I can’t believe nobody has commented on this idea from jtrops. Quick and easy, no maintenance, light weight, and virtually free, and seems like it should be plenty effective. +1 from me, and I’ll be putting some on mine for sure.
Haha, that idea only works on the outer hole; How would you slip it on if your crank is on the longest hole, leaving the inner hole exposed? 
Put it on before the pedal?
ok that makes sense, lol! I was thinking that one end was closed and slipped onto the end. There is one problem; the inner side of the cranks–at least the moments, are recessed quite a bit and when stretched snugly, the tubing would leave definite gaps, allowing water, mud, etc to get in. The outer side are a bit concave as well, but if the rubber tubing was tight enough it might seal it sufficiently.
Here’s a simple yet effective solution. perfect fit and seal. Quick on/off. 
You can use these nuts that stay tight.
Yep, slip on before the pedal. Although I agree it wouldn’t totally seal with Moments, but I’d probably just put a fairly long sleeve on there. My thought is not to try to totally seal it, because I think inevitably some water will get into anything, so a little air space will let it dry out. But should be enough to keep out any significant mud etc.
BUT, now I’m really liking the hardware store solution. Probably best to keep the threads greased a little in case some water does seep in. On the other hand, it may not be worth the extra weight for the bolt instead of the (as yet untried) inner tube solution. Hmm. I love this kind of dilemma! 
super simple solution, at least for those of us in the countries where we can get non metric hardware.
Buy the right thread sized bolt in stainless steel, run it through the crank from the back side and cut the excess bolt flush with the crank…
Now when out on the trail you can break that bolt loose with the pedal wrench and turn it out with your fingers through the spokes or what works for you, and switch them to the other hole…
Being stainless solves the corrosion / water problem, and if you shop well you’ll find bolts that will fit the pedal wrench.
Weight issues? Really? Seriously? I just weighed a similar bolt, 2 ounces. remove a sticker or two to make up for it or drink less beer / soda that day
Bar-end caps that have a screw built in so that when you tighten it, it expands inside the bar-end. This might just be the best option, and ready made if it fits!
Yeah Chicago Screws and sex bolts are the same from what I’ve seen.
I didn’t want confuse the people who use bolts during sex. This is the internet after all. 
I think you just invented crank condoms. 
I’m down with the dirt. It’s nature’s locktite. 
Haha, why not go all the way and take off those pesky bearing caps too! After all, a smooth rotating wheel without any friction just isn’t enough challenge! And while you’re at it, make sure to get a good helping of mother earth into your seat tube and magura lines! 
Good times!
Alright, you got me – being a weight weinie is just my excuse for being too cheap to pay the couple bucks for something (heavier) that might not be functionally much better than the free (and lighter) crap lying around in my garage. 
At least this little thread I started has spawned 3 pages (so far) of interesting ideas in quick succession. Bouncing around new ideas and getting people thinking is a good thing!
I filed the first thread on this pedal from my Coker to show what could be done. The starting thread was removed up to where it became full height. Giving it a flat or even a reverse face like a tap will clean just about anything. It will work just as well on the left handed thread of the other side.
Now just don’t cross thread that thing, like you said it is like a thread tap.
Good point
Hey Terry, when you make millions from this remember I suggested it a while ago
Happy to share the millions though:D
Haha, great minds think alike! It’s really a no-brainer imo, and the dual holed cranks should come with a protective plug or cap. But easy to do on your own anyway, if you so choose.
there is some round insulating foam that i got from lowes to use as backing for blowgun darts … that would work fine. if you wanted something that screwed in, get some plastic bolts and thread in from the inside and cut off the excess with a hacksaw or something. idk about the side that has left helical threads.