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Another step up for a minican


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#1 havlicek

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Posted 28 April 2018 - 07:19 PM

After installing a new oilite "keyed" to the endbell, and a can bearing, I wanted to close-up the magnets in this motor. With the ceramic magnets, I see around a .540"+ hole in this motor. 

 

So I made a pair of .004" shims, and epoxied the shims and magnets into the can and then honed the setup to .530". A re-zap brought the magnets right back, so I wound up a 50t/29 with what is (for me) crazy advance of 35 degrees CCW. I'll have to wait to epoxy it and cut the comm until the new batch of 4461 comes, but I think this will be a very fast motor.

IMG_2719.JPG


  • Pablo, MSwiss, boxerdog and 4 others like this
John Havlicek




#2 Ben Morrow

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Posted 29 April 2018 - 05:14 PM

John,

 

What do think the bottom line will be on shimming the mags: better brakes, quicker response, maybe both? It will be cool to find out what will happen heat-wise, too.   

 

Arm dia .518? Nice wind on that arm. Purty as always!  :D Just hope mine turns out half as nice!



#3 swodem

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Posted 29 April 2018 - 10:26 PM

John,

When you say very fast, how do we get an understanding of just how fast:

Faster than PS4002FK (I hope so!)
Faster than X12 minican?

I’m interested in how good these little motors can actually go...

Steve



#4 havlicek

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Posted 30 April 2018 - 05:41 AM

What do think the bottom line will be on shimming the mags: better brakes, quicker response, maybe both? It will be cool to find out what will happen heat-wise, too.   

 

Arm dia .518? Nice wind on that arm. Purty as always!   :D Just hope mine turns out half as nice!

 
Yes, better brakes and better acceleration ("response"), Ben. Heat-wise, it could mean running a little warmer, but not necessarily.  That's why we test!  :)  The overall effect will be that of having stronger magnets, because moving the permanent magnets closer-in or further-out from the armature even small amounts makes significant changes on the strength they exert.

Don't get frustrated when winding. It will take a while for things to start working well... to get consistent, tight, and neat coils. The biggest issue with all this is people jumping-in and then losing enthusiasm when it doesn't happen right away. If you stay with it... it will happen.
 

When you say very fast, how do we get an understanding of just how fast:

Faster than PS4002FK (I hope so!)
Faster than X12 minican?

 
 Hi Steve... this is an "X12" minican!? I *think* the "X" just means higher timed, and those go way up to (I think) maybe almost 50 degrees or so. So this arm (even though it's "radical timing" compared to what I've usually done) is actually more "conservatively" timed than some? Many? Most? "X12" arms. Higher-timed arms generally run faster in the direction they're timed to run and worse in the opposite direction, with some other acceptable tradeoffs in brakes and heat.  

The actual wind here is the same... 50t/29 as any other "12," but the minican can't (of course!) use a .440" long stack. Here, I pressed a .350" long stack, so the same 50t/29 wind here will have lower resistance than it would on the longer stack. I could have gone with as much as a .400" long stack and still fit it in the same setup, but I think the .350" makes sense here, and I don't know offhand what length stack the X12 arms made for the minicans made by Koford and Pro Slot use.

I upped the timing here because people seem to "like" and regularly run higher-timed arms, and the strange large diameter C-can arm I made for Dave Parotta was timed at 42 degrees advance. Even the Puppy Dog arms are high-timed by my standards, and people seemed to like those too, but I come from a place where I see 20 degrees as "high timed."   :)  I guess, I'll start upping the timing and see where things go. Of course, when I get asked specifically to build and wind an arm with "whatever" timing, I do that anyway.

As for "I’m interested in how good these little motors can actually go...", in many ways, the minicans are no different than any other DC motor. As they go faster, they last less long. I've done these as hot as #26 and even #25 wire, and that's very fast. Some #26 wire arms reportedly were run over in Europe using the Hawk setup (probably a good choice for the extra cooling from both the can and longer endbell tower) and were "right there" with some very expensive motors... for a while. At least one had a lamination failure (probably where the stack had been drilled for balancing), which is not all that uncommon for really fast arms. Of course, if allowed, the nifty JK aluminum endbell is probably a very good idea for the really fast stuff when it comes to the minicans. 

 

So, the minicans can go as fast as you're willing to allow them to and accept a higher failure rate... the same as for C and D-can motors.

There are of course nifty Koford and Pro Slot handwound 12 arms available stock... and you can get minican arms all the way up to around 15t/24(!), but those are "drag" arms for sure.


John Havlicek

#5 havlicek

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Posted 30 April 2018 - 06:12 AM

... and as long-winded as my post above is, I forgot to add an interesting little tidbit about this motor. 

 

I have seen ceramic setups for these minicans where the magnets had obviously been honed, and noticed that the honing "pretty much" took material out of the center of the magnets' inside arc. The same thing happened with this set-up, and that leads me to believe that the magnets' inside arc is slightly wider than that of the armature. I guess that this normally makes for a "softer" effect of the magnets on the arm.. .sort of the way very thin magnet tips can. On a set-up like Dave Parotta's C-can, where the magnets are radically honed way out, the magnets' gaps are basically exactly the the same all the way around the armature, even if they weren't beforehand.


John Havlicek

#6 Bill from NH

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Posted 30 April 2018 - 06:32 AM

Today's magnets are much more uniform than they were back when I ran C-can wing cars in the '70s and '80s. It was not uncommon back then to have to straighten both magnet faces and backs. Diamond hones had not yet been created either.


Bill Fernald
 

I heard they weren't going to make yardsticks any longer.


#7 havlicek

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Posted 30 April 2018 - 06:42 AM

That's seems like it may generally be true, Bill (although saw cut magnets certainly from the 1980's seem pretty "perfect") from what I've seen, but I'm not sure how that matters at all here. The inner arc of these magnets... their "face," seems to be purposely wider than the outer edge of the arm.


John Havlicek





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