Muffler Suspension

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Norton-Commando750-Roadster-1970.gif


One of the things that has bother me is how the mufflers/exhaust is mounted. You've got this engine assembly flopping around and the mufflers are mounted with a pair of rubbers which take all the strain.

What would happen if the mufflers were on more of a pivot, or, perhaps a link that allowed them to move up and down slightly but still suspended?

Or do I have too much time on my hands as I wait for parts to show up?
 

Flo

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Fancy ass on a computer eh?
Maybe an isolastic fixing on the silencer?
 
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The motor/trans/swingarm vibrations are not straight up and down, but more of an ellipse. Obviously the front mount moves the most followed by the top and them the rear is almost more or less a pivot. An ellipse is basically an elongated circle with two centers and a constant radii (two radiuses which always add up to the same number) All three mounts move in different ellipses and the rear exhaust mount has to do the same thing only smaller. Your computer simulation is a bit inncaurate and a true pivot would not work as the whole assembly has to be free to move in two dimensions.
 
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Since the mufflers are able, with the stock mounts, to move in 2 planes now, seems to me the only way to improve the suspension is to literally hang the rear of the mufflers with something like a (short) cable.

And, yes, you do have too much time on your hands. But, your putting it to good use thinking about Nortons.
 
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Danno said:
The motor/trans/swingarm vibrations are not straight up and down, but more of an ellipse. Obviously the front mount moves the most followed by the top and them the rear is almost more or less a pivot. An ellipse is basically an elongated circle with two centers and a constant radii (two radiuses which always add up to the same number) All three mounts move in different ellipses and the rear exhaust mount has to do the same thing only smaller. Your computer simulation is a bit inncaurate and a true pivot would not work as the whole assembly has to be free to move in two dimensions.

Eh, you're saying it doesn't move like that? :mrgreen:

I have to assume that the majority of the movement is up and down. Has anyone put a dial indicator on a running engine to see how much it really moves?

How would a cable suspension work?

(built it with Photoshop)
 
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Nice work Dave, I think you do have a little too much time waiting. LOL, When the stock hangers are in good shape and set up correctly they work great, I have to wonder about a pivot creating rattles or squeaks and not sure what you mean by a cable? I think as long as these bikes have been around someone has tried something new only to go back to stock setup, Maybe guys could show a better idea or two? Pictures? :wink:
 
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Hortons Norton said:
Nice work Dave, I think you do have a little too much time waiting. LOL, When the stock hangers are in good shape and set up correctly they work great, I have to wonder about a pivot creating rattles or squeaks and not sure what you mean by a cable? I think as long as these bikes have been around someone has tried something new only to go back to stock setup, Maybe guys could show a better idea or two? Pictures? :wink:

4138tp1s.gif


McMaster Carr has these gas struts (mostly used for hatches). The smallest is about 6-7" long. With rod ends they would have multiple degrees of movement. And dampen the vibration of the mufflers.

Just because no one has thought of something to do for the exhaust doesn't mean it can't be done. If it's not broken you aren't trying hard enough. :mrgreen:

btw, Production Racer muffler mounts are $100. So there's an opportunity to make something that costs more and is less effective...
 

acadian

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An interesting article I once read described the iso mounting designed for the exhaust system as being the "best worst solution". Basically, due to leverage and the fact that the iso mounts are far back from the engine, what's created is a scenario where the engine and the muffler vibrate at different frequencies. The article used this point to rationalize the issues we Commando owners have with our exhaust ports vibrating to shite.
 
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I guess I spend to much time thinking about Nortons too. I think the engine moves in an eliptical pattern. This happens because the balance factor is about 50%. The whole engine and transmission shakes in this way. I don't know what the amplide is of the shaking at the different mounts. There may be some rocking going on too. I am hoping the amplitude is about the same on the front and rear. Maybe it isn't. I think it would be best from the point of view of reducing the strain on the mufflers and header pipes if the pipes moved in perfect unison with the engine. This is the way Buells and Harley FXRs work. I have a Triumph with an isolastic system that I made and it works this way too. Right now I am building an 850 Norton and I have made a bracket that bolts on where the center stand would normally go. This bracket has extensions on both sides that the mufflers bolt onto. That way the muffer and whole exhaust system will be a unit. Has anyone else ever tried this.? Will it work? It seems an obvious idea. It was easy to make.

I will send some pictures of this bike in a few weeks. I plan on finishing it for the Nortorious Rally.

I know of some machines that have the Dunstall system where the pipe under the engine is clamped to the transmission cradle. This system works.

It is amazing that the original system works. I think there is a lot of dependence on the headers flexing.

Nigel
 
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tricatcent said:
I guess I spend to much time thinking about Nortons too. I think the engine moves in an eliptical pattern. This happens because the balance factor is about 50%. The whole engine and transmission shakes in this way. I don't know what the amplide is of the shaking at the different mounts. There may be some rocking going on too. I am hoping the amplitude is about the same on the front and rear. Maybe it isn't. I think it would be best from the point of view of reducing the strain on the mufflers and header pipes if the pipes moved in perfect unison with the engine. This is the way Buells and Harley FXRs work. I have a Triumph with an isolastic system that I made and it works this way too. Right now I am building an 850 Norton and I have made a bracket that bolts on where the center stand would normally go. This bracket has extensions on both sides that the mufflers bolt onto. That way the muffer and whole exhaust system will be a unit. Has anyone else ever tried this.? Will it work? It seems an obvious idea. It was easy to make.

I will send some pictures of this bike in a few weeks. I plan on finishing it for the Nortorious Rally.

I know of some machines that have the Dunstall system where the pipe under the engine is clamped to the transmission cradle. This system works.

It is amazing that the original system works. I think there is a lot of dependence on the headers flexing.

Nigel

Why do we have to wait a couple weeks for the pictures? We demand them now.

Ok, maybe a strong request.

How about a pretty please?
 
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Ludwig could you post some pictures on how they attach? I have never had a problem, but I bet they will crack soon now, LOL :cry:
 
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Thanks Ludwig, It looks as though you don't run a centerstand? (stupid question) I know they are heavy. But the idea of mounting it there is much better as others have also said, I wish I would have done this on the 72 as mine doesn't have a centerstand. Did you custom make the cradle? Thanks for your time posting the pictures, Chuck.
 
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Hortons Norton said:
Thanks Ludwig, It looks as though you don't run a swingarm? (stupid question) I know they are heavy. But the idea of mounting it there is much better as others have also said, I wish I would have done this on the 72 as mine doesn't have a swingarm. Did you custom make the cradle? Thanks for your time posting the pictures, Chuck.

Yeah, he has a custom made aluminum cradle, if I recall.
 

grandpaul

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tricatcent said:
... I think it would be best from the point of view of reducing the strain on the mufflers and header pipes if the pipes moved in perfect unison with the engine. .. I have a Triumph with an isolastic system that I made and it works this way too. Right now I am building an 850 Norton and I have made a bracket that bolts on where the center stand would normally go. This bracket has extensions on both sides that the mufflers bolt onto. That way the muffer and whole exhaust system will be a unit. Has anyone else ever tried this.? Will it work? It seems an obvious idea...

BINGO!
 

grandpaul

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Hortons Norton said:
Thanks Ludwig, It looks as though you don't run a swingarm? (stupid question) I know they are heavy. But the idea of mounting it there is much better as others have also said, I wish I would have done this on the 72 as mine doesn't have a swingarm...

I believe you meant "centerstand", and not "swingarm", correct?
 
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When I first got my MK-III home, the first day last fall. I was sitting on it in the driveway explaining to my wife why it was a good idea to buy a 35 year old bike. To demonstrate I went to kick start it, my heel slipped and hit the right hand pipe and knocked it right off the bike onto the ground....
 

grandpaul

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tban52 said:
When I first got my MK-III home, the first day last fall. I was sitting on it in the driveway explaining to my wife why it was a good idea to buy a 35 year old bike. To demonstrate I went to kick start it, my heel slipped and hit the right hand pipe and knocked it right off the bike onto the ground....

...Which highly impressed her, and totally solidified your argument, i'm sure!
 
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