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Some motor tidbits to consider - for all racers


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#1 havlicek

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Posted 13 November 2017 - 08:06 PM

From time to time I see questions about motors from racers who think there's "something wrong" with their motor. Now, certainly there can be something wrong with any motor, lord knows I've made my share of stinkers. I think all this applies mostly to the sealed/less expensive motor racers though. When you consider how affordable these things are because of mass-production runs, it's amazing how consistent they are, But... the motor itself is only one part of the total "electro-mechanical system" called a car. So, some things to consider:

– Say a car is doing 5 second laps on average, and after a motor change is doing 5.2 second laps. Is the second motor really a "dog"?  The math says no, but unfortunately those two tenths could win or lose a race. That kind of variability in a mass-produced motor that sells cheaply enough so that people will sometimes buy dozens just so they can pick the cherries (oy veh!) seems pretty impressive to me.

 

– It's possible that a slight variation in any one particular motor could be accounted for by a move up or down of a tooth on a spur or crown gear, but who's going to do that and test it with a motor inexpensive enough to just buy another? Besides, it's easier to just call it "a dog."   :)

– How do brushes and springs come into play? Most everyone knows that brushes can be inconsistent from batch-to-batch and have a big impact on a motor's performance. Springs can weaken can have a significant impact on heat, revs, brakes... you name it. That's not "really" a motor issue when you think about it, as much as it is a 'roll of the dice" kind of thing.

– Bushing wear and alignment can turn a "winner" into a real mutt.

– The heat from soldering a motor into a chassis can be significant, especially with neo magnets. When I take these things apart, I often see the magnet on the side that was soldered being down compared to the other one. Can that affect performace? Sure thing!

– The biggie... how does anyone know for sure with certainty that the above two-tenths example is actually because of the motor? Does a gear mesh change over time (rhetorical question)? Does the performance of the entire rest of the car stay exactly the same? Even an issue with a guide flag could cost a couple of tenths.

– And on it goes. Experienced racers who also know motors already know this stuff. My point is that you can chase those two-tenths and never really find them. More so... it just might not even be the motor. I haven't even gotten into a racer just having an "on" or "off" day, the controller or even the track power.   

 

Just sayin' is all!


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John Havlicek




#2 Pablo

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Posted 13 November 2017 - 08:39 PM

Well said, sir.

 

I thought I had cooked an FK type motor at last week's race. It smelled and it got real slow.

Next lane change, I sprayed it with cleaner as a last-ditch effort and slapped 'er back on the track.

She finished the race, although obviously way off the pace.

 

Post-race teardown: failed $3 axle ball bearing. Summary: axle bearing collected a piece of debris, bound the drivetrain up, overheated the motor.

 

Solution: switched to shielded ballbearings of higher quality.

 

It ain't always the motor.

 

Good point, John.


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Paul Wolcott

#3 havlicek

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Posted 13 November 2017 - 08:46 PM

It ain't always the motor

 
I think motor manufacturers hear it's always the motor, Pablo.  :D


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John Havlicek

#4 Ramcatlarry

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Posted 14 November 2017 - 12:15 AM

Never the driver or mechanic...


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Larry D. Kelley, MA
retired raceway owner... (for now)
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#5 havlicek

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Posted 14 November 2017 - 07:32 AM

The thing is, Larry, there's always uncertainty in the mix. It very well maybe the case that a motor is on the low side of the "performance range," but knowing that is not very easy. Even more difficult would be (if someone did know that) figuring out why. These motors are amazing performers considering all things... especially price. 

What you don't hear as much about is that there are motors that will fall more towards the top of the performance range. When someone gets one of those, there isn't much complaining.  :)  I think it's probably true that what we're looking at here is a bell curve of performance characteristics, with the majority of motors falling in the middle of the "bell."

Think about what racers want most. They want a motor that's cheap, fast, reliable, compact, lightweight, and as consistent across batches of many many thousands as possible (although some would prefer if there were stand-outs that only they could get  :D  ).  That these things pretty much do all that is pretty amazing. I have no axe to grind here... I don't race. 

 

Personally, I just see these things as both a great value and know for sure that figuring out what's going on inside of them is really difficult.


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John Havlicek

#6 Eddie Fleming

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Posted 14 November 2017 - 08:02 AM

The truth is that racers want the upper end of that performance bell curve no matter where that curve falls. Even the middle of the curve is a loser to the obsessive racer. It is a no-win situation for the manufacturer.


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Eddie Fleming

#7 havlicek

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Posted 14 November 2017 - 08:06 AM

Bingo!


John Havlicek





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