Two stroke engines fascinate me. They are so simple and fun that I've always enjoyed tinkering with them. There are many ways to boost the power, one of which is by installing a "tuned" pipe. The way a two stroke motor works causes them to be fairly noisy and a bit inefficient. A tuned pipe has a set of cones- Divergent (meaning the cone gets bigger) and Convergent (meaning the cone gets smaller) that are built to cause "echoes" or pressure waves to reflect back, which if done properly can increase the power of the engine. Check out this link, it will make a little more sense.
Animation of Two Stroke expansion chamber:
http://upload.wikimedia.org/wikipedia/commons/5/52/Arbeitsweise_Zweitakt.gif
As the pressure wave reflects back, it has a similar effect to turbocharging or supercharging a 4 stroke- it rams fuel and air that leaked into the pipe back into the cylinder under higher pressure, causing the motor to have more power (more fuel & air = bigger bang). That's a very loose explanation, but there you go.
I've always wanted to build an expansion chamber... This is where P.O.J. (pronounced Podge) comes in. This Piece Of Junk was (and is) my first motorcycle... found it in a grain bin around '95, back when I wasn't allowed to have bikes. Somehow, this one snuck home. I dug it out of storage a few years ago and began this process, so follow along as I make mistakes and learn a thing or two about building your own expansion chamber!
Please note, this is NOT the only way to do this. I think there is an easier way- done by cutting out two sheets in the correct shape, welding the edges, and the pumping ultra high pressure water in to "expand" the pipe, but I didn't have the tools at the time to do it like that. This is just how I did it...
Animation of Two Stroke expansion chamber:
http://upload.wikimedia.org/wikipedia/commons/5/52/Arbeitsweise_Zweitakt.gif
As the pressure wave reflects back, it has a similar effect to turbocharging or supercharging a 4 stroke- it rams fuel and air that leaked into the pipe back into the cylinder under higher pressure, causing the motor to have more power (more fuel & air = bigger bang). That's a very loose explanation, but there you go.
I've always wanted to build an expansion chamber... This is where P.O.J. (pronounced Podge) comes in. This Piece Of Junk was (and is) my first motorcycle... found it in a grain bin around '95, back when I wasn't allowed to have bikes. Somehow, this one snuck home. I dug it out of storage a few years ago and began this process, so follow along as I make mistakes and learn a thing or two about building your own expansion chamber!
Please note, this is NOT the only way to do this. I think there is an easier way- done by cutting out two sheets in the correct shape, welding the edges, and the pumping ultra high pressure water in to "expand" the pipe, but I didn't have the tools at the time to do it like that. This is just how I did it...
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Signing UpStep 1: Equipment, Skills, and Supplies.
This is NOT an easy quick project. It requires a lot of big, expensive tools. I'm lucky enough to have access to a shop that has everything I needed. There are alternate ways to make pipes, which I will discuss at the end of this instructable.
Skills you should have:
-Ability to Weld
-Ability to mark & cut metal ACCURATELY
-Understanding of and ability to use Shears, Brakes, and other metalworking tools
-Safe work ethic
-Understanding of 2 stroke engines
-Ability to use expansion chamber design software (OR, be really good at math or want to build 50 different pipes (trial and error))
-lots and lots of TIME
Supplies:
-Cold Rolled sheet metal- I used 18 gauge
-LOTS of welding rod- I used a 110v wire feed welder
-Rubber stoppers for isolation mounts
-Misc. nuts and bolts for mounting
-Duct Tape, shop towels, and band-aids. You never know!
Tools:
-Safety equipment- safety glasses, ear plugs, gloves, etc.
-Measuring & Marking tools- marker, scratch awl, steel rule, dividers, etc
-Squaring Shears
-Electric shears or aviation snips
-Hammer (ball pein works great!)
-Stake table with appropriate stakes
-Box and Pan Brake (could just use stake table but...)
-Welder (something capable of welding thin metal!) and related supplies- wire brush, clamps, gloves, helmet, safety gear, etc.
-Hack saw or metal cutting Band Saw
-Drill or Drill Press & drill bits
-Grinder and/or file
Other Usefull Things:
-2 Stroke expansion Chamber Software- I used 2 Stroke Wizard by Build and Click. Cost $20.00, came with a 4T header design program and a cone printing program that breaks large cones up to fit on 8.5x11 pages you can cut out and tape together. Great program. I tried a few free ones, but the first attempt at making a pipe from those didnt work so well...
-The Book Two Stroke Performance Tuning by A. Grahm Bell (apparently, not THAT A.G. Bell...)
-Someone who knows what they are doing, so you can ask questions! In my case, that was advrider.com
Skills you should have:
-Ability to Weld
-Ability to mark & cut metal ACCURATELY
-Understanding of and ability to use Shears, Brakes, and other metalworking tools
-Safe work ethic
-Understanding of 2 stroke engines
-Ability to use expansion chamber design software (OR, be really good at math or want to build 50 different pipes (trial and error))
-lots and lots of TIME
Supplies:
-Cold Rolled sheet metal- I used 18 gauge
-LOTS of welding rod- I used a 110v wire feed welder
-Rubber stoppers for isolation mounts
-Misc. nuts and bolts for mounting
-Duct Tape, shop towels, and band-aids. You never know!
Tools:
-Safety equipment- safety glasses, ear plugs, gloves, etc.
-Measuring & Marking tools- marker, scratch awl, steel rule, dividers, etc
-Squaring Shears
-Electric shears or aviation snips
-Hammer (ball pein works great!)
-Stake table with appropriate stakes
-Box and Pan Brake (could just use stake table but...)
-Welder (something capable of welding thin metal!) and related supplies- wire brush, clamps, gloves, helmet, safety gear, etc.
-Hack saw or metal cutting Band Saw
-Drill or Drill Press & drill bits
-Grinder and/or file
Other Usefull Things:
-2 Stroke expansion Chamber Software- I used 2 Stroke Wizard by Build and Click. Cost $20.00, came with a 4T header design program and a cone printing program that breaks large cones up to fit on 8.5x11 pages you can cut out and tape together. Great program. I tried a few free ones, but the first attempt at making a pipe from those didnt work so well...
-The Book Two Stroke Performance Tuning by A. Grahm Bell (apparently, not THAT A.G. Bell...)
-Someone who knows what they are doing, so you can ask questions! In my case, that was advrider.com
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Cheers Rich.
The info there exposes the flaws in the former ways of thinking about pipes and how to design them. If you are serious about pipes and want the best results at zero cost then check it out!
You have managed to break down a fairly complex operation, combine it with the relevant theory and still make it readable.
It's a 1967 Yamaha YL100C- also known as a Trailmaster. Yamaha also built a "street" version called the Twinjet, which was a 100cc 2 cylinder two stroke. Mine was meant to be a dual sport, but I'm in the process of converting it to a cafe bike.
Nice article, BTW :-)
http://www.youtube.com/watch?v=S_bpV11N0zg
here's a vid of my pipe its on a 50cc 2 speed automatic bike:)
http://shrani.si/f/2L/4E/4mCdnXas/3.jpg
and heres the last pipe i made, that still needs to be tested
One book for the average rider you left out of your list is the late great Performance Bikes Tech author John Robinson's "2 stroke tuning" the other book for the "scientists" is Prof. Blair's research paper
Keep up the good work.
so you can get the most ride-ability out of the bike
http://www.youtube.com/watch?feature=player_embedded&v=DGszBVy3cgU
The other thing that is cool to play with on a piston port 2 stroke is putting a spacer under the barrel it changes the port timing, and can make a sedate putt putt scooter into an animal. Try making a base gasket out of 2 or 3mm aluminium, you will be surprised. it works even better if you take 2 or 3 mm off the top of the barrel, to keep the compression ratio the same.
I am a stick welder apprentice, and to weld thin sheet I use a method that I invented: use an additional black iron wire, as in autogenous (Oxy-Acetlyne) welding. It is not easy, but allows some welding tasks otherwise are very difficult.
A question: the "tuned" exhaust seems like a resonant circuit. Does it enhance the motor only in a certain speed or range of speeds? Forgive me if you said that, I don't speak English and it is difficult for me to read and undestand all the text.
I believe TIG welders *dip* the rod in the puddle when welding aluminum for the same purpose- to cool the base metal.
My pipe was designed to be a little less effective but cover a larger rpm range. Some pipes can cause the engine to be very sluggish unless its in a very narrow rpm range (my first pipe, for example). That type of pipe has a VERY notice-able powerband- when it hits the right rpm range, the engine really takes off.