J.A. Jackson (v. 2.35)

contents

• overview
• specifications
  • parts
  • assembly torque values
  • gearing
    • alfine 8 documentation
    • a note on locknuts
  • frame dimensions
  • frame material
    • 3Al-2.5V titanium properties
    • 4130 steel properties
    • 7005-T6 aluminum properties
• grievances (issues)
• photos
  • frame
  • build
  • complete

overview

This is the second iteration of a bicycle I made in 2023, improving upon a number of issues logged over the course of the last year, and allowing the frame from the previous project to be reused in another (future) bicycle build.

It is a titanium-framed road/touring cycle with an internally geared rear hub of eight speeds. It has a number of features atypical of road/touring cycles, such as track dropouts, both disc and rim brake mount points, threads for all manner of fenders, racks, and accessories, clearance for wider wheels, clearance for fenders, a rear quick-release hub space of 135mm, and a tapered headset tube. If you look “off the rack” for this combination of things, you simply won’t find such a bike. I don’t know why that could be, but I do know how to make one.

The name is one I give whichever bike I’m riding primarily. It comes from a Joycean description of a Trinity College bike race:

“Bang of the lastlap bell spurred the halfmile wheelmen to their sprint. J. A. Jackson, W. E. Wylie, A. Munro and H. T. Gahan, their stretched necks wagging, negotiated the curve by the College library.”

specifications

I apologize in advance, some units are metric and some English, but this is not a preference: the world of bicycles is a confusion of units.

parts

assembly torque values

It’s handy to have a single table of the torque values you should be using for assembly of the bike, since they need to be looked up in multiple places otherwise. Here are the ones important for this version of the bike:

gearing

The Alfine 8 hub is attached to a 21t rear sprocket, and the chainring on the crank is 43t. This results in the following eight gears, in gear-inches:

When I’m pedaling at 80 RPM, which is typical for me, these gears translate to the following speeds in MPH:

alfine 8 documentation

The hub for this build has good documentation I’ve copied here. There’s a particularly important bit about the alignment of the various dots on the pulley side of things, which, without knowing, you’ll waste a lot of time divining. The critical illustrations are reproduced here:

a note on locknuts

You don’t really want to tighten the locknuts on the Alfine 8 too much - it’ll throw off the fitment of the pulley bracket on the one side, and simply put a lot of pressure and friction on the hub on the other side. Reasonable hand tight is fine, the thing is actually held together by the frame anyway, it’s not going anywhere once installed.

Also, this bike has a 135mm rear dropout space, which means the stock Alfine 8 fits great. If you happen to have 130mm spacing, as I did in my previous iteration of this bike, you can grind 2.5mm off each locknut to make the Alfine 8 the proper size, it’s not that hard. Just make sure to grind 2.5mm off each locknut (one is larger than the other, stock), so that the hub remains centered. I went ahead and bought a couple sets of locknuts with the hub so that I could have spares, some ground and some stock.

frame dimensions

frame material

The frame is made of a titanium alloy called 3Al-2.5V. This alloy is 95% titanium, 3% aluminum, and 2% vanadium. As a bike frame material, titanium works well for me.

• It is not as light as carbon, but it has a much longer riding lifespan, and requires less specialized maintenance routines, such as very careful torque application in fasteners, or friction pastes.
• It is heavier than aluminum, but has a longer riding lifespan, and slightly better corrosion resistance.
• It is lighter than steel, but about as strong, and features far greater corrosion resistance.

3Al-2.5V titanium properties

4130 steel properties

7005-T6 aluminum properties

grievances (issues)

I keep notes on what to change for next time here, as I did with the previous iterations of this bike. No one of these would precipitate a rebuild, but if I were to rebuild for some other reason, I will incorporate fixes to them.

• Cable routing with zip ties is inelegant. It was necessary here because I forgot to design in housing mounting clips on both chain stay bottoms (only one of them has mountings). The zip ties work well, to be clear, they’re just not as elegant as integrated mountings.
• I don’t have a good way to plug the unused cable routing ports on the bike. I might specify that they be threaded at the ends or something so I can use a bolt to cover them in the future. I like having the number of routings I have, since I may use them in the future, but I would prefer an elegant way to seal them when not in use.
• I am seriously tempted to have some drilled portions of the rear seatstays for LED integration. I would love to make the next iteration of this bicycle a crazy flashing circus. I’ll have to think through the effect on rigidity, but it seems like a few 3mm holes wouldn’t be all that bad, and you can get some really bright SMDs in that space nowadays, wired internally to a battery stashed somewhere in a tube. Just an idea.

photos

frame

build

Build commenced on 28 October 2024.

complete

Build finished 29 October 2024, and the bike commuted to work that day.

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