The discussion on shear pins brings back memories.
Late 70's bombing comp at Lossie. Laarbruch's folding wing bombers operating out of the navy hangar where the exit is immediately up an incline. At the hangar door threshold is a drainage channel where the grating is not level with either the hangar floor or the sloping taxiway. The navy have given us a tractor. Not your usual RAF line type but a Massey Ferguson original, probably made even before M & F actually met each other. The trick was to get enough speed on the tractor/Bucc combo to get up the slope but not so much as you jumped the nosewheel on the threshold.
One morning when I thought I'd really got the hang of it, first two aircraft out and two shearpins worked exactly as advertised. Navy chief takes pity and says "you'll never do it with one of those (insert derogatory adjective here) RAF towbars, use one of ours".
The navy towbar was exactly the same as ours, at the nosewheel end. Tractor end was different. Bolted welded and very, very solid. Given what had just happened I said I couldn't use that as the weak link was now the nose leg. Chiefy reminds me Blackburn milled their aircraft out of solid and pilots have been landing them on pitching carriers for years " so you aren't going to break it". And do you know what, he was right. Mind you for the rest of the det it was the most controlled and considered movement of aircraft I've ever done.
Lightning tales later.