Adding structural foam to BB area?

[Scott Gordo]

I'm not sure if Bianchi still builds frames this way, but a couple
years ago I read that their high-end aluminum road frames were
injected with a structural foam around the bb area. This was done to
supplement the stiffness of the junction. It may make it stronger as
well, but perhaps not (as the stress may be transferred further up
into those paper thin tubes?)

I'm riding a '99 Litespeed Ultimate with a curved seat tube. I'm also
a big feller - 6'2, 220lbs. As I've put on weight, the frame is
getting flexier when climbing (imagine that). I have a growing concern
about the curvature snapping -- I've seen it happen on another frame.

Has anyone tried this structural foam trick? Pros/cons/suggestions?

/s

 

[Morten Reippuert Knudsen]

Scott Gordo <[email protected]> wrote:
> I'm not sure if Bianchi still builds frames this way, but a couple
> years ago I read that their high-end aluminum road frames were
> injected with a structural foam around the bb area. This was done to
> supplement the stiffness of the junction. It may make it stronger as
> well, but perhaps not (as the stress may be transferred further up
> into those paper thin tubes?)

They are still dooing it on their Titanim frame (The one M.Backstead won
P-R on in 2004)

--
Morten Reippuert Knudsen <http://blog.reippuert.dk>

Merlin Works CR-3/2.5 & Campagnolo Chorus 2007.

 

[Scott Gordo]

On Apr 17, 11:21 am, Morten Reippuert Knudsen<[email protected]>
wrote:
> Scott Gordo <[email protected]> wrote:
> > I'm not sure if Bianchi still builds frames this way, but a couple
> > years ago I read that their high-end aluminum road frames were
> > injected with a structural foam around the bb area. This was done to
> > supplement the stiffness of the junction. It may make it stronger as
> > well, but perhaps not (as the stress may be transferred further up
> > into those paper thin tubes?)
>
> They are still dooing it on their Titanim frame (The one M.Backstead won
> P-R on in 2004)
>
> --
> Morten Reippuert Knudsen <http://blog.reippuert.dk>
>
> Merlin Works CR-3/2.5 & Campagnolo Chorus 2007.

So I guess...I dunno. Is Bianchi the only company doing this? Any
credible evidence that it does anything? Is this an application that's
used outside the bicycle industry?

/s

 

[dabac]

...Is this an application that's
used outside the bicycle industry?

Well, sort of. The method of bonding thin sheets of stronger materials to both sides of low-density spacers/fillers is widely used, resulting in a stiffer yet light structure often referred to as a "sandwich" or similar.

Any credible evidence that it does anything?

Can't really visualize what it'do for a tube structure, but I imagine it'd make it more resistant against collapsing.