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C’mon, let’s get real about replacing SS with plastic
http://www.hobie.com/au/en/forums/viewtopic.php?f=11&t=6271		 Page 1 of 2
Author:  Apalach [ Sun Feb 25, 2007 10:38 am ]
Post subject:  C’mon, let’s get real about replacing SS with plastic
This is a modified version of my 2 June 2006 post in reference to Aloha Dan's (and others) recent posts about problems with the plastic supports for the mast and fins in the newer Mirage Drives, both here and over on KFS.

It is now some 8 months later and the same folks are still having problems with the plastic parts in the newer Mirage Drives. Turns out that I had also noticed what has seemed to me to be a reduction in quality of parts and construction of the Mirage Drives over just the past couple of years. I first noticed what seemed to be a reduction in weight of the Mirage drive between Jan., 2004 when I purchased my new Outback and July, 2005 when I purchased a new Sport for my wife.

Upon closer examination of both Mirage Drives, it became clear that stainless steel parts (including the mast holders and the sprocket and teeth that the chain rides on) of my old 2004 OB drive had been replaced with plastic on the 2005 drive. Here are a few pics for comparison so you can see what I am talking about.

1. Here is a pic of both drives, with the 2004 drive to the left and the 2005 (new) drive at the right, fins up, forward part of drive (Pitot tube speedometer holder) to the left.

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2. If you zoom in on the 2004 drive on the left above, you will note the stainless steel holders for the masts. Note also that the leading edge of each mast is secured by a SS cotter pin--no way the mast can become separated from the drive (unless the cotter pin breaks—unlikely unless it is non-SS and rusts!) since the cotter pin goes all the way thru both the holder and the mast itself. No use of set screws or "set points" anywhere here that are embedded in plastic that can break or become stripped and fail to hold the mast tight.

Image

3. Here is the 2005 (to present) arrangement in which the former SS mast holders have been replaced by plastic, as has the steel sprocket beneath the new sprocket guards. So what we have now are plastic sprocket teeth (like the sprocket teeth on a bicycle pedal assembly) driving the steel chain that operates the fins on the Mirage Drive. Again this seems to be a potential source of trouble as more folks go to the Turbo fins and/or longer-term use of their drives. However, I have to say that I have not heard of any problems or complaints about this as yet (as of Feb., 2007).

Image

4. Here is the opposite side of the newer drives (rear of drive to the left, fins up) showing how the after part of the fins is secured by SS pins that are held in place with a split ring-same as for the 2004 drive. This seems to be a simple, yet functional way to do this. The problem is in the forward attachment of the fins that are now using plastic and a SS screw insert to secure the masts in the newer drives.

Image

SUMMARY
So what is the bottom line to all this? Very simple—and due (IMHO) to not following the precepts of Murphy’s Law, something that I learned about first hand during several years of sea duty in the Western Pacific, courtesy of the U.S. Navy. Murphy’s Law, of course, states in its simplest incarnation that “if there is any possible way something will “screwâ€
Author:  mmiller [ Sun Feb 25, 2007 2:40 pm ]
Post subject:  Reliable?
We are looking at this closely.

Stainless sprockets reliable?

I think this is a misconception about the stainless sprockets. They are problematic. They wear bushings. The chains skipped teeth. The mast holder was loose. The cotter keys would fail from the movement. They couldn't be made tighter and still easy enough to fit the masts and cotter key alignment was critical. They were heavy. Hardly perfect... and a very expensive, difficult part to make for the volume we are building now.

I think we may consider a kit for those that desire stainless parts, but production will likely stay with the lighter and better functioning parts.

There was a big issue with the placement of the mast set screw in the plastic sprocket. That in itself can be blamed for a vast majority of the issues... a very small percentage of production I need to add. This is not a "big" problem.

We are working on it and looking for a way to better lock the Allen screw in place. There are questions about mast slots, worn set screw threads and consistency of the molded parts.
Author:  Rnykster [ Sun Feb 25, 2007 10:47 pm ]
Post subject:  Re: Reliable?
mmiller wrote:
I think this is a misconception about the stainless sprockets. They are problematic....
They also made more noise than the current combination of composite/steel. :)
Author:  Roadrunner [ Mon Feb 26, 2007 12:58 am ]
Post subject: 
[quote="Apalach"]
So what is the bottom line to all this? Very simple—and due (IMHO) to not following the precepts of Murphy’s Law, something that I learned about first hand during several years of sea duty in the Western Pacific, courtesy of the U.S. Navy. Murphy’s Law, of course, states in its simplest incarnation that “if there is any possible way something will “screwâ€
Author:  Billy V [ Thu Mar 01, 2007 1:09 am ]
Post subject: 
I would take a set of Stainless Sprockets, and Mast Supports in a second.
If they are available for purchase, please steer me in the right direction.

In spite of the what Matt has said regarding their wear related problems,
I just do not see how they can wear faster than plastic, or how the plastic that is presently being used is stronger than Stainless Steel.

Is there any New Old Stock available?
or is there a stronger mast support available for purchase?

My Turbo Fin Masts did not fit well from the start.
They did not insert very far into the mast support, and the flat spot on the mast itself needed some modifications (filing to elongate) just to be able to engage the set screws.

Its a malfunction waiting to happen, and I'm not satisfied with the design.
It sure sounds like I got one of those early design mast supports with the production problem.
Author:  Apalach [ Thu Mar 01, 2007 6:47 am ]
Post subject: 
Hey RR,
Good points all. Although I probably didn't make it clear, I'm not really all that concerned about returning to SS sprockets over composite sprockets (that so far have done well). My main point above is that the plastic mast holders with steel set screws to hold the masts in place should have been recognized by a Hobie engineer somewhere along the line as an accident waiting to happen (i.e., re Murphy's Law), even when using the stock fins. I have never been a big fan of set screws anyway, even in SS housings, because with the amount of torque those fins undergo some sort of thru-connection, either with a Cotter pin/key or small machine screw of some sort would seem to be essential, and probably cost-effective to boot.

What I'm not sure Hobie realizes is how many folks there are out there who have never posted, nor complained about the problem online directly, but who are now forced to carry Allen wrenches with them wherever they go (and more than one set too!), because even folks that are not bodybuilder/road cyclist types, but who are using the long Turbo fins, are having the same problem with masts coming loose, or perhaps dropping off part way thru a trip. Since there is no permanent "fix" on the horizon at present in the way of better replacement parts, these folks really have no alternative now but to do field repairs, even when underway, and hope for the best.

I guess I am more sensitive to the issue of plastic parts because I had a similar problem with the original design of the Mirage Drive adjustment levers that used only a pressure arrangement to keep the adjustment pins from coming loose. After a number of underway repairs, I finally had both adjustment levers on my 2004 Mirage Drive fail while out at sea in the open Atlantic off Port Everglades. I have to say that Matt Miller was great about sending me a new set of replacement levers with the new bolting arrangement (even though it now uses a set screw embedded in plastic!). Before receiving the replacement parts, however, I tried my own fix (based on a earlier Hobie design) using a thru-bolted machine screw and Nylock nut. Turns out I am still using that, and have had no problems since--see pic below.

Image

Now--don't get me wrong--carrying a small tool kit is an excellent idea, but being forced to do so because you know (or expect) this loose mast problem to occur before you return, is a real PINTA, and not in keeping with the Hobie way of doing things, and their commitment to quality. I mean we're not talking about Nobel Prize-winning theories here--it is mostly just plain old common sense (SS vs. plastic!) and remembering that Murphy is perched on all our shoulders whenever underway.
Nuff said...
Author:  mmiller [ Thu Mar 01, 2007 10:06 am ]
Post subject:  As I said...
As I said...

We are looking at this closely. The engineers are well aware of the concerns posted here. We'll come up with something.

Quote:
I just do not see how they can wear faster than plastic, or how the plastic that is presently being used is stronger than Stainless Steel.


Wear I refered to is related to the plastic bushings required with the stainless sprockets:

Quote:
They are problematic. They wear bushings.


There has to be a bearing between the stainless sprocket and stainless shaft. They wore rather quickly and required replacement. This is not a problem when using the newer sprockets.
Author:  kepnutz [ Thu Mar 01, 2007 9:02 pm ]
Post subject:  Hey ya going ya'll
I prefer sealed cartridge bearings instead of bushings. Bushings always wear out and break and create a lot of friction. They now make sealed cartridge bearings with ceramic ball bearings that are round to the nth degree. Ceramic material is tougher and harder than steels, and makes for frictionless bearing sets that wont rust corrode or break.

Image

I hate it when sh&t breaks . I always get super mad and look like this little monkey right here...

Image

I would buy the Stainless sprocket bits and mast holder parts too if it meant increased reliability and even better yet if it used ceramic cartridge bearings instead of bushies
-Kepnutz-
Author:  Roadrunner [ Thu Mar 01, 2007 11:04 pm ]
Post subject: 
Hey Kep,

You look a lot younger than I thought, but you're kinda cute for such a shrimp. How do you reach the pedals? :mrgreen:
Author:  Rnykster [ Sat Mar 03, 2007 12:26 am ]
Post subject:  Re: As I said...
mmiller wrote:
There has to be a bearing between the stainless sprocket and stainless shaft. They wore rather quickly and required replacement. This is not a problem when using the newer sprockets.
That is true. Those thin plastic bushings did not last long.
Author:  Rnykster [ Sat Mar 03, 2007 12:28 am ]
Post subject:  Re: Hey ya going ya'll
kepnutz wrote:
...if it meant increased reliability and even better yet if it used ceramic cartridge bearings instead of bushies
Amen!
Author:  FunJax [ Sat Apr 14, 2007 2:28 pm ]
Post subject: 
Is the problem being discussed here?
Used brand new yak less than 15 minutes when I decided to see just how fast it was. It did not last ten good strokes before this happened. Local shop is fixing it and loaned me a drive till it is ready.Image
Author:  Apalach [ Sat Apr 14, 2007 2:55 pm ]
Post subject: 
Hey FunJax,
Sorry your first post is about this problem that has generated a lot of discussion over the past year or so both here and elsewhere. The main difference with your particular experience is that it happened so quickly. Did you happen to have the Turbo fins installed--this seems to be associated with such failures?

Anyway, Hobie has finally decided to provide a "retro" kit that returns to the SS mast holders and SS sprockets that they had installed on all pre-2005 drives. But it will take some months to ramp up a source for the new parts and to find a supplier of the needed materials. If you read my first post here you will see pics of the pre-2005 drive with the SS fittings, as compared with the all-plastic mast holders and sprockets currently being supplied.
Author:  FunJax [ Sat Apr 14, 2007 3:38 pm ]
Post subject: 
Apalach wrote:
Did you happen to have the Turbo fins installed--this seems to be associated with such failures?

Yes, I had the ST fins installed. I got them with the Yak.
Btw, I still love this yak. My other yak is a Prowler 13. It has its advantages but I even enjoyed paddling the Hobie Revo. But I would have rather been pedaling :lol:
Author:  Apalach [ Sun Apr 15, 2007 6:37 pm ]
Post subject: 
Hey Fun,
The ST fins are too new so no one knows if they will cause the same problem, even though It looks like they might have in your case. It so happens that I installed my new ST fins on my pre-2005 drive just this afternoon. The full size Turbos seem to generate so much torque that even those folks who are not road-racing bike jocks may also have problems. The ST fins on the other hand are the same length and just about the same surface area (except at the tip) as the original fins, so I would be surprised if they caused as many problems. We shall see. Just for grins I took some pics comparing the ST fins to the originals. They are quite similar in dimensions, but the fins themselves are of a different chemical composition. Those that have used them have definitely noticed the increased power and speed they can generate--in some cases almost as much as with the long Turbos. Here is the link.

http://www.hobiecat.com/community/viewtopic.php?t=6537
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