wdmn

Hello,

The front derailleur on my (early 80s?) Mercier stopped working this winter. It's a simplex piston changer with a metal fastener but black plastic body. I've taken it apart and cleaned it as best as I can (it doesn't seem possible to open the plastic case), but I still can't seem to get the piston to move. Looking for suggestions.

Thanks



Side view

back view showing simplex logo

trailangel

Buy new Shimano front DR

wdmn

Thanks.

They will fit on the french bike?

Troul 

soak it in hot thin motor oil.

trailangel

They usually come with plastic inserts to allow for different seattube sizes. Ya know, it's fifty years old. Mine broke 49 years ago.
Maybe if you have the metal clamp instead of the plastic clamp, you can get it to work again.

bertinjim 

wdmm-

The red plastic disk can be carefully prised off. Do so and then add lubricant or penetrating oil on the exposed mechanism within. Then, hold the derailleur with the rod vertical and allow a fresh application of oil or penetrant to ease into the mechanism that way as well. Once the derailleur moves freely, the red plastic cap should snap back into place with a little thumb pressure. Remount the derailleur but be careful of overtightening the metal retainer as these derailleurs have a tendency to crack if this is overdone.

grizzly59

Maybe you can free it up with some oil in the mechanism. Good idea from Bertinjim. I usually have the best luck fixing Simplex front or rear mechs by using a 5lb hammer. Place mech on concrete, bash with hammer until you have 10 pieces or more. Deposit in dustbin. Find an old Shimano in the spares box, oil and install. Seriously, French bike- you may have a time finding a replacement that fits the seat tube exactly. Coke can might be needed for shimming. There are some adapters that clamp on and take a braze-on derailer.

wdmn

Thanks. Going to give it a try.

veganbikes

You might consider asking moderators to move this to the Classic and Vintage subforum, there are probably a few more folks who hang out there that are suckers for Simplex and have a few extra tips and tricks up their sleeves.

A shimano derailleur should work so long as you sing La Marseillaise while installing it.

Geepig

That cable housing takes me back 40 years

I really hope you can get it to work again, who needs to be like everyone else.

sovende

First thing would be to release that old frayed cable! That alone may release the mechanism and allow the push rod to retract into the derailleur body! Soaking or spraying some sort of “penetrant” as mentioned may facilitate that action. You can also back out (and remove) the limit screw that runs parallel to the push rod. It’s possible that it is jamming the part of the lever that advances the push rod (but unlikely). The red cap “can” be removed but there’s a good chance you’ll bugger it up . It would be the second to last thing I would remove. The last would be the pivot screw that secures the lever that advances the push rod. With the pivot screw and the red cap removed all of the internal parts can be removed and cleaned. Pay close attention tho so it can be reassembled correctly .

sovende

This diagram may be helpful

sovende

This diagram may be helpful

sovende

Sorry for the double post above .
I recently refurbed the exact same Simplex front derailleur. Don’t know if I’m actually going to use it but it’s now in a condition that would allow me to do so if I choose .
I did not completely disassemble mine. I left the “red cap” in place and didn’t remove the pivot screw or the lever that moves the push rod. The mechanism still functioned so I didn’t feel the need to do so but I did soak it in kerosene. I did soak all of the fastening and adjusting screws in EvapoRust and they cleaned up nicely.
RE: fitting these derailleurs to differently sized seat tubes, the cast metal (Zamak ?) “U” clamp is different for the different tube sizes. (1”, 1 3/32” & 1 1/8”). Shims would prolly do the job tho .
I'm pretty sure these derailleurs are considered “low end/ entry level” but still have a place for those that restore bikes to original specs.

xiaoman1 

^^^^^Good information for those seeking originality and trying to figure out how mechanisms work.
Best, Ben