redmog
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Post by redmog on May 31, 2009 9:31:29 GMT
About 2 thou would be ideal, although it isnt too critical. So, half-a-flat would suffice. Thanks for the advice Alan. I've been looking on the internet for a chart that shows the common silver solders, there melting point, and the correct flux but I haven't found one yet. Chris
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Post by alanstepney on May 31, 2009 12:14:35 GMT
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redmog
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Post by redmog on Jun 4, 2009 16:44:20 GMT
Motion Bracket PositionI've been positioning the motion bracket. The expansion link support hole is 1/2" forwards of the reverse rod shaft. It would be difficult to measure the position because the wheel is in the way. I overcame this by turning down a couple of pieces of 1/2" AF hexagonal to be a good fit in the bore of the reversing rod hole and the motion bracket, then held them together in the correct position while I clamped the bracket. Chris
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redmog
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Post by redmog on Jun 7, 2009 20:15:09 GMT
Fabricating Motion BracketsWell - I don't seem to be getting on very quickly. Trouble is, I bought a new camera on Friday and spent most of Saturday working out how to use it. I've been dying to use it to upload a progress photo to see the results. Here goes - I'm still shaping and fabricating the Motion Brackets because I'm a little disappointed with the castings I had from Reeves. Just a clean up now and I should be ready to silver solder them up this week. Shaped most of the end plates on the rotary table. One left hand - one right hand. Chris
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ace
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Post by ace on Jun 8, 2009 20:48:01 GMT
great work mate, hope you can solder them together and retain that pro finish. I am just starting to manage to solder joints and be proud to show then off, well most of them. Its great to watch someone elses progress, inspires me to on building mine.
steve
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redmog
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Post by redmog on Jun 8, 2009 21:29:41 GMT
Thanks ace.
Don't forget, I'm following your progress also.
Chris
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ace
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Post by ace on Jun 8, 2009 21:42:35 GMT
after a weekend mountain challenge for Wateraid in the lake district I am going to be recovering for the next week, so the loco is on hold....... well until I can stand up again that is.
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redmog
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Post by redmog on Jun 13, 2009 20:25:43 GMT
Check Your BricksI might have built three successful 5" gauge boilers in the past. All of which are still in service and regularly tested, but I had a bit of a shock this week. Because I couldn't get on and finish my motion brackets I was looking for something to do. I decided to do a few small boiler parts - the firebox girder crownstay, even though I'm not ready for it. After silver soldering it at about 660 centigrade look what I found! There must have been a foreign metal on the firebrick- pewter. It's caused an aggressive reaction with the copper and eaten into it by about 1/64". Good job it wasn't the boiler barrel. So the pewter caused the copper to melt at 660 degrees ish. No - I don't understand about eutectic and the like. Any metallurgists out there who can explain the reaction between pewter and copper at 660 ish degrees. Before emery cloth - After emery cloth Thanks Chris
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simonwass
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Cecil Pagets 2-6-2 of 1908. Engine number 2299. Would make a fascinating model....
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Post by simonwass on Jun 13, 2009 22:52:33 GMT
This is why you cant silver solder a boiler which has been sealed with comsol. No idea on the reaction which takes place.
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redmog
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Post by redmog on Jun 19, 2009 10:04:30 GMT
Thin Boiler BarrelI've been looking at the drawings of the boiler with the intention of seeing what materials I already have in stock and what I need to 'price up' and 'keep a lookout for'. eg. barrel tube. I'm very surprised to see that the Barrel and Inner/Outer Wrappers are only 16 gauge. This seems a bit thin to me for a 4 1/4" barrel working at 80psi. I welcome any thoughts from experienced boiler builders. Thanks Chris
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Post by alanstepney on Jun 19, 2009 11:29:39 GMT
Without checking, my GUESS (and it is only that) is that 1/16" (which is roughly what 16SWG is) would suffice, but even so, if I were building it, I would certainly want something thicker.
As the front plate and backhead are 1/8", I would go for the same for the rest of the outside, or at the thinnest, 12SWG (100 thou).
I can work out the strength of 16SWG if you wish, but it would still not be my choice.
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redmog
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Post by redmog on Jun 19, 2009 11:34:51 GMT
Thanks Alan.
I don't want to trouble anyone in performing calculations for me. If I knew the formula or whatever I could probably work it out myself. Where are these formulae to be found? Or is it more complicated than that!
Chris
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redmog
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Post by redmog on Jun 19, 2009 14:35:48 GMT
Formula Found. I found this formula in one of Martin Evans books. If I've got my facts right, it works out to a safety factor of 7.35, which surprises me. If any of the knowledgeable wish to check my outcome for a 4.25 dia. 16 gauge boiler barrel - I'd be happy to be corrected. Thanks again Chris
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simonwass
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Cecil Pagets 2-6-2 of 1908. Engine number 2299. Would make a fascinating model....
Posts: 472
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Post by simonwass on Jun 19, 2009 14:49:19 GMT
I get same result on an excel spreadsheet I downloaded from somewhere. I did think it was a bit thin but 7.3 is a good SF so go for it. If you use 1.5mm its still 6.9 SF. Try to fit a flanged throatplate to barrel join if you can, a flanged firebox 'frontplate' to combustion chamber join would also be nice but a good fillet is better than nothing. Its a weird boiler as a combustion chamber is normally an extension of the inner firebox wrapper not a squashed tube silver soldered in. If you are not making a scale machine a bigger firehole would be useful, its about the size of a Tich firehole! Good boiler though and a Bantam Cock is a lively machine.
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redmog
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Post by redmog on Jun 19, 2009 15:15:26 GMT
Thanks for Checking. I get same result on an excel spreadsheet I downloaded from somewhere. Good boiler though and a Bantam Cock is a lively machine. Thanks for backing up my calculations and your good advice. I'd noticed that the firehole is small, and had thought about increasing the size. Easier to fire and I like to be able to see the fire roaring away - part of the fun! Chris
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Post by baggo on Jun 19, 2009 15:41:50 GMT
I'd probably go to 13swg (3/32" or 2.5mm) for the barrel and outer wrapper, if only to make it less susceptible to accidental damage when it's soft after soldering. There's also the added bonus of a bit more weight on the drivers! LBSC designed a few boilers using 'squashed' tube for the combustion chambers. You can download a useful spreadsheet for boiler checking here: calslivesteam.org/calculations/Calculations.htmThat's probably the one that Simon's used. I use it all the time. I'd look at the staying of the firebox as well and possibly reduce the spacing and/or increase the diameter of the stays (But hey, what do I know about boilers ) John
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redmog
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Post by redmog on Jun 19, 2009 16:24:17 GMT
Useful Advice. I'd look at the staying of the firebox as well and possibly reduce the spacing and/or increase the diameter of the stays (But hey, what do I know about boilers ) John Thanks John It's all useful advice . I shall probably go for 5/32" snap head copper rivets for the stays, but that's a long way off yet. Chris
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simonwass
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Cecil Pagets 2-6-2 of 1908. Engine number 2299. Would make a fascinating model....
Posts: 472
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Post by simonwass on Jun 19, 2009 18:21:23 GMT
Yep thats the one - boiler.xls Contains a few other useful spreadsheets, a draughting guide and one for tractive effort.
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redmog
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Post by redmog on Jun 19, 2009 19:43:17 GMT
Slight Brain Blockage. Yep thats the one - boiler.xls Contains a few other useful spreadsheets, a draughting guide and one for tractive effort. Useful spreadsheet. But I still don't understand - 'Staybolt Pitch (larger dimension if not square)' Chris
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Post by alanstepney on Jun 19, 2009 20:21:39 GMT
The pitch could be rectangular, instead of square.
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