injector problems still

This is a very interesting thread. I was going to ask Julian if he could recommend any injectors but he has spared me the trouble by mentioning them above. A good injector is as reliable a a light switch. I drive my Simplex on our very busy monthly running days for 3 hours straight. I have a tank on the riding truck for cool water supply. I leave the water on constantly and use the single injector which snaps on every time. I have lightly pickled it a couple of times in several years (soft water here). In contrast, a loco I finished for someone and fitted 2 injectors and an axle pump has given constant trouble. Despite attention to water valves, clacks and pipework on a couple of occasions, the owner relies entirely on the axle pump. I'll have yet another look at it sometime but it is a big disappointment. Thinner walled 3/16 pipe might help as I suspect the easily available 20 G stuff has too small a bore.

No excuses, they need to be ready to put things right if they sell faulty gear, just like anyone else should.

I just hadn't heard of, and couldn't find, any reference to Chinese made injectors, but if Ron has been told that some of the one he has had are imported, I'm happy to accept that.

We do benefit from many specialist suppliers who have an understanding of the hobby. Clearly while others have had no problems with injectors from multiple sources, Ron has had a string of bad ones. If he and other people who get such items don't feed back to the suppliers nothing will be done.

Ironically, injectors are the sort of precision product where CNC mass production should offer reliability and consistency. I suspect the problem is that the volumes out of China will never be large enough to justify the investment in time to get them right. Alternatively, perhaps a UK supplier with in-house CNC might wish to rise to the challenge.

Neil

Injectors always seem to generate a lot of discussion:- probably because they are a bit of an enigma, I've observed that some people seem to have no problems with them whilst others struggle.

I fitted a commercial injector to my Simplex when I completed it, and it worked fine. But I fancied a go at making my own so read up on it, and to be honest I was far from happy as to how the great and good in Model Engineering described the process, they seemed to make it sound all to easy, but from my own research and long study of drawings I didn't feel that confident to start. Then a fellow club member offered to give me some tuition on the subject, this prompted me to have a go:- I made a batch of five as I reasoned that I would get at least one of the five running, In the end I got all five working, one is fitted to my Simplex and works flawlessly all I do is clean it in white vinegar once a year I've kept one back for spare the rest I've given to fellow club members and are in regular use.

Her are a few pictures of the tooling its not the only way to make them but it worked for me.

Cheers

Stew

Good luck with it glad your own works ok the frustration is so imense when your new and only think that it has to be your own work. i am so lucky to have Julian helpng me a man i have never met but spoke on here and has been amazing. without his help and encouragment i would have sold it by now. to see this injector he made work so well is like winning the lottery.

Ron

Coincidence is a strange thing. I bought a box of old magazines a few weeks ago and today's breakfast read was ME 16th June 1967.

The full text of the correction is: the steam cone was shown as entering into the first part of the combining cone by 0.090 in. This should have been 0.040 in.

In another recent thread I asked advice on how to turn a handle for a rolling pin. I have yet to complete that job successfully. Looking at the cones in Martin Evan's injector drawing is slightly depressing, I see I still have an awful lot to learn.

Dave

Hi stew very impressed any one who van make one of these like you and Julian my hat comes of true model engineers. just wish more where made that worked from suppliers. i have seen so many that don't work at clubs i have been to with guys building Loco's over 30 years still having problem and yes not always the injector mine has been clacks that Julian had to machine. i took some back to polly they checked none where seating and blow me the replacments didnt either till Julian worked on them.

I find it so intresting how you make them and your tooling wish i was that clever or young enough to tackle making them.

Ron

Hi David where down under do you come from and yes never thought about how they perform down under in the heat their. Whilst visiting my Daughter in Melbourne we went to Cambel toen railway he has a lovely set up 2 1\2 mile track round his garden 3 steam two deisel and runs every weekend giving rides. He was after some injectors for his 7 1\4 he is not on the internet so not sure how he got on.

I think in the future clubs need to have built a test bed to test injectors it would really help as all my bought ones need work but lucky Julian is doing mine for me an amazing guy.

Enjoy the cooler weather coming soon for you whilst we have our summer but yours is still like our summer in the winter great to hear from you.

Ron

Hi Dave some one suggested a book to me about injectors called miniture injectors inside and out by d.a.g. brown its very in depth but maths was never my strong point went over my head but it seems to cover everything. i think i will just stay with the ones Julian is doing for me to old to take in plus having Alzhimers does not help at least trying to sort my loco out keeps the brain working a little.

Ron

The only crucial dimension when the steam cone enters the first part of the combining cone is the annular gap.

Both Eric Rowbottam in ME 1976, and in DAG (Derek) Brown's books and articles provide a fool proof method of assessing/gauging same. Eric's method has been in print for 40 plus years so there is no secret.

If you dont get the annular gap correct on the steam cone then even if everything else is spot on to drawings for the other bits, then the injector is unlikely to work.

Gordon Chiverton used a smaller steam cone nozzle than in the DAG Brown articles and his excellent book, and used a larger combining cone 'throat' size. This gives Gordon's injectors their strong lifting characteristics . Gordon's annular gap was quite a bit more than Derek's standards for any size of injector.

Martin Evans never made an injector himself. He copied the C.M. Keiller injector proportions published in ME in 1962, but had very limited experience of driving and firing miniature locos, and had no personal knowledge of how to make injectors other than which others such as Keiller had written in ME. He was completely ignorant of the details of the highly successful designs of Ted Linden. So I would tread a bit carefully with anything written by Martin Evans about injectors!

If you want my own rather long and boring comments on injectors have a look at this

**LINK**

Cheers,

Julian

Hi Julian

Thanks for this very interesting link:- just spent the last hour reading it, there was an awful lot to take in I understood a fair bit of it but will go back and read it again to try and take in the rest, some of the comments about the tooling, assembly methods etc rang true with me from my own experience when I made my own batch of injectors. One thing that did become apparent from the various successful injectors from a range of different makers discussed in the thread is that there are a lot of subtle interaction going on.

I was tutored by a friend ,Peter: who knows Dag Brown, the injectors are to Peters design but I suspect that they will lean heavily on Dags designs, the obvious difference being is the design of the body this is simply a Piece of 3/8" thick Brass Bar cut to size with the couplings soldered on. As well as the drawing Peter supplied me a step by step procedure on how to machine and assemble the the injectors. I did deviate from Peters instructions slightly to suite my own equipment, and suggest to Peter that instead of having a interference fit with the combining cones to fit them with loctite, but he advised against this as he had tried it and found that the heat softened the adhesive and the cones moved and the injectors stopped working, but being a bit of an experimenter by nature I obtain some high temperature loctite and so far after 18 months of use its not let me down.

I was lucky to have Peter to tutor me, any one contemplating having a go at making their own injectors, I would advice them to seek out an experienced tutor, injectors are not like the run of the mill item, you have to adopt a different approach but once you have grasped the principles they should be within the capability of any experienced model engineer:-

lets face it if you go down the track with a loco fitted with your own injector you certainly get some bragging rights.

Thanks again for sharing your experiences

Stew

Edited By Stewart Hart on 04/03/2017 08:41:16

Hi Julian well you certainly know injectors i thought it was great to read but have to admit it went over my head.

i learned a lot from reading but know i could never ever be able to work to such close tolerances.

i think so many will be very pleased to learn more about them you really do make it interesting and help to solve the mysteries of them.

Did my other injectors arrive in post so interested to see if you found any thing wrong with them.

i know one will be past repair and my fault but i learn what is wrong after you look at them and find fascinating.

look forward to hearing outcome.

a very grateful Ron

You're too modest Julian, that's a very interesting read. Thanks for providing it.

Dave

Hi Stew and Dave,

Glad to hear my ramblings were of interest to a few.

Anyway, Ron sent me 2 injectors in the post. One is an example from Reeves that I've not seen before and is a bit odd, and anyway is unfortunately a 'bin job' due to an unfortunate fatal accident.

The other is of a type I have now 4 examples of sent to me by exasperated loco owners who have purchased same all in the last few years from 2 particular well known ME suppliers.

In the above 4 cases the original steam cones are a rattling fit in the bodies and the delivery cones arent much better.

Ron's example has cone sizes of say No.56/46 thou (steam cone throat), No.66/33 thou (combining cone throat), and No.71/26 thou (delivery cone throat).

This is way way off the radar of what will work! The others are pretty much similar.

To add to the complications the loose steam cone nozzle is 83 thou OD, and wont even fit into the converging tapered first part of the combining cone being far too big, and more suitable for a much larger injector. It is also too short by 25 thou.

The combining cone proportions are also not ideal in length - the 2 halves being shorter than standard.

Now if anyone can make out a case for a 56/66/71 cone sizing to work I would be very pleased to hear from them!

Usual sizes for this type would be 60/65or 64/70.

Someone is currently making and selling to some of the ME suppliers the most lousy badly made bits of brass that will never work, and giving miniature loco injectors a bad name in the process.

I should add I have no commercial interest whatsoever in this matter. I make my own injectors and a few for close friends. I detest repetitive work, and the idea of making these gadgets commercially would bore me to tears and drive me up the wall.

Cheers,

Julian

Hi Ron,

I'm about 4 hours west of Sydney. It has been one of the hottest summers anyone can remember getting up to 40deg C. Even water in tenders gets too hot for the injectors to work reliably. We didn't use ice on the Jan running day and had lots of problems. I was putting my loco back together after a major overhaul leading up to the running day and couldn't get the injectors to work until I fired it up early in the morning before the day heated up, and put fire bricks between the frames and injector bodies. Then they worked okay. I didn't bother putting water in the side tanks of my loco because it's well known that doesn't work well with injectors. I filled them with sand for weight.

During winter it goes from about -4dec C at night to 8-12deg C during the day. Maybe not as cold as the UK, but cold enough! Quite a temperature range around here.

I read a good web page someone wrote about the process he went through making and testing his own injectors, but I don't have his persistence so I'm not sure I'd make a go of it. But he had a means of testing them off the loco which seemed a good idea to eliminate the many parts on the loco which can be at fault.

As far as I can tell they work well until one of a million things upsets them and then you have the joy of cleaning them, checking the pipes, valves, taps, filters, clacks, sacrificing chooks, and who knows what else.

Just to put this in a fresh context:-

Perhaps its all a matter of economics, from what I can understand a good working injector in the 1930 cost £1.50 when the average wage was £5/wk, in 2017 the average wage is around £500/wk meaning wages have increased by about 100 so the ? is would you pay £150 for a good reliable injector, when injectors of dubious quality are in the £30 to £40 range, if you drop on a good one at this price you've got yourself a bargane, but you may have to but 2 or 3 to find that one good one so in the end quality costs.

Back in the 1930 money was tight and people were more inclined to make do and mend and have a go at making stuff them selves. I must admit that I buy most of my fitting because of their low cost, its not worth the time and effort of making my own, but perhaps we need to change our thinking on this.

Stew

Edited By Ron Hancock on 05/03/2017 12:08:40

Hi Dave thought i would share some shots of my friend Colin and Nancy Cambel from Melbourne Australia such nice wonderful couple with a 2 1\2 mile track in his back garden and runs every weekend.

Dave's comments are of interest because an ordinary injector will not work if the feed water temperature is over 46 degrees C. The maths and science behind this is in DAG (Derek) Brown's excellent book on miniature injectors, and concurrs with the explanation in my second edition of Pullen's book dated 1900.

You can make an injector that will feed hot water, but it requires a second steam cone to be incorporated. Special injectors of this type were made by the UK major manufacturers in fullsize for use on locos in India and South Africa etc.

A miniature injector that is below the water supply will probably perform a bit better with a warmer feed water supply, compared to the same lifting type injector fitted above the water supply.

If I am running on a very hot day in the UK (very rare) I leave the injector water valves open all the time. The tender or tanks need replenishing far more often, but if a mains supply it will keep the feed water temperature down to well below 46 degrees C.

Cheers,

Julian