Wednesday, 16 April 2014

Fork it

I may have mentioned that I was not 100% happy with the forks on the Fatness, the biggest issue being the steerer tube flexing quite disconcertingly under load. This was because I used straight gauge 4130 where I should have used a proper butted tube. Various tiresome things have got in the way of doing anything about it, but now things have progressed.

One of the issues preventing progress is that I was really quite unhappy with where my TIG welding skills were at. I started the new forks a few weeks ago, but the welding of the crown parts to the steerer was frankly terrible, with lots of bubbles and voids and large chunks of tungsten thrown into the mix. I could TIG weld once upon a time, so why couldn't I do it now? This stalled things because I want 100% confidence in something as stressed as a fork and I fell into framebuilders funk.

As it happened I had ordered enough parts for two sets of forks, so a few days ago I decided to start in fresh on the second set. I did a few trial welds with the same issues, then decided to swap the tungsten from the recommended thoriated type to a ceriated one that came with the machine. What a difference! It was like coming home and settling in front of the fire with a hot toddy. And so I cracked on with super renewed enthusiasm. The skill is still not at the level it was when I did it for a job, but it is way, way nicer than it was.

Mitering in the fork tubes
Some slightly better then previous welds, yesterday. The next ones were much better than this.
All fitted up. I changed the design detailing a bit, the fork tubes are closer to each other for a start, this was defined by the Ceeway sourced plug in dropouts I used.
The fork is also taller to give a bit more vertical clearance. This slightly slackens the headtube angle, and I took a 10mm spacer out of the stem stack to drop it back to the previous height.
And I angled the fork tube caps and used flat sheetmetal instead of coins
Well, it is a fork attached to a fatbike. Time to see if it will work....
Yes, I have been riding some wet trails in the recent past. All trails in Christchurch are wet and will be for the foreseeable future.
So the plan is to ride it as it is for a week or two to see if there are any niggles, then strip it down for coating. The thin coat of primer is not really cutting it in the current conditions. I have been riding it a lot though.... including a trip with some fat friends to Hanmer.

In other bike related news I built this up for my eldest daughter - I got sick of buying crappy kids bikes and I figured this would last her for a good long while. I got it as a stripped frame and forks with wheels and brake calipers. By the time I bought a headset/BB/chain/cassette/hanger/derrailleurs/discs/levers/shifters/tyres it became probably the least economic option possible. But it looks sweet and will last forever. She loves it.

I also spotted these forlorn looking beasties in the woodshed, I will need to bring them inside for the winter I imagine.

In other, other bike related news I have a new set of tubes awaiting me in the garage. These are to make into my wife's fattie, which I may well TIG now, and looking further out I have plans for an updated commuter with disc brakes and much other secret goodness.