I rekon this is where the noise comes from

[crafty]

After banging my noggin against the rollbar a couple of times, and hitting aluminium panels and tools against various parts of the chassis as I manouver around my tiny garage, I found that any contact with the chassis makes quite a loud sound that resonates thru the chassis.

I figure that a lot of the road noise, engine noise and probably some of the heat transfer could be absorbed if the chassis tubes were filled with foam - like the stuff that you use to seal off cavities and/or around pipes in a house... I rekon this will probably reduce more noise than adding insulation to the panels, as the tubes not only resonate, they provide a direct flanking path for noise and heat from the outside to the inside of the car.

Im thinking if a hole was drilled in the end of each pipe (somewhere unobtrusive), then attach a long plastic hose to the nozzle so you can get the end of the hose near the end of the pipe, then draw the hose out as you pull the trigger.

5mm bead = 25mm fill > one 500ml can = 80m
10mm bead = 50mm fill > one 500ml can = 20m

If the rivet holes are already drilled they will act as overflows and from this you will be able to see that the speed you are pulling the hose out it adequate. Put duct tape over pipes before drilling so that the overflow will land on the duct tape for easy removal - cover everything else in cling film cos its gonna go everywhere.

Waxol needs to go in first.

When its cured - cut off all the excess, tap the hole and shove a stainless bolt, grub screw or somesuch in there...

Mmmmm - I like the sound of that.. (excuse the pun) - Im gonna grab a can and try it on a test piece of tube and see how it goes.


www.ramset.com.au/CC-PDF/FomoFill.pdf

[ezakimak]

Crafty,

That fomafil stuff works great at reducing sound, I no through work, that a lot of the audible warning devices that we install to protect the public, get routinely filled up with this stuff buy “vandals” as a way of making them quieter.

ryan

[crafty]

works on nagging women too

[donkeasy]

Think you can leave the waxoil out.

[martinlaw]

Would not put wax oil in first - it will prevent the foam from adhering to the tubes and it may affect the curing of the foam.

It is actually a good idea to spray a fine mist of water into the tube first as this helps with the expansion and curing of the foam.

Cheers,
Martin.

[brdee]

Isn't that similar stuff to the foam filler you can get from B&Q and other DIY places?

[crafty]

Nearly done cutting and drilling panels.

Im gonna go with this foam idea. Ive looked at the frame and there's enough places to get holes to enable filling of all tubes.... I'll take some shots over the weekend.

Point taken with the waxol.

[donkeasy]

Heard it is a good solution for vibration and noise from somebody before.

I am planning not to use alluminium
but to weld in metal (0,8mm) plates,
and put foam in the pipes
and all open areas/boxes.

[crafty]

All good to go. Got some foam and some silicone hose. I think I'll need to strap the hose to a piece of wire in order to be able to push it down the chassis rails.

I think I am going to put the holes in the middle of the car, this way the pressure in the can need only push the foam a max of about 1.5m down the hose for the longest members.

Im also going to pre-fit all of the hoses into place before I start, then all I need to do is connect to the end of each one and pull it out.

I was contemplating drilling a few holes in the inside skin of the roof panel and filling that also, but I'm a bit worried that the pressure may deform the outside skin.

Bought some Dynamat Extremeliner for the back of all the panels.

Its gonna be the quietest loud car in Hong Kong.

[donkeasy]

1.
Buy some plastic pipes, house electrical stuff.
dril a hole (or two) in that and experiment a bit.

2.
Dril a few holes extra
so the presure will go off
and you have no expanding problem.

3.
buy some thin handcovers/gloves.
doctor/operation/don't know english word
It works a lot better/easier.

[crafty]

I tried one chassis tube today.... the one on the bulkhead.

I did it before fixing the panel - this is what I found:

1. I pulled the hose out far too slow and put too much in.
2. Because there's no air in there it takes a long time to dry.
3. If you pull it out too slow, and put too much in, it keeps spewing out of the holes for ages.

I've gone ahead and fitted the panels first, its too messy with the holes open. I am also going to use a heat gun to warm up the chassis before I start.

The test tube I did is noticably quieter than the unfilled tubes and this is definitely worth doing.

[crafty]

Oh yeah - my final shipment arrived today:
transaxle
wheels - Kinesis
harnesses - simpson
gauges - autometer procomp ultra lite silver faced
and a load of braided hoses and connectors.

I've had to cover the wheels up cos I kept finding myself in a daze, staring at them and touching myself inappropriately.....

[donkeasy]

1. I pulled the hose out far too slow and put too much in.

a. Tried it with the plastic electrical pipe and two open ends.
Have to put a bit in (1 sec) every +/-15 cm and it al comes together.

2. Because there's no air in there it takes a long time to dry.

a. Normaly it takes 24 hrs in a buildingsite, so that is normal.

3. If you pull it out too slow, and put too much in,
it keeps spewing out of the holes for ages.

a. Hope you can still open the door of your garage this morning.....

[craig-ultima]

I am curious to see if this foam idea makes a difference.

My understanding of acoustics is that sound absorption requires dissipating or reflecting the energy of the sound vibration. Filling the chassis tubes with foam would imply that the goal is to absorb the energy being transmitted through the steel tubes and convert it to heat in the foam inside. I don't think it is going to work. A good test would be to take two segments of identical steel tube - fill one with foam, and leave the other empty. Tap a hammer on the end of both (transverse and axial) and see if they have different sound characteristics. My bet is that any difference would be very minor.

Regular cars reduce sound into the cabin by having much less noisy engines, spongy suspension with alot of rubber isolation pieces, monocoque bodies that flex quite a bit, etc. I don't think its reasonable to expect a quiet Ultima - however, I'd love to be proven wrong!

[crafty]

We do a bit of acoustic work for buildings....I'm not an expert but we've done a bit of testing etc and built a few theaters...

To effectively stop sound transmission from say one room to another, you need a combination of thicknesses and densities. The different thicknesses and densities trap different frequencies of sound. You also need an airgap. Thats why Dyanamat works so well for sound through panels.

For the chassis its a little different... when you hit the tube (e.g. engine vibration) the sound is make BY the chassis resonating... much like a tuning fork. If you think about it in the GTR you have a large tuning fork (Rollcage) over your head, and attached to that you have a 6500rpm vibration generator.


I am nearly done with filling the chassis with foam, and the parts that are full make a "thud" rather than a "twang" when you hit them. There is definitely an improvement.

[martinlaw]

Crafty,

It is probably too late now but is the cured foam fire resistent?

What will happen if you ever need to do any welding?

[crafty]

[quote=martinlaw]Crafty,

It is probably too late now but is the cured foam fire resistent?[quote]

yep

[jeff-texas]

martinlaw said:

Crafty, It is probably too late now but is the cured foam fire resistent? What will happen if you ever need to do any welding?

If you need to weld the chassis for repairs to the "tub" around the cockpit (where the sound/insulation issue occurs), the damage has gotten to the safety-cell for the passengers, so isn't it pretty likely that the car is totaled anyway? ;-) (other than perhaps the footbox's / front-bulkhead's chassis-tubes)

But for anything besides welding, this stuff was meant for usage on homes, not inside sealed STEEL PIPES of a chassis. As the temperatures from a fire turn this insulation from a solid to a gas -- the gaseous form of it being much lower density than the solid form of it -- if temperatures can vaporize the insulation w/o melting the metal first, what if it turns each tube into a pressurized-gas pipe bomb? This might or might not happen during a fire, but I wouldn't risk it just for a little insulation effect!

>> Edited by jeff-texas on Thursday 9th March 11:24

[donkeasy]

Think you get carried away a bit there jeff,
At these temperatures you can not survive in or around the car.

But point taken.
I will use the (3M) foam from a coach/busbuilder around the corner here.
They use it for empty spaces/noise isolation, and it's more fire-resistant.
It has to be used in a special presurepistol,
and comes out very slow, which is better.

[jeff-texas]

donkeasy said:

Think you get carried away a bit there jeff, At these temperatures you can not survive in or around the car. But point taken.

My fire-retardant Touch-n-Foam from Walmart says it's flammable at 240F -- and I think 3-layer nomex is ok at quite a bit more than 240F. ;-) (That's not even boiling.) Not only that, but a fire stopped by your firewall can keep you relatively cool (even if you aren't wearing nomex at the time) compared to the steel pipes adjacent to the cockpit, since heat is easily conducted by the steel pipes but your firewall blocks most of that heat from the larger surface-area facing your cockpit. i.e. Your chassis pipes need to penetrate your firewall at some point and these penetrations thru your firewall will conduct heat.

To determine whether I'm getting carried away, we'd need to know how long it takes for enough of the foam to turn gaseous that it exceeds the steel's burst-pressure at a few different temperatures, compared to how long it takes your nomex to fail at each of those temperatures...and I doubt you've calculated that. I'm not trying to be an alarmist, and like I said in my first post, it's hard to say whether the foam would make your steel pipes burst at all...but I just wouldn't wanna find out the hard way. ;-) There is that risk of shrapnel -- to you and anyone responding to your fire -- when you place solids in any strong, steel pipes w/o calculating anything.