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Air gaps - when to run less and more?


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#1 Robert BG

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Posted 13 June 2016 - 08:56 PM

When I used to race before I was lucky to have enough motors to send a arm out for service  and still be able to race etc. But now I've stumbled into a nice collection of motors and I have some tighter and others with bigger gaps.

 

So why would you want to run a motor with less air gap?For ex a .500 arm with .512 instead of .515,.516/7 and so on.

 

I've searched a bit and really only found recommended gaps for things with no real explanation behind them.

 

There has to be a time when going with less or more is a advantage.Is it tied with timing or power or both etc.

 

Thanks,


Robert Fothergill




#2 Fast Freddie

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Posted 14 June 2016 - 11:42 AM

Here's a easy way to figure out what air gap, however, it comes with a "but" that you need to pay attention to.

 

-High timed arms 40+ like smaller air gaps .005 -.007 usually.  Mainly because they develop less torque than low timed arms.  This increases chances of overheating.

-Low timed arms 38 and less like bigger air gaps .008-.012 usually.  Since they produce more torque it allows them to spin up faster.  No real overheating problems.

 

Now here comes the "but", but this isn't always the case.  Magnet strength, can design and integrity, and armature efficiency all play a part in how well the motor runs.  Not to mention track power.  I have also seen high timed arms that just loved larger air gaps and low timed arms that would run better with tighter air gaps.  So what I said above isn't always set in stone, more like loose dirt.  The only way to know is to build identical setups using different air gaps and then try arms with different timing in each to see what works best with what you have.


Fred Younkin

#3 idare2bdul

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Posted 15 June 2016 - 12:59 PM

The problem with motors is that there are a lot of variables, so that you may have changed something like spring tension or a brush or the armature spacing or maybe the motor would have worked fine by changing one of those other variables or adjusting gearing or breaking in the motor differently.

 

With air gap magnet type, track power, track type(high speed or technical) all play into the equation. It can be hard work and expensive to really nail down a good combination. This might be why there has always been more chassis builders than motor guys. It can be very difficult sometimes to see what you did right or wrong and to get repeatable results. Very few of us have dyno's ( I don't) and even those that do, can't be expected to duplicate a particular tracks power.

 

As for air gap too tight or too loose can both cause a motor to over heat making life even more fun.

 

I like motors but I would never have the patience to do what John Havlicheck does with his builds. I didn't let my sponsors talk me into winding arms and found balancing them stressful, tedious and boring. I'm glad there are people out there that are willing to do the things I can't or won't do for our slot car motors. 


The light at the end of the tunnel is almost always a train.
Mike Boemker

#4 Robert BG

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Posted 16 June 2016 - 02:22 PM

Thanks guys,I've got 6 almost identical Koford setups to experiment with.They all have the same mags matched pretty well,one already has a little bit tighter of a airgap than the others,2 have have my normal gap and the other 3 one is a hair under and 2 a hair over what I used to run.So it's a pretty decent spread to play with.I just wanted to make sure I was using arms with timing that is better matched to them to start with.I know it may not work out that way but still.

 

Since I finally got my chassis dialed into the track and now it's time to look for horse power :)


Robert Fothergill

#5 Zippity

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Posted 16 June 2016 - 03:03 PM

Robert,

 

Don't forget to report back here with your findings.

 

I will be interested to know the results :)



#6 Robert BG

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Posted 16 June 2016 - 05:46 PM

Zippity,it'll be a while but I'll try.I've got mostly 40* arms so I'm probably going to load them all with them first and see what happens. Although  I'd really like to run the same arm through my smallest to largest gapped motor.But this will get me started for now.


Robert Fothergill

#7 bigdanbo

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Posted 16 June 2016 - 08:15 PM

Thanks guys,I've got 6 almost identical Koford setups to experiment with.They all have the same mags matched pretty well,one already has a little bit tighter of a airgap than the others,2 have have my normal gap and the other 3 one is a hair under and 2 a hair over what I used to run.So it's a pretty decent spread to play with.I just wanted to make sure I was using arms with timing that is better matched to them to start with.I know it may not work out that way but still.

 

Since I finally got my chassis dialed into the track and now it's time to look for horse power :)

 

My experience is first, you have to to have the identical killer arm in each setup or identical turds to do a proper experiment. So many variables or maybe the same arm in each setup.   


Dan Ebbert

#8 Robert BG

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Posted 17 June 2016 - 10:56 AM

Dan,that is why I said it is going to be a while ;)  For now I'm going to see how they like hand wound 40* timed arms that all meter very close and have few balance marks.Once I get a few new arms I'll probably run the same one through all 3 gaps and adjust the timing via the endbells to dial things in even more(I have reg and +4 endbells for most of them) with the same arm and different timing.But stuff like this takes time and I dont have a arm that I think would survive running all the setups while cutting the coms.So I'm just trying to get a baseline for further tests and if I find a rocket I'll pull it for later.


Robert Fothergill

#9 bigdanbo

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Posted 17 June 2016 - 08:16 PM

Dan,that is why I said it is going to be a while ;)  For now I'm going to see how they like hand wound 40* timed arms that all meter very close and have few balance marks.Once I get a few new arms I'll probably run the same one through all 3 gaps.

 

Been wanting to do this also. I live an hour away from nearest track so it makes it difficult for experimenting.  :good:


Dan Ebbert

#10 Robert BG

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Posted 18 June 2016 - 11:54 PM

Well my smallest gapped motor didnt like the 40* arm I tried,I'll try another but I'm not expecting much.The first was 40 on the money and the second one is 41*

 

Setup is a .512 gapped Buef built Int 15 Koford can,Koford big radial mags.First arm was a hand wound Koford .500 40* second will be a  Proslot hand wind @41*

 

I've decided to just use Koford cans to reduce variables but the one Camen with the same mags and a .515 gap and a Koford arm like the other was a rocket.Same car,chassis etc it ran a 3.190 on a 220 ft englman,the Buef built ran a 3.315.

 

Before I throw another arm in it if I can get my friends lathe I'll skim the coms and swap the arms between the 2 and see what happens.

 

I'm also loading the other Koford setups now,gapped .514,.515 and I have a non windowed can at .516


Robert Fothergill

#11 Koford fan

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Posted 21 June 2016 - 04:06 PM

Iv experienced a lot of difference air-gap.

 

Mostly i run 40 degree tri-star koford .518 armature, but got a couple 42 degrees too.

Iv testet airgap of: .528, .530 and .533

 

But now i love race at airgap .530 and .533, on a cahoza c-can with koford magnet.. they run good in most cases.

Of course, it depens on the armature too, how you setup your motor and so on. Lots of testing to find the good spot.


Tom Blantern

#12 Car-2

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Posted 22 June 2016 - 12:37 AM

I'm about to build that exact setup for a OMB wing. A Koford ceramic magnets and feather can and Koford G12 40 degree arm with that measures .516. I've got a .530 slug so that means .014 air gap. Now my mentor has said this will run good but i am open to opinions. I've not glued them in yet.


Robert Uzzi

#13 Robert BG

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Posted 22 June 2016 - 09:21 AM

Koford fan,I'm starting to really think the tristar blanks like the larger gaps.Most of the motors i got from another racer all had .014-.016 gaps except for one.Now it is a little early for me to say this for sure as I prefer to do my own testing but it really is going this way.

 

Car-2,

I think you're on the right track,especially the more I test the more it appears that the tristar blanks like the larger gaps.I would start with .012 or .014 and go from there.The only reason I'd do .012 is to hone my final size to ,014 so you'll be fine with that slug.Chances are though you may want to hone it out to .015-6 later on.I know it doesnt seem like much but on my 27Lite motors I went from .015 to .016 on the suggestion of another racer (one of the best pro's currently out there) and I picked up a few tenths and more speed on the straight just from .001 more gap.

   I'd definitely start where he suggested but dont be afraid to pick up another can to try a bit bigger gap.I doubted it myself but just a hair bigger can make a world of difference.


Robert Fothergill

#14 Koford fan

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Posted 22 June 2016 - 10:13 AM

yea you just need to test out stuff yourself, see what fits you and how motor runs.. !!!

But more important is to write down wich armature in wich motor (That worked good, most likely will work good next time)


Tom Blantern

#15 Robert BG

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Posted 22 June 2016 - 12:23 PM

Yeah it is very important to keep records.I actually run a new race arm in to make sure everything settles in and send it off for recon and I have them numbered at that time.I've got around 50 I-15 .500 arms at the moment and another 12 .490's so its a excuse to double check the balance and things more so then a necessity to balance new arms like it was before.Although in the past a fresh arm would move a little the first few cycles and the windings would settle in.

Also all of my motors are labeled like Koford 1A,2B,2 C,2 A etc.The number is the style of motor(windowed can,scalloped edges etc etc) and the letter corresponds to the airgap.For instance 1 A is a solid can with .512 gap,this way in my notes I know what arms ran well in what setups.Although some numbers refer to mags like Camen 2 C has koford .500 L radial mags with a .515 gap.

 

It sounds complicated but my notes will say like Camen 2 C # 22 +.12,Camen 2 C # 23 -.12, The # was the arm and the + and - were from when I used to test on a oval on red.I had a benchmark time I used set by one of my faster motors and the + or - was how far off the combo was.Back then I used to race on a lot of different tracks so the oval really took out the driver variable and track conditions for motor testing and let me concentrate on chassis tuning for the big tracks.

 

Chances are I may get a Gerding test track that he makes for this as I dont have the banked oval to run on anymore.But my notes from before still helped when i was getting back into things again.

 

I wasnt the best at keeping records but when I started doing things this way its helped a LOT and there is little room for forgetting a combo.A few quick notes was all it took and if guys wanted to cheat and look at my notes they were clueless as to the setups.Believe me more than a few took a peak at my book while I was testing too.


Robert Fothergill

#16 bigdanbo

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Posted 02 July 2016 - 09:14 PM

IMO, If you hone your mags .015 larger than your arm, you would have a .0075 air gap not .015. In my experience this is pretty close. I have had the stacks hit the mags, due to wear of bushings/bearings and run out of arm. Being this close gives you allot of brake and more torque. Some say more air gap (to a point) more arm speed but less power. T or F?


Dan Ebbert

#17 Robert BG

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Posted 03 July 2016 - 05:57 PM

IMO, If you hone your mags .015 larger than your arm, you would have a .0075 air gap not .015. In my experience this is pretty close. I have had the stacks hit the mags, due to wear of bushings/bearings and run out of arm. Being this close gives you allot of brake and more torque. Some say more air gap (to a point) more arm speed but less power. T or F?

I go by the size of the hole not each side.Right or wrong its how the motors I have from CRP , Buef and other builders are tagged and it's how I've always labeled my air gaps.

 

Also all of them are ball bearing motors and the bearings are changed on a regular basis long before they have any slop in them and the arms are serviced regularly unless I come across a extra fast combo.Those motors are put aside for rainy day use ;)

 

I'm still testing different gaps but at this moment I'm putting together some oddball stuff using old school parts and new mixed together to try some new stuff.Once I get some real track time with the airgaps I have set now I'll assemble some new combos/


Robert Fothergill





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