Slide Valves

[mott]

Hi guys, I ve just been reviewing the threads on the 14XX to see if any can have a bearing on my current problem.My loco has been steaming but poorly, converting lots of water into steam but evidently not through the pistons. I have demonstrated the problem and everyone has agreed that the slide valves were not bedding against the seats and steam was going straight to exhaust. I stripped out the valve chest and found that the slide valves were indeed sticking in the buckles. I cleaned everything up, polished and even did some judicious filing to ensure the valves would fall out under gravity when the buckle and cylinders are turned over. All ok just like when first assembled.Chassis reassembled, valves re-timed and test on air only to find air still coming out of the blast pipe when the wheels are stationary and the reverser is in mid setting. How can this be? Is it the buckles? I have had a suggestion that the buckles can twist out of the vertical during running and cause the valve to break its seal - result is poor steaming, high water consumption etc.What should I check next, the valve rods are straight, though why they have springs on I don't know and the timing is at least approximately right,I ve capped off the drain plugs for test purposes whilst running on air. Some observers at the club say the valve rods should not be clamped to the extensions with the nuts either side but lock nuts should be used so the rods are just free to turn and let the buckles bed in. When examined through a magnifying glass the valves look to seat perfectly on the steam chest.
Any thoughts? I am at a bit of a loss as to what to try next! Mott

[Phil Sutton]

Hi Mott.I would have thought that the valves would have "floated" in the buckles.If they were too tight a fit then the valve perhaps would n't seat properly.There should be no rotary motion in the valve rods as such,because they just move back and forth.If there is air coming up the chimney in mid gear,there must be a leak round the valve,and presumably also in the pistons.
Cant understand what the springs are for on the valve rods though.What do Modelworks have to say about it?Can't think of any thing at the moment,will have to go away and consider!

Phil

[greasemonkey]

Hi Mott
Sound like the valves aren't 'lifting' to seal against the port face! Try putting a piece of bronze strip bent to act like a spring (think humped back bridge) into the valve chest to apply gentle pressure against the valve lifting it into contact with the port face. I have a freind who had a similar problem with his 'Pansy' until he modified it in a similar manner.
cheers
Andy

[gwrfan]

Hi All,

I have a Pansy, and can confirm that this works! I also drilled the steam chest cover for a small screw, for adjustment of same bronze strip. Never had a problem since.

Regards.

Geoff

[sjtown]

Mott,
This is one of the greatest and most irritating problems of all for the winson models in my opinion…..Unfortunately!

I take it you've read my bit about the slide valves in the problems list thread...
The only thing I can expand on from what I have previously written is that now mine has run with cast iron rings, new valve rods and machined valve faces to make sure they’re 100% flat it will still on the odd occasion when opening the regulator (while pulling off or rolling) by pass the cylinders and go straight up the chimney. To cue this I just open her up a bit more so the pressure in the chest pushes the valves against the face.

If they seem to seat fine then I’m not sure what the problem is, if you take it part (again!!) I would take the cylinder and valve chest block out of the frames with pistons in and move the valve rods in and out while air applied to see if you do get any sort of piston movement, give them a wiggle and try to feel what is happening in the chest. This is what I did originally and you can gain some idea of what’s what just by feel, honest!
Basically my best suggestion is to experiment with valve movements manually.

There’s no way it can be anything else other then the issues in the valve chest as if as I know, unless of course there’s a leak in the cylinders casting!

The only other issue is the valves lap, but mine should be the same as your as I’ve got the Modelworks cast iron valves which have a reduced lap over the winson ones

Steve

[mott]

Hi guys, justa thank you for the useful comments. I took the cylinders out of the frame and showed to some club members. No problems were detected so I am going to have another go having lubricated everything copiously. I guess the valves need a kick of steam to seat. maybe those buckles get a twist on and discourage the valves from laying flat - we shall see. I will follow up on Steve's suggestions if the problem persists. great to have your considered comments on my latest problem. Mott

[pannierstan]

Hi Mott sorry to hear about the problems.
I have just yesterday run mine on air with very good results. As you say it was drenched in oil but ticked over at just 25 psi and then down to 10 after a few minutes of running in ;D
Just one thing nobody has mentioned is the buckles themselves.
I made sure that the buckles had a bit of room to move about aswell as the valves.
I just gave them a touch with a file on the outside aswell as the inside.
Just a thought as it might be your buckles that are not allowing enough movement between themselves. Lets face it if there is no movement in something it will never bed in.
Another thing Mott I dont have any springs on the valve rods My destructions dont mention any either.

Stan

[greasemonkey]

HI All
If your going to make everything loose and sloppy be carefull as you will end up with reduced valve movement! If your valve only has a movement of 5/16 and you put a 1/32 of play in then that is quite a percentage of lost movement. The problem as I understand it is gravity! When you have no pressure in the chest the valves are going to fall away from the port face. Plenty of lubrication will stick them in place but ultimately you need a mechanical means of keeping them in their correct position. A blow of steam up the chimney is symptomatic of steam blowing past the valves.
In this instance lap will have no effect upon the problem, lap is a term used when describing a valve gear. Lap can be defined as the amount by which your valve overlaps the outside edges of the ports when in its mid gear position. During the early days of steam locos the slide valves just spanned the distance across the ports and didnt have any lap so the cylinders were always open to either steam addmision or exhaust. This meant that the steam was wasted as it didnt have any chance to expand. Lap was added to allow early cut off and thus allow the steam to expand and the engine to run more efficiently.
cheers

Andy

[pannierstan]

Thats right Andy.

Of course I wasn't suggesting they are slapping about like a dogs whatnot but certainly going back to what Mott was saying about them running tight in the buckles I also realised when put together that my buckles where tight in the cylinder blocks and just needed a delicate touch with the file to move nice.

Also made up some stainless steel valve rods aswell Tap cost 30 quid though
The standard ones felt like cheese to me and didn't seem to be straight anyway.

[greasemonkey]

Hi Pannierstan
You'd be supprised at the things some people will do. I remember seeing one engine at my local track that had so much play in the valve gear it would only run in full gear.

Andy

[pannierstan]

Oh dear

[locoworksnorth]

Hello all,

Just a quick thought, the older winson pistons are not only too small for the cylinders but the o ring groove was also wrong. The later pistons are slightly larger with larger o rings and suitable grooves. The easy way to tell.... they should be fairly tight untill they have done a few steam miles !
Make sure the bores are smooth otherwise those o rings are finished after 2 minutes on air anyway.
If youre not sure change em !
Hope that helps.

good luck !
locoworks

[mott]

Well this string goes on 'cos its interesting and because its probably a "known fault". We had the loco in steam today but in about 1 1/2 hours going round we never managed to get the valves to seat. We used amazing amounts of water and centrally heated half of Colchester.We could do about 200 yards before the gauge glass dropped and we had to dash over with the watering can to resupply. The theory was that eventually the valves might seal but it didn't happen though we could detect a slight improvement.Ian at Modelworks has been getting calls from me and has been has helpful as I would hope. He suggests running on air for a couple of hours to really give the buckles and valves a bit of work, also slacken the nuts on the valve rods in case they were inducing twist in the buckles. Another possibility was to remove the lubricating elbow into the steam chest and try to move the buckles about by tickling them up with an allan key or something but this too much hassle at present.The only thing which might be relevant is that the lubricator was not moving oil whilst we were running to-day. I have cast iron rings and did put some oil down the blast pipe when we were closed down to keep up the lube also pumping oil in through the drain valves. This problem now sorted and oil coming from the lubricator ok. One wonders about flushing the valve chest through with penetrating oil in case the valves need freeing up but they were pristene yesterday. Ian was familiar with soldering a bronze spring on the back of one of the valves bearing on the other to keep them pressed on to the port faces and I may have to go for that but that means another strip down and "lifes too short", The damn thing ought to work but it don't! Mott

[pannierstan]

I don't think the valves and buckles are a known fault as I have both a 57xx and a 14xx and both were fine after modification to the lap and are both the same cylinder block, but I agree with Locoworks that the pistons were indeed.

Just a thought but if your pistons were passing would that not produce a similar problem.

Cast Iron rings without oil is that not like a car engine without oil?

Has the lubricator never worked or only last time out??

The pistons and valves will have been rather dry without wouldn't they?? especially running on air

[mott]

Stan, We ran on air yesterday for more than an hour with copious lubrication but though there was an improvement in the "beat" it was really not much better. I just have one final thing to double check which is the valve timing. I know this is critical and we have fiddled about with the nuts to make sure the rods were not being clamped and twisiting the buckles. Obviously it can't be far out because she does run on air but maybe there's something here. Guys in my club are advocating putting inspection holes in the bottom of the valve chest to see what is happening to the valves but I will take it back to ModelWorks first because that seems a bit drastic and anyway it would need a strip down to do it. Ian seemed confident he can sort the problem. As to the pistons I did add oil though the lubricator was not functioning and anyway most of the time the loco was stationary.Earlier I had taken the cylinderheads and valves into the club and several very experienced members looked at the valves, buckles,pistons and rings and could find no fault, indeed rather the opposite they were complimentary of the whole lot.They though the finish of the bores was very good as well as the fit of the pistons/rings. I shall be off the air now for a few days for computer servicing. Best regards to everyone. Mott

[mott]

Further comment on this slide valve issue. I have opened up the valve chest and there is no problem of sticking valves or buckles. However what was obvious was that the valves were not being given enough travel. The travel should be the width of the steam port plus the lap x 2.This is 8mm, the port width being 3mm and the lap 1mm. The most accurate reading I can get from the movement of the valve extensions is that from front to back, movement is 5.5mm. With limited valve movement it is n't certain whether the valves are centering when the piston is at FDC and might explain why steam was getting from steam port straight to exhaust. How to increase the valve travel is a bit unclear at this time as there is no adjustment available to the eccentrics on the crank axle!! Mott

[Phil Sutton]

Hi Mott,when you fitted the valve gear together,did you file out the ends of the curved slots in the links? Mine were still rounded where they had been milled out,and filling them out square made a bit more travel on the valve rods in full gear.In fact it was possable to slightly lengthen the slots to ensure maximum travel.If you have not done this,it will mean a full stripdown of the gear unfortunately,to do it.

Phil

[mott]

Phil, Thanks for that point. I had picked it up from one of your earlier notes on 14XX issues. No my slot ends in the links are still rounded but from what we can see, travel of the die block is not impeded as the limiting movement of the die block is the travel of the reverser and maximum movement is used. I have had the expansion links out to make sure the die blocks were not binding. In the end the problem might come down to the linkage restricting full movement of the die block which would be easier to fix than problems with the eccentrics on the crank axle. One thing is now clear, the valves , buckles and pistons are fine and it looks very much that lack of valve travel is the problem. I can even see from the marks on the port face that the valve is moving from side to side about 5.5mm which coincides with my measurement of movement at the valve extensions. so somewhere in the linkage 2.5mm of valve movement is being lost. The guy from my club who has been oversighting my work was concerned to find that the inside of the valve was 0.5mm wider than the measurement between the inner edges of the steam ports, with the thought that this might allow steam to go from steam port to exhaust port without going through the cylinder. My guess is that ModelWorks will have a quick answer to put this timing issue to rights and then I can get back to some serious steaming.Mott

[baggo]

Hi Mott,
have been reading this topic with interest and hope you can get the problem sorted soon.

It is possible the valve is designed to have exhaust clearance ( in your case 0.5mm) although its not common in models. It was often done in full size locos to give a free exhaust by allowing the port to open to exhaust earlier and close later.

With regard to the amount of valve travel, Martin Evans in his book on valve gears suggests a travel of 4.5 times the valve lap to give a cut-off of 80% and 5 times the travel for a cut off of 85%. As your valve travel is 5.5mm and the lap 1mm, this gives a ratio of 5.5 so this should give a full gear cut-off of about 90% which should be more than adequate. Few valve gears are designed to give the full 100% cut-off as the amount of work done by the steam at the very end of the stroke is small due to the small angle between the connecting rod and the crank.

It seems a safe bet that your problem is due to the valves not seating properly. Excessive exhaust clearance or lack of valve travel may effect the loco performance but shoudn't cause your present problem. The only other possibility that I think was suggested earlier is that there is a hole in the casting between the steam and exhaust passages somewhere!

John

[Phil Sutton]

Hi Mott,It was a known fault in the Winson 1400 that the valve travel was limited,the eccentric throw was barely enough for the model to run,and everything has to be spot on to work properly.My thought was that Modelworks would have increased the eccentric throw to make things better.Still,good luck with any mods.

Phil