After fighting adhesive failures all year with my RSI Pressure Trace system, it was time to get serious about testing adhesives. Strain gages are encapsulated in a rubbery plastic that most glues don't stick to. The gages are too expensive to use as guinea pigs, so I used strips of a bicylcle innertube glued to pieces of scrap steel. The innertube seems like a similar surface so hopefully it will give similar results.
The pieces were washed in hot soapy water and dried prior to gluing.
Loctite 401 was recommended by RSI at one time.
JB weld is the favorite of Denton Bramwell.
Devcon 30340 "Flex Superglue" elastrosized ahehsion creeates a flexible bond, won't crack when bending, resists impact, great for rubber, vinyl and leather. It sounded good.
Devcon 30350 "Plastic Superglue" works on all kinds of plastics.
After drying overnight, I tried peeling the rubber strips off the metal.
|Loctite 401||peeled off, glue stuck to rubber but not steel|
|JB||peeled off, glue stuck to steel but not rubber|
|Devcon 30340||stuck, couldn't remove with fingers|
|Devcon 30350||peeled off, glue stuck to rubber but not steel|
I'll be the first to say that this is not a highly scientific test, and I can't be sure that the innertube is a good substitute for the strain gage material. Also, this test does not consider the high temperatures that will be encountered on a rifle barrel, or the effect of cleaning solvents and oils. Still, even a crude test is better than nothing.
Only the Devcon 30340 could not be peeled off. The others came off with very little effort -- just like most of the strain gages that I have removed from barrels.
RSI has recently dropped Loctite 401 in favor of another product. At one point they told me they were experimenting with a Devcon glue that was very flexible but when I asked for a product number they would only say
We found another cyano with the same properties as the Locktite but at half the price.