Haven't been here for a while. Work and life getting in the way and all. Here's another new project, and quite a big one by my standards. An 8F in S7 from the MOK etched kit. I won't do a step by step account, there are a few excellent blogs out there already. I'll just post a few pics now and again and explain some of the things I encounter and choose to do differently.

The first model railway locomotive I ever had was a Dublo 8F. The first serious railway book I ever owned was London Midland Steam in the North West by Bradford Barton, with some splendid photos of 8Fs. Some of my favourite Colin Gifford photos feature 8s. I have a soft spot for 8Fs.

In spite of modelling in 4mm for many years I've somehow managed to not build an 8F. Having recently taken an interest in 7mm S7 and built a wagon or two I thought I ought to build a loco. I came across the MOK 8F, so why not? I've been stuffing notes into the piggy bank for a year or so and now I have the kit, a motor and gearbox and the wheels. No excuse not to get on with it now.

The wheels are the Slaters set in S7 from the Scaleseven Society, complete with crankpin set. These wheels differ from the usual Slaters offering by having steel threaded inserts for the crankpins. Seems like good engineering.

I thought I'd start by getting the wheels set up before I get on with the chassis. Blimey! Disappointment on day one! The wheels don't run true. I checked them all and some are better and some worse but none of them run true. They all have some lateral wobble and some have a bit of eccentricity. I don't think it's a case of sending them back because I think it's a limitation of the manufacturing process and the design. Having had a bit to do with injection moulding design I'm expecting that the relationship between rim and axle insert depends on accuracy of tooling and the cooling distortion of the plastic when it is free of the moulding tool. I have an old set of Slaters driving wheels from an aborted 0 Gauge 9F project from years ago. I checked them and they're just the same. I also have a set of AGH wheels from the same project and they run true (to eye at least), so it is possible. Looking closely at the Slaters design I guess they've decided to make quartering easy and compromised the fundamental ability to run true. There really isn't very much to locate the wheel perpendicular to the axle. Just a tiny land outside of the quartering square. I doubt that many Slaters driving wheels run true for these reasons. If I'm wrong then do let me know.

What to do? The wheels look good cosmetically, and I don't know where else I can get a set of 8F wheels in S7 that look the part. I've read online that flattening the back of the wheels on a surface plate with wet and dry will put the back of the rims and the back of the axle insert on the same plane and reduce the run out. I've tried that and it does help a little on some wheels, but not enough and not on all wheels. Two options occur to me: tweak the wheels by hand to reduce the run out by essentially distorting them back to where they should be, or boring the wheel centres through 3/16"and using a telescopic axle. If anybody has any experience of either of these remedies then please leave a comment. Thanks.

i think this project is going to take a while...