Hub flange failure - diagnosis, engineering chums?

^i don't wish to start a fight, but I can't see how a component like this could be forged ,machined and heat treated and sell for 20ish regardless of how big the batch was.
I don't understand why you rubbish my explanation, then continue to ask, why it happened? If you have enough knowledge on what its made from why continue to ask?

damage from a chisel, started it, fretting finished it.

I hate being an aaaaarrrsssehole

 

Do VW sell them for 20?

Fatigue finished it off. The two little black lines, at 95 deg, on the second photo, of post #1, are typical of fatigue fractures.

Because there are two small points on the periphery, where the black lines start, is why I suspected fretting, as the cause of fatigue. Determining why fatigue starts, is not the easiest of subjects! The Comet Airliner crashes prove that.

Why anyone should put a chisel in there, I can't imagine. I can photograph some Audi 90 Q 20V hubs that I removed years ago, which have no marks at all on them. And, they have a much larger bearing to remove, and are thus more difficult to deal with!

 

Tinydubs, it's astonishing how efficient industrial manufacturing can be - - for instance my company manufactures a replacement aftermarket engine part, cost breakdown $6 for materials and labour (a 125gm investment casting of expensive stainless steel) which is then CNC machined for $5 (two operations totaling 50 - 60 seconds per casting) - - add packaging, amortisation of tooling, R&D, marketing etc etc and we wholesale it for $20 - - engine reconditioners then pay $25 - 30 - - local garage gives them $37 - 45 - - vehicle owner pays $47 - 55 (figures depend on "supply chain" efficiency/greed/exclusivity/numbers

An inferior (truly!) oem part retails for between $175 and $225 depending on the country - -

 

But, the opposite is also true.

Back in about 1970, I was given the task of comparing Quinton Hazell aftermarket clutches, with those manufactured by ourselves. ie Laycocks.

To put it simply: The QH clutches were made from 5h!t materials, and were not to tolerance!

DO NOT BUY QH RUBBISH! Unless it's Fag, or similar, in a QH box!

 

10ish from GSF unless the price went up.

Gurds

 

Who makes them? QH?

 

I still don’t buy into fretting as been the primary cause of the failure. If it was would we not see more examples of this type of failure on the forum? But if experience say fretting so be it

I thought the only way to definitely stop fretting is to change the fit or shaft section to give more interference pressure between the bearing and shaft. There are other fixes such as copper plating but this is usually only results in managing the situation. Best plan is to put a new one on which is closer design intent for the bearing fit and is at the start of its design life.

 

I was uber sure in my first post, #6, that the failure was caused by fretting, as I assumed that the hub and bearing were both in good condition when assembled. And, also assumed that the bearing hed not been fitted fully up to the face on the hub. The gap left would then have permitted moisture ingress, corrosion, fretting, or relative movement fretting.

I am now more open minded, having read your own and other posts, regarding the possible damage to the hub prior to the re-build. Post #82. So I do not discount accelerated fatigue due to a notch raiser.

I discounted normal life cycle as, on the Golfs of this period, the CV splines fit right to the end of the hub. Thus support the hub beyond the break line. On Audis, such as my own, the splines of the CV only fit 50% down the hub! If normal life cycle was easily exceeded, you would expect to see lots of Audis with hub failure.

As it happens, I was stripping the rear CVs from my Audi 90 Q, to use on the Golf, only yesterday. I had already changed the hubs to 5 stud some years ago, so I had previously dis-assembled, and, re-built the unit myself. I decided to take the hubs out and re-fit them just to see. They came apart easily, with no damage, and went back together again, using ASP. But, I was not 100% sure that I had got the hub face tight to the bearing face, just by hammering, while supporting the inner race! When I originally did the job, I used a hydraulic press.

With regard to the prevention of fretting. I believe that this is a subject still much under disscussion. I am not sure it has been resloved yet. I have not worked in Engineering for 12 years now, but I recall lots of investigations and disscussions back then, about the subject. Molykote's reasoning in post #68 gives me some hope that I am doing my best to limit its effect.

 

Just to confirm the VW flange I bought does have their stamps on it & some numbers (unsure if they correlate with the part no - don't think they do) Photos if needed by anyone.

100 from VW believe it or not. Clearly not cheap, but with 2 in my stocks, broken or cracked, it's an issue I felt the need to play safe on!

Non engineering morons like me, for starters!

The inner race was stuck high up that one I photographed and arrowed, so I put it in the vice and reached for the chisel! As I don't have a puller, I seems an obvious thing to do, yet in the light of this thread, quite a worrying thing to even contemplate!

Interesting debate being had on this. When I got the new hub pressed (using a proper press this time) the chappie that did it gave it a last push to make sure it was fully home.

 

i`ve done some more digging and found this, http://www.febi.com/en/unternehmen/industrietechnik/technik/bearbeitungsvielfalt/bearbeitungsvielfalt.html

at the bottom of the page it states, " Machining of cast housings on CNC machining centres."

i couldn`t let this go as my new job involves machining

as for vw selling them at 100, they aren`t main stealers for nothing

 

I am still quite convinced that VW will use forgings for wheel hubs. I do realise that cast hubs are available, for some vehicles, but I feel that for a front wheel drive hub, of such small proportions, a Cast Iron hub would be too notch sensative. Having said that, I would not be averse to being proved wrong.

I worked at a company that had both a foundry, to cast flywheels, etc. and a forge, where we made overdrive annuli, gearbox out-put flanges, diff. in-put flanges, gear blanks, gear shafts, etc.. Had a cast part been as strong as and cheaper than a forged component, then I am sure they would have cast them, as they were always looking to save pennies.

For your information, below is an article explaining how frorged hubs are machined for Nissan.

Renishaws tool setting solution aids competitiveness at leading UK automotive supplier
One of the most efficient suppliers to Nissan, UK, is Geo. W. King Ltd, where a high degree of manufacturing automation, including Renishaw probe systems, has been put in place.
In 1996, triggered by Nissans make-or-buy policy, and a strategic decision to out source the hubs for their 4-wheel drive models, Geo. W. King secured the contract for their manufacture. The installation of a bespoke Flange Cell in 1997, was initially conceived by an internal project management team, as part of the successful pitch. The cell consists of turning, heat treatment, drilling, broaching, grinding, sub-assembly, final inspection, and wash-and-pack operations. Each operation is an automated cell within a cell, all served by an Ewab conveyor system, as Production Manager, Andy Emmerson explained.
A fully automated line; assessor operators with a thorough understanding of the operation, service the machine tools and oversee the lights out operation, where raw product becomes a finished component. The line has a conveyor system, the main highway, which runs around the cell. Raw material in the shape of air-cooled steel forgings, placed on bespoke fixtures, are loaded manually on to the conveyor, and carried to satellites, from which a variety of robotic load/unload systems present a component for machining. The satellites are filled on a one for one basis as a machined component exits. Until called into the satellite, waiting products remain on the main highway.
Manufacturing the hubs for each of the models, the first and most important of the machining operations comprises four, twin-spindle CNC lathes, each fitted with Renishaws HPRA tool setting arms. The lathes are dedicated in pairs to each model, and electronic sensors around the highway ensure that the relevant part is conveyed to the assigned machining operation. However, depending on demand, flexibility exists to utilise any number of the lathes for a particular model.
A load/unload robot, integral to each of the lathes, picks up a forging and feeds it into the chuck for the first of two turning operations, continued Emmerson. The part is rotated, and after repeating the turning operation, the machined component is delivered into an electronic gauging operation at the rear of each lathe.

 

Mmmmm, given the frequency of front wheel bearing changes, I stick in a cheap new Febi item from GSF each time for the 10+ its worth. Never went to VAG for it.

Maybe VAG part is forged and GSF part cheapie casting?

Gurds

 

Tip for removing a big bearing with a small puller.

This is the front hub from my 90 Q. It has been sitting around like this for years, since I converted to 5 stud!

Put the puller on.

Tighten until you are afraid of breaking it. I used a short spanner.

Heat bearing race.

It will pop up, and the puller will land on your toe!

I had to repeat this twice to get the race to pop on to the top of the hub!

 

^ now that should be a sticky.

 

Is this thread still on the go?

It must be time for Chris to need another wheel bearing by now!

 

I have already, 2 days ago! Keep up with your telepathy Dan!

The irony? In a hurry, no time to order from VW on a 2 day wait, I went to GSF. Out came a green aftermarket box with some German co name IIRC, initials "OMG".

'Hub flange sheared off sir? We have just what you're looking for: "OMG" '

Who's idea was that

As an alternative to daved's professional puller, I was advised to do what I'd done by chance the other day, when beating it with a chisel wasn't enough: Dremel a groove into the inner race, taking care not to cut too deep. Then hit it with chisel, and it should split. Brittle metal, and once split, it'll come off without a fight.

 

That's not a professional puller! It was from a cheap, sort of, pound-saver shop, in Castlbar. Can't remember the name, Brian.G will know. Cost about 5. That's why I dare not tighten it very hard. Hence the tip about the heat input.

New Dremel grinding tips are not much cheaper, and won't last as long. By time time you've ground two bearing inners off it will have cost more in grinding bits!

 

Im a total heathen then. I cut a groove in the race with an angle grinder then split the race with a cold chisel

 

The same as just about every garage in the world does too, NWR.
They do not seem to have wheels falling off all the time either.

Chris is just doing it wrong.