Quote:
Originally Posted by VFR750
Isn't the deflection of the diaphragms controlled by the central plunger and control pressure?
If you double the thickness you will increase the stiffness at lest 4x.
Why do you want it thicker? Material availability?
Stainless is chemically compatible with iron. Rubber probably better suited for aluminum verses stainless. There would be galvanic reaction with any water in the fuel. Good question though. Why rubber?
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In simple flexure terms I think that the stiffness of a beam is proportional to the cube of the thickness so double thickness is 8X.
I would imagine a clamped diaphragm would behave a bit differently to this simple model but the stress analysis for this configuration would be tricky and doing FEA too time consuming.
I don't think that the stiffness of the diaphragm is part of the control system. The plunger depth is controlled by the air sensor and must be very free in its operation.
The springs that are used to control each piston must be much softer than the stiffness of the diaphragm and if the idea is to accurately control a differential pressure then in the limit maybe the diaphragm should be infinitely stiff?
The difference in stiffness between the Stainless steel and the reinforced rubber diaphragms would also be at least an order of magnitude and both types seem to work.
I suspect that the thickness of the diaphragm will influence the volume of fuel delivered for a given pressure as it changes the volume of the chamber and it is this aspect of the design I am struggling with. I am not 100% sure I have understood the operation of the distributor well enough.
The reason for my interest is due to the problems of sealing rebuilt distributors and the use of Permatex Indian Head Shellac which is hard to apply well although I am sure that other sealants may work.
I have been looking at the repair 'kits' available and none of them really deal with the sealing issue very well.
I have been looking into applying a vacuum deposited 'conformal' coating to the diaphragm which would mean that the use of any painted on sealer could be avoided.
Handling a 0.1mm sheet is tricky and a 0.2mm thickness would make this process much more straightforward.
We are looking at applying a 10 micron coating on each side.
I do realise that there are several 'expert' refurbishing companies that overhaul these parts but we want to try to produce our own solutions.