Road Bike, Cycling Forums banner
21 - 39 of 39 Posts

·
'brifter' is f'ing stupid
Joined
·
15,549 Posts
Monocoque is a construction technique that utilises the external skin to support some or most of the load. This is as opposed to using an internal frame or chassis that is then covered with cosmetic body panels.
i'm guessing you're a race car person, yeah?
 

·
Registered
Joined
·
11,474 Posts
Monocoque is a construction technique that utilises the external skin to support some or most of the load. This is as opposed to using an internal frame or chassis that is then covered with cosmetic body panels.
Precisely right. Of course and as said by others, you could apply this engineering definition to all carbon fiber reinforced plastic (CFRP) bicycle frames. What makes discussions like these contentious is the fact that the bicycle marketeers have taken the term "monocoque" and made it mean whatever they want it to mean. But this sits square in the tradition of bicycling advertising copy: lots of bunk masquerading as engineering or science.
 

·
Registered
Joined
·
2,078 Posts
The Impec is made of machine made CF tubes joined by lugs. It is mostly made by a computer controlled machine. It's pretty slick engineering.

IMO, tube-to-tube construction (Sarto, Cyfac, Guru, etc.) is not considered monocoque.
The same as Look and Time were doing ten years ago?
 

·
classiquesklassieker
Joined
·
3,106 Posts
The same as Look and Time were doing ten years ago?
Are you referring to the Impec/BMC method or the tube-to-tube? LOOK and TIME were doing lugged construction until a few years ago, they started with lugs and tubes, which are then joined/bonded.

TIME advertised that their tubes were made in-house. But as far as I can tell they still start with lugs and tubes.

And if I understand the BMC/Impec method, they start with tubes, put them on a jig, and then weave/build lugs around exactly how the tubes are supposed to be supported.
 

·
Registered
Joined
·
6,820 Posts
Discussion Starter · #25 ·
Are you referring to the Impec/BMC method or the tube-to-tube? LOOK and TIME were doing lugged construction until a few years ago, they started with lugs and tubes, which are then joined/bonded.

TIME advertised that their tubes were made in-house. But as far as I can tell they still start with lugs and tubes.

And if I understand the BMC/Impec method, they start with tubes, put them on a jig, and then weave/build lugs around exactly how the tubes are supposed to be supported.
I'm wondering what's the advantage of building the Impec like they do (if what you said is true). Why put lugs in a jig and build lugs around them? Surely lugs can be built outside of a jig if the correct specifications are given. I wonder if it's easier or harder to build a lug around a tubeset set in a jig. Is there something about this building technique that gives the frame any advantage over the traditional lug method?
 

·
Registered
Joined
·
6,820 Posts
Discussion Starter · #26 ·
Precisely right. Of course and as said by others, you could apply this engineering definition to all carbon fiber reinforced plastic (CFRP) bicycle frames. What makes discussions like these contentious is the fact that the bicycle marketeers have taken the term "monocoque" and made it mean whatever they want it to mean. But this sits square in the tradition of bicycling advertising copy: lots of bunk masquerading as engineering or science.

You're right about advertising bunk in the bicycle industry. Sure the improvement is there, sure the "technology" is there, but ultimately they are a minuscule contribution to the overall performance of its rider. But leave it to the bicycle marketeers to make these improvements seem like Nobel prize stuff.

I every time I read an ad of a high end racing bicycle, goes something like
- tapered head tube for stability
- oversized tubes for rigidity and lightweigt
- oversized bottom bracket for ultimate flex free power transfer
- shock absorbent rear triangle design for all day comfort

... and i'm thinking to myself... maybe Eddy Merckx and his contemporaries were racing on noodles back in the days... and surely Eddy The Animal must be producing girly wattage.. because surely today's Joe Weekend Warrior would easily break those flexy noodly steel frames with girly 1" steerer tubes that Eddy was riding on.
 

·
Registered
Joined
·
5,360 Posts
I'm wondering what's the advantage of building the Impec like they do (if what you said is true). Why put lugs in a jig and build lugs around them? Surely lugs can be built outside of a jig if the correct specifications are given. I wonder if it's easier or harder to build a lug around a tubeset set in a jig. Is there something about this building technique that gives the frame any advantage over the traditional lug method?
The tubes are woven onto a mandrel. Any modulus of fiber can be put anywhere in the tube, since instead of using pieces of fabric they are designing strand by strand. Theoretically the labor cost should be lower, since cutting pieces of fabric and laying them in a mold can be very time consuming.
The weaving may someday allow for identical looking frames to have different levels of stiffness or weight, by changing the mix of fibers. A steel builder can use an SP downtube in an SL frame to stiffen it. The Impec system may allow this kind of customised ride tuning.
Molding the lug around the tubes should make them more homogenous/solid. Brushing glue onto a tube and sliding it into a lug may allow voids or bubbles. That shouldn't happen when molding.
From a manufacturing point, the biggest advantage would be consistency of product and reduced labor cost.

Just an example, I visited a small factory that made knitwear. They had a machine that made socks with logos (Nike, Adidas, sports teams etc) and pictures ( Disney characters). They machine was huge, with large spools of thread hanging from the ceiling. An operator picked a design from a computer screen and this thing started weaving socks with the pattern, and it took about 30 seconds to make a sock. It made 24 socks at once.
After finishing one batch, the operator picked a different pattern, no physical contact with the machine was necessary. Just a selection from the menu.
With this system one person was able to make thousands of socks in a shift, of several different designs.
They had a similar machine but bigger for making knit sweaters.
If BMC could get something like that up and running it would be awesome. Custom tuned carbon frames for your weight, size and riding style. Carbon fiber bicycle manufacturing is still in its very early stages. It's going to get far more sophisticated in a few years.
 

·
classiquesklassieker
Joined
·
3,106 Posts
The tubes are woven onto a mandrel. Any modulus of fiber can be put anywhere in the tube, since instead of using pieces of fabric they are designing strand by strand. Theoretically the labor cost should be lower, since cutting pieces of fabric and laying them in a mold can be very time consuming.
The weaving may someday allow for identical looking frames to have different levels of stiffness or weight, by changing the mix of fibers. A steel builder can use an SP downtube in an SL frame to stiffen it. The Impec system may allow this kind of customised ride tuning.
Molding the lug around the tubes should make them more homogenous/solid. Brushing glue onto a tube and sliding it into a lug may allow voids or bubbles. That shouldn't happen when molding.
From a manufacturing point, the biggest advantage would be consistency of product and reduced labor cost.
Thanks for the explanation. Ignoring costs, does the Impec/BMC method yield a better product or degree of customization compared to tube-to-tube with hand-cutting and hand-laying of carbon sheets/kevlar/glue/etc.? Or, is the latter limited by the resolution of fabric, instead of strands of fiber/kevlar?
 

·
'brifter' is f'ing stupid
Joined
·
15,549 Posts
Thanks for the explanation. Ignoring costs, does the Impec/BMC method yield a better product or degree of customization compared to tube-to-tube with hand-cutting and hand-laying of carbon sheets/kevlar/glue/etc.? Or, is the latter limited by the resolution of fabric, instead of strands of fiber/kevlar?
not sure about 'better' but i'll tell you one thing it isn't...lighter. the one i built was a 53 w/ the taller head tube and it was about 1350g. the fork was pretty hefty as well. the lugs are built in halves and bonded to the frame tubes in the mold after the tubes are woven around the mandrels to get the proper mix/pattern of fibres and the shape of the tubes.
 

·
Registered
Joined
·
5,360 Posts
Thanks for the explanation. Ignoring costs, does the Impec/BMC method yield a better product or degree of customization compared to tube-to-tube with hand-cutting and hand-laying of carbon sheets/kevlar/glue/etc.? Or, is the latter limited by the resolution of fabric, instead of strands of fiber/kevlar?
There is great potential for customisation...in a few years.
Tuning a carbon structure by varying the individual threads is far more effective and efficient than changing swatches of fabric. Currently, a builder will have to fetch a roll of fabric, cut out the piece they want, then roll up the fabric and put it back in storage. If the fiber modulus could be selected right in the weaving stage it would save lots of time.
Hand cutting always requires a margin of error. Every piece has to be bigger than necessary in case the cutter snips off a bit too much. That is why more expensive frames (McLaren eg) cost more. The cost goes way up because the person cutting goes much slower and more carefully, and each swatch is more carefully positioned in the mold. Most frames could easily be 10% lighter if these steps were taken, but the labor cost could double.
In manufacturing, a huge amount of time is wasted when people have to go to storage areas and get an odd item, or stop regular production to custom make one little piece. That is why a loom like BMC's has so much potential, not only could it offer tuning, it can make the whole process more efficient.
 

·
Registered
Joined
·
6,820 Posts
Discussion Starter · #31 ·
not sure about 'better' but i'll tell you one thing it isn't...lighter. the one i built was a 53 w/ the taller head tube and it was about 1350g. the fork was pretty hefty as well. the lugs are built in halves and bonded to the frame tubes in the mold after the tubes are woven around the mandrels to get the proper mix/pattern of fibres and the shape of the tubes.
1350g for a 53cm frame???
 

·
Registered
Joined
·
1,923 Posts
The Impec I saw at a local shop also has a VERY slack geometry. If you like a bike that handles more like a ferrari, then it is not the bike for you.
 

·
Registered
Joined
·
2,542 Posts
I can't find the videos right now, but they used to have videos that showed most of the Impec fab. The tubes are carbon weaves done 100% by machines. Look or Time doesn't do this, although they all 3 have carbon lugs. Supposedly each Impec tube is 100% identical.
 

·
Converted Runner
Joined
·
691 Posts
Okay I haven't seen anybody say it (but then again I did skim through some parts).

The term "monocoque" is used to differentiate between frames that are molded in one, two, or three large pieces, from tube-to-tube style frames (either lugged or wrapped). It is rather difficult to mold the frame as one piece and as such we usually see the front triangle (head tube, top tube, and down tube) molded together, and then the rear triangle (BB, seat tube, and seat/chain stays) is glued to it. By minimizing any unnecessary wrappings or gluing the bike is a more solid piece. However, you are stuck with "off the shelf" sizing since moulds are obscenely expensive. Tube-to-tube bikes (i.e. Cannondale's super six) allow for custom geometries - see Peter Sagan's bike.
 

·
Registered
Joined
·
1 Posts
I'm no structural engineer, but I'm under the impression that a monocoque is structure is constructed without fusing tobegher separate "halves".. in other words, the structure is one contiguous piece of fabric

Is there a truly monocoque frame out there?

For example, if I look at a Tarmac top tube, I can clearly see a line indicative of 2 piece joining together at the line. I also don't believe the Trek Madone is monocoque frame either (they are lugged underneath all that outter carbon layers).

Anyway, I'm curious if there is a truly monocoque frame out there in which everything from headtube all the way to the rear triangle.. is constructed as one contiguous piece without any fusing or bonding separate pieces.

Just curious.
The KIRK Precision road bike and the KIRK Revolution MTB we’re both genuine monocoque frames. Both frames made from a single magnesium alloy moulding. Check them out google ‘Kirk bicycles’
 

·
'brifter' is f'ing stupid
Joined
·
15,549 Posts
The KIRK Precision road bike and the KIRK Revolution MTB we’re were both genuine monocoque frames. Both frames made from a single magnesium alloy moulding. Check them out google ‘Kirk bicycles’
ftfy...And thank god you showed up to clarify this whole situation...8 and half years after the fact. Fantastic first post.
 
21 - 39 of 39 Posts
Top