Nautilus (Beached Bobber) - WBO 2018 Scratch Built

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The Renaissance Man

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Was looking at the spec. drawing of this frame and it occurred to me that all of the lines seem to almost have a Fibonacci-esque quality about them.

b bobber.jpg


That's a good thing.:cool2:
 

kingfish254

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Scallops (...continuing a developing nautical theme)

I first drilled a through hole to establish the head tube location and angle. Then I sketched out the approximate scallop shape with a sharpie marker onto the top section of the tube. After transferring the shape to the opposite side the sections were cut off, flipped and welded in. I've been smoothing out the tube a little as I go along. I've got the major dents on the tube in this area down to just a major ripple.

topTubeScallops.jpg


The center tube is two inches wide and needed to be narrowed to one inch for chain clearance and to match the bottom tube diameter. I originally was going to make this area flat but liked the scallops at the top of the tube enough to treat this the same way. The area at the top of this cutout will eventually be filled in. I've left it as is so I can do a final trim to match the exact angle of the chain guard. The non-drive side will probably just get a small flat angled cut at the bottom.

bottomScallop.jpg
 
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Bottom Bracket

Last time I used the rear tire/rim width combination I'm using on this build I was able to pull the freewheel and place a couple spacers behind it. This moved the sprockets out just enough so that the chain cleared the tire when in first gear. As I got into it I realized I didn't have the correct wrench to remove the freewheel this time. Pretty much had resigned myself to either letting the chain rub or just not use first gear!

@GuitarlCarl posted the observation that the bottom bracket on his Tyranny & Mutation / 36' Silver King is actually offset:
http://www.ratrodbikes.com/forum/index.php?threads/tyranny-mutation-36-silver-king.105534/page-2

So there was the solution! Especially since on this frame there is no chance for interference between the crank and the chain stays. I offset the bottom bracket by about 3/16 inch. That will give me the clearance and hopefully won't be noticeable while riding. It worked for the Silver King.

btmBracket.jpg
 
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Seat Tube & Mock Up

I drilled completely through the center tube to strengthen the seat tube attachment by welding it to two sides. I'll eventually trim and fill the front.

seatTube.jpg


Mock Up

Still need to weld up the fork legs and lengthen the steer tube. Also leaving the top of the fork tubes long for now. I'm fairly certain they will be trimmed down to the top of the triple tree but leaving the option open as long as possible.

mockup01152018.jpg
 

GuitarlCarl

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That offset... Two ways to deal with it that I can see.
1- Use a dogleg crank like the Silver King did but your offset isn't as much, so...
2- Using a 3 piece crank may allow you to put the shaft in offset a bit. In fact a good welder like you could probably cut and splice the shaft to incorporate the offset. You're killin' it bro. The Nautilus name is beggin' for some steam punk super detailing, maybe just a little copper and brass.

Carl.
 
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That offset... Two ways to deal with it that I can see.
1- Use a dogleg crank like the Silver King did but your offset isn't as much, so...
2- Using a 3 piece crank may allow you to put the shaft in offset a bit. In fact a good welder like you could probably cut and splice the shaft to incorporate the offset. You're killin' it bro. The Nautilus name is beggin' for some steam punk super detailing, maybe just a little copper and brass.

Carl.

Thanks Carl! It is begging for at least a nod to steam punk.

I was thinking of just going with the crank offset to the right... because it is such a small amount. And, there's no clearance issue on the left / tight side. If it feels too funky figured I could maybe use an adapter or a spacer to offset the left pedal. As a last resort was thinking I would even the bottom bracket back out by grounding down on the right and adding a little to the left. Hadn't thought of converting to a three piece but, I've got a nice well used one piece crank I wanted to use. I'll have to research a bit on the cut, lengthen, re-weld of the crank. I think the crank is forged or heat treated? The weld process might weaken the crank too much? If it can be done I'm sure there's an example somewhere around here.
 

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The real deal behind dog leg cranks is clearance to the chain stays. Should be the same on each side, that automatically puts the pedals in the same position, feeling centered while pedaling. Right? I'm just that ocd, I need my clearances to match...
A thick washer or not (maybe 2) between the inside race and the sprocket, moves the crank around. Always a pain retro fitting something to be just so. I imagine a scratch built is the same...

Carl.
 
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The real deal behind dog leg cranks is clearance to the chain stays. Should be the same on each side, that automatically puts the pedals in the same position, feeling centered while pedaling. Right? I'm just that ocd, I need my clearances to match...
A thick washer or not (maybe 2) between the inside race and the sprocket, moves the crank around. Always a pain retro fitting something to be just so. I imagine a scratch built is the same...

Carl.

Last build I definitely tapped into my ocd tendencies. To switch things up I'm building a little more loosely this time around.
 
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Agreed. I doubt it'll be noticed.

Kinda like steering trail too maybe. Even if trail is pretty far off you can usually adjust to it quickly. And for how this will be ridden, less than optimum ergonomics isn't going to be a big deal.
 
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Seat Tube

Trimmed up the seat post after welding it to both sides of the middle/top tube. I drilled out a patch from left over 2" tube, welded that into place and ground (relatively) smooth.

seatTubeInsideFill.jpg


Support for the seat post includes an attachment point for the rods that will bolt to the top of the rear dropouts.

seatPostSupportLinkageConnect.jpg
 
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