3573 replies to this topic

[havlicek]

If the arm isn't magnetically centered it will jump substantially when the motor is started. Slot drag racers have figured out that if you space the motor for this in the first place you pick up substantial top end and ET.

Hi Mike,

I thought that this was pretty common knowledge by now for all slot racers, not just drag racers? Unless you mean that drag racers were the first to figure this out??

If you want to send a drag arm that has been statically balanced we could do a test on ET and MPH before and after a dynamic balance.

I don't know why I would do that as I've already said that dynamic balancing is more accurate? I'd be happy to send an arm to someone anyway...for stuff in return

BTW, even a not true tail spacer or com end can contribute to vibration. I'm sure you know that from building motors...but I only recently came to understand that it can be significant.

John, actually before dynamic was commonly available, we usually did the longitudinal balencing as well.

Hi Rocky,

I've thought about that (as per my post above and why I start balancing nearest the com)...even imagined a setup to do that kind of balancing with ball bearings and all kinds of labor-intensive fabricating. Then I thought better and went back to what I was doing before It seems like too much work to me and I've never seen a manufactured balancer for this. Can you point me to a balancer capable of doing this? Pictures? Links? Inquiring minds want to know!

Have I ever steered you wrong?

Well heck...I don't know The slot history stuff you seem to have an encyclopedic knowledge of, between yourself Don Siegel and of course Phillipe(!) I learn stuff here everyday. The arm-winding stuff seems to agree 100% with what I've learned, so I think we're sympatico!

-john

[havlicek]

I rigged a new way to push out shafts that is working like a charm. I got a 4 inch C-clamp, removed the swivel pad and then drilled through the cast/fixed end with a 1/8" drill using a long bit and going from the threaded end. I sorta eye-balled it keeping the drill bit centered visually in the threaded hole and marked the point of contact between the now-exposed ball and the fixed surface. The hole went through pretty straight and came out the back of the clamp close to dead-center. I also ground a small recess in the ball end of the clamp screw to keep the arm shaft in place as I push it.



I've tried it on a dozen or so assorted blanks both with hardened shafts and the easily bendable non-hardened kind (no names mentioned) and it pushed them all easily and from either end to boot. It didn't distort the softer shafts either! So if you want to replace a shaft...or to make a can-drive arm blank into an endbell one (or vice versa), this is a very easy and cheap way to do it.

-john

[Alchemist]

That's ingenious John! If I may ask you please, would you be able to take segmented pix of the tool as it removes the shaft? Very cool tool!

Thank you John!

Ernie

[TonysScrews]

Question.... Can anyone confirm if I have these windings correct? What is the standard stack length of each of these motors?

16D - 70T30
S16D - 60T28
Outlaw S16D - 60T28 (same windings but shorter stack?)

S16C - 55T28
Super Wasp - 60T30
Contender - 55T30
Group 12 - 50T29

Competitor - ? (not sure if this is another name for Contender?)

Thanks and best regards,

[Slotgeezer]

All the modern gadgets... All the new-age do-hickies... All the latest & greatest tools, supplies, & designs...

& our man John finds exactly the right tool, right in the drawer...

It's no wonder this thread is by far the most-viewed on Slotblog! ...

Keep looking thru the seams, John... The truth is there.... show us...


Jeff Easterly

[Phil Irvin]

"Necessity-- The mother of invention" How true.........

OLPHRT
PHIL I.

[JoB]

Thanks John and Doug,

This was exhausting answers Good though.

I had a try on a test arm I'd wound. After removing not very much from 2 poles it spun much smoother than before. I couldn't feel so much vibration in my fingers holding the motor as before the balancing. So I rev it up and it was whistling away... and then SMACK.. the com blow

It was an old com though and it seems that the plastic was a bit brittle and the copperplates had kind of released a bit from the plastic substrate.
Anyway it's good practice and fun learning

Just need to get a few comms... a good source someone?

Jens

[havlicek]

That's ingenious John! If I may ask you please, would you be able to take segmented pix of the tool as it removes the shaft? Very cool tool!

Hi Ernie,

Sure thing. I'll get the pictures up a little later. This is a MUCH better way than I had been doing it, and even stubborn shafts move pretty easily now. I guess I've had the most difficulty with some of the powder coated Muras, but they're no problem now...and the older Muras shafts are generally excellent anyway. Also, some FT36D shafts have been all but impossible for me in the past, but I tried one yesterday and I was able to push that as well.

Hi Tony,

Those winds (at least the few I'm familiar with) seem about right. Guys like Barney, Rocky, Phillipe etc. know this stuff by heart and should be able to confirm. The only thing I would say is that I know some of the various Mabuchis (even among the same motor type) had different winds. So there wouldn't be one standard "FT16D wind".

Yo Jeff,

Slowly, it's become a necessity as I've dug deeper and deeper into this whole armature thing to have an efficient way to either push or remove arm shafts. It seems that some new motors have poor quality shafts that will make them run rougher (and possibly have poor gear mesh in extreme cases) as well as making balancing very difficult. Also since I'm using many recycled arms because of the difficulty and expense of buying new ones, sometimes I'll need to push a shaft to get an endbell drive blank out of a can drive one. There's also the occasional oddball like making a long shaft arm for 4WD by removing the stock shaft and installing a long enough one. This simple method makes all that relatively easy.

Hi Jens,

Yes...I guess we did get a little excessive with the whole balancing thing, and after Doug's post I figured it was a good time to dig a little deeper into the whole balance subject and how difficult and important it is. I think it's awesome that you're winding arms and even if you only get an arm a little better balanced than it was before...it's still an improvement worth making. I've had the same problem from time to time with old coms and you have the right attitude...when they blow up...just make another one! Look for coms on new (but no longer useful) 16D motors. The tabs can be carefully pried open with an X-acto knife and the coms are a good fit for many vintage Mabuchi motors. The magnets also work really well in those motors...MUCH stronger than the original ones. Other used motors also can be sourced for coms and other parts...OR...simply rewound and put back together again if they have removeable endbells. Get creative and look around, there's plenty of motors out there waiting for you to do your magic on!

Hi Phil,

No doubt there are even better ways to do all this with machine-shop type tools, but this has got to be pretty close. It works really well and I use it mounted sideways in a vise. When done, I can put it away because it's no bogger than a 4" C-clamp.

-john

[havlicek]

Per Ernie's request, here's some pix to better describe what I do here with these problematic (and formerly intransigent/uncooperative) shafts.

Here's the C-clamp with the swivel pad reinstalled. I saved the pad and sanded it flat on my work glass with some sandpaper stuck to the glass for when I need to use the pad to push stuff. To remove the pad, simply unscrew the clamp all the way and the force of the clamp screw will pop the pad right off.



With the pad removed, I reinstalled the screw and tightened the ball end of the clamp screw against the fixed/cast end of the clamp to mark the point of contact between them. This would be my target with the drill. Then I removed the clamp screw again so I could drill through the cast end of the clamp with a long 1/8" drill bit. Eyeballing the bit to keep it centered in the threaded hole used for the clamp screw produced a pretty accurate hole that ran completely through the clamp. A 1/8" hole will also allow for pushing FT36D shafts.


Here's the test subject...an arm of unknown lineage (probably a modern D can arm) and a long stack. Longer stack mean more difficulty pushing the shaft because of increased grip length of the stack plates against the shaft.


Here's the arm installed in the "pusher". As I had mentioned in the previous post, the ball end of the pusher has a recess ground in it to keep the arm shaft in place as I apply force.


With some force (not much really because of both the leverage the clamp affords as well as the solid base you're pushing against)...the shaft begins to move.


Here's the replacement drill blank shaft with one end slightly chamfered so it will find it's way easily into the center hole of the target stack.


Using the new shaft to push out the old shaft after you push it flush to the stack (I forgot to take that picture, so use your imagination ), you get the old stack with a nice STRAIGHT & HARD new drill blank shaft.


Once you've installed the new shaft, you have to be careful because the lams will often times fall apart with an uncoated stack. The good news is that once you push the shaft the first time, it's easier to do it a second time...here's the original arm with the old shaft reinstalled by using it to push out the drill blank with the C-clamp pusher. At a couple of bucks a throw for the drill blanks...I'll wait to actually keep a drill blank in this arm until it is used for a project. McMaster Carr has both 2mm drill blanks and 5/64ths, but 5/64ths is too undersized for slot car motor bearings and bushings. 2mm is perfect for most bushings but won't fit (without polishing them down) the bearings I've seen and used. Happily, McMaster Carr also has a slightly oversized .0781" drill blank that is a perfect fit for these bearings. For the larger shaft FT36D motors, a 1/8" drill blank is a good fit and those are easy to get as well. You can also use .078" piano wire for some motors and get good results instead of 2mm drill blanks...not as straight and not as hard, but very cheap and you can make up long shaft arms with this. I've tried long pieces of "drill rod" and it's a pretty good material as well and much cheaper than drill blanks, but drill blanks are the best for those "special jobs".


I hope this helps someone.

-john

[Prof. Fate]

Hi

John, see, the thing is that this hobby and winding by Mike and the rest were invented by kids for kids. You apply a lot more thinking to this than I think we ever did.

Just as you fabricated your static balencer out of razor blades...so did we! But in my case, I also did a simple fore/aft single blade balence to find the GG by approximation. A mark on the can indicating where I wanted to move the center was all I thought about.

We kinda made this stuff up as we went along, and mostly, being kids, we didn't make the press.

It is Fiddly, but as I have said before, bench time is golden time. So, if you think it fun to static balence fore and aft, do it..........."It's a hobby not a job".

The winds.
That is a "maybe". One is the problem of quality control, and the second is how recently I have played with a modern arm.

When I was required to race stock 16ds, there were two stacks available, the long stack, I don't remember the size right now, and a more standard 440 which was not allowed in some venues. Quality sucked. Winds were between 69 and 72 turns of 30 wire. This variability might be ON THE SAME STACK. from pole to pole. Super 16ds are a 28, with the above quibble.

Mura makes very consistant arms. I haven't had occasion to do a wasp or contendor in recent times. 10 years ago, they were 65/30, the wasp on the standard short stack, the contender on a medium 440(if memory serves).

The difference THEN between a Wasp and Super wasp was only that the latter was balenced.

Fate

[havlicek]

I also did a simple fore/aft single blade balence to find the GG by approximation

Oh I get what you mean now Rocky. I had envisioned something way more complex...probably beyond my ability to fabricate.

-john

[Alchemist]

M'ning John!

Thank you very much for posting the photos. Regarding Prof. Fate's comment about "kids" - looking at these photos brings back the excitement I had as a "kid" when I got my first slot car. I really appreciate this website and I wish to thank "Dokk" for having the brilliance to put it together - "Thanks Dokk!"

Ernie

[havlicek]

Hi Ernie,

Glad you enjoyed the pix. Regarding Rocky's post, I didn't do most of the stuff I'm doing now when I was a kid either. I still blow up arms, but less so. The arms that don't blow up run better than the ones I did then...and the motors come out a little nicer looking now than they did them. A big thing is using the best parts you can like the better shafts and that's something I never did back then. Unfortunately, good parts are much harder to come by now...but they can be found and by recycling and substituting, the old motors can live again.

-john

PS...I agree that Phillipe (and Greg and Bill) have done a wonderful thing with this site. People get to relive the excitement some 40-50 years afterwards, see how things are done and hopefully bring new people in.

[Champion 507]

John,

Just a friendly correction here...36-D arm shafts are .091 or .092, not 1/8 which is .125.

I certainly like your arm shaft press. I guess it's time to go buy a 4" c-clamp and a long drill bit.

[havlicek]

Right you are Doug. The 1/8 hole allows for the 36D arm shaft which I believe is also around 3/32" fractional or thereabouts and of course, those DBs are available from McMaster Carr and others.

-john

[Ron Hershman]

Question.... Can anyone confirm if I have these windings correct? What is the standard stack length of each of these motors?

1.16D - 70T30
2.S16D - 60T28
3.Outlaw S16D - 60T28 (same windings but shorter stack?)

4.S16C - 55T28
5.Super Wasp - 60T30
6.Contender - 55T30
7.Group 12 - 50T29

8.Competitor - ? (not sure if this is another name for Contender?)

Thanks and best regards,

USRA Minimum stack lengths...........................

1. .600"
2. .490"
3. Not a USRA spec arm...... they varied .350" to .440" depending on who made them at the time
4. .490"
5. .350"
6. .440"
7. .350"
8. .440"

[Champion 507]

I was hoping Ron would answer this one. I figured he would know. Thanks for the info Ron.

[Ron Hershman]

I don't know why I would do that as I've already said that dynamic balancing is more accurate?

There is no comparison between static and dynamic arm balancing.

I have rebalanced 1000's of static balanced arms in both brand new and used condition..... and have never found any to be accurate. In most cases I think there was more damage or out of balanced created by statically balancing them to begin with.

I have had many I could not make correction in a pole or poles as there was not much left to drill after someone filed or ground them while statically balancing them.

I once had a HO arm MFG send me arms for dynamic balance. I dynamically balanced them and returned them to him. He called me and asked me what was wrong with my machine...I told him nothing why????? He replied he had checked them statically and they were way out...... LOL

I told him to put one of the arms I balanced in a chassis and put a static balanced arm he had done in a chassis and rev both of them up on a power supply while he held each in his hand. I told him to call me back after he did this.

He called and told me he was sorry he wasted my time and that dynamic balanced arms were very smooth and his static balanced arms vibrated greatly and the he would never static balance arms again.

[havlicek]

There is no comparison between static and dynamic arm balancing.

...well, there IS a comparison because they're both having a whack at the same problem. Just that dynamic balancing is far more accurate which is why it's been the standard for so long. The other comparison is that with both, the accuracy is also somewhat dependant on the operator. Static balancing can make a noticeable improvement, but there are times (as with the HO example) where I can't really find fault with an arm on razor blades even though I know it's out-of-balance. Even with an arm that shows it's imbalance on razor blades, you can only go so far even with a smooth shaft on new blades and I often will just stop trying because I know I'm bound to do more harm after that point. No doubt that, if you have the time and budget, sending at least those "special" arms to Ron or someone else who does dynamic balancing will often result in a smoother running arm.

There could be times where there's no noticeable difference between static and dynamic balancing and that could be because of:

1)Pure luck (unlikely)
2)Other factors in the setup causing vibration that have nothing to do with the arm's balance.

-john

[Ron Hershman]

There could be times where there's no noticeable difference between static and dynamic balancing and that could be because of:

1)Pure luck (unlikely)
2)Other factors in the setup causing vibration that have nothing to do with the arm's balance.

-john

Being I have a machine that accurately checks and measures both Dynamic and Static balance.......

1. Pure luck....... I have yet to find a arm that was close or similar when checked both dynamically and statically. Yes I have found arms that were very close and not needing correction in either a static or dynamic condition but again never found one perfect in both conditions.

2. That would be a set-up problem and not a armature problem. If you have a arm that is balanced perfect and it shakes in a set-up...fix the problem in the set-up.

I don't know how many here know this, but I will share with you........ a magnet needs to be the same length of the armature stack plus 5% or longer. If you have a stack that is longer than the magnet length...you will have centering problems both statically when hand spinning the motor and when it runs. The arm will wonder around in the field unless it's spaced to center the arm in the magnets. By spacing the arm like this, it could lead to vibration problems between the arm spacer(s) and the face of the bushing or bearing.

Some motors will vibrate due to a bad magnet or magnet segment. This is kinda rare, but I have found many over the years.

[havlicek]

1. Pure luck....... I have yet to find a arm that was close or similar when checked both dynamically and statically. Yes I have found arms that were very close and not needing correction in either a static or dynamic condition but again never found one perfect in both conditions.

...that's what I said. In other words, the arm would show no noticeable improvement.

2. That would be a set-up problem and not a armature problem. If you have a arm that is balanced perfect and it shakes in a set-up...fix the problem in the set-up.

...that too is what I said. It still doesn't negate the fact that dynamic balancing will be more accurate, even when the difference is unnoticeable in a setup

-john

[Champion 507]

Ron,

Are there any other arm/magnet relation issues that we would benefit from knowing the solutions? I'm sure others would like to learn too. Thanks.

[Ron Hershman]

...that's what I said. In other words, the arm would show no noticeable improvement.




-john

Well that depends on how your checking it or correcting it....... example..... I have found arms that statically are perfect, but when checked for dynamic balance, they were way out of balance dynamically and would vibrate greatly when ran in a motor.

Sorry, but a arm statically balanced is not truly balanced. If static balancing was accurate and worked, we would not be dynamically balancing armatures. Dynamic balancing is the only way to balance armatures and any other way is a complete joke. It didn't work in the 60's and it still doesn't work today.

If you were to send me a arm that you statically balanced perfectly, I could check it dynamically and it would need correction everytime.

I know this because I have had perfectly statically balanced arms sent to me to be dynamically balanced and they showed great improvement after they were corrected.

[Ron Hershman]

Ron,

Are there any other arm/magnet relation issues that we would benefit from knowing the solutions? I'm sure others would like to learn too. Thanks.

You would have to be specific.

[havlicek]

Well that depends on how your checking it or correcting it....... example..... I have found arms that statically are perfect, but when checked for dynamic balance, they were way out of balance dynamically and would vibrate greatly when ran in a motor.

Nope Ron...I think we're slipping into those freeblog kind of posts where we're discussing how many angels can dance on the head of a pin. I said..."no noticeable improvement" even though they show an imbalance. That means exactly what it says with no qualifiers...ie, you can't notice an improvement. You can have an arm that shows no noticeable improvement in terms of how it runs when dynamically balanced over static balancing and it's not a particulaly rare thing.

On the magnet length thing, funny you should mention that as Barney and I were talking about that just testerday!

-john