Here is a list of all the postings JA has made in our forums. Click on a thread name to jump to the thread.
|Thread: Small Metric Screws|
Many thanks for the replies - nothing has changed.
I re-opened the tread because I have started designing a model steam engine. I decided it should be metric including fixtures. Tubal Cain, in his Model Engineer's Handbook, reports that this was discussed in 1981 and the BSI published a document Guidance on Metric Screw Threads and Fasteners for Use by Model Engineers, PD6507-1982. I have not seen this and I doubt if anyone else has (a copy costs over £100). Soon I have to make up my mind whether to stick to BA or take the plunge and go to metric.
I think, as JasonB suggests, this has serious implications for our hobby.
Obviously there is little point in converting most models to metric since they are only made by the experienced. However the opposite is true for entry kits such as some Stuart models. To be presented with the drawing for a Stuart 7A can be quite a shock for someone who has only known metric units etc. I know from experience since my niece decided to make a Stuart 7A while in six form (the school had, probably still has, a well equipped workshop) fifteen years ago. With the help of her teacher all the dimensions were converted to mm but problems arose when it came to drill sizes. Neither of them had any idea about number drills and the usual shops (local, Axminster Tools) could not help. So uncle was phoned.
Perhaps someone should buy a popular Stuart model and try building it, with a blog, as a complete metric model with dimensions based on mm and not converted from fractions of an inch and with metric fixtures. Just a thought for the future of our hobby.
I do not apologise for resurrecting this very old thread.
Has any progress been made in the model engineering fraternity, users and suppliers, about metric fixings? We seem to be the last to use odd BA sizes and I am sure all BA sizes will go.
|Thread: Aero Fuel|
It is difficult to think of what else an aircraft piston engine would run on. In addition to the above reasons, petrol was a relative safe fuel that people were familiar with.
The only alternative I can think of is a lighter, more volatile, "petrol" that would make starting easier in cold climates. The Russians could have used such a fuel. Their general jet engine fuel is more volatile than aviation kerosene for this reason. In the very early days of the petrol engine more volatile fuel was used with surface carburettors.
One must add that diesel aircraft engines were also used during the War.
|Thread: Water in fuel|
I think the latest postings are slowly drifting off subject again but I have been dying to write something.
AVGAS went up to an octane rating of 130. All the piston aircraft engines used by the British and Americans in the War were designed and initially developed before the War. These engines were either naturally aspirated or had a very low boost pressures. The compression ratio was usually about 7:1 and the octane rating of the fuel was 100 or lower. As the War progressed fuels with higher octane ratings allowed the boost pressure to be increased resulting in very large increases in power with no change in compression ratio.
One little question: How do you dispose of waste fuel responsibly?
Edited By JA on 27/09/2019 20:22:57
Thank you. I have been trying to prevent myself from posting something on water injection.
Major problem with fuels is that the refiners and distributors do not have to tell you what is in the fuel. This includes additives. All the fuel has to do is to meet the specification.
About 12 years ago there were a spate of cases where a fuel additive was destroying an engine sensor and thus engines. I think the fuel suppliers legally hid behind the fact that their fuel met the specifications.
There are firms out there, such as Carless, who will blend a fuel to your specification. We used them at work. Obviously they will not put in banned additives such as tetra-ethyl lead and they will only deliver in bulk. You will have to be able to store it legally and pay tax (VAT and vehicle fuel duty).
Addition - I am sorry to say Vic is probably right. They know who you are - You don't pay road tax and your vehicle does not need an MOT.
Edited By JA on 26/09/2019 14:00:06
|Thread: citric acid|
If it just citric acid I guess you pour it down the sink.
My pickling acid, made from powder bought from CuP Alloys, is now a nice green colour since used acid is returned to bottle. I guess the green is copper citrate. I would think the powder I bought contained a biocide since I never had anything grow in the liquid.
I would guess it is a fungus or some form of lower life. These can turn up in unexpected places such as in petrol and aviation fuel.
Why don't you just try using your citric acid. It will either work or not work. What ever it is will not eat your copper.
Fungi are more likely to be killed by copper than citric acid.
Edited By JA on 23/09/2019 19:05:47
|Thread: Drill running off course|
You are not alone.
I have experienced a drill running off course with bronze. The drill diameter (all this is from memory) was about 5mm and after a depth of about 35mm the drill was around 2mm off course. The drill was good and dressed to cut bronze. The drilling was done in a lathe and started from a centre drilled hole. The Jacobs chuck was not removed between the use of the two drills. The tail stock alignment is within 0.001". The speed may have been slightly slow. Neat cutting oil would have been used. The bronze was phosphor-bronze bar.
As far as my "lesson learnt log" - this is to be expected when drilling bronzes.
I would ask questions about the bronze bar, like do you really expect it to be perfectly homogeneous?
|Thread: drillling bronze|
The real problem with a wandering drill is that you do not know it is happening.
I have drilled quite a bit of bronze from cast gun metal to phosphor bronze. I have always used a drill with zero rake, as for brass. I drill at speeds lower than brass and always with a neat cutting oil. I do occasionally get a drill that snatches and have had drills wander badly in deep holes.
|Thread: Are there any left?|
Pride and Clark - everybody got ripped off by them. I part exchanged a dynamo with them once. Years later I took it to a respected parts dealer who could not quite understand what he was looking at. They even did the manufactures. When a company was facing cash flow problems they would quickly take a batch of new bikes down to Pride and Clark and get some, a little, money to pay the workers. I think I have a P&C Matchless, a C registered 500c single.
|Thread: Screaming brass|
Many thanks for the comments.
As already stated I do not have a problem machining brass. It is easy and the finish is good to excellent. It is just the noise.
When I have a spare moment on the lathe (not in the next few days) I will put a 1" diameter bar in my biggest four jaw chuck and take a number of 0.030" deep cuts using my existing tool (left hand knife with about 5 degrees of top rake) and a similar zero degree top rake tool at various speeds and tool overhang. Photographs of the finish will be taken and I will report back.
I don't really want to spend time on this since it is not a problem!
Nigel, thanks for the offer but I am just outside Bristol.
Edited By JA on 05/09/2019 17:26:36
What grades of brass do you use?
I have always expected brass to squeal or scream irrespective of the lathe. However I am beginning to realise most of my experience is with CZ.121 bar (leaded free cutting brass).
I accept that. I am cutting it.
I use a very slight positive rake. This cuts well and cleanly.
Edited By JA on 04/09/2019 22:37:24
|Thread: Brazing torch|
I have used both and would recommend the 3488. It is far more convenient.
One comment: When fixing the supply tube to the torch, either torch, use spanners on both nuts. If you hold the torch and just use a spanner on the tube nut you are likely to twist the pipe inside the torch. Eventually it will fracture leading to propane leaking into the body of the torch. Fortunately I was not burnt when the inevitable happened.
|Thread: Screaming brass|
Just a simple question - When turning brass, why does it scream?
I apologise if this has been asked before.
|Thread: M4 x 0.75mm pitch CSk machine screws|
This is not a standard size. M4 x 0,70 is Metric Coarse.
|Thread: Your ideal holiday|
Venice, Melbourne, Vancouver and San Fransisco. No other cities are worth it! Not that I have visited all of them.
The Lizard is OK, Lowestoft Ness is just a beach, I gave Dunnet Head a miss. The Ardnamurchan, including the point, is really worth the journey. The area is truly remote with stunning scenery.
To escape life, which is why I go on holiday, nothing beats Islay. At any time of the year.
|Thread: Are there any left?|
It is a long time ago and one’s memory can play tricks.
I think Proops were in Holborn in around 1963. They were not there in 1960 and had moved on by 1966. So had Bassick Lowke. By 1963 Proops had left the disposal market and was more like the business it is now.
I was once a Londoner and remember the shops and area (parts were dodgy).
Bassett Lowke had their shop at the west end of Holborn and I think Proops were next door. In the early 1960s the government disposal shops were split between Tottenham Court Road and Lisle/Little Newport Streets. The latter streets were infamous, the only businesses present were the disposal shops and brothels. The biggest building in Lisle Street was the London Hospital for Skin Diseases. By 1966, when I left London, the disposal shops had left Soho and later the Tottenham Court Road shops went into the HiFi market.
Occasionally I would return and by 1971 nothing was left.
Just a comment, the goods stuff like HRO receivers sold for a lot of money.
Edited By JA on 21/08/2019 14:23:17
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