Jan. 2020

particular part was not critical. Valves need to be made out of some fairly tough steel and the finish on the stem needs to be good. The alternative technique involves cutting short sections at a time (say ¼” long,) taking several cuts to get to depth, leaving ~0.005” for a finishing cut, measuring, then making a final cut to (hopefully) get the diameter required. I used this technique for the 8 valves on my Sealion but also put a centre in the outer end to support this while I did a final grinding operation. (You really need to be thinking in terms of a few tenths tolerance for the valves to operate nicely.)

Another of his favourites in Mr. Crispin. The following is about measuring difficult angles and diameters

https://www.youtube.com/watch?v=3ngGV10sRl4

Bruce has been making parts for his Howitzer using 416 stainless steel. This machines beautifully but when it comes to soldering parts together it is another story. Just assembling the parts, dosing with flux, heating and applying solder is not sufficient. Basically, what you have to do is to “tin” the mating parts first, then everything works out OK.

Most of us were brought up with Meccano sets and maybe that is why some of us ended up in the world of engineering. Apparently, it is still available and quite popular. There is a very worthwhile history set out in Wikipedia and the origins go back to 1898. The inventor was Frank Hornsby who lived in Liverpool, England and started the manufacture there. In fact, I remember the stuff I had as a kid was made in Liverpool. Anyway, after a series of takeovers etc. the parts are no longer manufactured in Liverpool (very little is) and not even in the UK. A Canadian company, Spin Master, currently has the rights to the brand but whether parts are actually made here is not clear. One thing that has not changed is the hole spacing on the metal strips etc., it is still ½” and the bolts are still 5/32” BSW - probably the only place where that thread is still used. (For Bruce’s benefit, I am sure M4 bolts would work just as well, they are almost exactly the same size!)

https://en.wikipedia.org/wiki/Meccano

There was discussion about a kid in the US who had tried different things to increase the life of hearing aid

manufacturers have chosen a compromise that makes the drills less susceptible to shattering but not as long lasting as they might be.

https://www.youtube.com/watch?v=hAxi5YXTjEk

Show and Tell

Todd Michael brought in some more of the items he has been working with to produce iron castings for his traction engine. The picture below shows the core box halves used to make the core needed to form the steam passages in the balanced-valve operated by the governor.

Another subject of discussion was cryogenic hardening. Again, I thought I would do some research into this and the website below is quite interesting. Trying to summarize what is being said; the hardening process for steel involves generating a very hard, martensitic phase in the material. The tempering process then converts some of this to a softer phase to give the right balance of hardness and ductility so that the tool is hard enough to cut effectively but not so brittle that it shatters readily. The cryogenic hardening process involves exposing the tools (in this case conventionally hardened drill bits) to liquid nitrogen at ~-2000C for 20 – 30 hours and the effect is to increase the amount of the hard martensite present. In the video he describes all of this and subsequent tests carried out comparing drills that have been treated and others that have not. Using fairly aggressive drilling conditions the treated drills last at least twice as long as untreated ones -which sounds impressive. The middle section of the video is not particularly useful but at the end he makes some interesting remarks; mainly that what one is likely doing is just shifting the hardness/ductility balance more towards the hardness end. Also, that these cryogenically hardened drills are not coming from recognized manufacturers. The implication is that you could get the same thing by adjusting conventional hardening techniques but most

The next photograph shows the cast valve body and the pattern used. (The projections from the flanges form the core “prints” for the core mentioned above.)

The last ones are for the match plates used to make the mould for the governor body.

Bruce continues to make progress with his 4½” howitzer. Earlier he described the problems he had soldering parts together, below is picture of the assembled breech end and breech block.

Meetings dates for 2020

These will be as follows:

February 10th, 2020

March 9th, 2020

April 20th, 2020

May 11th, 2020

June 8th, 2020

Our Website

https://sites.google.com/site/bluewatermes/

John Lovegrove

I did manage to get a few more parts made for my Sealion. What remains now is to take everything apart, deepen the tappings for the head bolts, then carefully assemble everything with suitable sealants, making a few adjustments along the way. Although I have carried out some breaking-in of the bottom half (pistons/cylinders, connecting rods/crankshaft) by external power, I anticipate that a lot more will be needed before the engine runs freely. I have a set-up on my old lathe that allows me to turn the engine over using a slender wooden drive shaft from the headstock. The thinking is that if something seizes the wood will break and avoid serious damage to the engine.

Possible Subjects for Following Meetings

Bruce and I have discussed what might be done to give a little more “content” to our meetings. One of the things both of us are into is Computer Aided Design (CAD.) The professional world adapted this several decades ago and the model engineering world now makes extensive use of it as well.

If there is sufficient interest Bruce and I are prepared to give some demos on how 2D and 3D systems work. Perhaps we could discuss at the February meeting to assess just how worthwhile this would be.