Tag Archives: engine

ValveGear getting close

Close but no coconut

I have been working on the valve gear completing the expansion links and die blocks. The link slots are longer than designed (due to iffy dimensioning on the drawings), so I made the die blocks longer to match, so I think all should be OK.

Colin Sims and I have been debating if the eccentric rods are too long, and having now assembled the LP Valve gear I can confirm they are!! I have ad to shorten the clevis (?) at the bottom of the valve rod, and also shorten the valve rod to get everything to fit – not a complete disaster, but it seemed to be about 3/8″ long over all…

Worried about LP Valve too

Having now assembled the LP gear I could not resist applying some compressed air to see what happened – and what happened? The valve leaked (a lot). Inspection revealed that the eccentrics and eccentric rods are too close to the valve chest, and so exert some side pressure on the valve rod, and the design of the “buckle” means that this resulted in the valve being held off it’s seat. I am sure this is all as a result of inaccuracies in my machining, but it’s still a bit of a concern.

A normal slide valve buckle allows the valve to settle smoothly onto the port face, but the circular arrangement in the Leak has the opportunity to hold it at an angle in either the vertical or horizontal plane. Disconnecting the expansion link from the valve rod, resulted in the valve seating, so I think it’s just a matter of providing enough “slop” to prevent the crank endfloat from forcing things out of line…

However, I also found if I upped the pressure the balanced valve started to leak. – It  seemed to be that the part a the valve bearing on the valve chest cover is forced off it’s seat.  (not a good sign). It would appear that there is insufficient surface area on this part of the valve to hold it in contact with the cover, a large change!.. Time will tell…

Some picks of machining the links and assembly…

Advertisements

Making it nice…

As we have stripped down the assembly, it’s time to do some “finishing” prior to a (hopefully) final erection of the major components.

At the SBA social in Hereford in the Autumn John Winn had given a talk on Nickel Plating as a way of reducing the polishing needed to maintain the engine. Given that Befur is destined for Salty Water this seemed like a good plan. I had done plating in the past with complete success, using a Dynic Nickel Plating kit on the loco, so decided to have another go on the bright-work on the engine. However, on the last batch of plating I had contaminated the solution by letting the brass anode hangers get into the bath (even though they were varnished over. So it now produces a rather nasty looking black (but corrosion proof) finish.

Dynic seem not to exist any more, so eBay provided replacement Nickel Salts (Frost Restorations), and the local gardening store provided a nice plastic trough capable of holding the rather larger parts needed on the Leak.

I had not done any plating on steel or cast before, and did not imagine it would hold any problems. The whole game plan is to CLEAN the parts to be plated – any failure here and you WILL get crap results!

You can  use an  Acid Bath to start with, but Dynic provided de-greasing solution that you boil the parts in, and then you scrub and wash them repeatedly using scouring powder – and DO NOT TOUCH the parts once they leave the de-greasing tank.

Well, we followed the previous plan, with mixed results – everything “looked” OK, but after a short time tell-tale rust was showing thru but not on the really polished parts of the components (The parts rust very fast (10 mins) in the open air as they are SO clean).

So some analysis suggested that we had failed to get the grease out of the minute holes in the less polished parts of the components, so back to the start – stop-off the bits that were OK with varnish, re-boil the parts in the de-greaser, re-scrub and re-plate. The results look pretty good to me… See Pictures below>

Connecting Rods, Cleaned waiting under water for the plating Tank

Connecting Rods, Cleaned waiting under water for the plating Tank

Scrubbing after degreasing - each component is scrubbed then washed at least 3 times.

Scrubbing after degreasing – each component is scrubbed then washed at least 3 times.

Like any Chemistry this is messy - CHinese Fishtank Heater, Maplin Constant Current Supply, Bath, anodes and components.

Like any Chemistry this is messy – Chinese Fish-tank Heater, Maplin Constant Current Supply, Bath, anodes and components.

The Engine Columns in the Plating Tank (Nickel Sulphate provides nice colour)

The Engine Columns in the Plating Tank (Nickel Sulphate provides nice colour)

The end result seems quite nice - I stopped off the sliding surfaces on the piston rods - we will see how the plating survives in the stuffing boxes!

The end result seems quite nice – I stopped off the sliding surfaces on the piston rods – we will see how the plating survives in the stuffing boxes!

Work on the engine begins!

Well, we’re off! Spent the day clearing the workshop ready to get started, and trying to decide where to begin. The bed casting had already been mostly machined, so I spent a while measuring it up to check all well. Bruno had mentioned that it was “mostly” OK, a few minutes found that all was well, except that the main bearing housing was 1 3/4 instead of 1 5/8’s..Not catastrophic, but it has implications. The next parts to address are the columns, and there I found my first dimensional error on the drawings (the offest from the cross-head slideways to the front of the foot is shown a 1 5/16 instead of 1 15/16!).

This also points to a need to adjust the column setting jig to accomodate the changed main bearing housing – so the first metal to be cut is the removing a 16th from the face of the jig… so we have certainly begun! 🙂

The Castings Arrive!

Castings for Befur's Engines

Beauty in Cast Iron!

The engine ceases being and “idea” and transforms into a few hundred pounds of cast iron!

As planned Louise and I returned from the sailing course and hot-footed it to Paris to meet up with Bruno Martin-Neuville and his friends from the Amateurs de Bateaux á Vapeur and purchase this beautiful set of castings.

Bruno, Jean-Yves, and John entertained us wonderfully with a tour of their fabulous facilities in Severes on the outskirts of Paris and a very nice lunch. (we forgot to take pictures! but saw Midship, Melusine and others…)

So the winter’s work is now clear – to commence transforming these castings into a working engine – it’s clear that there are some “deamons” lurking in the drawings, so I am pleased to have the help and advice of some of the professionals from my Model Engineering club and the support of previous builders in the SBA