Mud/dirt/water guard caps for dual-hole cranks

It dawned on me while riding my new kh 36er on the trail the other day, that the exposed second hole in the each dual-holed crank was getting sprayed with water, mud and everything else!

The other danger is if the uni falls on a sharp rock and hits that open crank hole it can destroy the threads as well. So I thought it would be a great idea if Kris could have some plastic protective caps made specifically for the dual-hole cranks.

I brought this up earlier today with Josh at UDC, and he liked the idea, and thinks rather than a “pop in” type cap, a plastic cap that would screw in by allan key would be best, and also be long enough to protect both sides of each hole.

Anyway, I really think the caps would be a great way to keep the otherwise exposed holes clean so that when you are ready to switch holes, there would be no mud, dirt, dust in there, or possible thread damage.

I also think that in addition to these caps being made, that they should be included with every pair of dual holed cranks at no extra charge, just like crank axle hole caps or bar end caps, etc. I will expect my percentage once they are being produced, haha! :wink:

In the meantime, I’m using a small piece of duct tape, which seems to hold well in wet weather, but needs changing each time. The other option would be to use something like the expanding earplug-type foam, (cylindrical in shape) and compress it enough to get it into the holes, then let it expand. that should also work. :slight_smile:

I have thought of this problem before, and this sounds like a perfect fix to it! Great idea!

Is it necessary? Will anything actually be damaged by the mud and water?
I think a snap in cap would be more convenient than something that threads in because when you want to change to the other holes you have to undo both pedals and caps then replace everything again.

Seems like if it gets caked with mud then you can just put your pedals on and it will clear out. no?

The dirt and mud will make it harder for your pedal threads to go in, and create friction which will cause the threads to grind through the debris, and can make it very difficult to screw them in. There is also more chance of mis-threading. The threads on both the pedals and INSIDE the crank holes should be clean and also regularly lubed. Pretty basic stuff. :smiley:

Not so much. It will mostly be damaged by screwing in a pedal at a later date. Cleaning out inside threads is really a pain to do properly!

Methinks you weren’t around when all the unicycles came with snap-in caps over the crank nut. They invariably fell out after a while. I had some aluminum ones with real threads, but they tended to die after a while as well (too lightly constructed).

The simplest idea so far is the pieces of foam jammed in there. It should be foam that repels water though, rather than the kind that holds it like a sponge. Otherwise it just holds all the moisture and dirt in place.

Josh’s approach sounds nice and classy, but is highly unlikely to happen without cost. It would be the best solution for people who don’t switch holes much.

For the cheap approach, I think the right kind of tape would hold up for a while, except where it rubs your foot…

Use a drop of easy release loc-tite withe these…

oops wrong thread size… looking…can’t find correct thread… could make it easy enough at work though

What about a small section of old inner tube around the crank arm. Just slide it over the open hole and it will cover both sides. You might need to use a road bike tube to get a tight fit, but I don’t see why it wouldn’t work.

I think Terry’s idea is great. I would also second the idea of having a screw-in cap as there will be much less chance of it coming out. Any pop-in cap will come out, no doubt about that.

I think Terry’s idea is great. I would also second the idea of having a screw-in cap as there will be much less chance of it coming out. Any pop-in cap will come out, no doubt about that.

To be really effective at keeping the thread clean it would have to go all the way through, or have a cap on both sides of the crank. I’m with the foam idea - a mushroom-shaped lump of closed-cell foam could be pushed in from the inside (frame-side) of the crank and leave the outside edge smooth with nothing to catch on your foot.

But I reckon you Americans worry far too much about getting things wet and dirty anyway. It’s a big coarse steel thread after all.

Even better, decide what crank length you like and stop messing about with these gimmicky “emperor’s new clothes” dual-holed things :wink:

Rob (waiting for the flames)

I think I will be cutting my old bent cranks up and using the thread from that.
That way it should protect them, will fit well and will easily removed and put in.

Not sure how easy that will be for everyone to do but is fix for the time being at least

Hahaha, I agree with Rob.
Why worry about a little mud getting in the holes? Just poke it out with a stick and take a little more care when changing crank positions. :roll_eyes:

You could fill the holes with a dab of grease if you’re that worried about dirt damaging the threads.

Perfect! Wipe it out with a stick before you put the new pedals in and you’re golden. Any non-greased plug that isn’t tightly threaded will only serve to hold moisture in the threads.

Haha, I see your winkie, but I do change crank holes on my 36er, depending on whether I’m riding offroad or street, and sometimes I change them on the trail to the shorter hole, if I’ll be going downhill for a while, or a long flat stretch, and want more speed. I like the flexibility and option to make the fast switch without having to change entire cranks.

On the subject of protecting the “open” crank holes; Another option to a screw in plastic cap that extends all the way through, or the closed cell foam that would expand inside the hole, I also had an idea for a kind of crank hole “muffs”! Same idea as ear muffs, but obviously on a much smaller scale. The idea being they go on fast, cover both sides of each hole, and are one piece plastic that is molded so that you have to pull the muffs apart to fit over each hole, and there is a small inner ring that pops inti each hole to keep then inside. The way they’re molded keeps them pressed against each hole, and the connecting cross piece is flat so it wouldn’t be obtrusive. Quick on/off, simple design.

I’ve got it… polystyrene foam packing.
Like these ones that I happen to have here (and was about to throw out) fill the gap perfectly and of course expand to fill the space.

Another possibility would be to use heat-mouldable plastic to create a removeable plug.

Maybe some plastic “Chicago Screws” would work?

They’d need a wide enough head. The biggest I’ve found in 5 minutes of searching is 0.54" diameter. Here. I’m not sure if that’s wide enough to cover the holes.

Pedal threads are 9/16", which is about 0.56", so those are probably a tad too small. I think the 9/16" is to the outside of the thread though, so it might sit nicely on the edge if you’re lucky.


OOOOOO Sex Bolts

Sex bolts (never heard of “Chicago Screws” before) seem like they would be the most secure while being easier to remove quickly than a plug threaded for the entire length of the pedal hole.

I just got my pair of dual hole cranks and think that I might just start carrying a stiff bristled toothbrush with my tools.

Y’know, we should just let Sask answer questions from here on out. This is all that is really necessary before a pedal change… a swipe with a brush. Use a little WD-40 if you’re really paranoid.

Really, poking out the dirt with a stick? What, are we cavemen?

As Rob said, they’re coarse steel threads. You’re gonna have to work to mess those puppies up. Some little piece of plastic isn’t going to do balls to protect those from that miracle “rock just bashed my crank threads” UPD someone’s worrying about.