uuu
Elder Statesman
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Post by uuu on Jul 7, 2022 14:59:06 GMT
I'm encouraged by your experience, as I have CI cylinders on Jessie and, if I ever get to finish it, is likely to have periods if inactivity.
Ken Swan wrote this in 1971 about his experience with Bridget, I suppose a more heavily-used engine: "About this time there seemed to be a lot of discussion about rusting up and pitting of iron cylinders, so I arranged for an additional oil supply to the port faces by way of oil nipples and oil gun. These were used in the first year of operation but as the gun went astray I have not bothered to use them since. After eight years of running, with no special precautions taken at the end of the season, the cylinders are as tight today as they were when new. Last year I was so curious to how the bores and port faces were faring that I took the covers off one cylinder. Both were like black marble, beautiful and smooth with no signs of pitting at all. It was worth having to make new joints to find this out."
Wilf
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Post by Roger on Jul 7, 2022 15:43:23 GMT
I'm encouraged by your experience, as I have CI cylinders on Jessie and, if I ever get to finish it, is likely to have periods if inactivity. Ken Swan wrote this in 1971 about his experience with Bridget, I suppose a more heavily-used engine: "About this time there seemed to be a lot of discussion about rusting up and pitting of iron cylinders, so I arranged for an additional oil supply to the port faces by way of oil nipples and oil gun. These were used in the first year of operation but as the gun went astray I have not bothered to use them since. After eight years of running, with no special precautions taken at the end of the season, the cylinders are as tight today as they were when new. Last year I was so curious to how the bores and port faces were faring that I took the covers off one cylinder. Both were like black marble, beautiful and smooth with no signs of pitting at all. It was worth having to make new joints to find this out." Wilf I don't doubt his experience, but siezed pistons in cylinders definitely happens to some locomotives. Maybe this is due to how much Steam Oil the lubricator delivers, how cold the storage area is or other factors.
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Post by silverfox on Jul 7, 2022 20:06:36 GMT
Now as i write this i have no idea what i am talking about!!!, but am willing to put a bit more info into the memory banks for possible future use
On Michael Breeze B17 drawings he has either CI or GM blocks with CI/GM or PB valves running in CI liners
I hear a lot about expansion coefficient
Using the info for the B17 if i were starting from scratch ( i have gone the all CI route) would using the leaded bronze with CI pistons have any problems with the various expansion rates esp as there could be three different metals involved?
I am still looking at Bobs and thinking..shall i? but then it is only thinking..
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Post by Roger on Jul 7, 2022 21:19:34 GMT
Now as i write this i have no idea what i am talking about!!!, but am willing to put a bit more info into the memory banks for possible future use On Michael Breeze B17 drawings he has either CI or GM blocks with CI/GM or PB valves running in CI liners I hear a lot about expansion coefficient Using the info for the B17 if i were starting from scratch ( i have gone the all CI route) would using the leaded bronze with CI pistons have any problems with the various expansion rates esp as there could be three different metals involved? I am still looking at Bobs and thinking..shall i? but then it is only thinking.. There's no problem with any of the Copper Alloys and CI because the Coefficients of Expansion are similar. Here's a list of themYou can see that Bronzes are 18-19 while CI is 11.8 That means the CI piston expands slightly less than the Bronze cylinder block. The difference is say 7microns per metre per degree Celcius. So a 30mm bore will have around 30/1000x0.007x140=0.0294mm or just over a thou extra clearance if you raise the temperature from 20C room temperature to the temperature of Steam around 90PSI Personally I don't see the point in having CI pistons in a Bronze bore. Why not use Phosphor Bronze for the pistons, that's what I've done? Then the coefficients of expansion are almost identical. Hopefully that makes sense.
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Gary L
Elder Statesman
Posts: 1,208
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Post by Gary L on Jul 7, 2022 23:37:26 GMT
Now as i write this i have no idea what i am talking about!!!, but am willing to put a bit more info into the memory banks for possible future use On Michael Breeze B17 drawings he has either CI or GM blocks with CI/GM or PB valves running in CI liners I hear a lot about expansion coefficient Using the info for the B17 if i were starting from scratch ( i have gone the all CI route) would using the leaded bronze with CI pistons have any problems with the various expansion rates esp as there could be three different metals involved? I am still looking at Bobs and thinking..shall i? but then it is only thinking.. There's no problem with any of the Copper Alloys and CI because the Coefficients of Expansion are similar. Here's a list of themYou can see that Bronzes are 18-19 while CI is 11.8 That means the CI piston expands slightly less than the Bronze cylinder block. The difference is say 7microns per metre per degree Celcius. So a 30mm bore will have around 30/1000x0.007x140=0.0294mm or just over a thou extra clearance if you raise the temperature from 20C room temperature to the temperature of Steam around 90PSI Personally I don't see the point in having CI pistons in a Bronze bore. Why not use Phosphor Bronze for the pistons, that's what I've done? Then the coefficients of expansion are almost identical. Hopefully that makes sense. Makes perfect sense as always Roger. My concern (no, too strong a word) my interest would solely be on how to get a durable and effective seal without wearing away the relatively soft bronze. Certainly the tried and tested CI rings are unlikely to be suitable. O-rings of various sorts are the main contenders I guess, but I’d be amazed if they got anywhere close to the proven service life of CI. That won’t matter to many leisure users, but I still like to get the engineering as ’right’ (perhaps I mean ‘authentic’) as it can be. Gary
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Post by Roger on Jul 8, 2022 9:21:36 GMT
There's no problem with any of the Copper Alloys and CI because the Coefficients of Expansion are similar. Here's a list of themYou can see that Bronzes are 18-19 while CI is 11.8 That means the CI piston expands slightly less than the Bronze cylinder block. The difference is say 7microns per metre per degree Celcius. So a 30mm bore will have around 30/1000x0.007x140=0.0294mm or just over a thou extra clearance if you raise the temperature from 20C room temperature to the temperature of Steam around 90PSI Personally I don't see the point in having CI pistons in a Bronze bore. Why not use Phosphor Bronze for the pistons, that's what I've done? Then the coefficients of expansion are almost identical. Hopefully that makes sense. Makes perfect sense as always Roger. My concern (no, too strong a word) my interest would solely be on how to get a durable and effective seal without wearing away the relatively soft bronze. Certainly the tried and tested CI rings are unlikely to be suitable. O-rings of various sorts are the main contenders I guess, but I’d be amazed if they got anywhere close to the proven service life of CI. That won’t matter to many leisure users, but I still like to get the engineering as ’right’ (perhaps I mean ‘authentic’) as it can be. Gary I don't think CI is any harder than SAE660 Bronze. If you took a scriber to each, I don't think you'd find any difference. If anything, the Bronze could be harder. CI rings make little sense to me in Bronze cylinders or Phosphor Bronze pistons because of the corrosion issues alone. My choice is an experimental setup with four PTFE rings with two side by side and two under those. This allows for large expansion gaps which are covered by adjacent rings beside and under them. At the moment I haven't arranged for any pegs to guarantee they stay in the same orientation. My bet is they will stay where they're put, but I may be wrong. If they do move, I'll peg them with PTFE pegs. There are 'O' rings underneath to get them to stay out when there's no pressure, but those may be unnecessary too. I think this arrangement ought to have a very long life. We'll see. I agree that 'O' rings won't approach the service life of CI rings in a CI cylinder. PTFE ought to be a lot better.
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johnd
Part of the e-furniture
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Post by johnd on Jul 8, 2022 11:05:05 GMT
As a postscript to this thread I as previously stated have gone for the cast iron route, in the post £58 incl total.
It was interesting to talk to several metal suppliers over the last couple of days, all seemed genuinely concerned at the sudden sharp rise in prices. Direct quote from one supplier. “ Having obtained a quote earlier in the week to replace stock I haven't yet recovered from how much its going to cost so its on hold. “ Reading between the lines retail suppliers think that some of the incredible high price rises are totally unjustified. This supplier has now run out of SAE660 and LG2 over 3” and as stated is not restocking at the moment.
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Post by Roger on Jul 8, 2022 18:13:34 GMT
As a postscript to this thread I as previously stated have gone for the cast iron route, in the post £58 incl total. It was interesting to talk to several metal suppliers over the last couple of days, all seemed genuinely concerned at the sudden sharp rise in prices. Direct quote from one supplier. “ Having obtained a quote earlier in the week to replace stock I haven't yet recovered from how much its going to cost so its on hold. “ Reading between the lines retail suppliers think that some of the incredible high price rises are totally unjustified. This supplier has now run out of SAE660 and LG2 over 3” and as stated is not restocking at the moment. It's not unusual for non-ferrous metal prices to fluctuate wildly. I have a friend who's a scrap metal merchant, and he often sits on his pile of scrap until the price recovers from lows.
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stevep
Elder Statesman
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Post by stevep on Jul 9, 2022 8:54:27 GMT
Roger, we all need a friend in that business!
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Gary L
Elder Statesman
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Post by Gary L on Jul 9, 2022 9:45:04 GMT
As a postscript to this thread I as previously stated have gone for the cast iron route, in the post £58 incl total. It was interesting to talk to several metal suppliers over the last couple of days, all seemed genuinely concerned at the sudden sharp rise in prices. Direct quote from one supplier. “ Having obtained a quote earlier in the week to replace stock I haven't yet recovered from how much its going to cost so its on hold. “ Reading between the lines retail suppliers think that some of the incredible high price rises are totally unjustified. This supplier has now run out of SAE660 and LG2 over 3” and as stated is not restocking at the moment. It's not unusual for non-ferrous metal prices to fluctuate wildly. I have a friend who's a scrap metal merchant, and he often sits on his pile of scrap until the price recovers from lows. Metal prices, especially non-ferrous, always increase when there is a serious war on, and sterling has been sinking on the international exchanges for months, adding to import costs. Costs of production world-wide are going up, led by grain shortages and fuel issues due to the Ukraine war. Add all that to the UK having the lowest G20 economic growth forecast outside Russia, and the highest inflation, and you have a perfect storm. Don’t bank on an improvement anytime soon Gary EDIT And looking at it from the other end, the value (replacement cost) of all our locos and machinery should have shot through the roof too, and that isn’t going to change soon either. Might be a good time to check your insurance, and your security. - G
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