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Post by fentmar on Nov 26, 2007 13:26:22 GMT
Hello all 14xx builders- I am glad I found this website forum.
I have recently started building a 14xx having acquired the first 7 kits. I have put the cylinder and valve gear together- the valve chest rods seem to move freely but the cylinder's (with o rings on the piston heads) do not move without breaking my fingers.
Dean and Debbie have kindly offered to test the model on air at the factory once I have the motion together. I am going to take them up on this but don't hold out much hope that this will free things up.
I have tried different o rings and have polished the cylinder inside bores with emery paper and parrafin- this hasn't helped things much.
I fear I may have to seek alternaitives to o rings and maybe a new cylinder block.
From reading the blog a few may have had the same problem. Does anyone have a recommended way forward....
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Post by baggo on Nov 26, 2007 17:07:02 GMT
Hi Fentmar,
I'm not a 14XX builder but do use O rings for piston seals. Probably a daft question but do the pistons move freely without the rings fitted? If so then the O ring grooves in the pistons may not be deep enough and the rings are being compressed too much making them tight in the bore. The pistons with rings should be easy to push into the bore if the fit is right. If you have to force them in then they are definitely much too tight. I think I've read on other postings on the 14XX that the finish on some of the cylinder bores is very poor although I suspect this will just lead to very rapid wear of the O rings rather than making the pistons tight. Ideally the bores should be lapped or honed to a very fine finish if O rings are to be used and have a long life.
John
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mott
Hi-poster
Posts: 151
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Post by mott on Nov 26, 2007 22:27:03 GMT
Hello Fentmar,My 14XX runs well now and is a consistent performer, but, oh boy, its taken a while to get there. I now use clupet cast iron rings and am on my second set of cylinders. These were honed by the factory whilst I was there.The first set of cylinders became distorted by the drillings for the end plate screws which meant that rings stood no chance of sealing.You could feel the bulges with your finger when you ran it round the bore.If you cant get clupet rings I would go for graphite soft packing which if tightly made should be ok. O rings have a very short life if the loco is run every week but for only the occasional outing should last a year or so. You can turn the pistons off the rods and out the front and replace the 0 rings quite easily. Valve timing on these locos is a big issue but whilst lots of us have worried about the valve chest and whether the valves were sealing properly and timing is critical, my view is that inefficient cylinders is the most important issue. There are many other issues to get sorted to improve steaming, such as the correct positioning of the blast pipe. The regulator is also something to be viewed with suspicion, it can very easily stick and really needs to be very carefully assembled so it does not allow steam through when closed.My regulator has been in and out so often that I could no longer make the inner dome seal due to wear on the threads in the bush. I cant say I am the architect of all these improvements, I have just had loads of help from club members over the last couple of years who have re-engineered many aspects of the loco.Now she runs well but is tricky because it is very easy to cause the boiler to prime and cover you with cold water so you have to run the water level quite low in the glass but being for ever vigilant that the water does drop below the bottom nut. On an undulating track this can be quite a challenge. Debbie and Dean are very helpful and know how to get the loco running. Good luck. Mott
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Post by fentmar on Nov 27, 2007 11:12:45 GMT
Thank-you both- I think the way forward for me is to get Debbie to have a look at my motion assembly ( I will have kit 4 done by the end of the week) and have the loco tested on air. I can then suggest these options (and look at the grooves of the piston heads as the piston heads themselves do run freely).
It sounds like going for a longer term solution now will help get her running in the future.
thanks again
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Post by baggo on Nov 27, 2007 17:22:24 GMT
Hi Fentmar,
having just read the previous 14XX posts, I realise that the cylinders are cast iron. In this case, forget O rings and fit proper c.i. rings as Mott suggests. O rings won't last long at all in c.i. cylinders even if correctly fitted - it's very difficult, if not impossible, to get a good enough finish on c.i.
John
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Post by fentmar on Nov 29, 2007 11:07:03 GMT
Thanks very much,
Any idea where to start on getting someone to machine cast iron rings? and an idea of cost
thanks
Martin
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