Mar 2020

extraordinary lengths to steal them. It just goes to

show what a thieving bunch the Brits are!

https://getpocket.com/explore/item/the-great-modeltrain-

robbery

As discussed at the February meeting, I said that I

would put on a demonstration on 2D drafting – so that

is what I did. I used both the older AutoCad 2000

program and the more recent AutoCad 13. (For what

we do, the 2000 version is really quite adequate.)

The problem is that neither it nor version 13 will run

on the later Microsoft operating systems. They were

OK up the Windows 8 stage but that is all.

Fortunately, there is a convertor from Longbow that

allows them to be loaded into and operate in Windows

10. The older AutoCad versions are fairly readily

available.

I have used AutoCad for over 20 years, initially for

work but now entirely for the hobby. If you are

making something from scratch then you need to

make drawings of some kind and you either have to

do this with pencil and paper or learn an electronic

system. Even if you buy a set of castings and

drawings, experience with my last two projects is that

you really cannot make the thing with the drawings

supplied. In some cases, the castings cannot be

machined to the finished dimensions specified, in

other cases there are errors in the drawings so that

things cannot actually be made as drawn and go

together afterwards. With my Sealion I have basically

had to re-draw the whole thing.

In addition to the straightforward drawing part, these

programs allow you to get various properties of the

items you have drawn. For example, when I was

making my single cylinder Wyvern engine, one of the

write-ups I saw suggested that the crankshaft balance

weight was inadequate. I made the piston and

connecting rod first, determined their weights then

worked on re-designing the crank webs to give the

“correct” balance. Drawing programs have a

“properties” function whereby once a component has

been drawn (in 2D in this case), one can find its area

and the centre of gravity. From the area, thickness

and material density, the weight can be calculated,

then given the centre of gravity, the balance moment

This was the second valve body he has made, he

found that the first one had a blow hole at a critical

point and it had to be scrapped.

Melting iron is hard on crucibles – as the picture

below shows:

The next items were the main governor piece and the

valve body for the governor:

Tony also brought along the steering shaft for his

traction engine. I milled the (variable angle) helical

grooves on this some time ago using my CNC mill,

Tony has now added an end piece.

Bruce continues to make progress on his howitzer –

despite the setbacks mentioned earlier. Below are

some pictures of the artillery piece showing the status

as of the meeting

side. I built an electronic system that uses a Hall

effect device triggered by a slotted disk on the

crankshaft. This operates a high voltage switching

transistor that does essentially the same job as

contact breaker points did in days of old. The Hall

effect device + switching transistor is the technology

used in cars etc. nowadays but they have a computer

in between to calculate optimum spark timing.

The first problem was that the Hall effect device was

mounted on the engine with all the connections

carefully insulated. This was then connected to the

rest of the ignition system comprising the switching

module, battery and coil. The only other connection

from the ignition system to the engine was the hightension

supply to the distributor/spark plugs.

Everything worked OK for a while but what must have

happened was that the current flowing through the

high-tension system built up a charge on the engine.

When the voltage associated with the charge reached

a high enough value, the insulation around the Hall

effect device broke down and it was zapped.

The solution was ordering a replacement from Digi-

Key and putting in a grounding connection between

the engine and the ignition module - which had I

thought about it properly I would have done in the first

place. (That was my dumb arse moment.)

The other problem was more difficult to find. When I

was assembling the engine, I made up something to

mount the spark plugs so that I could check that they

all worked and fired in the correct sequence. I had

already checked that the timing was right, so

everything in the ignition system looked good.

The engine is mounted in my old lathe so that I can

turn it over continuously whether or not it is producing

any power. Rotated like this it would fire sporadically

and in a somewhat strange way but not actually run. I

won’t describe how I eventually figured out what was

happening but basically, when you have to create a

spark in a cylinder that is under pressure, a

significantly higher voltage is needed than at

atmospheric pressure. There is not much space

inside these small distributors for the rotor arm and

the contacts for the four spark plugs and what was in

fact happening was that the high voltage from the coil

was arcing across to a contact for one of the other

spark plugs (in a cylinder where there was no

pressure) hence finding an easier passage to ground

than through the spark plug which was under

pressure and that actually needed to be fired.

I made a slight modification to the distributor and now

it runs fairly well. It does not run as evenly as I would

like and I suspect that I still have the same problem

but to a lesser degree.

This is the engine on its lathe bed test stand, using

my traditional fruit juice can for the cooling water.

I once described him as the ever-productive Mike

Clark. He certainly lived up to that billing this time

bringing along the Celebration Ball Clock that he

recently completed.

The timekeeping part isclockwork with an escapement wheel and pendulumarrangement that is different from most. You tell thetime by looking at the number of balls in the lowerrack (1 to 12 hours) and the minutes using thenumber of balls in the top rack (5 to 55.) You only get

the time to the nearest 5 minutes - not microsecond

precision here! If you Google the subject quite a lot

comes up including a video of one working. It also

seems that a lot of these have been made from wood,

Mike’s is primarily aluminum.

I have been working fairly intensively on my Sealion

to get it up and running. (This is my main excuse for

not getting the newsletter out earlier.) I was aiming to

have it running for NAMES this year and although that

target has now disappeared, I still wanted to get it

finished.

Although there have not been any real mechanical

issues, I have had some problems on the ignition

The Rest of the Season

Although I have left the scheduled meeting dates

below there is obviously a question mark over

whether we will be able to hold any of them. I have

had official notification that the April booking for the

school has been cancelled and it is likely that May will

be as well. Because there will be no meeting in April

there is not much point in producing a newsletter

either…unless…being confined to home, everyone

has been beavering away in their shops and have

pictures and write-ups of all the items they have made

...that they can send to me so that I can put

something together!?

Scheduled Meetings dates for 2020

These were to have been as follows:

April 20th, 2020 – definitely cancelled

May 11th, 2020 – still questionable

June 8th, 2020 – we will see?

Our Website

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

John Lovegrove