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Post by steamer5 on Oct 19, 2019 21:10:49 GMT
Hi Pete, Keep at it you’ll beat it! If it’s any help I use orings to seal my gauge glasses. Work a treat.
Cheers Kerrin
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smallbrother
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Post by smallbrother on Nov 18, 2019 9:36:13 GMT
Managed to get another run (2nd since re-commissioning) at the club on Saturday.
Not too bad but 2 items need attention. The timing isn't right so I will get the covers off the valve chests and see what's what in there. She also needs one of the valve rods re-packed with graphite yarn as it leaks significantly.
Otherwise looking quite promising.
Pete.
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smallbrother
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Post by smallbrother on Nov 21, 2019 21:56:59 GMT
Well I took the covers off the valve chests and after setting up some track at a decent height checked the movement of the valves.
One of them appears fine but the other one is tracking the piston movement rather than doing the opposite. Not sure how it runs at all like this.
Some head scratching required.
Pete.
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Post by coniston on Nov 21, 2019 22:20:43 GMT
Isn't it amazing how even a poorly steam engine/loco will still work to some degree. look forward to hearing your diagnosis and remedy.
Chris D
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smallbrother
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Post by smallbrother on Nov 26, 2019 13:46:07 GMT
I have spent several days rolling the loco back and for and have concluded things were not as bad as I thought.
I have therefore adjusted the LH slide valve to do what the RH one was doing, as the RH one was equally placed over the ports.
Obviously this assumes the RH set-up is correct. The LH one was nowhere near even, so will put things back together and if the weather holds up give it another run on Saturday.
Pete.
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stevep
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Post by stevep on Nov 26, 2019 18:39:59 GMT
Pete,
There are many on this forum better qualified than me to advise you, but as far as I see it, there are two aspects of the valve movement that you need to be interested in.
1) The valve should open the same amount at each end of its movement. The spacing of the ports and the length of the valve is obviously important, but if they have been machined accurately, you need to ensure they open equally. The two ends of the cylinders are basically symmetrical, so the valve movement should be the same.
2) The valve should open (and close) at the right time - and this is controlled by the valve gear and how it is set. I tried to look at your pictures, but Photobucket are making them blurred. The MJ Engineering web site says this engine is fitted with Hackworth valve gear, and this is reasonably easy to set, as you just need the return crank at 90 degrees.
So setting one side (which isn't working properly) to be the same as the other (which is) is sound reasoning. Just check the return crak settings each side too.
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smallbrother
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Post by smallbrother on Nov 26, 2019 20:18:01 GMT
Pete, There are many on this forum better qualified than me to advise you, but as far as I see it, there are two aspects of the valve movement that you need to be interested in. 1) The valve should open the same amount at each end of its movement. The spacing of the ports and the length of the valve is obviously important, but if they have been machined accurately, you need to ensure they open equally. The two ends of the cylinders are basically symmetrical, so the valve movement should be the same. 2) The valve should open (and close) at the right time - and this is controlled by the valve gear and how it is set. I tried to look at your pictures, but Photobucket are making them blurred. The MJ Engineering web site says this engine is fitted with Hackworth valve gear, and this is reasonably easy to set, as you just need the return crank at 90 degrees. So setting one side (which isn't working properly) to be the same as the other (which is) is sound reasoning. Just check the return crak settings each side too. Hi Steve, Yes it is Hackworth valve gear. It ran as it was so I don't think it should be a million miles out. As far as I can tell the valves are now opening the same amount at each end of movement on both sides. Will report after the next run. Pete.
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mbrown
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Post by mbrown on Nov 26, 2019 21:19:47 GMT
Hackworth valve gear can actually be a bit of a swine to set as changing one element can throw other bits out. It is vital for good events to have the position of the slide block shaft set correctly when designing the loco in the first place. Movement of the axle up and down on the springs can seriously affect the events and one possible cause of inequalities between left and right might be the level of the axleboxes in the horns being different... Getting fore and back gears both working equally well with Hackworth gear is extremely difficult because the necessarily short vibrating lever (connecting the return crank to the slide) creates angularity issues.
That said, if you can live with a bias to one direction, and aren't too fussy about getting precisely even beats, Hackworth can be made to perform quite acceptably. But do check the position of the slide blocks in the slides at mid travel and see if they are roughly the same on both sides. Setting the springs to give (effectively) no travel to the valve when you are on dead centres and move the reverse from fore to back gear is a good check.
Hope this helps.
Malcolm
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smallbrother
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Post by smallbrother on Nov 26, 2019 22:00:46 GMT
Hi Malcolm,
She is fitted with the stiffest springs we could sensibly fit.
I am not at all bothered about performance in reverse, as long as it moves that's fine by me. The one valve was noticeably out of symmetry. I will start with this adjustment and see if it helps.
Pete.
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Post by andrewsleigh on Nov 27, 2019 3:57:36 GMT
mine has the sofest springs, doesnt really affect the performance, shes still a beast!
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smallbrother
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Post by smallbrother on Nov 27, 2019 9:23:48 GMT
mine has the sofest springs, doesnt really affect the performance, shes still a beast! Indeed she is! Does she pull that lot with passengers? Mine is up and running after a number of years (at least 7) in bits. It would have been a very big surprise if it had performed 100% from day one. However, she makes steam safely, injectors, blower, brakes, whistle all work, goes in both directions, can't be far off methinks. Forecast is looking ok for a run on Saturday so let's see what happens. Pete.
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Post by andrewsleigh on Nov 29, 2019 2:44:09 GMT
pete
she can do 3 fully loaded coaches fairly easily. i have yet to give her a proper work out as our track is only a small circle.but she ran for many years at hollycombe with 2 or 3 coaches no problem
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smallbrother
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Post by smallbrother on Dec 1, 2019 10:09:41 GMT
AArrgghhh. I have made it worse. Also another steam leak is visible this time from a cylinder gasket.
At least the gland packing I did has worked - this was previously masking the gasket leak.
Not sure whether to leave it all over winter until we get longer days back. By the time I get to the club and raise steam there is no time to dismantle anything and experiment.
Pete.
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Post by David on Dec 1, 2019 11:10:10 GMT
That sounds really frustrating Pete. What Steve says above about setting valves is exactly what I do for both my locos but neither of them have Hackworth gear and I don't know how you adjust the timing with that. But the two main points must be the same - equal openings which you think you have, and having the ports open as close to the correct moment as you can. A question for everyone else - if you can't get the ports to open right when they should is it better to have them open slightly early or slightly late? For the timing I use the position of the crosshead. When it's right at the front of its travel then moving the wheel any more in the appropriate direction (depending on whether you're setting forward or backward) should start the crosshead moving back and the valve should just show the edge of the front port to allow steam to enter and push the piston the other way. Same for the crosshead at its furthest point to the rear and the rear port. Sorry that's not much help but if you got point 1 done, you should be able to work on point 2 and run it on air for testing. Soapy water will show up leaks and you should be able to get an idea of how smoothly it runs with compressed air. I spent all last week doing just this. I guess Malcolm's point that point about the vertical position of the wheels might affect the running if it's up on blocks but you have to start somewhere. Here's a couple of pages I found for timing it. www.roundhouse-eng.com/ss09.htmukprsl.uk/moc/mods/dixie-hackworth-gear.htm
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mbrown
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Post by mbrown on Dec 1, 2019 12:17:02 GMT
It's very difficult to tell where front or back dead centres are just by watching where the piston rod stops moving. There is a simple accurate way to find FDC/BDC which is set out various places including Don Ashton's books. It's harder to describe in words than to do....
Essentially, turn the wheel in one direction until the piston is almost at full stroke and make a mark on the slidebar - then make a mark on the crosshead which lines up with the one on the slidebar. Then make a mark (centre dot) on the outer rim of the wheel (the tyre or the flange, whichever is most convenient) where you can either line it up with a dot on the frame or can use a pair of dividers to set the distance from the mark on the frame to the mark on the wheel. Then go on rotating the wheel in the same direction until the crosshead starts moving in the other direction and the mark on the crosshead once again aligns with the mark on the slidebar. Now find the mark on the frame again and make another mark on the wheel at the same distance from the frame mark as the first one. The two marks on the wheel will be a distance apart - bisect that difference and make a third mark. As you rotate the wheel (always in the same direction) this middle mark tells you when you are at the true dead centre. As I say, much easier and quicker than it sounds in print....
Having found dead centres, there are not many adjustments you can make with Hackworth gear. First you need to set the axle height so that when you move the reverser from fore to back gear there is no movement of the valve rod - actually, the in-built errors in Hackworth mean that this may not lead to the optimal events, but it is a good starting point. Then set the position of the valve on its spindle to just give the correct amount of lead to the valve. Basically, those are the only two adjustments you have - so if the valve travel is very uneven, try slight adjustments to the axle height and to the position of the valve on the valve rod until it starts getting better.
With Hackworth gear, you are not going to get even valve events in both fore and back gears - on the Talyllyn, No.4 "Edward Thomas" which has Hackworth gear, is set to give good events going forward and we can notch up right to mid gear. But in reverse, wherever you set the reverser, it is very off beat. We could have got better back gear events at the expense of fore gear, but as the great majority of the work is in one direction, we got fore gear right and let back gear take care of itself. Even so, in fore gear she doesn't clip the bests off evenly like No.6 "Douglas" with its Walscaerts gear - No.4 has a distinctive galloping beat.
You may find eventually that you can't get the valve events any more equal - and this might be because the slide block shaft is not positioned correctly on the frame. I know there is a problem here with Sweet Pea, but just as with Romulus there are an awful lot of locos built to those designs which work OK, so it is probably not worth chasing perfection.
Hackworth gear was designed to be cheap, easy to maintain and with no low-slung parts to get bent if debris is left near the track - rough and ready shunting in rough and ready industrial premises - perfect valve events were an expensive luxury! But the limited length of the vibrating lever - the vertical rod from the return crank to the die block - introduces angularity errors that can't be easily avoided.
Hope this helps.
Malcolm
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Post by springcrocus on Dec 1, 2019 14:37:12 GMT
I covered finding dead centres for my Britannia HERE if you want to look. It is not specific to Walschaerts. Regards, Steve
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stevep
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Post by stevep on Dec 1, 2019 15:10:09 GMT
What Steve (springcrocus) describes is about the most accurate way of finding dead centres. I used a similar system, but put a toolmakers clamp on the sidebar, rather than using a dial gauge, and turned the wheels until the crosshead touched it. Just a bit quicker to do.
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smallbrother
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Post by smallbrother on Dec 1, 2019 21:53:07 GMT
Those tips are much appreciated. As I say, I think I will leave it until we get longer days. Take the loco down the club and use the steaming bays to work on it under the supervision of experienced people. My facilities are much too cramped for this large loco. I did a similar job with the slide valves on our 5" Polly a few years ago and it was a piece of cake in comparison. Shoving a 1/4 tonne loco back and for in not much space is not much fun.
The job I can do over the winter is look at the cylinder gasket leak.
Pete.
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jma1009
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Post by jma1009 on Dec 1, 2019 22:12:39 GMT
Hi Pete,
You cannot set valves by looking at how far they open on each side of a loco.
mbrown (Malcolm) has shown the vital importance of assessing the die block position either side of the loco, and the vital importance of accurately establishing FDC and BDC, and that the Don Ashton method is superior to that of Steve (springcrocus), and certainly David's approach.
Malcolm has also suggested you check the return crank settings and the axlebox heights on the driving axle.
No one can set valves by rolling a chassis along a piece of track with the steam chest covers off looking at just how the valves seem to open the same amount. There is a lot more too it than that!
Cheers,
Julian
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Post by David on Dec 1, 2019 22:12:51 GMT
I found watching the crosshead worked well enough. I'm very 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.
An edit to say the PDF linked to on Steve's thread is very interesting. The author seems to say a very similar system was used in full size. It also emphasises the importance of getting the axle with the conrod at the correct height which I didn't worry about.
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