# Pancake Chassis Comm Spring Size



## Grandcheapskate (Jan 5, 2006)

Hi Guys,

Does anyone know if Auto World changed the size of the comm brush spring (making it larger) when they switched to the XT Ultra-G chassis?

Thanks...Joe


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## dlw (Aug 17, 1999)

Pretty sure they're the same size. Is you XTUG's having trouble?


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## Grandcheapskate (Jan 5, 2006)

dlw said:


> Pretty sure they're the same size. Is you XTUG's having trouble?


No. I'm just experimenting with something and I wanted to find out if AW made the brush spring a little taller and stronger (heavier gauge wire) on an Ultra-G chassis as opposed to those used on original Aurora or Johnny Lightning. I was thinking the chassis itself might be a shade thicker, and therefore the brush holes slightly deeper, to accomodate the extra magnet.

Thanks...Joe


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## peter50 (Jul 24, 2012)

if that is XTUG's size then I believe that you can get trouble. I pretty sure on this because I also have faced to this problem.


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## Grandcheapskate (Jan 5, 2006)

For those who care, the answer appears to be yes.


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## tazman052186 (Oct 19, 2005)

The springs are the same as the one without the traction magnet. The 4 gear ones are a little different. I think they are bigger around or a little taller. Hope this helps.


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## Grandcheapskate (Jan 5, 2006)

In doing some research, I discovered that the comm brush springs used in newer AW XT Ultra-G chassis are taller than those used previously, and taller than those ever used in Aurora or JL cars. This taller brush spring is unuseable in older cars without snipping off part of the spring. If used in its unmodified form, it will at best cause additional friction, slow the car down and cause excessive heat buildup. At worst, the car won't run at all because it binds up.

Here is a note I received from a fellow hobbiests who did some testing and measuring:

Your note on the AW Ultra G brush springs got me thinking. So I dug up a dozen chassis from different releases and took them apart. Lo and behold, 2 different spring sizes. The older ones were smaller in height, more similar to the original AFX and JLs. But here's the irritating part, not all of the newer ones had the taller springs. It looks like the taller ones were added here and there as production went through. I noticed that none of the 4-Gear chassis had the taller springs. I just received the Rat Fink cars in the mail yesterday. After I take some pictures for my website, I'll take a couple apart and see if the springs are tall or short (normal). The taller springs do cause the same result in JL and AFX chassis. Just too much pressure.

Thanks...Joe


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## dlw (Aug 17, 1999)

I wonder if they are putting pick-up springs in the comm's as pickups are bigger than comm springs.


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## Grandcheapskate (Jan 5, 2006)

dlw said:


> I wonder if they are putting pick-up springs in the comm's as pickups are bigger than comm springs.


 I don't think so. While the comm springs are bigger than before, they are not quite the same size as the pickup springs.

Joe


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## slotking (May 27, 2008)

I have cut down pickup springs in the past for my afx comm
had real low ohm arms


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