Member postings for DiodeDick

I fitted a digital read-bar to the long travel of my ML7R and would not be without it. They cost around £30, depending on length, from Arc Euro Trade, Chronos Tools and others and in my humble opinion worth every penny.

Dick

In ME 4725, Duncan Webster mused that the point of raising the cylinders was to keep them clear of the ground, which certainly was a consideration on the later KS Wren's.

In The Industrial Railway Record, Issue 60 - June 1975, the late Rodney Weaver states that the arrangement stemmed from the requirement that all the moving parts of a steam tram loco should be covered and that by raising the cylinders above the line of the (non-existent) running boards it was also possible to reduce the width of the loco and to do the oiling from inside the screens, without dismantling them.

His references were to The Engineer, 31st May 1878 (Graces Guide at a price, or possibly at a Reference Library near you and to an IRS publication "Indistrial Locomotives of Switzerland"

Issue 60 of the IRS Record is available on line and includes a Roger West drawing of an SLM loco with this valve gear.

Dick

My Norfolk (nee Flexispeed) 2 x 12" lathe was driven by an open frame washing machine motor of unknown parentage from a workmate's "this might come in handy, some day" pile. I did not record any name plate details from the motor, possibly because there was none. Remember that this was in the mid-70's and rules were different then. I did note that the belts were Z500's. With the motor and countershaft mounted on a board, the motor bounced, as noted in earlier posts. I minimised that with a suitable block of wood under the board - this left the belts tight enough not to slip in normal usage, but able to slip on a dig-in. DC motors and electronic speed control? How times have changed, for the better.

Dick

4 3/4" gauge is actually correct for 1":1ft scale. I believe that some museum models, and perhaps the original "Cosmo Bonser" (if I got that right) were built to that scale. It is far more convenient if modelling from work's drawings than the the 1 1/8" used since the 1940's for 5" gauge. Prior to the change lead by Maskelyne the scale used was 1":1ft which left loco's looking a bit bottom heavy.

dick

Yes, well spotted Duncan, the current scale for 5" gauge is 1 1/16":1ft, not 1 1/8". Anno domini.

A model of "Cosmo Bonsor" (note corrected spelling) built in 1910 by J C Crebbin is held by the Science Museum. Their website gives no indication of scale or gauge.

The silver model that I can see in my mind's eye is not the "Como" by Dr J Bradbury Winter that features in Vol 1 of 1898 of the Model Engineer (and amateur electrician).

Still some more digging to do, just for my own peace of mind.

dick.

4 3/4" gauge is actually correct for 1":1ft scale. I believe that some museum models, and perhaps the original "Cosmo Bonser" (if I got that right) were built to that scale. It is far more convenient if modelling from work's drawings than the the 1 1/8" used since the 1940's for 5" gauge. Prior to the change lead by Maskelyne the scale used was 1":1ft which left loco's looking a bit bottom heavy.

dick

Yes, I know the difference between internal resistance of a battery and source impedance of an ac circuit, but in line with the request in the original post, I was trying to keep the the explanation within terms that a 10 year old would understand.

Dick

Electro-mechanical relays (typically) comprise a coil wrapped round an armature. The frame supporting the armature has a movable bit which can change over the contacts, and sometimes move a "flag" which indicates whether the relay is on or off. Current passing through the coil creates a magnetic field which attracts the movable bit and changes over the contacts. The coil has a nominal voltage, 50volts DC, or whatever and the maker's data sheet will specify the tolerances on the nominal figure. During system commissioning "Pick up" and "Drop off" voltages will be recorded. Pick up is usually about 80-85% of nominal and drop off maybe 60%. The current passing through the coil is dependent on the voltage and is substantially less when the relay is "energised" because the moving bit is drawn onto the exposed end of the armature, closing the magnetic circuit. This characteristic was exploited by the Laycock overdrives fitted to 1960's cars. A fair bit of current was required to energise the relay, and end hence engage the overdrive, but comparatively little to maintain it. The other side of this trait is that if sufficient current is not available to properly pick up the relay, the magnetic circuit will not be closed, full current will be drawn and the coil will burn itself out. That is how washing machine door lock solenoids fail during supply "Brownouts"

Those with nothing better to do in the workshop will find lots more online about the Clifford and Snell D2600 relays which were the industry standard for the protection circuits of large power plant turbines of yesteryear.

Dick

I had a similar experience 2weeks ago when I picked up the then current issue of ME. It came bundled with "The King of the Light Railways" ( The story of Col. Stephens) which I might have been tempted to pay £7.99 for. Pot luck, I suppose...

Dick

Before you start building this, check the availability of the 30deg hex bar shown in fig1.

Dick

Hello, Packman:

I have ME's from 1975 to 1985 in Easibinders on my bookshelf, which is why I could quickly check if it was there. If these contained the issue that you wanted, then of course I would help.

I think (and may get shot down for this) that your date (1984) was wrong. 1984 is vols 152, 153.

I ran out of shelf space, so what I have left of later issues are in boxes in the attic and my knees really are not up to scrambling about up there now, which might leave the kids with some tiding up to do...

Best wishes,

Dick

Sorry, "Packmule" but I have Jan - June 1984 on my lap right now and it is Vol 152, issues 3720 - 3731.

Just check your reference for typos and try again.

Dick

All those years ago, I fitted a sleeve made from copper plumbing tube to do just what Thomas wants. The sleeve does not to be a complete circle, cutting a bit out and squeezing it in to the required diameter worked perfectly for me. However, when the time came to pull the pulley off for the next iteration, it would not budge (and having been a Clyde- trained Land Rover driver brutality came easily to me). I bet that countershaft and pulley went to heaven together. Be careful !

Dick

There certainly is a lot of "traditional" wisdom (aka folklore) that the tannin in oak can cause corrosion of steel tools, but that the tendency can be neutralised by "fuming" in an ammonia rich atmosphere. There was plenty of oak, but never mahogany, tool chests in the cold and damp satanic mills of Clydeside, usually where the more sophisticated work was done. Quality tool chests might well have been "fumed" but are the cheap imports? I have seen a mahogany chest on sale at an antique fair - it was alleged to have been the property of a clock maker. The same stall was also offering a wrongly assembled Pultra. When I asked (tongue in cheek) what it was, I was told £350, which probably speaks to the knowledge of the stall-holder.

Dick

In the dark satanic mills of Clydeside in the sixties where I served my time (as an apprentice marine engine fitter) most of the drawing dimensions were in fractions - possibly just as well, as there were very few micrometers outside of the tool room.

The tolerance on Fractional sizes were meant to be to the nearest similar mark on a steel rule, ie a 16th inch size was to the nearest sixteenth on a steel rule.

Decimal sizes usually had an actual tolerance specified.

We all had learnt our tables up to 12 times at school, now we had to learn our 1/8ths times table - 1/8th equals 0.125", etc. And 3/16" was just half of 3/8. 17/64" was difficult.

As an aside to another discussion here, a 6" rule was also used as a teaspoon. Hence "how much sugar do you take in your tea?" - answer "an inch and three quarters"

Dick

Hopper mentioned a leadscrew clutch design inthe Feb MEW, which I have not read. It sounded like the Duplex design in ME 3rd Nov 1949, page 573 on. Apologies for the poor quality of the photo from that article in my album - I am between computers, and hence scanners just now.

Dick

It is a lovely bit of kit - looks as good as new. By comparison my old warhorse of an ex-industrial ML7R looks like it has just been pulled out of a skip.

What caught my eye was the dog clutch on the leadscrew. I put one on my first lathe (a Flexidpeed Meteor) but it had an extra leadscrew bearing below the front mandrel bearing. I wasted a lot of time looking for an elegant way of providing that support without building three-quarters of a QC gearbox shell.

I wish had seen that photo 20 years ago. Too late now...

Dick

Inspired by the articles in ME, I built a two-speed leadscrew drive for my Myford 7R. Swing the new banjo up and it meshes with the tumbler reverse output gear for screw-cutting, swing it down and it meshes with with a belt driven worm wheel for fine feed. It all fits inside the original change wheel cover. No messing with oily gears, as required with a QC gearbox. There are some photo's in my album.

Just as Martin Cleeve promised, it saved a lot of time when making fasteners, for bike restorations.

Every week or two there are queries about screw cutting on this forum which are all answered in Cleeve's book "Screwcutting in the lathe" in the Workshop Practice series. The queries are usually about gearing and seldom about repeat pick up, which is the chapter worth reading over and over.

Dick

Bird scarers in the garden -

Old CDs hung up on strings,

These are a pigeon' least favourite things.

Dick

I was surprised that no one mentioned the Daf Variomatic transmission.

i have seen a similar continuously variable transmission used on coal feeders. They used chains and grooved pulleys, rather than fan belts. Wish that I could remember who made them...

Dick

It's a bit off topic, but the comment that "Wikipedia is not definitive" is an understatement.

Check the Wikipedia Commons entry for "Decauville locomotive Lilliput" Most readers here will spot that in the engraving in the middle, the loco has outside cylinders, whilst in the two photographs, which are believed to be the Corpet works photos, there are inside cylinders, actually a V-twin with longitudinal cylinders on a common crank and slip eccentric valve gear reversible from the footplate.

When this was brought to Wikipedia's attention, through their community of experts, they removed the work's photos and kept the engraving. The photos were reinstated some time later. The loco in the engraving is a later one, probably built by Couillet, bearing the same name but definitely not Decauville 0001.

Dick