500".



Parted to a rough length.  The contacts are 0.45" tall, the upper die is about 0.44" for a little clearance at the top/bottom.





Milled a flat for a hammer target



Flipped the "donut" and made it into a "U".



When mashing the parts, the lower die is set on a sheet of rubber. The contact is set in place, upper die held in place, then tapped a couple of times with a 16 oz. ball peen hammer. The rubber allows the retaining pin to retract some so it doesn’t get peened over by the upper die. Then the lower die without the pin is set on the hard-surface bench and the contact is struck again with the upper die.


Finished die set.  Brass contact sets on the pin.  The lower die relieved area is a few thousandths shorter than the contact.



Set the upper die on top of the contact and give it a couple of taps with a 16 oz. hammer.  The die was set on rubber so the retaining pin would sink down and not peen over or dent the upper die.



The contacts were tight to the die even with rubber on the bottom.  But for belt and suspenders, I'd pull the pin, set the die on the bench and give it another hit.



Lotsa contact, actually goes pretty quickly.




Hit the photo limit, so on to part 3. . . 

Thanks for looking, Bruce


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## BGHansen

Assemble was done with the aid of a bench block. For the commutator, the axle was glued in place by the factory. I do the same using Gorilla glue. Mark the axle where it’ll be in the commutator molding, knock in a couple of dents with a hammer and glue it in place.

The commutator/switch base are set on a bench block, apply a dab of Gorilla glue, set a contact in place and run in a #2 screw. I didn’t show it, but I wrapped the cylinders with a piece of wire twisted tightly to hold the contacts to the molded base as the glue dried.


For the commutators with an axle, peened the center and Gorilla glued it in place.  The photo doesn't show it, but I slip a molded base on the opposite end so the assembly sets flat on my bench block.  Put a dab of glue in place, set the contact and run a #2 screw into the molded hole.



Molding the center cylinders and stamping the contact saved a ton of time on this batch.



My reproductions on the left and center, original motor switch on the right.  My color is actually closer than what the photo shows, it's really hard to tell mine from the original part.




Overall, molding the parts cut out more than half the time to make the commutators and motor switches. Pretty happy how they came out.

Thanks for looking, Bruce


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## C-Bag

Fascinating stuff. It always drove me crazy doing a pile of parts. So I would dream of ways if I was going to do it how I would do it. Doing a million small pieces is the perfect time to devote to that. Good job, lots of great ideas.


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## hman

Bruce, that's truly a fantastic build!  I especially liked the last photo in part 1 - the completed casting.  The slightly irregular coloration really gives it character!


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## tq60

Looks good but silly question.

Why are you removing the shaft to latter glue it in?

Seems like you could kiss it on the grinder where the casting goes to give the. Epoxy something to grip and cast it as done.

Sent from my SM-G781V using Tapatalk


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## BGHansen

tq60 said:


> Why are you removing the shaft to latter glue it in?
> 
> Seems like you could kiss it on the grinder where the casting goes to give the. Epoxy something to grip and cast it as done.


Good thought for the commutator/armature.  The motor switch would still need the axle driven out as a screw is run into the wooden base for a pivot.

For the armature, I could drill out a piece of aluminum for a drive ram to demold the part.  The ram would need to freely slip over the axle and be turned to under 0.47" on the OD to clear the mold.  Might be an improvement for the next batch.  Thanks for the idea!

Bruce


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## tq60

All about reducing steps and saving materials.

Great work by the way, very clever.

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## Winegrower

You have everything here, Bruce!   An appealing historical story, a cool and nostalgic product, terrific designs and tools, and a marvelous well documented writeup, and on top of that, a hobby activity with real cash flow.   Can it get any better than this?


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