What ist?

He says they're twisted because it works at 90 degrees, connected to the bevelled gearbox, or something. Or maybe a spiral bevel gear, he's just said (he's been googling all evening, liking an engineering conundrum).

Likewise PP! Just it bugs the excrement out of me when I can't find anything similar.I understand the principle of a crown wheel, pinion and planet gears but can't figure how this would equate?

Where's Fred Dibner when you need him?

I'm glad someone understands 

And as for Fred Dibner, felling chimneys in the sky!!

I read Freds lifestory book. He was also an innovative engineer building his own winding gear and pit shaft in his back garden and restoring and running Steam Traction Engines.  One of life's characters!