Wednesday, December 21, 2011

Compensating an 0-8-0 chassis

0-8-0 Chassis

The Super D box of bits contains really lovely item - the chassis. It's scratchbuilt and fully compensated. I post a picture, not because I want to claim any input (It was built when I got it) but for those who fancy doing the same thing and want to know which wheels should move up and down.

Now I've actually seen the beast, it's simple. The front pair use a normal compensation beam. A fixed third axle is then followed by one able to tilt. The pivot is cleverly a bolt so the ride height can be adjusted.

On a 7mm scale loco, this is a serious level of sophistication. Most people just fill the boiler with lead and let the weight bend the world, or at least the layout, around the loco. Some may whinge about the lack of inside cylinders but then they probably don't build their own toy trains. This thing might be lacking in this department but, by golly, it will be able to pull the side off a house.


Iain Robinson said...

Looking forward very much to seeing this job progress through Parker Engineering, as and when time permits! The chassis looks very sweet; I'm getting a hankering to build a loco myself after seeing this.

James said...

The chassis isn't actually fully compensated - the third axle is fixed which means that not all wheels will be in contact with the track at all times. So as a guide for compnesating a similar eight coupled chassis it really shouldn't be followed. It will run better than a fully rigid chassis, but for just a little extra effort with a pair of beams for the trailing pair of axles, the results will be even better.

Phil Parker said...

I knew I should have kept my mouth shut - compensation is a semi-religious subject !

Most flexi-chassis have a fixed axle for the drive. Getting beams on to the trailing axles is thus impeded on this chassis by the need to hang a gearbox on the third one. I know you can do some stuff with beams either side but then it gets fiddly. Too fiddly for me anyway, which is why I hate making the things !

James said...

It's not so much that it's a semi-religious subject! It's surprisingly simple when you see the fundamentals. In the main, three fix points around which everything else moves s key. The 0-8-0 chassis here has four fixed points so will never be quite as good as the full system. It will have some advantages over a rigid chasis when it comes to pick up though.

In P4, there's plenty of room for twin beam layou - similarly in EM by choosing an appropriate gearbox it's not too bad either.

You can compensate any wheel arrangement but after a while it becomes a bit, well, silly. Imagine a 2-10-4 with full compensation? Terrible really! For larger locos springing offers far more conveinience really instead of multiple beams.

Then again, in any 00 locos I've built, aside from 0-4-0s, they've been rigid and have as much lead stuffed in them as humanly possible!