Outside framed bogie suspension

[garethashenden]

I'm having trouble working out the ideal way of making a bogie. It's for a North London inside cylinder 4-4-0T, the bogie has a 6' wheelbase. I want to have some form of suspension on the bogie as well as current collection. It seems that functional inside frames may be the way to go but I'm not sure. A further complication is the closeness of the engine frames to the wheels. There are cutouts in the prototype frames the shape of the wheels, but there's not a lot of space for an extra set of frames.
The loco kit (Peter K) has twin beam compensation for the drivers, but the bogie is rigid. It has very flimsy inside frames with no bearing surface other than the etched hole.
Suggestions (and diagrams) appreciated.

[Philip Hall]

I think the simplest solution would be to have a fixed bearing at the front of the bogie, either in bearings or merely holes in the inside frame, and a slot for the rear axle with a beam bearing on the top of the axle.

However, as the wheelbase of the bogie is only 6'0", I think that you might not really need any compensation on the bogie at all. The Finney M7 is arranged on the same principle, twin beams on the drivers and a central pivot for the bogie, and is very steady and powerful even with no compensation on the bogie.

Philip

[Andy W]

Agreed, but you could have one bogie frame fixed rigid to the central spacer, and the other pivoted to provide compensation. Like Philip said though, that might not be necessary.

[Will L]

Like Phil, I'm not convinced that compensation/suspension on loco bogie is really necessary. A way of fitting pick-ups to a bogie is given here, although applied to a sprung inside frame bogie, this approach can be applied just as well to an rigid outside frame bogie. It also has the effect to putting a bit of springing between bogie and bogie.

[garethashenden]

Well that makes things easier. I'll make up an inside frame with proper bearings and go from there.

Tangentially, how should I go about making leaf springs? They're very noticeable on this bogie and there's nothing in the kit.

Here's a larger scale model, I can't find a prototype picture on google