UniCrown Forks

[mercalia]

what are the pros and cons of unicrown forks ( and the other type ) and why dont bespoke frame builders use them? ( My Dawes 1-Down has a unicrown fork and seems fine )

[531colin]

Mass production using lots of gear....big tube bender, mitering machine, accurate jig, welding tackle.....makes a big, stiff, ugly, heavy fork, cheaply.
A skilled man can make an accurate, lightweight fork using a simple jig a hacksaw and a blowtorch....and a light bender if he wants a rake other than 45mm.

[Valbrona]

Bespoke framebuilders don't weld. Framebuilders can buy pre-bent unicrown fork legs off the shelf.

[531colin]

.............. Framebuilders can buy pre-bent unicrown fork legs off the shelf.

Yes, but with a brazed crown its the crown which sets the width/tyre clearance, and you trim the blades to length. Unicrown isn't so simple.

Is this the worst of all possible worlds?

[fastpedaller]

.............. Framebuilders can buy pre-bent unicrown fork legs off the shelf.

Yes, but with a brazed crown its the crown which sets the width/tyre clearance, and you trim the blades to length. Unicrown isn't so simple.

Is this the worst of all possible worlds?

Crikey, until I clicked to quote for the reply I thought that was a jest! Surely the worst of all possible because it would just require more fork tube bending ! I really can't see the point (although I can see the point of unicrown set up for mass production). I have to comment that my On-One Pompino has a unicrown fork (standard issue with the frame) and the whole bike rides very well.

[531colin]

Never underestimate how far fashion can push bicycle design.

[Brucey]

.............. Framebuilders can buy pre-bent unicrown fork legs off the shelf.

Yes, but with a brazed crown its the crown which sets the width/tyre clearance, and you trim the blades to length. Unicrown isn't so simple.

Is this the worst of all possible worlds?

In the UK, custom/hand-made frames are not TIG welded for the most part. However whilst it is a viable way of building custom frames, it is perhaps devalued to some extent by being used on so many frames that are OTP or mass market. I prefer the look of lugs myself.

FWIW I have a crown like that on my Overburys Pioneer, (which is about 25 years old). I suppose that there's only limited scope for adjusting the exact fork length when building with this arrangement, but if you can adjust the length by (say) 3/4" eg by trimming the fork tips, you can also set the fork width to vary by about 1-1/2" because you can vary the trim on the ~45 degree bends near the crown. I guess you might need a couple of different fork blades; one to suit ~27" wheels and another to suit ~26" wheels, each with factory bends at the crown and to have the fork offset set later. With those one ought to be able to make narrow or wide forks to suit different wheel sizes without too much difficulty.

cheers

[goatwarden]

and why dont bespoke frame builders use them?

They do (at least did, and probably still do).
Chas Roberts used Unicrown forks for disc brake tandems.

[Steveo2020]

Robin Mather built a fixed wheel randonneur bike for an exhibition at The Design Museum earlier this year which had a unicrown fork. I think all of his bikes are now tig welded too.

Cheers

[531colin]

..................

Is this the worst of all possible worlds?

FWIW I have a crown like that on my Overburys Pioneer, (which is about 25 years old). I suppose that there's only limited scope for adjusting the exact fork length when building with this arrangement, but if you can adjust the length by (say) 3/4" eg by trimming the fork tips, you can also set the fork width to vary by about 1-1/2" because you can vary the trim on the ~45 degree bends near the crown. I guess you might need a couple of different fork blades; one to suit ~27" wheels and another to suit ~26" wheels, each with factory bends at the crown and to have the fork offset set later. With those one ought to be able to make narrow or wide forks to suit different wheel sizes without too much difficulty.............

To me, "you can make it work" is a dubious sort of advantage.
You could already make forks of different widths by selecting an appropriate crown, and trim the blades to length.
What is this crown apart from an attempt to make traditionally-constructed forks look like something they are not, ie unicrown forks?
Its much taller than a traditional fork crown, and bloody ugly.

there are plenty more just as daft...

[mercalia]

well Colin531 you wont like this on my 1-Down

Uni Crown Dawes 1-Down

[reohn2]

If ugly is the only gripe about unicrown forks I like ugly,YVMV mine won't,so ugly wins for me every time .

[Brucey]

I don't think that unicrown forks are very pretty or anything, not on a traditional touring bike, but I can kind of see the point on a machine that will accept a 2" tyre. I think the fork will be difficult to make as strong at the same weight using a separate crown of conventional design. I think a taller crown is part of that too.

However the uncrown design arguably lends itself to TIG welding rather than other joining methods. The 45 degree socketed crown is just the job for a builder that doesn't want to TIG weld the fork...? Obviously different steerers/tubesets will lend themselves to one design or another; I don't think that a steerer that goes into a lugged crown of any kind would necessarily be thick-walled enough to be TIG welded?

cheers

[fastpedaller]

..................

Is this the worst of all possible worlds?

FWIW I have a crown like that on my Overburys Pioneer, (which is about 25 years old). I suppose that there's only limited scope for adjusting the exact fork length when building with this arrangement, but if you can adjust the length by (say) 3/4" eg by trimming the fork tips, you can also set the fork width to vary by about 1-1/2" because you can vary the trim on the ~45 degree bends near the crown. I guess you might need a couple of different fork blades; one to suit ~27" wheels and another to suit ~26" wheels, each with factory bends at the crown and to have the fork offset set later. With those one ought to be able to make narrow or wide forks to suit different wheel sizes without too much difficulty.............

To me, "you can make it work" is a dubious sort of advantage.
You could already make forks of different widths by selecting an appropriate crown, and trim the blades to length.
What is this crown apart from an attempt to make traditionally-constructed forks look like something they are not, ie unicrown forks?
Its much taller than a traditional fork crown, and bloody ugly.

there are plenty more just as daft...

Not quite as daft because the top of the fork blade doesn't need bending like it will with the first example!