Member postings for Bill Pudney

How about providing a set of drawings linked to MEW. Following the "Engineering for Beginners" series by Mick Knights for instance.

Everyone needs to start somewhere, and we all need decent toolmakers clamps, calipers, odds and ends.

cheers

Bill Pudney

Michael Williams asked about working on Hovercraft. Crikey where do I start?? In 1964 when I started there, hovercraft were out of the experimental stage, and getting into the development stage. In fact they were pretty much in that until after I left in 1969.

Saunders Roe were basically an aircraft company (remember the Princess flying boat, SR53 rocket/jet experimental interceptor....M2.2 climbing at 45 degrees!! and the Black Knight rocket) so obviously their Hovercraft used a lot of aircraft techniques in construction.

In 1964 the Big Thing that I was aware of was skirt development. At the time (hovercraft) skirts weren't very flexible, and had a very short life and involved a very high level of maintenance. The skirt material would delaminate and flog itself to shreds. In the building next to the dormitory I was in (Saunders Roe was in East Cowes on the Isle of Wight, and they maintained an Apprentice Hostel for their mainland Apprentices) was the wind tunnel. Attached to the out side of that building was something called a "Flapping Rig" where samples of skirt material could be flapped to death, At the beginning skirt material would last maybe 1 hour, Avon (the tyre company) developed a thin, flexible, relatively light material. It took two or three years, but eventually the Flapping Rig was running continuously. Technically this was a great achievement, but the rig was very noisy...imagine a piece of neoprene/cloth laminations three feet by two feet or thereabouts and 2.5mm thick flapping in an 80 knot breeze! We were expected to sleep forty feet away from it.

Then there was the story of training Hovercraft pilots. When performing a turn Hovercraft drift downwind, so when performing consequtive 360 degree turns you can imagine that the hovercrafts course would look a bit like a spring. So there was the hovercraft with it's Middle East Trainee Pilot, doing consecutive 360 degree turns, drifting slowly down on a bloke fishing from a small dinghy, it was the Solent after all. The instructor a bit concerned asks trainee if trainee had seen the fisherman,

"Yes" says trainee,

"Are you going to take avoiding action" says Instructor

"No, its only a fisherman" says Trainee, whereupon Instructor takes over control.

When SRN4-001 was finished, before she could start flight trials the Board of Trade required that she complete a 24 hour full power tethered trial. This was started on a Saturday and could be heard all over Cowes, East and West. Now four Proteus gas turbines, driving four 19 foot diameter paddle blade props, and four huge fans makes a lot of noise, but I don't recall any complaints.

Then there was the story about the SRN4 when on test flights. The story goes something like.....

SRN4-001 was on trials in the Channel, some way South of the IOW, when up comes an RN Patrol Boat. There was some confusion as to whether it was a "Dark" Class boat or "Tenacity", but anyway. Being very polite the RN Skipper asks of the hovercraft "everything ok", sees that all is indeed ok and starts to accelerate away. Whereupon the SRN4 accelerated up to its maximum speed (which was well over its Board of Trade limited speed, but that hadn't been imposed yet) and flew past the patrol boat. It was apparently that trip that the Hovercraft achieved its highest speed, something over 80 knots.

In the Machine Shop was a huge long skinny mill, the bed of which was probably over 70 feet long which was used for machining wing spars. It was designed and built to machine the wing spars for the Princess. This machine was installed in the corner of the shop, closest to the sea wall, which was probably about 40 feet away. I assumed that the tide tables on the wall were for general interest, but no. The tidal rise and fall made the bed move up and down, and the only operator who could make any sense of it, apparently used to suck his teeth, pull his chin and mutter, then as the straddle mill was working its way down the bed would crank in a bit here and crank out a bit there....amazing.

Anyway its past my bedtime

cheers

Bill Pudney

Michael Williams asked if anyone had personal experience of the Redux process. When I did my apprenticeship way back in the '60's the company was making hovercraft. Most of the large panels were stiffened by the the use of folded stringers of witches hat section bonded to large flat sheets which were up to 8 feet long. At the time we were told that they were bonded using the Redux process, which was (we were told) an epoxy based adhesive. The stringers had the adhesive applied by roller, they were placed in position, an "anti-tear" pop rivet placed at each end of the stringer, the whole assembly was then placed in a press which applied heat and pressure. Test samples were made of each adhesive mix, and after curing were subjected to a standard peel test. After curing the hollow stringers were filled with expanding two part foam. The bigger panels were full sheet size, I suppose 8' x 4', from memory (it was all nearly 50 years ago) and had a stringer about every 6 or 8". The panel and stringer material thickness was about 18swg (0.048" ? thick) the whole panels were as stiff as a really stiff thing and very light.

If you can find any pictures of an SRN4 hovercraft, pretty much the whole exterior utilised these panels.

I've just put "Redux Process" into Wikipedia, it's worth a look!!

cheers

Bill Pudney

I agree that HSS is better. Also look for "ground thread" taps. Most "name" manufacturers grind taps

In my experience all carbon steel taps have gashed flutes which leave burrs on the threaded portion. How a reasonably accurate thread can then be generated is a mystery to me.

Also for what its worth, I would suggest that buying a set of taps be avoided. Better to buy good quality taps as and when you need them.

Finally avoid second hand taps, unless they are clearly unused.

cheers

Bill Pudney

When I had to work for a living we had to make some satellite bits out of grades 2 and 4 Titanium. The parts had lots (dozens per part) of M1 threads. Conventional very high quality cutting taps were lasting maybe two threads, they usually broke after two, so we developed some expertise in getting the bits out! Someone suggested thread forming taps. They were imported from Germany, and they worked a treat, but they were very, very expensive. Taps would typically last 30 to 40 threads from memory.

cheers

Bill Pudney

Edited By Bill Pudney on 07/10/2011 04:03:51