# Ohming Arms



## coach61 (Sep 6, 2004)

When Ohming arms which would be better..

16.1 , 16.5, 16.4

OR!

17.0, 17.0, 17.0

Wasn't sure if the lower arms even though all diffrent would be faster (Potentialy) then a even one.. I imagine the 17.0 arm would be smoother am I correct in this thinking?

Thanks in advance

Dave


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## martybauer31 (Jan 27, 2004)

Hopefully Tim Leppert will reply to this as he I'm sure knows better than I, but I have found that it doesn't seem to be how they ohm out, even or not, low or high, but how well they spin up.

You can actually hear the difference if you spin up a good arm with just brushes, magnets and a top plate.

I have a Christmas tree arm that ohms out at 17.8,18.5,18.1, but blows away anything else in my box, including those 16.0, 16.0, 16.1 arms that people like to tout.


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## AfxToo (Aug 29, 2003)

Whichever one is better mechanically balanced would likely be better.


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## Bill Hall (Jan 6, 2007)

Response to electrical input and mechanical ballance are what I look for. If it pipes up nice I like it!


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## Dragula (Jun 27, 2003)

stick money on the 17.0,then if you have to,get it balanced.Galinko and I speak maybe 2 times a week,and we both agree,hopefully Tim will chime in with his .02 worth.
DRAGjet racing


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## afxgns (Jul 6, 2006)

I would go with the higher ohm one first, But I would balance both of them just to be shure.
There are so many things that can go wrong with these things that it's hard to say without listening to one rev.
First check a few things,

Look at the winds, be shure they are even and there are no loose tags.

Look at the com, if it's got crosshatching on it, it's new, or almost new.

Grab the shaft on top with a small pair smooth faced pliers, and squeeze genly, then try to spin the stacks on the shaft. Not too hard,just be shure that they don't spin free, this happens alot, and will drive you nuts when trying to balance. Sorry there is no fix for this , paint it white and throw it in the junk pile.

Good luck
Tim Leppert


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## Dragula (Jun 27, 2003)

Guys,I go thru 100 to 200 arms a month,more than probably anybody else out there even gets close tne thing you gotta learn about arms..there only 1 piece of the puzzle!!Magnets,gearplate,chassis,shoe set up,spring tension etc..All has to be right.I dont have time to type it all up.So look at Tim's FRAY tuning tips,hell,maybe I can pick up some cool new tip!Just my .02
DRAGjet


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## A/FX Nut (May 28, 2004)

Well I don't race the Fray cars but, everything I've heard or read about armatures is you want them to be equal in ohm readings, the com plate has to be as level as possible, and well balanced. ( If rules allow it can be balanced by grinding material off of the heaviest lamenants. )

This would go for any pancake motor racing class. Like Chris said, armatures are just one part of the puzzle. 

I love these kind of post, I learn something new everytime. :woohoo: Randy.


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## coach61 (Sep 6, 2004)

Thanks for all the tips.. I have been working and using them but not being a tjet guy to start with this mail in race may just be a learning experiance for me. and learnings a good thing right? lol...the 17 was better balanced by a long shot and looks to be a lot better shape so I am going with it in the main car just looking through the pile for a straight chassis which is a lot harder then I thought it would be. I have a pair of very matched magnets for the car and new brushes and shoes. So baring my inability to put on rims straight I should at least not be over embarrassed..lol.. But who cares its all fun...

Dave


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## Ragnar (Aug 22, 2006)

A simple formula is: The lower the ohms(resistance) in a coil(armature winding) the higher the Magnetic flux created by the coil at a set voltage.That is why we rewind with larger guage wire and/or less turn of wire on the armature poles. If you increase the magnetic field of eack pole,and you balance the armature correctly, and you get the timing right for the track you are running on and the comm trued you will have a great armature. The you need strong, match magnets, that have been trued and and then setup centered in a trued can with the gap set to suit your race conditions. The can and endbell bushings seated true and fixed with glue for the endbell, and soldered in the can end. the armature centered and shemed. The brush hoods trued and aligned. a set of low resistance motor brushes installeh with matched brush spring tension( the higher the rpms the stronger the brush springs). 
Cheers!
Tom


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## Ragnar (Aug 22, 2006)

Sorry didn't mean to get so carried away with the above post. The above comes from my experience with building can, and strap motors, I most admit that I have never built a pancake motor.

Tom


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## afxgns (Jul 6, 2006)

Ragnar said:


> Sorry didn't mean to get so carried away with the above post. The above comes from my experience with building can, and strap motors, I most admit that I have never built a pancake motor.
> 
> Tom


It's all good dude,
The same applies for these things. The only thing different is the limits placed on us by the chassis.

I just want to impose on folks that you need not discount an arm just because the ohms are "too high".
Check out the ohm readings on the fray entered cars elsware on this board.
High ohm readings can be a good thing when it come to 9 tooth t-jets.

Tim Leppert


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## AfxToo (Aug 29, 2003)

Tim's right. My absolutely best inline arm in my box right now is a $3.00 stock Tyco 7.2 ohm arm. It's freakishly strong and runs very cool. You never know. Picking good arms is an art more than a science.


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