Hello

I want to change the chainset on an old 10 speed racer from a double to a triple. Is this possible?  Would  I need a longer  spindle? Has anyone ever done this? I would welcome any advice.  Currently it has 50/40 on the front and a 14 -30 range on the back and I'm finding it hard to get up hills these days.

That's quite an old version then with a fixed cup BB. The chainrings are offset on more recent versions, so they run narrower axles to achieve the same chainline.

If you want a cheap replacement, look for Shimano Sora sq taper version and it should run a 115mm BB.