Hey everyone – Greg here. I’m about 10 km North of Pentincton on Okanagan lake right now with Ken taking a turn on the pedals. I’m in the cabin and decided to write a blog post and send it via satellite phone.
So – why are we here and not on the Pacific around Vancouver Island? You read Jordans account of the drive leg failure from yesterdays blog post. The next morning, my buddy and ex-kayak guide Bryon Howard used his kayak to tow us across the straight from Denman island back to Vancouver Island where Ken was waiting at the boat launch with the Suburban. It must have taken a couple of hours to tow us back with me standing up through the hatch with a paddle helping out.
That night in a hotel room in Nanaimo, Ken and Jordan pulled the lower gear box apart and found the problem – it was a small roll pin used to secure the pinion gear to the shaft that had sheared off when Jordan pedaled into reverse near the Ferrie. I contacted George from MitrPak and he advised us to replace that pin with a solid pin, so Ken “MacGyver” Fortney found a drill bit that fit the hole, and he went to work fixing the gear box during our drive back to Calgary in the passenger seat of the Suburban – don’t try this at home kids!
I figured that we might as well do something to salvage this trip, so I asked Ken if he would be into spending a few days on Okanagan lake in Penticton testing out the drive leg fix. He was into it, so here we are!
We are staying at the Lakeside Resort in Penticton and the public marina and boat launch is right next door. I launched WiTHiN (single handedly) yesterday afternoon while Ken re-assembled the drive leg in the hotel room. We got the Drive leg in, and I set out past the break-water at the marina.
Holy SMOKES! The lake just past the break water was crazy! The wind had picked up substantially (didn’t really notice it in the protected marina area), and now the waves which travel about 140 km down the lake from North to South were 4 feet and breaking. I was a bit nervous, but that’s what this baby was built for, so I went for it. It was one wild ride – probably nothing compared to what I might (or have) experienced on the ocean, but it wasn’t expected on this lake – that’s for sure. Waves were washing over the bow right up onto the front portlight, and I was getting slammed by waves beam-on as I turned WiTHiN around to feel-out her stability in every conceivable orientation. No problems at all with control, my speed into the wind, or powering through.
I returned to the dock and spent the night in the cabin of WiTHiN. Today, Ken and I are touring Okanagan Lake and putting the drive leg to a good test. We may do the same tomorrow and spend another 5 to 10 hours on the lake. I’m apprehensive about the drive leg, but the longer we spend out here, the more confident I am becoming in our fix. When I get back to Calgary, I think I want to set up a tub of water, the drive leg and a motor and run it 24/7 for a few months.
Mahalo!
Greg
dennis on October 29, 2009
You guys are having quite the adventure, thanks for all the updates. Love to follow. Good luck tweaking the drive system. Thanks for sharing.
David Tangye on October 29, 2009
Those sort sharp lake waves are an excellent test for the ocean. Waves in shallow water, near land, in tidal areas and coastal points are mostly more confused and usually tougher to handle for small craft than when way offshore, where they might be mountainous but are also likely to be long and nice and predictable (except every 1 in 10,000 :-)).
Guy Gilbert on October 29, 2009
In my opinion, the drive system should be able to resist to human legs while the propeller is trapped in a fishing net. This would be the ultimate test.
Frank on October 29, 2009
While running 24/7 for months is a good test, and I would recommend that you do so, I would also include other testing along the lines of what Guy suggested. I.e. you need to subject the system to shock waves, abrupt starts and stops, abrupt reversals and other high frequency transients. Those are more likely to cause the types of breakage that you experienced recently.
Bryon Howard on October 29, 2009
Way to power into those Waves Greg.
Good to hear there were no problems with control, speed into the wind, or powering through.
Been thinking about squeezing into the cockpit … and am inspired to get on my bike trainer!
Peter Raymond on October 29, 2009
As a mechanical engineer I agree that it’s important to test, but with the break happening so quickly, that indicates that there was a design problem.
The force you can apply at the pedals and the gearing lets you calculate the shaft torque. The radius of the shaft will give you the shear force that the shear pin has to resist. The area of the pin will give you the shear area, so you can calculate the shear stress that the pin has to resist for normal use. I would recommend assuming that only one side of the pin is carrying the full load and look for at least a factor of safety of 5.
A little harder is to figure out what would happen if the prop was spinning at full speed and a stick got stuck in the prop. You might want to try testing that on land.
In outboard motors there used to be a shear pin in the prop. If the prop hit a rock the pin was designed to shear and to be easy to replace. As I recall, the pin was under a removable cone on the back of the prop shaft. I think that now most outboards have something that will limit torque and allow slip if the load gets too high.
For your use I think a prop shear pin would be fine, but you would like it to be easy to replace and it should be designed to be the first thing to break. Of course, you also need to carry spares.
Frank on October 29, 2009
I found this to further clarify what Peter said:
http://answers.yahoo.com/question/index?qid=20080921173739AAta1i8
Philip Chadez on December 21, 2009
Nice level of information here. There is so much data around about this subject that sometimes you cannot see the wood for the trees but you have pitched this at just the right level so that the lay person can understand – thank you!