3573 replies to this topic

[Phil Irvin]

john i got the twine to tie the arms when i finished so right away you know kid with new toy had to try it out right away and i tried to follow you directions but i think somthing went wrong any thoughts

Talk about an AMP sucker!!! Some torque, very low RPM.... noooo brakes.

Phil I.

[havlicek]

A cut-down Mura C can with a #26 wind. First try seems promising.



-john

[Champion 507]

Looks mighty handsome Mr. H.

[havlicek]

Thanks Doug

-john

[Champion 507]

John,

Any chance of a quick recap of the build?

Thanks

[Howmet TX]

This may have come up before and I missed it but....

Is there any point to trying to fit a new comm on a nice old arm? I have quite a few tasty old Muras, etc., with blown or very worn comms, mostly tied but some not, and I often wonder if there is any mileage in gently prising the windings off the comm tabs and resoldering & tieing them to a new comm.

[tonyp]

East coast motor builder supreme Big Jim Greenaway would change comms on armatures that were really "magic". He did a few for me when I used his stuff and they ran just like new.

[havlicek]

Hi Doug,

I've been toying with the idea for a while of a 1/32 full-sidewinder and a while back I got a few lovely 1/32 thingie bodies from John Dillworth. It seemed to me that there's a pretty significant amount of room to cut down C cans and with this one, I can get somewhere around a 2 7/8" width with modern tires. I did this motor as a test to see where things go, and while not a barn-burner...it sounds pretty fast. I had done a #28 wind for this setup back a ways that WAS a barn-burner and think somewhere between the two would be ideal. Anyway, I can either use a little narrower rear tires or cut the can down some more and tuck it all under the body sidewinder. Then it's just a matter of getting a hold of the right gears.

This arm has an overall length of almost exactly 1.00" and I cut more than 1/8" from the can. I forget the Can/endbell are modern Mura, arm and com were salvaged from an older Mura I got in trade.

-john

[havlicek]

East coast motor builder supreme Big Jim Greenaway would change comms on armatures that were really "magic". He did a few for me when I used his stuff and they ran just like new.

I can't imagine doing that kind of microsurgery! That's pretty freakin' amazing.

[Champion 507]

John,

Did you shorten the stack any? Remove laminations?

I've got some Mura Wasp arms that I've unwound and want to do something like what you've done here.

East coast motor builder supreme Big Jim Greenaway would change comms on armatures that were really "magic".

I haven't changed out any comms yet but I've thought about it and I'm not afraid to try it if I think the arm is worth it.

I have changed out arm shafts on modern Super 16Ds. I got a bunch of modern 16Ds off ePay and there were several Supers that ran good but someone got carried away with a Dremel and messed up the shaft ends where the pinions go. Some time ago had I salvaged anything and everything I could from another group of arms I got including some good arm shafts and I was able to save these Supers.

[havlicek]

Hi Doug,

Yes, I did remove lams. Of course after doing so you need to insulate the stack end (I use epoxy). I also use a very small diamond point in the Dremel to round over or ease the edges of the stack ends before insulating them to help prevent shorts caused by those edges cutting through the magnet wire's coating.

Anyway, I'm going to cut this can further and do another arm with a .350" stack. Looking at the can/endbell/arm/comm, it seems as though that's about as short as is feasible without cutting the magnets. Whether it will work or not is a question.

[Prof. Fate]

Hi,

One of my personal jokes... knowing I am not fond of motor rules, is that I have a 1/32 Euro car I did backin the late '70s with a "P" can in it that is a quarter inch shorter than it should be. But it has a TAGGED group 12 arm in it!

Fate

[havlicek]

I cut down the can some more... pretty much as far as it can go, and the stack is now somewhere around .340".

At this point, the comm is almost as long as the stack and the motor will definitely fit sidewinder in a 1/32 thingie even with fat tires. It's a pretty potent sounding little sonofagun so I'm going to keep the setup and add ball bearings to both ends and maybe wind another alternate arm for it.

I have a question for those "in the know"... should the magnets stay full length, or should I cut them down as well. It seems to run really well as is.

[havlicek]

I did some more fiddling with the mini-C (sort of my "walnut" motor) above today.

After running it for about ten minutes at various voltages, I took it apart and recut the comm (it really still looked new), checked the balance (I was able to get it a bit better), and set it up for almost zero endplay. After reassembling it and running it for a couple of minutes at 2 and then 4 volts, I let it spin all the way up and it sure does sound healthy!

The arm was done using a vintage Mura .007" blank I salvaged and shortened way down, as well as an old Mura comm I salvaged and cleaned up. This #28awg wind draws around 2 amps (no load) and doesn't get particularly hot at all in testing.

One thing I did notice is that apparently a lot of current is passing through the springs because insulating them seemed to slow the motor down. I have to assume that the motor will run even better with some shunts installed, as well as ball bearings. This little guy has been a fun project.

[Champion 507]

John,

Once again, two thumbs up. Nice job!

[Jairus]

Hey John.

I built one of those (way cut down C-can) for my personal wing car. Runs great until it gets hot... then the magnets start losing their edge. Arm is tagged GP27 and I think it is from Pro Slot. Going to pick up a set of HEQ magnets (PS-907) some day for the next attempt.

Can't wait to see your chassis build for the 1/32 sidewinder!

[havlicek]

Hi Jairus,

Hey, thanks for the info... your project sounds very similar to mine, but a tagged G27 arm is long. How the heck did you get it in a short can? Also, that may be a bit hotter than my arm but it's hard to tell since they're all pretty hot when the stack gets as short as mine is. Did you cut the magnets also? I asked about that here and got only one reply by PM and don't have any experience with these short setups and how cutting the magnets would affect things... more RPMs/less brakes?.

On the car itself, I'm certain it will be a wire-only perimeter chassis that will be close in general style to the one Rick showed recently. These were the kind I ran when I got into sloots again for a short whgile a couple of decades ago and they were a blast, but I always used G20 motors. The car will be built VERY light and I'm thinking of two basic scenarios/configurations:

1) Having the motor situated in the traditional full-sidewinder position, with larger gears if I can find them (?) to clear the rear axle tube.
2) Installing the motor on its "side" with a new set of tabs for the leads on the "bottom" of the endbell and then using regular 64 pitch gears at a bit over 4:1 to start.

For sure, having the motor installed "normally" would put the CoG lower, but I still think that using Faas or equivalent gears would be a good tradeoff with the motor on its side. Can you give me any more details or pictures on how you did yours? Even though I guess yours was an anglewinder, I'd be very interested in what you did.

[Jairus]

The arm was short. Not sure what it was originally designed for but my thought was a strap motor...
At any rate, I shortened the Mura can about 1/8 of an inch. Also opened up the holes bigger and installed ball bearings. The magnets were standard white dots, narrow. Not enough "push" for the wind so moving on up to the High Energy Quads next... when I get the time and $ to order the parts.

Right at the moment, I am having fun with Flexi racing.

[havlicek]

Arm #2 for my "walnut motor". This one was done on a new Mura blank and com. A #26 that's pretty darned zippy, showing a current draw of just around 3 amps with no break-in. I think this is the arm I'll keep for a while with this setup. I have some tweaking to do to the can/endbell, but this should provide plenty of "oomph" for a 1/32 sidewinder thingie.

[wilbor56]

John:

How about insulating the springs and shunting the brushes, that should take care of that problem with heat on the springs and this will also help retain the spring strength.

[havlicek]

Hi Bill,

Yes... both those are in store for the motor as well as ball bearings on both ends.

Having spent some time breaking-in the motor over the last day, I'm even more pleased about the way it runs and feel good about such a small motor's usefullness. Actually, I'm going back and forth now between the idea of a 1/32 and a 1/24 car for this motor (either one built light and geared to rev) since it seems to run so strong. I'm not sure a 1/32 car won't be overpowered with this little walnut???

[wilbor56]

John,

Here is a thought for your minmight: how about a retro build of a old Triumph Spitfire? You will have to build the chassis but I think this would be a good fit for that little brute.

Don't mind me, have not had first cup yet and eyes are not open...

[havlicek]

Hi Bill,

Interesting take on the retro thing. Usually people are putting modern throwaway motors in chassis that recall the '60s. Putting this little guy in one of those chassis (even though it's a rewind and a cut down can with the right "spirit") would be cool... but probably not the best use of the motor.

I think this motor would do well in as light and strong a chassis as possible, high gearing for lotsa revs and with some sort of air control on the body. Truthfully, I always preferred the MG's looks to the Triumphs for some reason... but the Lotus 23s that Chris Clark and Jairus showed here recently are pretty darned nice as well!

[havlicek]

I pretty much finished my #26 awg "walnut motor". I added shunts and ball bearings (still have to insulate the springs) and I epoxied-in the magnets as the magnet clips were so short they tended to not sit straight in the can.

For comparison, I'm showing it in front of a regular-sized Mura C can. It's about .320" shorter than the stock setup or almost a full 1/3 of an inch, which is a LOT. I guess it's also a bit lighter as there's a whole lot of can not there anymore. There's plenty of room for air to circulate and it doesn't get very hot at all, still drawing under 3 amps. The motor sounds just great and it seems as though a can this short is a viable option, although it limits you somewhat as about any wind you put in there is not going to be very mild.

[Champion 507]

John,

Looks like you took a V-8 and made a V-6 out of it. But with it being a 26 wire short stack arm, it should have ALL the power you'll ever need. Looks like a sweet candidate for a drag car because of the weight loss.

I recycled a Mura Wasp arm one time and wound it with the same wind as a GP27 (38 turns #27 wire) and put it in a full length set up with quads like the one on the top of your photo and it turned consistent .865's on a full length drag track. It was in a lightweight chassis with a Lexan body. It's one of the most potent motors I have built so far. I have plans for a couple other motors that should surpass this one.

Keep on crankin' 'em out... the volts and amps ain't peaked yet!