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Secrets of Mirage Drive Failure http://www.hobie.com/au/en/forums/viewtopic.php?f=11&t=6261	Page 1 of 2

Author:	AlohaDan [ Fri Feb 23, 2007 1:41 am ]
Post subject:	Secrets of Mirage Drive Failure
Secrets of the Mirage Drive failure. Herein lies a long tale. Will it reveal potential improvements for the Mirage Drive? Correct some problems people have complained about? Can I have renewed faith in bad weather conditions? Only the shadow knows, and maybe those that can wade their way through a very long post. Hopefully that includes some Hobie engineers that are not caught up too much in aloha Friday.. OK here's the truth. I fouled up my Mirage Drive myself. I had had no problems since I replace my failed pedal/crank assembly unit. Last Sunday I launched in the dark off a concrete ramp. I didn't shove off strong enough, and also failed to see a small incoming swell. Pushed back when I jumped in, the Mirage drive clobbered the ramp. MIA CULPA as much as I might want to blame Matt Miller. I quickly found out trying to pedal that the front sail mast of the drive had come lose. Jumped out, pulled the drive, flipped up the rudder, and dragged yak to shore. Got big flashlight, and repair tools out and got to work. Figured I had to disconnect the tension screw. Did that. Got the allen wrench out, backed out the set screw and removed sail from mast. Then only (in the dark with only flashlight), could I see the mast enough to rotate it enough to make sure the flat area would meet the set screw. Note. Solved this problem later. See below. Inserted mast, tighten set screw,mounted sail, reassembled nut & bolt through tension screw, tighten up tension adjustment, back in yak with light dawning off to fish. I'm out a VV FAD 3.5 miles off coast. Front mast comes off . SH^%!! To make a long story short using sail fought small current with sail, while placing mast back on. Got home only doing it twice, jamming mast back into sprocket without taking off tension screw retaining bolt and nut in bobbing sea. Difficult to make sure mast was lined up right. Home I took all apart. First thing I did was put the masts in the vice. Notched them 15/16ths from the end 180 degrees opposite from the flat section. Applied red fingernail polish in grove. Now I could easily line the mast up correctly with the set screw hole. Reassembled. Next day wife and I enjoyed a short training session. No problema. The day after that Wednesday, out to fish. 15 minutes into trip front mast comes off. The hell with it. Perfect conditions 8-10 knot wind off Keauhou, small swells. no bad weather in sight. Sailed most of day. Fishing was poor and did not interfere with fixing front drive mast 4 to 5 times. Biggest fear was dropping allen wrench. Should probably carry 3 of them for safety sake. Finally took the thing off and went in on one sail. You still move pretty fast. So what was wrong? I had not observed anything wrong with the sprocket on the notching assembly day. Closer inspection was needed. My first fix was to try to put plumber's waterproof thread tape on the set screw to keep it from back out. But maybe there was something else. I started with the mast itself. The upper edge of the cut out flat part had been squished into a slope, versus straight up cut. Hard to see in these shots though the dark shadow at the upper end of the flat cut indicates a slope..[click to enlarge]. Here's another view, this time of the set screw that got squished on the left, versus a new one on the right.: So you have a slope on a slope situation. Let's look at the sprocket itself. Note the angle of the set screw hole to the mast hole. It's at about 45 degrees. I have put them together to illustrate. The angle of the set screw against the mast means only one edge of the screw is being retained by the mast edge. With the mast and set screw squished (BY ME NOT HOBIE!!) means the mast would easily slide out under strain (it did this once after reassembling at sea while I was under sail without even pedaling). I suspect this problem is behind anyone experiencing their masts dropping out. So it seems: 1. Your repair kit should contain a spare mast besides the recommended , sprocket, and set screw, or even a couple of each if your touring. 2. Maybe some plumber's tape for the set screw to keep it backing out of the sprocket (haven't tied this yet on failed unit). 3. Hobie might look at getting the flat surface cut in the mast angled so the set screw meets it flat on versus at an angle.. Might lessen effect of any squishing incident. 4. Possibly design in a breaking part when drive hits something, making it easy and cheap to fix. Comments including how to salvage a mast (set scews are too cheap to mess with) ?

Author:	kepnutz [ Fri Feb 23, 2007 8:33 am ]
Post subject:
Hey Aloha Thanks for the detailed post. sorry to hear you had so much trouble with your drives. I would be frustrated too if I were in your flip flops. Knock on wood..I have not had any troubles yet with my drives but I am always taking notes. I was trying to think of different ways to solve the mast/sprocket failure thing and was wondering if a metal T- shaped sleeve were molded deep inside the sprocket mast receptacle to add stregnth then the mast could be drilled and through bolted to the sprocket with a screw and a nylon lock nut or another fastening method (similar to the way the fin adjusting screw is attached) and thereby eliminate any chance of the mast dropping off due to any set screw/mast slot mating failures. Another method could be to thread the end of the mast and then install some type of a threaded insert into the sprocket mast receptacle. (heli-coil style) The mast could then be spun up into the threaded insert in the sprocket like a spark plug in an engine block etc etc. Maybe then there might be less of a chance for a mast mishap. There are many different kinds of threaded inserts available to manufacturers of various designs and materials like stainless steel which could be tried. I realize this might not fix the cracked sprocket issue..but then again maybe it would help reduce that too because another hole would not need to be drilled into the sprocket for the set screw that now holds the mast in place . Just my two cents or some food for thought if you wanted to try your own fix etc etc. Keep the rudder side down -kepnutz-

Author:	mmiller [ Fri Feb 23, 2007 10:19 am ]
Post subject:	Thanks
Thanks Dan. I will forward a link to our engineers. They work 4 - 10s... off on Fridays! Note: I have yet to see failures of sprockets with the set screw located in the proper position (center of the flat area). We are certainly thinking about this issue and thinking of more fool proof solutions.

Author:	Roadrunner [ Fri Feb 23, 2007 12:01 pm ]
Post subject:
Dan, Are you sure you didn't develop a hairline crack along the seam of the mast receiver when the Drive struck the ramp? Those masts should be so snug in the hole that, once properly aligned to the hex screw, there is no room to wiggle or spin; the screw would have to back out to release the mast. If that isn't the case, take another look for a cracked sproket assembly. To pin the mast in the fore and aft direction would weaken the sprocket assembly, as that is the direction of highest stress. Perhaps a small cotter pin through the mast (like the old stainless mast step) from the side would keep the mast retained, even if the sprocket assembly were to crack. Here's a pic of the old set-up showing the cotter pin head going through the side. (Note, you can also see the opposite end of the pin wrapped around the forward edge of the mast step). This set-up has a little wiggle in it, but it hasn't fallen out in the past six years!

Author:	AlohaDan [ Fri Feb 23, 2007 12:49 pm ]
Post subject:
Roadrunner. Nope no crack that I could see with magnifier. But wear at the entrance to the mast hole. Something I ommitted above. It is possible the set screw thread was stripped. Hard to see in there. But I don't think so . For those that don't subscribe to KFS here's an exchange betwen Matt and myself. He seems to have a plausible theory. Matt: With the set screw in place... in the slot at any angle, the mast can not wedge its way out. The Mast hole tolerance will not allow that. The screw has to back out in some way. Now... thinking of this more. Can the set screws be twisted out by the mast rotating a minimal amount under loads? Each stroke slowly ratcheting the screws out? That may be the real culprit! This seems to be an issue on customer installed Turbo Fins and not standard ones so much. Once the screws are removed and re-inserted the threads get worn a little? The screw should not have to be tight. It should just not move. Me: Matt I think you nailed it. After I posted I took out my spare sprocket and inserted the mast. Tighter than a drum to force it in. But the old one there is space around the mast itself at it's entrance into the sprocket hole. Kind of like a tapered cylinder from entrance to the bottom. It's definitely worn larger. So add inspection of mast hole on sprocket to your maintenance checkoff list. This might enable the wobble, ( or be caused by it ?) you described to back the set screw out. It definitely was backing out during the occasions I described. Hence my suggestion on plumbers tape. I'm going to try this with the new sprocket, and will report any further incidents. kepnutz methods are a bit too far advanced for this fumbling repairman. Pending the arrival of a new mast(s) I have also followed yakaholics suggestion and filed the mast indent surface down to a slight angle. BTW did you ever come up with something equivalent to Loctite that won't eat the plastic sprocket? Aloha Dan

Author:	Rnykster [ Fri Feb 23, 2007 10:02 pm ]
Post subject:	shafts
mmiller wrote: We are certainly thinking about this issue and thinking of more fool proof solutions. Let your engineers know some of us would like to see a move back to the metal sprocket/cotter pin design, or even better, some sort of quick lock mechanism that would make it quick and easy to swap out the rubber masts. Maybe a fastener like Shaftloc could be used (provided it could be easily loosened).

Author:	AlohaDan [ Thu Mar 01, 2007 12:20 am ]
Post subject:
Matt Here's a photo I forgot the first time around. Click to enlarge. May help your engineers. The left shows the wear in the mast hole that might have caused the "wobble" and subsequent set screw backout. For the info of others. Here's the new turbo mast cutouts: And one final final. There doesn't appear to be anything wrong with the old sprocket. The mast is only $9.95. I can't see anything wrong by mounting a new mast in the old spocket with a new set screw and using active epoxy to reallyfill up the weared hole and and set screw hole to cement the damn thing in.I mean look at the cost here (relative minor) first avoiding failure. Does epoxy attack thie plastic the sprocket is manufactured with? For a few $ I'm tempted to try it if there is no definitive yes/no from experts here.

Author:	Kauaiguy [ Thu Mar 01, 2007 12:59 pm ]
Post subject:
First of all, I want to thank Dan for turning me to P & K Kayaks and Kelly Harrison. I've been in contact with him since that day and he's answered a lot of questions, and ... I really put him through the paces. Fortunately, he didn't get aggravated with my multitude of questions. Patience is a virtue and he got the sale! With a bit of apprehension, I bit the bullet and ordered the Outback Fisherman (khaki) with the upgraded cart wheel and also a Turbo Fin. I didn't get the Trax Cart because some of the places that I drag the Kayak through have rocks, broken glass and sometimes nails. I didn't want to punch a hole in the tire (I think it's a blow up type tire?), so I opted for the larger plastic type wheels. Don't know if I'm ready to use the Turbo Fins yet because this is my very FIRST experience with a Hobie Kayak ... Never even seen one. But I'm trusting all you folks on this forum and the Fishing Forum who swears by them. I WANT TO GO FISHING with my Kayak! So if all fails ... YOU'RE ALL TO BLAME! NOW FOR THE SCARY PART! I'm been following lots of threads regarding the Mirage Drive failures and now I have this apprehension about going too far out in the ocean to go fishing. I don't want to get stuck 5 miles out and find myself trying to paddle back to the launching area. As the people in Hawaii knows, the weather and ocean currents have a habit of making sudden changes. The ULTIMATE question: Should I purchase a spare Mirage Drive? How about another rudder? Pretty expensive after having spent almost 2 grand! Now I have to spend another $450.00 for a spare Unit when I haven't even seen the Kayak yet? A little PARANOIA? But I'd rather be safe than sorry, or is this an overkill? Please keep in mind that I don't know the first thing about this Kayak and all the repairs and parts names that you folks are throwing about is foreign to me and just goes over my head. It's like me trying to teach you folks the different parts of the inside of a computer? You'd just be sitting there scratching your heads. So, trying to repair something completely new to me would be like trying to repair the inards of your pc for some of you. The beauty about this idea is that if something does break on the Drive, I can throw it in a box and ship it back to Kelly with a note that sez: "IT'S BROKE, PLEASE FIX IT" Mahalo for any of your feedback Tony

Author:	AlohaDan [ Thu Mar 01, 2007 2:23 pm ]
Post subject:
I can share your apprehension. I get out that far most trips. BUT you shouldn't have any problems long as you take care of your drive with proper maintenance. Don't let fear of potential problems deny you the pleasure and benefits of using the Mirage Drive. Rather head any problems off at the pass. 1. Flush the drive with fresh water after usage and spray with WD40. Visually inspect fittings, etc. light lube the chain and idle pulley. So far I have never discovered a problem doing this, nor found any rust, etc. Having said that watch for rough grounding of the fins and mast. IMHO that's where 95% of the trouble comes from. 2. When in shallow water take short strokes, or better yet pull the drive and paddle.. 3. If you launch like I do, pull the yak out to thigh deep water before inserting the fins. Shove one fwd so they are up against the hull before you get in. 4. Carry the emergency spare kit. That would be some basic stuff like the set screw allen wrench, a couple wrenches including the set screws in case you drop one through the well. Some plumbers tape to rap around the set screw. You can at least make an attempt to lock the mast back in. 5. Carry the small vice grips and screw driver to disconnect the tension device.( Assume you ordered turbos.) You can always disconnect the one fin and come in on a single. 6. If you still ground your fins and do any kind of a repair job, use a short trip to test them first. 7. Carry a paddle at all times. Kind of fun to use it for 15-20 minutes to breakup trip monotony. 8. A pedal coming off is not a disaster. It's a minor pain in the arse until you get a new one. also very rarely happens. I only mention it as I experienced it. Note in such circumstances the unit still works. 9. Keep track of what's going on by checking the forums. Matt generally is very good at clearing up problems, giving solutions. Or the actual posters will do so. I repeat: Don't let fear of potential problems deny you the pleasure and benefits of using the Mirage Drive. Remember paddles can break, their screws rust out, and one guy lost his paddle at sea when during a fish fight he dropped it as normal into the water, and the retaining line broke due to rot. The drive is a great invention. But with the paddle, Hobie gives you duality, and if you eventually get the sail, three ways to get home. To answer your question: Should you buy a spare drive? Only you can answer that. So far I have not felt the need to do so. Perhaps I should fishing South Point & Mahukona. Right now that's pretty costly insurance. As for the rudder, not familar with Outback rudder system. If it was an Adventure the $24 for the larger sailing rudder is worth it. For the Outback, maybe someone else can chip in.

Author:	Roadrunner [ Thu Mar 01, 2007 11:49 pm ]
Post subject:
Hi Tony and welcome to the forum. Before you buy anything, I suggest you start out with your new kayak as it comes "out of the box". It will give you a base upon which to make comparisons and future decisions. Second, keep your first trips local until you get familiar with all the parts and comfortable with your boat. You shouldn't have any problems with your equipment, but if you do, that's what paddles are made for. Third, carrying extra parts and tools is a waste of money if you don't know how to install them. If you get to the point where you absolutely have to depend on your drive, I'd recommend the extra drive. If it's too nasty to paddle, you're not in a good position to make repairs at sea. I have enough trouble working on mine in the garage! True, it does cost a lot of $, but it holds its value very well and is worth the investment (if you make that decision). Besides, it's only $350 more than the parts kit! You shouldn't be putting yourself in a situation where you may need one until you gain some experience though, so there's no need to rush into that decision. Finally, be sure to tether all your equipment (paddle, drive, any gear you don't want to lose, especially if you're going out through surf or sailing -- just in case. Realistically, by the time you go further out to sea, you'll have assembled a good emergency kit (search the forum for info), you'll be practiced at capsizing and re-mount and you'll have a good idea of back-up equipment you'll need. Once you try it, you're going to love it! Dan is a great resource for you -- very knowledgeable in these areas (that's how he got to be so old)!

Author:	AlohaDan [ Sat Mar 03, 2007 12:10 am ]
Post subject:
If it's too nasty to paddle, you're not in a good position to make repairs at sea. I have enough trouble working on mine in the garage! This is absolutely correct, as for example when you get into replacing a sprocket. BTW here's a method I fiinally came up with. If it's the rear sprocket you don't have to mess with the font. The front one causes most diffucalties. If the front chain is released for a sprocket change when your ready to lineup release the rear one also. Extend all tension screws so the fins hang clear of the chain. As Matt posted grab the two pedal arms and hold them aligned together. Let the front fin dangle down, pull the idler pully toward the pedal arms. The cable should seat on the pulley if it popped off. You will need to hold the two pedal arms and the idle pully pulled up with ONE hand. Work on it. Not that difficult. Now with the front fin hanging straight down (you can clip a pair of vice grips on the bottom of the fin so it hangs heavy) the sprocket should be lined up on the shaft. Push the chain through the other side and pull it so it engages the sprockets with the fin still hanging vertically. Rotate the one arm so you can push the cable end into it's holder. Add the nut and tighten up a bit. Be sure the fin is still hanging straight down when the pedal arms are aligned. Now do the rear one. Much easier to align it as you have eliminated the idle cable from the equation. Roadrunner will post cable tension measurements & instructions shortly. This ain't easy folks. Took me 4-5 tries to get it right. You learn a lot in the process. Now where is that spare drive I need to carry at Mahukona?

Author:	Rnykster [ Sat Mar 03, 2007 12:33 am ]
Post subject:
AlohaDan wrote: If it's too nasty to paddle, you're not in a good position to make repairs at sea. I have enough trouble working on mine in the garage! This is quite true. That is why I ended up getting a spare drive unit for a quick 60 second swap of drive units. Once back to the safety of land, then repairs can be initiated.

Author:	Apalach [ Sat Mar 03, 2007 7:11 am ]
Post subject:
Hey Tony, A hearty welcome to the Hobie Forum! You will love your new OB and the Mirage Drive--it is a truly brilliant invention and works beautifully as it was designed. Also Amen to Dan and RR's suggestions above, but don't become so paranoid about the reported problems that you fail to enjoy the boat and the drive. I mean, a little paranoia while kayaking is healthy for all of us, but the guys and gals (I know of at least one woman who has reported similar loose fin problems) come under the heading of "Power Users"! Most folks will generally not come close to the amount of use and the same stresses and strains that these folks put on their gear. But, it's always a good idea to carry a Phillips head screwdriver, a Allen wrench (or set) for tightening up a loose fin, a pair of slip-joint pliers, and a small bolt cutter (for cutting and removing embedded fish hooks!). But donâ€™t forget that in an emergency you can always fall back on the tool that all non-Hobie kayakers use routinelyâ€”their paddle! Good luck, and have a blast with your new boatâ€”and I know you will! Best, Dick

Author:	Rnykster [ Tue Mar 06, 2007 10:41 pm ]
Post subject:	Re: Thanks
mmiller wrote: Thanks Dan. I will forward a link to our engineers. They work 4 - 10s... off on Fridays! Ahhhh, 3 days of kayaking every week. Got any job openings?

Author:	AlohaDan [ Tue Mar 06, 2007 11:50 pm ]
Post subject:
Now where is that spare drive I need to carry at Mahukona? I must confess. I have gone rynkster's route. I added up all the spares I have with emegency kits, old fins & masts replaced by turbos, etc. Hell I had half a drive. So ordered the parts so I could carry a complete spare unit. I suspect it was because I got caught in a heavy current this past Sunday and when struggling to get out realized the consequences of either trying a repair or paddling were not good options. My only regret is this has probably added a 6 lb weight addition to my emergency supply locker.

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