Member postings for Tony Martyr

I am halfway through building the valve gear and have been creating setting lines to help in setting the valves. Then I realized that I have no idea as to the direction of rotation the designer used - Most marine engine designs seem to favour the ahead direction, since they spend most time running that way but I can't see that in this design it matters, so is it up to me to decide?

I was intending to use the most external of the two eccentrics on the HP and LP cylinders with IP same as HP to run ahead - now I have confused myself and can find no help from the drawings

Can anyone help?

Tony.

In 50 years of (model) engineering I have found that the most difficult job I have ever done is my current task of making and setting up the valve gear on my Bolton triple expansion engine. The machining of the expansion links was OK but getting the 'just right' balance between a running clearance being too tight or slack so that the die-block moves smoothly and the drag-link operates without jamming is not easy. Even neatly silver soldering such small items as the die-block is quite tricky. I think it is the small size and the demanding geometry of the gear that I find difficult meaning that multilple assembly and disassembly is required. I thought boiler making was demanding but this is on a different level.

So what is your most difficult job?

I thought I had every allen-key known to man under 1/2" but I am currently defeated by one for tightening a set of 6BA grub-screws.

Can anyone help with the size? I am assuming they would be an imperial size but my sets don't seem to include the correct one.

Tony

I saw an example of one of these engines during a visit to the London Science Museum. Is there any example known of a model made of this design? It would be a machining challenge to get the timing correct.

I was disappointed by the model of the marine TE engine that I found which had not reversing mechanism. Since I have just machine and set the split excentrics for my model I had expected to see an example of how it should be done at the museum - I have calculated that the finished excentrics are 13% (by volume) of the materials I started to machine.

No need for articles Rod - the proper way of producing a drawing can be found written in any basic level Technical Drawing training course from City & Guilds etc. With the increasing use by model engineers of DRO and CAD/CAM the historical designs are increasing anachronistic and were always, in my view, poor compared with their contemporaneous industrial practice

Tony

Having read the interesting responses to my initial query I am now confirmed in the view that most of the sets of drawing that I have used over 50 years of model engineering are badly draughted, in that, through lack of any dimensional tolerancing, there is no differentiation between important and 'open' dimensions.

Tolerancing makes the interpretation of an engine design easier to understand particularly if, like me, you build multi-cylinder steam or IC engines where the build-up of arbitrary errors can lead to a disastrous misalignments between cylinder and entablature components.

I find it interesting that so many model engineers are using machines fitted with DRO, which gives them the capability of easily measuring to fine limits, yet have no guidance in most set of (imperial) drawing sets of classic designs as to when and where to use such accuracy.

I dislike the concept expressed here that 'model' engineering is a lesser form of engineering and that practitioners simply bodge things to make them fit. I have only made one 'model' in my life (31/2" William done as I wanted to test my boiler and painting skills) all my other work has been miniature working engines in which running clearances, inter-bearing and cylinder dimensional tolerances important, whereas many other dimensions are not.

Looking at the present set of drawings I am using I have come to the conclusion that they were not draughted well and that without the supporting ME articles most of us would be hard put to work out a sensible order in which to build the components and will need considerable experience to judge the relative precision of their dimensions. Its not a good tradition nor a good guidance for young people starting the hobby

Tony

I served a Student Apprenticeship (1960-65) with WH Allen who made turbines, large diesels, pumps and gearing: every component drawing issued was dimensioned in one of three ways: Toleranced, open or calculated.

(Remembering that these were 'imperial' units)

Toleranced dimensions always took the form of the Decimal 'maximum metal condition' dimension + 000, - the chosen tolerance. Bores often had their 'fit' designation as in Size, tollerance, H6.

Machining open dimentions were usually +/- 10 thou and open fitting dimensions were given in fractional figures.

Calculated dimensions were just that but finally set by the fitter's final adjustment.

Why do none of the model engineering designs for locomotives or stationary engines that I have ever seen have toleranced dimensions?

I am currently building a modified version of the Bolton/Bertinat Triple Expansion Engine and without my knowledge of full size marine engines it would be quite difficult to know which of the dimensions are vital in such a composite build up of component assembies.

When I started to build a 3 1/2" William some years ago I knew very little of loco chassis construction and without key dimensions being toleranced I had to learn the hard way. I was told 'don't be too 'tool-room' about the dimensions, as locos need a lot of slack to run' - which I found to be only true in parts!

Have the esteemed designers of the model engineering classics never used industrial practice or guide tolerances in their drawings and if I ever used a modern metric design would I find that the practice is used nowadays?

The next generation of engineers, like the last one, will come from our universities. What proportion will be British by birth is a question that will be govened by the standard of pre-university science and maths education and the financial models available to different students. As a product of a 1960s student apprenticeship I know it was the factory that gave me skills and university that made me an engineer but my branch of engineering (automotive) is today dominated by mathmatical modelling as much as metal and materials science. Key to the continued success of our University education system will be the extent to which Mechatronics is taught and lab facilities are made available in the teeth of financial cut-backs and inappropriatly applied legislation.

Tony (Visiting professor of powertrain engineering, University of Bradford)

I am clearing some of my workshop out in preparation or moving house and have some equipment for sales and other things, like a braking hearth for boiler making, free to anyone that cares to collet it - but I can't find out how to put new entries into the classifieds

Please point me in the right direction

Where abouts are you in the world? I made a mild-steel hearth for silver soldering my 'William' boiler last year and it is getting in the way at present and will not be needed for about 12 months judging by present progress

I also made all the classic errors of a first-time boiler maker (not enough heat etc etc) and I have some sulphuric acid pickle brew so if you are within travelling distance of north Worcestershire contact me.

Tony

I can answer my own question after trying the solder in cream form.

It works OK for surface mounting objects or soldering two plates together with the cream in the sandwich but it doesn't work where you need to form fillets around multiple tubes - or rather it is very difficult to apply and it is easier to use traditional flux cored wire.

I have to solder, at both ends, 24 tubes 1/4" OD into the end plates of a condenser (Bolton Triple expansion engine).

Not sure how to 'tin' the plates or the tube ends in such a way as to get the 24 joints to make as I wave a torch carefully around.

I have a tube (out of date but have been raised on out-of-date food) RS 'No clean RMA dispensing solder cream' that sounds as if it might be the answer - anybody out there expereinced in it use - or have better advice?

Tony

Chris,

This is not a cam but rather a circular section with a hole reamed off-centre by a precise amount, therefore it can be fabricated from mild steel bar. I have just made 4 sets for my engine by holding the turned bar in a 3 jaw chuck centred and mounted on the milling table which is then traversed the (half throw) distance and locked. This allowed all 4 excentrics to be drilled and reamed at the same setting before being drilled a tapped for a locking grub-screw.

Tony

The large bolts that we used to connect the flanges of the propellor shaft sections of large tankers were not tighted by using thie nuts. The bolts were stretched along their length by known hydraulic pressure which also reduced their OD and allowed them to slide into a their 'fitted' hole and then the nuts nipped up before the pressure was released and the bolt clamped the flange.

Study of the second law of thermodynamics for a couple of years will solve most of the questions raised in this thread - and add greatly to the understanding of life in general

What a great story to read in these days of tales of doom and gloom - a small bit of joy and a true victory for the hard work involved

Well done!

I have spent many hours machining the cylinder blocks of my Bolton design TE engine (see album) and I am very pleased with the valve ports and the through drilling of the exhausts.

But I now have to drill the inlet holes from cylinder rebate into the base of the inlet ports. 5 x 6 chances to get the (different) angles wrong, break a drill in cast bronze etc.

I hate this job - my loco cylinders were OK but I am glad the holes aren't on show since they all break-through into the valve ports at slightly different heights.

I can't see any other way to do it rather than setting the cylinders at an angle in the machine vice 'by sight' and starting the holes with a very small slot drill or centre-drill - any tricks of the trade of which I am unaware?

Tony

Alan

There seems to be a number of technical colleges at present selling off the contents of their machine shop. I would suggest you find one of the Colchester range that such places used; they had quite an easy life compared to puduction machines. I think buying a cheaper new unit is bad practice - go for the real thing. Lots of good machines for sale - just Google 'Colchester'

Good luck

Tony