Midland
Elder Statesman
Posts: 1,870
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Post by Midland on Jul 11, 2017 15:16:34 GMT
Hi All I think it is time to come clean and admit that I am displacing the Compound with a very pretty 990 Class with the same number as the class leader. Quite a rare loco in model form but a very interesting one and just very Deeley! A bit of a challenge to get it going. First, she was not put to bed very well and the cylinders were locked up but some gentle prising had loosened the corrosion and lots of oil had loosed things up. The brake valve fell apart on first turning it but that is now back to normal. When I ran her the noise from the chimney told me I was slipping badly but then I wasn't when you looked at the wheels. So at the end of the day I put her in mid gear, opened the regulator and the blow by was defeaning. It appeared the piston rings were not holding very much steam back. The gathered experts told me all about new piston rings. This is new territory for me as I have been in a Stephenson's slide valve world. This is Walschaerts and piston valves with no eccentric as it has Deeley's gear. So now to some pictures. Cylinder Block 1 by David Goyder, on Flickr Don't like the corrosion? in the LH valve. Valve spindle 1 by David Goyder, on Flickr At each end, there are two slit rings and one solid. Not quite sure why it is that way but no doubt the experts will lead me to the answer. RH Valve bore 1 by David Goyder, on Flickr RH Valve spindle 1 by David Goyder, on Flickr This last one is important to me as it show how many threads should show when I put it back with new rings. So an I correct in assuming that the clyinder block is gunmetal and should I use cast iron rings and how the hell does one do that? As I said these are uncharted waters for me so any tips or direction will be most welcome. Meanwhile I will read what I can find. Cheers David
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Midland
Elder Statesman
Posts: 1,870
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Post by Midland on Jul 11, 2017 15:37:56 GMT
. . . and I have just discovered that the middle of my 'three rings' is in fact part of the spindle which means has two rings, told you I am learning!!! D
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don9f
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Les Warnett 9F, Martin Evans “Jinty”, a part built “Austin 7” and now a part built Springbok B1.
Posts: 960
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Post by don9f on Jul 11, 2017 16:33:13 GMT
. . . and I have just discovered that the middle of my 'three rings' is in fact part of the spindle which means has two rings, told you I am learning!!! D Hi, I wasn't sure if that was what you meant when you mentioned the "solid" ring, so yes it's just got two normal piston rings per valve head. It wouldn't be normal to use piston rings in gunmetal bores and it's not obvious from the photos what the cylinder block is made from....could they be gunmetal but lined with cast iron or steel perhaps? Cheers Don
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Midland
Elder Statesman
Posts: 1,870
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Post by Midland on Jul 11, 2017 17:29:46 GMT
Hi Don The one piece cylinder block is a smooth yellowy metal but I do not know my metals that well so I would guess bronze maybe but the piston valves have steel liners. There is a hint of rust just inside the left one. This just goes to show that you cannot just 'park' a loco, it has to be cared for. So now to lern how to make new rings and how much bigger than the bore!!! Cheers David
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Midland
Elder Statesman
Posts: 1,870
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Post by Midland on Jul 11, 2017 18:36:47 GMT
Hi Don The one piece cylinder block is a smooth yellowy metal but I do not know my metals that well so I would guess bronze maybe but the piston valves have steel liners. There is a hint of rust just inside the left one. This just goes to show that you cannot just 'park' a loco, it has to be cared for. So now to lern how to make new rings and how much bigger than the bore!!! Cheers David Still learning. The cylinder block is magnetic as is the valve area so that suggests cast iron. Bobbbin is cast iron as well??. This loco was built by a Tony Meeks from Peterborough. He seems to have built some five prize winners and he was considered very good so I am assuming (perhaps dangerously) that he did things pretty well. Anyway reading through a post from 2014, modeleng.proboards.com/thread/8962/piston-valve-liner-clearance All very informative. A question that bothers me is just how springy should these rings be. Just tried my RH bobbin back in the bore and it just popped in. Do rings just get weak? Anyway PTFE with graphite seems to be a solution. Cheers David
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Post by chris vine on Jul 11, 2017 19:52:43 GMT
For steam engines, the rings don't have a very large wall pressure, so they should slide quite easily.
Are you sure the rings are worn? If you put a ring in the bore, without the valve or piston, you can judge it much better as you can see the gap etc.
I may be that the problem was just that the rings were seized in their grooves and so were not touching the cylinder walls.
If the engine used to run well (and the bores have not been badly damaged by the iron rings, then you wonder if it is worth using different materials??..
Chris.
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Midland
Elder Statesman
Posts: 1,870
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Post by Midland on Jul 12, 2017 13:26:33 GMT
Thanks Chris All the various comments are coming together and this thread is becoming a sort of diary to disciplibe one's thoughts (and learning). Have measured the bore as accurately as I can and the front middle and back readings are within .001". Actually .751/ .752/ .751. Have taken a ring off the bobbin and put it in the bore and the gap is about 19 thous. Feeler gauges at 18 thou go in the gap and 20 does not. I am told the gap should be about one thou. So I am coming to the conclusion that the 'blow by' might be that the rings are gapped too far. So it is not a huge job to get new rings and put the thing back together and see what happens. At least I do not have to start altering the bobbins and taking other drastic measures. New rings seems a simple (if expensive) experiment. More news in due course. Piston valve ring gap by David Goyder, on Flickr Is this gap big enough to create the problem? Cheers David PS Know why I love slide valves!!!
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Midland
Elder Statesman
Posts: 1,870
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Post by Midland on Nov 25, 2017 18:41:29 GMT
This is loco has a combined steam brake and vacuum release valve. The only problem is that the front control disc leaks as does a sinking ship. I have tried lapping the two mating surfaces with brasso and while there is evidence of progress I wondered if anyone has a better solution. The brakes work btw as does the steam sanding so I am a bit chuffed with this little gem!!!
Talking of steam sanding, it took a while to get rid of real sand from the beach as it had gone hard in the sand hoppers. Sand and oily locos are strange bedfellows, sand is not my favourite lubricant. Have thought of trying aquarium gravel but surely there must be something better if you really want to use it. Any thoughts other than don't!!!!!
And now that the movie is released I can mention that it is in Paddington 2 judging by the days we spent at the studios where the film was shot. Was sworn to secrecy! Have not seen the film yet so it may have been cut! We will see.
Cheers David
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Post by Roger on Nov 25, 2017 23:22:24 GMT
Hi David, Perhaps something a little more aggressive for the lapping is in order, Brasso is very fine. Grinding paste for car valves is too coarse in my opinion, but you can get any grade you like on eBay.
If you type in "grinding paste grit" as the search term it will show you all the entries that mention the grit which is the same as that used on Wet & Dry.
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kipford
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Building a Don Young 5" Gauge Aspinall Class 27
Posts: 566
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Post by kipford on Nov 26, 2017 8:57:25 GMT
In our 4mm scale world we often 'ease' tight spots on gear boxes using tooth paste which is a mild abraisive. May be worth a try.
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Post by fostergp6nhp on Nov 26, 2017 11:26:02 GMT
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mbrown
Elder Statesman
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Post by mbrown on Nov 26, 2017 14:57:00 GMT
Just a thought - but I have sometimes worked away at lapping surfaces together without success, only to find, after hours of puzzling, that when the component is reassembled, some glitch in the way it is constructed is tipping the mating faces slightly and preventing a seal. No idea if that is the case with your valve, not having seen it, but perhaps worth a little investigation?
Good luck.
Malcolm
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Midland
Elder Statesman
Posts: 1,870
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Post by Midland on Nov 26, 2017 18:48:48 GMT
Thanks to all who advised. Guess what is on my chaotic shelf, yellow grinding paste. That did most of the work. Then I tried toothpaste and that shined it up a bit, then back to brasso to get a nice smooth surface. Tried it, almost there just need a little more patience! But the truth is the forum does work!!! Thanks D
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Midland
Elder Statesman
Posts: 1,870
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Post by Midland on Nov 27, 2017 21:21:07 GMT
Just a thought - but I have sometimes worked away at lapping surfaces together without success, only to find, after hours of puzzling, that when the component is reassembled, some glitch in the way it is constructed is tipping the mating faces slightly and preventing a seal. No idea if that is the case with your valve, not having seen it, but perhaps worth a little investigation? Good luck. Malcolm Malcolm Very astute comment. Yes the two faces are as smooth as a babby's bottom, as I remember them about 45 years ago! But the shaft rocks in the hole. The shaft is .154/5 along its length but the hole into which it goes is about .164, somewhere between a no 20 and 19 drill so that is the new issue. I am inclined to ream the hole in the body out to 11/64s or perhaps 3/16s and turn up a sleeve so the shaft is held firmly. The shaft is bronze so I will have to use a bit of the same and see of I can turn it that accurately. Never really used bronze before so yet another learning curve. There are so many it is a little bit like the seven hills of Rome! How thin can a sleeve be I wonder?? Cheers David
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Midland
Elder Statesman
Posts: 1,870
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Post by Midland on Aug 23, 2018 20:30:27 GMT
Ran the 990 a couple of weeks ago and she has a definite limp with lots of steam pouring out of one of the valves so a major investigation was called for. Since most if not all of the valve gear is very hard to access, it appeared a boiler off project was in order so in Tuesday the task began and it took two days to unravel. My friend Mike can get his boiler of in an hour or so as he says but then it is off every week to sort his bits and pieces. Anyway, thought you might like to see some of the good bits and a few not so good. So here are some pictures showing the dismantling. I should comment that this is a self-inflicted wound as I had blow by in the piston valves and had to renew the rings. Outside admission and all that, apparently a Midland obsession until they smartened up. I think I destroyed the packings when putting them back so here we are. And it was ‘Simplyloco’ who showed me how to make new rings out of cast iron a year or so ago so it is useful to have an engineer around the corner, I am not one just love trains, he hates them but is an engineer! Useful combination and we both love our dogs! So let's start at the smoke box, quite simple undo some bolts, IMG_0705 by David Goyder, on Flickr Only problem was that five came of fine, nunber six sheered off. Does one drill into a boiler band, yes successfully. Reach rod was delight, little pin held in with a cover plate, IMG_0706 by David Goyder, on Flickr IMG_0707 by David Goyder, on Flickr Still more to undo. The steam sanding lever had always leaked and I had no idea how to fix it. I should explain that the cab top comes off seperately, very ingenious but even so one could not have access to a number of joints. These ones in particular. IMG_0728 by David Goyder, on Flickr All was revealed later. After more undoing the whole cab side came off, IMG_0733 by David Goyder, on Flickr But having denuded this poor loco the boiler would not shift. In fact it was still solid to the frames, major frustration. Then I questioned why would someone do it this way? IMG_0738 by David Goyder, on Flickr There was the clue. Undid the cladding and I found the culprit. Do not ask about the screws but the boiler will rest on its mountings for ever! IMG_0742 by David Goyder, on Flickr IMG_0743 by David Goyder, on Flickr There was more that I will not bore you with. Someone said that the best way to learn about a loco is to take it apart. Anyway, latest report is under fresh air the piston valves packing gush fresh air. Whats new??? I once took apart an old remington manual typewriter. My dear old dad told me that one day I would learn how to put it together again. I hope his support will help with this old girl!!! Cheers Guys D
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Post by Roger on Aug 24, 2018 13:50:17 GMT
Hi David, Am I right in thinking that this is a Mild Steel angle bracket that's being held onto a Mild Steel Frame? If that's the case, you could take the bracket off and case harden it so that you could spot the centre of the broken screw without it wandering. As it's currently soft, I think it's asking from trouble to expect it not to wear away the bracket as the drill tries to find the centre.
Whatever happens, you would only spot the middle because that's the clearance and not the tapping size.
I'd still be wary of drilling the tapping size, I'd definitely go 0.1mm under that and I'd still want to make a drill guide at that size because given half a chance, it will still wander.
If you've got a small piece of gauge plate, you could spot through two holes from that bracket using the inside of the angle to get the holes the same distance from the edge. One right through and one 0.1mm under the tapping size so as to make a drill jig. Once you're happy it's right, just heat it to red and quench it. You can bolt that to the frame with the remaining bolt, making sure it's level with the top of the frame.
I'd make a collar to fit over any drill to make sure you can't go too deep and damage the boiler if you're leaving it in place while you do this.
Once drilled out under the tapping size, you will probably be able to tease out the thread with a scalpel enough to get a tap to start and take out the rest of it.
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Midland
Elder Statesman
Posts: 1,870
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Post by Midland on Aug 24, 2018 22:00:15 GMT
Roger I think you are correct. I will dispense with the angle piece as the boiler weighs a ton and gravity will do a better job. Have you ever lifted a loco by its boiler? I think not. The plot thickens and at a pace. I am aiming at one little gland-ish bit to put some packing into to stop the steam leaking out. But to get to the gland you have to get rid of the boiler and the remove the valve spindles and that is virtually dismantling the whole bloody thing. And I now have discovered how this man put it together. Very crafty and ingenious, well worthy of your genius. Will show some pics tomorrow. Anyway "Simplyloco" came over to assist, a mixed blessing!!!! He showed me that my cast iron piston valve rings that he taught me how to make were now worn away by some 6 thou on the diameter, that is why I had blow by. Wrong kind of cast iron apparently. A bit like wrong type of leaves. Told me I was not lubricated enough so opened a bottle of the best red. Then we decided to check the diameters of the bores. Did it with the vernier and got a good result. Then (he) decided to check it with one of those little springy things with two bits spring out. I will let him tell you about that. Had a discussion about inside vs outside admission piston valves and we parted with my saying I had learn a lot about precision engineering and he saying he had learn a bit about steam engines. Not a bad trade really. Never did find out what it was like to renew a spindle on a tank in darkest Germany under gunfire but that will emerge one day. Anyway lots of jars with nuts and things and lots to put back together and still have some nice graphite yarn to put in but that can only happen when the valve spindle is in enough to hold it, then the support plate is put in and the spindle is moved up for setting and then we set the valves in the right place and the covers on the other end and so and so. I know why I liked clockwork toy trains!!!! Pics tomorrow. D Bloody Exhausted, stupid steam locos, still looking at stamp collecting!!!!!
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Midland
Elder Statesman
Posts: 1,870
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Post by Midland on Aug 24, 2018 22:01:47 GMT
And as a postscript, one of the cover bolts came off so a careful drilling and tapping up next. please recommend an easier hobby!!! D
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Post by simplyloco on Aug 25, 2018 7:20:49 GMT
Forgive me Father, but I have sinned.Whilst measuring the bore with the spring bore gauge- much more accurate than a vernier and I wanted a mid cylinder measurement - it sprung out into the (very) large exhaust port and proved impossible to remove without taking off the end flange. I exited, stage left, in a hurry! John
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Post by Roger on Aug 25, 2018 7:51:42 GMT
And as a postscript, one of the cover bolts came off so a careful drilling and tapping up next. please recommend an easier hobby!!! D Where else can you get this much intellectual and sometimes physical stimulation though? Solving these little puzzles is great fun! If it was all easy, it would be very boring. To misquote a great man... "We do this, and the other things, not because they are easy, but because they are hard"
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