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Post by wdiannes on May 18, 2014 10:01:42 GMT
Congratulations on your success Peter!
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Post by Deleted on May 18, 2014 10:21:31 GMT
Hang-on PETER, try not to overdo it..You don't want the familiar "Dalmatian Driver" syndrome appearing !!....The Chimney top should be grey with a hint of oily-dampness..any more than this and you are OVER-oiling......Try to visualise the oil actually "at work" in the cyls. etc......It's should be a very fine mist ( NOT LIQUID as per your car engine..).............. Have a look at how a basic 2-stroke engine is lubricated using a self-mixing oil in with the petrol...Our steam locos have almost the same idea ie}--- the oil is atomised and mixed in with the operating medium = main steam......Please DON'T change your current oil ( you'll need to purge all the old stuff out anyway before filling with new ) but actually REDUCE the pumps' output by one hole on the drive arm....
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nonort
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Post by nonort on May 18, 2014 10:49:06 GMT
Great news on the lubricator front. Its easier to clean the oil off the shirt and face than remake all the slide valves and cylinders. But in all seriousness I have long since given up on the Mamod swinging cylinder style of pump much loved and successfully used by LBSC. They are not self priming as you have discovered and unless driven from a constant motion will either over lubricate at full gear and deliver none at short cut off. Rarly have I come across one that works for all conditions. Full size practice the lubricators are driven from a constant motion point and the deliver is adjustable depending on what is being lubricated. The Les Warnett plunger type of pump is self priming and the delivery can be easily set by the separation of the O ring seals. what drives the pump ratchet roller clutches or gears is immaterial the drive needs to be constant. As an aside I know of a steam boat engine that has cast iron cylinders with bronze slide valves and bronze pistons that since its building many years ago has never had cylinder lubrication. The recovery of the oil was to much trouble. The cylinders have small tallow cups that are used at the end of each steaming with proper tallow which is bio degradable so does not pollute the water source.
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uuu
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your message here...
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Post by uuu on May 18, 2014 11:23:30 GMT
I'll second Hagley's thoughts. If your steam is not hot enough it just won't get the treacle properly working, so you're better to stick to the thinner stuff. If you run at 250 psi and high superheat then by all means go for the thick gloop. It's not "better" it's different.
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Post by iompeveril on Jun 1, 2014 14:31:44 GMT
I took the opportunity of this dry weekend to have another steam-up of ‘Peveril.’ She behaved impeccably, with no water, fire or lubrication issues.
However, there is one little ‘niggle’ which I know is not unique to my model, and that is when she blows off the safety valve does not re-seat even when the pressure has dropped quite a bit. The only way to get it to close is by giving the protruding spigot a tap with the firing shovel.
I haven’t had the valves apart, but I presume they are the usual spring-loaded ball type. So what is the usual cause of this problem and how is it remedied?
Peter Jordan
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jma1009
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Post by jma1009 on Jun 2, 2014 8:48:17 GMT
hi peter, if you safety valves are of the 'pop' type (which i assume they are) there will be a small circular rebate on the valve seat (not easy to see if you dont know what to look for). the problem you describe is caused by this rebate being too deep. a 'whisker' of about 10 thou needs taking off the area around this rebate to reduce it's effective depth. a pin drill of the correct size and 'hand lathe' will do the job in a matter of seconds with the safety valves dismantled. setting the safety valve bodies up in the lathe to take 10 thou off with a pin drill, endmill, slot drill, or small boring tool will take much longer of course and require an adapter to hold the safety valve body. cheers, julian
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Post by marshall5 on Jun 2, 2014 8:59:51 GMT
Peter, they often do this to some extent and the odd tap will do no harm. How much is the pressure dropping before the valves re-seat? If it's only 5 lbs or so I wouldn't bother. If it is more than, say, 10 lbs it'll need attention. If so strip the valves down and inspect the ball/ball seat - if there is a build up of limescale etc, a soaking in citric acid will remove it. It could be that the springs are getting 'tired' or even rusty if they're poor quality stainless - in which case they need replacing. Is the valve stem scored and jamming in the guide/adjusting nut? I've seen people using a pair of pliers to lift the stem "to check the safety valves are working" leaving scores on the stem. If this is the case you need to clean up the stem with fine emery until it slides freely - a drop of oil will help. Remember that once you've re-assembled them the safety valves will need to be re-set to the correct operating pressure. Cheers, Ray.
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nonort
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Post by nonort on Jun 2, 2014 16:10:21 GMT
Hi ninety nine percent of safety valve problems are caused by using rubbish springs. I would almost take bets to say that the spring in the offending valve has been cut from a length of spring stock. I turn your attention to the Gordon Smith articles on safety valves where the spring is properly mounted so as to not interfere with the spindle,for the spring to work efficiently has to have properly squared off ends and be of the correct spring rate. If one of the safety valves works OK then the problem is even more likely to be the spring. I believe that Polly models sell the Gordon Smith springs. They will need to know the working pressure and the diameter of the valve seat to select the correct spring. If perchance the valve is of the Slater type then the width of the seat on the valve its self needs to be no more than twenty thou wide any wider and the hysteresis of the valve will be huge and sizzle away for ever as the steam escaping forms a cushion a bit like a hovercraft skirt.
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Post by iompeveril on Jun 3, 2014 13:37:26 GMT
Thanks for the replies so far received on the safety valve issue. When the valve stays open it drops the pressure by about 20 pounds, so it really is a pain, and obviously wastes water. However, as I expect to be moving house shortly, and I want to keep the engine serviceable for the foreseeable future, any remedial works might have to wait until the winter 'lay up.'
Peter Jordan
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jma1009
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Post by jma1009 on Jun 3, 2014 22:05:27 GMT
i agree with nonort entirely re the superiority of the gordon smith design. however there is nothing to prevent the use of a traditional pop valve design as opposed to gordon's 'mild' pop action design. the traditional design in miniature will cope with the accumulation test quite ok.
pete, whoever made your safety valves made the rebate for the pop action too deep. this has nothing to do with strength or quality of the springs. if a spring opens at a certain pressure it will close at same unless the valve/safety valve ball is exposed to a greater area when slightly open.
cheers, julian
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Post by iompeveril on Jun 8, 2014 17:32:01 GMT
I've decided that another little improvement I can make to my model is to fit a new gauge glass. At present it is fitted with a glass which has a broad red line up it, with little or no contrasting white background, and it is difficult to see the water level unless you peer closely at the gauge. I'd like to change it to the kind which has a broad white background with a thin blue line up it. I have several lengths of this that I've had for some years, but none are the right size for the gauge on 'Peveril.' I've looked at various suppliers websites but can't seem to find any glass with the white background/blue line. Can anyone tell me where I can get some, please? I need 5mm outside diameter.
Peter Jordan
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smallbrother
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Post by smallbrother on Jun 8, 2014 18:27:30 GMT
Live Steam Models in Derby do a 4.5mm and 5.5mm blue line.
Pete.
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jma1009
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Post by jma1009 on Jun 8, 2014 22:42:58 GMT
hi peter. it is easier to make a card (white) insert behind the glass with biro lines added at 45 degrees. although i have quite a quantity of the schnellbach glass you refer to it is much more brittle than ordinary gauge glass. however if you let me know what size you need i'll check my stock to see if i have any of the right size. cheers, julian
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nonort
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Post by nonort on Jun 9, 2014 8:47:00 GMT
May seem a little obvious but I've been using sections of bar codes from beer cans for along time now. Schnellbach glass is a soda glass and is very brittle and has to be thicker walled to withstand the working pressure. Pyrex glass will be much thinner and give more accurate reading by the reduction of the meniscus effect. Pyrex glass is much more accurately produced soda glass i believe is almost hand made like a stick of rock.
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