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Post by Deleted on Mar 19, 2015 23:12:37 GMT
(1) Need to distinguish between a kit for a realistic locomotive with full functionality and a kit for a more toylike locomotive with much simplified functionality .
(2) The more toylike locomotive could be fun for many people to build and run so we won't make mockery of the idea . Point though is that such a locomotive could to some extent resemble a real engine but be designed quite differently .
Worth noting at this point that kits for electrically driven Diesel outline locomotives have very few parts . Our toy type steam locomotive kit should have similarly low number of parts .
This then gives rise to the concept that an actual steam engine need not
be much different in layout to an electrically driven engine .
The 'engine' is a packaged unit construction steam motor - just like an electric motor .
Boiler is a packaged unit construction steam generator with minimal fittings .
Chassis and scantlings are just plate cuttings and a few bent bits . Wheels et al would be machined properly but there would not be any valve gear except optionally dummy .
The whole lot then goes together without need for major adjustments or need for significant skill .
This therefore is a kit engine designed specifically for the purpose and not just adapted from an LBSC problem engine .
(3) The more complex full function engine would have to be designed as a proper engineering job from day one to be successful . I suggest that the costs involved would make kits for any larger engines unviable .
(4) A major problem with all kits is the assembly instructions . These have to be very comprehensive , clear , well illustrated and assume no prior knowledge from the reader . To do this properly is again a major exercise and would add considerable to costs .
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Post by joanlluch on Mar 19, 2015 23:14:42 GMT
John you do like keeping things on topic  as a nice side note it has its relevance in modern manufacturing that ties in with additive manufacturing but I think maybe best left now or carried on in your thread possibly Joan. All I will say is as it is your first loco I would have possibly gone for something simpler in published design, doesn't mean you can't try producing it in the same way you are now but at least you know the theory behind it is proven. Back to 3D printed stuff....I am going to be looking into some lost wax stainless castings soon for a 5" Duchess using 3D printed patterns, anyone had experience with casting stainless? Adam Hi Adam. I am more on designing things (even if just "adaptive" design) than on anything else. That's the reason why something else does not appeal me. About casting stainless, I am not sure if you mean melting it into a mould, or direct 3D printing of it. If it is the later, I am considering ordering a simple part from Shapedways just to learn how it goes. |
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Post by simplyloco on Mar 19, 2015 23:18:20 GMT
I have no wish to be seen as or act as a moderator, but shouldn't this discussion be held in your own 'informells' thread? After all, this thread was started as 'additive manufacturing' and looks like getting clogged up again... John Well maybe. This is why I offered to open a new tread only to share 'bad' experiences (see one or two posts above). I do not think that this applies particularly to my build, although of course that would be useful to me. If you have something more to add, please start something such as "'kit' issues and other bad experiences" or something to that effect. Thanks Very sorry, but as you are convinced that your design is perfect, I have no bad experiences to add that would be useful to you, or anything else to that effect... John |
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Post by RGR 60130 on Mar 19, 2015 23:19:00 GMT
Back to 3D printed stuff....I am going to be looking into some lost wax stainless castings soon for a 5" Duchess using 3D printed patterns, anyone had experience with casting stainless? Adam I think I remember Abby (Dan) on this forum doing some crosshead castings for a 7 1/4" gauge B1 in stainless steel. I think they were done using a lost wax process. Reg |
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Post by simplyloco on Mar 19, 2015 23:21:44 GMT
Back to 3D printed stuff....I am going to be looking into some lost wax stainless castings soon for a 5" Duchess using 3D printed patterns, anyone had experience with casting stainless? Adam I think I remember Abby (Dan) on this forum doing some crosshead castings for a 7 1/4" gauge B1 in stainless steel. I think they were done using a lost wax process. Reg We don't see much of Dan these days: I do hope all is well in that regard? John |
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Post by joanlluch on Mar 19, 2015 23:24:49 GMT
Well maybe. This is why I offered to open a new tread only to share 'bad' experiences (see one or two posts above). I do not think that this applies particularly to my build, although of course that would be useful to me. If you have something more to add, please start something such as "'kit' issues and other bad experiences" or something to that effect. Thanks Very sorry, but as you are convinced that your design is perfect, I have no bad experiences to add that would be useful to you, or anything else to that effect... John I meant that discussing about bad experiences was not particularly related to my (or any) particular build. I did not imply that my "design is perfect". I actually stated the likelihood of being the contrary if you care to read my posts. BTW, where is the "unlike" button? |
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Post by RGR 60130 on Mar 19, 2015 23:25:26 GMT
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Post by Cro on Mar 19, 2015 23:28:21 GMT
Thanks for that, very interesting. Hoping to do some motion brackets I think, not entirely sure till I see the guy! Adam |
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Post by Deleted on Mar 19, 2015 23:40:24 GMT
Need to be careful to choose right type of stainless steel but in general it casts beautifully and normally no problems .
Few things to mention though . Parts for lost wax casting have to be designed with some of the strengths and limitations of the process in mind .
If you consider how you would design a part intended for simple sand casting and apply same thinking to lost wax casting you won't go far wrong . Things like need for sections to change uniformly and no large lumps attached to thin sections etc .
Another thing is the question of machining allowance . Lost wax castings can be made dead size after a bit of experience of the process and adjusting for shrinkage etc . Generally though best to have a small amount of machining allowance on any sliding surfaces such as on a crosshead .
Purely out of interest I made the pattern for the cross head on Neville Evans Grange as well as many patterns for his other engines .
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Post by Cro on Mar 19, 2015 23:58:00 GMT
Michael,
Machining allowance is an interesting one. So I have now done the LMS brake valves (sorry I keep using these as examples) in both 5" and 7 1/4" the only real machining on the body is boring out the valve bore for the steam brake, in the 5" one I made the casting hole 1/16" and it's finished size was an 1/8" the 7 1/4" one the finished size is 5/32" (I think) and I have made the cast hole size 0.14" so a lot less machining allowance on this but because the casting quality in Lost wax is so good I shouldn't have a problem.
I have recently done the BR manifolds now these are a bit different, the square faces for some of the fittings need machining to get a good sealing surface, the edges are radius-ed to help with the patterns/casting and the machining allowance on these is the thickness of the radius.
I have found though that the boss for threading fr the boiler has come out about 10thou under size which is a bit of a pain so will be chatting to Mike about our shrinkage allowance.
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jma1009
Elder Statesman
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Post by jma1009 on Mar 20, 2015 0:01:01 GMT
hi michael,
i think the Neville Evans castings in stainless are quite superb! very interesting to know now that you made the patterns!
cast stainless seems to have considerable advantages these days. i would be very interested to learn more both about it's characteristics and why very fine castings can be produced with it whereas these days lots of other castings are frankly rubbish!
cheers,
julian
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Post by 3405jimmy on Mar 20, 2015 7:43:47 GMT
I have no wish to be seen as or act as a moderator, but shouldn't this discussion be held in your own 'informells' thread? After all, this thread was started as 'additive manufacturing' and looks like getting clogged up like all the others... John I wish someone would start a thread to discuss the use of endless threads that wander way off topic |
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Post by joanlluch on Mar 20, 2015 8:49:43 GMT
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Post by ejparrott on Mar 20, 2015 10:23:28 GMT
My friend Paul is is working on a Class 70 in 5" has been looking at having the bogie side frames cast in stainless. Now I'm not 100% certain, but I'm sure it's 316 he's been talking about. Reason being that it's the most commonly used, and because the straight parts that hold the frames apart can be made from ordinary bar stock, and the lot can be welded together with no worries about dissimilar metals.
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44767
Statesman
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Post by 44767 on Mar 20, 2015 20:59:01 GMT
Back to 3D printed stuff....I am going to be looking into some lost wax stainless castings soon for a 5" Duchess using 3D printed patterns, anyone had experience with casting stainless? Adam Dave Noble had the Buckeye couplers done in stainless steel. You could get in touch whith him about it. I do know that stainless steel casts very well and so for small castings it is ideal. |
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Post by Deleted on Mar 20, 2015 21:26:59 GMT
I made many patterns for lost wax castings a few years ago . Most for Neville Evans when he was working on his own and some for PME . Most of them ended up at PME in the end . Also did some for myself and some for industrial applications .
The crosshead pattern was designed so that however shrinkage went - within a narrow band of acceptable variation - the casting would always be dimensionally acceptable and always have enough machining allowance . Measured some up afterwards - in stainless shrinkage was consistently in the 0.9% to 1.1 % region .
Pattern I was most proud of was for the Grange tender axleboxes .
Stainless steel of the right grade is very fluid when molten and will flow easily into fine detail . Mild steel is a little less fluid and materials like phos bronze are like treacle .
Those with 3d printer capability should certainly make use of them but there is no problem at all making lost wax castings starting from a hand made pattern . Best to use metal but Tufnol is ok .
Metal pattern is embedded in a synthetic rubber mix and when set the rubber mold is used to make the waxes .
If you want to make lots of identical parts or particularly high precision parts then you can make a metal mould instead of pattern and bypass the rubber mould stage .
Wax is then embedded in a special liquid ceramic material which when hardened forms the actual casting mould . Wax pattern is then burnt out leaving a clean casting cavity the same shape as pattern .
It is perfectly possible to make simpler lost wax castings in home workshop . Intricate and higher quality lost wax castings though require a vacuum or centrifugal casting rig to force molten metal into all crevices of ceramic mould .
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44767
Statesman
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Post by 44767 on Mar 21, 2015 9:06:14 GMT
I have recently done the BR manifolds now these are a bit different, the square faces for some of the fittings need machining to get a good sealing surface, the edges are radius-ed to help with the patterns/casting and the machining allowance on these is the thickness of the radius. I have found though that the boss for threading fr the boiler has come out about 10thou under size which is a bit of a pain so will be chatting to Mike about our shrinkage allowance. Adam, I have checked the two castings I have here. One is within 0.05mm of the required size (nominally 70.07mm on the model) which suggest that the shrinkage allowance is correct. The other done by a different foundry is, as you have found, about 0.2mm under size on the boss for the thread but also 0.2mm under nominal size for the length. This raises the question "is this a shrinkage problem or is it the whole surface reduced by 0.1mm per side?" I don't know. What you have to understand is that these are still castings and different areas of a casting will shrink at different rates so there is a lot to consider. Shrinkage allowance will largely take care of the size but you must still add a machining allowance to parts which need to be machined to a good finish and where the size is important. We will have to add machining allowance to the boss for any future ones. Mike |
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Post by joanlluch on Mar 21, 2015 9:25:51 GMT
Hi Michael, your post above on the lost wax process was very informative.
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Post by Cro on Mar 21, 2015 9:38:42 GMT
From Mike
"What you have to understand is that these are still castings and different areas of a casting will shrink at different rates so there is a lot to consider. Shrinkage allowance will largely take care of the size but you must still add a machining allowance to parts which need to be machined to a good finish and where the size is important. We will have to add machining allowance to the boss for any future ones. "
Mike,
I suppose I hadn't really thought about it like that and in hindsight I should have done them with a bit of machining allowance on them but knowing they would be a tricky item to set up I was hoping finished size could be threading side. I may do them in the future without the boss as it may not always suit everyone for size anyway. (One is already up in the lathe on the 4-jaw to have a sleeve fitted, I couldn't help starting when I got home last night!) thanks though im still very pleased with them :-)
Adam
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Post by Roger on Apr 1, 2015 7:21:56 GMT
I've just seen this Tiko 3D printer which is novel in the field of printers although the idea has been around for years for other things. This is a crowd funded project but it looks like it's well developed already and it's certainly going to be cheap when it's available. The precision is down to 50microns so it's better than many that are out there. Anyway, I thought it was a well designed and engineered product that might be of interest. |
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as a nice side note it has its relevance in modern manufacturing that ties in with additive manufacturing but I think maybe best left now or carried on in your thread possibly Joan. 
