Mirage drive failure -- number 3

About four weeks ago, my '06 Mirage drive failed. The right pedal adjustment pin chewed up the drum holes (see pic #1):


Hobie promptly rebuilt the drive, including new crank arms. The first trip on the water, the right crank arm cracked (see pic #2):


Again, Hobie promptly rebuilt the drive, including new drums This time it lasted until the second trip before the right drum failed again. (see pic #3):


I have to wonder if the quality control department went on vacation. I have a pair of six year old drives that run Turbofins and have yet to fail. The drums and crank arms are not a new technology, and there is really no excuse for this kind of failure rate!

I take excellent care of my equipment, so this is not a matter of neglect. I also use Hobie's products without restraint, but am hardly a hard user; many Hobie customers have vastly superior strength and endurance with which to punish equipment!

In an ocean environment or any other body of water, failed equipment can be very costly in terms of property and life. When unexpected winds, storms, currents, unseen hazards and inattentive boaters place strenuous demands on equipment, it should not fail to serve! As a result, "marine grade" equipment should be built to standards of reliability that they can be trusted and depended upon, period. Weight savings and cost savings should not compromise this standard!

This is not a new issue. Rynkster, for one, has been reporting on drive reliability issues for well over a year now: http://www.hobiecat.com/community/viewt ... c&start=15

Whether Hobie needs to insure their vendors are meeting assigned specifications or whether they need to revise these specifications, there should be a margin of error that precludes this kind of failure rate.

Most importantly, while Hobie is looking for solutions, they should not continue to produce and sell unreliable equipment. Hobie's warranty is second to none, but cannot substitute for dependability when you need it!

Perhaps a thin plate of Stainless Steel placed over the sides of the drum would provide a stronger point for pin engagement.
-It wouldn't take much to prevent that plastic from sheering.

Thats what I would do,, but hey I'm not a Hobie engineer.

I'll keep a close eye on mine.

Marshall's Industrial Hardware on Production Ave. in Miramar is where I go for most of my fabrication need.

Also.

Industrial Metal Supply in Kearny Mesa for sheet metal.
----------------------------------------------------------------------

Do Hobie Engineers read this forum to keep abreast of their products performance??

Hi-Ya Roadie..
This is a most disturbing situation to read about. Sorry to hear about the frustrating failures with your mirage drive. This would be a total factory recall situation if say the transmissions on a new model 2006 automobile were failing right and left I will have to re-inspect my 2006 drives first thing this morning from yesterdays excursion.

Did you notice any unusual noises or vibrations while pedaling? Did it feel different to you in any way out on the water or was this discovered at the journeys end? If so please describe any possible "warning" signs one might notice while underway, if a drive was being stressed and/or starting to fail.

Perhaps the Hobie R&D team needs to install a replaceable delrin bushing in these holes to absorb shock and prevent fatigue of the drum and/or use two sets of holes and pins to spread the load or some other method and then run " failure" tests on a lab machine over so many cycles in order to finally solve these drive failures. Im not a structural engineer by any stretch but something needs to be done as we are all at risk it seems.

From everything I've read in this forum, Hobie does a pretty fair job of warranty repair on their products. I often say "You can break anything if you do it right" yet your failure and Rynkster's, under normal use, is most unsettling to us all , as we have seen on this site how well you guys take care of your Hobie kayaks.What do you think is a possible contributing cause of these events ? Do you think the pin is wearing the hole larger and getting sloppy then being pounded into the drum material with each pedal stroke to cause the damage? Could it be the just difference in material hardness between the drums and pins or less than ideal machining of the pin holes that create this situation?

I whole heartedly agree that this safety issue needs to be resolved immediately. More than a few of us are using these drives many miles out on open waters and far from shore on a regular basis and should not have to worry about our transmisson's failing. I doubt any of us here would ever own a car that , when going for a Sunday drive or long trip, it was deemed necessary to put a spare transsmission or rebuild parts and tools in one's trunk just to be sure of completing the intended round trip

I for one will be interested in hearing about any further developments of your drive situation and look forward to any concrete solutions on this issue from Hobie representatives. Thank you and Rynkster for the "heads up" and if possible, please keep us posted of any new factory response, corrections or changes to our Mirage drive system's
-kepnutz-

In all cases, the failure is without warning. It seems to be caused by excessive gap between the crank arm and the drum (preventing the adjustment pin to seat fully) and pedal flexing under extreme use, thereby extracting the pin even further to where there is insufficient drum remaining to hold it in. Both the previous pictures show this to be about 1/8 inch from the edge of the drum.

The next picture illustrates the arm-drum gap (the failed side, now bolted, had a slightly larger gap).


by way of contrast, the next picture shows the older drive drum and crank arm. Notice how close the gap is between them? Also, you can see the adjustment pin on the right side, going all the way through the drum. With the solid crank arms, there is virtually no flexing; that drive is properly built and will not have a drum failure!


What is upsetting to me is, Hobie obviously knows what it takes to build them properly, and has done so in the past. Where are their priorities today, where it is OK to sacrifice this kind of dependability on a bottom line piece of equipment? This is not a seat-back coin purse or water bottle!

The next generation drum that Matt mentioned may close this gap some, but does not address crank arm flex, which is a major part of the problem. In the mean time, These weakened drives are passing the quality assurance process and continue to be sold.

I'm a huge Hobie fan, but after three failures in quick succession, I see this, not as an annoyance, but as a serious problem, and am concerned that in an unforgiving sea, this could cost somebody dearly.

What is the crank arm made of?

_________________
Waterman at Work - Kayak Fishing Photos, Video,Kayak Rigging - Blog

Thank you for the detailed explanation and pictures. I see what you mean by the gap and understand how this could cause the pin to skip out under load/flex and thus tear up the drum. This does appear to me to be a real problem issue. The mirage drive is the heart and soul of these kayaks and if these are not proving to be a reliable build then I think it needs to be addressed by the manufacturer before someone is put into difficulty. On the positive side it sounds like Hobie has been trying to respond by attempting to repair your drives under warranty even if the results have been unsuccessful so far. I will be paying close attention to any solutions offered by Hobie and eagerly await any reply from Matt on this matter. Better to have it sorted out now rather than say 8 miles out in rough water. Do you think we should cease using these mirage systems until a correction is offered up? Would you have any advice as to what kind of temporary fix should be used if heading out into open water? Keep us posted if you hear anything.
-kepnutz-

Appears to be an anodized aluminum extrusion. The old ones look like anodized aluminum bar stock.

No question about it, Hobie has been super at handling these warranty repairs. They have handled these problems immediately and have replaced any parts that were suspect in any way.


Not at all! Forewarned is forearmed though, so knowing your equipment's limitations is always important. Kep, you could probably pop one of these drums, so just don't max it in a tight situation. If you're concerned, you could bolt the arms up for now.

In my case, I was riding wakes, with sprint speed during each of the three failures. On yesterday's failure I was going 8.7 MPH (GPS) when it popped. I lost control of the boat, got swamped and just about capsized. This is not an everyday occurrence for most users. But it could just as easily be someone scrambling to get out of the way of a daydreaming yachtsman on the ocean (this happened to me once with a freighter -- talk about adrenalin!).

Hey Roadie
Sounds like I better be more careful out there in the big waters. When Mrs Kep is out with me we usually do a steady cadence with a minimum of sprints. Yesterday we went 7.58 miles in 1hr 54 min with a 4mph average and a max of 6.4mph (GPS). However we did forget to bring a paddle as we were in a rush to load up, drive out, and get a few strokes in before the end of the day We would have been in some trouble if we had a drive failure of some sort. With our tandem, at least there are two drive units on board which helps in the event of a mishap.

When I take my friends out we often go to the bigger lakes and chase boat wakes into the lagoons, so I will have to take this information and perhaps do the bolt thing and hope the arms do not become a problem.

I was thinking that perhaps if the pins stuck out just a bit more and had an internal spring loaded detent ball that would snap out on the back side like the hex socket drives in my tool kit or something similar,that this might solve the pin skip issue and still allow for a quick leg length adjustment. Another simpler method might be to drill a small hole in a longer pin and then insert a "hitch pin clip" into the hole of the pin on the back side of the drum. This could also have a small wire "keep" attached so the clip would not get dropped or lost etc. It would have to be developed a bit in the lab but it seems like a potential fix to the skip problem without having to bolt.

As for the crank arms I would prefer the extra weight of solid bar stock in favor of greater reliability. One other solution might be to make the arms out of carbon fiber like the cranks on my bicycle. Although a more expensive solution, carbon fiber bike cranks have proven to be both lighter and stronger than aluminum and steel and could be offered as a high performance upgrade similar to carbon/kevlar kayak paddles and boats etc. Then again solid bar stock would still work well.

At any rate thanks again for all your photos and the excellent debriefing on your drive failures and solutions. You are one of the resident genius problem solvers around here and it should benefit all concerned to digest any of your current developments. Please keep us in the loop if anything new crops up or you get any fresh ideas that we could all adopt.
-kepnutz-

Heres some more on my "Mirage Drive Retrofit Idea"
Yes, thats sarcasm.

However, in support and interest of Hobie's product development I want to share my idea in hopes of a resolution to drive drum issues.
A picture is worth a thousand words, heres a couple for you Hobie engineers to review.
--Talk amongst yourselves.

My Sheer Shield.



------------------------------------------------------------------------------------
Hey, there could be some money in this High Performance and Upgrade Market.

Hey ya going B.V.
Your stainless sheet would protect the holes in the drum and one of these clip things might prevent the pin from flexing out of the adjustment holes If a longer adjustment pin reached through the crank arm and drum and then and got clipped to the back side of each drum then maybe pins will stay in place better. If we all pitch in we can sort this thing out. Nice work .
-Kepnutz-

RR,
It looks like the failure happened on the starboard side. Do you think the broken pedal bolt may have generated extra torgue on the crank arm?

Oops, never mind, I just realized your drive probs occurred before the pedal bolt.. "never mind"

Certainly we are working hard on a new drum that will help if not completely solve this issue. Not that the issue is that widely reported though. It appears that the current drums may have some warp-age at times, flex maybe. Same drums we have been using all along since going to the plastic years ago. Perhaps the pedal shaft is twisting the adjustment pins out of the drum? You have to be sure the pins are fully seating into the adjustment holes in the drum. I have seen some misalignment that prevents the adjustment pins from fully seating.

In any case, I will forward the forum comments to engineering.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

I took my kayak out yesterday for a pedal in Mission Bay. I was only cruising at 3-3.5 mph as measured on the speedo tube. No sprinting, or heavy pedaling, I had the Turbo Fins installed and was just tuning them a bit. (I had the yak loaded down with a full bait tank, beach wheels, full dry bag, fishing gear, the whole fishing package.)

What I noticed was the "pedals shafts twisting" as Matt had mentioned.
-I had some tools with me and tightened the 14 mm nut, and bolts that affix the pedal shafts to the drum and watched for more flex.

I do believe the pedal shaft will continue to flex in its current hollow configuration. Perhaps through bolting the pin area with washers will help the pin from slipping out, but it may also introduce more psi than the drum holes could take, and that may cause the drum to crack.

I'm sure the next generation will be better in every way. :thumbs up:
--------------------------------------------------------------------------------
Its good to see this company continue to strive to make their products better.

-They make nice stuff...
Which is what I thought when I bought this, 22+ years ago.
BTW (Its Still "In Service")

I had the same problem with my drive. Just after installing my new turbo fins I had pin hole failure on the drum as well. I can see why ,the added torque from the larger fins flex the drum more causing the pins to slip out.You can clearly see that the pins are to short and do not extend far enough into the drum.I have made new stainless steel pins for the drums. They were easy to make and the look just like the olds ones but longer. The trick is make them longer, but not so long they won't release to the other holes. You can increase them almost a 1/4 of an inch or more . The most incredible thing is I was able to keep my damaged drum. The pins make a huge difference and will save your existing drums from the problem. If anyone would like pictures let me know.
The two pictures below show the new pins in . They stick through the holes and not flush making them very safe from slipping out. The beauty is you can still operate it the same way and change to a different hole if wish be.Enjoy !


The bottom one is the new one I made that is slightly longer .You can adjust the length to the maximum length for each side.Try to make them as long as possible,but still be able to slide to the next position.

I would like to see pictures newyaker.