Steam leak from reverser block

Joe · Post by **Joe** » Fri Mar 20, 2015 5:08 pm

Well i finally got round to fitting a RWM reverser block in but....... unfortunately when i put the regulator up steam escapes from around the left cylinder and the loco finds it hard to move-and when it does get going the steam still escapes. any ideas why? do i need new cylinders or does the valve timing need sorting? etc?
I have to say though the new block is more controllable and better quality
than the old one
cheers
Joe

DLRdan · Post by **DLRdan** » Fri Mar 20, 2015 6:00 pm

It might be that one of the pivot bolts is resting on a pipe, this does happen on the odd occasion. The other possibility is that the bolts holding the cylinder and back plate on are too long, so the cylinder isn't being held tightly against the frame.

Joe · Post by **Joe** » Mon Mar 23, 2015 10:20 am

Well after a bit of a fiddle it was obvious the one cylinder had become loose from the chassi as the spring was loose compared to the other one but when i tried tightening it up i wasnt sure if i was tightening it or loosening it i know noramlly you turn the spanner right to tighten it but im not so sure with this one. any ideas?

by the way its the cylinder at the top which is loose

Big Jim · Post by **Big Jim** » Mon Mar 23, 2015 12:14 pm

I don't think these have a 'chinese' thread on them. Keep going, it will either tighten or fall out. Unless there is a stripped thread in there.

DLRdan · Post by **DLRdan** » Mon Mar 23, 2015 12:59 pm

The pivot bolt is definaltly loose and is resting on the steam pipe how ever the bolt that holds the reverser doesn't look like its all the way in. If the cylinder still isn't touching the port face when the bolt is done up then you will need a shorter bolt.

Joe · Post by **Joe** » Mon Mar 23, 2015 2:07 pm

Thanks for the advice guys, I think the screw holding the reverser together is tight enough as ive just had it of roy wood; i kept unscrewing (to the right) the cylinder and eventually the cylinder fell off, heres the offending article:

I noticed that the two cylinders are different and this one has a hole at the one end which i haven't seen on other mamod cylinders; i think i may need new cylinders so will probably email RWM- i think i only need new ‘O’ ringed piston and cylinder set from him and then hopefully no more issues as i will have replaced all the parts in that area!. If i can just srew it back on and it will work then i will but if not i may as well invest in some from rwm.

Chris Cairns · Post by **Chris Cairns** » Mon Mar 23, 2015 6:40 pm

A-ha, so I was right.

Chris Cairns wrote:Cylinders - Had a closer look at the eBay photos again. The right cylinder is an earlier MSS one where the cylinder end cap that the piston rod runs through has an additional face (thicker) to reduce the wear effect caused by the lateral/vertical motion of the piston rod. Difficult to be exact (due to the cylinder cover) but the left cylinder appears to be the current style of MSS cylinders. That end cap is flat (as they were on the Mamod SL ones) and there would be an identical cap on the other end with the hole blanked off with a blind copper rivet. There have been reports of those rivets fouling the piston inside the cylinder which will affect the running.

So the loose cylinder is the current version from MSS with that blind copper rivet in the hole, and the other cylinder is the earlier version from MSS.

Those screws provided with the RWM reverser are too long (a problem that I thought has been passed on to Roy previously). On the RWM models they have thicker chassis side frames, and the cylinder back plates are also thicker. So you need to mount the RWM reverser either with the original Mamod/MSS screws, or shorten the supplied screws so that you are compressing the gasket between the cylinder back plate and the chassis side frames (in your photo above I can clearly see a gap between the screw head & the cylinder back plate). As you are operating at the higher pressures you should really seal the reverser to the chassis side frames. Some Mamodificationists use a high temp sealant there but I (& Roy Wood) mount it using a thin temperature & oil resistant paper gasket.

You can now check the thread on the cylinder pivot bolt which should be clockwise. With a bit of luck & perseverance you should be able to remount the cylinder in situ. Push the piston rod fully in, with a screwdriver or similar push the pivot bolt head against the spring so it sticks out as far as it will go. Hold the cylinder over the pivot bolt with the piston end as far up against the smoke box casting as it will go. Whilst holding the pivot bolt so it will not turn, turn the cylinder assembly clockwise as far as it will travel to engage the pivot bolt thread. If that does not happen after a couple of goes, rotate the pivot bolt through 90 degrees and try again. Once that thread has engaged you should be able to tighten up the cylinder pivot bolt.

If you are unsuccessful engaging the pivot bolt in situ, then you will need to remove the cylinder back plate from the chassis but care is needed here so that the back plate gasket is not damaged, and getting the nut back on the cylinder upper rear mounting screw can be another awkward process.

Chris Cairns

Joe · Post by **Joe** » Mon Mar 23, 2015 6:52 pm

ah that explains it! i was wondering what those bits of paper were-good job i kept them. I will follow your instructions, thank you very much

Joe · Post by **Joe** » Mon Mar 30, 2015 11:13 am

any tips on wedging the gasket in? It seems to come loose just as ive almost got the reverser block in.
cheers
Joe

Chris Cairns · Post by **Chris Cairns** » Wed Apr 01, 2015 5:03 pm

Hi Joe,

You need to prise apart the chassis side frames at the front (have you fully removed the screws that hold the chassis side frames to the smoke box casting?). A little soaking in oil may help with the gasket, place the first gasket then mount one side of the reverser valve first - if you can at least get one screw through the gasket and into the reverser valve it should be easy enough to nudge the gasket into the right place for the 2nd screw using a slot screwdriver.

The other side will be a little more tricky but again if you can get one screw through the gasket and into the reverser valve you should be able to slide the gasket into place OK for the 2nd screw.

Be careful screwing up those 2 screws going into the smoke box casting - it is mazak (zinc diecast) so do not overtighten those screws or you will strip the threads in the casting.

Chris Cairns

Joe · Post by **Joe** » Thu Apr 02, 2015 6:55 pm

Well im glad to say the saga has finally ended and there is no more steam leaking- just needs a little more tightening up and oiling and then should be good to go for a good running session on sunday, i will upload a test vid of it running later. Thankyou every one for your advice (and patience) lol
cheers
Joe

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Steam leak from reverser block

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