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DO NOT USE HUB ADAPTORS-PHOTOGRAPHIC PROOF 

 

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 Post subject: Re: DO NOT USE HUB ADAPTORS-PHOTOGRAPHIC PROOF
Posted: Thu Oct 01, 2009 9:45 pm 
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Indeed you did but it doesn't make the calculations any less artificial. I'm not arguing the bolts aren't strong enough for the task. They obviously are most of the time since hub adapter or not they're often the only thing holding the wheel on. But it's still a very misleading way of thinking as the shear forces can still be potentially much higher. f=ma and sometimes even if briefly 'a' can be very high for a bolt.

 

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 Post subject: Re: DO NOT USE HUB ADAPTORS-PHOTOGRAPHIC PROOF
Posted: Thu Oct 01, 2009 11:16 pm 
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Yeah I agree that its not perfect, but in a lot of situations, assumptions are required, which is what I did to demonstrate the strength of wheel bolts.
I highly doubt that purely from cornering that there would even be close to full car weight on one wheel. One example I found froma short search suggested a weight transfer ratio of 1.4 or something from one side to the other.
Hitting a bump would induce a higher load, but shock loading is something different and most steels can handle higher loads when they are applied in shock.

My demonstration may be very inaccurate, but if anythig I'd say it's inaccurate on the side of safety.

 

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 Post subject: Re: DO NOT USE HUB ADAPTORS-PHOTOGRAPHIC PROOF
Posted: Fri Oct 02, 2009 12:27 pm 
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Yeah it probably is. In the end I guess the problem is cheap studs that don't live up to the rating they claim. I just removed a set of hub adaptors and put some e series offset back on. The studs on the adaptor def looked worse for ware compared to the studs on the hub.

 

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 Post subject: Re: DO NOT USE HUB ADAPTORS-PHOTOGRAPHIC PROOF
Posted: Fri Oct 02, 2009 12:32 pm 
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I am looking at getting some AU+ offset rims (do not exist in E-series offset) so I will need to use adaptors. The first thing I will do is take out the supplied studs and replace them with 1/2" Ford studs.
Originally when I was thinking about getting adaptors, I was concerned about the material quality of the adaptor itself, and was going to get my own made up from 4140 (overkill) but now I see there is very little need for that and 1045 will be fine (which is what most are made from I believe).

 

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 Post subject: Re: DO NOT USE HUB ADAPTORS-PHOTOGRAPHIC PROOF
Posted: Fri Oct 02, 2009 12:52 pm 
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MADXF wrote:
I am looking at getting some AU+ offset rims (do not exist in E-series offset) so I will need to use adaptors. The first thing I will do is take out the supplied studs and replace them with 1/2" Ford studs.
Originally when I was thinking about getting adaptors, I was concerned about the material quality of the adaptor itself, and was going to get my own made up from 4140 (overkill) but now I see there is very little need for that and 1045 will be fine (which is what most are made from I believe).


just make sure you buy GOOD QUALITY adaptors in the first place, then there will be no need to replace the studs.

 

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 Post subject: Re: DO NOT USE HUB ADAPTORS-PHOTOGRAPHIC PROOF
Posted: Sat Oct 03, 2009 11:43 pm 
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MADXF wrote:
If the centre hub was to actually carry the load of the wheel, it would need to be a super hard press fit.

Lets look at some actual figures....

Car weight = 2000kg = 19620 N
Extreme case loading (all weight on one wheel) = 3924 N / stud
Shear capacity of M12 grade 8.8 bolt = 39,000 N
That's a safety factor of 8.9 with having all the weight of the car on one wheel.

Sure its a simplified look at it, and there would also be tension placed on top few studs (imagining the wheel trying to lean over during cornering), but there would also not be the full load of the vehicle on ONE wheel.

If you look into the friction of the joint between wheel and hub face you end up with a similar picture.
Coefficient of friction of aluminium to mild steel = 0.61
Ajax bolt guide Recommended tightening of a 12mm Grade 8.8 bolt = 77 Nm which converts to 31800 N tension.
Total tension at joint of ONE wheel = 159,000 N
Friction force of ONE wheel = 159000*0.61 = 96990 N
Car force (TOTAL) = 19620 N

So again if we put all the load on ONE wheel the safety factor is 4.9.


Now this is looking at these things separately.
If the vertical load is never enough to overcome the friction then the studs will NEVER take any load in shear.
If the vertical load does overcome the friction, then the studs would start to take the load. Not all of it though as the friction would still be assisting.


Now most wheel studs are what's called 'grade 8' which is basically the imperial version of the metric 'grade 10.9'
I didnt use grade 10.9 because I wanted to show the worst case situation, and th ebook I have doesnt show the shear strength of grade 4.6.




Ok, now go learn the more advanced engineering principals and come back and tell us what you just said is still true.
Add in dynamic loads (as well as the tension forces on the studs due to lateral loads during cornering) and some corrosion and fatigue factors. all your calculations are good for is that the car can carefully be balanced on one wheel without it falling off. Im not going to bother quoting any numbers here as to give a truly accurate representation of what is going on i would have to go through textbooks.

The vibration problems reported by people on cars with poorly fitting locating rings outlive the problem exactly, the wheel is flexing the studs (lateral G's will reduce the clamping force exerted by the studs) allowing vibrations this flexing is doing mechanical work on the studs, this mechanical work is probably within the elastic deformation range of steel ( so they will never plasticly deform) BUT it is conceivable that the stud will eventually crack through fatigue this crack will propagate until the yield point is reached (being high tensile there is probably a minimal region of plastic deformation)

 

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 Post subject: Re: DO NOT USE HUB ADAPTORS-PHOTOGRAPHIC PROOF
Posted: Sun Oct 04, 2009 4:42 pm 
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JOSE wrote:

Ok, now go learn the more advanced engineering principals and come back and tell us what you just said is still true.
Add in dynamic loads (as well as the tension forces on the studs due to lateral loads during cornering) and some corrosion and fatigue factors. all your calculations are good for is that the car can carefully be balanced on one wheel without it falling off. Im not going to bother quoting any numbers here as to give a truly accurate representation of what is going on i would have to go through textbooks.

The vibration problems reported by people on cars with poorly fitting locating rings outlive the problem exactly, the wheel is flexing the studs (lateral G's will reduce the clamping force exerted by the studs) allowing vibrations this flexing is doing mechanical work on the studs, this mechanical work is probably within the elastic deformation range of steel ( so they will never plasticly deform) BUT it is conceivable that the stud will eventually crack through fatigue this crack will propagate until the yield point is reached (being high tensile there is probably a minimal region of plastic deformation)


I know it's missing a lot of variables for 'real world', I said that.
I think the dynamic forces, the tension and the fatigue factors would still fall within the safety factors shown by my original basic calcs. Remember not only was it a car balancing on one wheel, it's a car that weighed 24.9 Tonnes balancing on one wheel. In AS1418 (crane design) if the ratio from actual stress to yeild stress is low enough, fatigue can be ignored in certain situations.

I'd like to do a more in depth analysis, but I'm missing a lot of information like typical fatigue and corrosion factors for a vehicle, the sort of g's a car on good road tyres would see and I dont have access to the Australian standards for vehicle design. Then there's spring rates and damping that will affect the dynamic loads.

I looked at the problem with the tools I have. It may be overly simplified, but sometimes its the best way. In this case, I dont know.

 

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 Post subject: Re: DO NOT USE HUB ADAPTORS-PHOTOGRAPHIC PROOF
Posted: Mon Oct 05, 2009 1:58 pm 
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I also have a set of adaptors that came from Tempe a few years back. The quality of stud that came with them was definately below par. I got the front guards rolled about a year ago and the people who did it snapped 2 of them. They told me that it happened when they undid them, although they waited til the wheel was going back on to tell me about it. I reckon it happened as they put them on with the rattle gun. I went straight out and bought a set of 20 which was a bit of a pain in the a*** cos they were a hard stud to match, but found them after visiting a couple of different shops. Just after a visual inspection, you can see that they are very poor quality compared to the standard ones after a couple of years use.

I've never had any problem with them apart from this and my car gets driven hard.

The only time I've ever seen a hub adaptor fail was years back when I was watching a Targa-style race when an Audi TT lost a wheel. A cop nearby walked up to the camera with a couple of bits of shattered adaptor, saying that's why they're illegal.

 

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