# Pancake arm questions......



## TX Street Racer (May 8, 2004)

Hey guys, I'm in need of a bit of help with pancake armatures. Does anyone know how to check the ohms of a pancake armature??

What's the fundamental basics for finding the best arms?

Also, in the world of Aurora arms......which would perform better in a Tjet....Mean Green or Blue drag??? I know the blue drag arms are supposedly designed with more torque.


THANKS!!!!! :thumbsup: 

Brian


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## 2.8powerranger (Dec 13, 2004)

take the wire of your meter and touch one contact then put the other wire on the next contact,wrrite down your reading,then move them both around to the next then the next,your basically walking the wires around the arm .
say going conter clockwise pos is in front neg behind next you will just move pos forward to the next copper pad and the neg will go where the pos was untill yo get all the way around,should get 3 readings,you want the arm with the closest readings across all poles,you'll want the arm with the lowest matching numbers .as for the green or blu arm,,depends on what kind of track your on ,,,twisty with short straights with a heavier car go blue,long straights and some curves lighter body go mean green,,one more upgrade though get some yellow and blue super 2 manets or j/l magnets,gearing is also a factor,but others could probably tell you better than me.alot of these guys here have a wealth of knowledge and some good suggestions. hope this helps :thumbsup:


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## gear buster (Dec 1, 2005)

*Arms..*

TX,

Pancake arms, Just add Butter,syrup and run..  

Checkin arms in the easiest part. As 2.8 said test from 1 pole to the other.This will give you the reading on the wire from on com to the other.
The lower ohms(For fray rule cars it has to be close 16.0 and no lower.)
Try to get an arm that all 3 poles on the com plate match when ohmed.Check to see if the com plate is not wobbly on the arm. This can be done with a low speed dremel or a jig you can make for balancing.There is a post on balancing arms and jig making here somewhere. For speed a good stock arm is as good as a blue or green arm.To much torque and will be unstable or hard to control in corners. 
Magnets we use is the JL/AW blue and white mags. Some arms will work better with even stock mags. You can over magnet a arm. It will actually slow it down in Rpms. Brushes We use a good copper brush. Mess around with the tension on the brush, you will find out it make a world of difference in the speed and power. Gearing is good .Just polish the gears for a smoother mesh ..Hint...(The quieter the car the faster it will run.. :thumbsup: 
Another trick..For better power before installing pickup springs, Place a small brass thin shime in the chassis,between the spring and chassis. This will give it more tension,(better than trying to stretch spring). Limit the shoe travel also. The flatter you can get the shoes on the rail the better power and handle. . Ind. brass fronts(we use wizzards and JW,s) but there is alot more good ones out there..Silicon rears(slip on or foamies) all good. Hope this helps some on building a driveable pancake...Need more help..Drop me a line .. There is alot more guys who know more secrets to arms,But I get by with what I have learned so why not pass it on.. Anybody else can add some more tricks to help out a fellow pancaker jump in.. 

I just might have a arm just laying around if you want torque...


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## Bill Hall (Jan 6, 2007)

*Weeding Them Out*

I'll kick in four cents here. For a cobbler such as myself there are two balances. Electrical and mechanical.

When you do the ohms probe I always check the comm plate and the solder joint on the ear. A bad joint can make it appear that you've got a bad loop.
While your probing pay attention to the general relationship of the arm shaft and the comm plate, RE is it centered, and does it look flat from the side? How's the solder globs look? They can cause havoc if they're lumpy or hooked by rubbing the pan or magnets. 

I always mount the arm and pinion to a good gearplate and chassis to spin them up till they're at operating temp. Checking ohms on an armature that's not warmed up doesn't give you an indication of heat fade. It also gives you a quick indication of how the brushes are tracking on the comm. The circular brush pattern (tattoo) also gives you a bulls eye to eyeball how well the comm plate is centered. It also negates the drive train noise so you can hear and feel whats going on.

Another reason to spin one up is mechanical balance. A free spinning arm with decent balance will have a distinct feel in your hand and an unbalanced arm will let you know. It's a different vibe. Be sure and spin em' up in the normal operating position, vertical. Check how they feel through the RPM range. You don't have to get all crazy here and cook the arm at WOT. Warm it up and give it a few blips to see how it feels at slow, medium, and fast.

As Gear Buster said comm tension is a big deal. When testing I "gently" poke (so you don't tweak the spring) the front an rear spring separately with my finger and listen for the change. Buster also is spot on about magnets. Stronger mags are not always the answer! If the arm doesn't have enough grunt, stronger mags are detrimental, as is a stronger arm with weak mags. When your testing it's a simple matter to change mags. Ultimately the final disposition on mags and spring tension is determined on the test drive. Is it twitchy cuz the mags-n-arm don't match, or are the brushes too tight. Providing your gear ratio and meshes are correct of course.

This is just my bone head way of creating three piles,

#1 - It'll live
#2- Needs work
#3- See ya later

As for the Mean green vs Blue Drag question, I prefer the blue drag over the gold wire green tip. I've never been happy with the heat created by the newer gold green arms, the old ones are OK. I also really like the green/greens however a high percentage of these seem to have their comms off center, and there seems to be some spread RPM wise right out of the package. Tire profiles, wheel and tire weight, initial and final gearing play a huge part in how an arm performs. I tend to be somewhat color blind on arms. A good arm is a good arm and has an application some where in the works. I'll take a good smooth, cool running stock arm over a wobbly, twitchy, finger burnin' supposed hot dog arm. 

Build yourself a poising tool and get one of those gizmos for polishing your comms so you can revisit the "Needs work pile". A lot of arms just need a little fluffin'. Good luck! :thumbsup:


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## TX Street Racer (May 8, 2004)

Hey guys, THANKS so much for all of the info.........DEFINATELY going to help me out in the future!!!

I'm REALLY wanting to get into some rewound arms.....and just build up a few pocket rockets for sh*ts and grins...... 

I'll pick up an electrical tester soon and get to testing my stock :thumbsup:


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## 2.8powerranger (Dec 13, 2004)

Thanks from me too! learnin more all the time,has anyone noticed on the green gold arms a real lag in the acceleration,i have one that requires alot of throttle to get going but tops out really high,just doesnt have the oomph off the line ,it goes either fast or a little more than half speed ,any ideas ?the poles are all at 5.9 5.8 5.8,.
matt


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## Bill Hall (Jan 6, 2007)

Yeah Matt as I stated above they dont get it for me. Some swear by them. I've short geared them, lightened the comm pressure and tried different magnets and always changed them out in disgust. There are some old school AFX gold/greens that you find occasionally that run nice and dont seem to have the lag or blistering heat. I had 4 of the new gen gold/greens and went 0 fer 4. That doesnt cut it for my money.


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