Alloy Muffler

[bashplate]

hi guys,

just wondering about the alloy mufflers a lot of pre65 bikes use....you know the elongated diamond type, has anyone any idea what the baffle arrangment (if any) is in these? i am guessing the inlet and outlet pipes stick well into the 'can' so that the gas has to double back to get to the outlet pipe.....are the pipes perforated any, or just plain. reccon charlie will know the answer as he's built most things to do with the old 4 strokes.

cheers trev.

[jon v8]

I've got one in a box somewhere.... Was going to use it on my Serow/TY project,but didnt need it.From memory its perforated and is not straight through like an expansion box.I'll try to find it and take a photo.

[bashplate]

thanks jon

[brian h]

I made a silencer the shape you describe for a Triumph TR20 Trials Cub which looks good and above all works perfectly.

You need 0.062 wall alloy tube to slide over a 1.25 dia exh pipe and need access to a good Tig welder and requirea tool to created the scoops needed.

The pipe that goes into the silencer has four staggered rows of scoops protruding into the gas flow, these scoops are equally spaced - four scoops in each row, offset on each alternate row and approx 1.0ins apart inside the silencer. the bottom pipe terminates open ended inside the silencer and causes the gases to swirl around into the top pipe to atmosphere.

The body of the silencer began as 4.0 ins dia tube X 0.062 ins wall, squeezed to approx 1.5 ins oval, then cut along the top and bottom, fitted to the tubes with end plates and Tig welded. You would need to make a tool to created the four rows of scoops. This design works well and good both for noise and performance - these silencers are hard to find these days.

Hope this helps

[charlie prescott]

Hi Guy's.

Hi Bashplate,

You are thinking of the Terry Weedy/ Miller. box , still available from Terry ,at Avery Products.

You have the entry and exit pipes that are perferated with a small return on the perforations, this helps to redirect the gasses.The box itself acts as a small expansion chamber, slightly like a reverse megaphone, and seems to help with the gas flow. Although these tend to protrude slightly when fitted I still thing they are good boxes, and at the right price.

Hope this helps. Sorry for not answering sooner, but have had problems logging into the new format site.

Regards Charlie.

[bashplate]

Hi Charlie,

yes I was thinking of the Miller type box, was wondering how they differed internaly to a straight through absorbtion type baffle....I'm much clearer now. One last thing, the 3 bikes pictured have the box close to the cylinder(short header pipe) as apossed to having it hanging out behind the shocker, does the placing of the box alter the engine charictaristics at all, or is it ok to put it anywhere convenient? Thanks to all for your imput, Cheers Trev.

Edited July 27, 2012 by bashplate

[charlie prescott]

Hi Guy's.

Hi Trev,

There is a theory that a longer pipe helps bottom end power, but you need a megaphone type extraction at the end to compleat the system.

To be quite honest, I think expansion type chambers help some motors but not others.

Trials riders tend to use short pipes and boxes just to took them out of the way more easaly??? some realy short, double tube, boxes do no good at all, only to anoy the other competitors.

That is why I think the Weedy type, although slaged by others?? actualy has been proven over the many years now in production to do the job. Well.

Regards Charlie.

[bashplate]

Thanks guys,

going to have a go at knocking a box up when I get a minute. Always like to get a mental picture of where I'm going with a project before I start... . A drop of elixier also helps . cheers. trev