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Threadlock (Loctite) and Lexan

slower than...

slower than...

Peets Coffee Junkie
Joined
Jan 19, 2005
Location
Oakland Hills
Moto(s)
Ducati
For those that don't know this already, Lexan apparently reacts (very badly) to Permatex Threadlock and/or Loctite. It isn't even direct contact that is the problem, because while the Threadlock dries/cures, it apparently "off-gasses", and that is enough to deteriorate the Lexan.

Here are picture of my timing belt cover. I had it on the bike for years with no problems. But after my recent Dyno, (when most of the screws vibrated out), so I decided to use some Threadlock. I tried to make sure it was only on the aluminum frame, wiping any excess that would touch the Lexan lens. I did not even tighten down the screws to "hand tight", when within two minutes, every hole developed spider cracks.

Anyone else have similar experiences?
 

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Is that Lexan cover a Ducati part, or after market for Ducati owners that want to show the belt?

If it is a Ducati part...What does Ducati use to keep the screws..from un-screwing?

Aren't there any screws available with a little Nylon button on the threaded shank?, that is a common self locking type of screw.
 
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Yep, it does a pretty good number on polystyrene too.
 
A little RTV, (I prefer the permatex blue sh*t) on those threads will stop them from falling out.
 
louemc said:
Is that Lexan cover a Ducati part, or after market for Ducati owners that want to show the belt?

If it is a Ducati part...What does Ducati use to keep the screws..from un-screwing?

Aren't there any screws available with a little Nylon button on the threaded shank?, that is a common self locking type of screw.
Click to expand...

It is an aftermarket part by Rizoma, an Italian firm. The lens already comes screwed to the billet cover, so I don't know what they used.

These are weird Italian metric screws, and are VERY short, so I don't know where to find them with nylon buttons. Someone suggested nylon washers would help. I worry about the heat from the engine, but maybe it would be okay. Any washer would need to be paper thin though, since the screws are so short, and the way the lens sits into the recess of the billet frame.

I do hear that these screws have vibrated off on other bikes with these covers. I've been told that over tightening the screws will also cause the lens to crack, because of the engine vibration. Threadlock and/or Loctite isn't the answer. For now, I will just check for a snug grip before each ride.
 
*I wonder if your thread title is messing with the other mods too. I keep reading "Lock Thread" and wonder what some knucklehead's up to :laughing*
 
Is this as it is drying or simple contact? One option is before installation is to put a dot on the threads and let it dry, but I agree maybe a dot of RTV would be a better solution?

Thanks for the heads up since I tend to use Locktite quite a bit!
 
Couple of thoughts:

1) If you live or work near Olander, give them a try for the screws. I work right around the corner from them. I've popped in many times looking for really oddball fasteners that I couldn't find anywhere else, and I've yet to stump them.

2) I wonder if the Loctite that comes in the little chapstick-like tubes would cause the same problem? It's obviously a different carrier than the liquid form. I don't know if it would 'offgas' the same compounds. Maybe worth giving them a call.
 
instead of loctite try something a little more rednecky... lots of solvent based products will attack plastic. anything that's acrylic safe (lexan is a toughened version of acrylic) and dries from liquid to solid would work to "lock" threads. hell whiteout might work, maybe some dried coffee from the next starbucks posing session? avoid anything with acetone in it.

to to tap plastics and get a scrap of lexan and see if you can replicate the problem, then use various gooey things to hold the screws in place to see if they're ok. i bet tap can replicate your windows pretty easily as well.

i'd also try RTV as well, they're based on a different solvent/cure system than loctite type of products

Nonsequitur said:
Is this as it is drying or simple contact? One option is before installation is to put a dot on the threads and let it dry, but I agree maybe a dot of RTV would be a better solution?

Thanks for the heads up since I tend to use Locktite quite a bit!
Click to expand...

it's kindof hard to tell from the one picture. "offgassing" tends to haze plastics. it will deposit/create a film of making it look like frosted glass. i've also seen acetone work it's way into plastic like you'd expect dye to stick in fine cracks on something except it goes IN instead of spreading (i was making this awesome pimp stick for a party in college, and after buffing the clear acrylic end i went to clean the residue off with acetone and ended up with a bunch of spyder cracks. sucked)
 
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