Member postings for Bill Pudney

Some hours later I have just realised that I had "hydrodynamic", "homogenises" and "aesthetics" all in the same sentence. Obviously I was sleepwalking and snacking on a thesaurus.

apologetically

Bill

The epoxy compound is only used below the waterline. It is purely functional, it reduces hydrodynamic drag and it reduces and homogenises hull generated noise, aesthetics are not a factor.

Attempting to predict the ultimate shape of the hull and rolling the shell plating so that welding induced distortion is eliminated would probably be theoretically possible but almost certainly outside any cost budget.

It wasn't only the non slip floor coatings that burned and gave off toxic fumes, it was mattresses, bedding, even the sailors clothing was polyester so it burned and melted onto the skin. Horrible.

Performance of a modern warship can be fairly spectacular. Again I was told by someone who would know that HMS Broadsword would accelerate from 0 to 30mph faster than a sports car. I always assumed this was an MG Midget type sports car, not a 7 litre AC Cobra type of sports car!! Certainly being on a launch alongside when she did a standing start sprint, was very impressive.

cheers

Bill

Modern destroyers should not be confused with destroyers of a bye gone age. For instance a modern T45 destroyer displaces over 7,000 tonnes and are about 500' stem to stern. An early "V" class destroyer laid down in 1916 was about 1190 tons and 300 feet long. To provide an effective escort for the modern fast battleships in WW2 the "L" and "M" class were built. They displaced around 2,000 tons and were 360 feet stem to stern.

Even HMS Queen Elizabeth had visible between frame and longitudinal panel warping at the time of her launch

cheers

Bill

Pauls addition is interesting and provides an alternative perspective.

One of the reasons that weight is important is the increase in electronics and cabling in modern ships. An attempt to reduce "top weight" by the use of light alloy superstructure proved to be a dead end. The T21 class frigates had light alloy everything above the weatherdeck, and it was realised fairly early on when the first of class (Amazon) had a fire when fitting out, the al. alloy structure just burn't away. Sadly this came home to roost in the Falklands. The superstructure of later ships, is of fairly light gauge steel. Interestingly (well I thought so!!) the paint scheme is very important to prevent rust. It's not just a case of slapping on another coat of battleship grey!

I was only involved with two classes of ship, T21 and T22. They both used constant frame and longitudinal spacing (36" x 24" for T21 and 600mm x 1000mm for T22). The variations required to comply with longitudinal strength were achieved by varying the shell thickness as required.

cheers

Bill

Its caused by the welding on the 'inside" of the shell. There are frames and/or bulkheads at approximately 1 metre intervals along the length of the hull, and longitudinals at approximately every 600mm going from the sharp end to the blunt end. These cause "panels" all over the external surface of the ship. When the welding happens the "panels"are pulled in by the action of the welding, causing the distortion mentioned. The distortion varies but can be up to about 10mm. The welding of the frames and longitudinals to the ships shell (the outer plating visble from the outside of the ship, is continuous. Shell plating thickness varies considerably from a maximum at the deck edge and the "turn of the bilge" amidships to a minimum towards the bow and stern. I was told by someone who would know that about seven tonnes of epoxy filler is used to smooth out the hull on your average frigate, this improves performance and reduces the hull generated noise.

Ady1 is right about the weight, considerable care is taken to ensure that weight is minimised. Not to sure about the "...big speedboats with guns", though!!

Hope this helps

cheers

Bill

For an Australian perspective, Ausee Tools are good, as are LPG Toolmakers, Eccentric Engineering & E.J. Winter. RS Australia are surprising, free shipping!! CTC Tooling in Hong Kong have been excellent, their delivery times have improved recently as well.

In Adelaide most of my metal comes from either Surman Metals for cast iron and gunmetal or Bohler Uddeholm for specific grades of steel

My "go to" UK shops are Arc Euro, I don't know what they've done to their freight people but 4 days from UK to Australia is pretty spectacular!! Drill Service do top class stuff. Tracy Tools are excellent. I was disappointed to find that Cutwel Tools do not supply to Australia.

Finally the USA .....Little Machine Shop is good, MariTool are top quality suppliers of top quality cutters

Cheers

Bill

To prevent corrosion and enable better adhesive efficiency, consider anodising all the aluminium parts before gluing. It makes a world of difference.

cheers

Bill

Agree with most of the above. In addition if you are using an epoxy based adhesive ,it would be good to clamp the joint whilst the adhesive is curing, and leave in a warm dry place for the recommended cure time. In general long cure adhesives have better properties than slow cure.

cheers

Bill

Sorry I mean't to say the single cylinder one, not the V8!! The V8 was certainly an amazing design, but for me the single is so beautiful!!

cheers again

Bill

I read The Book in the mid 70s, it seemed appropriate at the time. I am a technical person and have been all my life, I also understand the need for beautiful things, and beautiful design. F'instance, for me a 1957 Grand Prix Moto Guzzi 500cc is just about the epitome of pragmatic, elegant design. Of course there are examples wherever you look, but for me that 'Guzzi is perfect!!

cheers

Bill

Cannot recommend the use of sharp cutters and some sort of fluid enough. My preference is for paraffin/kero on al alloy. WD40 is ok but leaves a waxy finish in the overspray areas. Fantastic for displacing water though!! Kero is probably cheaper as well.

cheers

Bill

Big end bolts and nuts. Mike Pooles comments about replacing them is right on the money. They are generally the most highly specified part in a motor. Material, heat treatment, surface finish, tolerance regime, post manufacture handling and storage etc etc

Socket head screws, "name" manufacturers like Unbrako, Holo Chrome etc are manufactured to very high specs and their fasteners are of uniformly high and reliable standards. Personally I wouldn't trust non branded fasteners as far as I could spit.

cheers

Bill

Google "Unbrako" and you can download the Unbrako Catalogue/Engineering Guide with more information than you will ever need to know about socket head fasteners.

cheers

Bill

Not a CNC failure, butttt.....Many, many years ago, there was a large grinder, it had a vertical axis cylindrical wheel about 24" diameter, the bed of the machine was about 20 feet long. The machine had a rapid traverse that was pretty quick. I was in an adjacent workshop, and wasn't involved, other than as a witness, fortunately. The experienced operator was setting the machine up and as a result had the guards off or down, the workpiece (apparently) wasn't clamped down, it was a piece of steel about 20" diameter and 2 or three inches thick. Anyway, the operator was just checking the coolant flow, with the bed at an extreme of travel, i.e. right uo one end, when the bed traversed at high speed, flinging the workpiece the full length of the workshop, about 50 or 60 feet, it started at about 5' off the ground, and finished about 2'. It flew down the walkway, between workbenches and missed the nine or ten people working at those benches, and impaled itself in the brick wall. Several people lost their lunch. Rapidly made me realise how dangerous working for a living could be!!

cheers

Bill

Hi Tug, Thanks for the kind comments!! The motor with the composite piston is a PAW 15 TBR CT....that's 2.5cc, Twin Ball Race, Combat Tuned. It's one of two motors that I bought in about 2005 when I intended to use them in Vintage Combat. It turned out that I was too old and slow for Vintage Combat, but finding that out took several attempts and the motor in question was buried in the sand that is our flying field. As a result of which the piston was damaged, requiring replacement.

I still haven't built a model for the Sugden, but it's likely to be a Mercury New Junior Monitor.

cheers

Bill

hello Tug and NDIY

The part of the piston that is in contact with the cylinder is from cast Iron. The shape is like a bean can with one end open. The closed end is the crown of the piston, and is about (from memory) 1.2mm thick, the cylindrical part is about 0.8mm wall thickness.

What I described as the carrier is a bit of 2024 T3 al. alloy, made so that it is a smooth and snug fit up inside the piston, to a positive stop when fully home. This seemed to be important to keep the gudgeon pin at about the right height. Bearing in mind that the bore is under 15mm, it will be appreciated that the carrier is fairly small. From memory it was drilled through about 6mm dia, the gudgeon pin was cut from a 4mm diameter needle roller and carefully reduced in length until it would fit in the piston. No especial grooves or other keying devices were used, I just didn't try for a super smooth finish on the inside of the piston, and outside of the carrier.

I claim no originality as this method was used on the first ETA 15 back in the early 60s, if not others. In fact it was reassembling my ETA 15 that gave me the idea, for my motor. Yes Tug, if there are any problems, there is no way other than destructive diassembly, but the advantages of a captive, floating gudgeon pin outweigh that (minor) problem in my opinion. Interestingly the weight of the composite piston, gudgeon pin and conrod is marginally less than the weight of the original piston/pin/conrod, from memory about 0.5 of a gram.  So not enough to get really excited about, but worthwhile.

The motor has been flown a fair bit, initially in a CL Peacemaker, which it dragged around quite impressively on 60' lines. I too wondered about it all falling apart, but thinking about it I realised that the JB Weld was always in compression, I stopped worrying about it then!!

cheers

Bill

Edited By Bill Pudney on 17/03/2021 09:34:38

Edited By Bill Pudney on 17/03/2021 09:37:33

Probably ten or eleven years ago I had to make a new piston for a 2.5cc compression ignition engine. At the time the simplest solution was to make the cast iron piston like a tin with one end removed, make a carrier for the gudgeon pin and glue the whole thing together. The I did a bit of research on high temperature epoxies, as the underneath of a piston in a high revving (15,000 rpm plus) engine would be likely to get fairly hot. JB Weld seemed like it was the best candidate. So very carefully everything was cleaned, and cleaned again, the conrod was assembled into the al.alloy carrier with the gudgeon pin. The JB Weld was VERY carefully applied, the conrod, pin, carrier was assembled, and left in a warm place for a day to cure. The motor was carefully assembled and the new piston run in. Ten or eleven years later this motor after a lot of use is one of my favourites, it starts from cold in one or two flicks, and revs to well over 15,000rpm.....Thanks to JB Weld!!

cheers

Bill

When my "chariot a vis" (ref albums) was underway, there was a huge amount of mess very quickly as all the big parts were cast iron. A sheet of thin polycarbonate from the local friendly hardware shop was cut up as required and clipped to anything close using bulldog clips. It contained most of the mess, was very cheap, fairly effective. Don't over think it!!

cheers

Bill

Excellent, so basically we are all on the same book if not the same page!!

cheers

Bill

NDIY, maybe you were in such a hurry you obviously missed my ...." although there are larger ones ". These larger ones are only available from a few suppliers. My point was that the largest normally available collet is nominally 20mm diameter.

I don't consider anything wrong with my Clarkson Autolock. My preference is for the ER32. If your preference is for the Autolock then clearly that's your choice and good for you.

cheers

Bill