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Sprocket replacement - in the field
http://www.hobie.com/forums/viewtopic.php?f=60&t=12947
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Author:  mmiller [ Wed Jul 01, 2009 8:45 am ]
Post subject:  Sprocket replacement - in the field

Another Gem from our friend roadrunner!


Lets say you're on an extended trip in your kayak and you accidentally strike a submerged object and break a mast. Rare but possible, and fixable in the field if you're prepared. Using the one remaining fin, you can easily pedal to your next destination or shore. In order to fix this, you need to have just 3 things in your emergency kit:

1. 1/8" Allenhead wrench
2. spare sprocket
3. spare mast (pre-assembled on the spare sprocket if possible, especially if you're using the '09 threaded masts).

4. (optional but desirable) Loctite Blue thread locker

Procedure:

1. Immediately remove the dangling fin and mast from the clew outhaul and proceed to shore as appropriate.

2. Find a semi clean surface to operate from.

3. Partially unscrew the Allenhead screw that locks the sprocket shaft.
Image
Note the alignment mark on the end of the sprocket shaft (more on this below).

4, Using a rock or any makeshift hammer, pound the sprocket shaft half way out releasing the damaged sprocket. There is no need to loosen or remove the chain/cables. Use your broken mast as a push pin. If it is missing, try a stick or use your new mast/sprocket and pound with your hand. If you keep your Drive properly lubed the shaft should be fairly easy to slide back. If there is corrosion in the shaft, try working it it a little at a time in both directions until it starts to break free.

5. Slide the sprocket over to one side. This will allow you to release the chain. You can pop the clew outhaul off if necessary.
Image

6. Replace the sprocket / mast assembly and reverse the procedure. Note, the sprocket shaft detent (or groove) must align with the locking Allenhead screw. This is blind though, so the alignment mark on the end of the shaft conveys that information.

7. With your sprocket shaft correctly centered and aligned, use some Locktite blue to lock in your Allenhead screw so it doesn't back out. If you have not pre-installed your new mast, use additional Locktite to lock in your threaded mast or Allenhead retainer as appropriate to the best of your ability. In this case, wait several hours until exposing the Drive to water.

Here are some tips to make things easier:
1. If you've replaced or upgraded your older sprockets to the newer brass insert style (standard for '09 models), you can relegate your older sprocket and mast as your spare -- they are interchangeable as a sprocket -- mast set.

2. Pre-grease your spare sprocket and keep it sealed in a plastic bag or tape the ends.

3. Scribe both ends of your sprocket shaft before your trip so you will have a permanent allignment mark for the Allenhead locking detent.
Image

4. Make sure you get the middle chain link in the master cog FIRST and all chain links seated when replacing your sprocket.
Image

5. Practicing this operation once ahead of time will make it a lot easier if and when the time ever comes that you need it. You can re-grease your sprockets and inspect your masts as part of your pre-trip preparation while you're at it! 8)

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