The cross-beam for a travelling-hoist I am building is a 6-foot gauge 4-wheel bogie, the beam itself a frame built from 4 lengths of angle-steel linked by flat plates and channels.

Recognising it would be very difficult to make angle-iron rails truly level and parallel in a 16 X 6 ft concrete-block shed built to the nearest half-block, I am giving the "bogie" simple horn-blocks with rubber pads. The design is further complicated by limited head-room at one end – and the frame has to hang below the suspension.

Taking all care I drilled all the plates on the milling-machine, the angles against an angle-plate on the bench-drill (space reasons), and the frame came out very satisfactorily.

Fabricated the horns complete with lead-in bevels to aid the upwards assembly necessary…

… Then discovered their screw-holes did not line up with the DRO-set holes waiting in the chassis plates!

Annoyed and disappointed I decided what holes could be enlarged and/or slotted in what bits. There goes their pristine accuracy, and I reflected though this is a purely functional tool, not exhibition entry, I still want to make a decent job of it.

Then it hit me, this morning.

I'd used the wrong ends as data, matching the datum corners marked by drill-dots on the frame-plates, but not right for their own purpose; and I might have escaped by simply inverting them, with new bevels.

Using some very ratty old steel hadn't helped either.

Nothing for it now though, really, but to make new horns, from some metal in good condition, and I cut the blanks this evening.

'

The moral?

Hindsight is a wonderful thing, fore-sight is even better!

(Probably available from stockists of round-tuits and spare moments.)