Pardon me, I am a complete novice - custom front hubs

[pantswagen]

I am having machined some custom front hubs
basically to suit a 1975 vw van, so single row taper bearings.
now these are steel, what I am having made are in alloy
they are replicating a porsche stud pattern, the porshe hubs they are replicating are cast alloy
my concerns are, which grade material should i use

the other concern being, they are having studs pressed in as the standard ones, I wanted them in steel, but the machinist and I know its easier to do them ally.

also whilst I am on
-the max diameter on the finished item is bob on 150mm
-the machinist says he is to charge me for the next size up, as he has to true the billet, is this correct?

 

[izzmus]

I am not a Porsche expert but I would highly doubt that they would use cast hubs and not FORGED hubs.

 

[kchan711]

I agree with Izzmus. Porshe uses a compressing die to forge its wheels. This increases the strength dramatically over cast wheels or machined wheels. Unfortunately, it also makes it extremely expensive for one-offs (although cheaper for mass production). You may want to consider certain heat treatments or choose a higher grade aluminum alloy to account for lost strength due to machining. You can look up many of the material properties for the different alloys for free on

http://www.matweb.com

.

-Kyle

Kyle Chandler

http://www.chiefengineering.net

"To the Pessimist, the glass is half-empty. To the Optimist, the glass is half-full. To the Engineer, the glass is twice as large as it needs to be!"

 

[GregLocock]

A big problem you will have is that the coefficient of expansion of the aluminium is much greater than that of steel, so your taper roller bearings will lose their preload when they get hot, or bind when cold.

That's why we use hub units not two seperate bearings in alloy spindles.

So far as material goes, it will need to be a high strength alloy with excellent properties. I expect you'll use 6061 T6, that may not be the best choice but I am not going to make a recommendation as it is a safety critical part and you are not designing it properly. Have you wondered why so few cars have had aluminium spindles in the past?

Pressing steel studs into aluminium is rather difficult. I'd do a lot of practice runs first to set the required fits etc. I doubt you will get aluminium wheel studs to live.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[MikeHalloran]

Yes, the machinist has to true the billet. That's the least of your problems.



Mike Halloran
Pembroke Pines, FL, USA

 

[thundair]

When you say alloy, are you saying aluminum?






I don't know anything but the people that do.

 

[GregLocock]

me? yes.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[patprimmer]

Maiko did a disk brake conversion for link pin model VW Beetle and "B" series Porsche front ends. These had a magnesium hub. Min ran over 100,000miles with no bearing problems on a hotrodded VW Beetle used (or abused) every day. It used the standard VW tapered roller wheel bearings.

Summer Brothers also made a disk brake conversion for off rod buggies using VW type front suspension. These had aluminium hubs of rather substantial dimensions. They served us well on an off road racing buggy.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Tmoose]

With the typical adjusted-on-the-car-by-a-big-nut tapered roller bearings it is possible to put considerable interference fit in an aluminum hub to keep the outer races snug, and the final room temp adjustment takes care of it all, but the running roller clearance with blazing hot brakes is undoubtably a bit loose. If the car was parked in Sherman Station, Maine in January, in the morning at -40F/C the 0.002 inch endplay

With roller or ball bearings installed as a preset cartridge, extra initial interference would create extra interference (negative clearance). BSA, Norton, and Triumph motorcycles with all or half aluminum connecting rod plain bearing big ends tread a narrow line avoiding going into negative clearance at low starting temperatures.

My Checkoslvakian 2-smoke dirt bike has steel inserts cast in the cases for the ball main and transmission bearings, just like the FAG bearing design book says it should.

 

[pantswagen]

hello again all, well I had them made, I now wish to have your opinions.

there they are

so i have stock roll sentres, ackerman
basically stock geometry

-my only real concern is fissure strength - if thats what the term is?

do i just have them made in steel?
-the machinist won't do them in steel - i don't know why?
-maybe you can explain.

If anyone in the world, would like me to post one to you, so you can copy it, in steel, i will be happy
-but then what grade steel?

 

[patprimmer]

Why would you not use them now that yoi have already made them.

If you do need them in steel, just find another machinist, They are not exactly a rare commodity.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[pantswagen]

MY CONCERNS ARE STRENGTH

DO I GET THEN MADE IN
8.8
10.9
12.9

-OR A STRONGER GRADE OF ALUMINIUM
-I WANT IT DONE CORRECTLY
-THEY WILL BE ON A 1.5 TON VAN
I.E. IDEALLY HOLDING UP A 100 RATED TYRE


-I JUST WANT THEM CORRECT - TO GRADE, INDUSTRY STANDARDS

-I KNOW I NEED AT LEASE 10.9 FOR CALIPER BOLT STRENGTH

-

 

[pantswagen]

http://en.wikipedia.org/wiki/Carbon_steel

medium grade
-machined
then case hardened?

 

[Toolish]

"That's why we use hub units not two seperate bearings in alloy spindles."

Can someone point me to more details about these units. I am looking at designing an aluminum hub but I am worried about the wheel bearings and expansion. Any help greatly appreciated.

Thanks

 

[patprimmer]

Toolish

Why don't you start your own thread instead of hijacking this one. That way you can also give it an appropriate heading

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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for site rules

 

[GregLocock]

As Pat says but

http://www.nskeurope.com/cps/rde/xchg/eu_en/hs.xsl/wheel-hub-units.html

should get you going

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.