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Member postings for DiodeDick

Here is a list of all the postings DiodeDick has made in our forums. Click on a thread name to jump to the thread.

Thread: High Speed Bench Drill?
21/05/2022 23:03:40

It was home made, along with a Wal Philips injector and a Mag-dyno, many years ago when you could build a Bonnie from the floor sweepings after the auto jumble traders had packed up and gone home.

The Amal carb piece was inspired by something similar in the Science Museum collection, the others just followed.

The Mag-dyno has a crank handle and would fire a spark plug.


23/04/2022 23:21:50

There are some jobs that need a high speed. The twist grip lock barrel in the attached pic was/is secured by 2 x 1/16" pins from the inside. Tried to drill them out with regular drill press and the bit wandered off and started to chew the Mazak casting. The Meddings precision drill put the bit straight down the middle.

DickAmal carb

Thread: Buy a book or download free
03/03/2022 22:57:39

In a forum thread re-locknuts, December 2012, I suggested that marine engine builders look for Sothern's "Verbal notes and sketches". Michael Gilligan added a link to an edition available for free download. This was useful as print copies seem to be getting scarcer, but the real benefit to engine builders is in the (sometimes) large fold-out plates. From my experience of downloads, these are either missing or reduced too much to be usable.

Generally, I do not download from an iffy source when a hard copy can be bought. In my view that is too close to "Stealing by Finding" which is a seldom-prosecuted offence in Scotland, but if the only way to get a copy of "Le Genie Civil" from 1886 is to download it from The French national library, then presumably that is what it was put there for.


Thread: Santander on-line banking
25/02/2022 19:21:15

I have received an invitation, allegedly from Santander, inviting me to confirm my login details, etc.

I do not do online banking and I have no account with Santander.

Gang warily,


Thread: Always confused over threads and tapping
21/02/2022 23:03:21

Neil Wyatt points out (above) that camera tripod threads were BSW, but are now UNC. The user guide for my JVC camcorder specifies the tripod thread as 6.35mm x 1.25p, with no mention of the thread form or angle.

A rose by any other name?


Thread: Motorbike gearbox fitted to a milling machine
07/02/2022 18:44:32

In the pre-war gearboxes I was familiar with, there was no oil seal, as such, between the sleeve gear (output) and the main shaft input, just a bush inside the sleeve gear bore. This was OK because the oil level was below the main shaft. There is usually a level plug on the gear box shell - this was often BSW thread as it screws into the alloy shell. Some had a hole through the the inner cover wall so that oil put in through the clutch lever. cover would find its way into the main box. A new sleeve gear bush would help, but if the box is noisy it may need more than that.


Thread: Electricity Supply - Fun with Statistics
05/02/2022 23:20:10

J. Hancock says that "sixty years ago nearly every large town/city had a complete infrastructure in place to provide electric powered transport. All affordable, convenient and pollution free".

The genesis of the electricity network that we know now was individual municipal corporations changing from horse-drawn to electric tramcars. There was no "grid" so they had to make their own electricity. The companies that supplied this kit usually over-estimated the power required (to allow for expansion of the tram system over time and to boost their sales in the short time) leaving the council with an excess of capacity, which they realised could be sold for domestic lighting, etc. The power stations were built near the centre of the tram system, which meant that many were built in the centre of town.They were invariably coal powered, with chain-grate stokers that struggled to reach 20% thermal efficiency, but as every house had its own open coal fire(s) nobody bothered about pollution. Battersea would have been one of the later and bigger examples.

The Tramways Act stipulated that tram systems had to be built and operated by companies independent of the councils, but could be bought out by a council after some years. This hindered investment no end. Why invest, only to get bought out before you had got your money back?

The council-owned transport was convenient, was apparently affordable (because some of the cost was hidden in the rates) but far from pollution free.

All this changed with the nationalisation of the electric companies after WW2. New, bigger, power stations were built out of town, a grid was built to connect them and Scotland embarked on the "Power from the Glens" programme.

And yes, I know about the steam powered trams widely used in the Midlands.They were coal-fired too.


Thread: Cowells 90ME 14x1.5 backplate question
30/01/2022 21:48:32

Yes, they were 14mm x 1.5p, but changed to 1mm pitch to enable the use of Unimat accessories. I bought a 14x 1.5p tap. Turned a backplate from round bar and fitted a Unimat 3 jaw to that. The end-mill holder in my photos uses a similar backplate for the same reason.


Thread: The demise of UK fossil fuel Power Stations
27/01/2022 22:38:55

Germany took fright at nuclear power after the reactor fire at Chernobyl in April 1896 and reverted to burning brown coal, sometimes known as lignite, which is indeed dirtier than our "black" coal.

Meanwhile, Western countries, including the UK, embarked on a Technical Assistance programme (Tassis), under the aegis of the International Atomic Energy Authority, sending scientists and engineers into former Soviet bloc countries to advise how to keep their reactors safe, principally because we did not want them burning lignite.

Germany's aversion to nuclear power did not prevent them from trying to muscle in to Tassis to sell their kit at Kozluduy in Bulgaria, which had Russian designed and built VVER reactors.


Thread: How to contact Model Engineering Website
19/01/2022 16:49:52

On the front page of the current "issue" if that is the term, just below the pic of a Triumph power unit there is a box with options - "ask a question" goes straight to his e-mail account.


Thread: Model Engineering Website
13/01/2022 22:03:32

It worked perfectly on my iPad 2 minutes ago

Thread: Engineering as Art
09/01/2022 23:10:48

Engineering as Art:

First define"art".

While there is undoubtedly a lot of skill in producing an engineering drawing "the old way" is that really art? I do not consider a manufacturing drawing to be "art". Some general arrangements (like the one of "Douro" by Harland and Wolff that I can see as I type) has the waterline shaded blue, bow and counter planked and coal bunkers also shaded. Although presented like that for the benefit of buyers who were, perhaps, not good with engineering drawings, it is a very nice picture to hang on the wall and could be considered "art".

The drawings in the ME article are not particularly good examples of engineering drawings - no tolerances for a start, too many items on one sheet, etc. , but nicely drawn.

The primary purpose of a drawing is get the necessary information across. The various standards strive to eliminate confusion by reducing the risk of mis-interpretation, but I would argue that certainty of the designer's intention is more important than pedantry.

Thread: Lock nuts / Jam nuts - MEW 311
07/01/2022 16:29:20

In proper engineering, "standard" bolts and studs go through clearance holes and do not resist shear, unless something moves to take up the clearance. Resisting shear is meant to be done by friction (produced by the clamping force) at the interface. The thought of a portal frame structure squirming under varying load as the connections shift to and fro is quite scary. And yes I do know about flexure under load and wind conditions, but that flexure is accommodated by stress, and consequent strain, in the members, not in movement at the joints. The only bolts that are intended to resist shear are "fitted" bolts that are the full diameter and in reamed holes.

Thread: Running 'nukes' in the red
02/01/2022 22:46:38

The reason for running nukes at a steady load (not necessarily flat out) is a reactor physics consideration (which I am not qualified to speak on) not thermal cycling. Something to do with the reactor getting poisoned with short-lived daughter products, which is also the reason why it can be difficult to get them straight back on line, after an inadvertent trip.

The limitation with core life is if cracks in the graphite blocks that comprise the core spread too much, the deformation of the core may prevent the control rods dropping in to shut down, if required.

This limitation was known about, and referenced in the safety case, before approval for construction was given. The last 4 AGRs are/ were subject to very close examination of the core passages during shutdowns as a condition of the life-extensions granted by HMG.

I was sad to see the Longannet chimney come down. In 1970/1971 I used to run (well walk briskly) up it to sharpen my appetite for lunch. It helped with the Munro-bagging.The chimney that you saw was a wind-shield round 4 separate flues with a square spiral staircase (if that makes sense) around a goods lift up the middle.

Scotland has no coal-fired power stations left standing and an oil/gas industry at risk from the green lobby which presumably thinks that electricity comes from a sort of magic money tree.

Interesting times, but the nights are long and the weather can be inclement up here...

Thread: Verbal Notes and Sketches
21/12/2021 21:45:00

image.jpegimage.jpegFollowing earlier discussions here about whether the lock nut goes on before or after the full nut, I had a dig:

Sothern's "Verbal notes and Sketches" has illustrations, attached, of 2 piston valve assemblies from different manufacturers. Lockwood and Carlisle's shows the locknut above, Moss-Phillip's below. Take your pick. These diagrams would have been prepared by the maker's Technical Publishing or Sales departments and reflect that maker's practice. The artist would have had the GA in front of him. For purely practical reasons, I have always been in the "lock nut on top camp".

Verbal notes and Sketches was THE book for aspiring marine engineer officers preparing for their Board of Trade exams and is a gold mine for anyone looking for details of reciprocating marine steam engines. My 18th edition is in 2 thick volumes and has many fold-out plates. The one of the Yarrow high pressure water tube boilers for the P & O liner "Viceroy of India" is 21" wide x 14". Second hand copies turn up on the usual flea market site, but I must add a warning - get absorbed in the Verbal Notes and the sun will rise several times before you get back in the workshop.

Thread: Lock nuts / Jam nuts - MEW 311
18/12/2021 22:54:23

The usual justification for putting the thin nut on top is purely practical - otherwise a very thin spanner may be required. This is not valid if the thin nut is tightened first, etc...

re - measuring the tension in the bolt: Triumph motorcycle big end bolts (5/16" or 3/8" dia.?) were tightened to achieve a specific elongation, and hence clamping force, of the bolt. I may have more detail on that, but is a bit late for crawling about in the attic.

The much bigger sizes used bolt heating is used to lengthen the hollow bolt and the subsequent cooling tightens it. In steam chests at close to 565deg C the stud-bolts are hotter than the heaters can achieve. There is a variety of "patent" nuts for high pressure applications, including hydraulic stretching, out there. Someone with recent experience in petro-chem might be able to expand (sorry) on this.

All of this is technically interesting, but of little relevance in model engineering.

Thread: jury service
01/12/2021 21:37:01

I got cited for duty when I was due to be away from home on holiday. I asked for an exemption on account of age, (well over 70) gave my driving licence number, which has date of birth embedded in it, and got a permanent excusal within a few hours.

It has been said that the quickest way to get sent home involves a jacket, tie and a copy of the Times to read in the waiting room.

Thread: SMR's a conundrum.
11/11/2021 22:52:20

A small point on reactor refuelling:

Pressurised Water Reactors are refuelled off load. This can be done during statutory examinations or refits.

The last four Advanced Gas-cooled Reactors were intended to be refuelled ON load and this has been done, one channel at a time, although at reduced load, not full load. The wind down/exchange/reload cycle costs lost output. Some feel that it is more cost effective to come off load when demand will below for a period and do a batch. One complication is that because they were intended to be refuelled one channel at a time, storage for discharged fuel stringers is less the 25% of a reactor's complement. (Unless they have increased it since commissioning)

09/11/2021 22:57:36

Yes, the CEGB had a design/development department at Berkeley but that was part of the problem. They were always looking for something better, rather than just sticking to something that was known to work.

The North of Scotland Hydro-Electric Board had outline approval to build a nuclear station at Stakeness, Banffshire, but the scientists at Berkeley could not agree on which type of reactor to build. In the end, the Hydro Board built an oil-fired station at Boddam, south of Peterhead, which had to be converted to natural gas and/or oil on the drawing board when the price of oil shot up.

That station, 2 x 660mw, did sterling service during the 1985 difficulties, burning CEGB oil and sending their MW's "down the wires"

SMR's will work IF RR are allowed to make them PWRs, which they know inside out. If the government advisers, who told every one to switch to diesel cars, stick their noses in and insist on something new, then stock up on candles.

Thread: UK fires up old coal power plant as gas prices soar
04/11/2021 22:12:53

Pumped Storage (Cruachan and Foyers in Scotland) is great, but further expansion of it hits the buffers when you ask what valley you are going to flood next. Generally, in the Uk, there will be a lobby group more interested in natter jacks, or whatever, than having something noisy in their backyard. In France they do not consult the wildlife, they just build.

Tidal seems attractive, but as I understand it, there two tides every day with not much flow, or output, at high and low water, so something else has to cover the shortages. There was a tidal race system tested in the Pentland Firth, feeding into the grid connections for Dounray Power Station. It got washed away the first winter. Forget unicorns and stick to what we known. We should have built another pair of AGR stations after Heysham2 and Torness while the manufacturing train was all in place.

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