106 replies to this topic

[Phil Smith]

Gotcha on the dwell, but timing would advance as well. Looking at the endbell end of a motor and looking at the brush on the left side: A 1" brush on a 1" comm would contact the next comm segment at 12 o'clock high. A 1" brush on a 5" comm, the brush would contact the next segment around 9:30PM. That is an extreme example, but it translates to smaller differences as well.

[Guy Spaulding]

The timing would "seem" to both advance and retard. The commutator segment may reach the brush sooner (advance), but it also leaves the brush later (retard). These actions somewhat cancel each other out.

[slotbaker]

[Cap Henry]

Can someone explain the inside and outside firing if I missed it? LOL.

[Ron Hershman]

'Dallas Racer', on 22 Nov 2011 - 7:49 PM, said:

Gotcha on the dwell, but timing would advance as well. Looking at the endbell end of a motor and looking at the brush on the left side: A 1" brush on a 1" comm would contact the next comm segment at 12 o'clock high. A 1" brush on a 5" comm, the brush would contact the next segment around 9:30PM. That is an extreme example, but it translates to smaller differences as well.

Nope again you are advancing the firing and dwell of the segment in your example. We set timing on arms based on the slot in the comm and between the comm segments.

A smaller comm gives a shorter segment height which will fire quicker.

Degrees of timing... the position of the slot/comm in relation to the arm stack/blank remains the same

For example... take any arm with a comm diameter of .200"... cut that comm to .180" (you can not cut a .200" dia comm to less than .175" as you will be into the fill that holds the plates on )... you are shortening the comm segment height .010"... how much advance or degrees of advance do you really think you are getting due to the comm segment being .010" shorter?

The smaller the comm.... the more dwell and duration ( firing )... this is why they don't use comms smaller than .175" on high end arms

If the Chinese 16D style sized comms were used on the upper class stuff... we would fry lots of arms... it has nothing to do with physical static position of the comm in this case and has everything to do with dwell, duration and firing. The only way to make a smaller comm work on high end stuff is to reduce the size of the brush.

Again... think horizontal versus vertical brushes.

[Ron Hershman]

'TeamCHR', on 22 Nov 2011 - 9:33 PM, said:

Can someone explain the inside and outside firing if I missed it? LOL.

Can't give away all the secrets... LOL... if any thinks they know... go for it.

[Bill from NH]

'flem1959', on 22 Nov 2011 - 7:03 PM, said:

Don`t you dare say anything bad about Parma here or you`ll get put in time-out!

[Pablo]

You will cook those motors if you advance the endbell too much...

[Victor Poulin]

'slotbaker', on 22 Nov 2011 - 9:22 PM, said:

Hahaha!!! I'm with you, Steve.

[Lucky Me]

'Ron Hershman', on 22 Nov 2011 - 9:48 PM, said:

Can't give away all the secrets... LOL... if any thinks they know... go for it.

OK, this is most likely way off base but read THIS.

[Mike Patterson]

I'll take a stab at the "inside-outside firing": Each pole or coil on the armature has two leads. Depending on how these leads are attached to the commutator, the current will flow from the outside winds to the inside, OR, the current will flow from the inside to the outside of the coil. Am I close?

Isn't thread drift a wonderful thing?

[Rick]

Hershman is correct, the timing of the com does not change. That is fixed to the stack. But the firing event happens sooner on the smaller comm and also the short lasts longer on the trailing end. Where does this all become diminishing returns?? I guess you will find that out as you cut your comm diameter.

One thing is certain, you can't polish a turd...

[James Grandi]

Leon,

Not to attempt to confuse you anymore than you may already be from the massive flow of information above ( you guys are thorough! ), but keep in mind that adjusting the timing will affect the characteristics of the motor...

If what I've been told over the years of learning about motors is correct, advanced timing will give you more top end, while retarding it will generally give you more off the bottom end, and a bit better braking. You'll find different timing settings will prefer different gear ratios in order to obtain the best balance of performance, so be ready to spend some time testing different configurations and settings to find what works best for you

[Leon]

Thanks for all the answers.

[Phil Smith]

'Rick', on 23 Nov 2011 - 04:43 AM, said:

Hershman is correct, the timing of the comm does not change. That is fixed to the stack. But the firing event happens sooner on the smaller comm and also the short lasts longer on the trailing end.

Ok, maybe Ron and I are talking about two different things. No, reducing the diameter of the comm doesn't change the timing on the armature, but it does cause the brush to contact the comm segment sooner (firing event), thus advancing the timing.

So cutting the comm doesn't advance the timing on the arm, but it does advance the timing of the motor (everything else being equal).

[Zippity]

Ask Gill A (here in NZ) about having a motor rezapped or rebuilt and having the magnets placed back in the wrong order

[Ron Hershman]

'Dallas Racer', on 23 Nov 2011 - 6:38 PM, said:

Ok, maybe Ron and I are talking about two different things. No, reducing the diameter of the comm doesn't change the timing on the armature, but it does cause the brush to contact the comm segment sooner (firing event), thus advancing the timing.

So cutting the comm doesn't advance the timing on the arm, but it does advance the timing of the motor (everything else being equal).

The only thing it "advances" is the time the brush fires the comm which charges the coil. Has nothing to do with the physical timing/position of the comm. It's advancing the "fire" time or increasing the firing time......it makes it happen a tad sooner.

When I said .010" difference in comm segment height ( when you cut a comm from .200 to .180 ) it's actually .005"

'Zippity', on 23 Nov 2011 - 7:31 PM, said:

Ask Gill A (here in NZ) about having a motor rezapped or rebuilt and having the magnets placed back in the wrong order

Just go ahead and tell us what happened.... LOL

[Zippity]

My lips are sealed. Life is too short!!

[Phil Smith]

'Ron Hershman', on 23 Nov 2011 - 7:55 PM, said:

The only thing it "advances" is the time the brush fires the comm which charges the coil. Has nothing to do with the physical timing/position of the comm. It's advancing the "fire" time or increasing the firing time......it makes it happen a tad sooner.

When I said .010" difference in comm segment height ( when you cut a comm from .200 to .180 ) it's actually .005"

Because the brush wraps around the curve of the comm surface, the brush's leading edge will advance more than .005 around the perimeter of the comm.

But at least you finally realize that cutting the comm advances the timing. Thank you.

[Pablo]

As far as motor rotation direction/polarity, cheater taught me to place the south mag to the rear of the motor, and the forwardmost of the two hood prongies will be positive.

The trick is, the concave side of the magnet is how it is named a "north" or "south" magnet. Since it's impossible to hold a compass up to the inside of the motor, place it against the rear of the can. The compass will orientate itself north for a south magnet and south for a north magnet. You want the compass to point north.

Now, as far as southern hemisphere, will it work the same way, or the opposite ?

[Zippity]

same - 'cept we wire our tracks opposite to you lot

our tracks are normally powered positive to the left braid in the direction of travel - we place the south magnet against the axle.

[MSwiss]

'Dallas Racer', on 23 Nov 2011 - 8:50 PM, said:

Because the brush wraps around the curve of the comm surface, the brush's leading edge will advance more than .005 around the perimeter of the comm.

But at least you finally realize that cutting the comm advances the timing. Thank you.

Sorry Phil, highlighting and supersizing one word in Ron's post doesn't make you correct when you are wrong.
Increasing commutation/commutator firing duration has nothing to do with increasing the timing of the motor.

To quote my ex-boss, Stu Koford (AKA, most knowledgeable person in slot cars with electric motors)
"They are two entirely different things".

[havlicek]

It's pretty simple when you get right down to it. Think of an armature as being made of two 360 degree devices linked to each other...one being the coils and the other being the commutator. If you're looking at the arm from the com end, you realize that no matter what the size of the com and the stack, they are related to each other in "steps" of 120 degrees ( 1/3 of a full circle). The position of the com segments to their corresponding coils (timing) is not related to the size of either, since if you expand the 120 degree lines outward of both the center (or either edge) of the com segments and the armature stack...or even if you only expand one which would be analogous to changing their size or the size of one and not the other, their relationship doesn't change. If they were at zero degrees advance (neutral timing) in the first place and you only change the size of either or both, they are still at zero advance.

-john

[Phil Smith]

I don't know how to use any drawing software, so I had to learn the basics of Google Sketch to create an illustration to help make my point. (It's pretty sad that I would go to so much trouble to try and win an argument about toy cars. LOL)

I've already said this but let me say it again: REDUCING THE COMM DIAMETER DOES NOT CHANGE THE TIMING OF THE ARMATURE! I know that. That's not my argument.

Reducing the diameter of the comm does however change the timing of the MOTOR. By motor I mean a fully assembled, ready to run motor. By timing I mean the position of the armature stack when it becomes charged with electricity and becomes magnetic.

The illustration is an inside view of the endbell end of a motor. The rectangle is the left side motor brush. The inner most circle is the armature shaft. The outer circle is the uncut comm. The slightly smaller circle represents the cut comm, the reduced in size comm. The angled lines show at what degree the brush comes into contact with the comm face. The slots on the comm are not represented. Where they're located doesn't really matter for this argument.

The brush size stays the same. The comm size is the variable. As the comm diameter is reduced, the brush's leading (and trailing) edge moves farther around the circumference of the comm. This causes the armature stack to become charged (fire) sooner. And THAT is advancing the timing.

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[Phil Irvin]

'Dallas Racer', on 24 Nov 2011 - 5:56 PM, said:

I don't know how to use any drawing software, so I had to learn the basics of Google Sketch to create an illustration to help make my point. (It's pretty sad that I would go to so much trouble to try and win an argument about toy cars. LOL)

I've already said this but let me say it again: REDUCING THE COMM DIAMETER DOES NOT CHANGE THE TIMING OF THE ARMATURE! I know that. That's not my argument.

Reducing the diameter of the comm does however change the timing of the MOTOR. By motor I mean a fully assembled, ready to run motor. By timing I mean the position of the armature stack when it becomes charged with electricity and becomes magnetic.

The illustration is an inside view of the endbell end of a motor. The rectangle is the left side motor brush. The inner most circle is the armature shaft. The outer circle is the uncut comm. The slightly smaller circle represents the cut comm, the reduced in size comm. The angled lines show at what degree the brush comes into contact with the comm face. The slots on the comm are not represented. Where they're located doesn't really matter for this argument.

The brush size stays the same. The comm size is the variable. As the comm diameter is reduced, the brush's leading (and trailing) edge moves farther around the circumference of the comm. This causes the armature stack to become charged (fire) sooner. And THAT is advancing the timing.

The best explination and illustration of what has been tried to be explained on this topic. We have all seen this on the PARMA brushes from a 501 & 502 endbell. They are so sloppy. The brushes will cock twords the right RETARDING THE FIRIENG TIME in relation to the magents but NOT by the comm to the laminations...

OLPHRT
PHIL I.