# Aurora AFX Bodies and Noise



## Grandcheapskate (Jan 5, 2006)

Okay, what is it about certain Aurora AFX bodies that make the chassis sound like it is grinding away?

I have been taking some Aurora AFX chassis (both styles) and cleaning them up. I run them around the track and they are nice and smooth, no noise. Then I put the body on and it sounds like every moving part needs oil. Take the body off, and no noise.

Not all bodies, just some. All the McLaren XLR #54 or the Ferrari 512 bodies for example. I'm assuming that one of the gears is hitting the underside of the body, but I see no marks of any kind. Go fairly slow and there's no noise. Go fast and they grind away. These bodies are very tight on the chassis, but I don't think they distort the chassis - or do they?

What is it about these bodies?

Thanks...Joe


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## brownie374 (Nov 21, 2007)

Echo, try a body with a open cockpit


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## AfxToo (Aug 29, 2003)

Something must be rubbing. You could try marking the inside of the body with a silver Sharpie in areas where there are moving parts nearby, running the car around for a while and then looking for the silver marker being worn off. Another approach would be to mark the top of the gears, black Sharpie on the brass gears and silver Sharpie on the black gears and then running the car and look for wear. Sometimes there are body protrusions that rub directly on the gear teeth, especially on bodies that have an open cockpit (low body height) or a tight rear bulkhead like the two cars you mentioned. 

Another experiment would be to put a layer or two of electrical tape on the top side of the chassis pot handles before mounting the body. If there's any vertical slop this may tighten it up or jack up the body ever so slightly to get if off the gears. If this changes the sound then there is definitely something rubbing.

I've had the same problem with the XLR McLaren and it was due to the body getting loose over the years and dropping on to the gears. I ended up glueing a small shim of Plastruct into the body above the side mounts. Some of these bodies also have standoffs in the body that rest on the side rails of the gearplate to keep the body off the gears. If one of these wears down or is broken the body will drop enough to rub on the gears. 

Most of the original A/FX bodies used standoffs and only have the bottom half of the body side mounts. This allows the body to sit nice and low on the A/FX chassis. The downside is these bodies don't fit on any other chassis, like a Tomy SG+ or Turbo. When AutoWorld copied these same body designs they did the full side mounts on the body. In some cases like the AW rendition of the XLR McLaren the results were utterly horrible, while others like the Trans Am Camaro the result is still wonky but tolerable. But they will take other chassis.


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## Grandcheapskate (Jan 5, 2006)

Thanks. I figured on marking the gears to see if anything was rubbing.

These two particular bodies are not wobbling at all, so both the side tabs and standoffs apparently haven't worn at all. In fact, they are really, really tight, which is what made me wonder whether or not they can distort the chassis just enough to cause something to grind. The Ferrari is so tight it really hurts using your fingers to pop it off.

In the case of the McLaren and Ferrari, you also have a front post on the body. Don't know if that causes extra tension (pushes back) on the front of the gear plate.

Thanks...Joe


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## tjetsgrig (Nov 1, 2009)

Some bodies are actualy "squeezing" the chassis together tweaking it. I know exactly what you're talking about. I'll take the body, apply a liitle heat and with my thumbs pull the body apart a little, then retry. Repeat as needed.


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## Boosted-Z71 (Nov 26, 2007)

I do the same thing, runners I dont care too much about as long as they dont make a ton of noise, I tolerate it. On my hardbody racers I stretch them until they are loose with a little wiggle & almost no pressure on the chassis. 

Jim's exactly right if they are tight, the body will flex the chassis and you can bind the arm, gear mesh & drive line.

Just a word of caution on any "blue plastic" AFX/Aurora body, they are extremely brittle and will sometimes explode into pieces in your hands, Datsun 510's have a similar problem as well, you think you have it almost right where you want it and next thing you know its in pieces. 

Boosted


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## Grandcheapskate (Jan 5, 2006)

tjetsgrig said:


> Some bodies are actualy "squeezing" the chassis together tweaking it. I know exactly what you're talking about. I'll take the body, apply a liitle heat and with my thumbs pull the body apart a little, then retry. Repeat as needed.


 How do you apply heat? Hot water? Hair dryer? How much heat? And the body will actually loosen up and stay loose after it cools down?

Thanks...Joe


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## Bill Hall (Jan 6, 2007)

*Kazoos!*

Sometimes there's more than one problem.

The bodies shrink so your squeezing them side to side at the motor housing.

Bodies shrink in all directions. They also shrink at different rates depending on the density of the area in question. You cant assume that all the mounting points shrink uniformly. 

So, not only can you be squeezing it east to west; you can also be exerting unexpected forces on the chassis at the stand offs. Sorta like pinching a deck of cards in the middle with one hand and bending the same deck in the middle endo style with the other hand. The transmission of unusual harmonics is a given at that point so you have find out where to relieve the tension.

It is not uncommon that a body that has been unmounted for a prelonged period of time can shrink/distort well out of whack with respect to the originally intended mounting points of a chassis.

A gentle but snug fit on the basket handles and the slightest clearance on the standoffs is what I shoot for. Excessive tension on either side mounts or stand offs simply enable the body to become a better resonator.


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## tjd241 (Jan 25, 2004)

I think it might be 2 fold Joe... _(okay I said... I think)_ .... I have certain bodies that are very snug on their chassis because that's their nature. They are low slung with no room to spare, ride nearly on and immediately next to the chassis, are thicker in some spots, and mostly windowless. Although the mechanicals are not being interfered with, any noise the chassis makes gets amplified by the shape and close proximity of the body. Like cupping your hand next to you ear can amplify sound, certain bodies almost do the same thing. For yours the problem might now be exaggerated by the addition of the extremely tight snap-in fit. Now you not only have a mini speaker cabinet reflecting sound... you also have the speaker making more sound too. You may never eliminate it completely, but if you file the mounting tabs with a good file (proceed slowly, equally per side, and methodically cuz you can't file it back on) you can probably at least lessen it by creating a less tight fit. I had one of the new Racemasters Chaparral 2D's at one point... damn that body was hard to get on and off.. Scary hard, and I almost wondered if I could get it off at all. The sound off of that thing was terrible. Same chassis slid into a vintage AFX Plymouth Roadrunner and it was quiet as a mouse. I actually traded the Chappy away without filing it, but had I kept it I would have had to have introduced the mounting tabs to Mr. File.


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## tjetsgrig (Nov 1, 2009)

Grandcheapskate said:


> How do you apply heat? Hot water? Hair dryer? How much heat? And the body will actually loosen up and stay loose after it cools down?
> 
> Thanks...Joe


All good methods Joe! And yes, they will stay loose after the cooling period!

JS


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## Grandcheapskate (Jan 5, 2006)

tjd241 said:


> You may never eliminate it completely, but if you file the mounting tabs with a good file (proceed slowly, equally per side, and methodically cuz you can't file it back on) you can probably at least lessen it by creating a less tight fit.


 Since I have a few more used AFX chassis than AFX bodies, would filing down the tabs on the chassis be a solution rather than filing the body? That is assuming the "heat treatment" doesn't work.

Thanks...Joe


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## NTxSlotCars (May 27, 2008)

It's nothing a dremel and a pair of Tyco mounts cant fix.


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## tasman (Feb 17, 2007)

*Echo, I agree*



brownie374 said:


> Echo, try a body with a open cockpit


The bodies with open cockpit or open side windows seem to be much quieter than bodies that are completely enclosed. I also agree that some bodies seem to cause noise because of tight fit, but don't overlook the echo effect mentioned by brownie374.


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