ferrit worrier wrote:I think what you mean is one of these ...
...the front mech sits in the recess and is secured by a socket head screw through the unit which is then secured to the "Braze on" in the normal way.
These are what Mick F refers to as a "FWA"
Malc
No I'm trying to envisage the possibility of something slightly different that raises or lowers the FD but keeps it in the same plane (rather than moving it back).
Here is a very rough & ready image of the bodge version (based on an image of a clamp-on FD mount as that was the first one I found) FD adapter.jpg The idea being to clamp the FD on the lower bit (using the bottom bolt). Does that make any sense? It it likely to be feasible/strong enough?
Rick.
Hi Rick I see what you mean, Ok if you need to move it some distance but there may be a question of rigidity, given the pull on the cable the steel strip would bend, but, an ally block machined might work providing that the top of the FD will allow clearance for the bolt head. the original concept was developed. for Mick's TSR to lift the changer high enough to clear the larger chain ring. on the TSR I think the tube that the FD sits on is narrower than the seat tube. viewtopic.php?f=15&t=104103 then Deliquium posted that he needed to lower his FD so we tried an adapter (FWA) upside down and it worked. I could be mistaken but I don't think the set back is as critical as the top clearance. It's a pity Moulton couldn't have foreseen the need for a bit of adaptability and come up with a spacing ring that fitted over the frame tube that a conventional FD with seat tube diameter clamp ring could have been used. unfortunately there is a braze on in the way. The reason for the thickness of the adapter is the fixing screw sits directly behind the braze on in both applications so allowance has to be made for the thickness of the head of the screw plus leaving sufficient metal under the head to support the mech when tightened up. It would be interesting to see if there are any other adapters, Brucey mentioned others up thread but I've not looked for any yet.
Malc
Percussive maintainance, if it don't fit, hit it with the hammer.
adaptors of this sort almost invariably set the mech backwards somewhat; 'tis the nature of the beast.
If you look at the Rotor offering you will see that it comes with a wedge piece, so that you can bring the outer plate of the mech to better match the big ring.
BTW I still think that much the easiest thing to do is just to buy another mech.
Having switched to using 46t triples and having exactly the same problem as the OP on a couple of bikes I have to agree with Brucey that by far the easiest solution is to fit a different front mech with longer cage drop. Fwiw if using campag some of the older mech’s have a 50mm drop from centre of the fixing bolt to the bottom edge of the outer cage plate, which sorted me out nicely.
I cannot disagree with that idea, except that sometimes it could be possible that no mech would work properly without a device.
In my situation, I could have used a mech with less of a drop, but it wouldn't have worked with my wide-range triple. The longer drop was required for the inner ring.
I must say though, the the gear change is brilliant and there's no chance of the chain de-railing onto the BB. This is due to the deep inner plate of the front mech. I couldn't have wished for a better system to cope with the idiosyncrasies of the Moulton.
No doubt the FWA and variants aren't necessarily the best solution in certain situations ............ but that doesn't mean it should be discounted.
I know this is an old thread, but deliquium's old FWA is now lowering the front mech on my Eddy Merckx, which can take a minimum big ring size of...52T! Eddy didn't make bikes for softies.
I reckon the front mech could be drilled and tapped further up as an alternative solution (I need an extra 2.4mm when the mech is at the bottom of the slot, to give Shimano's recommended 3mm clearance*) Front mechs are cheap s/h, even DA ones. I might give it a go.
*personally, a hair's breadth is what usually I go for
rogerzilla wrote:I reckon the front mech could be drilled and tapped further up as an alternative solution....
most DA FDs have the mounting bolt offset to the high side of the tab anyway. This means there usually isn't enough meat to drill a second hole. Not and have the FD position stable too; there are quite high forces on it during some shifts.
I'm no designer but would it be feasible to make an adapter that fitted to the front of the existing FD mount that adds an extension to the position in the same plane as the existing one? The bodge version would be something like another braze-on FD mount with the frame mounting bit cut off with a strip of metal with bolt holes/slots to join the 2 together plus a threaded crescent bit to bolt through the original FD mount.
Actually, if the mech sat a little firther forward the curvature would fit a small chain ring better, wouldn't it? I've been pondering this myself because I prefer a 46t chainwheel too.
most DA FDs have the mounting bolt offset to the high side of the tab anyway. This means there usually isn't enough meat to drill a second hole. Not and have the FD position stable too; there are quite high forces on it during some shifts
I agree so I propose to try screwing and glueing an aluminium screw into the bolt hole and then drilling and tapping as far up as seems judicious.