38 replies to this topic

[TempesT]

Hello torry fans,

Im deep into an expensive brake upgrade and I was going to get some custom Aluminium hubs made up.

The hubs have been designed to fit HQ stubs and will be ordered undrilled so people can put whatever stud pattern (and stud size) they want on them. The centre spinal would be set at a diameter as to allow Hubcentric wheel fitment with a spacer ring on most rims out there.

The design themselves is very similar to those available from The German and they will be constructed from 7076-T1. The big difference is that I want to keep the price at about $300 if not just under that mark.

So post up any questions or opinions.

Cheer
jimmy

[TempesT]

Chop like any brake / suspension upgrade they need to be correctly certified by an engineer if you intend to run them on the street.

Yeh chop 6061 or 7076 heat treated to T6 standard will suffice; there is plenty of data available on the properties of both materials online which I recommend anyone interested to compare against those for steel. These two materials are widely used as the billet alloy "of choice" for this type of application.

The level of interest will determine where the final spindle diameter ends up. If there is interest to have it as low at Torana size then that can be arrange and custom centre bore spacers will be needed.

However i don’t see many people wanting to run Torana rims with these hubs. As such it would probably end up just under the smallest commodore diameter.

I Hope that answered your queries.

jimmy

[orangeLJ]

Id definitely be interested in a set to throw on my HX ute if they suited my needs down the track.

[TempesT]

Little update.

I have had some quotes come back and I can confirm that they will be made of 7075, which is an aircraft grade material.
http://asm.matweb.co...assnum=MA7075T6
heaps more info out there on the properties ect.

So hopfully I will be able to make some revisions to my drawing this week and then run it the ANSYS. This FEA (finite element analysis) will give me a comperhensive visual depiction on how the actual design will hold up to the forces experienced by the wheel hub.

[Toranamat69]

Make sure you design the part within it's fatigue limit as this will be the limiting factor for a highly loaded part like this made in Al Alloy.

You are correct that the 7075 - T6 is at least as strong as steel but steel has a far higher fatigue limit than any alloy under the same conditions.

You may well find that the part will have to be 'lifed' if your calcs show the deflection under load is too high - that is if you calculate it.

These will most definately be exposed to constant cyclic loading.

I think personally I will go for steel ones but hate to see some of these fail if not designed properly.

[TempesT]

True, true, true

and thats the point of the FEA to asertain if it is a safe option

Quick question of interest, alloy wheels I have seen them made of 6061, I assume their lifecycled?

Edited by TempesT, 15 November 2011 - 08:22 PM.

[Toranamat69]

Good question on the alloy wheels. Alloy does not actually have a fatigue limit per se as steel does but the time for cracks to occur and failure becomes so long it is essentially infinite.
It would be very interresting to see what number of cycles a test mule alloy wheel would theoretically fail at.



I know my dragway wheels have a fairly serious amount of alloy connecting the hub and rim and mine are about their most 'open spoked' design out of Dragway's collection so some of their other designs would have far more material in them again over what mine have.

To quote wikipedia 'An important structural limitation of aluminium alloys is their lower fatigue strength compared to steel. In controlled laboratory conditions, steels display a fatigue limit, which is the stress amplitude below which no failures occur - the metal does not continue to weaken with extended stress cycles. Aluminum alloys do not have this lower fatigue limit and will continue to weaken with continued stress cycles. Aluminium alloys are therefore sparsely used in parts that require high fatigue strength in the high cycle regime (more than 10⁷ stress cycles).


For wheels you can usually make the cross sectional area bigger(within reason), hence reduce the stress on the wheels, for something like a hub, it is dimensionally limited i.e. it has to fit into that slot to do the job.

[TempesT]

It will be interesting to say the least.

I have found some interesting information.

1. The clamping force between the wheel and hub will help in reducing the formation and propagation of cracks

2. the tempering to T6 will counter the stresses that cause fracturing.





I will just have to see how the design reacts when i run it thru ANSYS.

I

[TempesT]

Also for those that are reading and are a little lost on ANSYS:

its an analysis tool and a very good one at that. It takes a CAD drawing and you then set the forces experienced by that part. You then run the program and it will give to the stress's ect experienced by that part under operation. This is depicted as colour regions ranging front blue = good to red that is bad.


The deflections are extruded, for the cycles you set you’re trying to have no red areas. Red areas are point of high stress where cracking will start and propagate from.

[dattoman]

Nerds

Make it... bolt it up... thrash it till it breaks... thats your fatigue point

They have been making alloy hubs out of lesser grades than 7075 for years in motorsport applications
And yes they are "lifed" and replaced semi regularly
So too the disc hats and calipers

Accept that things need replacing regularly... your not building something that will last a metric lifetime

[Toranamat69]

I am, I like my stuff to work and work for ages. If only I can make them stay shiny too.

My normal regime is to give something new I make the full blast test. If it works good, if it breaks, it wasn't strong enough.

I would prefer not to find this out as a forged alloy wheel overtakes me - hence why I won't be using the alloy hubs.

I agree though, often it is easier to build and test rather than analyse to death but that is a bit hard to come up with anything for a component life without doing an FEA. Even testing one to failure is only a statistical sample of 1 and will not really tell you that much useful about when the next 10 will fail.

[ls2lxhatch]

It would be worth drawing up the steel hubs and running them through ANSYS as a baseline.

It would also be worth considering making the disc hat part of the hub as this would be considerably stronger in the wheel stud area.

You may also want to consider how you will legally cover your arse if you plan to sell the hubs. At a minimum I would machine into the hub the words “off road use only”.

In theory there is a performance benefit from lighter hubs but I doubt it would be a measurable improvement on a dedicated race car. There are much bigger weight savings to be had in disc and rim selection. The benefit on a street car would be purely cosmetic.

[ls2lxhatch]

What braking benefit would there be from an alloy hub?

[orangeLJ]

I think Chopper is reffering to the initial point of heading along this path, machining hubs to suit an expensive brake upgrade.

[TempesT]

hahaha lads we are all getting ahead of ourselves.

The truth is all parts have a life cycle, this thread has raised some good points. For me the comparison between the hub run thru ANSYS as alloy then steel will be the real test. Of corse the accuracy of the ANSYS system will be how good my modelling equations are... that.... I havn't even looked at yet (Friday when I am in the office maybe).

Now I can get these made from steel, cheap.... silly cheap but the only driving factor outside of the price is if I don't like what UPC has sent me. Anyway I dummy up the AP's on the 046 hat this weekend...

[dattoman]

Cooler bearings too

[TempesT]

lol.

Im trying to drop 10kegs b4 x-mas.....

who woulda thought this would turn into a weight loss thread