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mjan22640 | 10 months ago

> Also how they use aluminum for the connecting rods instead of stronger and stiffer metals like titanium

The 7000 aluminium alloys are similar to titanium in strenght/weight

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magicalhippo|10 months ago

Yes but they have lower Young's modulus[1] so compress more under the same force. Thus acting as a shock absorber to reduce peak loads on the rod bearings.

Again no expert but from what I can see, high-end aluminum rods can use 7075 aluminum[2], which has a Young's modulus of about 72 GPa, while titanium has a modulus of about 105 and up[3][4], depending on grade.

At least that's my understanding.

[1]: https://en.wikipedia.org/wiki/Young%27s_modulus

[2]: https://www.enginebuildermag.com/2017/03/racing-rods-builder...

[3]: https://titanium.com/alloys/titanium-and-titanium-alloys/gra...

[4]: https://titanium.com/alloys/titanium-and-titanium-alloys/ti-...

mjan22640|10 months ago

An aluminium part with 105/72 cross section of the titanium will have the same modulus and incidentally the same weight.

Aluminium is also significantly cheaper, and easier to machine.

Titanium (or high strength steel, which is the strongest both per area and per weight and also the most expensive and difficult to machine) would be used where the volume of the part would be a concern.