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Member postings for Tony Martyr

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

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Thread: Why build a Stirling Engine?
16/12/2009 16:33:23
My wife is a great fan of small low delta-t stirling engines because she says they are the only things that I have ever build that don't make a horrible noise.
Thread: Washers
12/12/2009 20:28:29
Washers are also used to minimise electrolytic corrosion when the clamped materials and bolts are well apart in the electrolytic series. We always had to use cadmium plated washes one the casing joints of royal Navy gearboxes. In fact aluminium will scuff badly under the steel nut if washers are not used.
Thread: Why do I do it?!
09/12/2009 09:04:30
Martin
The book to which I refer has the Tacoma Narrows Bridge as the cover photo!
In fact it was a classic case of believing digital calculations unalloyed by experience and 'does it look right'?
Virtual models are only as good as the algorithms they contain and in the case of the bridge there was little design knowledge of the resonance of aerofoil bridge sections. 
I recently caused consternation to a group of Austrian students by using a slide rule to calculate the diameter of a pipe - they had never see such a device and were fascinated to see that my answer was arrived at by an analogue device that allowed me to see how close my chosen size was to the size larger and smaller thus giving room for judgment rather than one digital answer .
I bet most model boilers were designed using slide rules!
Tony 
Thread: How many Boiler makers?
08/12/2009 19:02:50
Well the first soldering jobs have been done today and the fact that I have read all the books (that include advice about how deep to stack the Coke) it did not prepare me for some of the lessons I learnt today by practice.
First mistake: not packing insulating mat around the throat plate sufficiently, so it took too long to get up to temperature. Got there in the end by starting again with a new arrangement in the hearth.
Second mistake: Not removing an AO drawing that was pinned to the wall above and beyond the hearth - lifting the torch while applying solder and not looking where the flame was directed nearly set fire to the boiler design and the workshop!
Third mistake: not really a mistake - more a difficulty. Where the boiler tube was cut to form the firebox there is a small hole created at both sides that was not completely closed by the throat plate (I have a photo of the area in my photo album) I had to peen the gap and re-solder, it appears to be OK (not pretty but OK)
Big success - by the time I got round to soldering the back-plate bushes with high-temp solder I had got the hang of things so got it up to red heat quickly and the solder flowed beautifully.
Also just got news that I got a grade 2 pass in my Open University course and I did not spill sulphuric acid over the garage floor or dissolve my trousers - A GOOD day!
Tony
Thread: Why do I do it?!
08/12/2009 18:39:23
Guys
I'm still thinking of poor Dunstan and his out of line cylinders - puts my own (cheaper) balls- ups into context.
The CAD thread that has emerged is a very deep subject.
I recommend a book written some 20 years ago called 'To Engineer is Human' that discusses the disassociation that can occur when a digital computer is doing complex design calculations for you and giving a totally undeserved appearance of accuracy.
I still have no answer to my original question 'Why do I do it?' - errors must be down to lack of attention I think.
In my work I made a study of project disasters and I noted that when interviewing the persons involved, the phase 'I assumed...' appeared very soon in the conversation.
A colleague who was an expert in the analysis of car crashes related a similar event in his interviews; in his case the key phrase was 'Suddenly ......(there was a tree etc etc)
So a temporary lack of attention leads to the false assumption that I am doing the right thing until suddenly I see its gone wrong!
QED
Tony 
Thread: Loctite on shafts
08/12/2009 09:26:30
Mike
I agree with Martin - when I built a camshaft where each lobe was loctited with 648 onto the shaft I always put the shaft in the freezer overnight. Not only does it give you greater adjustment time but it gives you a greater initial clearance, so long as the male part has been left at ambient temperature of course!
Tony
Thread: How many Boiler makers?
08/12/2009 09:19:27
Hi James
Your experience is similar to mine and is the reason I started this thread.
As to the AMBSC code I have no direct experience but I know that  a vacuum caused by a generational gap in training and experience when coupled with a litigious society that is H&S dominated will mean that some skills will become exclusively 'professionalised'. In such a situation the most restrictive and 'safe' legislation and code will fill the gap because other national organisations haven't got the courage or the skills to modify or create their own.
In my professional life I am dealing with a parallel situation concerning automotive test facilities in Universities where many H&S officers treat the running of an engine in a specially designed cell as akin to handling plutonium - the result is that many students spend most of their time running 'virtual' engine models on computers; this makes the authorities feel they are keeping their students safe from possible injury but also safe from essential experience.
I would love to visit an exhibition and see a boiler made by a 21 year old, which was possible when I finished my apprenticeship in 1965 but sadly less likely now
End of rant - now off to solder the throat-plate
Tony
07/12/2009 10:15:22
Thanks for your comments and advice.
I have decided to use 440 solder in the two areas which will be subjected to significant secondary heating:
The bushes in the backplate
The regulator bush in the smokebox tubeplate
Both these plates can be laid on a fire blanket (obtained from CUP alloys) within the hearth so should get up to temperature without too much gas and a 2238 nozzle.
The remainder I will solder with 842 solder and use EF flux from the same company.
The latest problem I have hit is that the Safety Valve bushes and the Safety valves listed by Blackgates call for a thread of 3/8 x 26 TPI
But neither Reeves of Blackgates seem to list tsaps of this size.
From my old reference book 3/8x26 TPI is a cycle thread - is this the correct thread form?
Tony
 
05/12/2009 15:02:35
Hi Chris et al
I will follow your progress with interest and will post photos of my progress in my album.
I have just managed to get hold of some sulphuric acid for an old fashioned pickling bath and am currently turning all the back-head bushes which I will solder in place with a higher temperature solder than easyflow.
I have found that cutting the large (1 1/8") holes for the dome and the firebox to be quite difficult even on my milling machine with a boring head
Next week should solder in the throat-plate and firebox extension plate - watch this space!
Tony
01/12/2009 16:56:57
From my personal contacts with active model engineers I have come to the opinion that less than half those who happily build a running chassis are, nowadays, building their own boiler.
Since I am struggling in the middle of building my first boiler I think I know why. The skill set is not acquired during modern workshop experience. A different workshop/bench-space area is needed for dirty and hot work and the price of failure of one of the silver-soldering processes can be quite high and only found at (what you thought was) the end. Finally it is possible to buy a completed and certified unit from reputable specialists, unfortunately at a price beyond my 'hobby fund'.
So what proportion of active locomotive modelers in 3.5" and 5" are now making their own boilers and has there been a recent decline?
Tony
 
Thread: Flux question
27/11/2009 14:13:32
I am construction my first boiler. One side of the firebox outer wrapper is formed by attaching an extension plate to part of the outer tube, the other side being unwrapped to form the opposite side..
This plate is butted to the edge of the outer wrapper and held in place with a wide copper strip which overlaps the butt joint and is riveted on both sides. I am currently riveting both the throat plate and this extension plate in place but it will be a couple of weeks before I am ready to silver solder. I have cleaned the surfaces before riveting.
My question is, should the interface between the riveted plates be thinly coated with flux so that it is trapped in the space where (one hopes) solder will run, or should the interface just be a clean void?
Clearly the solder will dry out before I heat it for soldering - does that matter?
Tony
Thread: Britannia Boiler
24/11/2009 10:25:25
Hell Rick
First answer is 'No'
However having just used a block of hardwood as a former material I rather doubt that MDF will work well - Based on recent experience I think the difference in hardness between MDF and rapidly work-hardening copper sheet is probably not sufficient to prevent significant former damage however 1/16 steel sheet on top that forms the start of the radius may keep the edge shape better.
 
Thread: square holes
22/11/2009 19:14:34
David
The task of making a square hole was (a very small) part of my apprentice test piece long ago.
I was not allowed to use the vertical slotting machine, so reproduced the same cutting action in a lathe. Using a square section of tool steel means that by turning the tool in the tool head ensures that each side is slotted at 90 degrees as long as the work is held in a locked headstock.
The problem is that unless the shortest stiffest tool is use the hole will taper in from the entry face so you have to take very small cuts and traverse the whole saddle which gives some momentum to the process.
The form of the tooli difficult to describe if you have't worked on a slotter while cutting keyways but it is like a chisel end with about a 30 degree rake.
At least that is how I did and do it
Tony
Thread: Why do I do it?!
18/11/2009 08:53:50
Circlip you have cheered my morning!
Your first paragraph just rubs in an adage I was taught 40 years ago but your last one puts it all into perspective. Working alone in a workshop with machine tools and gas torches does make the 'soft tissue' vulnerable and mostly (unlike copper) irreplaceable
Tony
17/11/2009 20:37:04
A rhetorical question relating to making stupid errors, presumably when not concentrating on the job in hand.
I have just cut part of the copper of my boiler to the wrong dimension (too short of course) thus making the section a time consuming lump of scrap metal.
It was not a technically difficult job, but with careful deliberation I measured, marked out and cut the sheet to the wrong size - the only excuse I can think of is that I was listening to 'You and Yours' at the time which was irritating.
It is a horrible sinking feeling when you offer up the offending part and realise that gluing metal back on is not an option. The irony is that I had just done the really critical measurement and cutting of the outer boiler tube which had been a success.
I guess I'm not the only one and if it doesn't rain tomorrow I might go an retrieve the part for somewhere at the end of the garden where it landed.
Tony
Thread: Metric vs Imperial - Practical or Traditional?
13/11/2009 17:46:02
I have lived in both New Zealand and Fiji for the years during which they transferred from imperial to metric systems. Both countries took just 12 months and did the job to the satisfaction of the general population by an extensive publication campaign. I remember local discussion in Fiji about the metric equivalent of a 'string of mud-crabs' but common sense prevailed and in the absense of an SI unit the local market measurement stayed.
So I was very shocked when returning to the UK in 1980 to find weather forecasts being given in Fahrenheit and Celsius.
I explained to an French colleague that some folk in England believe that if we adopted the metric system then Napoleon would have won !
Any engineer knows how derived units in dynamics, thermodynamics and power are so much easier using SI units.
The model engineering fraternity do have to deal with the problem of their archived designs and the heritage of old documentation but it was no different in New Zealand where I simply converted my drawings to metric dimensions.
Imperial (the clue is in the anachronistic name) will die out with my generation except for a few die-hards who presently measure their gardens in chains.
Tony M
Thread: Boiler making hearth
08/11/2009 10:01:50
Thank you all for these replies from which I can formulate my preferred solution.
Nigel Hyde's mail reminded me that I have an old workmate bench in the garden shed that would provide a more stable base than a fabricated frame of smaller footprint. For nearly 5 years I was the chief engineer of a cement and lime plant (in Fiji) and was dealing with kiln refractory brick constantly but that is designed to withstand high abrasion so is too heavy.
The 'kit' posted through Niloch is a ice idea but too small for my boiler. 
I have no experience of the blanket materials but this sounds easy to organize than any coke replacement.
I am a great fan of this forum and hope I can be as much help to others as I have received
Tony
06/11/2009 21:50:02
I am about to start making a boiler for a 3 1/2" loco. The last time I was involved in such work was as an apprentice 40 odd years ago when there was a full size coke and gas forge available.
Lacking these facilities I need to make a suitable hearth that can live in my garage. Is there a suitable design available on the web?
Where does one buy a few refractory bricks nowadays and what material is used to pack around the work now that the UK doesn't seem to make coke anymore.
Thread: Starting out
06/11/2009 08:37:37
18 months ago I started out on model loco building, but I already had an old Myford lathe, a miling/drilling machine and experience in building a small i.c. engine and various stirling engines (50% successful !). I had served a craft apprenticeship in the 1960s and remained in engineering all my working life, albeit in much heavier variety than 3 1/2 gauge.
In spite of all this I have found the building of a 3 1/2" 'William' to be a real challenge because it requires a very wide range of skills and a rather extensive set of tools, some of which I have acquired over many years.
What I have found difficult is that the drawings  and dimensions (imperial) give no indication of the limits required so as a complete loco novice, and without the help of any experienced help, the last 18 months have been a period of discovery with some 're-work' required.
I chose 3 1/2 gauge because the materials required are much cheaper than the larger sizes and I can hold everything in my machine tools - the boiler barrel being the tightest fit this week.
I have acknowledged to myself that this first loco is for practice and will not meet the high standards of performance I would like but the next one (maybe a 5" gauge) will be the 'proper one' - should I live that long. I reckoned it would take me over two and a half  years and I am on program.
I have re-learnt a couple of lessons:
1. Pack up work before you are too tired and use the remaining energy to tidy up.
2. Machining is the easy bit - it is work piece clamping and chucking that is the vital skill.
3. Don't set targets too far ahead but take satisfaction in creating each individual part.
 
Thread: 3 ½" Gauge Association
07/10/2009 19:24:29
I do think a 3½" association could be of use to those of us with machine tools that can't manage 5" or larger, which must be many.
I am building a 'William' in this gauge and these forums are my only contact with fellow workers in the same gauge. My local club is mostly 5" and larger and meetings tend to be exclusively about track rules and maintenance!
Incidentally I got the chasis running on air for the first time ever today so am feeling somewhat 'chuffed'!
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