Body mounting vibration isolators?

[metros]

As I'm starting to line up my body panels and make slight adjustments to bring them all together I'm thinking of what I could use as vibration dampers between the fiberglass body and the chassis. Has anybody else come up with anything? It seems like a thicker rubber washer washer would keep the body from vibrating as much.

[STiPWRD]

I used some vinyl film between the gas tank and frame and I might use the same stuff at the body mounts. This is the stuff they use as a vapor barrier for custom shower pans. It's very cheap and available at home depot. I also used it when mounting my AWIC pump and fuel filter as a cushion. You could easily cut some washers out of it too.

[longislandwrx]

http://www.amazon.com/Isolate-Sorbothane-Vibration-Damping-Sheet/dp/B006YJ9AOS/ref=sr_1_fkmr0_3?ie=UTF8&qid=1459248129&sr=8-3-fkmr0&keywords=80+durometer+urethane+sheets#customerRevi ews

Some sorbothane might do the trick, http://www.isolateit.com/

you can use a hole saw to make a load of little disks, or just buy washers.

http://www.isolateit.com/bushing-and-washer-vibration-isolating/sorbothane-vibration-isolating-bushing-0576170.html

[MiniVanMan]

Two things come to mind.

Nylon Spacers

Phenolic Spacers

I know we use both of these in our vibration limiting applications.

When you need to secure something tightly so it doesn't vibrate, we use phenolic blocks.

When you want a little give, we use nylon. Now, that Sorbothane that was mentioned looks to be a type of nylon.

Nylon degrades over time. If the item will vibrate consistently, then the nylon will deteriorate after time and you'll have an even looser connection point.

The same goes for rubber, which has an even shorter lifespan than nylon.

Phenolic blocks don't reduce vibration as much, unless the item is completely constrained in the phenolic block (requires machining). Most of our applications are machined to fit the purpose. It reduces vibration by increasing mass of the vibrating material.

However a phenolic spacer or washer can still absorb vibration, and has a much longer life span than nylon.

So, what's the answer? Probably a mix of the two.

You'll need to figure out where and what purpose each will work.

If you want to isolate a panel that won't vibrate that much, but when it does it's annoying. Nylon (Sorbothane).

Phenolic washer or spacer will work well for separating two materials so they vibrate independently of each other. However, the connection point will transfer vibration (energy) into the other material more than the nylon.

So, it's a pick between permanent and not as much vibration isolation, or semi permanent and good vibration isolation.

Your pick.

[billjr212]

Warning - I'm going to play devil's advocate and answer the question with a question :-)

question - why isolate at all and at what points do you plan to isolate?

The body needs to be rigidly mounted to the frame in a few spots as a result of space contraints/method of mounting. Specifically, at the door sills (fiberglass is sandwiched between aluminum sill plate and frame), the doors themselves are (more or less) rigidly mounted at the hinge, and the body is rigidly mounted at the door striker plate. Modern cars no longer have a body on frame design, so in a unibody context there is no vibration isolation except between suspension and unibody and between engine/transmission and unibody. The 818 retains these characteristics even if the body is rigidly mounted.

So, with that, why isolate a portion of the 818 body from the frame? Given that some points are rigidly mounted, wouldn't it be best to rigidly mount all points?

Again, I'll be honest and admit I'm playing a bit of devil's advocate here. I initially planned to use some sort of rubber/vinyl/etc isolation at the perches, but ultimately decided against it and haven't noticed any vibration noises in ~1,800 miles. Similarly, did around 10k miles in my Mk3 Roadster with rigidly mounted body and no issues there either.

I do agree that there needs to be vibration isolation in the form of weather-seals (or similar) between body panels that are not directly attached to each other to prevent wear (ie around the engine cover, trunk, and hood, and between the doors and body).

[RetroRacing]

Anodized metric bolt set (ebay) comes with lots of body mounting hardware in different colours and rubber washers (thin, anti abrasion)

[Loring]

These vibrations are of too low a frequency and too high amplitude to be using anything on the Shore D scale or higher. I'd go with a polyurethane.

[Bob_n_Cincy]

I used rubber washers with conical washer at all my body mounting points. Making the hole 5/16" or 3/8" for a 1/4" screw.
Two reasons:
1. Fiberglass and steel have different coefficients of expansion.
52162
I did not want the side sails bucking with the row of screws that hold it to the bottom of the car.

2. Hard joints will cause local cracking in the fiberglass.

my 2 sense.
Bob