49 replies to this topic

[Steve Boggs]

What are the differences between the manufacturers laminations? They have different designations, but not much in the way of info on what makes them different or better than others.

[Ron Hershman]

Lam thickness, grade of metal used for the lams, and different blank designs... narrow leg, wide leg, long leg, short leg, crown width, tip thickness.

Then there are different diameters to take into consideration.

Is there a specific "answer" you are looking for?

[NSwanberg]

Thinner laminations supposedly reduce hysteresis and eddy current losses. Good luck quantifying that.

[havlicek]

Aside from the lam thickness and the blank designs, there's also the matter of what alloy steel a particular lam has been stamped from. Motor lamination steel or "electrical steel" is a low-carbon alloy with silicon in it that is used because it has the properties most suited to forming a core from. Also, the way the material is heat treated has a large effect on its final performance as an armature core. There is also something called amorphous steel that is cooled so fast that crystals don't get a chance to form and supposedly has the best properties for this application... but it costs a lot more than regular steel. I'm not sure if anyone in slots actually uses amorphous steel for punching their laminations because of the cost.

The final consideration is the lamination coating. The lams are most often coated to increase resistance between lams, stop or slow rust, and to help with the stamping. Obviously, all coatings are not the same and it could even be that some lams are not coated at all.

None of the above is readily visible just by looking at an armature... it all pretty much just looks like steel. I have done some quick and dirty tests with lams that are the same thickness (most often .014") and have a very similar profile or design and have gotten some repeatable results that would seem to indicate that some arms are stamped from a poor alloy.

It seems to be generally true that the thinner .007" lams also work better than the thicker .014" lams, but I've never had the same lam profile stamped out of both materials to be able to do an "apples to apples" test, so I just take this for granted. Having said that, with the trend towards thinner/lighter lam profiles with more winding space, the .007" lams can become so weak that the arms tend to swell from the force of the arm spinning so fast on open motors, from what I've been told. They can even distort to the point where they contact the magnets and that's not good. Many are apparently back to using .014" thick lams because of this.

Finally (and even though it's not specifically part of your original question), how the arm is coated after assembly is a biggie. The type of coating, how it's cured/post-cured, and how thick it's applied are major. Again, you really can't get an idea about this from just looking at an arm because it's all hidden. You really only need as much coating as it takes to insulate the core and to remain stable at high temps. Any more than that is a waste and can have a negative impact of performance. I kinda doubt that any manufacturer is going to share the nitty gritty details of the lams they use so, as a consumer, you're left with using whatever seems to work the best.

... Then there's the whole question of shaft material.

-john

[NSwanberg]

I could not find a can of worms smiley.

[havlicek]

What "can of worms"? When someone asks a question, I take it for granted they actually want to know... and deserve to know, everything I've learned from others about it.

-john

[Steve Boggs]

Lam thickness, Lam Grade of metal used, and different blank designs...narrow leg, wide leg, long leg, short leg, crown width, tip thickness.

Then there is different diameters to take into consideration.

Is there a specific "answer" you are looking for?

Well, I would like to know what the difference is between the Pro Slot Intruder and M2 blanks, and the various Koford blanks.

In this case, a little information is a dangerous thing!

I recently found out just how much difference the laminations make to the ability of the armature to generate a magnetic field. Lams are one of the elements of motors that you really can't do much about unless you order a custom arm. I was always wound up in chasing air gap and timing and all the little things that you can toy with, but the lams are in control of a lot of how the motor runs and it opens up a whole new avenue for building motors.

[Steve Boggs]

What "can of worms"? When someone asks a question, I take it for granted they actually want to know ... and deserve to know, everything I've learned from others about it.

Thanks for all the information, John!

[Ron Hershman]

Well, I would like to know what the difference is between the ProSlot Intruder and M2 blanks, and the various Koford blanks.

I recently found out just how much difference the laminations make to the ability of the armature to generate a magnetic field. Lams are one of the elements of motors that you really can't do much about unless you order a custom arm. I was always wound up in chasing air gap and timing and all the little things that you can toy with, but the lams are in control of a lot of how the motor runs and it opens up a whole new avenue for building motors.

The Intruder blank versus the Koford .513" blank are very similar in leg width and length. Both have a tad different "crown" profile and Koford and P-S both use .014" lams for these arms and both use a different grade of material.

The M2 blank has a narrower leg width and a bit different in the crown profile when compared to a P-S Intruder blank.

The Intruder makes more torque than the M2.

If we are talking .513"-.518" dia X12 arms here... 50 turns of 29... and if both are timed to 42 degrees... the Intruder will run cooler and make more torque. The M2 will run hotter have less torque and make more RPM.

It has been my experience that if road racing Box Stock 12s in glue... Intruders are the way to go... less heat and more torque. If racing in spray glue M2s will run fine if you reduce the timing. Reducing the timing will make them run cooler and make a bit more torque. In scale racing there has been lots of success with both the Intruder and M2 blanks. In wing glue racing Intruders are the way to go.

Which is better Koford or P-S??? One will be better than the other depending on the application they are being used.

The same would go for any wind (Contender, 20, Super Wasp, S16D/C) when talking about the P-S blanks.

Yes, .007" arms run better than .014" arms on the same blank, same winds, etc. When I worked at RJR we offered both and the .007" lam arms outran the .014" arms and we sold four .007" to every .014" arm.

.007" lam arms in the lower classes are not available as the material is three to four times more expensive than .014" lams, takes twice as many .007" lams as it does .014" to meet minimum stack length dimension and is a production nightmare when stacking the lams before pressing the shaft. This is why you don't see .007" lam arms available in anything lower than Opens any more.

When it comes to .500" and smaller arms it's a whole different story as both Koford and P-S have various blanks... Group blanksopen blanks in several styles and lam thickness.

[Phil Hackett]

.007" lam arms in the lower classes are not available as the material is three to four times more expensive than .014" lams, takes twice as many .007" lams as it does .014" to meet minimum stack length dimension and is a production nightmare when stacking the lams before pressing the shaft. This is why you don't see .007" lam arms available in anything lower than Opens any more.

Why did Mura make everything with .007" laminations if there are so many problems doing so? Bob and Woody must have known something that no one else has figured out.

[Rick]

One issue today is manufacturers of lamination material only roll down to .014" today. One place reworks the material down to .007" (Arnold Enginering). We stopped making .007" years ago at ATI and Armco did, too. The steel is rated as PG, SG, etc.

Coating makes a difference on the lams also. There are "other" things to do that makes it better.

[Ron Hershman]

Why did Mura make everything with .007" laminations if there are so many problems doing so? Bob and Woody must have known something that no one else has figured out.

Two reasons that Bob told me... one was performance... two was back in the day... .007" material was more widely available and not much more money than .014"

When .007" tripled in cost... Woody switched to .014".

Two slot arm manufacturers purchased the last bit of .007" lam stock that Woody had.

In 1995... .014" was a little over 2 bucks a pound... .007" at that same time was close to 9 bucks a pound.

Last I remember in 2000-02... .007" material was close to 14 bucks a pound.

The sad part of making laminations is that almost half the strip material goes in to the trash... material comes in a strip... lams get punched out of the strip and what's left becomes scrap.

[Mopar Rob]

Ron:

If my memory is correct, didn't Mura have a "pro line" or some other name in the mid-late '90s? If I'm remembering correctly they were .007" lamination arms wound by Pro Slot on the CNC winder?

[Rick]

The sad part of making laminations is that almost half the strip material goes in to the trash... material comes in a strip... lams get punched out of the strip and what's left becomes scrap.

Yup, you pay for the whole cow but only get the steaks... LOL.

Good stuff is sold by the pound, scrap is sold by the ton.

[Ron Hershman]

If my memory is correct, didn't Mura have a "pro line" or some other name in the mid-late '90s? If I'm remembering correctly they were .007" lamination arms wound by Pro Slot on the CNC winder?

I don't recall that... not saying it didn't happen but if it did I sure as heck have forgotten that... LOL.

[NSwanberg]

What "can of worms"? When someone asks a question, I take it for granted they actually want to know... and deserve to know, everything I've learned from others about it.

No offense intended. Just meant the discussion about motor specs and theory could go on and on...

[havlicek]

No offense intended. Just meant the discussion about motor specs and theory could go on and on...

None taken. You are right though. Even just this one aspect (laminations) has a LOT going on, but it's always been my belief that knowing as much about something as you can is a good thing.

In this case, the motor manufacturers aren't going to tell you all the details first because some of it is proprietary and second because some of it might not help their bottom line. We're left with just trying to see what works best and go with that. If the people who consistently win are using a particular arm, and you're confident that you have everything else worked out... it makes sense to try what arm they're using.

Even so, knowledge is power.

-john

[Phil Hackett]

Ron,

It's great that you explained why Mura went from .007" lams to .014" lams, that is a good reason but has nothing to do with your statement that .007" laminations are hard to produce armatures from. Seems to me that Mura had no problem making armatures with .007" lams.

[wbugenis]

Robert Root had a sliding fixture built on a small arbor press that would dump the "correct" number of lams into a spaced hole and then slde the stack under the ram to press the shaft. If not adjusted perfectly, the thin lams would jam between the sliding bar and the statonary part that held an 18" rod of laminations. Pain in the butt to clear.

I have an idea: lets have a design contest for a laminaton stacking fixture.

[havlicek]

Seems to me the reloading folks have a pretty good solution, Bill. Something like the Dillon 550 progressive reloader (great machine) would seem about right. First station dumps lams from a vertical tube feed into "dummy tube" (whose ID is maybe a few thousandths over the OD of the lams) of the intended stack length. Second station presses the shaft and the third station ejects the .510 cal er... arm blank.

Besides everything being perfectly centered and true on the turret, the dummy tubes would need to be made up. I figure these would also sorta look like an empty cartridge case with a bottom plate and a center hole just larger than a shaft and have some sorta guides built in for keeping the lams straight as they fall. What do I win???

-john

[wbugenis]

Gettng the stack length quickly and accurately is the issue. Not sure that machine can address that issue.

[Ron Hershman]

Ron,

It's great that you explained why Mura went from .007" lams to .014" lams, that is a good reason but has nothing to do with your statement that .007" laminations are hard to produce armatures from. Seems to me that Mura had no problem making armatures with .007" lams.

For the reasons Bill posted (he beat me to it). I never saw how Mura's deal was set up as it was done "out of house"... Mura paid for blanks that were correct and the bad ones... well, the shop making them ate the bad ones. Mura's stamping house also made the blanks for Mura. Mura then coated them in-house and finished them in-house (except for the hand winds that Bob did at home while watching TV) LOL. So technically Mura had no idea how hard it was to make .007" blanks as they didn't make them in-house. Bob Green knew, but it wasn't his problem... it was the supplier's problem.

I never said "who" (did ya notice that, Phil? ) had problems making .007" lams... I just know firsthand and two other manufacturers who stopped making them for lower end production stuff for the reasons Bill mentioned.

So it goes like this... back in the late '70s and until the early '90s Mura ruled the lower end market with .007" lams simply because no one else went after that market. When Mura was sold and over time other manufacturers came in and made new blank designs that even with .014" material outperformed the Mura .007" blanks. It wasn't much past 1992 that Mura was in trouble due to their competitors having better product. In two years we went from all Mura arms in a couple of classes to no Mura being ran at all as other manufacturers had taken over that market with less expensive material and easier assembly of blanks.

[Ron Hershman]

Gettng the stack length quickly and accurately is the issue. Not sure that machine can address that issue.

Easier said than done.

[havlicek]

Gettng the stack length quickly and accurately is the issue. Not sure that machine can address that issue.

Sure it can, Bill... next time we talk on the phone, I'll describe it. Heck, I could even make it, but it would have to be made out of wood.

-john

[Ron Hershman]

Make sure you take into consideration... the "spring" of the material (which varies from different thickness material), the unflatness of the material, and allowances for burrs and strange edges from the stamping from time to time.