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| Tensioning Problms with Mirage Drive http://www.hobie.com/au/en/forums/viewtopic.php?f=11&t=6435 |
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| Author: | AlohaDan [ Thu Mar 29, 2007 12:24 pm ] |
| Post subject: | Tensioning Problms with Mirage Drive |
Yep I saw roadrunners great pics on the previous thread. He had actually sent me some numbers before on what tension I should have. The pics make evrything very clear. But here's a problem I can't solve. I'm building a new drive unit from emergency spare parts and some additional ones I ordered. The problem is I can't get the idle cable and font sproket drive cable into their proper positions with any slack. I can barely get enough of the threaded swedges far enough into their holes to have the retaining nuts grab 2-3 threads at the most. Even with the nuts barely engaged evrything is way too tight. I have no problem with the rear cable. I have taken apart the idle cable on the old drive to make sure I then did it right with the new one. I then remounted it, and the front sproket chain/cable. No problema tensioing and there were plenty of extra threads from the threaded swedges sticking over the top of the nuts as in roadrunners pics. On the new drive when I first placed the idle cable I rotated the spine as high up as I could on the drum assembly to keep the cable around the pulley correctly while putting the retaining nut on. Was able to get the nut on OK, but slacked it off to only 2-3 threads due to problems with the front sprocket cable/chain which requires this spline position or higher to be able to correctly place the sprocket chain/cable. I did this with the pedal assemblies bungied together. The sprocket was then correctly lined up to recieve the chain/cable. I had extreme dificulty even with the spine rotated as high as I could. It really needed another 1/4 inch or so. As stated above I was barely able to get 2-3 threads engaged by the nuts. Tension was way too tight at at this stage. No slack at all in the idle cable, and the sprocket chain/cable wasn't much better. I am pretty sure I assembled the drive correctly. But.... what is wrong here? Anyone have any ideas? Mahalo for any advice. Dan |
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| Author: | AlohaDan [ Thu Mar 29, 2007 2:47 pm ] |
| Post subject: | |
Here's a pic showing the old and new drive (on the left). 
Click on the image and you can really blow it up to see the problem. Note on the old drive on the right the red nail polish on the idle cable nut. If you look at the new drive on the left you can see the cable is no way near inserted into it's receptacle hole as the cable on the old cable. Likewise on the sprocket chain cable. The new drive's cable barely reaches through it's receptacle. |
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| Author: | Roadrunner [ Thu Mar 29, 2007 3:55 pm ] |
| Post subject: | |
Hi Dan, Perhaps your cables shrunk in all that humidity? 
It's hard to know without seeing the whole unit, but first check that your front chain is tightly seated on the sprocket. The center cog on that sprocket is thick and will sometimes hold the chain out from fully seating, though not necessarily easy to see.. Second, unbind the crank arms temporarily. If tightly bound, it can affect the way your drums sit. I'll go out and look at mine to see if I get any more inspirations. In the meantime, let us know if you get it solved! 
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| Author: | Roadrunner [ Thu Mar 29, 2007 4:06 pm ] |
| Post subject: | |
Make sure your idler pulley isn't mounted backwards. That could be the problem. If not, loosten or unfasten your rear chain cable and restart from the front.
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| Author: | Roadrunner [ Thu Mar 29, 2007 4:16 pm ] |
| Post subject: | |
Looking again at the picture, it appears that your idler pulley is OK, but it looks like your front chain is not fully seated on its sprocket (the chain/cable swedge looks lower than the other drive). Check the rear chain-sprocket seat also. Give some slack on the rear cable and retry your idler cable. Hopefully it should work now.
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| Author: | AlohaDan [ Thu Mar 29, 2007 5:20 pm ] |
| Post subject: | |
rr Thanks for the analysis so far. As you saw the idle pulley was installed correctly. Also there is no chain/cable on for the rear sprocket. I left it of for now. From past experience that one is a piece of cake once the front is taken careof. However, your: A. it looks like your front chain is not fully seated on its sprocket. Not so. It is. I made great effort to find the center sproket, then laid the center chain hole right over it so it went in.... but your: B. (the chain/cable swedge looks lower than the other drive) is absolutely correct. It's the problem driving me nuts. I can't get the swedge in there to grab more than a couple of threads with the nut. Then when I tighten the nut down to try and pull it in at least to seat the nut 95% to the nylon locking section, it makes the idle cable or sprocket chain/cable too tight. I'm hoping Matt reads this and asks a shop assembler what the story is. In the meantime if you, or someone else has another idea, please let me know. Mahalo Dan |
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| Author: | New2Yak [ Thu Mar 29, 2007 9:30 pm ] |
| Post subject: | |
This is just a wild guess, but did you pull both cable's off and compare their lengths? Maybe the new cable was just made too short. I've stared at your photo for some time, and can't think of anything else. |
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| Author: | mmiller [ Fri Mar 30, 2007 9:13 am ] |
| Post subject: | Idler cable |
There are different length idler cables. Current is 14 1/4" Old is 14 3/4" Should be measured from tip to tip. |
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| Author: | AlohaDan [ Fri Mar 30, 2007 11:35 am ] |
| Post subject: | |
Nope! All chain/cables are the correct length and I have the correct idle cable. |
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| Author: | mmiller [ Fri Mar 30, 2007 2:13 pm ] |
| Post subject: | Are the stud ends the same length? |
Are the stud ends the same length? Maybe not allowing it to wrap around the corner properly? Looks like the stud is proped up on something on the drum. Is that something that we trim off here? |
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| Author: | AlohaDan [ Fri Mar 30, 2007 3:20 pm ] |
| Post subject: | |
Are the stud ends the same length? Yes Maybe not allowing it to wrap around the corner properly? Looking at the old drive the swag is still supported by the curved portion of the drum. Don't think that's it. Looks like the stud is proped up on something on the drum. Is that something that we trim off here? Don't think so. Old and new drums have same caliper measurements.(BTW anything you want me to measure? My instrument is good to .01") A symptom, not a cause, post coming shortly. |
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| Author: | AlohaDan [ Fri Mar 30, 2007 3:35 pm ] |
| Post subject: | |
Here's something else that is happening. Maybe related to sprocket. Note that I'm doing this with no fins mounted, but that shouldn't make a difference. Also that his is with the cables fairly tight and the nuts only half engaged. I hold the drive by the pedal arms, front up so I'm looking at the idle pulley and pitot hole. Rotate the drive up so I'm still looking at idle puley, but now am virtually sighting down the length of the sprocket. The center sprocket arm is vertical and the two pedal arms are parallel and adjacent each other (neutral). I can easily see the chain riding on the sproket if I move the arms. I move the pedal arms so the sprocket rotated 90 degrees either side , back and forth. Chain moves OK. Now I move the arms further so the sprocket goes into a "stop". The stop being the sprocket rotating so far the mast holder portion hits up against the spine. This occurs at approximatel 120 degree rotation of the sproket from it's centerline. Note with fins attached and mounted in the yak I doubt if you can get this far without the fins bumping up against the hull. I'm just looking for why the short cable/tensioining problem occurs and causes. On rotation by the sproket just as it approaches the stop, the spocket arm next to the center sprocket arm pops out with a large click. It re-engages as I move the arms in the other direction, again with a click. Other than this, the chain seems to move smoothly if I don't rotate into the stop. FYI have disassembled and re-assembled several times including spare drive. I also disasembled the pedal arms and swapped durms left to right, and vice versa. Drum measurements appear to be identical but I did not do a 100% check. |
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| Author: | Roadrunner [ Fri Mar 30, 2007 4:29 pm ] |
| Post subject: | |
AlohaDan wrote: Here's something else that is happening. Maybe related to sprocket.
On rotation by the sprockets just as it approaches the stop, the sprocket arm next to the center sprocket arm pops out with a large click. It re-engages as I move the arms in the other direction, again with a click. Other than this, the chain seems to move smoothly if I don't rotate into the stop. I think that's the center sprocket cog snapping in and out of the chain at full deflection -- it's normal. Tell me, have you tried assembling the chains without the idler pulley attached? Something Matt said about the two idler pulley cable lengths would make me curious. If you were out at sea making this change, you'd probably be getting mighty hungry by now! 
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| Author: | AlohaDan [ Fri Mar 30, 2007 5:52 pm ] |
| Post subject: | |
With the curents around here I would be half way to the Marquessas. I wonder if I would get tired of eating mahi mahi? 
I tried a "bad part" ID. I knew Old Drum Right = Good = ODR Old Drum Left = Good = ODL Old spine = Good = OS New Drum Right = ? = NDR New Drum Left = ? = NDL New spline = ? = NS Wala so far: a. ODR + ODL + NS = good!! So NS = good BTW for the above the click at the stop is gone. b. NDR + NDL + OS = Bad Now testing to see if it's NDR or NDL. I'll match -em each with an old drum. I hope Hobie appreciates my 20+ hours of QC. |
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| Author: | AlohaDan [ Fri Mar 30, 2007 6:25 pm ] |
| Post subject: | |
Well after three days I found the culprit. Now what? Matt see below. OK NS + ODR + NDL = Good NDL is therefore OK However: OS + NDR + ODL = Bad Culprit is NDR Visually I can see nothing wrong. But with this bugger you end up with the situation in the photographs. Absolute over tension to even get enough thread in the nuts for them to hold. Not to mention wrestling with it is worse than handling to alligators. So I just received this part. Matt do I return it to the dealer for a new one, or do you want your QC guys to have it? If so give me where to send it, and forward a replacement to me. If you want the exchange e-mail me at: [email protected] To all others. Mahalo nui for chipping in on the advice. Aloha Dan |
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