True monocoque frames. Who makes them?

[kgt]

Manufacturing a true monocoque (one single piece) frame is a more expensive, more exclusive procedure since you need as many moulds as the sizes produced.



Most mass production carbon frames are created by 4-5 or more pieces/tubes glued together. This obviously results in a non uniform frame in which there are weaker areas and joints where cracks or delamination may occur. Tht's why some respected manufacturers (like Parlee or Crumpton or Colnago) still use lugs for their top frames.
It seems that very few manufacturers make monocoque frames nowadays and most monocoques are track frames where the power-stress is the maximum and the stiffness must be the highest possible.
So, who makes still monocoque road frames? I know Cipollini does, anyone else?

[kgt]

Look calls it one piece, no lugs monobloc. Almost...

[Stefano]

Hi KGT,

Fully Monocoque frames are interesting. However, the differences between "true" monocoques and the "rest" of the frames on the market is a little bit more nuanced.

Monocoques are interesting because it allows you to have continuous fiber runs in high stress areas, forego overlapping/bonded tube sections, and have a one-shot production methodology, which can reduce price. However, there are several drawbacks. Because these frames are all made in one piece, it is very difficult to obtain some desirable shapes from either a strength or stiffness perspective and release from the mold. It is difficult to do certain bladder/compression techniques on a monocoque because removing them would be impossible. Small tubes, like chainstays or seatstays, may not get optimal compression. In general, because you are subjecting the entire frame to the same curing conditions everywhere, it precludes using material combinations or structural elements that could be useful. (easy ex. of structural element- trek madone 9, tube within a tube)

As far as non-monocoques, your assessment of them as inferior in strength or stiffness is simply untrue. The safety factor of a frame's bonded joint generally exceeds the safety factor of the surrounding tubes by 3:1 or greater. The reason a frame manufacturer would make a frame in pieces has much more to do with trying to tune/optimize structural properties of the frame than cost- in fact, in most cases each frame size has to have its own set of molds- 6-10 different molds PER SIZE. Just look at the lightest, most aerodynamic, or stiffest frames year after year in the tour test- almost none of them are true monocoque. There are many ways to skin a cat (or build a frame), but at the moment it looks like the best method from a performance perspective is to do it in at least a few pieces.

Best,
Stefano

[darnellrm]

Great post Stefano!

Not many people do true monocoque because they figured out years ago that it's not the best way to build a frame due to the manufacturing issues mentioned above.

[wingguy]

Manufacturing a true monocoque (one single piece) frame is a more expensive, more exclusive procedure since you need as many moulds as the sizes produced.

I don't quite understand your logic. As pointed out a non monocoque needs more than one mould per size...

[prendrefeu]

OH SNAP!

As far as non-monocoques, your assessment of them as inferior in strength or stiffness is simply untrue. The safety factor of a frame's bonded joint generally exceeds the safety factor of the surrounding tubes by 3:1 or greater. The reason a frame manufacturer would make a frame in pieces has much more to do with trying to tune/optimize structural properties of the frame than cost- in fact, in most cases each frame size has to have its own set of molds- 6-10 different molds PER SIZE. Just look at the lightest, most aerodynamic, or stiffest frames year after year in the tour test- almost none of them are true monocoque. There are many ways to skin a cat (or build a frame), but at the moment it looks like the best method from a performance perspective is to do it in at least a few pieces.

Great post, Stefano.

[Calnago]

Manufacturing a true monocoque (one single piece) frame is a more expensive, more exclusive procedure since you need as many moulds as the sizes produced.
...
Most mass production carbon frames are created by 4-5 or more pieces/tubes glued together. This obviously results in a non uniform frame in which there are weaker areas and joints where cracks or delamination may occur. Tht's why some respected manufacturers (like Parlee or Crumpton or Colnago) still use lugs for their top frames.

Yes, you do need as many molds as frame sizes. It's certainly a lot more expensive, so from a purely business side of things that's probably not the smartest way to go about things. But in itself that is neither a good or bad thing. Stefano points out the reasons why in his post.

And I completely disagree that a non-monocoque frame "obviously results in a non-uniform frame in which there are weaker areas and joints... blah blah blah". It is not "obvious" at all. There are many ways to skin a cat, with the end result being largely the same. Stefano also quite nicely addressed this in his post.

Finally, I don't think I know the true answer to why certain respected builders still use lugs any more than you do, but I suspect it's due to a multitude of reasons.... including but not limited to a) that's how it's been done in the past, and it's a tried and true process, and one they have mastered; and b) it's fairly easy to produce customized geometries (could you imagine a small frame builder trying to produce an individual mold for each and every client). Those are just a couple reasons which I would think are pretty valid.

Stefano's post really nailed the jist of most things technical however.

And of course, everyone knows that a monocoque frame is simply more aero as well
Oh wait... I wanna seem some data on that last point.

[kgt]

It seems that most track frames are true monocoques. What's the reason? Isn't that related to strength and stiffness?

[stormur]

If Stefano is right, why so many frames with bonded chainstays brake on turbo trainers, and such an issue is not known to frames where rear tringle+bb is from one mold ? And yes, chainstay bonding area is a place where damages occur.

Just asking

BTW , BH is making mono-frames. Forks too.

[Stefano]

Hi Stormur,
I am not sure whether your information is correct. All types of bikes break, in all sorts of different places. If you know of any statistical failure data that shows a difference between frames manufactured in different ways, that could be hugely interesting and informative for this discussion. If so, bring it out! Otherwise, unsupported claims don't really mean much.

KGT,
Where have you gotten this information about track bikes? From my count, most track bikes in total are steel
Seriously though, what manufacturers of track bikes in use by pros, can you definitively label as monocoque?
Cervelo- not monocoque, you can see seams internally
Fuji- not monocoque
Look- not monocoque (says monobloc, but stays bonded on to front triangle)
Felt- not monocoque

Nobody is saying you can't have a good monocoque frame. What I am saying is that you can also have good frames from many many other methods that are comparable (or better!) in every way.

[Calnago]

I can't speak for Stefano, but I would suggest that while there is more than one way to skin a cat, some will still manage to f-it up regardless of the method they choose. This is where Quality Control and sound design and manufacturing processes come into play.

As for the breaking frames on trainer scenario, I also suspect that since the vast majority of frames are not "true monocoque" or whatever you want to call them, that statistically it's hard to say if one is more durable on a trainer than another. I don't know. Can you say that not a single monocoque frame has ever broken on a trainer. I don't know. I can't. And I wasn't aware of widespread frame breakage on trainers either, but clamping a frame rigidly into a trainer would not be my first choice of use for a nice frame. And if I did, I wouldn't be pretending to be sprinting and wrenching the frame side to side... a lot of leverage in that scenario can't be good for any frame, no matter what it's construction.

edit: Ha, looks like Stefano beat me to the punch again.

[wingguy]

If Stefano is right, why so many frames with bonded chainstays brake on turbo trainers, and such an issue is not known to frames where rear tringle+bb is from one mold ? And yes, chainstay bonding area is a place where damages occur.

So many? How many?

I've seen a lot of broken bikes, of all manufacturing types and materials (except maybe steel), and I've never seen that.

[AJS914]

I've always wondered if this idea that you shouldn't put a carbon frame in a trainer is actually myth or reality. I broke plenty of steel frames back in the day - never actually on a trainer but they were ridden on the trainer. I haven't yet broken a carbon frame. It seems that they usually break after a trauma.

[stormur]

Stefano, you want statistic, a voila : I had 3 BMC, 2 carbon frames, 1 bonded and 1 with mono-chainstay. Those bonded broke after 200km... so failure ratio is 50% for carbon frames , and 100% for bonded chainstay frames.

Now seriously :

My thesis ( based on posts on various forums ) is that bonded chainstay frames do/did brake much more often than single piece ones. Not empiric ratio I would estimate at 5:1. If you believe that any manufacturer will give you real warranty claims data, you're more than naive... .

If you say, they're not weaker/ do not break more often- GIVE US STATISTIC DATA proving that. Lack of it, make my thesis valid. ( sounds familiar ? ) . Prove , if I'm wrong. If you can't, I'm right

From your previous post : bonded area strength 3:1 : provide us , please with reliable engineering data confirming that ratio. Fiber , resin, bond agent data, type of sleeving, dimensions, testing procedure,...

( for your info, it will be verified by 25y experienced engineer working with laminates for yachting and aeronautic businesses )

BTW if part of construction is 3 times stronger than rest of it, do you know distibution of forces and stresses in such area ? Ask ANY engineer working with structural composites


To clarify something : I have nothing against structurally bonded constructions. If designed well, it is more than good enough.
After "initial" issues with bonded chainstays seems that manufacturers solved this issue with additional reinforcing weak areas ( i can clearly see it on my Wilier ( naked carbon all over ) : bonded chainstay, additional wraps of UD fiber at bonding area ONLY.

Same applies to lugged constructions: from ( my ) mechanical point of view those are even better; mono pieces in highest streeses areas plus round-ish tubes... sounds good for me.

But ALWAYS mono-continuos construction will be better . Molding even very complicated shapes as mono has been solved while ago, and is less complicated than many companies insist it is. It's absolutely most expensive, so ... as always, if you have Q "why?" , it's because of money .

[wingguy]

Stefano, you want statistic, a voila : I had 3 BMC, 2 carbon frames, 1 bonded and 1 with mono-chainstay. Those bonded broke after 200km... so failure ratio is 50% for carbon frames , and 100% for bonded chainstay frames.

That's really dumb.

If you say, they're not weaker/ do not break more often- GIVE US STATISTIC DATA proving that. Lack of it, make my thesis valid. ( sounds familiar ? ) . Prove , if I'm wrong. If you can't, I'm right

That's really, really dumb.