Catamaran 2 fat bikes into a Quad

Given you are now using steel framed bikes why not use steel for the rest and weld it. Going wider means longer beams across and aluminium makes really poor beams. You are using it off-road so forces are likely to be higher than road use with the potential for accidents and flipping with the sail. Steel is much more forgiving than aluminium particularly in beam use. You've already lost the corrosion benefit of aluminium with the steel frames.
 
Given you are now using steel framed bikes why not use steel for the rest and weld it. Going wider means longer beams across and aluminium makes really poor beams. You are using it off-road so forces are likely to be higher than road use with the potential for accidents and flipping with the sail. Steel is much more forgiving than aluminium particularly in beam use. You've already lost the corrosion benefit of aluminium with the steel frames.
I have the aluminum, I don’t have the steel. My welding isn’t all that good, but once I have this all figured out I might go back and rebuild it back with steel. There is also the budget, which got heavily slashed.
 
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So I’m thinking about the pedal power drive train. This is my idea to drive both rear wheels with a straight axle. This photo is from a go cart axle on eBay. I photoshopped in the sprockets on either side. This would ride behind the rear wheel and short chain sections would go to each cassette. I’d manually experiment with the position of the chain for the gearing.
 
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this is an example I found on YouTube that I want to implement on my quad. The question is how to build it. Can I use the go cart axle and modify it to work? The chain of the bike is different than of the go cart so I’d have to use bike sprockets.
 
No reason why it can't go there. It does mean the derailleur could be vulnerable on break angles if tackling dunes as it'll be outside the wheels circumference. It could be a problem if you are going up and down dunes and may need some protective shielding.
 
No reason why it can't go there. It does mean the derailleur could be vulnerable on break angles if tackling dunes as it'll be outside the wheels circumference. It could be a problem if you are going up and down dunes and may need some protective shielding.
No sand dunes will be traveled on, mostly flat, mostly hard pack along the water. Deep soft sand getting to the crossings.
 
Well I’m cheating on the rear axle part because of a time constraint. I’m getting a trike conversion kit from dream bikes from Brazil. $229 total, to my door, open box special. This gives me time to work on the next part.
steering. I’m using cable steering after my very long pull levers so I can get this whole mechanism behind me so it’s empty out front.
My problem now is now I have to reduce the amount of throw to something useable.
The video shows more.
 
I recall that your initial thought was to have a fat tire beach quad, that would also be able to cross various passes along the beach.
Came across this photo on another forum, and it made me think of your project :)
Looks like heavy pedaling, though .........

Monster_with_floats_r6wn4j.jpg
 
I recall that your initial thought was to have a fat tire beach quad, that would also be able to cross various passes along the beach.
Came across this photo on another forum, and it made me think of your project :)
Looks like heavy pedaling, though .........

Monster_with_floats_r6wn4j.jpg
Yes! That was very similar to my initial idea. Those pontoons are expensive! I was going to make my own. This design has the bike wheels in the water, I’m guessing fresh not salt water. Ideas evolved, now I’m using SUPs, a pair of stand up paddle boards, it’s way cheaper! Plus I have roll on roll off disembarking. New change, I’m rowing instead of pedal prop drive. Too much to engineer in a short timeframe.
 
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