Franken Fixie.......

[Lark2004]

Ok, I've been toying with the idea of building a Fixie for a while.... nothing new there....

A few days ago I built up an old Univega MTB frame as a SS and it's turned out to be a fun bike to ride, the point of that one was to sort of test the waters, without spending any money or wasting heaps of time..... ( I had enough parts sitting around in the garage)

So now I am starting to gather bits for a fixie....most of which I now have.

A frame


A flip flop hub with an old freewheel stuck on it (may have to get a bit brutal in order to remove it)
It's a 40 hole hub, so I have to go looking for a 40 hole rim, I am thinking of contacting Velocity and seeing what they can do.



Now, here comes the small issue with what I have...... the BB shell on the frame is stuffed. The threads are stripped on the drive side (I got the frame for free, probably the reason why).
So I am thinking of cutting it out and welding in a BB shell from a BMX....and fitting the BMX one-peice cranks (there's a huge range of chainrings that I can fit to these for next to nothing).


And while I'm at it, maybe welding these into the back of the frame too


Thoughts?

[aerohydro]

Sounds like a fair bit of work, it might be easier to find another frame. What sort of welder do you have? Bike tubing is thin obviously, but I've successfully welded some cheap, fairly heavy gauge bike tubing with a MIG. I reckon I could do it with my little inverter stick too, but not with good quality, thin stuff. Why are the fork ends better than the dropouts the frame has already? Depending on how bad the threads are you might have success getting a bike shop to run a tap through them.

[Lark2004]

The plan was to use a MIG with .6mm wire, with this setup I can weld extremely thin metal without blowing holes in it..... The rear? well, no real reason to change it other than, because.....If I'm going to change one part of the frame, why not two parts...

Also, I was thinking with the rear fork ends, I can use some of these...

[super_simian]

Now, here comes the small issue with what I have...... the BB shell on the frame is stuffed. The threads are stripped on the drive side (I got the frame for free, probably the reason why).
So I am thinking of cutting it out and welding in a BB shell from a BMX....and fitting the BMX one-peice cranks (there's a huge range of chainrings that I can fit to these for next to nothing)

There is a BB available with a soft-ish plastic sleeve to overcome this very problem, the idea is that it self-taps into whatever remains of the thread. They are useful also for people with french threaded BB shells, instead of re-tapping etc.

[aerohydro]

The MIG with fine wire should do the job nicely, just make sure you get the BB shell clean and mitre the ends of the tubes accurately for nice close fits. Actually that's going to be pretty difficult. What's your strategy there?

[Lark2004]

I was going to use a die grinder on a flex shaft to mitre the ends to the BB shell. I figure that is the easiest way to get into the ends of the tube with the frame already being assembled. The BB shell is already stripped and cleaned ready to go. Hopefully I should have a result by the end of the weekend.

[aerohydro]

Yeah that would be a good way of doing the shaping. The marking out of the mitre shapes is what I would find dificult. It should be possible to calculate it all but I doubt my brain could handle it.

[Mulger bill]

There is a BB available with a soft-ish plastic sleeve to overcome this very problem, the idea is that it self-taps into whatever remains of the thread. They are useful also for people with french threaded BB shells, instead of re-tapping etc.

Oooohh, likin' the sound of that, got any details please?

Shaun

[munga]

i saw your cut-down gt (the one with the pinny forks?) so i've no doubt you can dooo eeeeeeeet!

[brauluver]

How did this pan out mate?

Any pics?

[Lark2004]

all plans have been put on hold at the moment...... until I have access to the mig again.

I did get the frame cut and filed...it looks like it will work ok, I've modified things a little, by raising the BB shell up a bit. It raises the centre of the bb about 6 or 7 mm higher than the original BB...... might help a little bit in cornering, not too sure yet. I'll find out soon enough, hopefully.

[brauluver]

12 months on! What's happening with this ugly duckling ?

[Lark2004]

didly squat....

I have got my Repco superlight filling my singlespeed / fixed gear needs at the moment, and I have a Tange Aero track frame waiting to get made up when time and money permits.... so the franken fixie will probably never see the light of day.