Sign my
GuestBook

LTM 51 in HO

Detailing the boiler

This is going to be a long read as the boiler cradle has many many detail to discuss. But then again I maintain this website

  1. for your enjoyment to read;
  2. for others who want to learn how to build models or maybe even a similar model (which in this case is of a lesser consideration as it is unlikely that someone will ever build another Kaffa with this one exception of Johan who sold me the kit, and he can build without my help because he is a far more experienced builder than I am);
  3. to record what I do so I can use it as a reference for myself (I tend to forget the details after a few years and many techniques are handy to remember).
  4. Thatsaid enjoy it or skip it, whatever you prefer.

 

Detailing is for me "anything beyond the basic structure". So all appliances, piping, handrails etc. There are only a few rules to the order of things

  • The larger fittings come first: chimney, dome, whistles etc. for two reasons
    • the larger components require more heat so it is convenient to have no other parts in the way that may fall off
    • the larger components tend to be the source or the destination of piping.
  • Piping is usually built up from the closest to the boiler towards the outliers.

For the rest there no particular order and and the order in which you work is prone to the whim of the moment.

Preparation of the large boiler appliances

Chimney, safety valves and dome

 

Detailing starts with the chimney. The casting that I have is a NS 3700 chimney from Philotrain. It is 1.2 mm too long for the LTM 51.

The form of a chimney is irregular and vulnerable so simply sticking it in the lathe is out of the question. The only reliable straight surface is the inside hole of the chimney but a look inside revealed that wasn't up to par either.

So I stuck it in the chuck of the lathe protected by a thin sheet of aluminium (from a soda can). I carefully drilled and centered the hole to an acceptable geometry.

I turned a mandrel from steel, originally only on the right hand side. After drilling the chimney as described above this mandrel had become undersize so I turned the left end slightly bigger. This end was glued into the chimney. After the glue had set I stuck the mandrel in the chuck en drilled a 1.6 mm hole from the bottom though the center of the chimney all the way up.

I then parted the chimney base at the lower rim. I filed the chimney base flush with this rim.

I measured its height and calculated how much material I still had to remove from the upper part of the chimney. Just a few tenths of millimeters and these were quickly disposed of on the lathe.

I stuck a M1.6 bolt through the chimney and its base and secured them with a nut.

Then I soldered them together avoiding contamination of the bolt by smearing a bit of grease on the thread. So after soldering I could remove bolt and nut again.

A bit of filing to get it flush on the boiler will do the rest.

Speaking of which, I had two other appliances to fit on the top of the boiler: the dome and the safety valves.

The safety valves I bought where filed down to match the prototype. Easy. The base however took a bit more thinking. Habitually the safety valves were located on top of the firebox and in the Netherlands these were usually Belpaire fireboxes, with a flat top. This flat top was reflected in the casting. The LTM 51 however had a round top firebox. So I had to remove some metal to get it to fit decently on the firebox. After some thinking I took a dive in my old metals and failed parts box and retrieved the number two iteration if my boiler which was rejected because it was undersize. Undersize it still was bit with a piece of emery paper 360 it had just the right diameter. I oiled the paper and rubbed the safety valve carefully until I had a pretty good fit.

The dome received a similar treatment

Steam turret

 

The steam turret on the LTM 51

The steam turret on the AD60

The drawing of the controls in the cab

Now attention turns to the steam turret cover immediately in front of the cab.

The steam turret needs some explanation. Normally every single appliance has a boiler fitting with a shut down valve. Of you have a lot of appliances it can be benificial to group them together in the steam turret. This

  • reduces the number of boiler fittings; which each weaken the boiler structure
  • reduces the number of shut down valves; the whole steam turret only requires one shut down valve. This reduces inital cost and the maintenance costs

A boiler turret is an unusual feature for a Dutch steam locomotive but from the drawing of the boiler backhead (left) I know it there. The close grouping of all the controls betrays it is there. The turrets is covered most likely for aesthetics and ease of cleaning.

The parts provided for in the Kaffa etches consisted of

  • a top and sides sheet which should be bent twice over de the pre-etched recesses
  • a front sheet

As you can see from the ominous photo's above things di not go too well. I decided to solder the parts together with 240C solder so I could solder the whole cover on the boiler top in one piece. So I brought the small flame torch out and more less burnt a hole in the top-and-side sheet. After taking the two apart again and while celaning the front sheet I rubbed too hard on a bit of sandpaper and now both were scrap

I took my loss, sawed and filed a strip of brass and copied the front sheet on another new sheet of brass

By the end of a troublesome evening I had a cover glistening on the boiler, only to come to the realisation it was too big. So out came the calipers and I started comparing.

Dimension Drawing Measured
Length 7.98 mm 7.45 mm
Width 12.05 mm 13.91 mm
Height *) 3.92 mm 4.64 mm

*) Measured from the top of the boiler

The conclusion was inevitable: my first impression was correct. The little overheigt of 0,7 mm could be correct with a bout of filing, but an overwidth of almost 2 mm can not overlooked. But was Kaffa so wrong?

Well no. I made an error during both my attempts. I assumed the top-and-side part had to be wrapped around the front sheet (left diagram) but as it turned out the front sheet had to be placed ahead of the top-and-side part (right). As may be evident from the drawing the arrangement will result in diffrent dimensions

Dimension Drawing Measured As intended
by Kaffa
Length 7.98 mm 7.45 mm 7,62 mm
Width 12.05 mm 13.91 mm 12.75 mm
Height 3.92 mm 4.64 mm 3.91 mm

These sizes are still not correct so on the third attempt I will transfer the correct dimensions on the brass sheet.

Three generations: 1. Busted 2. Too big 3. At last

On the photo it sitsnot entirely well but I will make a few corrections before soldering

I am happy with the dimensions despite the 0.2 mm overwidth

Dimension Drawing Side Measured
Length 7.98 mm

Left

Right

8.03 mm

7.98 mm

Width 12.05 mm

Front

Rear

12.24 mm

12.23 mm

Height 3.92 mm

Middle front

3.89 mm