Nov. 2018

The November Meeting

We usually start with the Treasurer’s report but Nick has sustained an injury and was unable to attend the meeting. (I think we can safely assume there is still some money left in the bank.)

appeared in the Jan 1953 edition and here are a couple of pictures:

Let me start by apologising for the late distribution of the e-mail version of the last newsletter. I try to get it out the Wednesday before the meeting – essentially soon enough to remind everyone about the meeting but not too soon that people forget. I had the newsletter ready on time, composed the accompanying e-mail, attached the file and hit “Send”. I checked that it went to the “Sent” box, saw it was there - job done. However, on the morning of the meeting Bruce called to ask about the newsletter because he had not received it, as it turned out neither had anyone else. We suspected that my e-mail provider had put a limit on the size of the mailing list one can use and this had caused the problem. I therefore split the list in two and tried again. This time the two e-mails went through. I did call my provider and did not got a get a very satisfactory response but it does appear that they have recently put a limit of 20 on the size of the mailing list one can use. Its just a pity that they did not inform their customers about this or provide a warning when an e-mail does not actually go through.

There was some further discussion about the costs we are now incurring for use of the meeting room at the school. (Detailed costs were set out in the last newsletter.) Assuming the school board does not further increase fees, annual member subscriptions should cover this particular cost. However, we do need to keep an eye on other outgoings. One item discussed was our subscription to Model Engineering Workshop and whether we should continue with this. Keith Orr informed us that it costs ~$100 for the 13 issues we receive each year. The subscription does not have to be renewed until next March so we have some time to decide whether to continue.

Last month, Bruce talked about an article in Popular Mechanics on a reversible tapping head. However, when he went to look for the information so that I could put in the last newsletter, he could not find the article. But now he has, so here are the details: It

making artillery pieces that were around at that time and there has been lots of television coverage featuring what went on including new aspects that are coming to light. One program I was watching discussed the poor quality of the ammunition delivered to the front, particularly that used by the artillery. It was a British based program and I am not sure whether the figures relate to shells manufactured in Britain or whether it was across the board but apparently between 40 and 90% failed to explode when they reached their destination. This explains the huge numbers of un-exploded shells that continue to be found and maybe Haig’s over optimistic assumptions around his artillery’s effectiveness at the Somme. However, it really makes one wonder about what was going on in the munitions plants or with the design and manufacturing technology. One thing that comes to mind is that the old British pub licencing hours were introduced during WWI: These limited the opening times to a couple of hours during the middle of the day and the intent was to get workers out of the pubs and back into the factories to make a few more shells etc. in the afternoon. One wonders whether the 40% failure applied to the shells made in the morning and the 90% to those made in the afternoon!

Show and Tell

One can easily see how it works but a comment made last time was; “how do you make sure the tap goes in square to the surface of the workpiece?”

This week Bruce talked about some videos from Joe “Pi“ which are really about making a cannon barrel but start by discussing how to make the form tools needed to produce the fancy shapes that are traditional on these items.

https://www.youtube.com/watch?v=I_Tr1hlPzB0

https://www.youtube.com/watch?v=N3-XFfc82ew

Since the meeting was the day after the hundredth anniversary of the end of the first world war there was some discussion about that sad event in human history. Martin Beales has a soldier’s helmet from the time but is looking for a new liner because the original leather one has disintegrated. Bruce, of course is into

Offsetting the input shaft by the (mean) helix angle of the thread used for the worm not only allows the wheel part to be cut with straight teeth, it also brings the shaft with the hand wheel a little further away from the barrel supports.

Tony Koolen is back working on his Case traction engine. This time he brought along the boiler feed pump that he cast originally and is now in the process of machining.

I have managed to get back to doing something on my Sealion. Before activities ceased at the start of the summer, I had completed most of the design and CNC programing for a manifold to go at the back of the engine. This is to feed oil to the rocker shaft then drain it back to the crankcase afterwards. Also, to take the water from the far end of the head and send it back towards the front to where the radiator will be. Westbury leaves these provisions to the imagination of the person making the engine, nothing is shown on the drawings.

Having written a CNC program, the first step for me is to “dry” run it using Mach3 loaded on to my laptop. This is the “armchair engineering” part and gets rid of the silly errors. Before making the part in metal my usual approach it to try out the program on a piece of wood (machinable wax would be even better) because it is less frustrating to mess up on a piece of wood etc. than the real workpiece. As a preliminary to this I usually do some “air cuts” with the cutter above the workpiece, to make sure things look right.

The item I brought to the meeting was the piece of wood used to test the programing. It along with the finished item (in aluminum) are shown below: