28 replies to this topic

[Alchemist]

I just came across this video for the first time and just wanted to share it.  Hopefully my posting it isn't redundant!

 

[Hworth08]

The balancer does a fine job for home use as long as a person grinds a point on either end of the shaft with the heavier comm end being best. Easy to do with a hand drill and Dremel.

 

The machine does not allow dynamic balancing though.

[SlotStox#53]

Cool video. Pretty sure that's a video that is linked to an eBay auction/seller that sells these very balancing tools. Sells one at a time, have often thought about snagging one of them.

[Phil Irvin]

Years ago we used to use razor blades. I got pretty good with them. I got into R/C planes and with the big electric props. Balancing was a necessity.

 

I bought a magnetic one and it had the center rods sharp on both ends. I tried a slot motor and found that one end needed to be pointed. If not, they would not balance out. It does OK but will not be as good as the spin balancing of a pro setup.

 

OLPHRT

PHIL I.

[Dan Miller]

The idea that the average racer can grind a point, on the ends of the armature shafts, that is accurate enough, is just not reasonable to expect.

 

The tool is a slick way to get your money but little else. It strikes me as a joke.

 

For hobby fooling around, razor blades are OK until you dent the edge. Ground hardened parallel shafts are much better, as are a pair of thin ground pieces of hardened tool steel. Both methods pale in the shadow of the real way to balance, which is by using a proper dual plane electronic machine.

 

NOTHING else comes close.

[Hworth08]

Dan,
 
Chuck the arm in a hand drill turning the opposite direction of a Dremel with a cutting disc. Hold the Dremel at a slight angle and in fifteen seconds you'll have a very nice, centered point.
 
You're plain wrong and the balancer does a very nice job of static balancing. Friction is near zero and the tool doesn't have to be level.

[havlicek]

Getting a well-centered point on a shaft is heavily dependent on how true the shaft is, as well as how accurate the chuck on the drill is... and many chucks have a fair amount of run-out. I agree with Dan pretty much in that neither static method will be close to as accurate as dynamic balancing, even though you can do good work static-balancing (depending again on the things I've mentioned).  

How "good" is "good"... depends on how critical the application is. That faster an arm spins, the more critical any imbalance. Also, there are "places" within the RPM range of any arm (and motor it's installed in) where certain harmonics become more of a problem, so it's possible for even relatively slower-turning arms to have some more noticable vibrations.
 
The magnetic method has an advantage in that the jig doesn't need to be so accurately level to function well, but it's a big disadvantage to have to sharpen both ends of an arm shaft to an accurate point... both in time/effort (the shaft needs to be re-ground flat on the ends afterwards in most cases), and in some cases the amount of shaft that will have to be lost.
 
-john

[SlotStox#53]

For home track, hobby, and normal applications the static way is more than acceptable. Have noticed marked improvements in smoothness when running a motor on power, plus smoother torque on track.

[Champion 507]

Gimmie a bench grinder, I'll show you how to balance one

[SlotStox#53]

Now that's the way to do it!!

[havlicek]

For home track, hobby, and normal applications the static way is more than acceptable. Have noticed marked improvements in smoothness when running a motor on power, plus smoother torque on track.

 
True, Paul. Most of my arms are done this way and they're fine, but that's only because I don't have the ability to do dynamic balancing here. If I had the choice, I would use dynamic balancing every time. It is also a matter of consistency. I can sometimes get arms really close to what seems like "perfect balance", but not that often. If a person balanced 100 arms both ways, he would see a huge average improvement with dynamic balancing.
 
Of course, with either method, there's always the choice of the operator as to "how far to go"... so that is an equal variable that doesn't change according to what method is used.
 
-john

[SlotStox#53]

Too true, John. It's just cool being able to balance your own arms and bolt 'em up in a can and see improvements that you know you've done yourself.

[havlicek]

Oh, I agree 100%, Paul... and you're talking to someone who routinely prefers to do it himself, that's how I got into winding arms in the first place... both as a kid and again as an adult.  

BTW, I also tend to take whatever anyone says about all this with a huge grain of salt. On the other hand, Dan Miller has done it all... and I mean ALL to the point of producing world-class arms. He's really been through all of this stuff frontwards and backwards... inside and out, and is one of the few that I really listen to when he speaks.
 
-john

[Hworth08]

I guess you have to own the balancer to understand how well it works. You just put a point on ONE end of the shaft, that's all that's needed! Set the shaft up to the fixed magnet and then screw the other magnet up to about a 16th away, DO NOT have the shaft touching on both ends. The armature only touches on the point, the other hangs in the air.

 

A heavy 36D arm will spin around for a minute or so. The person in the clip barely spun the arm to show how the heavy pole goes to the bottom.

 

And there's no need to re-face the point, it hurts nothing. I usually grind such a point on the pinion end of the shaft to help center the pinion while soldering it on. Easy to grind a point on an assembled motor (sealed). Just spin the motor with a power supply at about three volts while gringing the point with a Dremel. That's the best way to cut a shaft off too.

[Gator Bob]

"Dad... I need two more of those razor blades".

 

Can you imagine selling a nine-year-old kid one of those today? "Jail time".

 

John, do you think that doing a static first then dynamic would make for a better balance?

[Pablo]

I have one of those that does wheels and gears also.

 

I learned how to balance pink Parmas very nicely.

 

Wheels, on the other hand, I could not find any modern wheels out of balance at all.

[havlicek]

John, do you think that doing a static first then dynamic would make for a better balance?

 
I can't really see how it would make for a better balance in the sense of more accurate, Bob. I sometimes will mark the heavy side before winding as there are some things you can do while winding to lessen that. It might make for a little less drilling later on. 
 
-john

[Phil Irvin]

John,

 

I think I asked before but do you wind by turns or by length of wire around a pole?

 

Back in the ol'days. I tried by turns but found that some will overlap the other pole causing more wire for the same number of turns causing all sorts of problems. Most with balancing and then with heat generated... I found that using the length I was able to produce more consistent running and better balanced arms before doing the razor blade balance.

 

OLPHRT

PHIL I.

[havlicek]

ALWAYS by turns (and pattern), Phil. I haven't found a reasonable wind yet where overlap is a problem. The only arms I've had a little difficulty with in that regard are some of the smaller five-poles.

 

-john

[Dan Miller]

Hworth08...

 

I am plain wrong???

 

There is no chance that an accurate point can be ground on an armature shaft using your hand drill and Dremel method. Then again, how could you possibly know? I doubt that you are capable of measuring it. Before you criticize anyone, you should insure that you are more qualified than the person you are taking to task. In this case, you certainly are not.

 

Dan Miller

[havlicek]

Dan,

 

I have one of the magnetic ones here somewhere and even built one before that and wasn't able to get consistent results. I still use a block of machined aluminum with razor blades... but I DID try. Since that point is the only physical "connection" to the balancer, I assumed not getting that precisely ground must have been the problem.

 

-john

[Dan Miller]

John,

 

Without the proper setup, grinding an accurate sharp point on an armature shaft, should not be expected. Plus the disadvantage of single plane balancing, offered by the static method, makes the process even less desirable.

 

The average guy would also not take into account that the shaft need be straight. Real straight. To well under .0005" for low class armatures and better for a serious race arm. Armature shaft flexing, which takes place at high RPM, because of bent shafts, just hurts performance. As a footnote, triangular ground shafts can happen, when poor quality control takes place, during centerless grinding of hardened steel shafts. This effects results, when dynamic balancing an armature, in a negative way. But that is another story.

 

Static balancing, for hobby fooling around, is OK by me. Just do not think that the magnetic thingies are any good, if you are handhack grinding points on your armature shafts. Blades are alright, as long as they stay sharp and do not become dented. Round, hardened shafts (think drill blanks) are one step better. Keeping your static balancing jig level is something to strive for.

 

None of the above come close to dynamic, dual plane balancing.

 

If any hobby winders are going to put themselves to a lot of trouble handwinding armatures, finish the process off properly. Send the arms out to be balanced the right way. Don't cheat yourself or take anything away from your own efforts.

 

Dan Miller

[havlicek]

As a footnote, triangular ground shafts can happen, when poor quality control takes place, during centerless grinding of hardened steel shafts.

 
I long ago found (the hard way) that besides being very straight and true, shafts need to be round, Dan. Before, I just assumed they were round because... well... they're supposed to be round. I found this out after not being able to figure out what was going on with a bunch of shafts that were giving me problems that I couldn't understand.

 

Of course, a shaft that is significantly out-of-round will behave very much like a shaft that's not straight and either will make an arm that's sitting on a bearing surface (either gauge pins or razor blades) act as though it's unbalanced. Getting really good shafts is (apparently) something of a crapshoot, but also REALLY important. I have some pretty good ones now
 
-john

[Bill from NH]

Send the arms out to be balanced the right way. Don't cheat yourself or take anything away from your own efforts.

 
Dan,

Who do you have balance the PK arms? I'm not an arm winder, at least not yet, but over the years I've used Thorp, Camen, and now Alpha for my balance and recon work.

[Pablo]

If any hobby winders are going to put themselves to a lot of trouble handwinding armatures, finish the process off properly. Send the arms out to be balanced the right way. Don't cheat yourself or take anything away from your own efforts.

 

That's good advice. The only ones I balance myself are the ones I'm just playing with. It's fun to do, but when it's time to get serious, I go to the pros.