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 Post subject: pedal arm broken
PostPosted: Sat Jun 16, 2012 12:30 am 
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Joined: Sat Jun 16, 2012 12:16 am
Posts: 3
Hello,
we have in our country, several friends who have suffered a broken arm bracket after a turbo kit utilisatoin with 2 to 4 years;
is what you know of any similar events in your country

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With normal maintenance, rinsing with each release, the incident occurred without warning (visible cracks)
do you have advice for us to reduce the risk?


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 Post subject: Re: pedal arm broken
PostPosted: Tue Jun 19, 2012 9:16 pm 
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Joined: Sat Nov 12, 2005 10:46 pm
Posts: 2409
Location: Escondido
Penkayak, welcome to the forum.I haven't seen a broken crank arm in a few years -- it seems to be uncommon around here.

There appears to be quite a bit of corrosion around the lower broken crank arm hole. Does your drum have a weep hole in the bottom. If not, it might be a good idea to drill a small one so salt water can not sit in that pocket. Even if you rinse and drain it, there is a residual in the hollow pedal arm shaft that drains back into that area.

Years ago Hobie used solid billet aluminum crank arms. They are still listed in the catalog (81105001 crank arm right, threaded; and 81100001 crank arm left threaded) -- they are very strong and you'll never break them, but they require standard bicycle screw-on pedals (left and right hand threads) which you'll have to supply. They should be otherwise interchangeable with the current crank arms. 8)
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 Post subject: Re: pedal arm broken
PostPosted: Wed Jun 20, 2012 10:04 pm 
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Joined: Sat Jun 16, 2012 12:16 am
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Roadrunner wrote:
Penkayak, welcome to the forum.I haven't seen a broken crank arm in a few years -- it seems to be uncommon around here.

There appears to be quite a bit of corrosion around the lower broken crank arm hole. Does your drum have a weep hole in the bottom. If not, it might be a good idea to drill a small one so salt water can not sit in that pocket. Even if you rinse and drain it, there is a residual in the hollow pedal arm shaft that drains back into that area.

Years ago Hobie used solid billet aluminum crank arms. They are still listed in the catalog (81105001 crank arm right, threaded; and 81100001 crank arm left threaded) -- they are very strong and you'll never break them, but they require standard bicycle screw-on pedals (left and right hand threads) which you'll have to supply. They should be otherwise interchangeable with the current crank arms. 8)
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thank you advice Roadrunner
or drill the hole without weakening the drum


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 Post subject: Re: pedal arm broken
PostPosted: Fri Jun 22, 2012 12:32 pm 
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Joined: Sun Aug 12, 2007 5:17 pm
Posts: 532
Location: Auckland NZ
I broke a crank arm and now carry a spare on longer trips.

The breakage was on a second hand drive I bought. I do not think that the drive had been particularly well cared-for: there was certainly more corrosion on either of my other drives and I seem to remember that the blanking plug on the top of the arm (to stop water coming in the end) was missing.

It started twisting noticeably before it finally broke in the middle across the adjustment holes like one of your photos.

I think the answer is that the arms do wear and break, especially if not cared for properly and used hard (I would not class myself as a particularly light user) so keep the plugs in place, rinse well after use in salt water and consider stocking a spare. The good thing is that spares are available and replacement is straightforward.

BTW, where is your country?


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 Post subject: Re: pedal arm broken
PostPosted: Fri Jun 22, 2012 3:26 pm 
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Joined: Thu Feb 23, 2012 5:03 pm
Posts: 56
Location: Seattle, WA
Roadrunner wrote:
Years ago Hobie used solid billet aluminum crank arms. They are still listed in the catalog (81105001 crank arm right, threaded; and 81100001 crank arm left threaded) -- they are very strong and you'll never break them, but they require standard bicycle screw-on pedals (left and right hand threads) which you'll have to supply. They should be otherwise interchangeable with the current crank arms. 8)
Image


Nice! Had no idea and have been thinking about fabricating this very thing. Do they weigh more?

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 Post subject: Re: pedal arm broken
PostPosted: Fri Jun 22, 2012 4:14 pm 
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Joined: Fri Sep 12, 2008 12:07 pm
Posts: 16
Penkayak, Your drive shows corosion. This can be prevented with a good spray lubricant applied weekly. WD40 works fine but I prefer any of the new waterproof silicones now on the market. Any automotive store should have them. I have drives over 10 years old that have zero corosion but get sprayed all the time.After four years of use however you might excpect something to give.


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 Post subject: Re: pedal arm broken
PostPosted: Sat Jun 23, 2012 7:10 am 
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Joined: Sat Jun 16, 2012 12:16 am
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for broken arms 2 years of routine maintenance
rinsing at each exit and W40 on the chains and axes.

for my arms (one broken in the middle and one at the bottom) 4 years with the same maintenance and disassembly for re-painting
disassembly of the cap there was a higher accumulation of oxidation

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 Post subject: Re: pedal arm broken
PostPosted: Sat Jun 23, 2012 3:52 pm 
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Joined: Sat Nov 12, 2005 10:46 pm
Posts: 2409
Location: Escondido
The crank arm corrosion is a byproduct of galvanic action where two different metals are touching in the presence of moisture. Salt water accelerates the process. In this case where you have stainless steel and aluminum, the aluminum corrodes.

The best way to protect the aluminum is by adding a third metal such as zinc. The zinc acts as a "sacrificial annode" and will corode instead of the aluminum. Fortunately zinc is inexpensive and very common. In fact, any 1983 and newer U S cent is 97.5% zinc.

Look for a worn penny where the copper cladding is mostly worn off,
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bend it to fit in your pedal shaft and slide it in.
Image Image

BTW, the crank arms are now anodized for better durability. They used to be E coated (painted). Between the improved crank arms and one penny fix (check it annually for replacement), you shouldn't have any further problems. 8)

PS. I checked out the drums. They do have a drain hole:
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But the hole doesn't drain completely (residual water is highlighted in pink):
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So it is best to rinse turning the Drive upside down a few times to purge the salt water (which also leaks into the shaft of the crank arms).


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 Post subject: Re: pedal arm broken
PostPosted: Sat Jun 23, 2012 4:05 pm 
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Joined: Sat Nov 12, 2005 10:46 pm
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Location: Escondido
cryder wrote:
Roadrunner wrote:
Image


Nice! Had no idea and have been thinking about fabricating this very thing. Do they weigh more?
Yes, they are quite a bit heavier. So are the bicycle pedals you'll be using. The original style Drives weighed significantly more than the current versions. I don't see it as especially problematic though -- they all sink! 8)


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