Cutting a motor commutator & motor tweaks

[Charlie-III]

I now have a nice condition Hudy comm lathe......it's been a looooooooong time since I had one.

I found a Hudy manual here.... http://www.hudy.net/xhudy/products/p...0&kategoria=61 for anyone interested.

I need to check the set-up before cutting a couple of smoked comms......

[Charlie-III]

OK, question for the motor manufacturers....(Eddie0 & JRH).....arms....do they have to be laminations or "could" you do a billet core??

I'm guessing it could go either way but laminations can be "cheaper" to make since you just need a die to punch them out then stack them on a shaft. Doing a billet core would be CNC and likely cost more.

[EeePee]

Maybe those laminations are used for a reason?


That's a rhetorical question.

[Robbob]

ROAR rules ...... so many lamination's totaling a set length/size. Back in the days (way back) you had different motors with different stack sizes and you had guys that would remove lamination's.

But thats what I remember from back in the brushed days of looking for ways to make speed.

[TEDROCKZ]

A solid armature spinning would cause Eddy currents which cause heat and some parasitic loss. Laminations deter Eddys. Pretty much a non technical answer but there is a lot to type to get a full definition.


a quote from the web:
Eddy currents occur when a solid metallic mass is rotated in a magnetic field, because the outer portion of the metal cuts more lines of force than the inner portion, hence the induced electromotive force not being uniform, tends to set up currents between the points of greatest and least potential. Eddy currents consume a considerable amount of energy and often cause a harmful rise in temperature

[EddieO]

Laminations are there to counteract the hysterisis(spelling) losses induced by the eddy currents.

I've actually looked into a solid armature before for crawling. Simply too pricey to get made and getting it on the shaft wouldn't be fun without setting up a special press. I had some other ideas, but not something I could cut on my mill, so I said bleh....would need to be EDM cut. EDM machining low quanties is NOT cheap.

My thought was, maybe we could use the eddy currents to our advantage...

Sagami actually makes a smaller 280 or so size armature that's solid.\

ROAR rules allowed you to make an arm solid if ya wanted, but at the RPMs we had in racing, it would of been terrible....rules only really dictated length and diameter.

We used to make short and long stack arms in racing. Short stack was used in the 10t mod limit days....basically a work around the rules.....we messed with long stack stuff in different enviroments. I actually have some long and short stack arms I made up for some limiteds I have to get wound. I was gonna probably at some point sell them as a regular motor (Type SLR and XLR) on the site, but so many choices already to confuse people with, I figured I would roll them out over time.

Later EddieO

[JohnRobHolmes]

Solid armatures simply create heat and drag on a motor from eddy currents as they pass through magnetic fields. I can't think of any positive outcomes of a solid arm, other than cheapness to build. Even the fanciest core materials are still made into laminations to reduce eddys as much as possible.

Look up eddy brake on google. A solid core would be a highly effective one.

[Charlie-III]

Thanks for the info guys, all of you. I didn't even think to Google it, figured it would be a bazillion returns on the search.

As an aside, checked over my new (to me) Hudy comm lathe last night. Checks out square and fairly snug. Did a test cut on a roasted comm, bit cuts well.
Good thing I still have quite a few 4 cell NiMH packs for my 12th pan cars, they make good supplies for the lathe.
Guess I will be cutting working comms tonight.

[JohnRobHolmes]

Wear some safety glasses, the copper shards can throw off pretty far even at low facing speeds.

[Charlie-III]

Originally Posted by JohnRobHolmes

Wear some safety glasses, the copper shards can throw off pretty far even at low facing speeds.

I do, I've worked with "spinney things" long enough to know. Thanks for mentioning though.

[JohnRobHolmes]

I figured you knew, but maybe somebody else browsing the thread does not.

[Charlie-III]

Originally Posted by JohnRobHolmes

I figured you knew, but maybe somebody else browsing the thread does not.

That is why I did a .... ..., for anyone else that likes to see in stereo....

[JohnRobHolmes]

I do rather enjoy 3d vision.

[Charlie-III]

OK, what do you guys prefer to use for arm spacers?
Metal washers (any specific material....brass, steel, ?...)
Plastic (Nylon, PE, ?....)
FIber

Does it depend on thickness of spacer (thin is metal, thick is plastic, ?)

Are these motor specific items, or hardware/electronics bits?

I usually look to see where the arm wants to sit in the field, then reduce float end to end with spacers. I try to keep "float" down to a few .000's, too tight seems to kill some power and can get worse when everything gets warm. A little extra float always means there is some gap even when the motor is real warm.
Do you tend to "force" the arm to a specific spot or do similar to what I do?
If you do different from me, may I ask why (and get a response)?

Just looking at some of the motors I have and know some need some spacing done on them.

[EddieO]

For most motors, I just stick to the standard .010(Brass), .015(Steel),.020 (Aluminum).....I do have teflon, rubber, and others.....but honestly, I don't use most of them. Sometimes I will use rubber on the Onslaught or the V2 when I build them. The teflon aren't easy to find and really the teflon was for a bushing motor.

The Fiber (aka Phenolic) is meant for the top of the comm, though I have seen some brain surgeons use it on the bottom. The whole point of it is to insulate the comm from the bearing, so it won't short out. I've never found this to be needed, but I use them on every motor pretty much that goes out the door.

I used to get all my washers from trinity........they used the three colors so they were easy to tell apart....plus if you always try to put the aluminum or brass on last, it won't pull them off because of the magnets.

Phenolics are pretty motor specific, but the others are just washers made here in the states by a big washer company.

The float method is what I use.....but its really less critical in a modified motor than in a stock that has weaker magnets....though I guess the cheaper integy lathe motors could use it.

You are aiming for a tick of play really....less you can get the better. I get all production motors down to little of play, but I don't get massively nuts with it like I used to for team race motors back in the day. One trick you will learn is a good TAP. Once you think you got it spaced...give it a solid (and straight) tap on hard surface on the shaft. This will help compress any additional play in say the bearing or the bottom washer on the motor (plastic one). Like I said, TAP....not a slam....think Happy Gilmore....just TAP it.

I can tell you that MOST motors space the same on the float for the bottom....its typically the top that differs as the comm can be a mm or so higher/lower on a motor. Sometimes though the washer on the bottom (plastic, typically black or tan/brown) or even the laminations can be slightly different from arm to arm, hence why spacing can differ...........then of course the magnets can be different heights too.

Later EddieO

Originally Posted by Charlie-III

OK, what do you guys prefer to use for arm spacers?
Metal washers (any specific material....brass, steel, ?...)
Plastic (Nylon, PE, ?....)
FIber

Does it depend on thickness of spacer (thin is metal, thick is plastic, ?)

Are these motor specific items, or hardware/electronics bits?

I usually look to see where the arm wants to sit in the field, then reduce float end to end with spacers. I try to keep "float" down to a few .000's, too tight seems to kill some power and can get worse when everything gets warm. A little extra float always means there is some gap even when the motor is real warm.
Do you tend to "force" the arm to a specific spot or do similar to what I do?
If you do different from me, may I ask why (and get a response)?

Just looking at some of the motors I have and know some need some spacing done on them.

[Charlie-III]

Thanks EddieO.....when you talk about "top" & "bottom", I'm assuming the "bottom" is the comm end vs. "top" is the opposite end of the arm?
I can see why there is a difference since the bottom is a little more precise material to work with with less variables.

[EddieO]

Top=Comm Side
Bottom=Pinion side

Later EddieO

[EddieO]

People slacking on this

http://www.ebay.com/itm/Fantom-Motor...item3cbb559655

The diamond bit alone sells for $100 still from Carter Diamond...

Later EddieO

[TEDROCKZ]

^^^Saw it earlier. Pretty sweet deal!

[rock hard]

any ideas on how to stiffen the springs besides bending.....any heating methods?