[Voodoochile]

I always wondered if a bent fork would be more supple compared to a straight bladed fork. It would seem to me that the bend would work just as you see the curved seat stays being designed these days. Instead of transferring road buzz straight up through blade it would be more shock absorbing.
This is only my opinion being in the tool and die design trade. I have not scientifically tested this theory though.

 

[Voodoochile]

Okay so why were most of the older bikes built with a curved fork? I honestly don't know if straight bladed forks have been around all along but I always remember seeing curved forks. It seems like it would be easier to make a straight fork (maybe I'm wrong). Why would the builders go to the trouble of bending the blades?

 

[Voodoochile]

Does this answer my question? Hmmm
http://en.wikipedia.org/wiki/Bicycle_fork

 

[Voodoochile]

Variety is the spice of life. Some like it one way while others like at another. Ain't life grand?

But, yes it is easier to build a straight bladed fork simply because you don't have to go through the process of bending the blades. But, the additional work is minor.

So why on earth would you bend it? Looks? Shock absorbsion? I would only guess the later would be a reasonable explanation for the curve. Maybe it's just a learning curve.

 

[Voodoochile]

Maybe the early builders found it was easier to achieve the offset by bending the blades and attaching the steer tube and crown straight.
I'm a tool and die maker and work with steel all day every day for over 20 years. I've also designed many dies and machines for production and personally the only time I would bend something is for ease of application, unless there was a very good outcome for the reason of the bend. Everything we do is built from an idea. Bending is not easy for me unless I have a machine to make the bend consistently and accurately.
I’m not looking to get flamed. LOL

 

[Voodoochile]

Just thinking realy quick. If I were going to build a fork which I have no experience at all. We build dies mainly to stamp out parts with many forms and bends like a bottle opener for example. If I were to build many I may fasten the steer tube and crown straight to save time cutting and welding angles. I may then build a machine to bend the blades to achieve the offset. How do the builders bend the fork blades on a steel frame? They don't do it by hand do they? Or does the tubing co. do that for them when they mfg. the tubes. This of course leaves out CF and Al.
I know I'm pushing it guys but I'm interested.

 

[Voodoochile]

That's some of the info I was after from you guys that build your own forks. Thanks for posting that stuff. Do you guys also build straight forks? I would imagine you do. If you were to suggest a fork it kind of seems like it all boils down to style then. I was guessing that fork bending by hand would involve heat but I guess bending them cold does the trick just with a special tubing bender. I'm glad I asked all my pushy questions. Thanks for not flaming me. LOL

 

[Voodoochile]

Couple of points--it seems that if Ernesto is telling the story at all accurately, he came up with the design for the Precisa straight bladed fork because he was challenged by the Ferrari materials guys who asked point blank, "Why do you bend the forks?" E answers "for handling/damping." "Let's test" said the Ferrari guys.

And they found no significant improvement with traditional curved forks vs a straight fork bent at the crown and the latter had advantages (stronger because of no residual stress from cold bending). And the Precisa was the result.

But I think for a lot of years, conventional wisdom was that you had to curve the fork blades for ride comfort.

Second point is where the stress is--wasn't it Ritchey who first made a headset with a larger bottom frame cup precisely because it carried more stress?

Where did you find that story about Colnago? I'd like to read that.

 

[Voodoochile]

On a straight blade fork... I'm guessing the steer tube is welded to the crown on an angle then to achieve the offset. Is that right?

 

[Voodoochile]

If it has offset, then yes.

There is no reason you are required to have fork offset.

Okay so let me ask you this...
I bought a Casati frame off eBay NOS and I don't like the fork. Money is tight but I was looking at this Soma fork with a 41mm offset ($130). I've read that most road racing bikes use between 43-45 offset. I've seen track forks with even less offset. I'm not sure of the HTA on the frame but it looks kind of steap. Would the fork with 41mm offset ride alot different from a 43mm.? How would it ride different? Why does Soma use this offset instead of the standard 43mm I've seen on other forks? I'm not sure how it would ride with that offset so I want to get some advice.

Soma Fork with 41mm offset...

 

[Voodoochile]

Honestly I don't know if the fork on the frame has a 43mm. I won't get it until tomorrow. I'm just guessing the fork that came with the frame is standard but I guess I can measure it when I get it. So with more trail does it steer slower or faster?

 

[Voodoochile]

 

[Voodoochile]

Okay so if I get this right more trail would make the ride more twitchy? Harder to ride with no hands. My Colnago CT-1 was very hard to ride with no hands and twitchy and my Tommasini Tecno seems slow to turn like I need to lean alot more to get it to turn.

 

[Voodoochile]

Your Casati's fork is period right for an mid 90's Italian frame. The Soma is quite likely designed with their frame's geometry in mind hence the 41mm rake. Build the frame up with the intended fork and at least see how it rides as Casati intended. Then look at replacing the forks. By bolting a different fork into it you'll possibly kill the handling and ride characteristics. Casati have probably forgotten more about frame building than Soma know too!

Yes I agree. I think I'll leave the intended fork. You're right.

 

[Voodoochile]

Your Casati's fork is period right for an mid 90's Italian frame. The Soma is quite likely designed with their frame's geometry in mind hence the 41mm rake. Build the frame up with the intended fork and at least see how it rides as Casati intended. Then look at replacing the forks. By bolting a different fork into it you'll possibly kill the handling and ride characteristics. Casati have probably forgotten more about frame building than Soma know too!

After receiving the frame-set I would never break this up. I didn't think it was going to be this nice. I'm actually blown away because it looks ten times better in person. As good as any De Rosa or Cinelli I've seen and that's saying a bit. The paint and chrome looks better than my Tecno too. I really didn't think the paint and chrome looked as good as I expected on my Tecno though considering the price of that frame set. This thing was an absolute bargain at $550. The fork looks pretty good to me now. An engraved crown would be sweet but it is what it is and I'm more than satisfied. I can't wait to ride this thing. I checked the STA (73.5) and HTA (73) with one of my machinist protractors from work and it's exactly what I was looking for too. I looked for the angles everywhere on the web but only found some angles from other Casati frames and they weren’t exactly what I would have liked but this frame is more standard it seems which is good. Shame on me for wanting to put a Soma fork with this frame. Wow!