Member postings for Richard Parsons

For many years I worked designing systems which ran on computers. Yes the first machine had valves so that is how long ago it was. These machines worked 7-24. Ok they had shifts of engineers but they seldom failed.

I am puzzled as to why our ‘Modern Electronic speed condolers always seem to fail after a few years at the most. Is it the components? The basic designs or what? I have one speed electronic controller which I built about 30 years ago from a kit sold by a company called ‘John Bull’ somewhere in Soho London. It was and still is used on my Emco Unimat SL.

I suppose that the electronic speed controller are used for cheapness. However there are single phase speed controllers appearing. These are used mainly on ventilation fans and I an investigating them.

For the rest all my speed control is mechanical if it breaks I can rebuild it.

I was somewhat pleased to see the review in MEW of the Warco WM240B lathe. I have two growls/grumps with it.

The first is the speed range to my mind it is skewed towards the high end. 2000 RPM is satisfactory for mild steel of 0.144” (6.4mm) diameter however its low end is 125 RPM is satisfactory for 2.3” (58.5mm) steel. However much of our work (munching away at castings and thread cutting) we really require even lower speeds down to 25-50 RPM. At a quick glance a form of ‘Back Gear’ could be fitted into the final drive pulley. My second ‘grump’ is I would like a form of tower traverse. The simplest form is that used on the Myford Super 7, but I think it could be made even simpler.

Rdgs

Dick

Third thoughts. If you put some AC across the coils you could also use the engine to cool your tubes of the 'Amber Nectar' and warm up your meat pies. The Stirling cycle is reversible. Two uses from one machine. May be if you fitted a bicycle with one of those little alternators you could convince SWAMBO to pedal it.. By the way the you could also use the TMG to drive the bicycle alternator which could then drive a fan. Alternators can also run as a motor if you spin them up to synchronise with the AC frequency.

Regards

Dick

Hi Again David Yes there is a lot of the noise from that particulate example of the TMG (Harwell engine) is probably due to the fact that the generator has a moving ‘clapper bar' type magnet. The noise coming from the brass diaphragm which is probable drumming on the Annulus which is also part of the re-generator and the fact it is air cooled. I think with a little bit of a redesign it could be made quieter. This would be true if you used a thermo cycle cooling system and you might get a better output from it. I think it could be fitted on top of a pick nick stove.

The other thing there is an alternator that runs off the bicycle tyres just needs a bridge rectifier chip and you can charge as you go. I do not know about Oz but a Chinkee set costs a very little. in a bike repair shop you could probably get an old one for a 'tube of the amber nectar'

Hmm thinks what do I need to get my hooks on to make one?

Rdgs

Dick

Hi there again David.

If you really want go via the Stirling engine route have a look at the Thermo Mechanical Generator or ‘Harwell engine’. These were designed to produce electricity and are used widely on buoys especially those provided by Trinity House.

The engine is very simple. It is probably the simplest of all Stirling engines as it has no rotating or sliding parts/seals. Mind you it is not the most efficient of engines having an input to output ratio of about 10 to 1 (10% efficient)

It has a displacer whose chamber is heated. The displacer is sealed by a flexible seal into the displacer chamber. The displacer is not linked directly to a diaphragm power cylinder. So the TMG is a ‘free piston engine, which is linked to either a moving magnet (or a moving coil) generator. You will see one running here . It is being dismantled in this next clip . It can be hermetically sealed if you want to pressurise it. This model can be pressurised.

The Generator provides AC at about 80 to 100 Hz and the machine shown is giving about 10 volts.

It is a noisy little beggar but what fun!

Hope it helps

Dick

Edited By Richard Parsons on 03/04/2012 13:39:25

Hi there. You have a worthy project. One of the problems you will bump into is the fact that there are several things which affect the output of your machine.

The first and most important of these is the temperature difference between the ‘hot’ and the ‘cold’ ends of your engine. As you want to make a low temperature engine this temperature difference will also be low and so will be its output per unit volume. Typically this is about 500 Watts per square meter for each degree Kelvin (Wikipedia)

The second factor is the pressure of the system. A difficulty with pressurization is that while it improves the power output, the input heat required also increases proportionately to the increased power. This heat transfer is made increasingly difficult with pressurization is that you have to make the engine more pressure resistant – beef up the structure. The thicker walls of the engine also increase the resistance to heat transfer. You also have to make certain that the working gasses do not leak out of the ‘Hot-Cold’ cycle area. Phillips did this with a ‘roll sock’. Rule of thumb - More pressure the bigger the engine.

The third factor is the working gasses. Advice –stick to Air/Nitrogen, other gasses are either expensive or dangerous.

Don’t forget friction it is always with us!

First I would try to estimate the output you require then the ‘guesstimate’ Temperature Differential and use the figure of say 300W/(M².K) – I have allowed for friction, leakage and all the rest. That should give you a feel for the size of the thing.

Good Luck

Dick.

Edited By Richard Parsons on 02/04/2012 10:00:34

Ian Most of the brass work from that age was cast. I do not know how you want to make. If you only want a few I seem to remember there was a simple system by a company called I think Tiranti. They sold a simple system. (Usual disclaimer).

There was also a short series in Model Engineers Workshop it was somewhere between 1998 and 2002 but I cannot find it. It shows how to make moulds, make waxes etc.

Rdgs

Dick

In days of old when ‘Gonnes’ were all the rage there were two forms of ‘monkey’. The best known were the ‘powder monkeys’. These youngsters would scamper from their gun to the powder magazine carrying a cartridge case to pick up another charge for their gun. The then scampered back. The second type of these ‘simians’ was the ‘shot monkey’. These maties brought shot to the guns. Normally they carried several shot on a sort of wooden tray also called a monkey.

However when General Elliot who was the C in C during the great siege of Gibraltar (and who gave rise to several inn signs) decided that he had had enough of the Spanish floating (gun) batteries. So he decided to eliminate them with ‘Red Hot Shot’ (the Spanish complained that this was ‘deuced unsporting’ by gad!). To get the ‘Red Hot Shot’ from the furnaces to the guns they needed metal monkeys. These were made of brass. The original expression when things were ‘decidedly parky’ people would say “It is cold enough to freeze the balls to a brass monkey”.

The real trick was to load, lay and fire the gun quickly as the confounded thing had a large lump of red hot iron next to a bag of powder.

Over here in Hungary you can get 2 to 3 months of -20 to -30C. Our little ‘bronze simians’ can suffer If they are not properly lagged. So can various statues.

i dare say others can fiigure out why paper bags one clue is plastic can become brittle at -20C and they cost money.

Edited By Richard Parsons on 23/03/2012 12:51:42

Mountaineer by Martin Evans was a model of ine of the locomotives

rdgs

Dick

Yes Ferric Chloride does dissolve copper. But here we have a combination of copper and steel is a little galvanic cell . Galvanic corrosion occurs with the steel acting as the ‘Wasting anode’

Rdgs

Dick

Andrew Over here I make a little added income in winter. This is from very worried looking little brazen critters carring 'things' in paper bags who knock on my door and ask "Do you do brazing Mister?".to which I reply "Yes and I do lagging as well". You should the relief on their faces

Rdgs

Dick

Hi Bernard Use Ferric Chloride solution it munches steel faster than it munches copper

Regds

Dick

Russel Yes Sodium Ferrocyanide does give off Hydrogen Cyanide (HCN) at high temperatures but only if water is present. Kasenit contained both Barium Carbonate and something else. These formed a coating on the metal. This was done by using the water of crystallisation which boiled off long before the Ferrocynide started to disintegrate into HCN.

If you want to see this get some Epson salts (Magnesiun Sulphate) and warm them up. You can also see the same effect with Borasic Acid (borasic powder) you get from the chemists and use as flux –both of these contain water in their crystals-

Neither the makers of Kasenit or any other company would want to be involved in a Coroner’s Inquest so their products were safe for normal use. I dare say if you ate a ½ kilo or so you would need a few hours with the undertaker.

The lethal dose of HCN can be as low as 1.5 mg/kg of body weight. HCN is also lighter than air. This is why it is not used in military chemical weapons. I weigh somewhere over 75 kgs so to kill me you would require a minimum of 90mg of the stuff that is a large amount as a gas in air. It took upwards of 1/4 hour to kill all the folk in an Auschwitz gas chamber. Elfinsafety do not care they see their job is to keep you safe and damn the consequences

Handrudolph Barium Carbonate is used as a cheap glaze in the ceramics industry, glass making, and in rat poison so go and see a potter, borosilicate glass maker they may give you the few grams that you need

I think we had best leave it at that

P.S Calcium Carbonate can be used in place of Barium Carbonate as an accelerator but it is not as reactive.

Rdgs

Dick

Edited By Richard Parsons on 21/03/2012 13:01:25

The main ingredient of Kasenit is described in literature was Sodium Ferrocyanide. But it also contained an accelerator this was Barium Carbonate. The Barium Carbonate was in a crystallised form and included water in the crystals. If you remember when you heated Kasenite it stuck to the metal. This was because the water of crystallisation melted. At this point I can see the Gnomes of Elfinsafety getting agitated because both Barium Carbonate and Sodium Ferrocyanide are poisons. Barium Carbonate is used in rat poison. Sodium ferrocyanide is added to food salt as an anticaking agent.

rdgs

Dick

Re - Ye Law. In the last centenary sometime in the 80s-early 90s HMG passed a law about transferring Propane from one container to another. To transfer Propane from one container to another you have to be licensed and inspected (there is probably a whole legion of such persons and their regulations who do this.)

I read this in Model Engineer of the period. It was part of a series on building a steam plant for a model boat. The one part which the then editor left out was the filling system for the fuel tank which was for propane. The then editor mentioned the law and said that it was probably illegal to publish the filling system. The series author redesigned and made a new type of the valve system for butane/propane mix (LPG) which was published later.

Stub If your cars run on propane I think you have to change the cylinders. Those gars which are filled from a large tank are LPG which is a mixture of gasses. In hungary the mixture of gasses in LPG varies with the season as it can get very nippy (-25C) over here.

Edited By Richard Parsons on 20/03/2012 08:52:19

JasonB I think I would try a simple Venturi and needle bar carb and get a small amount of Glow Motor fuel first if the compression ratio is about right.

You also have to remember transerring propane with out a licence is illegal in the UK.  Some twazop blew himself up doing it. 

Rdgs

Dick

Edited By Richard Parsons on 19/03/2012 16:19:35

The Glow plug engine uses methyl alcohol as fuel. It works because a mixture of air and methyl alcohol oxidises (burns) in the presence of platinum. This happens faster if the platinum is hot. The process is exothermic it -gets hot-.

Propane does not react in this way. to use propane you need a spark plug! OK!

I think something got lost in translation

Rdgs

Dick

Chris you have three problems

1. To get the broken drill out. I do not know what the “Elmers Tiny column” column is made out of. If it is brass/bronze I would try either a solution of ferric chloride or alum. The other is to build a ‘sparky’ there is a very simple machine by Derek Lynas which you will find here. http://www.stockportsme.co.uk/Membersprojects/img/spark_eroder/Spark%20Eroder.pdf
2. Getting a new drill
3. Drilling the hole, here there is already a lot of good advice. Mine is take it slow, lots of cutting fluid, make sure the vise is secure and nothing can move. Then take small pecks and take it slow.

good luck

Dick

Springbock It was a gentle reminder. some moons ago there was a hoohar in M.E. over a an advert for a cd which showed you how to make a 0.22" Gatling. the ad was later dropped.

Rdgs

Dick

Ps I am making a 1/10 scale Brunswick. I have made the Baker and the 577 Enfield of Indian Mutiny fame

Edited By Richard Parsons on 17/03/2012 18:10:25

this is like the old conumdrum 'Why is a mouse when it spins' It is not a question it is a statement which defines a spinning mouse as 'WHY'

. I am off to feed the dogs an ger a beer or three

Rdgs

Dick

There are some stainless steels which are not totally stainless. These were used for articled where strength and the ability to 'keep an edge' as important as being stain/rust resistant. The Swiss used them in their Victorionix Knives and the french in their Sabatier stuff.

Your treatment also indicates that the bars could have been Nickel plated. what it was used for God only knows. the best Chrome plate was always under plated with Nickel. Chrome is porous

Rdgs

Dick