INSIDE MOTION No 14 April 2021

News and Views from the
TYNESIDE SOCIETY of MODEL and EXPERIMENTAL ENGINEERS

Download IM document in PDF format here

Preamble

It‟s been a long time coming, but finally we have a glimpse of life returning to some semblance of normality. Providing that nature (or people‟s behaviour) doesn‟t throw us all another curved ball (and events in Europe are proof positive that it can) the Government‟s Road Map for escaping Covid restrictions seems to be holding up thus far. Let‟s hope we can all travel carefully and safely along the road ahead.

The Route back to Normal

The Committee has talked over the safest way to get the Club back to normal while following the Government guidelines and recommendations. As usual, a lot of the information available is open to interpretation – what exactly does “stay local” mean ? Some advice is mandatory, some recommended … Anyhow, we have come up with the following …

After March 29th we will meet in a maximum group of 6 people outdoors with the intention of getting things ready for the ability to meet in a larger group in May.

As previously the Gardeners will meet on Tuesdays, the Maintenance Squad on Wednesdays and the Sundays to be used for boiler testing with two Boiler Testers present and up to 4 people having boiler tests done – a maximum of 6 people on site.

After May 17th we will be allowed to meet in groups of 30 outdoors and after June 21st we are effectively back to normal with all restrictions lifted.

Please note that the above is only open to those who have had their vaccination.

Note – Boiler Testing – if you require a boiler test please pre-arrange this with Linda and book a Sunday after March 29th. Do not just turn up and expect your boiler to be tested – this has to be a pre-booked arrangement and is strictly limited to a maximum of six people on site at any time.

We are not, in the immediate future, contemplating public running until we see how things settle down, but it will be nice to see this resume.

Thank you everyone for renewing their subscriptions as, at present, this is the only income we have but the insurance and rent still have to be paid. We are fortunate that through prudent management of our account our Treasurer Ian has a reserve that we are using to keep things going. As I write we have almost everybody signed up for 2021.

One further piece of news – Ian has organised online banking so subs and any other payments to the Club can now be made online. With the cheques being used less and less this is a sensible move. Please, when completing an online payment, fill in the reference line so Ian knows what the payment is for.
Peter Newby, Chairman

People

Junior Engineer Sam Yeeles has had two more of his photographs published in Heritage Railway Magazine.

SR No. 926 “Repton” climbs the grade towards Goathland in afternoon sunshine with an “Optimist” service from Whitby to Pickering. HRM Issue 277 February 2021
Lambton Tank No. 29 approaches Goathland „down‟ platform with a morning “RailTrail” service which terminated there. HRM Issue 278 March 2021
Members Musings

I used to buy Injectors

Adrian Morley

Building an injector has been one of those projects I have been getting round to for the last 20 years. Encouraged by Mr. Mee‟s success and with D.A.G.Brown‟s book “Miniature Injectors” as a guide I decided to use the winter lockdown as an opportunity. Building 7⅟₄ inch locomotives is not the best apprenticeship, but a year or two building Southworth pumps had introduced me to a degree of precision engineering hitherto unknown in my workshop. Injectors take this to another level. I have nothing but praise for Mr Brown‟s methods and instructions. The methods described are based on the use of hand-wheel measurements on a Myford and use imperial and number drill sizes with some metric measurements.

Achieving the level of accuracy needed is not easy and I have a graveyard full of pieces which failed to reach the standards required. I was unable to steam locomotives in Corbridge during lockdown to test injectors so I decided at an early stage to build the test rig described by D.A.G.Brown. The rig also allowed detection of leaks in the body which must be corrected before the next stage of cone insertion could be attempted.

The tools needed (brazing jig, cone D-bits, insertion tools ) took about 1 month to make. I was fortunate to have a grip-tru chuck which could be centred accurately. The reamers have a spigot 15 thou. diameter to aid halving the D-Bit. Quite a few of these went in the waste bin.

The jig is shown with the five parts of the injector body in position for brazing. New to me was Jewellers silver solder in a syringe with a needle which allowed accurate placing and which I now use for all small jobs.
The valve and overflow cover are the most tricky items. The simple method of machining differing diameter curves on the cover is a delight. The valve cap includes the equivalent of a cage to contain the ball and means that these injectors work at any angle (a claim not yet tested by me).

The test rig shows a brazed body being tested for leaks with plugs isolating the body. Water is the test medium and allowed localisation better than steam. About half the bodies I have made needed further brazing.

Making each of the cones is a small project in which the hand-wheel directions worked well, but I soon changed to using the DRO. Total concentricity is essential and not always easy with tiny drills. A start with a small slocum type drill was my solution.

The combining cone snout is the most obvious site for a wandering drill to be obvious but small errors are easy to miss, and replacement has resulted in considerable flow improvement. The cones need to be accurate to about one thou, and a tight press fit, The positioning of the combining cones in the body also needs similar accuracy.

The snout of the steam cone is 80 thou, diameter plus or minus half a thou. and only 2 thou thick. It needs to be accurate since it should be only 7 thou, from the 9 degree cone wall into which it is inserted. This gap (the annulus) determines the flow of water into the combining cone and is the main site of problems.

Once the cones were inserted the test rig came into use. Steam from the boiler comes from left and right into the test rig and pushes against a piston. If the injector works the piston is pushed to the right opening a valve and water flows into tank 2, otherwise water or steam leaves the injector by the overflow to tank1. Pressure on either side is continuously monitored. Iphone video records a test which takes about 2 minutes. Steam is supplied by a small boiler behind with the safety valve at 80lbs/sq inch. The temperature probes in the outflows are barbeque meat thermometers. The readings from probes 1 and 2 alternate every few seconds.

In a successful test the injector pressure rises abruptly above the boiler pressure,overflow from the injector ceases and there is a strong flow into tank two. As pressure falls the injector begins to drip until pressure falls to 20lbs or less. The temperature of outflows is between 60and 70 degrees. A well-adjusted injector will also start when steam is turned on before the water.

The following diagrams help explain the results of tests on a few injectors. It should be emphasised that this rig tests the ability of an injector to start and to work over a range of pressures. The small steam capacity of the boiler prevents measurement of output at a uniform pressure.

Here there is a small gap (the annulus) between the tip of the steam cone and the wall of the combining cone. At this point water and steam mix optimally. If the annulus is too wide, excess water will enter the combining cone and be ejected via the valve to the overflow.

Here there is insufficient steam entering the combining cone, and the excess steam bubbles back into the water tank.

Here the tip of the steam cone closes the annulus and only steam appears at the overflow.


The temperature of the outflows is largely determined by the proportions of steam and water. Low temperatures (40-50 degrees) indicate excess water. Functioning injectors have outflows in the 60-70 degrees range. Higher temperatures suggest penetration of the combining cone is too great.

This test chart shows that with increased penetration of the combining cone by the steam cone the flow increases. The pressure produced by the injector increases in line with temperature.

My injectors seem to work best with penetration greater than the 30 thou. given by DAG Brown. I suspect that I may have taken the combining cone reamer a little too far

I now have three injectors which work satisfactorily in that they start with either water or steam. I look forward to trying them out on a locomotive. This has been a project of many errors and a steep learning curve, but satisfying overall.

The Graveyard

Tales from Lockdown
By a TSMEE Railway Wife

This time last year we were in India enjoying our Rail Tour. That was the last time I have been on trains, stood in rail museums and on train platforms watching my husband vanishing down a rail line in search of a particular train or engine shed.

Who would have guessed the year we have had to endure ? The joy of seeing hubby off to TSMEE twice a week so I could have the house to myself has disappeared and I really miss it. That time Norman had with like-minded people to discuss railways in their every form has been sorely missed.

My saving grace has been that I also have an amazing hobby of lace-making and sewing to keep me sane. Hours spent over a lace pillow make up for his time at his attic layout or workshop. We have never in all our married life had so long under the same roof and I am glad to say that neither divorce or murder have ensued in this time !

The Postmistress at our local Post Office is now my friend. Norman has been selling surplus rail stock and books through eBay and I am now an expert in the selling process. The only downside is that all those parcels leaving the house should have left more space but I fail to see it !

Every enthusiast needs friends to act as a sounding board for their ideas and research and Lockdown has made that really hard. Also, the sad loss of Jimmy Stephenson meant that hours of chat have been lost to Norman. I am a poor replacement as I have, after 31 years, only gained a minimal knowledge of the train world, having kept my head down in my projects while he has been at TSMEE

I long for the day when I can send him off with his butty box to “play trains” with his pals at TSMEE. I‟m sure I won‟t be the only wife or partner who will look forward to that day. With the vaccine programme and some sensible behaviour by others I pray that it won‟t be too long in coming.
Diane Blackburn

Calling all budding authors …

The Crowood Press is a specialist Publisher for the Hobbies and Interests markets. It has a well-regarded list of model engineering and metalworking titles. Your Editor received the following from them …

We are keen to expand the list of titles we have and are currently keen to hear from model engineers who might consider writing for us. We do have a wish-list of topics, but we also consider titles that are proposed to us.

I wonder if you might know of some potential authors – perhaps amongst the contributors to your newsletter ? I would be grateful if you would consider forwarding my message on to them, please, and then they can contact me for further details (under no obligation).

Alison Brown, Commissioning Editor

If you are remotely interested, contact me in the first instance and I will put you in touch.

Postamble

Thanks as ever to those whose contributions have made this issue possible. With the gradual easing of restrictions comes the chance of the Club starting to generate its own news again. Nonetheless, what you are all doing in your various workshops, sheds or wherever still remains of interest, and potentially helpful, to the rest of us. A few words and a couple of photographs is all it takes to share it.

Contact information
  • Newsletter Editor – Mike Maguire – mike.maguire@btinternet.com
  • Club Secretary – Linda Nicholls – lindanic@sky.com – 01 670 816072
  • Website – www.tsmee.co.uk
  • Webmaster – John Rowley – johnrowley@btinternet.com

Headquarters and Multi-gauge Track – Exhibition Park, Newcastle upon Tyne NE2 4PZ

Posted on