On Tue, 03 Jan 2017 17:04:40 -0800, Joerg
wrote:

Is there something stronger than the usual rubber cement in the patch
kits? Ideally something that won't dry out so fast or where multiple
cheap small tubes are available.

Contact cement. It's a neoprene rubber based goo that remains fairly
flexible if applied in a very thin layer. Smear some on both the tire
and the patch, let air dry for at least 10 minutes (longer is better),
and stick together with a little compression pressure. I've used a
roller, two blocks of wood and a C-clamp, and beating on the sandwich
with a hammer. They all work.

Rubber cement is a latex rubber based goo. Otherwise, it's similar to
contact cement. It also uses many of the same solvents as contact
cement. Bicycle patches use heptane, naphtha, or a mixture of both.
Rubber and contact cement use these or other organic solvents. There's
also a water based version of rubber cement.

Contact cement solvents won't evaporate as fast as rubber cement
because the contact cement is thicker in the bottle and forms an
effective barrier. However, the solvents will rapidly evaporate if
the can, bottle, or tube is left in the sun.

Contact cement on bicycle tubes is nothing new:
http://www.bicitoro.com/how-to-glue-inner-tubes/
However, if do some Googling, you'll probably find testimonials from
people trying contact cement, and claiming it doesn't work. The
problem is that while rubber cement vulcanizing patches require
cleaning and sanding before applying, some people seem to forget to do
these things when using contact cement.

I've also tried glue used for patching my wet suit:
https://www.walmart.com/ip/Mcnett-14114-Seal-Cement-2-Oz-Tube-Black/21970283
https://www.youtube.com/watch?v=q9QK0yF540c
https://www.google.com/search?q=neoprene+wetsuit+glue&tbm=isch
http://www.bodylinewetsuits.co.uk/2015/01/12/using-black-witch-neoprene-glue/
I've only done one tire with wet suit glue and found that it didn't
last. However, that was in a rush, with little preparation, no
clamping, and I used a piece of vinyl for the patch. I suspect I can
improve the bond if I were more organized and careful.

The reason is that I sometimes have larger holes from side wall
blow-outs. Not inch-long gashes but one or two tenths of an inch long.
The tubes I use are super thick and, therefore, expensive. $15-20 each
and that's not something to be thrown out lightly. Instead of the li'l
REMA patches I need to use thicker rubber from an older sacrified tube
but this has to be vulcanized/cemented really well.

Hmmm... contact cement is more expensive than rubber cement. If I had
to find something cheaper than rubber cement, methinks RTV (room
temperature vulcanizing rubber) would probably qualify. The catch is
that you might have to wait overnight for the RTV to harden.

Anyway, I suggest you sacrifice an old tube, cut it apart, cut some
slits, patch with the various available glues, and test the results
with a pull test, peel test, pressure test, and flexibility test.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558