>>2523291To add, you can also get the bus.
There is a few buses which run up that way from Glasgow. Will be much cheaper than train.
Iirc there is a bus which goes direct from Glasgow to Arrochar, twice a day (976 to Oban).
From the bus stop it's only a 5 minute walk to start of the trail up the cobbler and/or Beinn Ime.
The cobblers a great wee mountain if you're just looking for a day trip. Great scrambling, pic related.
Can be up and down in plenty time to get the evening bus or train back to Glasgow.