Mirage drive repair

I am working on an article in which a guy replaced his drive arms with those from the first generation drive.  Those parts are still available from Hobie as part number 81105001 for right and 81100001 for left.  They are made of solid aluminum stock!  Supposedly the drive arms are interchangeable between drive generation (not 100% confirmed by me).  Note that they are threaded (same thread as bike pedals) so the pedals are different.  But this might be an option for those of you looking for stronger drive arms.

-Allen

Kinda like this?


Except mine are not made from the cheap ass pot aluminum Hobie uses. I made these from solid 7075 T-651 aircraft grade aluminum.

And I can make them to any length. Initial tests are very positive on the longer arms for tall individuals in PA's

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I am working on an article in which a guy replaced his drive arms with those from the first generation drive.  Those parts are still available from Hobie as part number 81105001 for right and 81100001 for left.  They are made of solid aluminum stock!  Supposedly the drive arms are interchangeable between drive generation (not 100% confirmed by me).  Note that they are threaded (same thread as bike pedals) so the pedals are different.  But this might be an option for those of you looking for stronger drive arms.

-Allen

Might wanna talk to FG.  Check out these beauts...



better, faster, stronger, longer!  It's like adding another gear to the drive.

Nice work Bill.  So you went with solid aluminum instead of stainless tubes?  Did you still drill an adjustment hole, or did you figure out some way to put it "outside".

How much longer did you make them?

And have you had any freakishly tall pedalers test it out?

-Allen

better, faster, stronger, longer!  It's like adding another gear to the drive.

Well, longer at least!  I'd really like to see sumpNZ run the numbers.  He did so for the solid stock vs. the tube.  But the increased length now puts more force at the adjust hole, right?  I wonder what the net net is in terms of overall strength relative the the shorter tubes.

-Allen

Now we'll need solid aluminum drums. 

I went with solid bar because it was easier to find than thick wall stainless tubing. This aluminium is as strong as some stainless alloys and harder than many mild steels.
I left the adjustment hole in place for a straight stock drop in replacement.
They are currently in the testing phase. I made mine stock length and Rory's set 2" longer.
My stock length arms and pedals are only 5 ounces heavier than stock.

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For longer legs like Rory and all, I would suggest cutting another set of solid aluminum square bars a bit longer and put a smooth radius 10-15 degree bend in it just above where the plastic adjustment lever is at it's highest point and aimed towards the front of the kayak.  This will allow you to run the pedals further forward, and/or even higher to avoid hitting the kayak.

Also, if quick adjustments for different  leg lengths is not needed, remove the squeeze handle, and the adjusting pin.  Run a stainless bolt through from the inside and use a good Nyloc nut on the outside.  The head should be ground down slightly to reduce hitting the bolt head on the opposite side.  Start with a longer bolt with at least a 1.25" shank where the threads don't start until completely outside off the solid bar.  Add a washer as needed.  Cut off extra length of bolt.  Lube the bolt shank with waterproof grease or anti-seize to reduce the dissimilar metals from reacting with each other.   

The bolt through method will remove unnecessary slop that may very well have caused work hardening and eventual cracking of the aluminum tube in the Hobie bars.

better, faster, stronger, longer!  It's like adding another gear to the drive.

Well, longer at least!  I'd really like to see sumpNZ run the numbers.  He did so for the solid stock vs. the tube.  But the increased length now puts more force at the adjust hole, right?  I wonder what the net net is in terms of overall strength relative the the shorter tubes.

-Allen

I'd be happy to do that.  Just need all the details of the design.  And a little spare time.  Going tuna fishing this weekend though (weather permitting).

better, faster, stronger, longer!  It's like adding another gear to the drive.

Well, longer at least!  I'd really like to see sumpNZ run the numbers.  He did so for the solid stock vs. the tube.  But the increased length now puts more force at the adjust hole, right?  I wonder what the net net is in terms of overall strength relative the the shorter tubes.

-Allen

I'd be happy to do that.  Just need all the details of the design.  And a little spare time.  Going tuna fishing this weekend though (weather permitting).

How about running longer solid square aluminum bar that Fungunnin used, add a 10-20 degree smooth arch in the bar from end to end. Put the bar in the number 6 position and clamp the bar in place with U bolts (like used in the original field fix). 
Ultimately look for square stainless U bolts, but for testing purposes, the round galvanized/zinc coated ones will do the trick. 

This will eliminate the internal weak point in the bar/tube where the adjuster goes, allows two points of clamping contact to the plastic drum instead of just one.  The bend forward and longer length puts the pedals up and forward for long leggers.

Plus that would eliminate one more point of machining.
I don't have access to a bender and this shit is REALLY hard .... Now to find stainless C bolts.

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Give me a drawing (can be by hand certainly) with as much detail, especially dimensions and materials, as possible.  I'll work up a durability analysis.  PM or email (sumpnz@yahoo.com) will be fine.

Plus that would eliminate one more point of machining.
I don't have access to a bender and this shit is REALLY hard .... Now to find stainless C bolts.

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You should have a metal shop in your area that could bend it up for ya. 
On a side note; I think since you wouldn't need the adjustment hole (weak point), then you could probably get away with .120" wall stainless tube. 

I have a bender that could bend that tube easily, however I don't have that particular die set needed.  The 3/4" square die sets are $215-$230. 

If there was enough interest in these arms where it would be cost effective for me to bend up a bunch, I would spring for the die set. 
See if you can source the stainless U bolts and maybe we could get something rolling?

.120 wall 3/4 stainless is not a common size. 1" ... No problem just not thick wall 3/4.

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.120 wall 3/4 stainless is not a common size. 1" ... No problem just not thick wall 3/4.

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I see that 304 SS 3/4" x .120" wall (11 gauge) square tube is available at the MetalsDepot.com, Tottentubes.com, and Speedymetals.com with just a quick Google.   

If you were searching for 316, then yes it is a rare commodity.  304 is stronger than 316, and is widely used in the marine environment for fasteners and strong structures. A normal fresh water rinse after a day in the salt will keep the tubes happy for years to come.

With that said, one shouldn't have too much trouble getting 304 .120" (11 gauge) ordered through a local metal shop. 
Surf your local Yellow pages for metal shops that you can visit or order through.
If I'm not busy tomorrow I'll hit up the two local shops that I frequent and see what they can get in.