Here's a close up look at the newest masts and sprockets for the Mirage Drive. I understand these are standard on all the '09's and can be retrofitted to the older Drives as well. They are already available and I have a set installed in conjunction with last year's redesigned drums and chain/cables. IMO, these latest upgrades finally make the newest Drives superior in reliability to the venerable old "stainless" drives (which we rarely use any more).
This is what the old (left) and new sprockets look like next to each other.
Notice the slight difference in color between the sprockets. The newer sprocket is a little harder and should have excellent wear characteristics. Obviously the Allenhead screw is gone and we should expect to see the end of "sprocket wallow" with the brass insert.
Mast installation is simple -- drop some Locktite Blue in the hole and screw the mast in (a screwdriver slot is conveniently located on the opposite end of the mast. No need to orient the mast slot, no more worries about screw tension or backing out.
Here's a cutaway showing a cross section of the insert. Nicely engineered, with flanges to prevent backing or turning.
This next view shows the mast. It uses a heavy shouldered, shallow thread pattern to maximize strength.
Bent mast? I bent one of these and had no problem straightening the mast without removing it from the Drive. Actually, it would be difficult to straighten any other way because of the potential for damaging the threads.
Cost? About $60 for a set of 2 sprockets and 2 masts. You must replace mast and sprocket together, but you can do so one at sprocket at a time.
Downside? Better not forget to use the Locktite (Blue). It works great as a thread locker and these need
to be locked in. If you loosen them for any reason, re-apply new thread locker.
Overall evaluation: These should eliminate the last of the issues that have occasionally come up with the old sprockets, especially when using Turbofins. The Hobie engineers have done a great job of improving the ruggedness of the Mirage Drive to handle the heavier demands necessitated by the newer series of fins. Finally!
Do you need it? You should inspect your masts to insure they are not twisting or moving in their sprocket holes, and that the Allenhead screws are not backing out. If you have a problem, there are 3 options:
1. clean and epoxy the joint together;
2. replace your old sprocket with another one (still available)
3. convert one or both sprocket/mast sets to the stronger latest version.
Between #2 and 3, I think your money is much better spent on the later!
PS -- Matt Miller has posted part numbers here: