Vire 7 - Hints and Tips

Breaking the Siphon in Below-the-Waterline Installations

The Principle: Instead of leading the water directly from the water pump into the bottom of the exhaust gas collector (the original installation), lead it up in an inverted "U", above the waterline, and back down into the exhaust gas collector. Then, fit a T-piece and a one-way valve at the top of the "U", so that air leaks into the system when the pump is off, and the siphon is broken.

Here's the original installation (click for a larger image): -

Click for a larger image

And here's the new installation: -

It might seem simplest to fit the siphon cut between the outlet from the cylinder and the inlet to the exhaust. That was where Dick made his first atttempt, but pressure variations due to pulses from the exhaust made that checkvalve unstable in its pumping.

To avoid these problems, the valve must be installed directly after the impeller pump. At the same time Dick also took the opportunity to modify the inlet, as a bonus, to make the engine a lot easier to work on.

  1. First, he straightened the small waterpump outlet pipe slightly, to improve the water flow from the pump.
  2. Then, he cut away the small inlet pipe on the exhaust chamber, made the surface even, and blocked the original inlet.
  3. Finally, he fitted a new 1/4 inch elbow connection in a more convenient location.

Note that these changes to the configuration of the inlet pipe are not essential.

To left is a photo of the bit of hose leading up from the T-piece to the valve. The key to success is that the BOTTOM OF THE T-PIECE (i.e. the top of the inverted "U") must be above the waterline.

You can also see how Dick has used a series of hoses of differing diameters to adapt from one size component to another.

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