Injector

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BClemens
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Re: Injector

Postby BClemens » Tue Aug 29, 2017 3:43 pm

Anyone heard of 'Polly' injectors from the UK? A few years back they had some noted issues with machine work quality and attention to detail (polish) in their cones. Some of their injectors did not work at all. They are relatively cheap compared to other equivalent devices - especially US made ones. They do not have cast bodies - silver soldered.

I gather from reading here that the wear point with an injector is the brass cones - thanks Bill Shields for pointing that out. Isn't it amazing that it seems to be the material of choice for commercially available injectors. Thanks Harold V for your recommendation of a more suitable material.

Also thanks Greg for bringing this interesting topic up - among a number of similar discussions on the manufacture of an operational injector. Someone should offer a 'blank' body casting for a 'consumable' for the in shop making of an injector. I would buy a few.

BC

Greg temp
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Re: Injector

Postby Greg temp » Wed Aug 30, 2017 12:36 am

Thanks guys your input thats been invauble,I have visited the links you have provided and got some great pointers,at least to make a start,,
Spent some time in the workshop last night,started making the D bits nessisary to make the cones,
I'll have a go at making them out stainless steel(fingers crossed)if not I'll make them out of brass,
If I made the body in stainless and the cones in brass,would there be any issues like corrosion between the two,
In the process of drawing a set of machining drawings to work from,
Happy to share them to get yre feed back,
It's better to try and fail than not to try at all,

Harold_V
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Re: Injector

Postby Harold_V » Wed Aug 30, 2017 1:48 am

The machining of 416, as well as 303S or 303Se will be relatively easy, but keep one thing in mind. Stainless work hardens relatively easily. When using large area contact cutters (like tapered reamers) it's a good idea to keep the speed quite low, and don't allow the cutter to tarry. If you keep it well lubricated, it will cut a nice surface, so there's little need to allow it to "spark out" (a term used in grinding, whereby you allow the cutter--the wheel--to remain in contact with the work with no further feeding, so miniscule highs are removed, improving the surface finish). If you do an adequate job grinding the reamers, they will yield a decent finish without rubbing. Keep them sharp, and allow only a turn our two before withdrawing the reamer, once size is achieved.

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

Greg temp
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Re: Injector

Postby Greg temp » Wed Aug 30, 2017 2:11 am

I have done a fair bit of stainless machining all my valves are made from 316,I'll get in touch with my local supplier and see if they stock 416, if not 303 maybe,,I think trying to make the cones out of 316 is just asking for trouble
It's better to try and fail than not to try at all,

Harold_V
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Re: Injector

Postby Harold_V » Wed Aug 30, 2017 3:09 am

If you have experience with 304, 316, 321, or 347, you'll really enjoy any of the free machining grades. The only difference being that 303S doesn't yield a shiny surface when being machined. It doesn't tear, but lacks the brilliant luster you get from 316. Much easier to machine, though. Best of all, all three of them respond quite nicely to heavy roughing cuts, very unlike 316.

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 » Wed Aug 30, 2017 5:02 am

Greg,

Forgive me if this is an unnessary input but: your reamers will do better and last longer if you 'step' the hole it is acting on. This is where CAD is so useful - that is to lay out the tapered bore and step into it with progressively larger drill bits so the D bit is acting on segments or corners. CAD the drill depths for the steps. The reamer will ultimately finish cut on the entire bore for a short or last shallow cut .... as Harold says - lots of lube and slow speed and feed.

The corrosion resistance appears about equal with 416 and 303. 303 is a more popular free machining SS but McMaster Carr has both in the size rod you may need. (Love that supplier!) As far as eletrolysis goes, it would be a long period of time before any galvonic damage would be detected but bronze should be used over brass for the body.

BC

Where is that pesky Bill Shields with all that know-how and wit?

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Trainman4602
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Re: Injector

Postby Trainman4602 » Wed Aug 30, 2017 8:14 am

If anyone thinks making injectors is easy your are dead wrong. I have been working on mine for a while and have some issues I can get it to work some what but not to my liking. I have about 75 customers waiting and that would mean big bucks but if I take the valuable time to work on it alone then what do I eat chips and I don't mean potato chips.
ALLWAYS OPERATING MY TRAIN IN A SAFE MANNER USING AUTOMATIC AIR BRAKES

BClemens
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Re: Injector

Postby BClemens » Wed Aug 30, 2017 8:50 am

Trainman4602 wrote:If anyone thinks making injectors is easy your are dead wrong.


Whether it is difficult or easy to make an injector is not really the issue. It's amazing what some people will do for entertainment and for relaxation as a part of their hobby. Some people even stuff dead animals.

BC

AnthonyDuarte
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Re: Injector

Postby AnthonyDuarte » Wed Aug 30, 2017 9:32 am

I've toyed with the idea of making cones out of stainless. If you go for it, I would recommend staying away from 400 series and stick with 303 or 316.

Considering the hours we put on our boilers, I don't think the extra trouble is worth it. Brass cones will outlast our models unless they are improperly stored. Perhaps make brass cones to test your design, then once you've settled on your cone geometry try it with stainless. Might save you a little frustration down the road.

If you go through the effort of making an injector, it will most likely work. The question is how reliably, and will it meet the anticipated delivery rate. If you're not planning on going into production, it doesn't really matter if you can make them work the same from one to the next.

And of course it's not easy, but that's what makes it fun, especially for those of us that enjoy this hobby for its challenges.

-Anthony (EE)

Harold_V
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Re: Injector

Postby Harold_V » Wed Aug 30, 2017 3:22 pm

AnthonyDuarte wrote:I've toyed with the idea of making cones out of stainless. If you go for it, I would recommend staying away from 400 series and stick with 303 or 316.

I'd be interested in hearing your reason. 416 is very unlike the balance of the 400 series materials, in that it is free machining. I would agree if you hadn't included 316, or if you were considering 410, 431 or 440C. I'd even include 17-4 PH, which, thus far, has not been included in the discussion.

I have considerable experience with 416 and would choose it over 303S for this application as it is inclined to yield a better surface finish, to say nothing of its rating as the best of all to machine of the free machining grades. Plus, it can be heat treated, to assure longevity of the internal components, which appear to be easily damaged when made of non-ferrous materials.

Am I missing something?

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

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Bill Shields
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Re: Injector

Postby Bill Shields » Wed Aug 30, 2017 4:08 pm

You are not missing a thing Harold:

I am waiting for someone to make a repeatable working injector from brass first.

Irrespective of what has been said before, I have a drawer full of 'worn out injectors' that are perfectly clean, have been well cared-for and just will no work any longer...so these things have a finite life.

Granted, these are smaller scale (3/4 and 1") and tend to be more finicky than the 1-1/2" critters, but the same problems apply...high velocity saturated steam tends to be very abrasive and by very definition, causes significant impact on the 'cones' which causes wear and distortion and a finite life, no matter how well they are cared for.

I ask a question and offer some thoughts:

Historically..how many injector manufacturers sold replacement cones so that you could rebuild your existing unit? I have not yet found a UK supplier that does.

Even the full-size steam eductors (a derivative or predecessor of the injector we use) used in industry (many with stainless steel guts), have a finite life...the supersonic saturated steam just tears them up.

Were this me, and I had a design that I knew would repeatedly work, I would have someone with a little sliding-headstock type lathe crank out a basket full of each part from stainless using carbide tooling and the heck with these silly taper reamers...but as best I can tell, nobody has grabbed that bull by the horns.

That is a business that I am in and irrespective of the material, a bucket of micron accurate parts in virtually any material is a trivial hour or two of work after setup, no special reamers required.

...but you gotta have something that you KNOW works and KNOW the exact dimensions required to start or you can end up with a bushel basket of scrap bucket filler.

I know that Howard Gorin was chasing that windmill for a while

http://themachineryworks.com/catalog/in ... e&ID=21185

I see INJECTOR PARTS listed on his site, but have no idea how successful he has been with the idea.

I am 99% sure they are for an Ohlenkamp design -> and at the price I can guarantee that he has someone cranking them out by the box-full.

If this were easy...my sister would be doing it.

BClemens
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Re: Injector

Postby BClemens » Wed Aug 30, 2017 5:05 pm

Harold V,

I agree with your advice - 416ss is the way to go and you have amply given good reasons why - and it is readily available.

Happy to see Bill Shields inputting here with such gusto. We were hoping for a more informative input from the 'old hat' with plenty of experience in all aspects of this venture to build an injector. The discouraging input from Bill is hard to neutralize for someone wishing to delve into spending some time attempting to build his own device. After all of the grand and freely given and encouraging designs and drawings, why turn from that type of attitude to to this blatent discouragement? And Bill Shields is not the only one - some have the actual axe to grind.

Why are we in the discouraging mode here? A person would think that a guard is being placed against anything promising as if to block any attempt - like infringing on a commercial product. And not just discouraging the attempt but also the means to do it.

How is a 9° bore, ending at the small end at ~.040" going to be bored with a single point boring tool - carbide or not? Please enlighten me... Looks like some folks here are hell bent to discourage the hobby by any means.... The discussion was supposed to gain from, not be told that it can't be done.

If building a steam locomotive was all that easy in the first place, only girls would inhabit the hobby.

BC


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