Following on from earlier threads, I have been interested in leak modes in Mark 1 vehicles for considerably more than a decade, and I think I broadly understand the mechanisms.  There is little doubt that Mk1s,albeit derived from my hero OVSB could not have been more badly designed in terms of water proofing if they had tried.

 

Water derives from four main sources

1.  The cantrail joint

2.  Leaky window seals

3.  Condensation

4.  Odd leaks round periscopes and ventilator evaporation trays (and as Darren has noted,at the end of  vehicles behind cast tare and dimension plates, behind RCH lighting control cable outlets, and those bloody OH elecrification signs that some loon determined were to be attached by self-tapping screws)

 

Another important aspect is that heritage railways provide a very different environment from the main line.  On the main line coaches spend a good proportion of their time whizzing around the countryside so that a highly evaporative airstream is generated.  THis is particularly true of the roof vent evaporation tries, which serve to do just that - evaporate.  On heritage railways, they fill up and overflow into the ceiling.  Block them up and problem 3 - condensation rears its ugly head.  In the heritage enviroment coaches spend most of their time static operating only at weekends and at slow speeds, and when static some well-meaning soul will come round and assiduously close all the windows - and problem 3 rears its ugly head again, with damp upholstery and mould

 

The trouble with the Mark 1 framing is that it is festooned with horizontal Z ribs that can entrain water and carry it miles from where it came in!  This is why finding leaks can be so exasperating.

 

The classical hole at the cantrail ends is caused by rain leaking in at the cantrail seal, travelling along to the end, pooling there, and rotting through, but the CAUSE of the leak in this case is NOT corrosion.  Failure in this area allows water to drain down the ends to rot the bases of the crash/buffing and corner pillars

 

Failed window seals give the classical Mk1 rot out pattern, though in this case, vertical pillars at the sides of the windows localise the water.

 

Finally the dreaded six-inch line rot, caused by a combination of window leaks and condensation.

 

Where does it all end?

 

1.  I have already wittered on about curing cantrail leaks in an earlier email (either here or on 61742) , so I see little benefit in repeating myself.  I have discussed this with both Darren and Julian and I think all three of us are broadly in agreement in how the problem should be treated, though there are arguments for re-rivetting or wholesale replacement of rivets by stainless steel nuts and bolts.  As for the hole at the end of the cantrail problem, the Cig has these and I am hoping that with a curly mirror or an endoscope to get a better understanding of the mechanics when I get a mo

 

2.  I think I have determined an effective method of securing window seal leaks using polysulphide sealer and (or Arboseal for window FRAME leaks - frames usually leak due to ali rivet failure).  The technique is quite time consuming to apply and needs careful masking but is effective.  Peter Spokes will confirm ( I hope!) that I have done a number of his windows and they are now watertight.  I must take issue with Darren over the use of Vaseline or other petroleum jellies for window rubbers.  These are paraffin compounds, and whilst temporarily softening natural and nitrile rubbers, will ultimately dissolve them.  They may be better on vinyl or neoprene rubbers, and silicone and Viton rubbers are safe - but these are expensive and way beyond BRs parsimonious thinking - even if such rubbers had existed then.  There may be commercial rubber softeners that claim to be safe,  but I'd be very wary. I cannot believe its too difficult or too expensive simply to go to Baines and ask them for new seal material.  I have simply yards waiting to be fitted to my 117, but I acknowledge that replacing the rubber on a double glazed unit may be more frought.  Incidentally I must confess to having made no progress on finding a factory with large vacuum oven in which to de-steam double-glazed units, despite promising someone - other pressures from PBR I'm afraid.

 

 

Anyway, to my main reason for posting.  Peter Spokes is contemplating some expensive repairs on the Cig.  Although the opportunity has passed by several times in the last month or two, this weekend should see our ace welder go down and look at the problem, to assess whether the work can be done without sending the unit way.    He will do this during his works time, so will want paying .  However if he can properly open up and expose the problems, he WILL be able to do a repair and this MAY generate a VERY much cheaper solution.  He cannot, of course, do anything about upholstery or floor coverings

 

In the absence of any instructions to the contrary I shall ask him to have a look at the Cep.  Shout loudly NOW if you have any objections, although at this stage he will clearly not be 'opening up'

 

Kind regards

John Down

 

 

 

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