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Old 06-13-2008, 02:50 PM   #1
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Default Question for the brushed motor guys

Help me understand...I've always heard that single wind motors have more torque, but our experience has been that a 10 single feels soft on the low end, especially in a truck, but will pull wheelies in the straighaways while a 10double will shred the tires all the way through the RPM range.

We tried gearing the singles both lower and higher; bigger pinions make them overheat with little appreciable gain, smaller pinions do help move the torque band down some but still not enough to. What gives?

Our 12S and 12D comparison had the same results, we also tried both flat and roundwire and, as expected, the flatwire definitely rips harder on the low end. Triple winds which are supposed to be smoother were simply a huge disappointment with no top end at all. I've gone to single winds only on slick tracks, and they definitely help.
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Old 06-15-2008, 12:43 AM   #2
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There is much more to a modified motor than whether it is a single, double, or a triple etc. As someone who had access to factory equipment across the board in off-road racing, I've gone through and tested from what seems like over hundreds of armatures, and done all kind of things you can think about with them to get them to perform at their very best.

You didn't say if you were using machine wind armatures, but that makes a difference as hand winds are much neater and tighter packed, as the wires are layered up nicely over the machine winds that tend to be a bit sloppier. That account for some of the differences, slightly of course.

However first real step is to (aside from whether it is machine or hand wind), first pay attention to see how much total circular mill value (CMV) you have. That is, how much copper is packed in the armature per the wire strands that is wound on them by the person hand winding them. For instance you can have two modified motors that are 10 doubles, but perform very differently from each other. For instance a 13-Triple wound with low mill value (smaller gauge wires take up less space on arm) would perform very differently from a 13-Double wound with high mill value (bigger gauge wires are near full on arm), when used in a 2wd off-road car etc.

That would be the case when their wire gauge varies differently. A 10 double with smaller wire gauge would pack (fill up the empty space) on the armature less, rather than say a 10 double that utilizes a larger wire gauge what would almost fill out (max out the empty space) on the armature. This is not to say either one is good or bad, but to know the performance differences is what comes in. Itís more of a performance thing, and what you want from either armature.

With that in mind, go back and note the circular mills values of the armatures you own and mentioned above first, before going to the singles, doubles, triples route etc, and see how they feel different on the track from one to another, and compare from there in your notebook. Youíll quickly see how heavier armatures spool up differently from their lighter counter parts depending on how itís wound. I believe you'll find a lot of your answers from there.

Those are the huge main differences to consider first, 1.) CMV values based on copper wire gauge used to wind the armature ,2.) winds selections of single, doubles, triples before going on other routes of 3.) timings, brushes selections, springs choices that work best with each armatures used.

Hope that helped to clarify some to start with for now.
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Old 06-15-2008, 07:26 AM   #3
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Lower winds more top end. (Single wind)

More winds more bottom end. (Tripple wind)
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Old 06-15-2008, 10:24 PM   #4
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4WD racer - I've never heard of CMV before, nor seen it listed on my packages. How exactly would I go about determining that value?

The comparisons were done as scientifically as possible by using the same trinity D5 can with 20 degrees advance timing and the same brushes and springs, athough the springs were tweaked slightly for each armature:
Trinity 12D and 12S roundwire machine wound armatures
Trinity 10D and 10S flatwire machine wound armature

Changing to a D6 can made no appreciable difference. All motors performed best on both the track and dyno at approx 20 degrees advance, but had longer run times and were much cooler after testing with timing held at 12 degrees. I've had similar results with Epic and Reedy mods.

OG- that's exactly what my experience has been but some old schoolers keep telling me I'm wrong.
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Old 06-15-2008, 10:26 PM   #5
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other way around man...

a 10 single will blow up a 10 triple...

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Originally Posted by OG RC 10T View Post
Lower winds more top end. (Single wind)

More winds more bottom end. (Tripple wind)
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Old 06-16-2008, 03:23 AM   #6
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CMV is an estimated value that you'll have to calculate yourself, as it's not provided by the manufacturer, of the total value copper wound on the armature. It's easy to do visually as I explained in my above post. However in your case, just keep things simple, and say for instance this armature has low CMV, or medium CMV, or high CMV etc. (FYI, only compare CMV's within the same turns. Don't compare CMV's of 10 turns to those of 13 turns etc. Just compare CMV's within the 10 turns, or within the 13 turns etc.)

An armature that is fully packed with copper has high CMV, and an armature that is low packed (lots of visual gaps between each pole) has low CMV etc.

FYI, about singles and triples (about which has higher top end, or which has more acceleration) in reality singles or Doubles can go either ways regardless. First as I explained, consider the overall total copper CMV values (do this yourself visually to get an estimate whether it is low, med, or high), then second, consider the winding set-up (whether it is single, double, triple, or quad) in that order.

Think about this way, a heavier armature with a high CMV takes longer to accelerate and reach top end (a 10-single can have a VERY high CMV value if a big wire gauge is used), and similarly a lighter armature (a 10-triple with a low CMV if smaller wire gauge is used correctly) has the capability to out accelerate and pull harder out of the corners throughout the entire powerband range.

So for this reason depending on wire gauge used (which determines the overall CMV) a 10-single with a higher CMV, will not always out accelerate a 10-double or triple with very low CMV before it etc. In fact the 10-double/triple with lower CMV can be geared more aggressively and produces more overall power throughout the entire powerband range for this reason, than the higher CMV 10 single that can feel softer with less snap & smoother throughout the powerband range off the line etc.

For this reason, a H-CMV 10 single can be considered smoother/softer/easier to drive and more suitable for dusty off-road tracks, and L-CMV 10 double/triple can be considered better for clay high bite tracks where they have more acceleration/more overall power throughout the entire powerband range etc.

That is the simplest way I can explain it without showing you the differences in person. Those’s why I said there is much more to a modified whether it is a single, double, or triple to consider in my original post. Always consider the total CMV (Circular Mill Value) of the armature first, before moving on to the winding selections, as that is the correct order of steps to follow in order to make the best selections for your given application.
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Last edited by 4wd Racer; 06-16-2008 at 01:24 PM. Reason: grammar
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Old 06-16-2008, 09:05 AM   #7
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Look at these pictures to help clarify, the images tell the story.

All of these armatures are 13-turns. From low CMV on the left, all the way to high CMV to the right. etc. Same thing as if they were 10 turns far as your application goes etc.
Attached Thumbnails
Question for the brushed motor guys-100_1921-13-turns-cmv-cropped.jpg  
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Old 06-16-2008, 10:31 AM   #8
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Thanks for the visual, 4WD, that helps. It does makes sense that the lighter arm would spool faster from an inertia standpoint when not under load, and that the increased amount of copper will give more torque. I remember making electromagnets out of 10D nails in science class back in the day and the most powerful magnets always had the most layers of copper wound on them - up to a point. Back then we only had one size of wire to play with so I had no other point of reference.
Top end seems similar on double and single winds, (all three triples I tried were disappointing for RPMs) and I can now appreciate the concept of CMV as a contributing factor.

Any thoughts on a larger vs smaller comm diameter? I saw a thread a long time ago on that but don't recall the outcome.
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Old 06-16-2008, 01:19 PM   #9
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Not a problem at all, as Iím more than happy to help. FYI, the armature on the far right has six strands per pole! As you can see it's pretty packed full, but harder to wind.

About your questions about small comm v.s. big comm. Thatís inevitable as each cut you do the comm gets smaller, and once it reaches the size of .270 its almost done, from the .292-.300 starting point when new, but you can try push it very slightly past that but not much more.

In general, keeping it simple as possible, small comm has more rpm, slight loss of torque, may have to gear one tooth or so less.

Bigger comm has less rpm, slightly more torque, and can keep same gearing or higher on the pinion.

That's pretty much the trade off of it.
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