from Rookie’s keyboard,
Hello, friends
This post is dedicated to carbon frame assembly/architecture.
There are three main ways to assemble a carbon bike:
a/ via gluing (most common)
b/via lugs
c/ via molding
Today, I will compare a/ and b/.
For financial reasons, most carbon frames today are built by gluing together a few separate pieces.
Monocoque frames, however, are a single unit produced via a molding protocol.
The result is a unified frame with consistent flow and strength.
Lugged frames go back to the steel road bike era.
The lugs are sleeves in which the tubes of the frame are inserted.
Lugs can also be used for the production of carbon frames.
The Strength of Monocoque Frames
- Strength
When all other variables are equal, a monocoque frame should be stronger because it doesn’t have joints.
- Light
The absence of a joint, epoxy, and lugs allows the frame to be lighter. The weight savings are minimal and matter only when competing on the highest level or when trying to produce the lightest possible frame.
- Appearance
Monocoque models have a consistent flow resulting in a unique look that cannot be replicated via other production methods.
- Faster Production
The molds are expensive but once acquired, they speed up the production process because there is no need to glue the frame together.
The Negatives of a Monocoque Frame
- Alignment
Since monocoque frames are produced as a single unit, there’s no chance to realign the frame once it’s complete.
There’s no room for error and the manufacturing process requires high-end molds without inaccuracies.
- Pricey
Monocoque models are more expensive to produce.
The molds have to be of high quality to avoid warping of the frame.
And for that reason many producers stay away from true monocoque production to limit the cost of their products.
Lugged Frames = The High IQ Economic Choice
Lugged frames are not limited by molds and allow easier production of different sizes. This property alone makes them a logical choice when minimizing costs.
Looks
Even though carbon is a modern material, the lugs make the frames similar to a classic steel model.
One can say that lugged carbon frames act as a bridge between the past and the present.
Errors Can Be Corrected
Since lugged frames have joints, the builder can fix a potential misalignment during the manufacturing.
Stress Points (a negative side)
The ends of the lugs stress the tubes when the frame flexes. This creates a stress point that can eventually damage the frame. Carbon is strong, but it’s not tough and resilient. It can’t take external stress as well as steel.
Not All Monocoque Frames Are Created Equal
A true monocoque frame is produced as a single unit. But not all frames labeled as monocoque fit these criteria.
Sometimes, only parts of the frame are produced as a monocoque piece and are later joined together.
A non-true-monocoque frame is not bad, though. It depends on the overall quality, the used materials and the craftsmanship behind the process.
Stiffness
A monocoque frame can be stiffer than a lugged one, but ultimately, the stiffness of a frame depends on the geometry and the fiber orientation. A lugged frame can also be stiff.
But when all other variables are equal, the monocoque frame will have greater stiffness due to the absence of joints and glue.
In conclusion
Most people won’t feel a difference between a standard (glued or lugged) carbon frame and a true monocoque model.
The structural dissimilarities aren’t big enough to create a substantially different riding performance.
The main differentials are the production process and the design.
But the buyer is rarely concerned with the manufacturing behind a product. And from his perspective, the deciding factors are often the price point and the appearance.
Since true monocoque frames are usually more expensive, it’s up to you to decide whether the appearance of the frame is worth the extra investment.
Me?
Honestly?
I prefer steel and aluminum over carbon.
Until next time,
Rookie
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