uuu
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Post by uuu on Sept 12, 2014 19:23:08 GMT
Is there a particular reason why steel isn't used for the door? That's what I was going to use for SPEEDY. Perhaps it's in anticipation of model engineers having weedy machines that are more comfortable with softer materials? Extrapolating also from the preference for castings over machining from solid. I'm just guessing here. Steel would perform just as well in use. Wilf |
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Post by Roger on Sept 12, 2014 20:47:09 GMT
You could be right. It's not the easiest thing to hold in any case and it's likely to chatter like mad. I'm not sure of the approach I'm going to take on that. I might just machine it from a slice of solid mild steel bar and use the Mill as a CNC lathe again. I'm thinking that the inside can be done first and then silver soldered to a mandrel so the front can be turned.
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jma1009
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Post by jma1009 on Sept 12, 2014 21:10:27 GMT
hi roger,
i already had an old gunmetal casting for the smokebox door albeit of larger size. 'waste not want not'!
thanks pete and david for your very kind comments.
cheers,
julian
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dscott
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Post by dscott on Sept 14, 2014 23:17:00 GMT
I have had great success with forming out of steel sheet using the dreaded MDF in compression using a press. Then cutting them out on a mill like cutting round like a saucer clamped down. I do all my boiler plates this way as well it just makes a neater job.
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Post by Roger on Sept 15, 2014 9:04:24 GMT
Now that's interesting. Presumably you make a male and female shape of the part you want in MDF?
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dscott
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Post by dscott on Sept 17, 2014 6:18:29 GMT
I just did a male shape for the door and a hole in the sheet for the other. I then lined the two up with built up sides like a picture frame to stop them moving and pressed in a local garages press from 1.6mm. You do tend to get a fold but a few bashes with a hammer helps. Wonderfully you don't get any turning marks I must dig them out and do some photos!!
I have a long list of sheet metal forming s to do including the fire-hole flap, wash out covers and the oil pipe cover from the boiler to the smoke-box as per all Great Western locos.
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Post by Roger on Sept 17, 2014 6:46:54 GMT
Thanks for that, I might give that a try. I've got a 3D model of it so I can turn a male and female former on the mill like I've done for other items using it as a lathe. That would be a lot lighter duty than machining steel that way. I could also anneal the sheet half way through the process.
The other possibility of course is to spin the shape if it's only 1/16" sheet. That ought to be possible but of course that would have the same issues with circular marks. I really like your press tool idea, it's an interesting alternative to the usual method.
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jma1009
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Post by jma1009 on Sept 20, 2014 20:24:22 GMT
a bit more progress! rolling the smokebox wrapper and turning the front and rear rings took very little time, but ive had to spend quite a bit of time getting the bottom of the smokebox to fit around the exhaust manifold and steam pipe, and then fit a doubler plate to the saddle and repeat the above... anyway the saddle plus doubler and bottom of the smokebox is all finished and a coat of grey primer on the saddle. compared to previous pics of the saddle ive added a curved strip on the front as per prototype. the saddle is quite an elegant affair - no doubt the pen of Basil Field, Marsh's chief draughtsman, and quite distinctive, as are most terrier parts! as no casting is available for the A1X saddle mine is fabricated out of 10 parts cheers, julian  |
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jma1009
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Post by jma1009 on Sept 20, 2014 20:33:14 GMT
my digital camera doesnt seem to like pics taken in anything other than daylight at the moment but this one seems to have come out quite well - shows the rear of the saddle plus all the studded glands to the piston rods and valve rods and the Stroudley type channel section slidebars plus the oil pots on the case hardened slidebars with 12BA bolts! cheers, julian  |
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Post by Roger on Sept 20, 2014 21:03:54 GMT
What a shame all that lovely motion won't be visible! Is that the final diameter of the hole in the front of the smokebox? That seems very small.
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jma1009
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Post by jma1009 on Sept 20, 2014 21:20:16 GMT
hi roger,
the front ring is turned to an ID of 2 13/16". that is pretty much scale measured off fullsize last october! the boiler barrel is only
3 3/4" dia on a 5"g terrier. i have made the smokebox OD and smokebox door OD to scale, which is quite a bit more than martin evans drew these parts!
the motion is quite visible underneath the boiler before the side tanks start, so isnt quite as hidden as you might imagine, not that this was a consideration in any event!
cheers,
julian
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Post by Roger on Sept 20, 2014 22:45:17 GMT
I didn't doubt for one minute that it wouldn't be right, I was just surprised. I'm please at least a little of your work underneath will be seen after all that effort!
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Post by Deleted on Sept 21, 2014 11:34:12 GMT
very nice Julian...love the motion...so much going on...picking up on Roger's question are you having the front ring removable for access?...I ask as Know what a pain it is on my 4470 which is much bigger....admittedly my hands have a number of issues now which means I can't clench them fully so can't get in the smokebox. I'm hoping that 4472 being so much bigger will make life a lot easier for me, currently any work needed in 4470's smokebox requires help from one of my boys....mind you it's a good way of instilling interest for when I leave this mortal plain...  Pete |
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Post by Jim on Sept 21, 2014 11:57:15 GMT
Hi Pete, As a follow on I made my smoke box ring a push fit into the smoke box for ease of access. I would imagine the diameters would be fairly similar.
Jim
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Post by donashton on Sept 21, 2014 16:59:43 GMT
Jim, you are lucky to be able to make the whole front of the smoke box pull out of the barrel. Most GWR engines had a step riveted to the barrel, so you cannot remove the door and ring without some real ingenuity!
Don.
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jma1009
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Post by jma1009 on Sept 21, 2014 20:05:01 GMT
hi pete,
as you might expect i have my own strongly held views on such things. my smokeboxes are removable from the boiler and my smokeboxes dont have any removable bits, apart from the petticoat pipe. all the innards are arranged to be 'easily' accessible with a spanner (though resort to a specially made spanner sometimes). there is no need to have the front ring removable - this isnt fullsize practice and ruins the paint finish!
cheers,
julian
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Post by Roger on Sept 21, 2014 20:31:11 GMT
Hi Julian,
These things are not at all obvious to us newcomers and it's very useful to note the way you make the smokebox removable. I wouldn't really have given that much thought but now it's obvious that a locomotive needs to be accessible to maintenance and repair. I'll certainly be planning the smokebox with a view to making that come off now I have this useful nugget of information.
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Post by Jim on Sept 21, 2014 20:55:35 GMT
hi pete, ..this isnt fullsize practice and ruins the paint finish! cheers, julian I can remove my smoke box door ring without any damage at all to the paint. Admittedly it's not something I do unless it needs to be done. As Don says I think it depends on the particular model. Jim |
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jma1009
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Post by jma1009 on Sept 21, 2014 21:05:39 GMT
perhaps i should add a few extra words of explanation - if you look at the above pic, the blastpipe screws into the top of the exhaust manifold, and the steam pipe into the cylinder block is in front. by lifting the boiler slightly with smokebox attached, the smokebox base clears both the above and can be slid off the boiler - being a push fit onto the front of the barrel with a smear of sealant for good measure. the only time this would actually be required would be if the superheaters needed replacing. (for sliding off the smokebox the blower ring union connection and snifting valve union and steam pipe union need undoing but all 3 are easily accessible with a spanner from the smokebox door opening - though my steampipe is at the front of the smokebox and front of the cylinder block specially for this purpose, unlike the martin evans drawings).
the base of the smokebox and doubler plate on the saddle are a very close fit around the exhaust manifold and steampipe. the steampipe is threaded all the way down, and a nut to suit same plus curved washer secures the smokebox to the saddle very securely. no other fixing of the smokebox to saddle is required.
in fullsize the smokebox is riveted to the saddle but this isnt necessary in miniature.
cheers,
julian
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Post by Jim on Sept 21, 2014 21:42:00 GMT
I see what you mean Julian, that is a very neat solution for the time when maintenance work is needed and shows the benefit of careful forward planning. I try, not always with success I might add, to arrange things so that access can be gained while maintaining the appearance of the prototype. It's not always possible though and easier access isn't an option if the appearance of the prototype is to be maintained. Back on task, progress on Boxhill is looking very good indeed and I must say I like your hand crafted backhead fittings, very nice Julian  Jim |
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