Silencer for Series C Comet

[Henry Martini]

Hi Matty,
I have not used the very recent VOSC offering I did have 2 of the previous ones and found that they blued badly at the front, I don't know if this problem has now been addressed. I have not used the Armours one, but can tell you that the S/S one sold by Kemp
was not made by Armours. They may be the closest one can get to the Kemps one. As I understand it what is good on a Comet may not be good on a Twin and visa versa. Russ would perhaps consider ordering 10 if he were to receive confirmed prepaid orders
with a 6 month waiting time. I am prepared subject to price to order and prepay for 2. Any other's out there speak up and call Russ.

Henry Martini

 

[timetraveller]

My only experience of the Armours s/s silencers has been on twins, not Comets so I cannot comment on how they sound on singles. On twins, for road use, they are ok and I do not mind the straw colour. Note however, that I have previously commented on these pages about the poor fit of Armours exhaust pipes.

 

[Black Flash]

Hi Matty,
first of all thank you for thinking we are better of, but be assured we are not. Mrs Merkel is really trying hard to squeeze the last drop(penny) out of hard working people. If you work for the government or in the financial market it is a different story though.
I have had many different exhausts from Armours over the years, one system for a Matchless G80 and a high level one for a G3LCS kind of, swept backs and Minigoldies for a Triton and the goldie one for my special and they all fitted well.
Their quality was always ok as was the price. I just want you to double check that they do fit wadding to your absorption type s/s silencer before you order it. From what I understood when phoning them, none of their silencers has wadding as a standard ! they told me they will do for a a s/s one if ordered that way and it would take them about 3-4 weeks.

Bernd

 

[timetraveller]

My two Armours s/s silencers both have padding but they are years old so cannot vouch for the later ones.

 

[Matty]

Hi

When I rang Armours yesterday they said that their steel chromed silencers did not have any padding because they could not be chromed with padding in.

However because the s/s one was not chromed, it had damping padding, which made it a bit quieter - but I had the impression it was still quite noisy.

I am not too keen on the s/s one however due to the straw coloured patina. I'm trying to keep my Comet looking as much like it did when I bought it in 1956 for £150, which is less than VOCSC want for their silencer !!

Although I have heard tales of Armours systems not fitting, the exhaust pipe I bought four years ago and the later chromed steel silencer fitted really well - though (see above) I found the silencer too noisy on The Comet and sold it to a friend (who is still a friend) with a Rapide.

I am presently running on a very smart very noisy but old empty straight through silencer or a tatty quiet one with baffles which results in very flat performance.

Seems the Bankers and bureaucrats in Germany are much the same as the ones in UK - better off than most of us because they are in control.

Matty

 

[vibrac]

Its been said earlier in the thread you will never get effective silencing with a body diameter of the standard unit you need at least 4” diameter and not only is that ugly but it has to be mounted at a higher level.
But it sure works with no baffles and a straight through 2” pipe I get 100db from a absorbs ion silencer on the Comet and if I had an annular exit of same X section area I guess I would be down in the low 90’s
Not much comfort to a standard guy but worth considering on an Egli
Incidentally the ACU noise test is run at a certain rev range dependant on stroke I was a sound scrutineer at a meeting some years ago and a NSU Sportmax came to be tested boy it made a racket! But when we tested it just at the measuring speed it went some 10-15Db quieter and passed
He showed me the trick under the engine he has a cross pipe at right angles with a blind end he had set the bike up at the measuring revs and slid this cross tube like a trombone till it went quiet then brazed it up.
It’s called the Helmholtz effect (I think) perhaps that’s the answer set it to 4200 on a Comet and see……

 

[Chris Launders]

Hi all
Took the shadow out without the air filters,only difference was it was harder to start and had a flat spot just off tickover.Refitted filters and swapped standard silencer for the goldie off the norvin,BIG difference,slightly louder but still pulling well above 4000 rpm by which time i was running out of space,you could still pick out the exhaust pulses unlike the standard silencer.So the problem still remains-how to get a standard silencer thats not too loud but breaths ok.

 

[Peter Stokes]

This is not directly Vincent related, but is a bit more about Armours products. I got some stainless pipes and silencers from Armours a few years ago for my old 750 Ducati. The pipes fitted a treat, and are still on the bike. The silencers were astonishingly noisy, deafening. If there is any silencing material in them I would be very surprised. I kept them on for about a week and then couldn’t stand them any longer. They sit back in their box, and the old silencers are back on the bike.
This is where the behaviour of the old silencers is odd. There were two types of silencers for these bikes when they were new, the noisy Contis, which some folk like, and the quieter Lafranconis, which my bike has, and which I like. These are a labyrinth type where the exhaust gases take a longer path, backwards and forwards through pipes within pipes. I have a set of these on the bike, but they are getting on a bit, and have corroded inside. You should definitely not be able to see through these, but the end plates in the inner pipes have rusted and blown through, so now you can. They are now straight-through silencers and you would expect them to be very noisy, but they are not. They have remained like this for a few years without getting worse, but I’ll be stuffed for replacements when they rust through to the outside.
So – I think that the behaviour of silencers is some dark art, not to be understood by me.
Quote from Vibrac – ‘... he has a cross pipe at right angles with a blind end...’
That is very interesting – so, on the twin, does the pipe of the cylinder which is not firing present a dead-end branch of the exhaust pipe, so quietening the exhaust on the twin compared to the Comet? I appreciate that it is a complex system, a dynamic system where the next exhaust pulse has some effect on the last one, and vice versa. Complicated!
Pete

 

[vibrac]

Right then
big cork, twin pipe, fit to comet and lets see....;-)
(or rather hear)

 

[Matty]

Hi Peter

Befoire I retired I was at some time an Electronic/Electrical research Engineer and as part of my studies had to do lots of hard sums associated with waveguide design - the principles of which can also (if you are clever enough ) be applied to the resonances and matching characteristics of exhaust systems.

These days the designers of exhaust systems, I am sure, use all sorts of fancy fluid dynamics software to optimise their sytems as do the designers of waveguides for the transmission of electromagnetic energy. Extra bits of pipe are called stubs in the electronic world and their lengths can be calculated to produce all sorts of matching and transmitting resonanace effects - though silencers are pretty tricky to analyse mathematically because they have baffles etc. which ruin the purity of the maths and complicate the sums a great deal.

So I am sure that the extra bit of pipe will change the characteristics of the exhaust systems from singles to twins and that the cross pipe could act as a matching stub if it had the right dimensions.

I think however that exhaust pipe/silencer design is more of a black art than waveguides because the latter are of very accurate dimensions, therefore easier to analyse and hopefully the megawatts of electrical energy do not get out of the sides of the waveguide, whereas quite a lot of noise escapes through the casing of a silencer.

Sorry I don't think any of this will help much with our Comet problem, but may help to explain why twins are quieter than singles on some bikes and the cross pipe might effect the niose.

Matty