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Post by runner42 on Sept 1, 2020 23:35:22 GMT
An easy solution is to fit a tickler device with one end close to the inlet ball and when operated lifts the ball off its seating, as shown in the photo. Brian P8252157 by Brian Leach, on Flickr
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Post by builder01 on Sept 1, 2020 23:54:53 GMT
Can I point you to my idea of simply modifying the inlet valves on hand and axle pumps so that a little piece of 'O' ring (or a very light spring) lifts the ball very slightly off the seat? That way, they can never get stuck! It's such a simple solution, I'm staggered that it wasn't thought of years ago and implemented universally since this is a recurrent theme. I wonder where the little piece of O ring will go when it breaks off after a few thousand cycles?
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Post by Roger on Sept 2, 2020 15:30:40 GMT
Can I point you to my idea of simply modifying the inlet valves on hand and axle pumps so that a little piece of 'O' ring (or a very light spring) lifts the ball very slightly off the seat? That way, they can never get stuck! It's such a simple solution, I'm staggered that it wasn't thought of years ago and implemented universally since this is a recurrent theme. I wonder where the little piece of O ring will go when it breaks off after a few thousand cycles? Why do you think it will break? The displacement is only about 0.2mm and Nitrile doesn't suffer from fatigue as far as I can tell, and is impervious to water. What's the failure mechanism you're worried about?
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Post by builder01 on Sept 2, 2020 22:31:44 GMT
I wonder where the little piece of O ring will go when it breaks off after a few thousand cycles? Why do you think it will break? The displacement is only about 0.2mm and Nitrile doesn't suffer from fatigue as far as I can tell, and is impervious to water. What's the failure mechanism you're worried about? I think it will break because of what it is made of. There must be a finite number of cycles that can happen before it breaks. Time will tell. Is there much track record of folks using a piece of an O ring for a spring? Does it simply last forever? I'm just thinking what will happen in the long run as I always consider a material like this as a consumable.
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kipford
Statesman
Building a Don Young 5" Gauge Aspinall Class 27
Posts: 566
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Post by kipford on Sept 3, 2020 7:36:57 GMT
I am with Roger. I worked all my life in Aerospace and we used rubber in dynamic compression situations in hydraulic circuits where failure rates had to be less than 10 million cycles. Dave
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Post by Roger on Sept 3, 2020 8:27:16 GMT
Why do you think it will break? The displacement is only about 0.2mm and Nitrile doesn't suffer from fatigue as far as I can tell, and is impervious to water. What's the failure mechanism you're worried about? I think it will break because of what it is made of. There must be a finite number of cycles that can happen before it breaks. Time will tell. Is there much track record of folks using a piece of an O ring for a spring? Does it simply last forever? I'm just thinking what will happen in the long run as I always consider a material like this as a consumable. What evidence do you have that it will break though? I disagree that there has to be a finite number of cycles before failure. Even Steel springs have a thing called the 'endurance limit'. There are research articles such as this online if you want to delve deeper, but note that this paper is concerned with high strain conditions. The implication seems to be that there isn't a fatigue issue at low strain. So, for all practical purposes, nitrile does last forever. I've got 'O' rings that are decades old in my stock, and they're just the same as they were when they were made as far as I can tell.
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Tony K
Elder Statesman
Posts: 1,573
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Post by Tony K on Sept 3, 2020 8:31:50 GMT
Nobby, I think the injectors you have chosen are very good and the best I have found available commercially.
If you are wondering where to put the axle pump - I think the best place is in the bin, where I think all the others should be.
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Post by Roger on Sept 3, 2020 10:13:32 GMT
Nobby, I think the injectors you have chosen are very good and the best I have found available commercially. If you are wondering where to put the axle pump - I think the best place is in the bin, where I think all the others should be. Hmmm that old chestnut again. I strongly disagree. Axle pumps are useful in many scenrios, such as novice training, reducing the workload and saving a running session or a steam test when injectors won't pick up. Anyone claiming that injectors always work isn't being completely honest. You don't have to used them all of the time, but I don't see the argument against having a backup unless you're being a purist. It does seem to be an elitist club of the smug who would never fit them. I take a more pragmatic view. It's no different to having safety chains or fusible plugs that don't exist in full size. Some things are just useful, whether they're prototypical or not.
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Post by builder01 on Sept 3, 2020 12:27:24 GMT
So, for all practical purposes, nitrile does last forever. I've got 'O' rings that are decades old in my stock, and they're just the same as they were when they were made as far as I can tell. Actually, nitrile O rings have a shelf life of 15 years, they do not last forever. Like any natural product, they will degrade. Shelf life of Viton and FLAS is infinite. So, if you have decades old nitrile O rings, you may want to toss them. This is from www.oringsusa.com/html/shelf_life.html
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Post by Roger on Sept 3, 2020 12:44:28 GMT
So, for all practical purposes, nitrile does last forever. I've got 'O' rings that are decades old in my stock, and they're just the same as they were when they were made as far as I can tell. Actually, nitrile O rings have a shelf life of 15 years, they do not last forever. Like any natural product, they will degrade. Shelf life of Viton and FLAS is infinite. So, if you have decades old nitrile O rings, you may want to toss them. This is from www.oringsusa.com/html/shelf_life.htmlI think you're massively overstating the risk of this ever being an issue. It's a bit like shelf life you see on some products. Yes, to be 100% as good as when packaged, you adhere to the dates. However, practical experience tells you that things last much longer without the slightest hint of them degrading. I'm really not going to worry about it, I'll be dead and buried before it's ever an issue.
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Post by andyhigham on Sept 3, 2020 16:30:13 GMT
A single axle pump is a horrible device. Two axle pumps phased 180deg apart would put less loading on the mechanism and a more even load 3 or 4 pumps would be nice and smooth, near constant load with no jarring
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Post by Deleted on Sept 4, 2020 11:09:43 GMT
I'm with Tony unless prototypical....
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stevep
Elder Statesman
Posts: 1,070
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Post by stevep on Sept 4, 2020 16:32:17 GMT
I can't understand this aversion to axle pumps (or in the case of my Rob Roy, a crosshead pump).
I hardly notice it, and the only reason for opening the bypass fully is when going up the banks on our track (which are supposed to be 1:100, but to due ground settlement, are now far steeper) to ensure that I don't put too much water into the boiler at a time when I need all the steam I can get.
At the old Andover track, which was a lot flatter, I could go lap after lap, with the pump just putting enough into the boiler to keep the water level up.
In my opinion, if you can feel the resistance of your axle pump, it is probably too big. It only needs to deliver a little more water than you are using, and the bypass should only need to be be 'cracked' a little.
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mbrown
Elder Statesman
Posts: 1,724
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Post by mbrown on Sept 4, 2020 17:58:01 GMT
My LYN relies solely on two injectors and everything was fine for ages - until one day on the Cheltenham track she must have taken on something with the water and primed massively....water gushing out of the safety valves, chimney, the lot.
After that, neither injector was totally reliable, both needing a lot more fiddling with to get them to pick up dry and sometimes feeding very poorly. Cleaning them helped but the old performance was never recovered.
So the Burma Mines loco has a small axlepump - and 99 3462 will as well, although I am not yet quite sure where I am going to put it.
I have also had injector trouble on the Talyllyn where the boiler treatment sometimes builds up a deposit on the cones and performance falls off rapidly. Frankly, the anxiety is something I can do without in any scale and I see an axle pump as an insurance policy for peace of mind. That's despite a deep desire to build to scale where I can. If I could put the original axle pump back on ex-Corris No.4 I would be tempted...
Each to their own, of course, but I prefer the minor compromise to "injector angst"!
Malcolm
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Post by springcrocus on Sept 4, 2020 21:40:44 GMT
I have an axle pump and a hand pump as well as an injector (well, I will have) and, quite frankly, I couldn't give a damn for the purists. I am far more interested in protecting my investment. Five grands' worth of boiler at risk just to say," well, it's not on the prototype"?
Sorry, practicality over vanity every time. Regards, Steve
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Tony K
Elder Statesman
Posts: 1,573
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Post by Tony K on Sept 6, 2020 7:44:43 GMT
.... It does seem to be an elitist club of the smug who would never fit them." "Anyone claiming that injectors always work isn't being completely honest." Roger, thank you for your bigoted comments. I did say it was what I thought and, indeed, said "I think" twice in the post. I would like to apologise for a misunderstanding - I was under the impression I could think what I liked, without insults from you.
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Post by Roger on Sept 6, 2020 8:16:09 GMT
.... It does seem to be an elitist club of the smug who would never fit them." "Anyone claiming that injectors always work isn't being completely honest." Roger, thank you for your bigoted comments. I did say it was what I thought and, indeed, said "I think" twice in the post. I would like to apologise for a misunderstanding - I was under the impression I could think what I liked, without insults from you. Indeed you can Tony, but maybe you too should think twice before saying something that you know is inflamatory. I never intentionally insult or upset anyone.
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Post by 92220 on Sept 6, 2020 8:25:23 GMT
If someone doesn't want to fit an axle pump to their loco, why can't it be fitted to the driving truck, with a water tank under the seat, and connected to the loco via a flexible pipe? I'm sure, with a driver sitting on the truck (which there would have to be anyway!) there would be plenty enough traction to drive the pump.
Bob. Edit: If someone insists on being prototypical and not fit an axle pump, why fit a tender pump? That is not prototypical either. There are pros and cons for both approaches. I'm not fitting an axle pump because I am building a faithfully detailed copy of the loco, as near as the confines of scale allow. As Roger says, injectors are not infallible. They do fail. The axle pump on the drive truck, would provide a guaranteed water supply, and keep the loco prototypical. The handpump that normally goes in the tender, could also be fitted to the driving truck.
Bob.
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JonL
Elder Statesman
WWSME (Wiltshire)
Posts: 2,912
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Post by JonL on Sept 6, 2020 8:38:12 GMT
One of the biggest strengths of a forum like this is its huge cross section of experience and opinions, I don't imagine anyone was going out of their way to genuinely inflame people. The community currently has a fantastic mix of engineers carrying out engineering by tried and tested principles, and those who are pushing the envelope and asking "but why has it been done this way?". Sometimes they find out why, and sometimes they find out people have just been reluctant to change something that worked but has now got better techniques or materials available. And then there is me, wide eyed novice trying to pick the wheat from the chaff from both camps!
What I'm badly trying to say is, we are all here for the same reasons, with the pleasure of the hobby at the core. Let's not get too bent out if shape about things said on a faceless forum where nuances of expression are lost, things can be interpreted many ways in just pure text where if they were said over a pub table we would be far more easily able to understand what is intended, for better or worse.
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Post by Deleted on Sept 6, 2020 10:24:28 GMT
Oh dear, a hornet's nest seems to have been disturbed...lol I have no issue with anyone fitting whatever they want to their loco, after all, it's theirs to do with as they please, indeed, my smaller pacific 4470 has an axle pump fitted so I swing both ways. Some of the comments made in this thread I personally find insulting to those who strive for perfection, trying to achieve a good looking accurate to the prototype model does not mean you fit into the description entailed by such words as 'purist, smug or elitist'. I do take exception though to those who attack others for wanting to faithfully follow the prototype, who are they to question what I or anyone else does. If that makes me a purist or rivet counter then good, I'll proudly wear that badge as there is nothing wrong with striving to accurately follow the prototype that they are building in miniature, it's only an issue if said purist looks down on others who don't follow their principle, that I would never do.
4472 is being built as a faithful miniature of its big sister, that means no axle pump or tender handpump, in fact, Don makes it very clear in his words where he sits on this subject, to quote, 'it would be undignified to fit this on such a model', I agree with him fully but also accept that it's the norm for one to be fitted and I have no problem with that, I do not look down on a model if it has one fitted. I also give consideration to the 'what if' scenario's which can and will occur when steaming a locomotive. I accept that it is possible for both injectors to fail, it has happened on full size and so can also happen on a model, I have briefly covered how I intend to deal with this in my build notes, I'll cover it in full detail when I get to this stage. I recall someone mentioning fuse plugs? Paul informed me when I questioned him fitting one to my boiler that this is now required for a CE stamp, no plug and the CE stamp is invalid, IIRC this is a recently new legislation. I also understand that as of yet this is not a 'code' issue as Paul said I can just blank the bush off with a plug if I don't want a fuse plug fitted, but the bush for it must be there for the CE stamp. Who's to know if one day this becomes part of the boiler code or not, if it does new commercial boilers within the last year or so should be covered.
regards
Pete
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