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Found out why my gearbox broke

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Apparently this was all caused by a bolt on an engine mounting snapping.

I just can't believe this with a modern car :thumbdwn:

You cant really blame Skoda for a bolt breaking, millions of bolts are made each day, they cant check every one.

Is it producing a lot of torque? ;)

  • Author
You cant really blame Skoda for a bolt breaking, millions of bolts are made each day, they cant check every one.

True. They cant check every water pump either.

Or perhaps they could use better engineered parts? IMHO

There isnt much you can do to make a "better engineered" bolt and keep the cost of the car at a reasonable level. F1 companies X-Ray bolts in critical areas to check them - no car manufacturer is goin gto do that.

Just bad luck.

  • Author

Again I agree.

I have just never experienced such poor levels of reliability over a 1 year period as I have with this car. This is the newest car I have ever owned too.

Was it a stretch bolt?, you can tell by the torque setting, so many NM followed by an angle. If it had been previously removed it should have been replaced and not re-used.

Stretch bolts cannot be indentified by angle tightening. Lots of modern cars now use angle tightening for critical bolts as it is more accurate.

  • Author

I do not know much about bolts, but I do think that a critical piece of engine mounting should be secured better. If one snapped bolt can wreck a gearbox, then there is something wrong with the design of the mounting.

I am not an engineer, but I do understand that areas of high stress should be able to take much greater loads than they are deigned to under normal conditions. Bolts cost pence each, a group of 4 would fair better than one large one.

I have not examined the area of damage as it is in the shop, hopefully they will show me what they have found.

Bad luck does come in to it, bad design also played a part here.

I do not know much about bolts' date=' but I do think that a critical piece of engine mounting should be secured better. If one snapped bolt can wreck a gearbox, then there is something wrong with the design of the mounting.

I am not an engineer, but I do understand that areas of high stress should be able to take much greater loads than they are deigned to under normal conditions. Bolts cost pence each, a group of 4 would fair better than one large one.

I have not examined the area of damage as it is in the shop, hopefully they will show me what they have found.

Bad luck does come in to it, bad design also played a part here.[/quote']

To be honest, and i hope Mr Gooch agree's with me here, i think you are being very unfair to the engineer, I could almost bet my left testicle that this bolt will have a built in factor of safety of at least 2, which means the bolt can accept double the force it will usually see during operation and will not fail within these limits.

However as is everything else in life things go wrong, a miniscule flaw within the rolled bar at a critical point most probably caused this failure, these bolts are probably made in their thousands if not tens of thousands and for instance one in every 500 will be picked of the line and NDT'd before being tested to failure to ensure the bolts fall within the quality guidelines of the company/British standard/ANSI standard. To conceive that one of these bolts will never fail is crazy.

I see your point about fitting more bolts, apart from cost/weight the question has to be asked WHY? if 1 in 50,000 cars has this fault then it is not really a problemif 1 in 10 cars had this problem then the designers would be back infront of the drawing board. If you adopted this philosophy you would end up with a grossly overdesigned car resembling a tank.

This is the reason they built the forth rail bridge in the way they did after the tay bridge disaster, you could remove 50% of the members and it would still be grossly overdesigned, why? public confidence, but came in at a silly price.

belah1.jpg

Tay bridge before collapse

RailbridgeMain.jpg

Beautiful but over designed

heres a wee interesting site about bolting technology and has an example of an engine mount failure http://www.boltscience.com/pages/failure1.htm

Whats the mileage and what bolt broke?

  • Author

50K

Not sure exactly which bolt yet, will have to speak to the garage

As to being unfair to the engineer- well didums! I have spent 1.5K keeping a 3.5 year old car on the road in one year, just on mechanical failures.

The worst I ever had on my Hondas (which were twice as old) was a faulty rear caliper. The only time they were ever in the dealer was for servicing or MOT.

Honda can engineer a car, it seems to me IMHO that Skoda cannot, or take the risk that it will last at least 3 years before breaking.

I am pleased that the rest of you have been more fortunate, perhaps I have bought a badly treated car?

Nice bridge BTW, proper engineering ;)

As to being unfair to the engineer- well didums! I have spent 1.5K keeping a 3.5 year old car on the road in one year' date=' just on mechanical failures.

[/quote']

I am being totally simplistic here and looking at it from a 3rd party perspective, Had it been my car then I would be jumping up and down having a moan about the price too so forgive me for that ;)

Being an engineer kind of puts you in their shoes for things like this, but the same principle applies all over. We have a price on a life of

  • 4 weeks later...

Thing about putting in four smaller bolts instead of one big one is - it takes four times as much work to fit them. That costs.

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