I built one in P4 and used a mix of compensation and springs. The front truck and centre driving axle are both sprung using coil springs. The first and second drivers have a singe, central beam and the rear two drivers have twin beams. Track holding is superb and the ride very smooth and steady, having no fixed axle. The only thing I would change is to limit the downward movement of the sprung centre axle so it cannot drop below rail head. I have experienced odd occasions when the flangeless wheels have dropped off the rail on too sharp a curve and dropped down, jamming the whole thing up! 

I drove the 4th axle with a High Level gearbox, motor vertical in the firebox.

The frames and coupling rods were from Alan Gibson - correct wheel spacing - the rods having joints at all the intermediate wheels. Because of the deeper flanges in EM, I think you need to stick to the Comet bits, which have a stretched wheel base so the flanges don't overlap. If you purchase and extra valve gear set, you can modify the coupling rods to give the required articulation for a fully compensated chassis.

Good luck with it.

Dave.

Thanks Dave. An interesting solution! I hadn't thought about wheel spacing. A bit more drawing board work required. What wheels did

you use?

Gibson wheels. Apparently, they have too small a crank throw for the 9F, being based on the Class 2 wheel but I lived with that. I don't think there's currently a better wheel available (don't know anything about Markits). Barrow Road, of this site, has had some P4 wheels made by machining the Bachmann wheel centres and fitting new tyres. Only viable if you have the requisite tools and skill.

Dave.

Bill Bedford also does a 9f etch for the coupling rods (available from Eileens). They are correctly sized and allow for articulation. Bill also uses a novel way of lining the 3 layers up for soldering. But and a big but - no instructions. But once you give some thought to the build it should be obvious which way to go.

Another alternative is to see if Dave Bradwell will sell an etch for coupling and valve gear from his excellent 9f chassis kit.

https://traders.scalefour.org/DaveBradwell/

Were it my choice, I'd go Bradwell for the chassis kit. Expensive? More than other chassis kits but then there is a lot in the kit and its very high quality. I have one in my to do pile. I have failed on 2 other occasions with a 9f build but I used the Perserverance chassis - que wild laughter from certain qtrs - any way good luck.

Mike

Were it my choice, I'd go Bradwell for the chassis kit.

 

 

I agree. Dave's chassis is a thing of beauty. I also have one in my "to do" store.

Dave.

Had another thought.

Following on from Dave's comment regarding the centre wheels dropping and jamming on curves, is this perhaps why Comet don't allow for articulating the centre axle in order to support it? Would that work?

Incidentally it is my intention to make my own frames from sheet as I have done on past projects.

I'm intending to fit it to a much modified Airfix/Dapol kit body.

(More hollow laughter perhaps - have I just blown my credibility?)

The Dapol body will adorn my 9f, it's been built for more years than I care to remember. I used the Comet upgrade kit for all the castings infront of the cab and added copper wire for the pipe work. There are a lot of really good ref books not to make mistakes with the pipework. The smoke deflectors came from the Jackson range - doubt if these are still available but ebay is a good starting point.

I also have to admit to holding a DJH 9f kit, which will probably never see completion!

As to the wheels..why not give Colin Seymour a ring and see if he'll skim the centre wheels for you? You will have to pay I'd have thought, but unless you know someone competent with a lathe there isn't much of a choice.

Just remember that the front drivers cannot have any significant side play at all and the rear driver must have side play. Unless your planning on scale curves...

Mike

Thanks Mike.

I was once buying parts for a fowler 2-6-4 from The Comet stand at an EM Expo and remarked that I may never get around to completing it.

He said "Look around. All these businesses exist by selling stuff people will never get around to completing!"

I do use a Mk1 Unimat so could do the skimming but thanks for the tip re sideplay.