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Add-on silencers…any good?


David Davis
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"...Does anyone remember mice? those add on exhausts that made your engine super quiet. They were in vogue for a short time when i was a kid. If i remember rightly, they worked brilliantly. The problem was, they worked by robbing your engine of all its power so were of questionable value!..."

 

Oh I don't know...https://www.youtube.com/watch?v=_6h2g48yUWc

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2 hours ago, David Davis said:

"...Does anyone remember mice? those add on exhausts that made your engine super quiet. They were in vogue for a short time when i was a kid. If i remember rightly, they worked brilliantly. The problem was, they worked by robbing your engine of all its power so were of questionable value!..."

 

Oh I don't know...https://www.youtube.com/watch?v=_6h2g48yUWc

 

Interesting stuff. In fairness, i was about 10 when this was all going on but all i can remember was people complaining that once fitted their engines lost all their power, overheated and then the thing fell off and was never seen again! 

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3 hours ago, Jon - Laser Engines said:

 

Interesting stuff. In fairness, i was about 10 when this was all going on but all i can remember was people complaining that once fitted their engines lost all their power, overheated and then the thing fell off and was never seen again! 

I never had a problem with mine, in fact I've still got one but I don't run two strokes that much now. I remember having some quiet ends fitted to standard silencers by Martin Forrest who was involved in the development of the Irvine Q 40.

 

It could be that people felt that their engines were less powerful because they were quieter.

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12 hours ago, David Davis said:

It could be that people felt that their engines were less powerful because they were quieter

 

Old mk1 irvine 46 does about 1k rpm less, with a mouse on the end of the standard silencer, vs silencer by itself. That's the single chamber I.e. loud silencer. I don't know why it was so restrictive.

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2 hours ago, Nigel R said:

 

Old mk1 irvine 46 does about 1k rpm less, with a mouse on the end of the standard silencer, vs silencer by itself. That's the single chamber I.e. loud silencer. I don't know why it was so restrictive.

 

That's not what Mark Robinson discovered when he fitted a mouse to the standard Irvine 46 silencer here. https://www.youtube.com/watch?v=_6h2g48yUWc

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6 hours ago, David Davis 2 said:

 

That's not what Mark Robinson discovered when he fitted a mouse to the standard Irvine 46 silencer here. https://www.youtube.com/watch?v=_6h2g48yUWc

I have no doubt there was a change made by Mark Robinson's addition, but to measure a fair db reading, do it with the motor on the model on open ground.

To me, he completely invalidated the test using the bench and near to the stone wall.

 

The mouse did work well on my OS25 way back when, on the then Precedent Bi-Fly.

Edited by Denis Watkins
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Not high tech, but in the past I’ve taken exhaust from the motors silencer to an external big box, metal or epoxy home made on a flexible pipe. Project boxes are also good. Box had stainless washing up scourers, or even Brillo pads inside, very loosely inserted, which act as baffles.

Good silencing. Pain to make, and and plan the installation.

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I fiddled with a few on rc Buggys, so that I could drive around the estate in the 70's, so much lost power, also the blue aluminium restrictors on 20cc petrol, my P 47 'boat' ones work well as did this hair spray canister on my 20cc four strokes installed in a Helicopter.

 

 I have a Dle canister on my other 20cc Ra and that's another story the  engine goes ballistic, I put a rev counter inside the fuselage with a camera to see what rpm it really gives and it' unbelievable, I did post a vidéo on youboob.

dle 20 P 47 exhaust-2048.jpg

Silencer.jpg

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3 hours ago, Mike T said:

How does this fit to the engine?  The picture on the Weston website isn't very instructive!

image.thumb.jpeg.dcb66df23e0e06c5c6873482ed034713.jpeg
 

There is a 45ish degree header. Looks a bit like it might not be man enough unsupported but the silencer is super light and the engine so so smooth it hasn’t been any problem.  In my case the pressure nipple has been blocked off as the  engine us pumped.

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Nick, that looks like a tail dragger.

What bit hits the ground if it has a nose down incident. If it’s the silencer, look at the cost of new cylinder heads. The failure point will be the female thread in the head, where the steel of the header meets the aluminum head. If so a sharper bend on the header, and a skid/fusalage bulge might be good. 

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12 hours ago, David Davis 2 said:

 

That's not what Mark Robinson discovered when he fitted a mouse to the standard Irvine 46 silencer here. https://www.youtube.com/watch?v=_6h2g48yUWc

That's nice, but, his silencer is different to my single chamber one and dies not appear to be the standard irvine cast silencer. Without the mouse he's getting high 10k rpm on an 11x6 apc. Mine did about 11k6  on the same prop. That's a big difference. 

 

Curiously, his "with" is still nearly 11k. My "with" figure was about the same as his. It seems his silencer is already quite restrictive and the mouse does not further restrict. 

 

Personally I thought the mouse was quite poor. Other brands' baffled silencers were less restrictive and just as quiet. A decent tuned pipe would even see power increase with similar or better silencing properties.

 

YMMV of course. 

 

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12 hours ago, Don Fry said:

Nick, that looks like a tail dragger.

What bit hits the ground if it has a nose down incident. If it’s the silencer, look at the cost of new cylinder heads. The failure point will be the female thread in the head, where the steel of the header meets the aluminum head. If so a sharper bend on the header, and a skid/fusalage bulge might be good. 

Don, it’s my only sport model a Wot4XL that is of course a tail dragger. There is plenty of clearance from the ground and it is positioned ideally for directing the oil residue away from the model. 

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I don't remember having much of a problem with my Mouse but it was probably only flying a vintage model or a trainer at the time so no need for maximum power.

 

I also had a Super 60 and a Telemaster 66 powered by a Merco 35 fitted with a PR strap on silencer. This took the form of a perforated tube inside the silencer body. It was not successful at reducing noise until I took a little loft insulation and packed it between the tube and the silencer body. That made it very quiet and it still flew the models.

 

The finest silencer I have ever fitted to a two stroke was a Weston Genisis Mini Pipe which I fitted to an SC 32 which reduced the unholy racket to a whisper without adversly affecting performance.

 

Nowadays I am mainly a four-stroke man but I'd like to build a sports model for that little SC.

 

Any suggrestions?

Super 60 Merco 35 up.JPG

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