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A G20 that won't get too hot :)


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#1 havlicek

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Posted 14 February 2018 - 07:10 PM

A recent thread about this type got me thinking about hot winds and timing.  The "20" has been a favorite of mine for a long time, and to me, it is the perfect combination of high-end performance and reliability.  With the arrival of some Champion C cans, I thought this would be the ideal time to dig-in.  So I scrounged-up a set of Mura Magnets...nothing special, and removed the can bushing, substituting it for a 2mm x 5mm bearing.  The end bell will be a later Mura, again, nothing special at all.  The aim here is to duplicate (*or better) the performance characteristics I remember.

IMG_2487.JPG


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John Havlicek




#2 Geary Carrier

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Posted 14 February 2018 - 07:41 PM

Now that ain't no soup can...

 

Sweet


Yes, to be sure, this is it...


#3 Pablo

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Posted 14 February 2018 - 08:30 PM

G20 arms were always good performers and still available today.

Recent SB "fake news" "drive by media" press alleging they "run hot" is pure bunk


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Paul Wolcott

#4 Robert BG

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Posted 14 February 2018 - 09:02 PM

G20 arms were always good performers and still available today.

Recent SB "fake news" "drive by media" press alleging they "run hot" is pure bunk

LOL, go ahead and put a 38-40* g 20 arm in a Cahoza or koford tin can and run a few laps on a stuck King with the trigger pinned in a wing car and come back and tell me how "cool" it runs for you ;-) A 20-30* timed arm in a Champion/Mura can from years ago is a different animal and is like comparing apples to oranges.Hell go ahead and strap a 11 tooth pinion on it too while you're at it.

 

Or is the fact that high timed motors run hotter then lower timed of the same wind "fake news" ???

 

John,those are nice cans,I used to run them over the mura's of the time.


Robert Fothergill

#5 Pablo

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Posted 14 February 2018 - 09:19 PM

Robert, who would ever put a G20 arm in a modern G12 setup? That would be stupid.

Where you got that idea didn't come from me, I assure you.

 

I'm looking at your posts, so don't say you didn't invent this, because you did.

Read your own posts. A guy asked for gearing advice for a G20 motor and you went off on a tangent about G20 arms in modern G12-type setups. You are the one who is confused. Not me.


Paul Wolcott

#6 Robert BG

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Posted 14 February 2018 - 09:41 PM

Last time i checked a C can was a C can.........Or are you going to tell me that isnt the case?Or are the cans I use to build a group 12 mysteriously different then a G-20?

 

Please by all means enlighten me as to the difference between a group 20 C can and a group 12 C can??


Robert Fothergill

#7 Pablo

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Posted 14 February 2018 - 09:57 PM

A G20 arm is a completely different animal than a G12.

The stack length, wire size and turns are way different.

Just because the cans may be of similar, or same size, means nothing.


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#8 Robert BG

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Posted 14 February 2018 - 10:37 PM

A G20 arm is a completely different animal than a G12.

The stack length, wire size and turns are way different.

Just because the cans may be of similar, or same size, means nothing.

LOL I never said they were.I actually said they are different but you seem to have missed that.

.But still I'm waiting to hear the differences in the cans?lol

While you're at it please tell me other than length what the difference is in mags between a G-12 and G-20? Oh and btw You can and build a 12 that HAS the LONGER mags ;-)

 

 

Seriously, if you are buying a C can G 20 these days that ISNT a drag motor you're going to run the SAME can and mags that are used in 12's-Spec 15's or a 20.But its clearly obvious that you dont know or understand that.So lets ask John what his Mura mags were used for?

 

Seriously there is a reason why 30* timing is about the max you want to run in a G 20 thats going to be flogged on a track and I'll give you a hint,its because the arm is too hot a wind with more timing for ceramic mags.

 

Seriously there's a reason why Koford only sells arms  Group 20 over 30* timing for Drag racing these days and if you'll go REREAD  Mike Swiss's post where he AGREED with me you might actually understand.

 

If you'd like I can demonstrate with pictures for you.I'll be more than happy to take the mags out of my stash of motors from the 90's and todays stuff and show you they all interchange.I have a 90's Mura off the shelf group 20 and plenty of new stuff that I bought to build 12's with.

 

 

Now John please get back to the build,sorry I bit the trolls bait.


Robert Fothergill

#9 Pablo

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Posted 14 February 2018 - 10:51 PM

I apologize to John as well for the drift. Robert, true I trolled baits :D

But in case you missed it, the title of the thread is, in fact, a jest in itself.

 

Robert, a good amount of your info I agree with, and I'll admit you are more fun to read and joust with than the guy who put a G20 motor in a G27 chassis. :D Plus I'll give you extra kudos for standing your ground and fighting rather than jousting then fleeing  :clapping: 


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#10 havlicek

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Posted 15 February 2018 - 06:45 AM

OK...now that the dust has settled  :)

 

 

 

LOL, go ahead and put a 38-40* g 20 arm in a Cahoza or koford tin can and run a few laps on a stuck King with the trigger pinned in a wing car and come back and tell me how "cool" it runs for you ;-) A 20-30* timed arm in a Champion/Mura can from years ago is a different animal and is like comparing apples to oranges.Hell go ahead and strap a 11 tooth pinion on it too while you're at it.

But that right there is the point.  I personally don't see the point in pushing the timing to where the motor becomes less useful, and it's a rare thing that I time ANY armature more than 15-20 degrees advance.  So...you're setting up a scenario that wouldn't happen Robert.  In the other G20 thread, I even mentioned that I tried both Mura arms, and couldn't see the point in the higher-timed (+) arms.

So (*in my best Henny Youngman)..."I say to the doctor, "hey doc, my motor gets too hot when I time it high", so he says "so don't do that".  :D  With all the variables that can be tweaked, including gearing, leave the timing below 20 degrees and tweak the other stuff!

Another way of putting it, abandoning the idea of G20 altogether because a very high-timed G20 isn't suitable for a particular scenario seems to be missing the point.  A reasonably-timed G20 should be the obvious choice.


John Havlicek

#11 Robert BG

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Posted 15 February 2018 - 09:22 AM

Pablo I was looking for my calipers and camera but thankfully I read your last post first lol  ;)  I even dug out a collection of cooked arms :D

 

John,I think the 20 is a great motor too,it truly shows how timing and winds are a balancing act in these little motors,probably better than any other wind.Too much of one and you'll most likely go backwards.The problem is 98% of today's Group 20 stuff is aimed at  drag racers these days.

 

A few years ago when i got back into slots wing car bodies and chassis design had completely changed from before.I actually put a few 20's together thinking they'd be a good car to test bodies and get up to speed without beating up on my good gear.Again I assumed that since the new 12's and Int 15's were running upwards of 44-46*'s that 38* was good to go.I never thought to look back at what we ran in the 90's and just ordered a bunch of gear.Needless to say they got hot enough to spin pinions soldered on with 60/40 solder in about a heats worth of running.The Mura arms I then tried didnt have the issue and ran about 2-3 tenths slower on average but where about 4 off of a top lap with the high timed motors.Considering they were from 93-95 and needed to be serviced I was impressed.I can only imagine how the old Mura blanks would perform if they where wound better.I seem to recall John saying they are hard to wind because of the blanks design so that probably has a lot to do with it.But seriously they look like a 5 year old wound them lol.Even the hand wound arms back then are sloppy compared to todays stuff.

 

On a side note I once told a friend of mine who is a electrical engineer in Bulgaria about the winds and dimensions of a one motor open that I was putting together.He looked at me strangely,thought to himself for a minute before asking me if I had put one of these things together before.He honestly thought I had wasted my money on a "custom wind" that wasnt going to work.He didnt know anything about slot cars so when i said custom wind he thought it was something I dreamed up and had done as a experiment.Being the good friend that he is,he finally piped up and said i should expect to see the magic smoke come out.He had run some numbers and honestly expected it to be essentially a dead short LOL.He couldn't believe how the things ran and he even asked his dad who is also a EE and head engineer at a Nuke plant and his response was the same lol.

 

John,I know its not a winding thread but if I unwound one of my cooked Mura 20's how hard would it be to rewind one?Can you put a new com on,or dont you recommend using used arms for rewinds?


Robert Fothergill

#12 Pablo

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Posted 15 February 2018 - 10:09 AM

Here's one I built a while back, a Champion G20 arm, runs cool as a cucumber

 

http://slotblog.net/...20-c-can-motor/

 

My Batmobile also has a Pablo built G20 arm motor and runs cool

 

http://slotblog.net/...lewinder/page-3

 

Back to you, John :)

 

 


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#13 havlicek

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Posted 15 February 2018 - 10:13 AM

Hi Robert,

 

 

 

John,I think the 20 is a great motor too,it truly shows how timing and winds are a balancing act in these little motors,probably better than any other wind.Too much of one and you'll most likely go backwards.The problem is 98% of today's Group 20 stuff is aimed at  drag racers these days.


That's probably because of several factors, but inappropriately timed arms sure isn't going to help.  The thing is, if you put a higher timed 20 in a setup and car and then a more moderately timed 20 in the same setup and car, the results could be predictable.  Like I said, there are many many other variables that can come into play than timing.

 

 

 

I can only imagine how the old Mura blanks would perform if they where wound better.I seem to recall John saying they are hard to wind because of the blanks design so that probably has a lot to do with it.But seriously they look like a 5 year old wound them lol.Even the hand wound arms back then are sloppy compared to todays stuff.

 

I don't think there's any magic to those old Mura blanks, other than good lamination steel and .007" lams.  They had a ton of wasted real estate between the thick legs, thick crowns and crazy thick diagonal supports at the shaft hole.  A more modern design out of good .007" material would be likely to produce an even better performing 20 armature.  Having said that, I am sure I can make a better 20 arm using .014" lams and keeping the timing reasonable.

***It may not always be the case, but there IS something of a "follow-the-leader" mentality in slots.  Whenever someone starts winning races, others start the "I'll have what he's having" thing rolling.  Consistently winning racers get to that position because of a whole boatload of factors, not the least of which is how well they drive, and that applies from the retro classes all the way up to the tippity-toppity bleeding edge stuff.


John Havlicek

#14 Robert BG

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Posted 15 February 2018 - 10:17 AM

Pablo,what are those elephant ear things?Is that just another movie themed build for Dumbo   ;)


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#15 Jairus

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Posted 15 February 2018 - 10:25 AM

Nice project John!  I saw you had three cans there.... are you selling them all once they are built-up?
Not that I need one, but my interest is piqued here. 


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#16 Jairus

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Posted 15 February 2018 - 10:32 AM

By the way... here is one of those motors that I put into one of Ralph's projects back in 2012.
Bought the motor new in 1991 btw.
The motor mount was soldered to the can and then bolted to the weird plastic chassis. (Gp12)
Of course I took the magnets out before doing that.  The rear axle is cut and soldered to the can, making the can a structural part.

2vM6KHbLxubMLY.jpg

 


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#17 havlicek

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Posted 15 February 2018 - 10:44 AM

Nice project John!  I saw you had three cans there.... are you selling them all once they are built-up?
Not that I need one, but my interest is piqued here. 

 

I have four Jairus.  I sell everything and keep nothing.  :D


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#18 havlicek

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Posted 15 February 2018 - 02:55 PM

...and BAM!  The magnets are epoxied-in to the can with a slug (*measuring around 1140 or so without a zap, even after curing in the oven), and the arm is done, measuring around .140 ohms per pole.  I'm not sure whether I'll have the arm taken down all that far, but I think most of the Muras finished at around .513" OD.  ***Most important here is that the timing is set at 17-18 degrees advance CCW, which is right where I usually am for about any wind on any stack for any motor unless people ask for something more extreme.  Will the motor be fast?...oh heck yes.  "Fast enough"? sure...but it shouldn't be a motor that you can't drive hard without worrying about things going south. 

IMG_2489.JPG IMG_2490.JPG

***Oh and, about any motor will be stressed in a car and on a track where it's basically full-punch and no driving.  Having said that, with the right gearing..."this one will kill"!  :D


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John Havlicek

#19 Jairus

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Posted 15 February 2018 - 04:31 PM

Looking Good!  :good: 

I believe you have the correct end bell too.  (Or, close enough.)
2vM6KHtgxubMLY.jpg


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#20 havlicek

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Posted 15 February 2018 - 04:53 PM

Looking Good!  :good: 

I believe you have the correct end bell too.  (Or, close enough.)
2vM6KHtgxubMLY.jpg

 

Weeeell Buddy.  I MUCH prefer the Mura I showed to the ProSlot pictured in your post, but we're otherwise on the same page!  :D


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