Member postings for michael potts

Antony.

HPC gears of Chesterfield sell the gear that you require. However to bore is 5/32", still too small for your mill.

You will have to hold it carefully, drill it out and ream it 3/16". If that is not possible then HPC could probably machine it to 3/16" bore. Try contacting them, but it will cost more.

Regards. Mike Potts

You would need a new leadscrew as well, as it will run in the wrong direction with only one extra step. J J Constable tackled this problem in a Model Engineer article in volume 111, # 2790 dated 11/11/54. Essentially he added two extra steps in the screw cutting gear drive, very neatly done, but the explanation was not quite so clear. It took me some time to work out how it operated.

Regards. Mike Potts.

David.

I got the tooth count on one wheel wrong. I read 20 tooth and then wrote 24 down. Apologies.

I you have not come across this internet item, you may find it useful. It is 'model engineering norge'. Written by someone in Norway he deals with the EW lathe in some detail much of it nowhere else. They are worth reading.

Regards. Mike Potts.

David.

The EW lathe uses 16 DP gears. These are relatively coarse and fine feed is not possible. Many years ago someone, J Constable, designed a fine feed. I have the article in an old Model Engineer.

Almost certainly the pressure angle of the gears is 14.5 degrees. Most gears available now are 20 degrees. Going back to gear diameters, the 48 tooth wheel should be 3.125" diameter, the 24 tooth wheel should be 1.625" diameter. I assume that both are on the lathe mandrel, and you do not have the back gear fitting.

Howard Lewis gave a lot of information in his post. If you have further questions come back and ask. Someone will have the answer.

You have a very good lathe, solidly made and easily adjustable. It does use Whitworth and BSF threads, so you would need to become familiar with these. If you need taps and dies to either make or repair them, then Tracy Tools in Devon are probably your best bet.

Finally, could you tell us a bit more about your lathe. What do you have with it, chucks and accessories, but also any other bits and pieces that came with it. It will make any advice you get more relevant.

Regards. Mike Potts.

The valve gear ? My colleague thinks that Thomas Newcomen ever rented a commercial engine with hand operated valves ; the dangers of a disaster were simply too high. We know the Dudley Castle engine had automatic valve gear, because when it was started up for the first tie, ' It made several strokes very quick '. This could not have happened with manual gear.

The story about the boy running the first prototype engine in Cornwall about 1703 could well be true. No one else had the opportunity to actually see what was happening. It is noticeable that the steam valve operation is simple, but the injection water valve operation is much more complicated,using the ' Potter cord '. .

Sorry for these omissions.

Regards. Mike Potts.

You need to get hold of a copy of 'The Steam Engine of Thomas Newcomen', by Rolt and Allen. Get the Landmark edition of 1997 if possible, it has a better bibliography. This book does mention a wide range of information about this engine.

Gravity was used to give a pressure to the injection water. It was simple and effective. When John Smeaton started to look at the design of the engine around 1770, he said that the injection water system should be as high as possible in the engine house. He also specified that the injection water nozzle should be square. This broke the jet up to provide a better spray. To see how this works, look at the internet site ' physicsgirl smoke rings ', and see the effect of blowing a square smoke ring. Water, being denser than air would be slightly different, it would tend to fly outwards.

Getting water up into the injection tank was an interesting problem. The Thomas Barney 1719 engraving of the Dudley Castle engine shows a small pump connected to the beam by a heavy connecting rod to pressurise the water sufficiently for it to rise to a level where it could flow into the injection cistern. The jack head pump came a little later ; it was connected on the main pump end of the beam by a light chain. As the main pump was lifted, the jack head piston was also lifted, forcing water up a pipe to the cistern. The John Smeaton engine drawing shows a more complicated arrangement using an auxiliary beam to operate a lift pump by a chain connection.

Model Newcomen engines have different problems, you would probably need a small motor driven pump to supply injection water at three or four psig. The main pump on such an engine works best using a jack head pump with an adjustable valve to control the flow of water from the pump. A friend of mine had a model engine, built by a toolmaker from his scrap box. I first saw it about 1998 or 99 at a Heritage weekend at Elsecar. I walked into a room with this model working away in a corner, started talking to the operator, and over twenty years later we are still talking. His engine was driven by steam from a pressure cooker, ran very effectively, and provided information about these engines that can be found nowhere else. This engine has now worn out, he has another that he built based on the Dartmouth engine. The single lever valve gear has caused problems, so is probably unsuitable for a model. He thinks that model Newcomen engines can work very well, but do need care, starting with the fit of the piston in the cylinder.

The model Newcomen engine that James Watt worked on still exists. It is in the Hunter Museum in Glasgow, an example of a clock maker's or instrument maker's skill. There is a similar model in Kings college at the University of London.

Jim Andrews wrote a paper about the differences between the Newcomen and Watt engines, and gave talks about it. The paper does not appear to have been published.

Over the last three hundred years a huge amount has been written about the Newcomen engine. The Newcomen Society has published nearly ninety papers about it. Over thirty years ago I began to read about it, and when I was deemed too expensive to employ in 1992, I began work on a patented version dating from 1790, the Heslop engine. Twenty years later I had just about worked out who did what and when and read a paper to the Midlands branch of the Newcomen Society when a row broke out about the site of the 1712 Newcomen engine. So, along with some other people I started to look at the evidence. I did come to a conclusion about it that fitted with some of the contemporary writings ( Well, about thirty years after. ) I have continued to collect information about this engine and others. We still have large gaps in our knowledge and understanding of these machines. People talk about the lack of efficiency of these machines, but at the time there was nothing else that could get water out of mines, apart from water wheels and windmills. The problems that they had are still with us in renewable generation of power.

I think that is all for now. The history of this engine sprawls everywhere, and fresh items keep coming to light. In 2020 I found nine separate items from auction sales to paintings, drawings and one article about a well known engine that I did not know existed. Two items allowed me to estimate the size of engines that we know existed, but knew nothing about. If you think that we do not know a lot about English engines, then the Scottish engines hardly exist at all, and European engines are very difficult to find anything about apart from the fact that they existed in some cases.

If anyone has any further questions I would be happy to discuss them.

Regards. Mike Potts.

I have a hand Perfecto shaper, but there is a motorised one on ebay at the moment at £350. I also have a Swan made near Norwich, also hand operated. The Adept at least looks as if it has been looked after, and all the parts seem to be there. As it does not have a reversible sideways feed it could be a pain to use. Another source of information on these machines are the Kay Fisher shaper columns on the internet.

Regards. Mike Potts

I also have an early Cowells lathe with the 14 X 1.5 mm mandrel purchased about ten years ago. It came without very many accessories, until someone decided to sell many accessories with this spec of mandrel. Having collected them, I decided to check the lathe over as the mandrel bearings had been remade after one of the bearing caps had been fractured. This was the first time I had ever done this, and the results were not good. The dowell pins in the headstock had been filed - not a good sign. Then the alignment was not correct, the mandrel was pointing up and to the rear. So I checked it again and then again the following day. No changes could be seen, so I took the head stock off the bed. On inspection I found two pieces of brass swarf under the head stock. I cleaned everything, obtained new dowell pins and reassembled the lathe. Realignment took well over an hour to complete, but at the end everything lined up to within about half a thou. I decided that this was adequate, if not perfect, sat back, wiped my brow and had a cup of tea.

I fitted the lathe on an old sewing machine stand, and it worked very nicely. The only problems are slipping belts.

The ins and outs of the Perris lathe, its variants, and the Cowells lathe seem to be complicated to put it mildly. The article ' Evolution of the Perris Lathe ' on the lathes.uk website is worth reading. How much is fact and what is opinion is difficult to work out. Brian Perris seems to have been killed in a car accident at the end of 1976. Within a year the PL90 lathe was back in production as the Cowells lathe. It says something that it is still with us.

The design was metricated very quickly, if only partially. Perris lathe dimensions are still used, notably on the mandrel, and there is one BA threaded hole on the cross slide. Care is needed when the smaller and less used screws have to be dealt with, or replaced.

Mike Potts.

There is an Invicta IXL lathe on ebay at the moment, quite well equipped. 3 bids £79, at the moment. It seems to be more or less identical to yours. The gear cover has the name details on it..

Regards. Mike Potts.

A few months ago, I purchased a Shardlow automatic adjustable spanner, a few inches in length. It is a well made and a very solid tool. A quick wash to loosen everything, a brush with a brass bristle brush, and some oil, and it then was completely free and working. The handle is about the same length as my Bahco 6" adjustable. It will open to take nuts from about 5/16" to 1" across the flats. It does appear to be a capable tool, but is just a bit too big to deal with the smaller nuts. It is turned over to tighten or loosen nuts.

Mike Potts

The strap and rod are broken and a solder repair has been attempted in the past. It seems to have just melted more of the rod away though.

Mike.

This is a rather poorly NDC belonging to my son, the eccentric sheave is part of the crank disc.

Regards. Mike.

Edited By michael potts on 23/06/2021 21:07:14

E s Cox wrote many years ago that hardening equipment for railway service was not easy. He was writing about diesel engines at the time, but it took time to get the English Electric engines that became widely used up to a reliable condition. The Brush Sulzers had to be derated after crank case cracking occurred.

This latest problem appears to be cracking of aluminium by prolonged minor vibration. Aluminium and its alloys are susceptible to this problem. Steel components can be stressed, but as long as the stress is below a limit their life can be long or very long. Aluminium has no such lower limit, even minor stressing leads to failure in the long term.

Mike Potts

I think that you will find that what has happened is zinc embrittlement of the steel. Have you heard of Flixborough, a nylon making plant on the lower river Trent, which was destroyed in an explosion some fifty years ago. The explanation was embrittlement of hot pipes by the galvanised netting holding the insulation in place. Zinc migrated into the steel where the netting touched it.

Early nuclear reactors with mild steel pressure vessels had to be kept above about 100 degrees C to avoid the danger of embrttlement cracks in the irradiated steel.

High temperatures are not needed for embrittlement, but brazing temperatures are high enough to act fairly rapidly..

Google Flixborough, and you may find out more.

Regards. Mike Potts.

It is either a Westbury or a Dore Westbury.

Hello BW.

I have two of these toolposts. I bought one for the Myford Speed 10, and made another to for my Cowells lathe. They are very much better than the standard toolpost, and well worth having in my opinion. They are also a lot cheaper to either buy or make than QCTP s. There was a Myford sized one on ebay a few weeks ago.

The body block will be split so that it grips on the threaded upright when the bolt is tightened. I assume that the upright has a 40 tpi thread about 3/4" diameter. It appears to be a useful design variation.

Regards. Mike.

One model of the Randa lathe, also sold by Grayson seems to have an infill in the bed slot. The first photograph seems to show parallel lines along the bed which could mark the slot infill piece.

Regards. Mike Potts.

`Hello Martin.

The Boxford item is a dial indicator as Clive says. It is for checking variations from a zero position ( In the centre of the dial ) such as centring in a lathe chuck, or on a rotary table.

Mike Potts.

Hello John.

Stuart Turner used a 3/16" X 36 TPI thread, usually for small pipe connections pre WW 2. They had a number of standard threads of various sizes, and sold the taps and dies for these threads. They were in their catalogues. My son has these catalogues at the moment, but when he comes in I will get one and put the list in a post.

Tracy Tools stock these taps and dies, Whitworth form.

Regards. Mike Potts.

The equation E = mc^2 is the first term in an infinite series giving the energy of an object. The second term is

1/2 mv^2 which is the kinetic energy of the object. The other terms are miniscule as all are divided by c^2 and higher powers of c^2. The series derives from the calculation of the kinetic energy of an object. The mass of the object changes as it moves and is calculated by the equation M = M0 / ( 1 - v^2/c^2 )^0.5. M0 is the rest mass of the object, M is the mass of the object moving at a velocity of v, so if the object is moving, its' mass is M0 divided by something that is less than 1 making it more massive, and the moving mass gets larger as the velocity increases. If the velocity of the object reaches the speed of light then the mass is then infinite. In practice if the velocity of the object is less than 10% of the speed of light then normal Newtonian mechanics can be applied with little error.

The mathematics of relativity become very complex very quickly, making an already difficult subject even more impenetrable. Infinite series of terms do not help either.

Radioactive fusion or fission is another issue. Both processes work because the mass of the resultant particle is less than the mass of the starting particle (s). This loss of mass appears as energy, heat,light or kinetic energy of the particles. The amount of energy can be calculated knowing the loss of mass. All the work of measuring the mass of atomic nuclei was carried out after work began to develop atomic weapons during WW 2.

Mike Potts.