Sunday, January 21, 2007

Wheels


















What I started with was a set of frames with hornblocks fitted, and wheels turned. So I'm afraid I've no construction details for these.

Except for quartering the wheels.

You can do this either with a jig,or in the lathe. I've used both methods - a jig works well. Most books and drawings show jigs which are specific to one model, which is not brilliant. Since then, I have seen a general one detailed, which is a far beter idea. I've also quartered wheels in the lathe, which is what I chose to do this time. Two sets of wheels were already assembled and quartered, but, when I checked them, both were different !

The object is to set the two wheels on an axle at 90 Deg to each other -usually, the right leads on British locos.

Having said that, the really critical thing about quatering is not the exact angle, but is that all the wheelsets on the loco must be set at EXACTLY the same angle. This is because the wheel relationships are locked by the coupling rods, and any differences in angles will result in tight spots as the wheels rotate.


Also, for the same reason, all crankpins must be drilled at the same radius and perpendicular to the wheel - a simple jig does the job - and the coupling rod centres will be exact.



The photos show the method I used to set the wheel quartering on the lathe.
I first put a round bar between centres, and a parallel (a piece of tool steel) across the lathe bed. Also, I clamped a square to the cross-slide table. I was then able to establish the position of my references relative to the lathe centre.
I set one wheel with its crankpin vertical; I clamped a square to the cross-slide table and offset it from the lathe centreline by the radius of the crankpin.
I set the other wheel with its crankpin horizontal - for this, I built up a set of blocks to centre height minus crankpin radius. One wheel was pressed onto the axle before I started, and the other was locktite'd, once set up.

Saturday, January 20, 2007

Welcome to my blog

One of my serious interests is model engineering. I've built steam locomotives in 5 inch gauge, and also in gauge 1. Interest in the hobby seems to have grown quite a lot in the last few years - certainly my local model engineering society is a lot busier. Several people I've spoken to have expressed an interest in building a loco. These days, sadly, most of the college based courses are no longer running making it harder to start from scratch.

I have just started building a 3 1/2 inch gauge loco and thought I would keep a journal of my progress. I thought if I set up a blog perhaps it might help someone else to get going. I will share some notes and photographs documenting my progress. Hopefully my blog will promote discussion with like minded people.


The loco I am building is a GWR Hall (3 1/2" gauge).
Its an LBSC design: the construction looks typical of lots of locos, so the construction notes should transfer to other locos.

Truth to tell, I bought it at a club auction, as a set of frames with the wheels already machined. There were a few other components which had been made up, but, sadly, they were rusted beyond hope. The drawings are original blueprints, and pretty fragile. I think they would disintegrate if used very much. I tried photographing them - this was surprisingliy good, especially when converted to black and white and invertes. In the end, I scanned the drawings in sections, and worked from both. So there will be no notes for the loco frames or wheels.