Blackgates Standard Injectors: Combining Cone Removal

[n269580]

Hi Everybody,
I hope someone can help me here.

But I have two Blackgates Engineering Injectors (No.4 and No.5) but want to remove ALL the cones as would like to use them in a new body design to suit my 7 1/4 LNER N2. 
The injectors are the hexagon body type.
(I have depth mic the length down to them so know what to set them to.)

Does anybody know if the combining cones (middle ones) are:

Pressed against a shoulder (In both directions)
Just a push fit into the body
Or another way that I have not thought of!   

If I cannot remove them, does anybody know of a drawing for the cones so I can make some instead?

Any help would be gratefully received. 
Many thanks everybody

Bruce Harvey,
24 year old, average model engineer 

7 1/4 Inch Gauge LNER N2 builder (Almost finished!! After 5 years) 

[flyingfox]

Hi Bruce, they are often "locktited" in, but most often a press fit.
I would think a new set based on data from DAG Brown's injector book is the best way to go.
Love the N2.
Regards
Brian

[uuu]

You could consider cutting the body away?

Wilf

[oldnorton]

Hi Bruce

We all admire your willingness to have a go and modify something, and will offer as much help as we can, but if you try to take the combining cones out of the Blackgates injectors they will be finished (wrecked) and you will be very unlikely (have no chance) to position them correctly in a new body. Injector insides are sub-thou critical devices.

The only constructive thought I have to offer is to read everything you can find about building small injectors, plus a few threads on here, and then have a go at making the whole thing from scratch if you are really keen. Expect to invest at least 2 months effort and time. If you do it you will rightly deserve the applause of us all. I apologise if it sounds like a put-down, it is not meant to be, but just a reality check to help you not get frustrated. I have never built an injector, but I have done the reading and realised that the fascination of building my own will have to wait until the current one hundred jobs are finished!

Norm

[Cro]

For reference these are Bruces' Injectors to be all to his own design.

Untitled by Adam Cro, on Flickr

Norm I said similar that I fear they would be no good after extraction but if he could try the body of the existing injector down to be the sleeve in these bodies he could be onto a winner. Failing that having a go at the cones from a published design.

Adam

[jma1009]

Hello Bruce,

You ream through the injector body on your commercial example. You press in the rear half of the combining cone, then you press in the front part of the combining cone in this type of design. Both have to go over openings in the injector body during this process, and is to tenths of thous tolerance on the body bore. The combining cone parts themselves are made slightly undersized and re-reamed in situ.

Pressing out the combining cones is fraught with problems to insert into a new injector body. I've attempted it quite a few times, and not with any degree of success. One example - the best working example of these attempts - was 'splashy' at the overflow continuously throughout the range - indicating the combining cones were not concentric with one another. And far from the performance I would regard as acceptable.

Subsequently, I have always taken the view that putting old combining cones in a new body, or putting new combining cones in an old body is always going to be unsuccessful, and DAG Brown was of the same view, and that they would be 'bin' jobs.

Cheers,

Julian

[n269580]

Thank you everybody for your comments.
It know looks like I will skip the idea and hopefully someone I know is going to look into designing new cones.
Which might be easier.
But there again, probably very tricky to make.

Cheers
Bruce