OK!! Another installment in the long saga of "Phil builds a couple of garratts"! In this case, the section should be entitled "Fixing one's previous mistakes!" . All of which were of my own making. I think that when Phil Parker built one of his models of this loco, he remarked somewhere that one should fix problems when they occur, as they WILL come back to bite you later and fixing them can be tricky. I should have listened........
There are two issues here, and they are different for each loco that I'm building. But they both relate to what I believe are the circular mudhole covers on the shoulder of the firebox. Lets take each loco in turn to illustrate the problems and how they were fixed.
For the model that I'm building for myself, the problem was with the whitemetal castings that were supplied and which i had previously affixed to the firebox. My model will represent the final loco of the quartet of BP Vivian style garrats, William Francis of Baddesley colliery. These castings had previously been fitted to the firebox and are see in the following photo's.
Note that these covers are assymetrically located on the firebox, as are the washout plugs.
The castings are nice, but when compared with the real thing, as shown in Phil parkers pictures of the real loco, they appear to be of too small a diameter and also too deep. Please see the following link : (Picture copyright Phil Parker)
A slight difference I think you'll agree.
So what to do? The castings had always bugged me from the moment that I'd fitted them. I could have ignored it, but it was going to bug me forever if I didn't do something about it. In the end, I had a go at making replacements and I think they came out rather well.
From the photo's I guestimated that the size of the real cover approximatd to 1/4" in diameter in 7mm scale. So I obtained some 1/4" brass rod and popped it in to the (new) mill. The radius of the firebox shoulder was approximated at 5/16" diameter following some test cuts, and so after centering the rod to the mill, a 5/16" diameter radius was milled into the end of the rod.
Picture below shows the rod held in he chuck after centering and with a light test cut to confirm centering of the rod. And yes, for the engineering specialists, I know that I should have held the brass rod with softjaws, but I don't have any at the moment. Still kitting out the new mill at the moment.
Looking good, so on with the milling.
Which gives this - a 5/16" radius milled into the end of the rod which will match the curvature of the firebox shoulder.
With a nice radius milled centrally into the rod, it was over to the lathe to tidy up the edges.
The end was parted off at a suitable depth to yield the rough finished item. Both covers are seen in the photo below, showing both the top and uderside of the parts.
As expected, the upperside looks a little rough, due to the parting off from the brass stock. The photo makes the series of cocentric markings look worse than they are in actuality, but they will be dealt with. The central spigot remaining from the parting operation will eventually be cut back to mimic the central cover retaining bolt.
So back to the lathe the parts go. In this case, I made a mandrel from 1/4" ID aluminium tube to hold the newly made brass covers for the lathe operations. The aluminium tube was slit with a piercing saw on approximately 120 degree angles and thus could be clamped down onto the brass parts. This allows the brass parts to be held securely in the lathe chuck without a risk of them being marked by the chuck jaws. Hopefully the pictures will show what I mean. The newly made brass covers were carefully inserted into the mandrel and clocked to check that the front face was at 90 degrees to the axis of the lathe. It was then a simple job to face the outer surface of the brass parts to give a nice smooth face.
A finished part is shown below together with its couterpart awaiting final finishing. I think you'll agree it was worth the extra effort to do the final surfacing.
The newly made parts are the compared with the whitemetal castings as currently fitted to the loco.
Hopefully you'll agree that the new parts are much more representative of the real things on the actual loco.
So then it was a case of unsoldering the existing whitemetal fittings and repalcing them with the newly made brass replacements. Some careful alignment was used to ensure that the parts were in the correct place, as the new parts had no location spigot. I could have added one, but I wasn't convinced that the alignment holes in the firebox shoulder were correctly situated, so careful measurement and alignment was used instead. The new brass parts were sweated into place using 100 degree solder and the RSU.
The following photos show the previous whitemetal casting and the newly made brass substitutes as fitted to the left hand side of the firebox.
Hopefully you'll agree that this is a significant improvement and worth the time and effort to do.
For the other model, which is to represent the Sneyd Colliery loco, the problem was rather different. In this case, photo's show that this loco was not equipped with these large mudhole covers. Unfortunately, when I originally made the replacement outer firebox wrappers, i didn't notice this on the photo's of this loco and so merrily drilled the hole of the locating spigot in the new wrapper and eventually fitted the cast white metal mudhole covers. And then I saw a nice enlarged photo of this loco in service that clearly showed no mudhole covers. Checking through my photo's of this loco confirmed that.
" Oh bother!!" said I. Actually I said something different, but it was still 6 letters, started with the letter B and ended with the letter R.
Again, what to do? As I keep telling my students, it is important to do one's research properly before starting work, otherwise fixing a mistake is going to be far more embarrasing and time consuming. I must listen to my own advice.
I thought long and hard about how to fix this issue, as there was a strong chance that I could make things sigificantly worse in trying to rectify the problem. Do I ignore it? Do I own up to the customer as to my stupidity? Do I need to remove the boiler and make new wrapper (again!).
After thinking about it for a few weeks, I convinced myself that I could remove the white metal casting, plug the resultant hole with some brass rod and sand down the excess rod flush and smooth with the surface of the wrapper. And in fact that is what I did. But before trying it on the actual model, I remembered that I had some spare firebox wrappers from when I was making the replacements for the incorrect orignals as supplid in the kits. So I experimented with one of these first, which convinced me that I could achieve a good final result.
Photo showing result of test plugging the hole in the spare wrapper from the front.
The excess rod is visible inside the forebox, but has been cut off and sanded down on the exterior side so that it is flush wiith the surface and so virtually invisble. The fingernail test shows no perceptable surface roughness.
And from the side - can you see the rod plugging the hole?
Looks OK to me.
So, on a wet and windy day last weekend with no demands on my time and more importantly, no distractions, I plucked up my courage and set to with plugging the hole.
So here is the casting in place to start with.
With the casting removed., the hole was enlarged slightly to accept a piece of 3/32" brass rod. The edges of the hole were chamferred slightly to allow for the solder to penetrate, and then both the edges of the hole and the brass rod were then liberaly tinned with solder.
The steel screws are there to prevent the inner washout plug fittings from desoldering during the various heating and soldering operations that are in close proximity to them.
With a liberal application of flux, the rod was inserted in the hole. At this point it won't slide in. However, heating the rod (not the wrapper) with my 100W iron allowed the solder to melt and thus the rod could be inserted. Working the rod back and forth slightly whilst the solder is molten ensures that both the inner and outer surfaces of the rod / wrapper join are well coated with solder to ensure a good joint. The joint was then allows to cool, leaving the rod firmly soldered into the firebox wrapper, as shown below.
The excess rod was cut off close to the wrapper using a fine piercing saw and then over the course of a couple of hours carefully filed and sanded back flush with the existing wrapper to eventiually make an invisible joint. This yields the final result below.
(The grey circle is the solder ring where it penetrates the joint between the wrapper and the rod / plug - the surface is indeed flush nd no imperfection can be felt using the fingernail test).
And on the other side....
Much less visible here.
All in all, a worthwhile task, abeilt a bit nerve wracking. If only I'd looked at the photo's properly when making the new wrappers, I wouldn't have had to do any of this. Oh well........
I have since given both loco''s a good scrub abd brush up to remove much of the tarnishing.
I'm just making up the displacement lubricator that is attached to the cradle above the reverser, and then the boiler unit then will be prepared for painting. However, the making of the lubricator will be for another segment.