Using Indexed front triple mech as a double

[BalkanExpress]

Pretty much as the title says.

I am transferring some parts to a new frame and have run into a problem.

The old bike was a mixture of Campag Athena and Chorus with 8 speed ergo shifters, a triple chainset and long cage rear mech.

For the new bike I've gone double chainset and put on a short cage mech, the 8 speed ergos are fine as the left shifter works on doubles and triples but the front mech is a nightmare. After a couple of hours in the garage with me, Calvin from Park tools and his front mech video I have got nowhere So I an trying to isolate the problem.

The front mech is the old triple, not ideal, but I understand it can work if you fiddle around.

Second problem is that I am mechanically inept. How inept? Well the front mech has a braze on mount, I've only ever fitted band on front mechs previously and so am struggling (as in have so far failed) to even get the front mech at the right height and parallel to the chainring . That's just for starters, I think, but only think that I have identified which is the L and which is the H screw (and yes Calvin and his 'tache have been avidly watched many times) and lets not go there with the indexing.....

So where do I go from here? Instinct is to head to my LBS and tell him I've made a mess of it and can he sort it out. This is a regular occurrence.

Or, is there a fix for this? please note the use of the terms "simple" or "you just" will be met with If it were simple for me it would be done by now...

and breath...…..sorry for the rant open to all and any suggestions ..except of course reverting to a triple I have plenty of bikes with triples but this will not be one of them

 

[Ajax Bay]

Braze-on fitment for FDs are really simple: you just adjust the outer cage plate to align with the large chainring and, when pushed out immediately above the teeth (wedge it - cable not connected) have a gap of 2-3mm. Worth unscrewing both limit screws a bit.
Too much? Drop it. Too little? Raise it - on the braze-on. Not aligned? Swivel it. And screw on tight.
Worth having an in-line barrel adjuster for the FD cable.
Done that? Adjust limit screws so that (H) the cage allows the chain to shift up to the large ring (and when in the smallest sprocket not rub) and (L) allows the chain to align on the inner ring (and when in the largest sprocket not rub). Pull cable tight and clamp. Small tweaks thereafter (in-line barrel adjuster).
Be aware that an ergo shifter designed for a triple connected to a double FD can be damaged/broken if the rider applies force to change up (increased cable tension) and doesn't realise they are up against the 'hard stop' of the upper limit screw (H).

 

[raleighnut]

^^^^^^ Wot e sed