Triple to double?

[neilob]

I am wondering if this bodge will work. I am building up my retro bike for a couple of events next month and hopefully Eroica 2019 in Tuscany. This bike will get ridden no more that four times a year so big investment is not a very good idea. I need low gears but my rear mech is short cage and my front mech is double. Is it feasible to use my 110/74 bcd triple chainset but just shift the inner two rings....say 39/26? The outer ring could be a dummy or one of those chain guards from Spa designed for their chainsets. I am not sure if the front mech would work when set up on limits so it can’t go to the big ring. My gearing would then be max 39/12 and min 26/28 which feels about right even if light at the top.

[tatanab]

No trouble at all.
Front mech will not care, I've been using 40/24 chainrings with a Campag triple mech for 6 years now. I am told that some Shimano MTB mechs are long and foul the chainstay, but you will not be using one of those anyway on an eroica machine.
Rear mech - short arm should be fine - way back in 1975 for a tour in Yorkshire I used 40/26 with 14-26 5 speed block and a Campag Record mech. I do not recall if the chain ran a bit slack in small/small but that doesn't matter because you would not use that anyway.

[fastpedaller]

My triple rarely gets used in the big ring, and indeed has never been used in the small ring (except to test it initially)

[pwa]

My Missus has a double made up that way, with a largest ring of 40t. She does spin out at speed downhill, but that just means she has an enforced break from pedalling. On mountain rides most of the time is spent either climbing or freewheeling, so your climbing gears matter a lot more than fast descending gears. 40/28 works with my wife's front mech, but what combo works with yours may be a bit different. The outer space where a large third ring would go is occupied by a black guard ring and looks neat.