70 replies to this topic

[Geary Carrier]

Duralco 4461...Oops. This was the first time I've ever used this epoxy and I should have degassed it first. Other than curing full of air bubbles it worked well wicking into the windings and Kevlar. I need to do a bit of experimentation with this epoxy.

 

[havlicek]

OK!  Now I have another element to look at.  I haven't been cleaning the coms prior to winding, this may be my turning point.  I'm still gonna turn on some classic rock though, minus the headphones lol!

John, the whole process of brazing the com tabs relies on current passing through the tab and out the associated com segment.  For the current path to work, there are two points on the com (the tab and the segment) where a good clean connection are critical.  Sometimes a little dirt or other non-conductive "stuff" on the tab or the com segment can stop the current from passing for a second...until it DOES suddenly pass with a "POP" (*as Geary said).  That "POP" is a split-second arc, and an arc is an amazingly efficient com-destroyer.  BTW, the silver/flux paste stuff I use is NOT a good conductor.  If you use it on the com tab (*along with some silver wire), you need to make sure it's not on the tip of the com tab where your brazing rod will make contact.

The other thing that can happen here because of a poorly cleaned com is for the current to pass through a different com segment (*if you're using a clamp on the com that contacts more than one segment) and then through the magnet wire looking for "the path of least resistance".  This can and will burn up an entire armature's coils PDQ.  If the tab and the com segment are clean, current will find the com segment you WANT it to pas through as "the path of least resistance", avoiding that whole problem.

***Because just "age" (*if you're using vintage coms) can cause enough tarnish/oxidation, or the manufacturing process can leave residue to prevent the copper from conducting electricity well, some sort of cleaning/prep of the com and com tabs before brazing is really important for the brazing deal to work well.

[Geary Carrier]

Received my little toy from Bill Bugenis. Got readings of .064, .064, .066.

Thanks Bill...

 

I only polished the comm as I don't have a cutter yet and I'm not sure how much cutting the comm will make in resistance measurements.

I'm going to leave the epoxy as is and send the arm out for grinding, balancing and comm cutting.

 

[havlicek]

Received my little toy from Bill Bugenis. Got readings of .064, .064, .066.

Thanks Bill...

 

I only polished the comm as I don't have a cutter yet and I'm not sure how much cutting the comm will make in resistance measurements.

I'm going to leave the epoxy as is and send the arm out for grinding, balancing and comm cutting.

004.JPG

008.JPG

 

 

Sweet Geary!  Cutting the comm can oftentimes even out small differences in resistance readings, even when the comm is clean.  ***Most importantly, cutting the com should cut "brush bounce", and the associated arcing it causes way down.  That will make for a cooler, faster, smoother running motor that draws less current as well.  The "Champion" type 36D comms have wide com slots, so truing up the com should also help with brush wear.

[Geary Carrier]

Sorry it took so long to get back to this motor...

 

Decided to can the original concept and try something a bit different. Put a C-can end bell on a Mabuchi FT-36 end bell so the motor could be used for drag or track.

 

Cut down a pair of 360 series Mabuchi magnets and epoxied them in the can.

 

This is after comm cut and balance.

 

Got a bit more to go...

 

 

[havlicek]

Nice Geary!  Using the original end bell as an adapter is a unique solution.  Wax on/wax off!  

[Geary Carrier]

Thanks John,

 

A bit more involved than adding D-can hardware to the original end bell, but just fun to do...

[havlicek]

...and more likely to perform better.  Adding anything to the original end bell still leaves potentially hot metal in direct contact with the equivalent of candle wax! 

[SpeedyNH]

that is seriously cool and so innovative!

[Geary Carrier]

Thanks Steve,

 

I'm hoping it is cool, as in not having the end bell melt off the end of the motor with the 22 turns of #25 on the armature.

[Ben Morrow]

Geary,

 

That is just Too Cool !!!  It's amazing what a person can do when you put your mind to it..    Very Nice job on the winds and the whole motor, keep um coming please!  Can't believe I didn't see this thread sooner....  

 

Great Job!  

[SpeedyNH]

well, for what it's worth regarding melting, that looks like a nice big com, and if you shunt the (good-quality) brushes there shouldn't be too much loss in the current path near the plastic. it seems to me that 22-25 isn't all That steep, and those are pretty long turns to boot- if it were like a 64 with cobalts, I'd start to think about it.

there's also elephant ears if it really gets bad, but it looks pretty darn good to me as is. you've done a very professional job.

I haven't wound any arms since the 60's, but I did get fairly decent at putting together G7 and Euro motors. look for the current to fall off during low-power break-in. I don't see the more experienced motor builders saying "watch out".

you might try putting a smaller pinion on it for its first road test to let it breathe a little. if it gets too hot then (or at break-in), then you gotta problem.

speedy

[Geary Carrier]

Thanks Ben,

 

A bit of persistence goes a long way...

[Geary Carrier]

Hi Steve,

 

I thought about adding shunts but I don't think they are necessary with this "mild" wind. If it runs too hot I will add a bit of cooling.

 

We will see what happens when we fire this thing up.

 

 

Thanks,

g

[Samiam]

Nice Geary!  Using the original end bell as an adapter is a unique solution.  Wax on/wax off!  

Great idea to mate old and new. Now there's a second life for those melted EBs.  

[Geary Carrier]

Great idea to mate old and new. Now there's a second life for those melted EBs.  

 

Gonna miss that acrid Delrin smell...

[Geary Carrier]

Finally got this motor finished...

 

Pulled about 6 Amps @3V on initial startup. After about 5' it was down to 3 Amps @3V with a noticeable increase in revs. Did a couple of very quick blips to 12V and it pulled about 8 Amps with instant throttle response. Very little arcing on the comm and it was surprisingly cool running. The couple of very quick blips produced an enjoyable piercing whine.

 

From initial impressions this motor would work fine for drags or track. Should be fun, or at least a handful, in an angle-winder track car.

[Half Fast]

12 volts X 8 amps= 96 Watts

 

For us guys running FK motors where 0.5 amps is the norm. Yikes.

 

"Should be fun, or at least a handful, in an angle-winder track car." Yup!

 

Have fun

 

Cheers

[Geary Carrier]

Added a flux yoke from a 360 series Mabuchi to help with magnetic leakage through the can walls which will improve torque and reduce current draw, this is not a large effect but is worth a bit of performance.

 

 

[Geary Carrier]

Made up a fixture when reducing the height of the magnets for this motor by 30 mils. Ceramic magnet dust can make a very large mess and I also wanted something to hold the magnets fairly square when they were sanded down. Used 40 grit first and finished with 120 grit. The interesting thing is that almost every bit of magnetic dust was sucked up onto the magnets in the fixture. Pulled the magnets with attached dust out of the bottom of the fixture and rolled them in play dough and received a nice set of thinner clean magnets, without a giant mess.

[SpeedyNH]

break in sounds good to me.