339 replies to this topic

[Dave Reed]

For your review:
Here is the highjack ... foo
 
 
Now go and read where the put-down started.

I know Dan KNOWS what he is talking about, you not so much.. If you feel PUT Down, Don't worry as I am sure it's all in your mind..Dan has been dealing with the peanut gallery for many years and I am sure he didn't mean to PUT YOU OR ANYONE ELSE DOWN.. As I had wrote earlier you have managed to High Jack this Thread to be about you.. Try THIS.. Don't wear your feelings on your sleeve and they won't get knocked off..

[Gator Bob]

Still going, Dave?

 

Bring your sleeve over to freeblog.

Let this thread be about armatures.

[Cheater]

This thread is really all over the board in the last page or so.

Here at Slotblog, it is required that you allow others to hold opposite opinions, even if you think they are completely wrong. And it's OK to tell others that you think they are wrong, but do not feel you have the right to disparage or insult them because of those opposing positions.

It's all about the free exchange of information and also respect for others. If you can't do that, please refrain from posting.

[NSwanberg]

Now, I have a question about voltage threshold when rewinding an armature.

 

When I'm searching the internet, i come across motors with such a diversity of operating voltage.  I'll see a motor that has a Recommended Operating Voltage (ROV) of 3 volts, while another is 9V or 12V, some have a range of 3V to 6V etc.,

 

What specifically determines the maximum voltage that a motor can run efficiently and last longer than single race?  Is it the wire gauge and number of windings, magnet strength, commutator material?

 

I ask because I've been experimenting with a few surplus motors I purchased years ago.  The ROV for this is motor is 7 volts.   I've been using them on our Blue King which operates at 13.5 volts.  I'm just playing around with these motors and at 13.5 volts they're mighty fast and as I deduced, and obviously they do get hot!  I run about 20-30 laps at a time but I figured they would have blown up by now.

 

I've got a 3V motor that I want to experiment with and see what happens.

 

This video is what peaked my interest is trying lower ROV motors:

 

 

Thank you.

 

Ernie

 

This guy is lucky he did not blow his thumb off.

 

In our little permanent magnet 3 pole DC motors when you plot voltage applied against the current drawn you will see a voltage where the current draw flattens out and remains nearly flat even as you increase the applied voltage. This is the voltage at which the motor will run the most efficiently for its intended purpose and will probably have the longevity the manufacturer intends. I believe this is the voltage at which the motor is designed to run. Run it at higher voltage and you get one of those diminishing return functions and the additional watts you put in mostly come out as heat and not power. Just my 2sense worth.

[havlicek]

Ernie,

 

     Again, there is no "standard" for rating these motors operating voltage.  All we have is the ability to make a vague/general guess as to how long one might last in real world conditions (voltage, gearing, car weight etc.).  Calling a motor a "3V" motor, or even saying a motor has a 3V ROV is all but meaningless.  One person could say a motor has a 3V ROV because he only expects the motor to last for a minute under whatever conditions he plans to subject the motor.  The old drag racers would run nominal 6V or so motors at 24V, but they would only expect the motor to hold up to extremely short runs.  For their purposes...those were "24V motors".  If someone unfamiliar with modern open motors were to determine the ROV for one of those using a power supply, they might guess that they're 3V motors

 

-john

[JimF]

FWIW and YMMV...................

 

In the late 60's I wound dozens of arms in the D/29, D/28, S/25, S/24 range. When I sent a batch to John Thorp for truing and balancing, he would invariably comment that the doubles were way easier to balance than the singles. On track, it seemed that the singles were slightly faster (maybe) but the doubles were smoother and easier to drive. Some of the Thorp team guys rather quietly preferred the doubles over the singles, at least at that time.

 

Apropos of nothing except that there is no one answer to any of this....... Once, right before quitting slot cars to go ski racing, I wound a single (pigtail) 22. The darned thing was soooo fast that folks said it sounded like it was gonna break down the bank @ Speed and Sports' new king track. Problem was of course that that it was undriveable. A D/25 might have been a better call.

 

Then again.........................

[havlicek]

Hi Jim,

 

     There's no doubt that doubles run "differently" from their "single-equivalent", and there's no doubt (at least in my mind) that the way they run could be an advantage.  The thing is, in an age where you can't run anything (except in open "anything goes" classes) that isn't tagged and "spec", is it worth it for arm makers to go through the extra bother?  ...probably not.  I can do a fairly neat double 28 or double 29 (parrallel wound...not layered), and some might prefer the way it would perform, but whether or not that translates into more podium time is doubtful.  It seems that what DOES "work" is getting all the PITA little details that Dan Miller has spoken of right, and THAT is really hard!

 

-john

[Paul Kovich]

Dan, any chance you will ever do G7 arms again ? I know you are busy with Eurosports, but I am down to my last few PK's and they are still competitive with any .480 arm being made. It would be great to see a new .490 PK produced. Stu could use some competition. BTW I recently got a copy of the "On Track", March/April 1987 which has the article by Paul Kassens interviewing you, Stu, Joel and Ray Birmele about motors. Still a great read!!

 

ps. All four of you said the same thing about singles versus doubles back in 1987. LOL.

[NSwanberg]

"In the late 60's I wound dozens of arms in the D/29, D/28, S/25, S/24 range. When I sent a batch to John Thorp for truing and balancing, he would invariably comment that the doubles were way easier to balance than the singles."

 

This is the first time I have ever heard of this phenomenon and i would have thought it just the opposite. I wish the balance gurus would commment but it seems there so few double winds being done these days that little hard data could be gathered.

 

John H. - In your experience, with all the static balance you have done, do you find double winds easier to balance?

[JimF]

Can't speak to the experiences of others, but in my case, I was simply better at winding the smaller, more flexible wires and thus got more even winds with less imbalance to correct. I was also told that my doubles metered more evenly than my singles although I never had the instrumentation to confirm this.This would be particularly true when getting right up into the crown and the last wind wouldn't lay quite flat. I hated to use the "popsicle stick trick" for fear of nicking a wire and I found that much less necessary with doubles. These days, the commercial winding machines are soooo good that any advantage in winding the smaller wires would probably be lost.

[havlicek]

 

"In the late 60's I wound dozens of arms in the D/29, D/28, S/25, S/24 range. When I sent a batch to John Thorp for truing and balancing, he would invariably comment that the doubles were way easier to balance than the singles."

 

This is the first time I have ever heard of this phenomenon and i would have thought it just the opposite. I wish the balance gurus would commment but it seems there so few double winds being done these days that little hard data could be gathered.

 

John H. - In your experience, with all the static balance you have done, do you find double winds easier to balance?

 

Hi Nelson,

 

     In a word...no.  Here's the thing, if you're doing a good job winding and keeping your patterns tight and consistent from pole to pole, there should be very little difference in the amount of copper.  We're talking VERY little difference...like maybe 1/16th of an inch to 1/8th.  I've never checked by ruining a good arm I just wound, but if an arm meters exactly the same (or even close...within a few thousandths) to the thousandth of an ohm, it's going to be something like that.  Relative to the mass of the arm blank itself, that difference in copper is inconsequential.  If your coils are that different that you notice one particular type wind is easier to balance, you've done a really poor job winding...even more so if it's noticeable during static balancing which is less accurate than dynamic balancing.

 

I can't speak to what Mr. Thorp was saying, but there are other factors that are much more significant as far as affecting an arm's balance.  First off, the laminations themselves need to be precisely concentric around the shaft hole, since (from what I gather) the lams are dropped and pressed onto a shaft in the same orientation as they layed on the rod...which is the same orientation as they came off the punching machine.  If one side is slightly off, you then multiply that "error" times the number of lams and, since we're dealing with steel which is heavy, you could have a significant imbalance without even winding.  If you could "randomize" the lams orientation at some point in the process before pressing them, you could take away all or most of this issue, but that would make things quite a bit more difficult than they already are.  Second, you need VERY straight shaft material and not all drill blank is that straight.  Arm manufacturers do quite a bit of hassling to get "good" shaft material, especially when you get up into the open class stuff.  Then you "COULD" have balance issues as a result of poor coating and epoxying, but those are less likely to be significant just because epoxy has far less mass than either steel or copper (which is why trying to cheat and balance arms using epoxy that doesn't show doesn't usually work so well).  Of course, on the bleeding edge where the G7 and other super duper motors run, even getting concentric commutators and then truing them before balancing is the practice because those guys deal with butterfly farts and pixie dust to gain any possible edge.  Lastly, even if you have excellent shaft material and perfect lams, you can easily distort the shaft while pressing the stack.  Contrary to popular belief, even hardened drill blank can bend and stay bent before breaking.  Some lams have a very tight hole and the longer the stack, the more difficult it is to press them onto a shaft.  The press is exerting an extreme amount of force over a very small area, so the shaft needs to be very perpendicular to the lams shaft hole to avoid damaging the shaft.

 

So I have not seen any difference in balance between doubles and singles.  If anything, there's more potential to be off with doubles because they're harder to keep neat AND because more turns of skinnier wire produces a stack that will absorb more epoxy.

 

-john

[NSwanberg]

"So I have not seen any difference in balance between doubles and singles.  If anything, there's more potential to be off with doubles because they're harder to keep neat AND because more turns of skinnier wire produces a stack that will absorb more epoxy."

 

This is what I was thinking that the doubles would offer more chances for the epoxy to sluff and run and get all out of place but I sure as heck would never second guess Mr. Thorp.

[havlicek]

I wouldn't second guess him either Nelson.  Still, I'm at the stage now where I'm "fairly confident" about a lot of this stuff.  When people ask me to do a double for them, I'm happy to oblige if it's do-able.  I'm just not sure that, in most cases, any advantage is worth the effort.  There are ways to get some of the advantages of a double wind without doing a double wind...the type of lam, the setup etc. can all be messed with...and then there's 5 poles

 

-john

[JimF]

Hmmm I thought it was clear that Mr. Thorp's comment was directed at my doubles and that they were easier to balance than my singles. That's simply a reflection on the fact that at the time, I never did more than maybe a dozen arms a month and was better at winding doubles than singles. The results on the balancing machine and bridge readings showed that. Because I was better at doubles......I did them more and hence.......was even better yet.....etc.

[havlicek]

Yes I see that Jim (unless you were aiming your post at Nelson...hard to tell???).   However, I  was answering Nelson's question about doublewinds in general, and also quoted him so it was clear what I was responding to.  In any case, your experience seems unusual from what I've seen.

 

-john

[Marty N]

John wound me a 45/28 that I installed in a Hawk set up with Emovendo magnets shimmed to a .550 hole. Arm is .513. Loaded this in a 112 gram hard shell 85 SVO Mustang drag car for our Street Outlaw's gig and keeping up with MUCH bigger motors. 1/8 mile passes .540 @ 50 MPH. Just thought I give some feed back on one of his rewinds. Low timed and cool as can be. I've had a ton of fun with this motor and surprised allot of other racers with it's punch. Thanks John.

[SlotStox#53]

Wow Marty sounds like you've got one killer motor and car on your hands ! Do you use the standard endbell on that hot hawk?

[havlicek]

Thanks for the good news Marty.  

 

-john

[Marty N]

Wow Marty sounds like you've got one killer motor and car on your hands ! Do you use the standard endbell on that hot hawk?

On this one, yes, the black bell with a no flange bearing. I'll be hitting John up for another arm shortly a bit hotter  Think I've wrung all this one has to give and the com is getting a bit smallish.

[SlotStox#53]

Cool, Bob who's got a hot drag hawk arm coming from John was debating on using the aluminum hawk endbell, that's why I was wondering what you were using Marty .


I'm sure John will have no issues with something Hotter !! how often do you cut the comm?

[havlicek]

See, but here's another important thing that really needs underscoring.  I can wind arms all day long, and probably make them competitive with what's out there, but the person doing the setup has to know what they're doing.  If you look at the specs Marty posted, those Emovendos are some seriously strong magnets...but if you look further, that's a large hole by ceramic magnet standards.  A short stack 45/28 in a tight setup with those magnets might well just sit there and go POOF!...and there's more still to the setup than "just" the can and magnets.

 

-john

[Marty N]

John has is nailed. I spend serious time and expense sorting magnet and gap out on the various arms John has made for me. Must have about a dozen "self" setups to get me ball park close then track time and the dyno sort out the detail.

 

Paul, comm cutting depends much on the wind and effiniecy I can pull from a motor and the efficiency of the car to use the power.

 

Some motors go dozens of passes between cuts. Some of the hot winds are done in maybe six pulls +/- 2 or so. John did a brace of 50/28 long D arms for me some time back that are so efficient, like nearing 50% that one has never been cut. Must have 50 pulls on it.  I have some open arms from both Proslot and Koford that I use in Neo/FC cars that are cut every outing just to keep peak performance. Those are 6 +/- types. Those motors are maybe 30% efficient? I had a double 28 done once that lasted one pull. (Not enough turns, stack to short and gap too thight) Than arm was 22%. Bottom line, if it isn't making power from the juice it pulls it's eating itself. As a rough guide, when the burn mark in the com gets about a mm wide, cut it and cut it as shallow as possible.

[SlotStox#53]

Thanks for the detailed explanation of motor efficiency and comm cutting to keep at peak performance, goes really well with all Johns rewinding information.

Amazing that some arms in some setups like you mention can kill themselves like that! Really brings home the wind /stack length/ air gap/ magnet variables and the importance of getting it right.

Thanks!

Paul

[Marty N]

Guess for the sake of clarity I should beat a dead horse just a bit Paul. No matter how efficient the wind is, the bigger the power (hotter the wind) and heavier the car, the shorter the comm life. I know that is preaching to the choir but some new people read these things too.

[havlicek]

I'm sending out a whole bunch of custom-wound Hawk arms tomorrow, but while I was at it, I did a couple of "what-if" arms for myself.  I know I've said it a bunch of times since they came out, but these little guys have a bunch of potential.  That's not news for those who already are stuffing all kinds of arms in these things, but it's instructive to see what's possible...I think.  So this is a plain-jane Hawk with the standard ceramic magnets.  The only things I've done here was to open up the endbell hardware to clear the larger diameter Bugenis com and to shorten the brushes a bit more than they already are so the back end isn't hitting the long leg of the springs (again because of the wider com).  No bearings, no shunts or spring insulation and stock springs.  In this case, I did a short stack (.350" long) arm, .513" diameter and a #26 wind.  The motor as is (it's even a sloppy setup with too much endplay) runs like the dickens...the thing really whistles:

 

Draws around 2 amps at 6V and doesn't seem to get at all unreasonably warm.  No doubt that with all the goodies installed, it could survive several minute heats.  Only the big guy knows what would happen in the Hawk 6 neo setup, but it snaps to life awfully quick as-is on the power supply.  Very cool little motors!

 

-john