catalytic converter mufflers

I'm wondering why I need to use U bolts since the fit is so snug. Couldn't I just drill a hole and pin it together with a sheet metal screw or two or three? Pictures below show parts laid out. I cut a section of handlebar and a short section of the expansion chamber pipe to use as a coupling. The little manifold piece is not aluminum and neither is the expansion chamber even though it was advertised as aluminum. It is chromed steel and appears to be pretty well made. So, the plan is to bend the handlebar and cut it or the expansion pipe to length for a fit. Good luck, Silverbear. Any tips on bending the handlebar? Just heat it up with the propane torch and bend it? Sounds simple. We'll see if it is, I guess. I don't really know what I'm doing here... just winging it and hoping things work out.
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Well that isn't working out. I can't get the handlebar hot enough with a propane torch to make the bend. So... plan B is to use a short section of handlebar coming from the manifold and another short section fitted into the expansion tank and use automotive type (small engine?) flex pipe to join the two and make the curve. It should be easier to make the fit with an eye toward the optimum 12" pipe length even if it doesn't look as good. I could buy a maps type of torch, but don't want to invest the money at this time. Depending on what is available in flex pipe sizes plan C is to skip the sections of handlebar and go directly from the manifold to the expansion pipe. I think I like plan B better than C, but in the end will like the one that works. Can't get flex pipe around here until Monday so it is again time to hurry up and wait. I'm open to ideas...
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I have one of these things in a kit coming right now, and another on one of the bikes. I'm thinking I'll put an extended lignth 1/2" drillbit right down through the center of the things. I've already cut the spout off & put a 1/2" hole in one of the end caps. It's slightly louder, but has a good sound.
What'ch Y'all think?

I did the same...Bought a 1/4" extended drill bit(foot long).....And just drilled out all the holes....Actually sounds pretty sweet....

Here's where I am with the expansion chamber exhaust. As mentioned in my last post I was not able to get enough heat out of a propane torch to bend handlebar as exhaust pipe. I could have bought a Map pro torch for about $40.00 and would like to have one someday, but not now. So I thought it would be simple enough to go to the hardware to pick up some flexible pipe. I went to three hardware stores, Lowes and a small engine shop and couldn't buy it. I finally found what will work at the local plumbing/ air conditioner business. They were willing to sell me the whole thousand foot roll, but I had them cut it off at one foot. Three dollars for stainless steel flex pipe and about the same at the hardware for two U bolts. I removed the stock pipe and exhaust manifold. I used a few inch section cut off of the expansion chamber pipe to use as a spacer at the manifold since the manifold is of a diameter which fits inside the expansion chamber pipe. The flex pipe is one inch, ID. The inside diameter of the exhaust pipe is the same as a handlebar, or 7/8". I thought it would fit more snugly over the exhaust pipe, but there is a bit of wiggle room. At the exhaust manifold there is the manifold piece which came with the exhaust pipe and bolts on to the engine using the stock gasket (which I may replace with one I'll make out of 1/4" aluminum). That manifold piece is inside the section cut off from the exhaust pipe which is a few inches long. On that goes the flex pipe, tightened down with a U bolt. At the exhaust pipe the other end of the flex pipe is tightened down with the other U bolt. I started the engine with the pull start to see what it sounds like and I'd say it is about the same noise level, but a better or at least different tone. There is some exhaust leak at the U bolts so I will shim it and might try some kind of muffler goop to seal it up. I think I'm, going to use the two little hangers pictured which are copper coated steel and are plumbing fixtures called Millford hangers (if I remember right). I use these for mounting my tin can headlights and cost probably $3.00 for the pair. In the picture the exhaust is just hanging there in the general area it will end up, but is held up with a cord so that I could better visualize things. It is going to be a snug fit seeing to it that the pedal clears, the exhaust pipe doesn't touch the bike itself, it is far enough from the tire, etc. Some fiddling will do it. I'm still in the middle of repairing (I hope) the centrifugal clutch, so won't be riding or able to report anything about a change in how it runs until the clutch is fixed. It will get snugged up a bit tighter into the bike and I like the way it looks, especially compared to the stock exhaust. I like it well enough that I ordered a second one to use on a build this summer. There might be something better out there in pocket bike exhausts, but this will work and at $20.00 including the shipping I'm a happy camper. The length from expansion chamber to the engine is a little over the optimum 12" as it is. I'm guessing 13 1/2 or 14", but I may be able to shorten that up a bit. I'll post another picture or two when it is all done and the bike is running again.
SB

Correction. I must be more tired than I thought. A bicycle handlebar is 1 7/8 inch in diameter, not 7?8". I believe the flex pipe is 2", but didn't measure it. It is as close a fit as I could get.
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Yeah, I think it's gonna work OK. I was already wondering about the turbulence thing. I think in the course of the summer I'm going to get a map pro torch so I can make up a pipe with handlebar. While flex pipe does bend, it doesn't much want to and kind of averages out a general bend where with heat you could bend handlebar just so... right where you want it. I'm guessing it is good bye to the chrome when high heat is applied.
I'm still wondering about how you're going to do the drop stand on your bike. Maybe you are too. I was staring at the American last evening trying to figure a way of using a kind of bolt on little tab it could attach to which would originate at the spot where a fender is bolted on to the dropout behind and above the axle point. That's the only spot of free real estate I can see for the Schwinn American. A drop stand on a 1963 bike might look out of place to some eyes, but the advantage would be great and would make installing an expansion exhaust in the down position possible on a lot more bikes. I think it is a worthy area to investigate. Besides, the motor, chrome expansion tank, etc. is a kind of giveaway that it isn't exactly original.. Of course I'm curious to see what you come up with as a solution on the Rolls once you stop riding long enough for the motor to cool down and fabricate the danged stand. Hint. Thanks for the original tip on the pocket bike exhaust as it got me going down this cow path in the first place (shakes fist while smiling).
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Pictured below is the expansion exhaust on the 39 Elgin. I removed the u bolts and made a spacer/bushing thing of aluminum at each union and also squeezed in some JB Weld epoxy which sealed everything up nicely. Instead of the U bolts I found that good quality Stainless steel clamps worked to tighten everything down In the front I used a plumbing hanger and in the back just a couple of left over strap pieces. Plumber's strap would work as well. I did shorten up the flex pipe so that the pipe from engine to expansion chamber is 12". I may still fiddle a bit more to raise the angle in the back and lower it in the front to better follow the line of the bike frame. The little I've been able to ride the bike due to persistent problems with the automatic clutch has still bee a satisfying thing in terms of the exhaust. The engine has more power and the tone of the exhaust is less tinny, deeper and if not quieter( hard to decide) it is less annoying and actually kind of nice to hear. I really like it. No more hot ankle from the catalytic kit pipe. I also like the way it looks and have ordered a second one while I can get it at $10.00 plus another $10.00 for shipping. Three bucks for the flex pipe and another two or three for the clamps. Call it $25.00, which is about what a kit pipe would cost.
What I would like to do with the second one this summer is use the handlebar instead of flex pipe once I spring for a maps pro torch.
SB

silverbear said:

Pictured below is the expansion exhaust on the 39 Elgin. I removed the u bolts and made a spacer/bushing thing of aluminum at each union and also squeezed in some JB Weld epoxy which sealed everything up nicely. Instead of the U bolts I found that good quality Stainless steel clamps worked to tighten everything down In the front I used a plumbing hanger and in the back just a couple of left over strap pieces. Plumber's strap would work as well. I did shorten up the flex pipe so that the pipe from engine to expansion chamber is 12". I may still fiddle a bit more to raise the angle in the back and lower it in the front to better follow the line of the bike frame. The little I've been able to ride the bike due to persistent problems with the automatic clutch has still bee a satisfying thing in terms of the exhaust. The engine has more power and the tone of the exhaust is less tinny, deeper and if not quieter( hard to decide) it is less annoying and actually kind of nice to hear. I really like it. No more hot ankle from the catalytic kit pipe. I also like the way it looks and have ordered a second one while I can get it at $10.00 plus another $10.00 for shipping. Three bucks for the flex pipe and another two or three for the clamps. Call it $25.00, which is about what a kit pipe would cost.
What I would like to do with the second one this summer is use the handlebar instead of flex pipe once I spring for a maps pro torch.
SB

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the little Bernzomatic mapp torches are really expensive to use.. I had 1 and you use about 6 tanks of oxygen to 1 tank of Mapp gas.. I kept using it because it's what I had and needed the extra heat. but last summer I scored an older AIRCO welding torch off Ebay for $20 and it's set up for Mapp gas.. uses the Mapp tank but it uses a full size high preassure oxygen tank for oxygen

matt167,
Thanks for the tip on the Airco welding torch. I don't know much about this, obviously. I see some bernzomatic torches at the hardware that don't aprear to use anything but the mapp tank, no oxygen. Can the mapp tank setup alone do brazing work on bicycle sized stuff? Can you use a mapp tank with a reguar propane torch or will it not work? It seems like I don't need a whole lot more heat than what the propane torch will put out, but it isn't enough and that's clear enough. Thanks.
SB

you can use a standard propane torch tip with mapp gas. the threads on the bottles are the same, and those mapp only setups are using a propane torch.. Mapp is perffered by plumbers because it gets a little hotter and it allows the solder to flow out faster. but I'm not sure Mapp alone will get hot enough to bend a handle bar.. it might braze thin steel tho

matt167 said:

you can use a standard propane torch tip with mapp gas. the threads on the bottles are the same, and those mapp only setups are using a propane torch.. Mapp is perffered by plumbers because it gets a little hotter and it allows the solder to flow out faster. but I'm not sure Mapp alone will get hot enough to bend a handle bar.. it might braze thin steel tho

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Many thanks for this post. I don't see what I have to lose trying a mapps tank with the propane torch I have. Nothing is lost. Cool.
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silverbear said:

Many thanks for this post. I don't see what I have to lose trying a mapps tank with the propane torch I have. Nothing is lost. Cool.
SB

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I have a jewelers setup at my friends shop i use. for rings, and minor brazing etc. i use a smith mini torch running oxy/propane. from what ive read, it can get pwards of 2700f i have been able to melt silver gold platinum etc with it. i might try using it on bike mufflers and such too. heck why not.

http://a763.g.akamai.net/7/763/1644/4/app.infopia.com/img/image/fp/VPID/4543692/img4/img.jpg

BarelyAWake said:

The solution lol;

"I needed the headpipe for a different project" and that's the result

It's a modified SBP expansion chamber, ported stock pipe & extended glasspack silencer. While the spring retention system on the SBP manifold is great and reduces metal fatigue - I couldn't bear to have the blue hi-temp silicone on my vintage ride... it just kinda clashed and Ima slave to fashion I guess. The extended glasspack quiets the exhaust to roughly equivalent to stock (sounds different/better - but no louder) and other than being 6" or so longer has little/no effect on backpressure as it's a clear passage straight through.

It's a pretty easy mod (glasspack) as it's simply 2" aluminum conduit, a chunk of metal window screen, a lil fiberglass insulation stolen from my wall & a coupla pop rivets, the stock head pipe slid right in to the expansion chamber with a lil chunk of the SBP system as an adapter (yus, I still need to trim & paint the one lil exhaust clamp) o.o

I liked how the curvature of the stock pipe pretty much matched the bike heh *shrug*

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Ok.......Wow...this is a really clean and nice set up!! Thanks for posting this!

silverbear said:

Many thanks for this post. I don't see what I have to lose trying a mapps tank with the propane torch I have. Nothing is lost. Cool.
SB

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All I can say is Harbor Freight for welding equipment

Few more pics of the Cat.......

Nice, Thanks for the pic. I like the way from the start to the finish its nicely tucked in tight and under and out of the way to peddle and so you don’t burn your leg. Also I agree about the stock pipes get real hot don’t touch get burned. Nice Set Up.

Here is a pic of a different cat. Don't know what brand motor or where it came from...