Baffles

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
Trefor
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Baffles

Post by Trefor »

The silencer on my G80 appears to be a replica and 'straight through'. I think it may be the cause of slight hesitation at very small throttle openings. Can anyone describe or better still point me to an illustration of the type of baffles that should be inside? Thanks.
JimFitz
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Re: Baffles

Post by JimFitz »

My replacement silencer was the same. The original pipe would have had about 12-14" which fitted inside the silencer and had a lot of holes drilled in the side and a blanked off end and was known as a "pepper pot" pipe for obvious reasons. The pipes available now do not seem to have this and are straight through.
I have a modern pipe and silencer on my 52 G80 and the exhaust note is louder than before but I did not have to change any carb jets.
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1952 G80 rigid, 1960 G12 DL / Watsonian Monza, 1954 G80S.
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Rob Harknett
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Re: Baffles

Post by Rob Harknett »

If you look in the parts list you will see the exhaust pipe blocked the end and many holes drilled around the pipe. This is the baffle which goes deep inside the straight through silencer. Replicas are usually found with a shorter pipe without the baffle, which is in the silencer. So you need a matching set.
Trefor
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Re: Baffles

Post by Trefor »

Thanks for the information, I have the exhaust section with the holes drilled in the side, but the pipe is not blocked, so I can start some experiments. Cheers, Trevor
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Rob Harknett
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Re: Baffles

Post by Rob Harknett »

Not blocked at the end may be correct, long time since I had a pipe off. The original pipe that had the holes in it to act as a baffle was much longer than replicas. Some one will usually spot if I made an error or memory failure, so I've looked at parts lists
Ashampoo_Snap_2018.07.01_11h36m01s_001_.png
The pipe appears to have open end in the 1955 parts list, cannot see the end in 1960 list.
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Mick D
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Re: Baffles

Post by Mick D »

Hi

The 60 parts list seems to indicate the end is open:
Ex Baffle.png
I think I'd like to try making a baffle for my bike which is a little more noisy than I remember - does anyone have an original pipe that they would be prepared to measure and photograph?

Regards Mick
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Pharisee
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Re: Baffles

Post by Pharisee »

If the pipe is open at the end, I'm not quite sure what would be achieved by drilling a lot of holes in it.
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SPRIDDLER
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Re: Baffles

Post by SPRIDDLER »

Pharisee wrote:If the pipe is open at the end, I'm not quite sure what would be achieved by drilling a lot of holes in it.
Good point! Maybe it's to tune the note to bFlat or a factory TT mod to reduce weight ;)
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Mick D
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Re: Baffles

Post by Mick D »

Pharisee wrote:If the pipe is open at the end, I'm not quite sure what would be achieved by drilling a lot of holes in it.
Hi

The exhaust travels along the pipe as a series of pressure waves, as the waves pass each annular set of holes a little of the pressure is dissipated to the silencer, the progressive dissipation reduces the exhaust noise level because it doesn't come as a single short pulse for each exhaust stroke which it does from a non baffled pipe, but as a more lengthy pulse - the energy is the same but as it's delivered over an increased time it's quieter.

Or at least that's my understanding of how it works.

Regards Mick
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Rob Harknett
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Re: Baffles

Post by Rob Harknett »

That's how it does work. They even use various types of baffles with a Trumpet to achieve a different sound.
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