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Scratchbuilding a motor


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#1 havlicek

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Posted 08 October 2014 - 09:18 AM

I put together a little "thing" about what I call "motor-scratchbuilding". You know, building a motor from scratch. Why you say?... why not!  Then again, I could ask..."Why build a chassis when you can just buy one? Why paint a body when you can get 'em already painted? Jeepers... why drive a slot car when you could just give it to someone else to drive?

Anyway, the result will be for sure a "one-of-a-kind". It can mostly be done with tools and stuff you either have or can get easily and mostly for cheap.  It's also just a fun/rewarding thing to do all this and hook that bad boy up to a power supply for the first time.   Like a lot of crafty-type endeavors, just the process of building in itself can be a pretty zen-like experience.

 

OK, so enough of the philosophy and on to the build. The subject here is a weirdo motor that has both been given to me at times and also one I've bought after seeing their potential. They come up from time to time on eBay and at the various online places where you can buy slot car "stuff". I think it's some sort of Johnson or one of the other "off-brand" type motors. It's not a Mabuchi from what I can tell and size-wise it's also pretty weird. The width is similar to a 16D, but the height is a bit taller... less than a 26D though. The can length is shorter than a 26D by a fair amount and the can will fit easily (and fairly precisely too) inside a 26D can.

 

1_zps548dcebf.jpg

 

Taking it apart, you find a fairly normal can type motor. The endbell is of a much better material than the Mabuchis, but there's a caged or "self-aligning" can bushing in there just like the Mabuchi "FT" type motors we all are familiar with from the '60s. Magnets are on the thin side, held in with two U-clips (a la the later Muras) and quite strong, measuring a bit above Arcos.

 

The endbell hardware has that goofy arrangement where the brush springs legs are on top of the hoods and the brushes themselves are of the "vertical type" (taller than they are wide). The commutator is pretty much the same as you get on the various current Chinese motors... looking pretty much dead-on identical to say a modern Parma D-motor. Looks like the Chinese all shop at the same  "Motors R Us" place for supplies. The stack is shorter than even the short FT26D stack, is powder-coated, and wound with a bazillion turns of hair-fine wire... good for like 15 RPM in stock form.  :D  They didn't bother to grind off the powder-coat from the outside of the stack as the arm fits fine as-is, so they probably figure... "Why do stuff you don't have to?"

2_zps25445312.jpg

 

Just to give a better visual reference as to the size of this motor... here's a shot of it slipped inside of a 26D can.  BTW, enterprising motor-scratchbuilders can cut up the can for it's sides as "shims" and install these magnets and can sides into a 26D can (obviously) and wind up with excellent magnets that are, again, a bit above Arcos and sized for the .590" diameter 26D arm.

3_zpsdbad17bf.jpg

... on to the build, or I should say "the scratchbuild."   ;)

-john


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#2 havlicek

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Posted 08 October 2014 - 09:34 AM

First things first. Looking at the endbell, it becomes clear that C-can hardware should work well after some eye-balling and measuring with the way things are spaced. I removed the stock goofy stuff, drilled where the original posts were and, as they say in the land of pâté, croissants, and Chateauneuf du Pape... "et voila!" A couple of button head screws cut to length on each side and it all works... pretty much. The endbell bushing tower is on the narrow side, so the hardware needed to be radiused a little to clear the comm and I'll have to space the hardware vertically at final assembly... a piece o' cake by adding some of the aluminum "heatsink" plates.

The can had pretty much zero ventilation (one teensy hole), so I hogged out a rectangle on top and bottom, and stripped it of its plating. Looks more like a slot car motor already! While the can is drilled and tapped for mounting, I drilled the endbell for mounting and will go "endbell drive" with this motor as it's more familiar and should take only slight mods to a motor bracket to get it to mount up.

4_zps766d3c1e.jpg
 
Now that I have a basic setup, I can "build" the armature to fit. Since the arm stack was already powder-coated, I pressed out the old splined shaft, cut arm spacers, pressed in a new drill blank shaft, covered the new spacers with some JB Weld to insulate them, and installed the original comm (it will be more than fine for this motor, and the purpose here is to do all this with pretty much what comes with the motor). While I had the stack off the shaft, I also flattened out the top and bottom of the arm's powder-coating with a piece of sandpaper stuck to my glass work surface. This will give me a little bit more room for winding and also result in neater coils since the stock powder-coat is a bit on the thick-and-lumpy side.
 
5_zpsad823f7d.jpg
 
To finish off the set-up, I did a quickie-coat of wrinkle finish black on the can and epoxied the magnets in holding them with the stock clips temporarily while the epoxy cured. All together, it makes for a pretty neat looking motor... very "slot car-like" and still weird enough to be interesting:

6_zps6c5c87dc.jpg
 
... on to winding!
 
-john


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#3 havlicek

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Posted 08 October 2014 - 09:50 AM

So, this stack is pretty much exactly "26D" diameter, although significantly shorter. Since the original still had the powder-coat on the outside of the stack, the arm wouldn't fit my 26D clamp, so I took that off and it fit perfectly. Before winding, I also set the com timing at around 20 degrees advance (the modern standard CCW), and it's off to the winding crank set up with some #29 wire. Since the stack is short, I went with my old formula..."alotta wire" (65 turns of #29), figuring that should be about right. One pole done...

7_zps7ffe1202.jpg

 

After winding all three poles, I silver soldered the comm connections. Everyone has a soldering iron right?... and solder should be fine for this arm.  Anything hotter than a #29 is probably pushing your luck with solder.

8_zpsc9946643.jpg

 

9_zps104dd806.jpg

 

Checking the arm (again and again to avoid problemos) in the setup and everything's A-OK.

 

10_zps673aa690.jpg

 

Next step it to cut/true the comm... taking off as little material as possible. These comms don't have so much to begin with, so it pays to be careful here.

11_zps4ffc66ab.jpg

 

With the arm epoxied, tied, and soldered, it's ready for balancing. I did this one here on my R-Geo static-balancing jig to underscore the points that you don't need a bunch of fancy-shmancy stuff... and you can do it all yourself. A dynamic balancing job would be more accurate and the arm might even run significantly better. However, in this case, the arm took very little to balance (good shaft, neat winding patterns, and neat epoxy  equals easy balance) and a good static balance should be fine for the purposes and the wind of this build.

 

12_zpsa34009d9.jpg

 

The finished arm looks pretty nifty, pictured here all tied up like your mom's bracciole (say..."brahzhole"  :D) :

13_zpsa6094ae6.jpg

 

A quick last trip to the meter to be sure everything's good and there won't be any..."SONOFAGUN!!!" moments when the motor gets fired up. Final measurement is .460 ohms which should put the motor solidly (with the nice magnets in there) into zippy/fun territory.

14_zpsefd0ecd7.jpg

 

On to final assembly...

-john


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#4 havlicek

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Posted 08 October 2014 - 10:06 AM

With all the hard work done, now it's down to final assembly... looking at how things line up, watching out for any "gotchas", first spinning by hand to be sure nothing is hitting stuff (especially sharp and pointy stuff!!!) it should't be hitting, etc.

Both the tail and the top of the comm get trued and, if necessary, a bit extra material can be removed to fine-tune the arm for the setup while making sure it's "floating" ("centered") in the field. With this arm, I took an eentsie-weentsie bit extra off the tail spacer so I could add another thin arm spacer back there and tighten up the arm's end play.

15_zps553baef2.jpg

 

Next I drilled the can and endbell for those nifty Mura black screws I like so much. :D  I also added two aluminum "heat sink" plates to each side to raise the hardware to clear the comm tabs. The stock motor had a bunch of spacers at the comm and very little room at the top of the stack for winding. I raised the comm when I cut the comm spacer to give me some more real-estate since the end bell "tower" is plenty tall on this motor.  More room to wind and less of the "10 lbs of shizzle in a 5 lb bag" syndrome equals a happier motor. I marked the motor polarity, added a sticker because it's cool to "sign" your work, and hooked 'er up to the old power supply. The motor sings a mighty sweet song that goes something like this: "WEEEEEE."   :D  

You can do this, and it's super fun. Remember that, in the days of slot car prehistory when people wore button-down shirts and slicked their hair back with a generous amount of "Vitalis" to go to the track (!), all kinds of motors were being repurposed for slot cars. Even when there were plenty of slot car motors available, everyone was tearing them apart to make them go faster. The people who got good at it (*they were probably just more doggedly determined and/or insane) started selling their motors and the "speed wars" were on!

 

16_zps88863fea.jpg

 

17_zps8581e2a3.jpg

 

-john


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#5 Pablo

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Posted 08 October 2014 - 10:25 AM

Very sick! I love it! :good: :good: :good:


Paul Wolcott


#6 havlicek

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Posted 08 October 2014 - 10:37 AM

Thanks, Pablo!

 

-john


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#7 SlotStox#53

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Posted 08 October 2014 - 11:27 AM

Awesome! Looks like a one off custom Mura straight out of a slot car magazine, think spy shots of a new motor being released :D :D

#8 havlicek

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Posted 08 October 2014 - 11:43 AM

Thanks Paul...BUT  ( :D )  the idea here is to show people who are even just *maybe* thinking about tinkering with motors that it's not THAT much of a big deal.  Otherwise, this particular motor is nothing special, but a way to show the steps involved.  So...go for it!

 

-john


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#9 CoastalAngler1

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Posted 08 October 2014 - 01:11 PM

You make it look easy...from recent experience I say it's not.  You and Pablo gave me some very excellent training on motors, and I say mucho gracias!   

 

"It can mostly be done with tools and stuff you either have or can get easily and mostly for cheap." - doesn't look like tools I have around that are cheep...

 

Not trying to be negative, but lets be real - YOU ARE THE motor MAN!  Love your stepwise post!   


Charlie McCullough

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#10 havlicek

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Posted 08 October 2014 - 01:30 PM

You make it look easy... from recent experience I say it's not.

 
Look, I'm not trying to minimize this stuff... or the effort it takes. Certainly, building a scratch chassis accurately to fit a body, handling, spec and strength considerations isn't easy either, but it can be learned and a lot of people do that stuff, many at a really high level. The point here is that this is just another aspect of the hobby, one that gets "mystified" to a certain degree and one that was a huge part of the hobby at one time.
 

"It can mostly be done with tools and stuff you either have or can get easily and mostly for cheap." - doesn't look like tools I have around that are cheap...

 
Well, instead of the meter I use, a decent digital multimeter ($15-$20) can work and a lot of racers have one of those. Both of my cranks were made by me. The various clamps have either been donated or traded for... with a couple oddball sizes having been made by machinists right here... CHEAP. Crud, people spend waaaaay more on tires, gears and other disposables.  

 

This for a hobby where a controller can easily cost a couple of hundred buckaroos or more. My balancing jig took the place of one I built on a block of wood early on. After that you have what?... a toaster oven!  

 

Yes, this stuff is cheap! Dig around, repurpose stuff, buy weird motors on eBay.
 
-john


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#11 CoastalAngler1

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Posted 08 October 2014 - 09:53 PM

I plan to watch in amazement. You're right as always, a true motor artist. 

 

I got a long way to catch these fast racers here in FL...

 

low bucks racing.jpg


Charlie McCullough

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#12 havlicek

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Posted 09 October 2014 - 10:04 AM

Hi Charlie,

 

You know, all of this stuff... whether it be chassis building, motor building, body painting (in itself a real art... probably more so than the other aspects of the hobby, just look at what Jairus and Noose do and how few people can get to their level!) etc., are "what you make of them". You can do any or all of them well enough (with practice) to have a rewarding/fun experience... one where you can proudly show off your work because you did it.  

 

On the other hand, you can keep at them and continually improve just for the satisfaction of getting to a higher level. You can learn/practicing painting with old soda bottles. You can learn chassis building with a Dremel, pliers, and a soldering iron.  ou can learn motor building and rewinding by asking around for other people's junk motors and tearing them open.  

I've always been the kind of guy that, since I was a kid, wanted to know what makes things tick... and always asked myself the question about all kinds of things... "can I do that?".  

 

Here's the deal on motors specifically. When I was a kid, my friends and I all shared whatever information we had about rewinding... but none of the motor companies or the "pros" shared any of the deep dark details. Learning about this stuff was a tedious and frustrating experience, with a lot of burned-up motors getting tossed.

 

Now with the internet and places like Slotblog, the situation is at least a little better. You can find at least some good info with just a few mouse clicks, and I've tried to do my part in that regard, hoping to help others avoid some of the frustration. Some aspects of the technology have changed a little, making things a little more difficult for the home-winder and it has been tough getting good information as to how you can, for example... weld your comm connections, or powder-coat your stacks, but that stuff is only important on the hotter winds. Even so, you can find out about all that as well because I've been there and am happy to share what I've learned.

As it always has been with slots, it's important to separate the malarkey from the good info, because there are always people ready to share nonsense and/or slot-myth. I try to avoid telling people something as fact if I'm not sure and will try to put in some sort of qualifier or disclaimer if I'm not certain about something. On the few occasions when an undisputed expert chimes in... someone like a Dan Miller or a Bill Bugenis (Monty Ohren was pretty free with the advice too, but his passing has left a void), it's important to pay attention and take notes! These guys have learned the hard way, by doing it until they get repeatable top-shelf results.  

 

Other than all this, it doesn't have to be too involved or expensive, but it always takes sticking to it and digging in.

 

-john


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#13 Pablo

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Posted 09 October 2014 - 07:16 PM

Bingo. :music:


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#14 Maximo

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Posted 10 October 2014 - 11:50 PM

That's a beautiful piece of work and using that weird (ish) motor reminds me once again of weaving straw into gold!

 

You are a master and your articles are fun reading.

 

-max Vrrooooom...!


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#15 havlicek

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Posted 11 October 2014 - 09:14 AM

Thanks, David. :)
 

your articles are fun reading.

 
Well... I try and keep 'em interesting. The guys who really know about this stuff either don't share much or are pretty dry when they do. I pay particular attention when someone like a Tony P or the others chime in, because they have decades of experience with motors (in Tony's case... both slots and R/C), so whatever they write is "fun" for me to read.   :D
 
-john


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#16 Gator Bob

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Posted 11 October 2014 - 06:11 PM

Another great creation, John. :good:

 

Bet it is lighter and faster than a 607 or 617 with the short stack and better mags. :)

 

Nice endbell - what letters/numbers are molded in?

 

I do like the shim in a 26D idea thing.

 

It would look very cool in thin 26 can and leave the top and bottom of the cad plated shim and only one round hole showing. 


Posted Image
                            Bob Israelite

#17 havlicek

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Posted 11 October 2014 - 07:57 PM

Hi Bob,
 

Bet it is lighter and faster than a 607 or 617 with the short stack and better mags.

 
It's definitely faster and a bit lighter, as well as more compact. It's actually a pretty cool package that would work very well in a scratchbuilt chassis.
 

Nice endbell - what letters/numbers are molded in?

 
I'll have to go back and look at one of these (I still have a few), but I *think* one of the letters was a "J" which is why I was guessing it might be a Johnson. The material seems to be the same stuff the Hong Kong Mabuchis used, so it seems significantly harder/tougher and more durable than even the black Tradeship endbells which were in themselves a little better than the stock Mabuchi end bells.
 

It would look very cool in thin 26 can and leave the top and bottom of the cad plated shim and only one round hole showing.

 
I've used them in some 26D builds using only the cut up sides and they gauss very strong. I would worry about the whole can in there because there would be zero ventilation, but I guess it *might* be OK with the Champion endbell and it's better ventilation. I only have some of the Champion (thicker) 26D cans, but they should fit the thinner Mabuchi cans fine. 
 
-john


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#18 don.siegel

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Posted 12 October 2014 - 05:36 AM

Another excellent article, John; thanks. I like your attitude a lot! 

 

What amused me on this one was seeing that old floating bearing - thought those went out with the dinosaurs! I probably have a couple dozen cans where those bearings have fallen out, for one reason or another, and thought the technology would have changed in the meantime. But they also fell out because we were taking them apart, not paying attention to the splines, etc. Maybe on a stock motor like this they're adequate... did you leave this one as is? 

 

Don 



#19 havlicek

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Posted 12 October 2014 - 06:52 AM

Hi Don, and thanks for looking in.  

 

Yeah, I was surprised to see that type bearing in there as well!  I've had a bunch fall out on me also and it's always been me forgetting to check to see if the shaft is splined. I left the bearing as is on this motor since they seem to work fine as long as they're tight in their socket and not worn.

 

I did another FJ13UO a few weeks back that was a real screamer, like scary fast, and the bearing was something that worried me on that one... but the motor is tight and smooth.

9_zps43f8efed.jpg

 

Then I just got a bunch of motors from Canada to do, among them several Cox FT16D and two of them had no splines on the shaft and the third was splined (?) and I almost pulled the bearing out of the socket before i realized what was what.

 

-john


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