a cheap sport muffler

by HalfaDave on Wed Mar 20, 2024 10:41 am
Hi roddie,
That is an awesome Cox.049 muffler.Cool
Ingenious !
Fantastic photos and journey, thanks for sharing with us.
This is why I like this CEF.Smile
Thanks,
Dave

balogh wrote:
That is what I call a Muffle-Bee...congrats Roddie, indeed attractive and practical design...any chance for a video to assess the muffled COX sound? Unless you have the leather strap for an easy cylinder removal, I would encourage filing the flats on the top fin for the wrench...Been there, seen that, done that couple times and despite my limited craftsmanship, not one single cylinder I filed ended up with destroyed top fin...

Thanks Dave and Andras! I thought I'd previously posted a vid.. but here's one which shows that; removal of the engine-cylinder is NOT required for the installation of this muffler. In fact; it shows installation and removal of the muffler, while the engine is running.

I'm using the Ace/Cooney venturi-throttle designed for the Cox Bee engines.. and I have a flywheel installed on the output-shaft.. which is why the fuel/air mixture favors fuel.. (running "rich") to help keep it from overheating. Ordinarily I'd have a Cox heatsink (cat.#1970) installed for non-aero engine-running.


...   I had to swap electric-starters.. but I get it worked-out fairly quick. Editing? We don't need no stinking editing...  

Roddie, that is interesting that you can remove and replace your synthetic muffler very easily. And, I thought my Cox .049 R/C Bee's silicon cover over the throttle ring with muffler flange was easy to remove.

GallopingGhostler wrote:Roddie, that is interesting that you can remove and replace your synthetic muffler very easily. And, I thought my Cox .049 R/C Bee's silicon cover over the throttle ring with muffler flange was easy to remove.

Hi George, Yes; the unit is a push-on/pull-off design. A pressure-tap is also an available option.

I got it, Roddie...so the aluminum ring inside diameter is larger than the diameter of top fins...

And your throttle response is fantastic, thanks for re-posting the video.

Rodiee friend, the video is great! The engine response is instantaneous! It is noticeable when you apply the muffler how the sound drops.
I really like how you are always interacting with alternative material to make pieces applicable to the hobby.
I remain attentive to your progress! Thank you for the video and showing all the steps with very clear photographs!

balogh wrote:I got it, Roddie...so the aluminum ring inside diameter is larger than the diameter of top fins...

And your throttle response is fantastic, thanks for re-posting the video.

Yes Andras; that's the simplicity of it.. The Cooney/Ace throttle design recommends the use of a muffler to to hold heat to the top-end for a more reliable low-idle. When tuning is optimal; the throttle-response is nice. Test-bench tuning for this throttle isn't too difficult. An aircraft engine's propeller unloading in flight is another story.. and one that I have zero experience with.

MauricioB wrote:Rodiee friend, the video is great! The engine response is instantaneous! It is noticeable when you apply the muffler how the sound drops.
I really like how you are always interacting with alternative material to make pieces applicable to the hobby.
I remain attentive to your progress! Thank you for the video and showing all the steps with very clear photographs!

Hola my friend Mauricio!! Viva la Citabria! We learn from each other! It makes this hobby very enjoyable! There's so much more to learn!

I'm thinking about a new application for my muffler. Having it encapsulate an exhaust throttle ring. It will definitely require the R & R of the engine's cylinder for installation.. but I'm thinking about how I can make it work.. with an easily adaptable and adjustable linkage. The "inner-ring" (throttle-barrel) would need to attach internally to the outer (Silicone) component.. so that they can rotate together.. about the engine cylinder. An exterior link can be as simple as an "L" bend stuck-through the rubber.. in a radial location that works.

Roddie,

providing you can produce a free moving exhaust throttle ring with a circlip on it (like the stock throttle rings of COX), a 1mm thick music wire passing between the top and bottom silicon muffler discs, between 2 staples holding them together, connected to the circlip eye, should work..

balogh wrote:Roddie,

providing you can produce a free moving exhaust throttle ring with a circlip on it (like the stock throttle rings of COX), a 1mm thick music wire passing between the top and bottom silicon muffler discs, between 2 staples holding them together, connected to the circlip eye, should work..

Sorry for not acknowledging this post until now Andras.. sheesh... 6 months ago..

A few days ago, I got together with some friends. We meet every other Thursday around 6:30 pm. They were curious about the Cox .049 reed engine in my outrigger which I had showed them at our last meeting. So this time I brought a similar Cox engine to bench-run for them to see and hear... (sorry.. no vid.. but will make one to duplicate the results)

I ran it with open-face exhaust first.. then restarted it and while running; popped one of my mufflers on.. down-over the cylinder. The noise-reduction was SIGNIFICANT. I had pre-installed a header-pipe with a .156" aperture.. which I'd never tried before. Actually; I'm pretty sure that I'd only tested full-flowing (.204"/.205" ID) pipes up until now.. even though I had drilled-out a myriad of smaller-orifice pipes to test, when I first designed the muffler.



Here's a comparison between a full-flow pipe and a reduced-flow pipe..









This muffler's pipe had a 4" length of silicone tubing attached for the test.. which will also affect the "tone" of the exhaust flowing through it. This tubing has a .187" (3/16") inner diameter which maintains a snug-fit on the .228" OD pipe (.22 cal. shell casing) and also holds the pipe captive inside the muffler assembly.







For comparison; my full-flow pipe has a .205" aperture (through-hole drilled) and an area of 0.033" The pipe with a .156" aperture has an area of 0.019" which is almost 1/2 the area of flow-potential.. yet I didn't notice an audible drop in engine RPM.

If the weather tomorrow permits; I'll do another bench-run and shoot a video to demonstrate.

Shown here on my rigger-build; a red sheet-silicone body. Sheet-thickness is .045" as are the other two colors that I have. It seems to be the best all-around thickness for that material.

Running a single/full-flow pipe, through a length of the 3/16" ID Silicone tubing routed to a 2nd full-flow pipe through the transom.



I could also try running a reduced-flow pipe at this location.. either as an experiment or as a matter of necessity.  



This exhaust configuration is actually a catalyst for a new test; the swapping of differing-aperture pipes "externally".. rather than having to remove the main-pipe from the inner-housing (ring). The main-pipe would be full-flowing (and permanent..) with a short length silicone extension-tube attached; and to where a reduced-flow pipe is installed on the opposing end.

Theoretically....... this expands the exhaust-tuning possibilities quite a bit. I've wanted to try dual-pipes; spaced varying degrees apart (IE 90 and 180 to start..) which requires drilling two 15/64" holes through the inner-ring at the needed spacing.. and installing a pair of full-flowing pipes with short silicone extension-tubes attached. This will no doubt; augment the flow.. and possibly scavenge it to some extent. This would probably depend on whether or not the cylinder employed sub-port-induction. Regardless; it could be fun to mess-around with.