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1.4 Preparing the valve gear

Instructions [71] to [95], page 11-13 of the instruction manual

As mentioned in the previous page instructions [71] to [95] are to be skipped. The motion rods have to  remain unpainted so they were not fitted until after the painting of the chassis. But that does not mean you cannot do any preparatory work. Generally I think it is a good idea to do the tedious work of preparing the valve gear now. When the time of the assembly comes there is little in the way of a smooth progress.

Preparing the valve gear consists of descusping it as much as possible and making is move freely. The actual work on installing it is described in 5.3 Valve Gear


[75] I started with the inconspicuous but mechanically absolutely vital parts: the slide bars. It is the part where the crosshead slides back and forth. This slide must be performed unobstructed and as good as frictionless. If it falters, the uneven running of the locomotive will betray your sloppy work. I am surprised over and over again how all important this slide bars can be. I have learnt it works best to decusp it all around, then sand it with 400 and 1200 grain and finally polish it. In this particular case take great care to keep the open part pointing in the turning direction. Otherwise the fabric of the polish disc will send it flying with all risk of damage and even injury. Always wear safety goggles!!

Working a slide bar, granting you a view on the clutter on my workbench.

The top slide bar is straight from it etch. Note the vertical grooves, caused by the production process of the brass sheet. These groves, especially when vertical, hinder the free movement of the crosshead.

The middle is already sanded and deburred. The grooves lay horizontal with this one because it was orientated differently on the brass sheet

The lowest bar is polished, you can tell by its somewhat curved and glossy edges. Note that the grooves have vanished

[76] The top of the crosshead shows casting marks


File it flat. The crosshead also has a hole in which the slidebar will be inserted. Make sure this hole is free of any obstacles by passing a reamer through it. Very, very lightly. The object not to widen the hole but to smoothen its surface and take away any casting marks.


[78] Instruction 78 is not particularly clear.


" Fold the vertical section of the slidebar over (outwards) and down, ie through 180 degrees"

Errrm..... what? This is such a rare manoeuvre that I simply wanted to be dead sure before doing that. You know, there's no way back if you're wrong. There's also another mystery remark in [75]:


"Note that the slidebars are left and right handed - the "dimple" which allows the vertical section to fold down goes to the inside of the chassis".


OK, now what? What goes to the inside if you fold something down? Nothing but puzzles.

So I studied photos on the internet to find out what the desired result should look like. I found that the upwards pointing really needs to be folded over by 180 degrees to close the slide bar. As pictures tell more than a thousand words I have three photos below to enlighten the procedure.

Upper photo. Put the the slidebar with the crosshead in it in the vise. Note the mentioned "dimple" just peeking over the vise's surface (arrow).


The manual's advice to include the crosshead seems very much superfluous, but remember, when you're hard at work and concentrating on the slidebar. A small slip of the mind is close at hand. I know myself: I would not be surprised to be staring a beautifully folded, soldered and consequently forever closed slide bar, the pride of any modeller, to realise only just then that I forgot the crosshead. @#$%^&*.

Middle photo: fold the vertical part away from the dimple.


This is against the modeller's nature: etches slots should always fold inwards, but a fold of 180 degrees can only be performed "the wrong way"


Photo three: Take the slidebar out of the vise, take it in a pair of pliers and fold it all the way through.


Make sure you do not distort the slidebar, use the pliers to take up any force exerted on the vertical part.
Also make sure you fold it at a true angle.


Finally close the fold completely with a delicate but resolute pinch of the pliers. Then close the slidebar with gentle touch of the soldering iron on both ends.

As an anecdote: when searching on the internet for the answers I needed on this subject I found various DJH built AD60s with the vertical part standing proud pointing to the sky. So I was certainly not the only modeller struggling with DJH's text!!

Good, that said (and done) I had four sets of shiny slidebars & crosshead assies.

Next job was on the connecting rods (216).

[79] Descusping, deburring and smoothing is once more due. Laborious but rewarding as you can tell by the difference between a rod straight from the etch (upper) and a ready rod (lower).

I just can't stop staring at the sheer beauty of a bunch of such rods. Although the manual mentions "two pair" I could find no indication whether a rod was left or right handed.

The connecting rods after adding the big ends's roller bearing.

[80] Note that the dimples are actually representation of nuts which should point outwards instead of inwards. A friend of mine suggested drilling the roller bearings and adding tiny pieces of brass wire. It is possible but I decided that this procedure would take too much time, 10 pieces of wire in every bearing. No thanks!


Also note that the bearing is a little far forward. On prototype photos I found them dead centred on the oval big end. Nevertheless I correctly lined up the corresponding holes of the big end and the bearing. The only way to go was moving the hole in the connecting rod a little backwards, effectively lengthening the connecting rod. This was a no go for me. I am simply not sure if that will interfere with the good working of the piston in the cylinder. So I decided to leave things as they were.

[81] The way DJH designs its valve gear creates a lot of play in the various parts. Every bolted joint is made of three separately moving parts: two rods and a fastener, made from a bolt and a nut. That is too much. You can reduce the sloppiness of bolted connections a little by soldering the bolt head to the back of the connecting rod's small end. This way there is less movement. As a bonus it will be easier to assemble the rod as you have eliminated the chance of the bolt going astray during assembly.

Soldering must be done with a minimum amount of solder. People tend to pickup solder with the soldering iron and then apply it to the work piece at hand. If its not critical I have no problem with that.

It certainly fast is but it is not good practise. If you want to have control over the quantity of solder just cut the bit you need and apply it to your work piece. Then heat the workpiece and the solder will flow into place. You have two advantages:

  • you will spend very little or no time at all cleaning
  • and in this particular case the solder will not foul the bolt's thread.


Take a good look at the bolts in the connecting rods. You'll hardly see solder (click image to see a detail view). And yet the faces of the connecting rod's small ends have not been cleaned yet (there was no cleaning ;-). The perfectionist in me says that the second from left had just a bit too much of solder: it crept up a little against the bolt thread.


The crosshead is cast with a round hole to be taken up on the slidebar. This means the crosshead itself will show no sign of stability. In plain words: it will wobble like a camel's back. Mechanically there is no need to do anything about that. Your loco will run smoothly. But as a depiction of reality it looks odd if it wobbles. More: it is downright ugly!!

The only means to provide stability is through the connecting rod. That is another reason why I soldered the bolt to the back of the connecting rod's small end. Luckily the crosshead's corresponding hole is a little undersized. Ream it ever so carefully to take up the bolt just rotating freely without sideward play. If you can achieve this the crosshead cannot move laterally in relation to the connecting rod. The connecting rod itself will be stabilized by a good tight but free moving assembly on the crankpin. We'll come to that later.

Two left handed and two right handed sets of valve gear.

A lot of time has passed but careful, clean work will make your model run well. I skipped [82-83] until after painting.

[84-86] Offering up the valve gear to the cylinder is the next job. No we are not going to solder the thing in place. It is just for testing purposes

  • to see if it fits and what needs to be altered make it fit;
  • to figure out the easiest way to mount these unmanageable tangling assemblies

The motto is again: anything you can do now must be done. Once parts have been painted rework is harder and everything you have accomplished now speeds up the assembly process later.

At first it seems impossible to insert all three parts into their respective holes and hold the assembly in place all at the same time but after some practise I found a pretty simple way. Just follow the photos for the procedure.


Fit the valve piston in the highest of the three holes in the cylinder backside. Next, temporarily attach the rear of no 215 to the valve gear bracket with a piece of wire (arrow at the far right of the photo).

By now you have already disposed of two sources of trouble.

Move the crosshead in its most forward position and tilt the slidebar so you can insert the piston into the lower cylinder hole.


One more down, one to go.


Now offer the slidebar up to the middle hole taking care that the connecting rod falls behind the vertical part of the slidebar.

Clamp the vertical part of the slidebar on self-closing tweezers and fix the tweezers so you have two hands free. Carefully adjust the slidebar until it sits true in all directions. Put a tiny bit of 140C solder on the upper horizontal bar of the slide bar were it touches the valve gear motion bracket and touch with the soldering iron.


The whole contraption to keep things in place




I quickly put two axles on to see if the movement was smooth

It was!!

For display and pride's sake I also put on the other axles.

They could not rotate fully as the crank pins have not been shortened yet. But that will have to wait. Content whit this test I unsoldered the slidebar and removed the valve gear and stored it valve gear assembly after the chassis had been painted.


[90-95, more or less] I worked the remaining parts of the valve gears.

  • deburring
  • polishing if needed
  • making the joints revolve freely. DJH does sloppy work in this respect.

I stored the resulting parts in a box for now. Assembly will only be done after painting.

I have done as much as I can before painting the frame and final assembly of the chassis.

It is now time to start the real fun part: construction of the various assemblies of the superstructure