FT: Frame (Twin) Elephant trunk breather
- Thread starter Vincent Brake
- Start date
What are they Vibrac ?
A different forum that I have visited had a feature called stickies so that memorable bits like this post of Vibrac's can be floated to the top of any thread that mentions breathers.
The valve shown by Vibrac is similar to the one I use in the breather cap, but there are a few reasons why I made the valve in an inspection cover.
Firstly, Vibrac's valve would be great on a racer, but for me the aesthetics of a valve within a cap are more appealing for a road bike. Secondly, a PCV works better the nearer it is to the engine - located in the cap places it as near as is possible. Thirdly, the valve within this type of PCV has a very light spring, but much of the valves closing pressure is provided by the weight of the 'plunger' inside the casing so it needs too be positioned sufficiently upright so that gravity helps to close the valve, or the operating efficiency is much reduced. There are quite a few different spring/plunger weights inside identical valve casings depending on their original application. I tried a lot of different valves before I settled on one which gave the best results. Too weak a valve and it doesn't work, too strong and it can create too much vacuum within the cases which is undesirable.
This was just a project for my bikes, I got interested so spent time researching and working on it. I never intended to 'go into production', but I was asked by a few people to make them one so have produced a few batches when I have time.
Firstly, Vibrac's valve would be great on a racer, but for me the aesthetics of a valve within a cap are more appealing for a road bike. Secondly, a PCV works better the nearer it is to the engine - located in the cap places it as near as is possible. Thirdly, the valve within this type of PCV has a very light spring, but much of the valves closing pressure is provided by the weight of the 'plunger' inside the casing so it needs too be positioned sufficiently upright so that gravity helps to close the valve, or the operating efficiency is much reduced. There are quite a few different spring/plunger weights inside identical valve casings depending on their original application. I tried a lot of different valves before I settled on one which gave the best results. Too weak a valve and it doesn't work, too strong and it can create too much vacuum within the cases which is undesirable.
This was just a project for my bikes, I got interested so spent time researching and working on it. I never intended to 'go into production', but I was asked by a few people to make them one so have produced a few batches when I have time.
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I am sure that young John's solution is a well thought out and neat solution there are myriad solutions looking for an oil stain.
I understood the reason for the vertical mounting of the in line valve was so the oil could run back to the engine but gravity could play a part
It may be serendipity but the valve worked on the twin racer out of the box two teaspoons of R in the mandatory catch tank at the end of the season BUT it's no substitute for a tired engine
I understood the reason for the vertical mounting of the in line valve was so the oil could run back to the engine but gravity could play a part
It may be serendipity but the valve worked on the twin racer out of the box two teaspoons of R in the mandatory catch tank at the end of the season BUT it's no substitute for a tired engine
Pardon my ignorance but is PCV being used to mean Pressure Control Valve or Positive Crankcase Ventilation, as I have come across both. The simplest breather valve I've seen was a piece of lay-flat tubing on the end of the pipe. Cheers, Stu.
Stu, those are mentioned here: https://www.vincentownersclub.co.uk/index.php?threads/breathers-can-anyone-help.7117/#post-56699
I thought PCV was Philip Conrad Vincent. You should know that Stu.
I'll put my tin hat on now.
Simon