Stripped threads on crankarm

Wife was cycling on the trainer and the pedal fell out. Had a look and the threads on the left crank are completely stripped. Anyone know how it could happen?

Second - what crank would I need for a BB-68 external threaded. Easy to change? Could possible just change the left side if they were similar.

That’s fully repairable, a good bike shop will drill out the old thread and insert a helicoil, which will be stronger than the original thread

You stripped the thread as the pedal came slightly loose, the small repetitive movement was enough to strip thread

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If its not the drive-chain side, I’be tempted to Ebay and a single crank purchase. Got to be cheaper than a helicoil insert ? £10 or so ?

Found loads of non drive side square taper, this is one of the hollow cranks which I was struggling with. It’s a 170mm apparently of anyone can point me in the right direction.

So what model crank is it, and what’s the axle interface? Is it the old Hollowtech? Can’t tell from the pics.

All these crank/BB standards now is a PITA; so much for standardising the industry.

It’s an Evans Chinese special. According to their spec sheet it’s;
Bottom Bracket Prowheel BB-68 external threaded
Chain set Prowheel Ounce 721, 50-34T, S/M - 165mm, T - 170mm

It says 170 on the arm so assuming she got the longer version. (won’t let me add a link to the post)

Went to Evans this morning who said they don’t sell them separately and another shop said no chance on a re-tap. No-one around here seems to do helicoils. There’s a metal machine shop near me, will ask them if they can make an insert. Otherwise it’s going to be a whole new crankset.

Hmm, yeah, sounds like a rare bit of kit! You may well find ebay your best bet for a new chainset, you just need something with a 24mm axle (diameter) I presume?