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Old 01 March 2005, 16:14   #11
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Quote:
Originally Posted by slimtim
Ok, here we go. This is my best shot at trying to explain it.

The blue arrow indicates the direction at which I think the boat would move if the seat stayed where it was. I'm thinking that this allowable movement is un-natural to the movement the boat will actually make when hitting waves at speed (it will want to go up and back...like a mountain bike wheel hitting bump in a track when travelling at speed). The green arrows show how the hull would naturally pivot with this linkage (kind of). Pink arrow just shows that the shock can only compress, from its fully extended position...obviously.

Does that explain what I'm on about? Am I talking sense or is it all crap?

Sorry about going slightly off topic RibRoy, perhaps JK can start a new thread.

Great looking seats by the way!

Cheers



Tim
Tim....I am no engineer but I know what you are getting at here, you'd prefer a different colour wouldn't you?
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Old 01 March 2005, 16:15   #12
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Considering a load on the seat: if the bow rises and the stern is the fulcrum there is compressive load on the spring. If the stern rises and the bow is the fulcrum there is compressive load on the spring. If both the bow and the stern rise there is compressive load on the spring. And all moments between bow and stern will cause a compressive load on the spring. Only if the bow goes up/down and so does the bow/stern, so as to pivot directly under the spring, is there no compression of the spring but in that situation you wouldn't need it. The fore and aft movement of the load due to the arm pivoting is unlikely to be a problem. Imho, of course.
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Old 01 March 2005, 16:19   #13
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Quote:
Originally Posted by jwalker
Considering a load on the seat: if the bow rises and the stern is the fulcrum there is compressive load on the spring. If the stern rises and the bow is the fulcrum there is compressive load on the spring. If both the bow and the stern rise there is compressive load on the spring. And all moments between bow and stern will cause a compressive load on the spring. Only if the bow goes up/down and so does the bow/stern, so as to pivot directly under the spring, is there no compression of the spring but in that situation you wouldn't need it. The fore and aft movement of the load due to the arm pivoting is unlikely to be a problem. Imho, of course.
Well now I understand..........
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Old 01 March 2005, 16:28   #14
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Whatever ... Its an improvement over non-spring seats.

RibRoy, lets us know how you like them. I'm planning on get a 7m rib someday and I'd like comfortable seats.
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Old 01 March 2005, 16:28   #15
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There is only one alternative......fit these instead
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Old 01 March 2005, 16:29   #16
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haha, lol at Robin! Yeah, if I designed it, I would specify some pimpy zebra stripes or something!

Nick and Jeff, there is no doubt that the shock/damper system will compress however the hull moves underneath (unless the pivot is where the shock meets the hull as Jeff said...but this wouldn't be a problem as it would be like a node of oscillation) and there is no doubt that it would have a significant effect on increasing driver comfort. It just that I don't think the path at which the unsprung mass (hull etc) can take is ideal.

Imagine the suspension fork on a bike again. If mountain bikes were designed with the headtube angle the other way (so the forks pointed backwards), then the forks would absorb bumps but not nearly as affectively. Lots of energy would still be transfered to the rider. The bike would also look crap and handle like a dog.

hhmmm, if only I could apply this much imagination and thinking to my uni project!

Tim
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Old 01 March 2005, 16:34   #17
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Quote:
Originally Posted by robin
There is only one alternative......fit these instead
I guess you are as lost as I am, I think they are a smart looking seat, probably a major finger hazard, but as for the logistics of which way the seat will rise or fall when the bow goes up or down has hopefully been taken into account as they don't look cheap.
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Old 01 March 2005, 16:36   #18
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They look superb don't they
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Old 01 March 2005, 16:36   #19
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Quote:
Originally Posted by slimtim
Imagine the suspension fork on a bike again. If mountain bikes were designed with the headtube angle the other way (so the forks pointed backwards), then the forks would absorb bumps but not nearly as affectively.
Tim
Yer reckon. Try pushing a wheelbarrow up a kerb and then try pulling it up the same kerb. A bike is different because the forward lean of the fork makes the front wheel a castor, which is a bit essential for riding stability.
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Old 01 March 2005, 16:37   #20
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Quote:
Originally Posted by slimtim
hhmmm, if only I could apply this much imagination and thinking to my uni project!
Tim
Just a thought but perhaps this should be your Uni Project!!!
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