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View Full Version : Bottom Bracket carrier for my Tubular bike frames.



DannyC
06-30-2014, 12:22 PM
Both the High-roller and the Terra-Fox are made from 1 3/4 inch 16 gauge tubing.
While I could (of course) just fish-mouth the Bottom Brackets into a fixed position on each bike, I am not yet fully confident in my building accuracy (Cut/weld/swear/grind/repeat) and I think it is probably best at first (during shake-down) to have a movable BB.
So Today I have been making a tubular Bottom Bracket carrier to fit to this bike and the Terra-Fox.

I measured the actual OD of the tubing and it is 44.65mm. I searched on e-Bay and found a mild-steel "non-swaged" 45mm through connector for exhausts.
I used sections of the pre-manufactured brackets as attachment points for my BB.
I cut a 3mm slit along the length of the underside of the exhaust-tube.
I used the 10mm flanged nuts that came with the U-Clamps to provide mounts for 2 Quick-release clamps.
I aligned them with an 8mm bolt and nuts and clamped them to the underside of the tube, welded them in place and then removed the bolts and nuts.

http://s5.postimg.org/cb81u9wmb/P1030152.jpg (http://postimg.org/image/cb81u9wmb/) http://s5.postimg.org/fjcj7biw3/P1030153.jpg (http://postimg.org/image/fjcj7biw3/)

The tube is a slip-fit over the main tube of the High-roller and the QR clamps will close the 3mm gap and will make it a tight fit.
Here is the completed assembly with a single chainwheel and pedals mounted.

I have yet to trim the exhaust joiner down to the minimum length I require.

http://s5.postimg.org/7li45o5lv/P1030154.jpg (http://postimg.org/image/7li45o5lv/) http://s5.postimg.org/imd9aoxur/P1030155.jpg (http://postimg.org/image/imd9aoxur/) http://s5.postimg.org/dxx9fi8o3/P1030156.jpg (http://postimg.org/image/dxx9fi8o3/)


http://s5.postimg.org/j48eqjnfn/P1030159.jpg (http://postimg.org/image/j48eqjnfn/) http://s5.postimg.org/5byl8nm1v/P1030160.jpg (http://postimg.org/image/5byl8nm1v/)

Such a BB clamp arrangement will allow me to finalise the best place for the BB on both bikes.
While the welding is not "perfect" by any means, it appears to be solid enough for the task.

darnthedog
06-30-2014, 05:16 PM
Danny-you need to stop that!
I mean your welds have been proven and your philosophy of Weld-swear-grind-repeat is paying off. That is a great looking bottom bracket. Esspecially for someone who didn't know how to weld till recently. And your becoming very creative as well to fix the challenges you are face with.
I say your getting down right good. So keep up the good work and quite putting your self down. Your doing great.

DannyC
06-30-2014, 05:49 PM
That's very kind of you DTD, your confidence in me is much appreciated. :)
I think a clear problem is that I am comparing my "raw" welds to the shop-bought bike "TIG-WELDS" that are so precise & perfect.

I do still "wince" when a weld goes awry, but I also get a sense of real satisfaction when one goes exactly as I want it to.

It is, after all...practice & familiarity that makes for "perfect" and as you say this is fairly new to me, so perhaps I should "lighten up and cut myself a bit of slack".

I suspect this BB arrangement will be likely to damage any paintwork on a main tube as it is adjusted "fore & aft" (because it is a "snug" fit), but that is really what it is for, it is intended to be sacrificial and only to be required until I determine more precisely the best position for the BB long-term. The fact that it can be common across the 2 bikes means that I can build one and prove out the best position on each bike and then cut the fish-mouth in exactly the right place.

Or, if it proves to be that it works really well and it is not a "paintwork-destroyer" I can keep it as a fully adjustable BB assembly and I will have a proven cheap (10) source of sliding BB assembly parts.

Thank you for the moral support, it really is appreciated.

My stainless bolts etc. for the fixing of the seat-stays should be in any day now and then I can have the seat properly and firmly fixed so I can sit in it and work out what length & angle to make the extended gooseneck for comfort.

dkerrivan
07-01-2014, 05:30 PM
Very Clever DannyC... very clever, and looks well thought out to boot!

DK

DannyC
07-01-2014, 05:52 PM
Thanks DK :-)

I will report back as to how well (or not) it works when I get further into my builds.