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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: Magnetic chucks on lathes
18/01/2012 18:39:02
I used to use Loctite to 'glue' thin (brass) plates to a faceplate in order to machine the knife edges of windage baffles. We then used to heat the whole assembly to break the bond. This was a standard way of working when I was at work but I can't remember what grade of Loctite was used!
Someone on the forum will be able to quote grade numbers
Tony
Thread: Application of water-slide transfers
17/01/2012 10:35:46
OK I have managed to separate the transfer numbers and backing sheet but judging by the time taken soaking they were probably old stock.
My supplementary question is about varnishing over the fixed transfers -
I assume that as the base paint is gloss then the varnish has to be gloss (Precision Paints) but do I have to varnish the whole loco side - won't the varnished patch look different from the rest of the paintwork?
One of the advantages of making engines in the past has been that I have never had to deal with paintwork which I find very difficult in spite of reading the book(s)
Tony
16/01/2012 16:38:44
I have bought a set of loco numbers to finish off my model 'William'. I had to change my original chosen number when I realized it was one of my PINs!
From long ago I remember putting the transfer in luke warm water for about 30 seconds and then sliding them off the backing sheet with a brush.
I have just had a practice run but the transfer number seems to stick firmly to the (rather stiff) backing sheet even after 3 minutes soaking.
Is there a special technique to get modern decals free of their backing?
Tony
Thread: To CNC or not to CNC - that is the question.
11/01/2012 22:45:06
To answer John's point.
You don't need to learn to manually machine before learning to operate a CNC machine. But a CNC machine is about producing an end result repeatedly with the minimum human involvement in the cutting process. Model engineering, as I enjoy it, is about the process and the tactile involvement in shaping something.
Programming a CNC machine is about as interesting to me a filling in a tax return while working out how to mill exhaust ports is a happy way of getting to sleep and planning the next morning. If your interest is the end, go CNC, if your interest is the journey, craft things manually.
Thread: Triple Expansion Engine (Bolton design)
11/01/2012 14:33:02
The drawing of the HP cylinder block contains an error.
The through drillings of the exhaust ducts are plugged - the drawing note to that effect calls for 7/16x40 tpi plugs.
It should read '7/32x40tpi plugs.
I think the plugging is better done by taking the holes through to the HP valve face where there is more metal than the sides of the casting as shown in the design.
Thread: Basic geometry question
10/01/2012 19:51:58
I think that requires more than basic geometry because it depends on the vertical stacking pattern, in that the balls of second and subsequent layers should rest in the space between every four balls below so while you can lay out the number of balls in the 52mm circle the number of rows above before you run out of headroom is a 'bit tricky'
I suggest the answer is a bag full but someone with a CAD system should work it out.
Tony
Thread: Honing bronze cylinder bores
10/01/2012 17:14:01
I think I am going to follow the method described by Norman (NJH) as it is very close to the way in which I used a large Delapena hone many years ago.
I had not considered Polly Engineering but found a quite good Technical Note on the subject on their web site.
The 'less than perfect' bore finish was produced by a boring-head mounted in my milling machine - because the casing was too large to mount in my Myford late. The HP bore which was machined in the lathe is perfect - the difference, I think, is because the boring head had to be fed by hand while the lathe was on a fine machine feed.
Tony
09/01/2012 20:17:11
I have experience of using (dry) 'flexihones' on car engine liners and 3-blade stone types (oil cooled) to finish hardened gear-wheels but i have never used any of the small hones such as those advertised as 'Cylinder Hone Kit 4-in-1' on bronze bores.
The LP bore ( 1 7/8" dia ) of the engine I'm building is not as good a surface finish as I would have liked but as it is very close to finished size I am considering honing both it and the other two cylinders.
Is this a normal process in model engineering?
I assume it would be an oiled process?
Tony
Thread: which coal to use
31/12/2011 16:16:47
Ben
You should avoid the very bituminous coals because, unlike the steam coals (which have a very high carbon content) they can clog the fire when the lumps weld themselves together.
My first attempts at firing a 31/2" loco were completely frustrated by using house coal. In any case house coal is a very variable mixture some with high ash and silica contents and other, like mine, with high tar content. It is worth getting steam coal from a specialist supplier. I got mine from a guy at the Midlands Exhibition in October and start the fire with kerosine soaked BarBQ charcoal and have no clogging problems since.
Thread: Fly-cutting flat surfaces
28/12/2011 20:39:05
Of course my mill-head is out of true to the table because it is tilted slightly on the swivel that allows 45 degrees movement either side of vertical - a glimpse of the B-obvoius after reading your replies!
Since I have never used the swivel adjustment I have never had occasion to check its setting and only using a 75mm dia fly-cutting tool showed up the problem.
I now have a job for the next raining day - thanks to you all and complements of the season to all users and experts on this forum.
Tony
28/12/2011 17:25:15
For the first time I am using a tipped tool mounted in a fly-cutter on a vertical milling m/c to face the bronze cylinder block of a marine steam engine model. The casting is too large for my Myford lathe.
I have taken care to ensure, by adjusting the position of the tool, that the sweep of the cutting tool is such that one traverse of the head covers the whole width of the work-piece; thus avoiding several cuts or a continuously intermittent cut.
In spite of this the finished surfaces are always slightly dished (the 'valley' being in line with the traverse line of the head).
I can't see why this should be the case although I know that bronze can deflect the tool when facing on a lathe with an unlocked saddle. I have tried different cutting speeds and depths of cut but the effect remains.
It is not a great problem, in the present case, because I have to bed the working faces on a surface plate using a hand scraper but I would like to know the cure.
Any ideas?
Tony
Thread: Reamers - hand vs MT
24/12/2011 14:57:41
I have just posted a photograph of using a machine reamer to finally align the 6 main bearings of a triple expansion engine. I find MT reamers both easier to use in the lathe of milling machine than hand reaming.
Thread: Bearing Material
23/12/2011 11:01:37
Alan
I have successfully used silver-steel shafts running in cast-irom bearings but I made sure that I used centrifugally cast iron bar as the bearing material and (occasionally fed) oil lubrication into the top of the bearings. After 20 odd years of intermittent use both components are 'as new'
Tony
Thread: Help about lagging
19/12/2011 19:55:20
I have used exhaust wrap on a track-car and as boiler insulation bought from:
http://www.demon-tweeks.co.uk/Search.do?method=delegate&n=663&p=242387&s=exhaust+wrap
Thread: Girder crown stays - are they overstressed?
08/12/2011 14:16:20
'All models are wrong but some are usefull'
I admire the confidence with which the quoted stress calculation had been done - I have not so much confidence and agree with Paul's statement:
I suggest that perhaps the girder stays do not act as simply supported beams, that the evidence shows that the beam and firebox assembly is somehow stronger than the simple model can predict.
My boiler has inverted T beams tied together centrally by a transverse link and silver-soldered to the curving roof of the firebox that it overlaps at both ends. Looking at that whole structure under compression defies simple calculation. My boiler shows no signs of distortion and I have never heard, in recent time, of a beamed firebox collapsing so long as the water levels are held correctly.
I am still working (part-time) in an industry where the empirically established best practice of many years is now sometimes being challenged by some PhD student who has modeled a mechanical system on a computer and claims we should be dead.
Tony
Thread: First steam test of 3 1/2" William
30/11/2011 09:37:13
You know David, it was a great milestone. I have enjoyed making the loco over 3 years and have had to practice skills un-used since the days of my apprenticeship in the early 1960s but I've also learnt new skills the hard way. Brass-plate work has become my least favourate occupation, just ahead of painting but they had to be mastered (perhaps not mastered). I thought I would be quite happy to give the finished article to a family member and get stuck into my next (triple expansion) project but firing it up was quite an experience. After remaking the snifting valve I will have another go.
Last year I was given a wrecked 'Gents' Waiting-train tower clock (face, hands, shafts and mechanism) which I carefully restored and, using a solid state 'master-clock' signal, I got working. It was the strangest experience as these cold bits of metal and coils came to life and developed a rhythm of their own that I had no idea existed and started counting my own time span. The loco firing was almost as good because the heat flow brings what was a cold and attractive but 'dead,' metal lump to life. But there are no plans for a garden layout!
Tony
29/11/2011 18:55:40
Got the loco's boiler fired up for the first time today. Re-learnt several things:
1. Fires with forced draught get very hot and it is best not to use fingers to load charcoal etc through the fire-box.
2. Steam leaks are not easy to find until you have steam, then they are very easy to find but aren't comfortable to fix
3. putting super-heated steam into a cold engine creates lots of condensate, which has to be drained and is also very hot.
4. passing pedestrians who see a smoking / steaming model loco in the house drive complete with a 'driver' with burn fingers, stop and ask questions which is neither sensible, safe or convenient.
Test number 2 will be conducted wearing leather gloves and in secret.
Oh! and the ball in a snifting valves need to seat properly.
Thread: How heavy is my loco?
15/11/2011 20:27:45
I spent a lot of money having my Caterham track car suspension adjusted for my 80kg weight and was too mean to put on, or take off, weight; even now I've sold the car (it got faster than me) I stay at that weight with an empty bladder (re: Coalburner's comment) without the help of my own bathroom scales - medical centre facilities a short walk away but I'm not about to hump the loco down there!
I thought this was a question to which every experienced loco owner would have an answer since the legislation under which organisations, like clubs with railway tracks, operate will surely require such data to be known when structures are constructed and trains lifted by club members.
I think I'll withdraw the question and work on my estimation, derived from a primitive seesaw device, that William is marginally lighter than his maker =< 80kg.
15/11/2011 17:19:40
I don't have the empty weight of the loco and assumed such information would be common knowledge to those who loaded their's into the back of cars.
15/11/2011 12:14:26
Having just filled my 31/2" William tank engine with water, as a final check for pipe leaks before firing it up, I realised it was getting too heavy to lift comfortably in certain cramped situations.
Since it is going to be put in the back of cars and on tables outside my workshop I probably should know what it weighs.
Lacking bathroom scales I have no means of weighing it in running trim, so my question is: How heavy is a 31/2" tank engine likely to be when full of water?
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