# testing with ohm meter



## iRace (Nov 5, 2008)

I'm interested in testing the arms of my tjets with an ohm meter. 
Is anyone willing to explain how to do this?


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## martybauer31 (Jan 27, 2004)

Find something steady to hold your arm in place, I like to poke a small hole in a cardboard box and place the arm with the poles up in the hole.

Take your multi meter and set it to read ohm's.... touch one tip to the middle of one pole and the other tip in another one and take your reading. Repeat for the other 2 combinations of poles and you should have a good idea of what your arm will ohm at.

That being said, while ohming the arm is a great way to make sure it's within the rules of whatever you may be racing, it's not a good way to tell if you have a good arm.

I have some arms that read out at 17.9/18.2/18.5 that will smoke any arm in my box that is at 16.0/16.0/16.0.

So check the readings and then run 'em to know for sure if you have a winner.

Marty


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## tjd241 (Jan 25, 2004)

*What Marty says and....*

If there is a build up of oxidation, oil, etc. it could prevent an accurate reading. A clean arm is a happy arm. nd


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## Mexkilbee (Apr 17, 2008)

I just flip an old chasis over and put the arm (upside down) in the arm hole of the upside down Chasis, holds them pretty good. I check them the way Marty31 does, on the soder of the pole, to many fluctuations when you check on the face. use a basic Ohm meter, fancy AutoRanging meters have been stumped (in my exp.). 
Like Marty, I have some arms that are in the 20's, and they rip with stock mags, they are dogs with JL Mags, I think it's the whole Carb/Cam Combo thingy...


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## Bill Hall (Jan 6, 2007)

tjd241 said:


> If there is a build up of oxidation, oil, etc. it could prevent an accurate reading. A clean arm is a happy arm. nd


Dats how ya do it. 1-2-3 go!

Nuther Daves little picture sez it all.


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## ropes (Jan 30, 2008)

Ever see a new X-Traction arm have a 4.3, 14.3, 11.3?


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## dlw (Aug 17, 1999)

Whoa, something's wrong there, Ropes. Does the car run ok?


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## ropes (Jan 30, 2008)

DLW, Its the slowest thing I have ever seen!!! It wont even get past the TOMY lap counter track!!! The car works fine with another arm.


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## majdave79 (May 31, 2006)

Typically if you have one low arm and the others are off the chart, it's a broken wire near one of the poles.

Here's a link to Victor's web page on testing arms (lots of pictures!)

http://www.netfixer.net/slots/arm.html

Dave


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## dlw (Aug 17, 1999)

Like Majdave says, it's a busted arm. If you're good at rewinding arms, you've got a nice blank there for a project.


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## iRace (Nov 5, 2008)

Ooops new thread


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## Hornet (Dec 1, 2005)

Touch your probes together first to get a baseline reading from your meter.If you're not using an auto ranging/self zero'ing meter,most meters will give you a reading from the bare probes ,this reading has to be calculated into your final reading


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## Ligier Runner (Nov 29, 2004)

I'm in the camp of the "magnet/arm combination is important". I've got a few gold wire/red tip arms that don't "ohm out" as anything special yet they scream pretty nicely with the magnets they're mated with. Got lucky on those.


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## GoodwrenchIntim (Feb 22, 2005)

Ligier Runner said:


> I'm in the camp of the "magnet/arm combination is important". I've got a few gold wire/red tip arms that don't "ohm out" as anything special yet they scream pretty nicely with the magnets they're mated with. Got lucky on those.


I have to agree, I dont think OHMing an arm is the most important thing, some of mine that OHM different from pole to pole smoke ones that do OHM the same(magnet cars). In fact I think someone said the fastest frey arms where the xmass tree arms that OHM all over the place. Its all in the arm/magnet combo


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## Bill Hall (Jan 6, 2007)

I'm in the hand grenade is close enough camp myself. While electrical ballance soothes the worrisome mind, I'm looking for response on the test pad and results in the tire frying department. Does it pipe up fast and sing a sweet song is what I really wanna know.

For me the meter is a more of a continuity check for opens and the rough "ohmage" tells me if I've got a direct. Splitting hairs on the decimal point is fun for the pigeon holing types with a shiney new Fluke-o-meter, but I've often found some very nice Arms in SOE's cast off lots that were a little "iffy" on the resistance ballance.


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## BrentCorvette (Jun 11, 2008)

Testing the balance of an arm is just as important as checking for low ohm's.


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## WesJY (Mar 4, 2004)

does anyone know how to test the ohm on tyco 440x2 armature? 

Wes


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## martybauer31 (Jan 27, 2004)

WesJY said:


> does anyone know how to test the ohm on tyco 440x2 armature?
> 
> Wes


It's essentially the same principle, it's just that the poles are so much tinier. You will notice there's 3 of them, just do it the same way you would with a pancake arm, just find something REALLY steady to hold it with.


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## bemoore (Dec 23, 2008)

Getting accurate readings on an arm is not as easy as it sounds. Keep in mind that in order to get accurate readings, you will need something more than the garden variety Radio Shack DMM. You need something that will measure 0.1 ohms with at least some degree of accuracy.


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