3573 replies to this topic

[Alchemist]

Hope you had a great Christmas John, as well as everyone else that celebrates this holiday!

John,

I hope you'll take pix of your Champion 26D project and share them with us please?! May I ask please, if you have any pix of the Mura coms you recovered? I love Mura motors!!!!

By the way John, the motor did arrive safely and it looks "hot" - pun intended - LOL!!! Thank you again!

[havlicek]

Hi Ernie and Merry Christmas to you!,

By the way John, the motor did arrive safely and it looks "hot" - pun intended - LOL!!! Thank you again!

Glad it got there OK Ernie...and the pleasure was all mine

I hope you'll take pix of your Champion 26D project and share them with us please?! May I ask please, if you have any pix of the Mura coms you recovered? I love Mura motors!!!!

...your wish is my command Here's a picture of what I have so far. As I said above:
-the can was fairly misshapen, but since there's no paint on these things I did whatever "body work" I could that wouldn't make things look worse. After straightening it out as best as I could, I polished it up after some work with #600 and then #1200 sandpaper and then ground off the rough areas where the endbell retainer tabs used to be. After that, I removed what was left of the can bearing and installed one I had salvaged from another motor that was in good functional shape (I'm going for fairly period correct here, both with the parts and the wind). The can was finished-off with a nice set of Arcos in the Champion shim. The endbell is NOS from Roger at Mid America and I installed another reclaimed bearing in that, saving the bushing for another day.

I assembled the arm stack from loose plates/lams I had left over and made it the same length as the Tradeship blanks. The shaft is a new drill blank (OK...that isn't exactly "period correct") and the com is one of the salvaged Muras from the Wasp arms Jeff Easterly sent me. I have some Tradeship coms...but the Muras (even though also not "period correct") can be seen as the equivalent of the Champion "Blow Proof" coms. I also like the fact that the Mura com will better fill the hole in the endbell, leaving a smaller gap between the brush tubes/heatsinks and the com. Since I have no idea where this motor will go or who it's for yet, I left the shaft long on both ends so that the completed motor can go either endbell or can drive. The motor will be either a #28 awg single or a #29 awg single as I have some comfortable 26 winds worked up for either.



-john

PS, now that I look at the picture, that com isn't one of those from the wasp arms that Jeff sent me. Oh well...you get the idea

[Alchemist]

John,

Thank you for posting the picture. To me, the way you worked the arm stack looks as though it was machined from billet - Fantastic craftsmanship John!!

[havlicek]

Hi Ernie...and thanks Here's the arm all done up. I did a #29 single and it comes in at just over an amp current draw and around .4 to .5 ohm


...and in it's new home. I wound up not using the endbell bearing as it was really making a racket and not spinning properly, so in went the bushing. I installed a pair of FT16D hoods over a pair of FT36D brush tubes/heatsinks so the motor can use the larger brushes that are more easily available. I finished it off with a pair of post protectors and Camen regular springs. The motor is much faster than the stock motor, but should be able to run all day no problemo. As I mentioned earlier, I left the shaft long on both ends so it can go either can or endbell drive for whoever gets it and whatever they put it in.



-john

[Alchemist]

Real slick motor John!

On a motor like this, if one were to set it up to run on a King, would a gear ratio of 4:1 be satisfactory or would you suggest gearing it taller like 3.5:1 or 3:1?

Another question please - if you "double wind" an armature, does this provide more torque to the motor and lower the rpms?


Ernie

[Champion 507]

I always heard rpm's went up and torque went down with a double wind but someone please correct that if it's wrong.

[Slotgeezer]

Doug, you're right...less resistance = more RPM... Sometimes more than you can get to the track surface! LOL!...

John, another masterpiece... Really love the idea of the 36D brush-barrels instead of the 26D sized ones... I have quite a few 36D barrels I should send your way... I won't be needed them, as I convert everything to Parma Death Star hardware, for availability issues...

Always loved 26D stock motors... Kinda like TSR - D3 motors, good bang-for-the-buck value! LOL!

(Yep ... shameless plug..... Hey, Dokk.... Got any spare TSRF's laying around, for Jaildoor class? )

Onward, John! Onward! LOL!


Jeff Easterly

[havlicek]

Hi Guys and thanks!,

On a motor like this, if one were to set it up to run on a King, would a gear ratio of 4:1 be satisfactory or would you suggest gearing it taller like 3.5:1 or 3:1?

Ernie, 4:1 had always been the starting point for most hotter-than-stock motors for me. So much depends on the track power, the chassis weight and type, the body...even the controller and driver that dialing things in afterwards is really a matter of trial and error. Most all of the Mabuchi and Mabuchi-type motors were short on brakes so numerically higher ratios can help that somewhat. Hotter winds (and this one isn't at all HOT) can get too warm if they're lugging and also if they wind out too early...so they need even more tweaking of the ratio to find the sweet spot. Still, starting at 4:1 should point you in the right direction pretty quick.

Another question please - if you "double wind" an armature, does this provide more torque to the motor and lower the rpms?

Doublewinds act effectively like bigger wire single wound arms and the thought is that a doublewind will act like a single that is three whole sizes larger...so a #29 double is something like a #26 single...more rpms and yes...less torque. Upping the magnets and closing the airgap will bring back more torque ...but will add heat. Sometimes for a vintage or vintage-type motor that's not going to be raced but simply enjoyed, it's probably better to keep the airgap a bit on the wide side and live with less torque and brakes for the sake of motor longevity...unless the person keeps it down to only a few laps at a time and monitors the motor for signs of "China Syndrome" The thing about DC current flow as opposed to AC current flow (DC tends to flow through the whole wire...AC tends to flow nearest the surface in larger diameter wires...but throughout the wire in smaller wires...except at very high frequencies) may not even come into play. Since you are basically creating a larger diameter wire with a doublewind, the advantage seems to me to be that you can more easily and neatly fill the limited space of an armature with a double wind with the right amount of wire. Picture two small wires laying side-by-side as opposed to a single large wire of the same capacity...the two wires can be seen as sort of a flattened bigger wire and it becomes easier to see why this would make a neater/more compact coil. Having said that, most winds can be accomodated without too much difficulty by just using larger wire rather than doublewinding...and doublewinding is way more fidgity than single winding. Still, doublewinds were popular and and powerful arms and there's a "cool factor" involved with them. I don't think (and I hope someone corrects me if I'm wrong) that a double wind has any real advantage over an equivalent single wind...except maybe when the track doesn't have much power??? Maybe not even then. Real motor-gurus and actual electrical engineers of course could surely answer this question definitively and back it up with the scientific theorey behind it. I'm just going by what I've seen and info provided by others 4 or so decades ago!

Jeff, yep, the 26Ds (especially the Champions) are neat motors and make cool cars in modded/hybrid Dynamic and straight scratchbuilt chassis. BTW I can use those 36D brush barrels for sure. I'm at the point here where I have some 36D motors with none because they wind up in 16D and 26D motors at times

-john

[JoB]

Hi John,

Very nice work indeed. I following this thread with much interest.

I have a few questions though.

How do I press out a shaft from the stack?
Do I need heat or...?
The laminates is OK but the shaft is no good to much rust has made it kind of rough on the surface.
Should the laminates be glued back on a new shaft?

Also do you glue the com. on the shaft? and what glue to use if so?

Jens

[Bill from NH]

Rear tire diameter is also a critical factor in determining what gear ratios to try. For anything larger than about .790" start with a gear ratio numerically higher than what you think you might need.

[havlicek]

Hi Jens thanks, and I see you're pretty new here so welcome too! I'll try and do my best with your questions.

How do I press out a shaft from the stack?

This can be a very difficult thing to do with common hand tools, but it can be done. First you need to realize that the laminations of an armature will grip the shaft even tighter if they deform at all when pressing on the shaft. A great way to illustrate this is the locking mechanism of a bar clamp (like the Jorgensen "Pony" clamp). These are made of several layers of steel that are held at an angle to the bar that "grab" the bar as they are forced against it even though the hole in them is far larger than the diameter of the bar. The same exact thing happens with arm laminations when you deform them, and they will grab the arm shaft tightly. Any rust on the shaft will naturally make the process even more difficult. It's therefore important to keep the arm laminations as flat and undisturbed as possible when pressing against them. I use a carpenter's 6" "hand screw" clamp for pressing mine like this (but made by Jorgensen):



For pressing shafts, I closed the clamp and drilled a 7/64" hole through both sides close to the ends so that a shaft (including the larger 36D shaft) can pass through it. These clamps can exert a great amount of pressure and even though they're made of very hard wood, they can cause an arm stack to indent the wood and deform the stack which is bad...the harder you press the more difficult moving the shaft becomes. To prevent this, I place several steel washers with small center holes behind the arm stack to support the stack and prevent it from distorting as I exert pressure. The other thing working against you is that ypou can VERY easily bend even a drill blank shaft doing this and that will also prevent you from easily pressing out the shaft. To prevent this, I cut the shaft close to flush with the stack on the shorter end and then grind it flush with a slight center depression where it enters the stack. I then use a piece of hardened steel only a bit longer than the typical stack as a "pusher"...aligning that with the center of the stack and pressing against another piece of hardened steel between it and the face of the clamp so the "pusher" pin doesn't just drill itself into the wood face of the clamp as I exert pressure.

Sometimes when a shaft is being particularly difficult, I will push a bit from both sides to try and make the stack loosen it's grip on the shaft...finally exerting the most pressure on the side I cut off. Frequently, you'll hear a "pop" as the shaft begins to move and feel the movement. Most shafts will come out...some I just can't budge. I'm sure that a "press" such as are used by machinists properly fitted for the task would make short work of replacing shafts, but I don't own one It can also help to press the stack instead of pressing the shaft. To do this, you use a piece of steel tubing that fits easily over the shaft. Sometimes alternating between pressing the shaft and pressing the stack...as well as alternating between presing either end will loosen a stubborn shaft. Of course, you need to replace the shaft with a nice straight one and not to bend it as you install it. I've found that the lams that just caused you so much difficulty removing from the old shaft slide easily onto the new one!

Do I need heat or...?

I've never used heat more than a couple of times just to see if it helps and it didn't seem to so I don't bother with the additional problems associated with handling a heated arm.

The laminates is OK but the shaft is no good to much rust has made it kind of rough on the surface.

Spinning the arm in a Dremel tool or even a drill while pinching some Scotchbrite around the free end will clean that up pretty well if it's not too bad...without changing the diameter of the shaft very much. It will leave a dull finish on the shaft that would make static balancing difficult if you wanted to do that. If the rust is more than just a little surface rust, then changing the shaft is a better idea.

Should the laminates be glued back on a new shaft?

In many cases, you'll find that the lams all separate when you remove the shaft...much more often with Mabuchi arms than with the later thin-lam and powder coated Mura and other arms. You'll also find that the lams, because of how they're fabricated, definitely have a more "concave" side and a "convex" side. You can see this when you look at each lam closely under good light. This makes it important to assemble them on the new shaft with all the like sides facing the same way so you get a nice tight stack with no gaps. Once assembled and oriented so all the poles line-up (along with any stack insulators if you use them), you need to clamp the stack assembly together. I use battery clips like these:



They exert enough pressure as long as the stack hasn't been deformed, are inexpensive and fit nicely but any appropriate clamp is fine. I also use these because the whole stack plus the three clamps will still fit in a small oven. To glue the stack together again, I use epoxy applied only to the interior faces of the three poles and only enough to cover so it doesn't drip and make a mess. Of course, care needs to be taken not to glue the clamps to the stack. Epoxy works very well for this because as it thins out with heat, it will get into all the little spaces of the stack and really bond it well. Often it will penetrate well enough to bond the stack not only to itself...but also to the new shaft.

Also do you glue the com. on the shaft? and what glue to use if so?

Yes I do glue the com both so it doesn't move around while winding...but also to keep the arm's timing set. I also use a tiny drop of epoxy for this...as well as the tail spacer and the com spacer (if used). To be sure the epoxy does it's job, I rotate the com and spacers as I seat them so that a bit will even get inside between the shaft and the hole. They won't move after curing...at all! I'm sure some cyanoacrylate ("Krazy Glue") would be fine for this, but I try not to use the stuff on arms as when the arm gets heated with use (and/or oven curing of any epoxy) it may release some cyanide fumes.

I hope this helps and if I need to be clearer, just ask.

-john

[havlicek]

So after talking to Jeff Easterly for a while about a specific application, I set out to build a 36D to fit. This one's a #29 wind that draws around 1.4 amps (that should go down as I'm going to lighten the springs) and meters .5 to .6 ohm:


I cleaned-up and repainted a setup I had here that wasn't in too bad a shape...metallic red seemed neat and was the color closest to me at my bench so...



The caged bushing was worn and fell out of the can so I soldered-in a new bushing. The magnets are the stock Mabuchis (complete with the dried-on masking tape "shims" from decades ago), and the motor sounds great! I'll probably add some post protectors to the setup when I change the springs, but it seems to run cool-ish

-john

PS...the com is (I believe) a Champion piece I had kicking-around. There are several other options including the stock Mabuchi which seems a lot stouter than the 16D sized ones as well as the Tradeship which is really nice.

[Phil Irvin]

aaa YES A DOUBLE WIND.....

Back in 67/68. We had one track that had a power supply rather than batteries. Everybody hated to run that track. Most of us would run single 26 on the battery tracks....some Maybe 25 if the power was VERY good.....But when the supply track had a full track of 26s.....EVERYBODY SLOWED DOWN.. ....I read about a double 29 that some used on low power tracks (THORPE?) I did a double 29 on a Mura stack after taking 2 laminations off. It was slightly slower than a single 26 on good power but was faster on the track full of 26s on the low power track . That was the only track I ran the D 29 on. Yes it RPMd higher and geared the same as a 26. It had less torque. I always ran 2-3 teeth more on the spur to make up for it. I never put down the wind on any of my teck sheets...After a year or so. They went to batterties.....Bummer....But Fun while it lasted .

OLPHRT
PHIL I.

[Bill from NH]

John, what's your thoughts on using .078 piano wire for 16D shafts after using it on a few? Will you still use it even though a drill blank is usually harder?

Phil, years ago I ran wing cars on a power pack track in Maine similar to what you described. With 7 or 8 cars running, I ran my Steube 22s(hand-wound Grp. 20s) & was very competitive. These guys ran open wing cars weekly on both Fri. & Sat. nights. A couple weeks I won both nights. With fewer cars, I usually ran a Camen 27/28 on that track, but I don't remember it being all that outstanding.

[havlicek]

Hi Bill,

There's nothing at all wrong with .078" piano wire as 16D/26D shaft material. It's usually straight enough in 2" lengths and is fairly hard. The only gotcha I see is that it may not be dimensionally right for some bearings/bushings. The thing is that when I can manage it, I figure I should do my best on every arm and drill blanks are stronger AND have a better finish which makes balancing easier. Little by little, I'm trying to get better and more consistent and the easiest part of that is using better parts. It's the actual winding that takes work

-john

[JoB]

Thanks for the nice answer. I will read it thorough and slowly to understand it all, and ask again if I somethings are not understood.

I do have a question now though. Where to get drill blank shafts to stacks?

Jens

[havlicek]

Hello Jens,

I have gotten them (2mm drill blanks for FT16D and FT26D) from here:

McMaster Carr

The part # is : 2900A234, so just put that into the search ("find") box up top. As an alternate on say Mabuchi motors that won't be too hot, you can use .078" piano wire cut to length. This works fairly well and is very inexpensive. This is also a good choice for unusually long shaft motors (like four wheel drive), as you can make the shaft any length.

For the big motors (FT36D), you can get 3/32" drill blanks from McMaster Carr as well...or use 3/32" drill blank axles.

-john

[havlicek]

Not a rewind, but it looked like it might have needed one beforehand I rehabbed this nice Mura for Brian McPherson and it came out pretty sweet. Current draw is down 25% or better and it spins way faster than when it got here. I think this old Mura is going to see a bunch more track time before too long Oh yeah Brian...there's a little something extra in the package with this

-john

[tonyp]

Nice color combo! Looks great...

[havlicek]

Thanks Tony, it's not far off from the original color. These motors are still very cool

-john

[One_Track_Mind]

Oh YEA!

MINE!

Thank You, John

[havlicek]

Right on buddy. It's a sweet Mura for sure and should be good for quite a while now...enjoy!

-john

[Champion 507]

John,

Nice mill, bro. What brand and color paint did you use? It's obviously light blue but did the manufacturer give it some special name?

[Bill from NH]

Looks like NH blue to me Doug!

[havlicek]

Hi Doug...Bill got it right...New Hampshire Special Blue It's really Rustoleum "Harbor Blue" #7722 and it is pretty close to the original Mura color so it works well with the blue endbell which is also cool. I hadn't seen them before but Rick T gave me one which I'm saving for some special build. I also had the blue spring insulation to complete the package. Thanks to Barney, I have some stickers here in white, clear and gold and even though it sounded like a weird combo, I tried the gold and liked it best. Anyway, it's always nice to do these rehab jobs and see the motor like it's new again.

-john