Although the majority of cars use what is essentially a solid, non-flexible method of fastening the outlet end of the exhaust pipe to the model car, there are different options worthy of consideration.
Hardened steel wire sold by most model shops used for control linkages, pivots pins, etc.. To the best of my knowledge it is only available in imperial sizes (fractions of an inch).
Why Consider Alternative Mountings?
Model car exhaust systems on the 1/8th and 1/10th scale IC circuit cars are easily damaged in race accidents and the normal exhaust mounting wire method shown to the right is essentially solid and does not allow for any movement in the event of a collision. It also does not allow for any kind of dampening of the vibrations generated by the engine.
Flexible Exhaust Mountings
Some of this damage can be lessened or eradicated by the use of a flexible mounting system. This flexible mounting can also reduce the high frequency vibration that can lead to parts failure.
Whilst I have personally made different types of exhaust mounting for many different model cars the Serpent Veteq comes with a good example to demonstrate why this type of mounting is advisable.
Pictured left is a spring like that used on the Serpent Veteq and on the right is an animation that you can Play that shows how the use of a spring in this way allows for lateral movement of the exhaust.
(Please note that the spring can move both ways)
Restricted Movement
The amount of movement that any exhaust mounting can make possible is ordinarily very restricted on a model car due to the relatively larger than scale exhaust that needs to be fitted as close as possible to the centre of the car. The spring used on the Veteq reduces this movement due to the orientation of the spring and is only really suitable for exhausts with a vertical hole for the mounting wire.
This is not meant as a criticism, the orientation of the spring is good for absorbing the engine vibrations and allowing downward movements.
Alternatives
There are a few alternative solutions to mounting an exhaust whilst allowing some movement. The first of these is shown to the right and uses a coil spring of similar dimensions to one that would be found inside a pen, only using a heavier gauge of piano wire. The retaining grub screw is left out and allows the exhaust to move with only the restriction provided by the spring.
Another worthy alternative uses a mounting wire like one that would be supplied with the car, but with a larger loop, so that an ordinary rubber grommet (yellow) can be fitted inside. This is good and inexpensive solution for those cars where the end of the wire can be mounted to either the chassis
or the radio tray. An extension to this idea would be to fit a bush down the inside of the grommet so that the retaining bolt/screw could be tightened up fully without compressing the grommet too far.
The third suggestion we have was originally suggested and fitted as a replacement on a Serpent Veteq for the reasons given in the relevant article. More
Please note that the coil of the wire is apart slightly to stop metal to metal contact, which could give rise to radio interference as well as adding to the vibrations generated by the engine.
Words of Warning
Apart from the grommet solution, all the suggested mountings mentioned in this article involve metal to metal contact, which can give rise to radio interference.
We have seen various types of exhaust mountings, some which were made from heavy gauge wire, that resulted in the manifold/header cracking and breaking in two. This is presumably because the vibration generated by the engine is transmitted back through the exhaust and causes the metal to almost shatter, like a glass does if subjected to high frequency sound vibrations. We would be interested in the opinions of any scientists/physicists out there.
Summary
We have tried to present the various different variations on providing some means for the exhaust to move and, although there are others, we feel that the basic theory will be understood by the information and examples given.
For help with the terms used throughout this series of pages, please see the Engine Terminology section.
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