Linn used a larger thimble type cylinder that went over the existing motor spindle to adapt it to the 45 RPM speed. It had like an O-ring inside that kept it tight against the motor spindle.
Linn LP12 Valhalla 45 rpm
This is the most embarassing question I've ever posed here. I bought a used LP 12 Valhalla many years ago and always assumed that, like my previous LP12, it won't play 45 rpm. But now I think that maybe there's an adapter for the Valhalla Linns. True? I'd sure like to get some of those 45 rpm Fantasy Jazz reissues.