Peter Griffiths

Areas Peter Griffiths is Knowledgeable in:

Techniques Peter Griffiths Uses:

Peter Griffiths's Problem Solving Skills:

1. Aerospace
2. Sonar
3. Physical testing
4. Bonding of materials
5. Microwave Composites
6. Environmental Testing

Peter Griffiths's Problem Solving Experience:

1. In the manufacture of sonar arrays, large (500kg) castings of polyurethane rubber were made.
   These suffered from voids due to shrinkage on curing.
   I devised a method of determining the rate and degree of shrinkage of all of the materials we used, from an extremely tacky gel, to a hard rubber.
   The only methods in international standards are applicable to hard materials, and are unable to measure the rate.
2. Solved grating lobe and 'crisp packet' effect in sonar arrays. Determined the source of the problem, plasticiser migration, and formulated the solution. Successful in its outcome.
3. A replacement for a microwave material was required having precisely the same dielectric and loss factors. I found commercially available materials which were not homogeneous, flat or parallel.
   I devised the composition of a new material, its method of manufacture, made the tooling to make it, and went on to manufacture the composite and determined the process to convert it into the finished product.
   Each sheet of my material was 18" square, flat and parallel within 0.002"
   Each one of a particular missile contains a number of these components
4. In the manufacture of large polyurethane rubber composites, some of the components used were very dense and some, very light. One particular material had to be mixed in the morning and used the same day, so there was no time to make test pieces to ensure quality.
   If the casting (250kg) was made and found to be sub-standard, not only would it have to be chiselled off (several man-days), but the material costs would be lost.
   I determined a way of testing the 'Part A' that would ensure success, and also determined the optimum manufacturing and storage conditions to reduce degradation of the light filler material.
5. I was tasked to determine a means of manufacturing millimetric radar components.
   I commenced by making mandrels from polyethylene, electroforming onto them and then heating to vapourise and remove the polyethylene.
   Although relatively successful, if a number of these components were required to fit together, the slightest distortion of the plastic might render it difficult or impossible to do so.
   I then made more rigid mandrels from aluminium which could be machined or wire eroded much more accurately, and which were subsequently electroformed to form the components. The aluminium was dissolved out using NaOH.
   Using this method, I made horns, junctions, crossovers, branches etc.
6. Emitter quality of radar components was declining.
   The tungsten filament was made from wire, braided, formed to shape, cleaned, then assembled into the emitter.
   The cleaning process was suspect. Any salts on the filament could cause hot spots promoting failure. Four ladies cleaned the filaments, one of whom was not keen to use a newer method of cleaning. I introduced route cards for the process and could show that she was blameless. I observed the process carefully. Degreasing, electrolytic cleaning, etching, neutralising, several rinses, dip in acetone and blow dry. The compressed air was clean (I dismantled and re-assembled the system).
   One lady was found responsible for 99% of the failures, but how?
   A chance remark gave me the answer. She thought these 'funny solutions' were the problem, and when we weren't looking, she often gave the filaments another rinse under the tap 'just to make sure'!
7. The requirement was for a small, very light, fresnel type reflector with a metal surface.
   I had a 'negative' of the mirror made in stainless steel, electroplated it with a thin layer of nickel, and whilst still on this former to avoid distortion, reinforced it with a carbon fibre/epoxy composite which incorporated the mounting lugs.
   The production run used this method of manufacture.