Compensating outside frame locos

[PenrithBeacon]

I've looked through the usual on-line sources without any luck. Can anyone point to an on-line source for advice on how to compensate an outside frame locomotive?

 

MTIA

 

Regards

[Adam]

As Simon said, it's easiest to build them with a functional inside frame chassis and have the outer frames purely as 'decoration'. I have a forthcoming project that will use cosmetic outside frames, but have done this before for a Sentinel 0-4-0 diesel hydraulic (a Judith Edge kit). It's probably a moot point as to whether dummy axleboxes are really necessary - at least in 4mm - as the cranks do a fine job of hiding them on most prototypes.

 

Adam

[JeffB]

I posted these photos to another thread last week... They show a functional outside framed 0-6-0 that is rigid beam compensated. The gauge is 9mm (HOn30), wheelbase is 21mm (6'/72" in HO). The hornblocks slide in slots in the outside frame. They are made up from a bronze bushing, with a steel part soldered to it to provide more bearing surface and to prevent the bushing from rotating about the axle. The gearbox will float on the outer axle, with the torque arm engaging the cross bar (steel wire) between the frames.

 

There's a beam that engages two of the axles (one beam to each side), and the last axle can pivot vertically about the center pivot you see in the photos. The rods are jointed, not prototypically, but a functional joint.

 

The system works well... I used to use cosmetic outside frames, but have found that functional ones are a lot better. They are more forgiving of small amounts of slop in the fit of the parts, and are much more stable dynamically (in motion).

 

 

 

Jeff

[Adam]

Proper engineering (and of course, most narrow gauge engines with outside frames really did have outside, rather than double, frames). Very impressive Jeff.

 

Adam

[JeffB]

Proper engineering (and of course, most narrow gauge engines with outside frames really did have outside, rather than double, frames). Very impressive Jeff.

 

Adam

 

Thanks Adam... Here's a few more photos. One shows the chassis above with a footplate, motor/flywheel and gearbox (no gears yet). The motor in this photo is a Mashima 1220 with a 12mm OD x 7mm thick flywheel. The next two are of a similar chassis, but with a longer wheelbase. It shows the gearbox with torque arm attachment to the frame. This is an older chassis design. I've since removed the inner frame around the pivoting axle. Both gearboxes are 50:1, which is a good ratio for slow speed running, without being ridiculously slow at the mid-range.

 

 

 

 

Jeff