Changing the triple chainset for a double chainset on an old bike

[tadpole]

This might be a stupid question but my 15 speed BSO currently has a Shimano 48 38 28 triple crankset, the only problem is, due to my misuse when changing down gear, the gap between the top ring and the next ring down is wide enough to occasionally let the chain drop in between the two rings and Jam. (I avoid this by changing down quickly and hoping I don’t go too far and change all the way down to the little ring, but sometimes it still jams and make the gap wider and the problem worse) I hardly ever use the middle ring and have only used to bottom ring twice in the whole time I’ve had the bike.
My question is I’d like to change the triple for a double, maybe a Shimano 52/ 42 crankset, I’ve a three piece crankset with a square taper, and it’s an older style cup and ball style. The gears are not indexed in anyway and are changed with friction levers on the handlebars. What do I need to look out for? Are there differences in the thickness of the front chaining, and will that affect the chain width? (Bikes currently fitted with a “narrow” chain)
I don’t want to spend a whole lot of cash on it, as I’m getting a new bike in March.

 

[mrandmrspoves]

Not a stupid question at all. It's easier to swap from a triple to a double than moving to a triple from a double. Chain should be fine as width is determined by how many rear sprockets. Before spending money though, it may be possible to bend the chain rings back to close the gap. Probably easiest to do by removing from the bike and using a vice to dish the middle chain ring back outwards.

 

[boydj]

Just about any cheap square taper double chainset would do. The chainline won't be ideal because the bottom bracket axle will be slightly longer than required for a double. But, with friction shifters, all you really have to do is adjust the limit screws on your front mech.

If you are already using a 'narrow' chain, then it should not matter if your new chainset is rated 8, 9, or 10 speed. (Though that may be part of the reason why the chain has been dropping between rings.)

 

[tadpole]

Thanks for that, I may try having a bash at fixing the gap with a vice, but as the chainset is off. I may just fit a new one. and then take my time repairing the old one, with a hammer and a block of wood.. maybe.