Mar 2016

The March Meeting

steel. A lot of the older UK based model designs (including my Sealion) refer to these numbers. This was superseded by the BS series and in the steels reference chart Bruce posted on our website, EN/BS equivalents are given. Apparently the BS series has now been superseded by the BS EN series. From what I can make out this is really to fall in line with some European standards.

I have been involved in various aspects of machine and equipment design over the years and one of the more difficult parts has been knowing what grade of steel is best for a particular application. In the early days, steel manufacturers worked with engineering companies to develop grades that were suited to particular purposes, then, standards institutions tried to formalize this with some kind of numbering system. The reality is that if you have been in a particular area of engineering for some time you settle on a range of grades for different components based on experience and input from metallurgical experts. If you are breaking new ground in equipment or machine design significant homework is required to select the best grades.

Fortunately, in model engineering, because things are fairly non critical, for the most part one can get away with a very limited range of steels. Perhaps what we should do is to have a discussion next time about what people commonly use and I will summarize this in the newsletter

Under the "miscellaneous" heading; Brian Lawson talked about getting 3 large prints of drawings made for $10 at the Commercial Copy Centre in Chatham. I have had large prints made at Huron Blueprinting & Reprographics in Sarnia but my recollection is that the cost was significantly higher.

Someone talked about ultrasonic cleaners; they do a good job cleaning small parts but are normally quite expensive. Apparently, one is now available for ~$40 that is designed to clean dentures. (One does start to think of some unfortunate mix-up scenarios here with items that are in for cleaning.)

and 4 holes in the boss it attaches to, but, to have those on one component angularly displaced by appropriate amounts so that depending on which pair of holes are used, the timing can be set in increments of a ¼ of the tooth angle. (Keeping the math simple, if the wheel had 36 teeth, then the coarse adjustment would provide 100 increments. The arrangement described would provide 2.50 increments.)

Mikes Mastiff

This is a valve and the adjustable tappet arrangement.

Show and Tell

Mike Clark is rolling right along with his 4 cylinder Mastiff. The major parts have now been made and the assembly of components is shown in the picture. The piston rings have yet to be fitted and there is an issue with the valve springs – the ones that came with the kit are too short. There is an interesting system for timing the camshaft: If the gears are fixed to the shafts, the timing can be set approximately by engaging the appropriate teeth on the pinion and wheel. However this does not provide sufficient accuracy. The arrangement used to provide a finer adjustment is to have 4 holes in the large timing gear

Don Eastman has been working on the model he is making of the equipment at the Petrolia Discovery. This is a large wooden wheel:

And this is a picture of one of his pictures showing more of what he has made.

I have managed to finish a few more parts for my Sealion. Both the connecting rods and pistons have now been machined from solid on the CNC mill. The rods were from 6061 and the pistons from 2024. These were probably the most challenging and interesting parts I have programmed for machining on the mill. I did start with some dummy versions of both to check the programing and make any changes necessary before machining the actual parts.

Mike and I are essentially at the same stage with our engines but mine still requires a train of 4 gears to drive the overhead cam and that is now in the works. The photograph below shows the crankshaft, pistons, wrist pins, connecting rods and head c/w valve gear. I also made a device with a very thin sleeve to help fit the rings on the pistons and a split, ring compressor to facilitate getting the rings to enter the cylinder bores.