Porous Cylinder Castings?

[steamnovice]

Hi there experts.
This is my first post, so sorry in advance if I get things wrong or ask stupid questions. I have bought a 2nd hand Simplex via Flea-Bay and I am repairing its many minor faults. (I have steamed it 2 miles already so it does work). The engine was leaking steam straight up the chimney when the left side valves were open, but there was no steam leakage when the valves were shut. Ah ha I thought. The piston rings have failed. But sadly a strip down revealed a pair of healthy Silicone rubber O rings as piston rings which were sealing OK. The attached photo shows the valve pockets and ports cut into the top face of the left side gunmetal cylinder. It looks like the builder (sadly deceased, so not available to answer questions) had tried to use solder to seal the bottom of the cylinder pockets because the casting was porous? If I pressurise one end pocket with compressed air I get steam oil bubbling up out of the pocket at the other end (but strangely nothing appearing in the exhaust pocket in the middle). N.B. The oil bubbles out of the bottom of the pocket at the bottom of the picture a bit like a spring emerging from nowhere, it does not come out of the port drillings - so the piston rings aren't passing. I suspect that there is a Major porosity underneath the solder somewhere and steam pressure has lifted it so it leaks at one end. Now for the silly questions:
1. Has anyone else experienced porous castings?
2. How did they fix it?!! (I wondered about silver soldering a piece of brass into the bottom of the end pockets as there is depth to spare below the port drillings, but I don't know how much heat distortion this might introduce into the cylinder)
3. How do I get one cylinder off to work on it? (This looks like a major job to me involving removing the boiler first)
4. How do you unscrew and remove the steam and exhaust headers from the back of the steam chests and cylinders? Is one end a left hand thread?
Sorry, but I did warn you that my questions might be silly. That's enough for today. Thanks for reading.
Regards
Peter

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[davet]

Hi Peter

I'm no expert and I am just in the process of rebuilding a Simplex, this one is quite worn and needs a lot of TLC to the motion works, bushes, boiler and fittings.

I have the boiler off my Simplex at the moment and I wound say it is possible to remove the cylinder with the boiler in place but :

• You will need a stand that can support the loco and rotate it upside down.
  
• A good set of BA spanners, sockets, tube spanners etc and a good supply of sanity pills, in my case Tiger beer liberally applied at the correct intervals.
  
• The steam and exhaust pipes from the cylinders should have a locknut next to the central T piece, loosen the lock nut and then screw the pipe into the T piece. This then screws the pipe out of the cylinder. That worked for me.
  
• The other questions will have to be answered by others, I have no experience of solder/brazing cast iron. But others have had good success in sealing boilers with a Loctite product. I think Greenglade or Baggo has used this technique.
  

While the loco is apart I would have a close look at the various pins and bushes in the valve gear, rods etc and this is a good time to replace.

Kind Regards


DaveT
Kuala Lumpur

PS Peter

Just did a search, look half way down this page for the info from Baggo.

modeleng.proboards.com/index.cgi?action=display&board=general&thread=5933&page=1

[steamnovice]

Hi Dave

Many thanks for your reply. It's good to know that there are fellow sufferers out there. You are dead right about wear in pins and bushes. There is so much lost motion in my valve gear that one of the steam ports won't open at all in reverse! And by my observations, to get full travel of the lifting arm in reverse I would need to cut a hole in the footplate and the bottom of the water tank to allow clearance for the end of the radiius rod?

The trouble is I'm trying to avoid pulling the model apart completely, as I want to play with my new toy.

Incidentally I've got gunmetal cylinders not cast iron.

Thanks for the Loctite suggestion and the link. I'm impressed with the performance of 'engineering glue' these days but I was nervous using it in contact with steam due to the drop off in glue strength with temperature. Most datasheets seem to give a top limit of 150 degC. Now with 80 psi steam the saturation temp is approx. 160 degC, add say 10deg for superheat gives 170 degC which I thought was too high to risk using glue? Obvisously this is where experience overules manufacturers' caution.

Isn't it wonderful to have this kind of experience on tap. How did we manage before the internet? NO, please don't answer that....I'll get spammed out of existence! LOL.

Thanks again for your advice.

[davet]

Hi Peter

I would have a good chat with Baggo as he used the Locktite product to seal a leaking stay on that steel boiler, the only issue I see is that in the steam ports the steam would be superheated, need to work out the exact source of the leak. I wonder where the crack/hole is, between the exhaust port and the cylinder wall or the exhaust port and the inlet ports to the ends of the cylinder.

Do you know anybody that uses the crack dye penetration system, that should show where the problem is and then go from there.

For the loco stand for the Simplex have a look on DrJohns web site

www.dr-john.org/index.html

Goto the Simplex section and on Page 11, the top of the mounting frame is shown and the connection to the buffer beams in one of the pictures. Before turning the loco upside down I would make real sure the boiler is firmly attached to the frames.

There are more pictures of the stands as you go through the good Dr's build sequence.

I am stripping the simplex down to do a good rebuild, yours sound the same as mine, quite worn in the pins. I am looking to make all ne pins and drill out the links for small bronze bushes, at least they can me replaced in the future. The other thing to look out for is the build, my Simplex is not build totally to the plans, for example threads have been changed, pins are different diameters (to the plans and from LH side to RH Side), I would measure and document all as you take it apart.

Good luck and have fun.

Regards

DaveT
Kuala Lumpur

[baggo]

Hi Peter,

I don't think the Loctite method stands much chance in your case. The problem is that the porosity in the casting will now be full of oil and it will be extremely difficult to get rid of it. I think your best bet is to go down the soft solder route again.

Your going to have to get the cylinder off no matter what you do. It is a pain but it can sometimes be quicker in the long fun to remove the boiler. I've spent hours fiddling about trying to get at difficult to access bolts etc. when it would have been easier and quicker to bite the bullet and remove the boiler.

I wonder what sort of solder was used in the first place? If it was ordinary electronic type solder, it may have melted when the engine was working hard and bubbled up leaving pin holes. Cylinders with high superheat do get VERY hot! I've measured the cylinder temperature on my Helen Long and it was way over 150° C (the limit of the thermometer I had).It really wants doing with a high melting point solder such as Comsol (300° C) or Carrs High temperature solder (243° C).

I'd recommend stripping the cylinder and heating it for a while to try and drive as much of the oil out as possible, then resolder with plenty of liquid flux such as Bakers fluid to really clean the metal. Maybe a dunk in a pickle bath after heating and before soldering as well. You could put some thin brass in the bottom of the ports to make a more solid job of it, as you suggest.

Good luck!

John

[fostergp6nhp]

For removing the oil, before any heating try soaking the cylinder in brake & clutch de-greaser/cleaner for a while. Remove and drain every so often and then back in the soak.

[steamnovice]

Hi guys

Many thanks for taking the time to advise me - there is some really helpful advice there which has given me the confidence to go further.

As a novice it is incredibly valuable to get good advice from experts. I'm glad I plucked up the courage to make my first posting.

I will post my progress at finding and curing the leaks, but don't expect quick results as modelling time is limited, and what I laughingly refer to as my workshop is a bit of a disaster area (see photo).

Thanks again.

Peter

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[peteh]

Hi Peter,

Wouldn't worry about your workshop - wait to you see mine!

[davet]

and mine !!!!!!!!

DaveT

[pault]

Hi Peter,
You may well have a porosity issue with your cylinders but I doubt that it would give a significant blow up the chimney. I would suspect the port face and possibly the valve. There seems to be some foreign object damage on the face and I would suspect on the valve as well which would give you a blow from live steam to exhaust. I would look at getting the faces and valve in good condition first and see if that improves things.
Regards
Paul

[steamnovice]

Hi Paul

I thought much the same as you initially, and even now I can't quite convince myself that a few bubbles of steam oil indicate a porosity leak big enough to hear and feel as air flow up the chimney when tested at only 50 psi on air. Both the slide valve and cylinder mating faces have fairly significant scratches in them (apart from the other damage you can see) but before dismantling I positioned the slide valve mid-travel and there was no leakage up the chimney at all. So the steam oil was enough to give a seal. OK it's theoretically possible that the raised sections of cylinder face between the pockets could have worn lower and they're giving some blow-by, but I just can't believe that is the case.

I have polished out the scratches on the slide valve quite easily using 600 grit wet and dry then Solvol Autosol. When I finally dismantle the cylinder from the frames (circa 2013) to fix the leak I might try some engineer's blue on it just out of academic interest before I polish out the scratches in the cylinder.

I must admit that this has me foxed. I thought I'd found the answer when I found solder in the pockets - clearly the builder was trying to seal something. But like you I can't convince myself that a bit of porosity could give significant air flow? I even checked the cylinder bore to see if he had broken through when machining the pockets but there's no visible evidence of that.

She still steams despite the leak, but I want to fix it, for reasons of power, efficiency, and personal satisfaction. Trouble is my Myford and Emco miller are still in packing cases after we moved down to the SW and are unlikely to see daylight for another 9 months.

Patience...patience...

One last thought....they make filter elements using sintered bronze...and that has a significant flow rate through it.... Hmmm, sintered gunmetal cylinder castings? NO! HELP!

[pault]

Hi Peter
Was it a blow up the chimney regardless of wheel position or only in certain wheel positions?
Regards
Paul

[steamnovice]

Hi Paul

There is only blow up the chimney in certain wheel positions.

I have removed one safety valve and applied low pressure compressed air to the boiler. Then by turning the wheels slowly by hand I can feel when the ports open and close. I get a blow up the chimney when (and only when) either of the cylinder ports on the left hand cylinder is open. As soon as the slide valve closes either of the left hand cylinder ports, the blow up the chimney stops.

That's what made me think it was piston rings passing in the first place, as if they had been leaking that would provide a direct path from the working side of the piston to the exhaust side and hence lots of blow up the chimney. But the rings were fine, which I proved by inspection and also by disconnecting the crosshead and pulling the piston a bit with the slide valve in mid-position. When released the piston would spring back into its at rest position indicating a good seal was being achieved both by the piston rings and the slide valve.

I'm still backing a stonking amount of porosity in the cylinder casting, but it is strange that it only connects the two end ports at present. Perhaps it is a channel that runs the full length of the casting (including the exhaust port in the middle), but the builder succeeded in sealing the exhaust port pocket, but the higher temperature of steam entering the two steam supply pockets has melted the soft solder? The casting appears intact at both ends where the mating faces for the end covers have been machined.

Dr John suggests that I should use a proper metal like cast iron instead of girlie gunmetal for my cylinders. Either way its serious money for some new castings and a 9 month wait until I can start machining.

Ho hum...

[baggo]

Hi Peter,

It could still partly be a problem with the port face as Paul suggests. It is badly damaged and the seal may break when the valve moves off centre. The port face may have worn unevenly causing similar problems. It really needs lapping flat again by rubbing it on carborundum paper on a flat surface. I've restored quite a few scored port faces using that method. There might be a lot to take off though so you'll have to be careful not to finish up with a convex surface.

John

[ettingtonliam]

Just a thought, but have you checked the size of the exhaust pocket in the left hand valve? If its too big, you could have the valve opening to exhaust far too early, and might be another explanation for a blow to exhaust as soon as either end port is open.
In your first posting you suggested a possible fix by silver soldering a piece of brass into the steam pocket. Sorry, but thats not on, once soft solder has been used, you can't silver solder at the same place, unless you can get all traces of the soft solder off first, which I don't think will be possible from those pockets. Baggo suggested Comsol, which is the ideal material, but I'm not even sure if you can use Comsol on top of a lower melting point soft solder. Its not something I'm sure about, maybe someone else can comment?

Richard

[baggo]

Richard, my thoughts were that the Comsol or whatever would alloy with the original solder and hopefully still produce a higher melting point product than the original. Probably best to try and get rid of as much of the old solder as possible.

Agreed you won't be able to silver solder it but that would probably distort the casting anyway with the heat required. I did read something the other day in one of our 2½" journals that if you use lead free solder i.e. plumbing solder, that may not cause a problem with subsequent silver soldering as it doesn't contain any lead?

John

[steamnovice]

Hi Richard

No it's definitely not a case of the exhaust port opening too early (or closing too late). I have taken 5 photos of my newly polished valve slide resting on the ports in various positions and exposures in the hope that you can see. I had so much lost motion in worn pins and bushes + lack of travel with the direction change mechanism that the valve ports are only uncovered 50% at best!

Unfortunately I don't know what kind of solder was used and the builder is no longer alive to ask.

I've got a job list as long as my arm to get this loco ship-shape!

I'll just keep pressing slowly on.

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