mbrown
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Post by mbrown on Dec 1, 2019 22:38:56 GMT
David's last comment on remembering what changes you have made so that you can undo them if necessary is very helpful. Sometimes, trying to get better valve events ends up making matters worse and it helps to have a starting point you can find your way back to before trying other adjustments.
In the past I have got into almighty knots - especially with Stephenson gear - by forgetting this. Hackworth at least has fewer variables and you should be able to return to a starting position easily enough.
Julian mentions the return crank position. With Modified Hackworth, as on Romulus, Sweet Pea and Edward Thomas, the return crank pin must always be exactly 180 degrees opposite the crank pin.
Good luck!
Malcolm
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jma1009
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Post by jma1009 on Dec 1, 2019 23:30:59 GMT
I found watching the crosshead worked well enough. I'm pretty happy with how it runs on air having used that system. Given how difficult it is to see exactly when the valve opens the port and exactly how even the openings are per side I'm guessing finding the exact front and back dead center isn't critical either. If you're willing to put in the work though, I guess you'll know it's as good as can be. Both of my locos have the valves between the frames with outside cylinders which might explain why I find it difficult to see what the valve is doing as well as I'd like. I don't think I'd be up for piston valves! I did adjust one of my valves by half a turn of the spindle in the nut which seemed to smooth it out slightly. I was careful to remember which way I turned it so I could undo it again and compare. Hi David, You can't guess when the piston/crosshead ends it's stroke. The piston/crosshead is moving very slowly, and you could easily be 2 - 5 degrees out depending on a bit of 'slack'/lost motion, or simply not being very very careful even if everything has no 'slack'/lost motion. However, at this time, the valve, being 90 degrees or so out of phase, is moving very quickly at FDC and BDC, and therefore absolute accuracy in establishing FDC and BDC is required; not just guessing when the crosshead is at the end of it's stroke. Malcolm has advocated the Don Ashton method, which is what I have always used, and I see no reason why anyone should wish to depart from this superior method of establishing FDC and BDC. Pete ought to do the same, of course, rather than just guessing, and with so many variables, and so many other factors to be considered and established accurately, as Malcolm has pointed out. (I use a fine marker pen on the driving wheel rather than Malcolm's centre pops). The fundamental problem with Pete's approach is that if the return crank is 'out' he will not find this out by his approach. Neither can Pete check lead openings at FDC and BDC or 'cut offs', if Pete has not established accurate positions for FDC and BDC. It seems to me, as implied by Malcolm, that a very careful check of die block positions either side is required that would cause one valve to open more than another - indeed you also need to check a lot more that may cause all of this, but this is basic stuff rather than getting into the involved procedure of setting the valves themselves once you are certain the weighshaft arms and links etc are the same on each side and the slide shafts set accurately and the same each side, and the axle box heights. Just looking at how far the valves open is pretty useless, and does nothing to check other errors, or is even a start as to how the valves should be set properly at accurate positions for FDC and BDC using Don Ashton's superior method. Cheers, Julian
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Post by David on Dec 2, 2019 4:54:34 GMT
Thanks Julian. I know my method is rough and ready but it's going to have to do because I've just cleaned the frames and cylinders in readiness for painting and there's no way I'm taking it apart again. It's ticking over smoothly at about 20 psi and that will do for me. If it's a dog on steam or on the track then I'll have to revisit my decision! Something about repenting at leisure comes to mind.
I have Don's book in case I ever need to design my own so will have a look at what he says on this topic for interest's sake. The paper linked by Steve was pretty good. Hackworth gear sounds easy to make and tricky to set.
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mbrown
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Post by mbrown on Dec 2, 2019 7:28:11 GMT
Hackworth gear isn't really very tricky to set as there are few variables once it has been made. The tricky bit is that, because it can never give perfect valve events, it is easy to get carried away trying to chase elusive improvements, sometimes making matters worse (been there... done that...).
But take heart from the sheer number of miniature locos that do very well with Hackworth gear -set to "good enough"!
Malcolm
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smallbrother
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Post by smallbrother on Dec 2, 2019 10:15:35 GMT
Interesting comments but it went reasonably well to start so I feel I am justified in trying small adjustments at this stage. The slide valve movement was noticeably different on each side.
If I get nowhere then it will be time to recognize a more thorough approach is needed.
Again I have to emphasize the difficulty of working space. Any prospective builders of these large locos will do well to provide most of an empty double garage or its equivalent.
Pete.
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smallbrother
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Post by smallbrother on May 16, 2021 9:43:40 GMT
I transferred the loco to the club engine shed last Autumn and there it has been sitting since. I took the tender along yesterday to join it so I have cleared a bit of space at home, and running will just involve taking some tools and fan blower rather than a major physical work out which leaves me in bits.
I tried to steam up yesterday but found several problems.
The balance pipe connecting the saddle tank had split - presumably due to frost. A bit frustrating as there is a drain and there must have been no more than a millimeter of water left in there. Anyway, after a wrestle to remove it we repaired it with soft solder. Lesson for next Winter!
As steam built up a couple of other leaks appeared and these will need new gaskets made. The valve timing remains in need of attention too.
Anyway, despite some showers, it was mainly dry and quite warm , which made it a decent day out. Working on steaming bays with plenty of room and some more experienced people on hand makes life a lot easier than struggling at home with this large loco.
Pete.
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smallbrother
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Post by smallbrother on May 22, 2021 18:01:34 GMT
An absolutely wonderful day. An experienced hand kindly helped me start to tick off the snags.
We identified at least twice as many as we started with but they are all surmountable.
Another session next week as the weather looks fine again.
Really is a joy to be doing this stuff!
Pete.
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smallbrother
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Post by smallbrother on May 30, 2021 10:18:21 GMT
Another productive day at the club in fine company and lovely warm weather
We ticked off a number of snags and had a little run. The injectors are all but useless and a mysterious leakage of steam occurred from a cylinder.
On investigation it seems a strange repair was carried out around a drain-cock hole. There is a small plate screwed to the cylinder casting. Over the Winter a number of things have come to light so perhaps something didn't like the cold storage. Anyway, we think a new draincock with a longer thread up into the cylinder casting will cure this leakage.
I'm going to fit new injectors. Also the blower pipe seems to be another victim of Winter storage so a simple repair required on this.
She ran quite nicely for a few hundred yards so I think we are not far off the end now!
Pete.
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smallbrother
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Post by smallbrother on Jun 4, 2021 9:32:35 GMT
I am waiting for hex stock to be delivered so I can make a new drain cock that matches the original. Meanwhile I have made a temporary one out of some bar.
I have also collected 2 new 60 oz injectors made by the very reliable Mr Len Steel. These are for 1/4" pipe so I will have to make connections to the existing 5/16" pipe.
If I can get all this fitted and cure the blower pipe tomorrow I will have another chance to steam up. Good motivator but I don't want to rush and make a mess of any part of it.
Pete.
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smallbrother
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Post by smallbrother on Jun 5, 2021 22:31:22 GMT
Not a great day. Some friends are going through an awful time and my heart was just not in it today. I just wanted to get home and be with my family.
Also had some duff information on the pipe sizes for the new injectors so didn't even have the right materials with me. One thing I got right was cutting the thread on my temporary drain-cock. Having read the advice on this forum I clearly set up the bar stock and the die correctly in the lathe and produced a decent thread. It fitted very snuggly.
Always another day for the other bits and pieces.
Pete.
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smallbrother
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Post by smallbrother on Jun 13, 2021 7:55:34 GMT
Quite a few minor leaks still to resolve but we managed to fit one of the new injectors (60 oz jobbie by Len Steele). Worked first time and so took it for a lap of the track. I went quite slowly and it steamed like a witch, so kept the fire-door open.
Encouraging but still lots to sort out.
Pete.
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smallbrother
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Post by smallbrother on Jun 16, 2022 11:17:25 GMT
Well some progress on this engine.
Injectors (Len Steele) fitted and work 100%.
All leaking pipes replaced, draincocks all sorted and working.
Raises plenty of steam but safeties need a clean as they are now accumulating.
We've been puzzling over 2 issues for some time. There is an amount of stiffness when we push the engine along, and there is a dead spot when it comes to moving off.
Yesterday I stripped off the front cylinder cover and the con-rod and coupling rod from the side where we think the stiffness is. The piston was found to move quite freely but there was still a stiffness until the coupling rod came off.
I then tried to replace the coupling rod only to find it was the wrong length by about 1/16"!! I rolled the chassis so the crank pins were in a different position and it went on fine. The rear bush is worn to an oval shape. So, a definite problem here.
I was on my own so left it at that.
Wondering if the 1/4ing is out.
Pete.
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Post by chris vine on Jun 16, 2022 19:50:30 GMT
Hi Pete,
The quartering might be out, but if the coupling rod is not the same length as the axle centres, then that can certainly cause binding in part of the cycle.
You can alter the length of a coupling rod: If it is too short, you can find a really stout piece of metal then make a pin to locate one end of the rod and find a big clamp, or vice to nip the other end to the metal plate/bar. Slack the clamp and heat the centre of the rod to red heat and then clamp the end. As it cools and shortens it will be stretched.
I had to do this on Bongo's coupling rods as they changed length as I milled most of the metal from the blanks. From memory I changed their length by around 1/32" per heat.
If they are too long, then clamp while heating to red heat and unclamp while cooling.
This is all much more fun (and prototypical) than messing around with eccentric bushes etc. In the old steam works, rods and valve parts were sent to the forge to be "bumped" to the correct length. The old smiths would know exactly how many bumps and with which sledgehammer to achieve x/64s of an inch as indicated with chalk marks on the rods from the erecting shop.
Have fun with the black arts!!
Chris.
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smallbrother
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Post by smallbrother on Jun 16, 2022 21:11:25 GMT
Hi Pete, The quartering might be out, but if the coupling rod is not the same length as the axle centres, then that can certainly cause binding in part of the cycle. You can alter the length of a coupling rod: If it is too short, you can find a really stout piece of metal then make a pin to locate one end of the rod and find a big clamp, or vice to nip the other end to the metal plate/bar. Slack the clamp and heat the centre of the rod to red heat and then clamp the end. As it cools and shortens it will be stretched. I had to do this on Bongo's coupling rods as they changed length as I milled most of the metal from the blanks. From memory I changed their length by around 1/32" per heat. If they are too long, then clamp while heating to red heat and unclamp while cooling. This is all much more fun (and prototypical) than messing around with eccentric bushes etc. In the old steam works, rods and valve parts were sent to the forge to be "bumped" to the correct length. The old smiths would know exactly how many bumps and with which sledgehammer to achieve x/64s of an inch as indicated with chalk marks on the rods from the erecting shop. Have fun with the black arts!! Chris. Thanks Chris. We are digging out a long calipers to measure distances over the crankpins. See what transpires. Pete.
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Post by doubletop on Jun 22, 2022 9:36:13 GMT
Are the coupling rods he same length? Take them off and put them side to with a pin in each end going through both bushes. You may find that it isn't as case of one rod being too long, the other one could be too short.
But first measure the axle centers, not the crank pin spacing, that will tell you what the couping rod centers should be. Do it on both sides as it could be the horns aren't aligned or the axle boxes don't have the axle going through the centre. It could just be case of flipping the coupled axle to get the wheel centers the same on both sides.
Pete
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smallbrother
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Post by smallbrother on Jun 27, 2022 20:28:30 GMT
Are the coupling rods he same length? Take them off and put them side to with a pin in each end going through both bushes. You may find that it isn't as case of one rod being too long, the other one could be too short. But first measure the axle centers, not the crank pin spacing, that will tell you what the couping rod centers should be. Do it on both sides as it could be the horns aren't aligned or the axle boxes don't have the axle going through the centre. It could just be case of flipping the coupled axle to get the wheel centers the same on both sides. Pete Very sensible suggestions and they are pretty much what I decided to do while I was sunning myself in Spain this last week. A busy week ahead for me so I'll post progress in due course. Pete.
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smallbrother
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Post by smallbrother on Aug 5, 2022 15:34:50 GMT
I won't go into the details of all I tried because I'm not entirely sure what I did that sorted the problem of stiffness out.
Anyway having found it now rolls freely again, I took the opportunity of a rare Friday working day at the club and steamed up.
Made bags of steam, injectors both worked and away she went. Not the even beats I wanted to hear but I can work on that.
The safety valves aren't performing well despite a good clean up so 2 are on order.
I am very pleased.
Pete.
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smallbrother
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Post by smallbrother on Aug 27, 2022 20:52:29 GMT
After a complete failure last week to get the new safety valves to perform, I slackened them off and slowly adjusted them to increase the pressure required to lift them. After a bit of to and fro they eventually coped admirably with a trial accumulation test. Blowing off fully at WP of 100psi and the pressure not rising at all.
Went for a run and the fire and pressure built very nicely up the steepest gradient on the track. Not the most perfect sound when she runs but if it makes steam like that I can't see it is worth messing about any more.
Only downside of the day was indifferent performance of the injectors. These are almost new and by Len Steele so I have brought them home for a bath in citric acid.
I'm hoping I'm almost there with this engine after 6 years. What to do with it is the next question! Keep or sell?
Pete.
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smallbrother
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Post by smallbrother on Sept 24, 2022 18:20:38 GMT
Here is Tan Draig after a successful run today. Only taken me 6 years but at last she is up and running. Been a case of one step forward and 0.9 steps back, every inch of the way. Never mind, makes steam like crazy and very relaxing to drive. Pete.
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smallbrother
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Post by smallbrother on Nov 11, 2022 18:00:48 GMT
Very nice weather today so took her out of the shed for a look at the valve timing.
Last time we did this we hadn't resolved the weird suspension issue on the rear left axle box. So no surprise the valve was nowhere near doing what it should. We adjusted it and I will steam up tomorrow to see how she goes. Really looking forward to this.
Pete.
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