Silencers/mufflers: packing

[Alley Kat]

Has anyone here chopped/modded exhaust cans? The fibreglass-packed type.

After an on-the-spot decision to shorten & mod the back end of my Wing, I've gutted and shortened the exhausts. Replacing the chamber'd baffling with straight-through perforated tube internals, which needs 'glass packing.

But I'm wondering how tightly packed the 'glass wants to be. Kind of difficult to quantify I know but, loose or tight, or really crammed in ??

Hoping someone's gutted or modded a glasspack and can give me a vague idea....

[BIG T]

when i shortened the "cherry bomb" brand glass pack i have on my 78 wing, i noticed that the glass was packed a little looser than a medium pack. (tight being rock hard and loose being like as it comes in the bag it was purchased in)....it growls but is not obnoxious. i would try a little like the insulation batts they sell for attic insulation...(do they sell it that way in the UK?)
or about as loose as a bag of cotton balls....hope this helps....T

[Alley Kat]

T yes, thanks, gives me something to shoot for. Knew it'd be really hard to describe : ) but I've got an idea, thanx.

[Jester]

I only have my quad to thank for this reply.LOL I repacked a White Brothers pipe using the "home" insulation and it didn't work too well. I finally broke down and bought the stuff for a four stroke at the bike shop. There is a differance between 2 and 4 stroke packing. I just wrapped it as tight as I could around the perferated interior tube and it worked great. Put some tie wire (bailing wire) around the wrap when your done. Both ends and one or two in the middle. This will hold it in place so you can slide the Perferated tube wrapped with batting back into the pipe. You will know when it's time to repack. That wire will start to sing to you. I have also heard of guys using zip~ties to hold it in place. It will melt off but who cares. It's only job is to make life easier during reassembly.
Good luck.

Jester

[Alley Kat]

Thanks Jester. I've made a perforated tube and a round 'disc' that the tube goes through, the disc seals to the walls of the outer exhaust. Then there's the end cap, so I've got like a 'chamber' where I can shove wadding in without having to tie it. Got the proper 'glass packing already, unused from another lil' project.

Dunno if it'll work, the chamber is short so I think they'll be loud, plus they're straight-through instead of the standard convoluted resonator design (whatever its called). On the plus side, there'll be almost no backpressure now it's only made with stuff lying around, so no cost if it fails (well unless the cops haul me over!!).

[NiteMare]

uk ebay has can "packing" for about 5quid per cans worth ....

seen a few auctions on "buy it now" at that price ....

ready built up to be slipped in micron style sports cans....

or try your local breakers for a crushed can and strip the packing out of it

[Alley Kat]

Thanks mate, I've got some wadding, but I am looking for something higher density to put a layer of that in. Like a lining round the inside of the cans, for a bit of extra deadening. Off to see if there anything worth robbing out of the loft : )