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Post by Cro on Jan 30, 2015 19:58:05 GMT
hi adam and ben, i had a beautifully made petticoat pipe of the combined blower ring type for a 3.5"g LMS Duchess, but i doubt very much if it would have been effective, and would also have mucked up the draughting if at anytime the blower was turned on whilst the loco was moving under steam. the laurie lawrence 4 jet blower fitting to go round the blastpipe nozzle cant be beaten for effectiveness and simplicity IMHO. cheers, julian Julian, this is for the vacuum ejector not a blower..... Adam
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44767
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Post by 44767 on Jan 30, 2015 22:24:00 GMT
I don't know the ins and outs of casting in great detail but the one in the pic I posted had 2" holes around the ring which when finished were tapped and had washout plugs fitted which were then ground flush (this can just be seen in the pic). Mike, could this not be done in miniature as the way of getting the wax out? Cheers Ben Ben, these features would have been the core prints for the void in the ring. They are the equivalent of the "frost plugs" in a car engine. Just to explain how the support wax is removed- the whole part is put in isopropyl alcohol which is heated to about 45 degrees. This dissolves the support wax but it needs to be rinsed away as it dissolves so that the alcohol gets at the rest of the support. In a confined space I doubt that all the wax would be removed and it would be difficult to tell. I would recommend casting from printed waxes in two halves, split where you see the seam, then cast and soldered together. I had thought of welding the two waxes but you'd have the same trouble trying to get out the investment material from inside the ring. Mike
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jma1009
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Post by jma1009 on Jan 30, 2015 22:30:58 GMT
hi adam, thanks for the above clarification. however my point about the jets upsetting the draughting still apply. i have a vague recollection that with double chimneys the exhaust from the vacuum ejector is arranged to go up a separate hole in the casting so not impinge on the draughting whilst it is doing it's business in the petticoat pipe. plus on a single chimney the vacuum exhaust pipe should go pretty much to the top of the chimney. these comments particularly apply to locos with large diameter smokeboxes and short chimneys such as ben's V2 and pete's Doncaster where the draughting is not not ideal and in the case of the martin breeze V2 rather poor. cheers, julian
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44767
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Post by 44767 on Jan 30, 2015 22:47:03 GMT
But Julian, these are not jets as such. They are set in the venturi to draw the air out of the vacuum pipe. It doesn't use live steam.
Mike
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jma1009
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Post by jma1009 on Jan 30, 2015 23:10:51 GMT
hi mike, you raise a very interesting point. the 'modern' understanding of how locomotive draughting works has undergone a bit of a revolution in recent years and i am far from sure that what you state will in fact happen as opposed to my view of the draughting being disturbed. my own experiments with the vacuum exhaust plus fitting of vacuum equipment to my locos is that the steam exhausts out of the vacuum pipe from the ejector at quite a force - sufficient to upset the draughting if not properly arranged. jos koopmans has published extensive research on the way pressure changes in a chimney/petticoat pipe, and i will need to recap on his writings. cheers, julian
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jma1009
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Post by jma1009 on Jan 31, 2015 0:11:15 GMT
a bit of an update, and a bit of eating humble pie on my part...
jos koopmans has very kindly replied to me specifically on the point mike raised and agrees with mike.
so i shouldnt have discarded that LMS Duchess petticoat pipe all those years ago!
i am very grateful to mike for questioning my earlier post as i have learnt something valuable as a result.
cheers, julian
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Post by Cro on Jan 31, 2015 0:29:14 GMT
Julian,
Glad you have found an answer, it did get me thinking but I also on the other hand thought that if it were the case it would cause such an issue how would it have worked on the full size as this is what I am modelling it off,
Currently just working on some other items, might open another thread to share some of these
Adam
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44767
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Post by 44767 on Jan 31, 2015 0:36:32 GMT
I didn't like to question you Julian as usually someone would shoot me down in flames! This time I thought you must have been mixing up live steam vacuum ejectors with this one which uses the exhaust blast. Always a wealth of knowledge here and someone usually has the correct answer. Nice to have it confirmed by your source.
Mike
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Post by Deleted on Jan 31, 2015 1:25:56 GMT
Mike this type doesnt use the exhaust blast, it uses the same type of live steam ejector as most engines, on the standards and most LMS engines the ejector is next to the smokebox rather than than in the cab.
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44767
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Post by 44767 on Jan 31, 2015 2:35:37 GMT
There you are- shot down in flames!
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Post by Deleted on Jan 31, 2015 14:23:58 GMT
Sorry mate
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Post by Cro on Mar 5, 2015 23:47:23 GMT
A small update, whilst I wait for some drawings to carry on with my BR items we have been doing a few test prints for the 7 1/4" version for these brake valves and here is the first pictures of the vacuum valve disc with the holes all printed. These show the holes in the front face and edge and the supporting frame placed around the part for strength and handling as these waxes are very brittle. Hopefully two versions of this will go to the foundry in the next few days, the difference in the versions is the arrangement/size of the holes to see which is most practical and realistic. Also finished off the model for a dummy 3 1/2" gauge version, need to check some thickness's on this before printing but hopefully most will be ok Adam
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Post by Cro on Mar 10, 2015 16:10:17 GMT
Some more progress from across the pond on the valves, the version mentioned above (3 1/2" version) was printed and its looking good, a different version is now being printed with sprus ready for the foundry Now back with the 7 1/4" version the main body has been printed to check the internal porting for casting. This version and the porting is an exact scale of the full size version meaning it should be easier to manufacture than the previous version. We cracked open the body to see the porting and to check if we were going to be able to remove the investment after casting - we have a few options to try so next step its to cast one and see what happens. Adam
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Post by Cro on Mar 15, 2015 15:01:06 GMT
Another update as castings start to appear, I know a lot of it is much of the same and not had much response but thought I'd keep sharing. So last two prints for the prototype casts in 7 1/4", the main body again after making some modifications allowing us to remove the print support material ready for casting and another variation of the valve Disc with a different arrangement of holes to try get the best looking/practical combination. So the two valve discs with all the holes cast in place and the extra detail not available on the 5" version, this will make manufacture a lot easier and quick (I have orders for these so far counting up to a batch of 20 so far so time is money!) Also a little extra detail with the hooks being cast, I have a feeling these will be a little thin so I may make them a bit thicker just to be on the safe side. Hopefully have all of the prototype castings will be done by Wednesday. Now we know a few other limits of the printer and foundry a few extra bits will be done on the 5" to help improve that slightly too. Cheers, Adam
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Post by Cro on Mar 18, 2015 20:42:40 GMT
Another one with more castings The first prototypes have now been done and are on there way to the UK, here is a set of 4 I will have to work on over Easter, we managed to get the internal porting correct as per full size and can just be seen in the second photo. Adam
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jma1009
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Post by jma1009 on Mar 25, 2015 22:45:50 GMT
there is an excellent picture and praise for adam's vacuum fitting in the april EIM. very well deserved credit methinks! cheers, julian
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Post by Cro on Mar 26, 2015 0:14:58 GMT
Julian,
Thanks, glad it got noticed! Will be back in the workshop Sunday, one I have done a few manifolds I will be cracking on with the brake valves again, a week of daily updates coming from me!
Adam
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Post by Cro on Mar 27, 2015 19:50:11 GMT
Was having a bit of fun with the render tools in SolidWorks whilst doing the drawings ready for next week, Thought it looked quite good! Adam
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Post by Cro on Dec 9, 2015 18:06:28 GMT
Been a while since I wrote anything here for this thread so bit of an update is in order. It is just over a year since I started this thread and just under a year since I started machining the first one. As most of you have seen I have been working hard on all my other fittings so these got lost in the crowd a bit but there has been some interest so I felt I should get some more castings in and have another go on the 5" version to see if I can really get the combination to work. The most time consuming part before was obviously the Vacuum valve disc as it was made as an assembly and having 96, 0.3mm holes in it made it tricky to machine but Mike has worked his magic on the model and we have managed to print and cast them now saving me a lot of time (and drills). The main body has stayed much the same as I feel there wasn't much room for change on that front but I will be working on the steam brake port design to try and limit it slightly so that I can get a greater ratio between the surface area of the steam brake valve and the piston in the vacuum chamber. Here are the new castings fresh from the foundry And the new Vacuum Valve discs now printed and cast with holes and a little extra detail I couldn't produce before. The only thing missing from the full size version is the small hook! Just to remind you what the first one looked like It's going to be a busy christmas again! Thanks, Adam
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Post by Roger on Dec 9, 2015 18:32:38 GMT
I'm still amazed that you can get that level of detail with this process, they're stunning. It's hard to imagine where this technology is going to be in 5 or 10 years time when this is what they can do already.
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