loose heel/toe shifter

[maestro319]

When I bought my trike off of E-Bay it came with a homemade trike "kit". Because of this I couldn't get my toe under the shift lever very easily. So I put the heel/toe shifter that came with the bike on. Now,after I drive it for awhile, this heel/toe shifter comes loose. I tightened it finger tight at first, then I used an Allen wrench to tighten it a little past finger tight. Today it came loose again !!!!!! I don't want it to come off while I am riding, but being loose makes it hard to shift easily.
QUESTION: Just how tight can I tighten it without it becoming too tight to shift??

[RBGERSON]

Use a lock nut on the part you are tightening and carry a spare nut

[Jeeper]

Put some locktite on the threads and it won't come loose. The red stuff is the best, the blue if you want to be able to loosen it easily in the future.

[WingAdmin]

I'd put loctite on it, then tighten it until it starts to bind the pedal - then back it off just a tiny bit.

[cearleyma]

When I bought my trike off of E-Bay it came with a homemade trike "kit". Because of this I couldn't get my toe under the shift lever very easily. So I put the heel/toe shifter that came with the bike on. Now,after I drive it for awhile, this heel/toe shifter comes loose. I tightened it finger tight at first, then I used an Allen wrench to tighten it a little past finger tight. Today it came loose again !!!!!! I don't want it to come off while I am riding, but being loose makes it hard to shift easily.
QUESTION: Just how tight can I tighten it without it becoming too tight to shift??

Just a suggestion, take some "high temp" rtv silicone sealant, coat the threads of the bolt & tightien it just beyond finger tight (or whatever torque level required in the service manual), and allow time to cure (maybe 24 hours). This sometime works & acts element to keep bolts & nuts from backing off, but makes it a little easier to remove if you ever have to for maintanance.

[maestro319]

Thanks to all for the Loctite suggestion
and the silicone suggestion. I'll do little more research and probably use one of those ideas. Thanks again guys.
P.