Adjusting belt tension?

Dear all

I seem to have the opposite problem to EvilV: I’ve got a Strida 3 and I’m having trouble getting sufficient belt tension - rather than 6.5-8.5kg as specified, I’m doing well if I can get 2kg. I spent a fair bit of time looking into it; the belt tensioner is loose, and can be easily pulled out between finger and thumb - if I understand the tensioning system correctly, that isn’t right, is it? Certainly, when trying to increase the tension (rotating the nut on the tensioner having slackened off the nuts on the BB moulding) nothing is happening.

I’m going to dismantle the entire BB soon and see if I can sort it out. But any comments (even in the line of ‘you’ve got it completely wrong!’) much appreciated.

Cheers

Ben