Can a car wheel hub made of 7075 instead of steel ? 3

[Noxx]

I know that wheel spacers/adapters are made of aluminum, but could a wheel hub made of aluminum too ? I haven't seen ali hubs for cars, only for motorcycles.

This could be a great way to reduce un-sprung weight and rotational mass.

Are there any reasons not to use aluminum (like 7075-T6) instead of steel ?

 

[tbuelna]

It is possible to make a wheel hub from 7075-T6 aluminum, and it is done for some racing applications like this. However, for most production vehicle applications steel still seems to give the best compromise of cost/weight/fatigue life/etc.

 

[Noxx]

Thanks for the input!

My car is half of a road car and half of a race car. I'm at 750kg now and trying to get to 700kg.

 

[GregLocock]

There's no reason in principle why the bulk of that part couldn't be made from aluminium. But there are easier parts to lightweight, and for a production car the cost of getting the strength and durability of this safety critical component back to the same as steel is probably prohibitive.

Cheers

Greg Locock


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[Tmoose]

Fits of Ball/roller (and even inserts, like plain rod and main Bearing) with aluminum housings can be problematic, due to differences in thermal expansion.

For long life in severe service the addition of an intermediate iron or steel insert housing in engines and hubs are recommended specifically to reduce the thermal expansion effect.

Harley crankcase half with cast in steel insert.

http://www.knuckleworks.com/images/cases/ph48i.jpg

 

[CoryPad]

As long as the parts are not exposed to a corrosive environment (like road deicing salts), then 7075-T6 should be suitable. If the vehicle is exposed to a corrosive environment, then a better option is 7075-T7X.

 

[GregLocock]

I'm assuming that it will be engineered, not just a copy of the steel part. Otherwise, yes, the bearings will fall out under braking.

Cheers

Greg Locock


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[Noxx]

I'm assuming that it will be engineered, not just a copy of the steel part. Otherwise, yes, the bearings will fall out under braking.

I won't engineer the part (except for the CAD work) as it's not my field of expertise.

Why do you think the bearing will fall out under braking ? I was under the impression that under braking (and heating) the thermal expansion would exert even more pressure (preload) on the bearing.

Here you can see the upright which is already made of aluminum. I was lucky to buy one of the early cars who still had that.

 

[EdStainless]

The Al will get larger in ever direction as it heats, hence the hole will get larger.
The other issue to look at is impact toughness. In order to do this correctly in Al the part would be designed to carry the loads and then it would be forged.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[Tmoose]

RE: housing fits. section 3.3 here -
edit with proper link

http://www.nsk.com.br/upload/file/nsk_cat_e728g_3.pdf

That is one fragile looking piece.
What is the application?
Can you post pix or linx to the rest of the suspension?

 

[GregLocock]

There's nothing wrong with aluminium spindles, we use them in production on an SUV. BUT if they are to live for a long time they need to be designed and manufactured in a different fashion to a steel part, and frankly, the lack of ductility in the higher grades/heat treats of aluminium mean they are a bit tricky when it comes to smashing into potholes and other facts of life. The lower grades are a bit too weak to give you a weight/cost save. I wouldn't touch a billet part for road use, forging is the proper solution.

One big change is that we don't use separate wheel bearings, we buy complete hub units,

http://www.au.nsk.com/Products/Automotive_Products/Hub_Unit_Bearings

which are effectively a cassette with both bearings, pre adjusted, which can be pressed or bolted into the aluminium spindle. Hub 1 designs can still suffer from the press fit problem under braking. It is resolvable, with appropriate tolerancing and machining practices. Establishing those fits needs experimentation and/or Lame's equation.

http://www.mydatabook.org/solid-mec...-cylinders-and-spheres-using-lames-equations/

for an example.


Cheers

Greg Locock


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