Are ** milled ** Fork Crowns less strong than original Crowns made from ** die-casted ** Aluminium??👀⁉

by kraeMit | Sep 16, 2024 | Allgemein

Short : NO !!💯    =▶ Alu 7075 T6 milled Crowns are MUCH stronger‼🚀

Long :
I was asked about the strength of the Marzocchi Crowns I already did (all >=1997 : Jr. T Top Crown, Monster Full Flat Top Crown), the ones I had already created 3D models for (Monster’s, Shiver DC, some 888, etc.) and the ones are in progress (some other 888’s + 2. Gen Monster’s).

A comparison of the strength between a 7075-T6 aluminum part and the same part made using the die casting process reveals significant differences in mechanical properties.

Let’s look at the details: 

1. 7075-T6 Aluminum (forged or rolled)

Alloy: 7075 is one of the strongest aluminum alloys, commonly used in aerospace applications. In the T6 condition (solution heat-treated and artificially aged), it reaches its highest strength.

Typical strength (T6 condition):

• Tensile strength: approx. 570–640 MPa
• Yield strength: approx. 480–510 MPa

Hardness: Very high, suitable for applications with high mechanical stresses.

Structure: Parts made from 7075-T6 through forging or rolling have a dense and homogeneous microstructure, leading to very high strength.

2. Aluminum part made using the die casting process

Manufacturing process: Die casting allows for the production of complex shapes and high-volume output. In die casting, molten aluminum is injected into a mold under pressure, which can result in some structural weaknesses.

Alloys: Commonly used die-cast alloys are typically aluminum-silicon alloys like AlSi10Mg or AlSi12, which have lower mechanical
properties compared to 7075.

Typical strength of die-cast parts:

• Tensile strength: approx. 250–350 MPa
• Yield strength: approx. 150–250 MPa

Defects: Die-cast parts can have internal defects like porosity and shrinkage, which further reduce strength.

Strength comparison:

7075-T6 (forged/rolled): This alloy has much higher strength values compared to a typical die-cast part. The tensile and yield strengths of 7075-T6 are significantly superior because the microstructure is denser and more uniform due to the forging or rolling process.

Die-casted parts: These generally have lower strength due to casting defects and the fact that less high-strength alloys are often used. Even if 7075 were used in die casting, its strength would still be lower due to the inherent defects in the casting process.

There is also a huge difference because of the geometry I have optimized, because:

– the die-casted parts need to have some kind of hollow areas from the bottom, because the process needs to have almost the same wall thickness for the parts to avoid cracks in cooling down.

– the milled fork crowns have been changed + optimized : I filled some of this hollow areas you can see from the bottom which will result in better strengrth overall!💯 (-> picture)

Conclusion:

A 7075-T6 aluminum part (forged or rolled) is significantly stronger than the same part made using the die casting process. The difference in strength is particularly notable because the forging or rolling process produces a much more homogeneous and defect-free microstructure.💯🙏🚀

Evolution of Marzocchi Steerers 👀✨🤙

by kraeMit | Sep 4, 2024 | Allgemein

I like to show you, how Steerers have been developed in the last ~35 years. Marzocchi starting in 1989 made rock solid HQ CroMo steerers in 3 sizes (1″, 1 1/8″, 1 1/4″) for all the XC forks (you know : StarFork, … XC500, XC600 etc.).

And when evolution of suspension forks continued, forks got more weight and users demand was about some weight tuning in steerers.
You know when bullet-proof Bomber’s appeared on the market 1997+ and following Marzocchi developed in weight optimizing modells like BAM, Alloy and others.

Over the year Marzocchi continoued developing different geometries – keep in mind it was a company of developers, not such wtf-buy-it-only-and-don’t-care-get+make_more_money-companies we have today.

The 3D geometry of a steerer needs to handle various level and vectors of forces. In the beginning this have resulted in ‘simple’ straight tubes, the later it became some optimized conical design – btw. same happened with Marzocchi stanchions!

Aluminium 7075 T6 is a fascinating material – heavy used in Aero Industry, Rocket Science and more. It’s high quality variants like ‘T6’ are best choice to repro such steerers.
I’m doing now length up to 280mm, that’s just to save some production costs. The original have been >=300mm.

The marked green one but black is the one which is in production now.👀🖐

FYI : There is one strong Marzocchi CroMO Steerer missing in the picture, I show you somewhen later. It is a variant with another additional inner CroMo core which is pressed into the steerer to avoid dynamic distorsions which results in cracking in all other modern brands, but not for the time Marzocchi rulez the world.
Seen 1st in a Marzocchi 66.🙏🤗.