I have a two piece tailshaft (well it is now) very similar to yours,it also came out on dyno.
It was orignally a EA FORD falcon shaft that i fitted a toyota yoke to,the shaft wasn't balanced. We had already done about 5 dyno runs in 3rd gear and was doing a run in overdrive and she went bang!
I recken my tailshaft broke in the middle first as this is where all the damage to my floorpan was,my guess is the same thing happened to yours going by the photos.
Even half a tailshaft banging around is enough to break your gearbox.
i had a splined slip thing on mine so when it let go at the back or in the middle it slipped off and had this short heavy bit flapping around that left some nasty damage on the floor pan and would have easerly snapped the bellhousing and output shaft.
You can't be planning on running an unbalanced shaft again soon. they will break in the middle if out of balance.
glad i am not the only one.
Even with a balanced shaft it's in the back of my mind every time i do a burnout or put my car on a dyno ,that the shaft may break again.
How did you go repairing the floor pan of your car?
I was lucky that mine broke in a old car dedicated for burnout's.
With a hammer and the state of mind that it was not my car. Then a welder and a few patches.
i bought a tail shaft hoop but it is not easy to fit so i put it in the to do list. but i know how you fee when punishing the car it is in the back of my mind. and the diff mount also broke once so it has a history. i don't trust it but i mis treat it all the same.
Have you dynoed your car since? if so what HP did you get?
Which engine & box are you using & what sort of car have put it in?
Lots of question's
I found it easier to make my own tailshaft hoop,the hoop i made is at the gearbox end of the shaft, so it still won't help if the same thing happen's again,have looked at making a hoop for the middle & rear as well,told you i am paranoid
tailshaft failures, maybe a new title on main menu soon
just reading bits here and there and came accross this thead, i spoke to my tailshaft bloke and he says that my tailshaft being a mile long and not big in diameter could have got what he calls "whip" where the shaft gets a bit of a bow happening, which could explain my failure as i was on a slightly bumpy road when mine let go, see pics of mine by clicking lingk below.
hows things going these days?