Injector

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Bill Shields
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Re: Injector

Postby Bill Shields » Sun Aug 27, 2017 1:33 pm

Note:

once you have a home-made injector that works, make another few to be sure that you can replicate what you have done...you will need them eventually.

BClemens
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Re: Injector

Postby BClemens » Sun Aug 27, 2017 4:50 pm

Yes, the OP and some of the 'helpers' here are probably along with that note 100%. My suggestion would be to make a number of them at one time - although - it may be as chancy to have them all work as it is to try to make another working one.

Why do you say that they will be eventually needed? Do they wear out? These 'model' ones are made with brass (soft) cones.... is that the wear-out?

BC

Greg temp
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Re: Injector

Postby Greg temp » Sun Aug 27, 2017 5:16 pm

My boiler is complete,passed it's hydro test with no issues I'm now up to the stage of plumbing it ,the axle pump is fitted but have to have the injector to install before I can fire it up,still plenty to do though
It's better to try and fail than not to try at all,

BClemens
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Re: Injector

Postby BClemens » Mon Aug 28, 2017 1:09 am

Well Greg temp; If you desire and can find a suitable one, go ahead and buy a proven/reliable intector from folks who have already been through the development of a dependable device. I personally don't go along with being the funding for a commercial endeavor for a reliable injector. They are out there, and have been out there in the past - nothing has been proven currently. I'll give up a few hundred when a dependable injector/ a reasonably priced injector arrives on the market.

BC

Greg temp
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Re: Injector

Postby Greg temp » Mon Aug 28, 2017 1:20 am

That's an option but not as much fun as machining one fitting it then getting excited when it works,,I see most people make them out of brass,any reason why they aren't made out of stainless steel(apart from being hard to machine)
It's better to try and fail than not to try at all,

Harold_V
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Re: Injector

Postby Harold_V » Mon Aug 28, 2017 2:56 am

Greg temp wrote:any reason why they aren't made out of stainless steel(apart from being hard to machine)

That's a matter of opinion (hard to machine). There are free machining grades of stainless that would lend themselves quite nicely to this application, one of which is 416 (the best to machine of all free machining grades), which is heat treatable. Once the proper configuration is achieved, there's no reason why critical components can't be made of that material. In the hardened state, they could last a lifetime. The main body of the injector, typically a casting, may be a tripping point, however. It might be difficult to find a foundry willing to produce them. The balance of the components can be machined from bar stock, which is readily available.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

BClemens
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Re: Injector

Postby BClemens » Mon Aug 28, 2017 4:49 am

The injector body is a problem only if the device is intended to look like a scale injector, which is nice but has nothing to do with function. The cones are the key to success and longevity (assuming BShields is refering to them as the 'wear out' point) but as said; they could be made of a material more robust - the cone reaming being the critical part of that. The 'D' bit reamers will be the critical machining portion with stainless steel but with careful step-up prep drilling, the reamers would have better chance of success - if they are properly made and heat treated.

I believe making these injectors would be a challenge, but only because of the 'small precision' required. With careful layout and attention to fit-up (as has already been done with a successful locomotive anyhow) making an injector is only hindered by taking the time to do it....is it worth it in that respect... If you have the resources to purchase them, why take the time to make them - unless a challenge is the reason for the workshop.


BC

Greg temp
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Re: Injector

Postby Greg temp » Mon Aug 28, 2017 7:55 pm

I'm not really concerned if they look like the full size ones,as long as they do there intended job,my main issue is procuring a set of working drawings to machine from,
To answer your earlier question,the reason I wanted to build a locomotive is
1 I like steam locomotives
2, the challenge (just to see if I can)
3 there's no fun in buying one ready to go
It's better to try and fail than not to try at all,

Harold_V
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Re: Injector

Postby Harold_V » Tue Aug 29, 2017 1:26 am

Greg temp wrote: To answer your earlier question,the reason I wanted to build a locomotive is
1 I like steam locomotives
2, the challenge (just to see if I can)
3 there's no fun in buying one ready to go

I understand that fully. I worked as a machinist for 26 years. To me, building would be an expression of my talents and skills, which are limited pretty much to machining. I'm not like a lot of guys, who appear to have multiple talents.

It's not the destination that would be important for me, but the journey.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

jma1009
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Re: Injector

Postby jma1009 » Tue Aug 29, 2017 5:51 am

Hi Greg,

Have you bought yet the book by D.A.G. Brown? It really is a 'must have'. His book has the drawings for an injector that will be of a suitable large size for your loco, and a 'large' injector is easier to make than a 'small' one.

Making what I will term 'UK' type miniature injectors is not too difficult given a number of prerequisites:-

Firstly you need to make the tapered reamers. These must be accurately made and with a smooth finish. Once you are over this hurdle everything else is pretty much plain sailing. In the absence of castings for the body, most UK miniature injector bodies are silver soldered brass fabrications so you need to be handy with silver soldering small brass parts.

You need to be able to produce accurate work and good eyesight helps. We are talking here of 1/10th thou tolerances for some of the parts.

An accurate lathe with a high top speed and an accurate sliding tailstock is required for machining the cones.

You need accurately ground lathe tools and some fine parting off tools, and some decent quality small drills that are reserved for brass.

This thread on another forum might be of some interest being my own rather boring ramblings on the subject

http://modeleng.proboards.com/thread/10 ... gn-musings

Principally concerned with smaller 'UK' type miniature injectors I have made and repaired up to and including larger 40 oz per minute injectors.

Cheers,
Julian

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Bill Shields
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Re: Injector

Postby Bill Shields » Tue Aug 29, 2017 7:10 am

If building injectors was easy, EVERYONE would do it.

I like to make stuff also, but I don't purchase pressure gauges, nuts / bolts / most valves or even piston rings (now that I found a guy that sells them for $5.00).

Tried making a whistle and was not happy - even after I purchased 2 from 'experts'....

I don't do castings either - leave that to experts like Dave S, John K and others.

I like having running locos and am of the age where I choose my battles.

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Builder01
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Re: Injector

Postby Builder01 » Tue Aug 29, 2017 8:43 am

Well, even if making an injector was super easy, not everyone would do it. My Mom certainly not make one no matter how easy it was! Some people don't make anything even if it is easy.

The injector on my loco was commercially made in England. It works great. But, for some reason, I still want to make one. I have ordered a copy of the D.A.G. Brown, everyone seems to reference it. I have also collected all the articles I can on the subject.

I did not make my steam oil pump, probably never will, but, I am somehow drawn to making my own injector. These devices are fascinating and strange indeed, with pretty much no moving parts to accomplish an impossible task! I have a feeling that others, who like making things, feel much the same as I.

David


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