28 replies to this topic

[havlicek]

The title says it all, and besides the actual machining, there are some subtle variables in play here that can really matter. First, here's a rough drawing for a starting point:

... building a winder is easy, it's the actual "clamp" that really matters!  This one should be able to clamp down to .510" with a "jaw gap" of .05" or so and a normal opening of .522"-.525".  

The closer the clamping screw is to the "jaws," the more leverage it will have over the clamp and make clamping easier. Here's a thing though. As you tighten the clamping screw, you are putting the two jaws more and more "out of parallel" as it flexes to open and close, "pivoting" on it's rear solid section. The one end of the screw that passes through the clamp with no threads can, if it's a little larger than the screw itself, allow the screw to "adjust" as it tightens.

The width of the slot (shown above at .050") will somewhat affect how far the clamp closes, and the length of solid material at the rear of the clamp where it screws into your crank will somewhat limit how far the clamp will open as well as how easy the clamp will open and close. As to opening, the clamp will only open as far as it's "resting" state allows.

 

A really trick thing I haven't seen would be to install a circlip inside the slot on the clamping screw against the non-threaded side of the clamp. That would allow the clamping screw to "push" as well as "pull," and you could open the clamp to a size larger than it was originally machined at. We're dealing with a limited clamping range, but a few additional thousandths either way can make a big difference in how useful a clamp is. You're never going to get a clamp that works for .518" blanks as well as 36D size arms, but a little more range could be a very nice thing!

A clamp can be made from (mild) steel, aluminum, brass... whatever. I have examples of all of them. Personally, I "like" the brass ones best. Brass has a natural "slipperiness" (lubricity) that gives it a small advantage. As the clamp opens and closes, it's stressing the clamp-screw threads especially, and you can feel that with aluminum clamps... the screw gets "twitchy" and "bind-y" when you're tightening it more than a little. I *think* that brass (regular 70-30 "yellow brass") is probably not going to strip any faster than aluminum... maybe titanium is the way to go!  

The above clamp might need some fine-tuning after machining to make it work optimally with whatever lams you're using, but having the clamp screw closer to the actual clamp-opening is better.

If you are or know someone who is a master machinist, building an actual pivot into the rear of the clamp where it screws into the crank arm, AND capturing the clamping screw with the circlip would be insane, and prevent most of the wear these things see. That would most likely be a $400 clamp though!

-john

[Geary Carrier]

Hi John,

 

There is a simple way of obtaining expansion of the clamp which would work for a retro-fit of the design shown above...

 

Referencing your drawing in the current view, insert a 1/4-28 cap screw with a rounded tip (just sand smooth and polish) to the left of the clamping screw as close to the .380" hole as you can. You would tap the threads on the bottom of the clamp, opposite the side the clamp threads are on. This would expand the jaws as you tighten the screw against the clamp slot and give you those few mils of expansion that you mentioned. You can still tighten the clamp screw as you normally would.

 

You would need to lubricate the threads and tip of the expanding screw with a nickle based anti-seize or equivalent. The clamp screw would also benefit from the anti-seize and prevent galling especially on aluminum.

 

Would you please elaborate on the pivot at the back of the clamp that you mentioned, not quite sure what your looking for there...

 

 

Thanks,

 

Geary

[Phil Hackett]

The clamp you're describing is in reality a spring. C-Clamps are springs. An armature clamp is a modified C-Clamp.

 

Steel is the best material for a spring. Brass will work as it is springy but the springiness will disappear after a while but steel will not. I use brass emergency collets and they die after a while and need to be "restored". They are good for 2 "restorations" and then it's the scrap barrel. I have yet to trash a steel emergency collet because of the lack of springiness.

[havlicek]

Hi Geary,

 

 

 

Referencing your drawing in the current view, insert a 1/4-28 cap screw with a rounded tip (just sand smooth and polish) to the left of the clamping screw as close to the .380" hole as you can. You would tap the threads on the bottom of the clamp, opposite the side the clamp threads are on. This would expand the jaws as you tighten the screw against the clamp slot and give you those few mils of expansion that you mentioned. You can still tighten the clamp screw as you normally would.

 

 

Good thinking!  That would work as a retrofit, and might be better than the circlip functionally-speaking in practice.

 

 

 

Would you please elaborate on the pivot at the back of the clamp that you mentioned, not quite sure what your looking for there...

Well, think of the clamp being like the working end of a set of linesman pliers with no handles, instead of a solid piece.  The ultimate range and capacity would still be limited by the radius of the clamp and the OD of the arms, but it would provide the greatest possible range and should all-but-eliminate failures from the metal being fatigued over time.

 

Hi Phil,

 

 

 

Steel is the best material for a spring. Brass will work as it is springy but the springiness will disappear after a while but steel will not. I use brass emergency collets and they die after a while and need to be "restored". They are good for 2 "restorations" and then it's the scrap barrel. I have yet to trash a steel emergency collet because of the lack of springiness.

True...and like all springs, the clamps will eventually fail from fatigue after countless opening and closing, but with the total range here being relatively small, they can last a long time.

 

-john

[Phil Hackett]

John,

 

Steel has more "give" if you're going to occasionally stretch them beyond their designed size.

 

A properly designed spring won't fail unless it is used beyond its designed capacity. Think of valve springs in an engine.... they go hundreds of millions of cycles without fail......

[havlicek]

John,

 

Steel has more "give" if you're going to occasionally stretch them beyond their designed size.

 

A properly designed spring won't fail unless it is used beyond its designed capacity. Think of valve springs in an engine.... they go hundreds of millions of cycles without fail......

 

Yep...understood Phil, but all metal (includiong steel) will weaken with time as it flexes.  Certainly steel is a better choice than the other non-ferrous choices.  I have to believe that it isn't used much for this simply because it's more difficult to machine, even though aluminum does some stupid/weird stuff when you work it.  

 

-john

[crazyphysicsteacher]

What if there was a change to the design? Eliminate the hole cut to make it a spring and more of two jaws that pivot over a center pin with a single bolt to bring the ends together. It could be like a test tube holder that has the three fingers but the jaws would replace the fingers. I think this may last longer and may be worth the cost. Even starting with the already designed holder and modify it front there. Yea or nay?

[havlicek]

...maybe.

 

-john

[Geary Carrier]

Hi John,

 

I was looking at the clamp design and decided to try a different method of attachment, just for kicks. This method has probably been used before but I decided to give it a try anyway...

 

The requisites for the clamp were low cost, durability, ease of machining, one size fits all and something that even I could make. The example shown below is the first prototype and is pretty rough. I found that the clamp will hold various crown widths effectively. The armature clamping shelves are too big in this example and need to be reduced in size to prevent interference with previously wound poles as you work your way around the armature.

 

The clamp is made of 6061-T6 aluminum which I had lying around and like to use for prototyping. You could make it out of whatever metal or plastic that you wanted but for this design the aluminum works as the clamping forces needed to hold the armature in place are low.

 

I apologize for the quality of the pictures, still working on how to use a camera...

 

This shows the two spring loaded rotating jaws with attached mounting post...

 

 

This is a shot of the armature clamping shelves that need to be reduced in size...

 

 

This is a narrow crown armature from Bill Bugenis, he gave me three of these for free with a small order of commutators. Thanks Bill...

 

 

This is an old 26D armature...

 

 

This is a wide crown armature from a current day RS-380SH  Mabuchi, destined for a future 36D motor build...

 

 

I will start on a second prototype as this version is a tad more complex to machine than I had hoped. The next version will be simpler in design and construction.

 

Thanks,

Geary

 

 

[havlicek]

Hi Geary,

 

    That's really thinking outside the box.  That sort of approach would give maximum unrestricted access to the pole being wound, and since it's using the gaps between poles rather than the poles themselves, isn't affected by the diameter of the arm.  The only thing that would worry me from *just looking* at it, is that I put a lot of tension on the wire while winding...often just short of breaking the wire.  With the larger gauge wire, that means a LOT of tension, and I'd worry the arm would pop out of the clamping fixture.

 

-john

[Coal Train]

With all due respect I agree and I'de be a bit concerned with the tips pulling out.
But it would be a dream to use.

[Geary Carrier]

Gentlemen,

 

I just did a pull test, thanks for bringing this problem to my attention, with double (#25) wire. This is the biggest wire I have on hand so I had to double it to approximate a large gauge (#22) wire.

 

I used the wide crown RS-380SH Mabuchi armature shown above which affords the least amount of armature clamping force that this clamp design can provide; the wider the crown the less available clamping force. I just wound a few doubled turns of (#25) wire on the outside of the current armature windings and pulled.

 

I was able to break the two wires pulling parallel to the axis of the armature shaft. This design clamp offers the least clamping force in this "sliding direction" and the greatest clamping force in the "twisting direction" which would be pulling the wire perpendicular to the armature shaft.

 

Forgot how strong annealed copper wire this size can be, it wore me right out...

 

 

Thanks,

 

Geary

[havlicek]

Good to know Geary!  Again, my take was just from looking at it and it seems that looks can be deceiving!  Keep us posted as you go, I think others may be interested in the results, as the type clamp I see everyone use is basically unchanged in 50-60 years.

 

-john

[Coal Train]

Great test great result

[Coal Train]

I agree John. It's a sickness for sure

[Rick]

John has educated me about clamps too. I used to make them at the dia, but now have the capabilities to make them a tad over center and any diameter, so the arm needs "dropped" in.

[olescratch]

Rick, you still making winders?  If so, then how would a person go about obtaining one for future use?

[havlicek]

Rick, you still making winders?  If so, then how would a person go about obtaining one for future use?

 

 

...well, simply messaging usually works!  BTW, I also have a dandy static-balancing jig Rick made for me, and I use the living daylights out of it all the time.

 

-john

[Rick]

A pm works best for contact.....Yes, I can make them still. Nothing made up in advance, as ordered. 

 

John H., I just found a few pieces of that thick corian™ I used to make your static balancer and was thinking of making a few for Ebay..........(must be ESP)

[havlicek]

Hi Rick,

 

     That balancing jig is aces.  If such a thing can be worn out, I'll be the one to find out because I use it so much!  

 

-john

[havlicek]

Well, Geary sent me one of these to test and I am surprised at how well it worked.  I was thinking that exerting pressure inside the pole gaps like that would/could distort the crowns, but I did a bunch of tests and measurements and had no problem at all.  It takes surprisingly little force to hold an armature securely, and you can almost just turn the bolt by hand to get enough holding power.  Actually, a thumbscrew might even work instead of a bolt (?).  Looking at the clamp, there's a lot more work involved with fabricating it than a typical clamp, but it's about as close to a one-size-fits-all solution as I could imagine.  I was able to clamp everything easily from an old Mabuchi 16D/13UO arm to a 36D arm, as well as most all moderrn arms and it holds them all securely.  

The only things that might occasionally come up are:

1)Some armatures that have narrower pole gaps don't have enough width for the clamp "hooks" to fit into.  I found this on only a couple of types that I have here (like the Chinese 16D arms).  I guess that using steel or something stronger to fabricate the jaws out of so the hooks could be thinner might work, but that would add more difficulty to fabricating.

2)The "hooks"...the part that grabs the pole edges, come close to the coils on some "fuller" winds.  They didn't seem to actually touch or harm the coils, but it looks like they *might* on some winds.

In short, this is a very good design and works across a wide range of armatures!  

 

-john

[havlicek]

I forgot, here's a pic of the clamp mounted to one of my cranks.  The gap between poles for this arm is close to being as small as the clamp can manage as-is, which is good for the majority of arms a winder might encounter.  Again, the clamp doesn't rely on fitting the diameter of the arm, only the pole gaps, so it will work for all sorts and sizes of 3 pole arms.

 

-john

[Geary Carrier]

Hi John,

 

Nice job on the review and picture...

 

6061-T6 has about 60% of the yield strength of mild steel and in this configuration the "hooks" could be made even smaller without stretching and or breaking, since the amount of force to hold an armature is relatively low. A lower profile and width would also allow for more coil clearance and the fitting of very wide crown armatures.

 

This design is a bit more complex than the standard clamp but is achieved with simple machining processes, which even I can do...

 

 

Thanks,

g

[Racer36]

There is an old hand winder on EBay right now with 2 arm clamps. It is in a batch of old tools.

[olescratch]

I spent a little more time on a clamp idea that I came up with a couple years ago.  I started by taking the largest clamp that comes with the LaGanke winder, and traced it on a piece of aluminum stock.  I then used a band saw to cut out the piece.  I then cut the arm hole out.  I made a cut down through the center of the same hole, leaving approx. 5mm uncut.  From the top of the piece, I made another cut that intersected the first cut leaving me with a piece that had one half of the jaw, and another with the remaining portion that will be there to mount the handle.  BTW, prior to removing the "floating" jaw, a hole was drilled to be used as the clamping mechanism.  I then used a belt sander and file to remove enough material from the inner surfaces of the clamping area to allow clamping of the smaller dia comms.  I then drilled a hole in the "static" piece to allow for the connection of an old fishing reel handle.  Once I was satisfied with the fit of all these components, I decided to add a counter to help with my case of CRS (can't remember sh*t) lol!  An old counter that was once used to track the revolutions of a bike tire along with a leg to trip the counter were used.  After adjusting the travel of the leg to the counter, it was attached to the stem of the winder.  This is the 1st version of this winder, I have already come up with a few things that will make it better.  To make this usable for the different dia. comms., spacers placed on the clamp screw are used. 

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