" did I get screwed" follow up report

I read Johnc's thread about a leopard that did not run after he bought it. And I PMed him to see if I could buy the motor from him cause I use a Leopard 4074 in my P-mono, it's the very first FE motor that I ever bought, and I thought it would be good to have a spare. I burned mine up at the Michigan nats because the boat took a dunk but came back up and went on to get within 30 feet of the finish line......and stopped:huh: The batteries slid forward about three inches cause I didn't have them secured very well.

I have won a lot of races with that old Leopard so when I got back home, I set forth to rewind it and get it back into the action. I was able to put a good bit more wire into it as the Leopards are not very full from the factory. And of course I used good 200*C wire, so the motor can take a lot more abuse now and still come out ok. Had I done this before going up to that race, it would have made that finish line and then some, and still been ok, just hotter than usual. And to prove this to myself, at our recent Atlanta Model Boaters Grand Prix race this past July, I had the recently rewound Leopard back in the boat and running as good as usual. I normally run an ABC 1714-17-45 and that's fast enough to get me into trouble when the water gets rough. It will pull a 1715 but does get a little warmer, so I prop down to be safe and finish the race. But on the last heat of our race, I decided to see if the rewind was actually any benefit I was out of the running cause of a mistake or three anyway. So I put an ABC 1814-17-45 on it, HO LEE SHIP that turned it into a rocket! I don't know how hot it might have gotten cause I only made it 4 1/2 laps before I subbed it by being to aggressive, but man it was fun. I was all over the leader (Doug Smock) and he has recently motored up with a BIG TP replacing his old 1515 Neu.


So when John's post came up I figured this might be a good chance to get a spare. John's is an 82mm long version, vs my 74mm, but the extra length wont hurt anything in my boat, And the KVs are the same so if I did swap motors, I wont have to change props if I don't want to.

John agreed to sell me the motor cheap enough, cause it's just a paper weight to him now, I hope he didn't pay to much for it when he bought it. I got it in last evening and tore right into it and found the short right away Where the leg wire bundles wrap over each other on the rear of the motor. There was a little bit of black residue and two or three blown wires. And on the PTO side there was also a tiny spot with just one or two wires blown into. But what happens, when this happens, is that when a wire does get hot enough to burn the insulation off, then it also usually burns the wires that are pressing tightly up against it. And if those wires are on another leg, POOF! Now when the ESC is sending a positive signal on that leg, it runs into the short and either gets in the leg that has the negative side on it, or get into the OFF leg which is supposed to be sending back EMF the the ESC to tell it where the rotor is positioned. So either way the poor ESC can't figure out what to do, so you get the shuttering/ single phasing.

I'll post a few pictures as I go to try and show what's going on.

here's the short. not much to it but enough to confuse the ESC, also see all the room left unused in the slots. This is not only because it's a cheap motor but also has to do with the type of wind that this particular motor had. 1.5Y . It makes two passes through the slots on one side of the stator, but then only one pass on the other????? That leaves a lot of air in the slots which would be a lot better if they were full of copper. That would allow the motor to make a little more power but mostly allow it to handle and get rid of more heat.

"HO LEE SHIP", I remember saying that myself! Ampdaddy was bringin it!!:laugh::thumbup:

I didn't like that 1.5 wind, but I really wanted to keep the motor close to the 2200 kv so it would be an easy swap for my 4074-2200.

But none of the other winds avaliable for that motor are very close, at least the ones that OSE has were not. The Leopard motors website has been down for a few days and I could not look them up on there. But seeing as how the 3D wind was not to much off, the 2 Y was way to low at 1600, but by taking the 2.5Ys/ 1250kv, and multiplying by 1.73 (the difference between a D and a Y, with Ds being higher revving of the two) so 1250 x 1.73 = 2162.5,HEY NOW I can work with that one.

So I made up a "test bundle" of three wires to see how it might work out. KVs and all that calculating almost never work out very close to what their supposed to be, thus "the test"!

Well I'll be dern, 2160 kv is what it was actually doing. The math was right for a change! Now I had to make up some wire bundles for the real wind. I ran one wire through the entire wind to get the length proper. Then add a little cause you always need a little more. Then using a bunch of scrap ends and pieces, I stuffed as many strands as I could get into one of the slots. I'm out of the 27 awg that I like to use so I had to use my other spool which is 29 gage. That's pretty small but it just means I'll have to use more strands. BUT good grief, it holds 140+ strands, and that's not really packing it in either. You can never get as much in them while actually lacing it up because of the overlaps of the end turns get in the way. And with a 2.5D wind, I will have to make three passes through each slot. So divide 140 by 3 = 46.66666 but I'm gonna cut that back a little more so it wont be to hard to thread it all through there , and I'm going with 40 even strands. That will leave a little room but will be oh so much more than was in there to begin with.

And BTW, this is one of the reasons that you have to pay more for a NEU motor. There aint room in one of there stators to put even one more strand of wire! They are as full as they can get. With a TP, there is a tiny bit of room left, but I have not been able to rewind one of those yet. When you get all the wire out of them, the stator just falls all to pieces!


So I wound it back and it did get pretty full, but if I had to do it over, I would go with a few more strands, maybe 2-3 more. That doesn't sound like much but remember that each bundle goes through each slot three times, so it adds up. And that's just three passes, so imagine what a 6 or 10 turn wind would be like. Just one wire difference really adds up then. PLAN AHEAD is the key words here, and a little practice helps too.

I'll show a few more pics in the next post.

Here's the wind after getting it all in there and before pressing the ends flat. Not that you have to press them very much on a Leopard, cause there is always a lot of room left over in the back end of this brand of motor. This is a D so there is even more room because with a Y, you have the connection where all three bundles come together and are soldered and heat shrink applied and then this is pressed down into or on top of the wires.

Then after pressing the snot out of it, I actually enjoy doing that.

Then all back together and ready for testing.

Ya better stand back a little, ya never know if sparks are gonna fly or not! Hey, look at that, it WORKS!

I put the little flywheel on the motor shaft and run it checking the RPM with a photo tach. Then I have a battery tester plugged in to the pack so I get an accurate reading of the voltage under load. 33690 rpm divided by 15.57 volts = 2163.7kv.

The numbers worked out dead on the target RPM and I end up with a 2160kv. Only 40 shy of my 2200 goal but, It don't get much better than that.

Ready to do battle again in some lake across the southeast or maybe Michigan next year! Or maybe it will spend it's days it the "spare motors box" and the old faithful 4074 will never go up in smoke again. ............But I doubt it, I liked the speed that the 1814 gave me. I wonder if it would pull a 1815, or maybe a 1914. I think I smell smoke!

Damn, I though I knew something about this stuff until I read this thread. Great craftsmanship man.

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Originally Posted by stadiumyamaha

Damn, I though I knew something about this stuff until I read this thread. Great craftsmanship man.

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That's why we call him "Amp Daddy"!

Very nice Don!!

Don could write a book.

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Originally Posted by T.S.Davis

Don could write a book.

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LOL!! Terry, just like in the past some of your comments always cracks me up and this one might not be funny to others but it sure is to me. Maybe I just worked too hard today.

I am impressed Don. And now want to try this, lol. Well, I’ve wanted to for awhile but with this write up I feel I could. Thanks , Shawn

Mary me....

JK... Love your stuff.

Unfortunately, the goolrc 3670 motor will not accept the 1515 rotor :glare:.... it's windings could easily be compressed.

If you don't compress the windings like you do Don, don't the windings in air create more motor heat an decrease efficiency?

I'm tempted to start tooling parts like you to rewind some duds I have lying around.

What kind of press are you using, pressure?

If there is one thing I'm good at, it's tinkering like this.

I've got a lathe to make some tooling.

A big thank you for sharing your knowledge with us....just used to do this years ago with my slotcars motors.Gill

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Originally Posted by stadiumyamaha

Damn, I though I knew something about this stuff until I read this thread. Great craftsmanship man.

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Thanks

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Originally Posted by T.S.Davis

Don could write a book.

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HA!!!

I won't live long enough to write a book. It took me half a day to write these few paragraphs and add the pictures.

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Originally Posted by srislash

I am impressed Don. And now want to try this, lol. Well, I’ve wanted to for awhile but with this write up I feel I could. Thanks , Shawn

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If, When, you get serious about it, and get to where you can take one apart and get all the old wire out without destroying the stator insulation (I have a trick for that). Then the complicated part starts. And when the disassembly doesn't go so well and you really mess up the stator insulation. I have just recently figured out how to strip all the insulation off of the stator, and then powder coat it back. And the powder coat seems to do a better job of protecting the wire than the stock stuff does.

If you do try it, let me know and I can do some more post on how to go about making the wire bundles, turns, and the actual threading of the stator slots.

Gee Whiz Mr. Don, I should have just asked how much to rewind for me lol. Just kidding. Glad everything worked out for ya. Looks like I did get took on that motor.

John

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Originally Posted by ray schrauwen

Mary me....

JK... Love your stuff.

Unfortunately, the goolrc 3670 motor will not accept the 1515 rotor :glare:.... it's windings could easily be compressed.

If you don't compress the windings like you do Don, don't the windings in air create more motor heat an decrease efficiency?

I'm tempted to start tooling parts like you to rewind some duds I have lying around.

What kind of press are you using, pressure?

If there is one thing I'm good at, it's tinkering like this.

I've got a lathe to make some tooling.

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Why do you want to put the 1515 rotor in the gool? Ya know, you can make a fixture to put in the lathe , and it holds your dremel tool with a stone in it. Then bore out the stator's rotor hole until that rotor will just slide in it. Keep that air gap a tiny as possible, cause the tighter it is, the more torque/horsepower you make, for the same amount of amps used. I once bored out an AQ 2030 like that, and put a rotor out of a dyna 3835 1500 in it. That was the strongest AQ motor I ever built, but it was still no match for a stock 1500. I called it "Frank" short for Frankenstein!

I use a one ton arbor press from harbor freight. Use enough pressure until you get it little enough to fit inside the can. I just press them until I feel the resistance get pretty hard. That lets me know it's about as far as it will go.
But I don't think that it's necessary at all or has any bearing at all on the performance aspects of the motor. It's just to get them in the can. I really feel that they would cool better if left dangling in the air," IF" we had some air moving through the motors. Which we don't! Maybe being compressed helps carry the heat out through the stator ,case, cooling can, by making better contact with each wires surrounding wire. I have some insulating varnish which I have dipped a few wound stators in. It's supposed to lock all the wire in place so the don't wiggle and chafe the insulation, and transfer heat to the case better, because it is now one solid unit. I don't know for sure, but it does make them look good.

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Originally Posted by grsboats

A big thank you for sharing your knowledge with us....just used to do this years ago with my slotcars motors.Gill

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Yes Gill. I can just barely remember back in 1967, rewinding one of my slot cars armatures. I was 14 years old so I'm betting it was an ugly job. But I do remember that it ran ok.

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Originally Posted by Johnc

Gee Whiz Mr. Don, I should have just asked how much to rewind for me lol. Just kidding. Glad everything worked out for ya. Looks like I did get took on that motor.

John

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Yes you did John. Whoever sold it to you had to know something was wrong with it.

See, the problem with getting me to rewind it for you is that you would then have even MORE money in it, and you can get a brand new one for $90. But then, it would not be nearly as strong or durable as my rewind. BUT instead of paying $90 for a new Leopard, put a little more with it and get a comparable sized TP and have a really good motor.

Don, if i wanted to read a book to learn more is there something you would recommend?

Sorry Terry but NO, I have not found one, but I have not really looked for a single source for the info either. All the info I have and tell ya'll about, comes from the internet. I spend hour after hour of searching and reading useless crap, just to find a couple of paragraphs that actually mean something to us. But I try to not just repeat what I read, until I can prove the theory out to myself and understand it.

Some of the best info I have gotten comes from this thread on rcgroups. https://www.rcgroups.com/forums/show...s-checks-tests

A lot of it is from 15 years ago, but it's still the best I have found. These guys rewind outrunners, but most of the info still applies to our inrunners too. But just like has happened with every hobby that I have ever been involved with, most of "The EXPERTS" try to make it sound as complicated as possible, ans seem to be totally incapable of breaking it down into terms that the average guy can understand.

This video explains more about how our motors work and what makes them spin, than any other I have found. Forget the synchronous part as our stuff does not work like that, but it shows the stator poles and how they rotate to keep a "pulling coil" a little in front of the magnets on the rotor.
https://www.youtube.com/watch?v=LtJoJBUSe28

very impressive Don , looks confusing to me , I used to handle the old slot car motors but that don't have a clue !!!

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Originally Posted by donhuff

Then after pressing the snot out of it, I actually enjoy doing that.

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Question how do you solder the end of that insulated wire plz !!

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Originally Posted by dasboata

very impressive Don , looks confusing to me , I used to handle the old slot car motors but that don't have a clue !!!

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Thanks, most of the slot car motors were 3 pole. A magnet with the north facing in on one side, and a south pole facing in on the other. Then the armature had the three coils on it, and the commutator and brushes did the "commutation" (switching of current polarity heading to those coils) . In these old motors, the current polarity was always the same all the way to the brushes. And it is the commutator contacting the brushes with a + and - going to the coil, and then some degrees of armature rotation later, it gets a - and + charge from them, and thats what causes the magnetic polarity of the coils on the armature to reverse. Note two that all three coils are charged all the time, with two coils being north and the other south, then vice versa.
https://www.youtube.com/watch?v=1673-0Y3fFQ


The big difference with our brushless motors is the commutation is all handled by the ESC. Also our motors are all inrunners where the coils are in the stator and the permanant magnets are one the rotor.
And another big difference is that only two legs of our motors are charged at one time, and the third is sending a charge of back EMF to the ESC. This signal is what "tells" the ESC where the rotor is in it's rotation. Ya know how sometimes when you give a motor a tiny bit of throttle, it might act a little confused and shutter a little before going on and spinning up. That's cause ithe ESC hasn't figured out exactly where the rotor is yet. The rc car guys get around this (because they sometimes need to go really slow) by using a sensored motor. The back plate of the motor has tiny hall effect sensors on it that sense where the rotor is all the time and at any rpm.

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Originally Posted by dasboata

Question how do you solder the end of that insulated wire plz !!

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Your not gonna like the answer!!!


I use a 3" diameter iron rod with a well bored into one end, filled with 3 parts LYE and one part salt. Put a torch on it and heat until it is liquid and blazing ass hot. Dip the wires in it and wait till it stops boiling, then dip slowly into water to cool before the lye has time to harden. Wash off with soapy water and solder pretty soon or the copper will corode. BE CAREFUL!

Ray sez he uses an iron pipe cap and that should work fine too.

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Originally Posted by donhuff

Your not gonna like the answer!!!


I use a 3" diameter iron rod with a well bored into one end, filled with 3 parts LYE and one part salt. Put a torch on it and heat until it is liquid and blazing ass hot. Dip the wires in it and wait till it stops boiling, then dip slowly into water to cool before the lye has time to harden. Wash off with soapy water and solder pretty soon or the copper will corode. BE CAREFUL!

Ray sez he uses an iron pipe cap and that should work fine too.

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Love it ,I'm going to use it thank you !!

Don't forget the glasses and gloves.:flammes-09:

Larry