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This small Java applet uses design rules according to ,
, and ,
to size a tuned pipe for a 2 stroke piston engine. The calculations are
assuming a speed of sound in the exhaust gas, which is not known exactly;
also, it depends on the temperature and thus on fuel/air mixture and external
conditions. In this applet, the gas conditions for methyl alcohol (methanol)
and gasoline have been implemented. The results of the calculations can be
used as a good starting point for experiments and fine tuning, deviations of
+/-10% are surely possible.
- Measure the timing of your engines exhaust and transfer
ports in degrees (see below).
- Measure the dimensions and calculate the area of the exhaust port
opening in the sleeve.
- Assume the velocity of rotation of your engine in rpm (dreaming doesn't
help much though).
- use the sliders to adjust the values according to your engine, or
- enter the corresponding values into the text fields and press [enter]
to update the graph.
- Printing and Exporting only works, after you have
adjusted the appropriate Java security settings of your browser.
You could create a hardcopy of the program window, though, using your
systems suitable tools.
- You can manually plot the cones to build a paper model or to transfer
the shape onto sheet metal by using the values of R and phi
noted below each cone. Plot two concentric circles (having the same center)
using the two radii R. The flattened cone spans a segment with an opening
angle of phi degrees between the two circles.
- The Print... command will print a scaled version of the cones.
The Export... command will create two AutoCad compatible DXF files
for the two cones.
Determining the Timing
|The animation shows, how to measure the timing angles of exhaust and
transfer port. These angles define how long the ports are open,
expressed in crankshaft angle. You can attach a disk with divisions in
degrees to the crankcase and a pointer to the crankshaft (or vice
Then you adjust disk and pointer so that the it indicates 180° when the
piston is at its bottom dead center. Now you turn the crankshaft until
the port of interest closes (when the piston crown arrives at the upper
edge of the port). It is helpful to point a flashlight or a halogen lamp
through the plug hole or to remove the cylinder head.
Reading the angles in both directions must be symmetrical to the bottom
dead center, e.g. a port opening at at 100° must be closing again at
360°-100° = 260°, as shown in the animation. The port timing angle
(shown in blue) is then 260° - 100° = 160°. This means, that port is
open while the the crankshaft turns 160°.
Usually the transfer port will have a shorter timing than the exhaust
Used Formulas (a mixture from , ,
The opening angles of the cones should be 4° to 10° for the opening cone
and approximately twice this value for the closing cone.
Cut view of a tuned pipe with silencer.
Enlarged view of the muffler section.
F3D Pylon Racing Engines with some engines
optimized for tuned pipes,
Peter Soule's documentation to learn more about the history of tuned pipes
for model engines,
my Silencer Application software, including a
similar tuned pipe designer.
How to download JavaPipe to use as a standalone Application
Remark: to use JavaPipe in the standard way in your browser, over
the internet, it is not necessary to perform the procedures described in this
section. I cannot give much support to solve any problems occurring while
running your local copy based on your local Java installation. If you have not
already a working Java system on your machine, you might want to consult a
If you want to run your local copy of JavaPipe , you can download a copy of
the JavaPipe archive to your disk. You can also save the applet page to a
local file, depending on the method you want to use for running you local
Step by Step Instructions to download the required files
- Check, whether you have a Java virtual machine (VM) installed on your
- Windows: open a command window and execute the commands jview
and wjview. Usually a Java VM can be installed during the
installation or when upgrading the Microsoft Internet Explorer.
- Unix: open a shell or xterm window and execute the command
- If these commands can be found, your system probably has a working Java
installation. If not, you will have to get the appropriate Java Runtime
Environment (JRE) for your system from Suns web site
- Download this html file from
- Download the ZIP archive with the class tree from the following web
- Create a subdirectory "java" below the directory, where you have copied
this html file and move the javapipe.zip file into this directory.
- Now you have both files to run JavaPipe either as an applet or a
standalone application. You can run the applet by loading this html page
into your browser or by using the AppletViewer.
[More details can be found here].
- To make life for Windows users easier, you can download the following
VBScript file to start JavaPipe as a stand alone application:
Using this script and the archive, you can run JavaPipe by merely clicking
onto the .vbs file.
- To make life for Windows users even easier, you can also download the
following Windows Installer file which contains all you need and installs it
To re-install or de-install use the "Software" applet inside the System
Control Program of Windows.
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This is a privately owned, non-profit page of purely educational
purpose. Any statements may be incorrect and unsuitable for practical usage. I
cannot take any responsibility for actions you perform based on data,
assumptions, calculations etc. taken from this web page.
© 1996-2006 Martin Hepperle
You may use the data given in this document for your personal use. If you use
this document for a publication, you have to cite the source. A publication of a
recompilation of the given material is not allowed, if the resulting product is
sold for more than the production costs.
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