Engine stand mounting bolts failed

[RrogerD]

As you say it's all part of the learning experience.

We don't all know everything, and kudos to your lad giving it a go.

It's an expensive mistake but such is life, I don't think there is anyone on here or in life that has never made a mistake (despite the poop they post), and I imagine there is quite a few that have made expensive mistakes to, even in their day jobs.

Best he not get too down hearted,

Thank you.

 

[JohnD]

stainless steel

ordinary stainless steel is unfortunately quite a weak metal, and easily fractures. You can't be expected to know that.

it is mostly imported from China, where it is built down to a price. It often contains 0% nickel to cut costs, which will even rust-mark when it is used for spoons and forks. I use it a lot in the garden and for non-safety jobs like plastic trim on the car, as I am in a coastal region.

I have snapped one myself, and the heads wear quickly.

It is possible to buy better-quality stuff, at a higher price, especially popular on boats, ships, for mechanical repair of broken bones, and a different alloy for some chefs knives.

Unfortunately I can't see your pic.

 

[RrogerD]

Well, what started as a disaster, resigned to the fact that it was his own fault in using the wrong bolts, has turned out to not be too bad after all. The engine dropping to the floor had broken off part of the cylinder head (a cast fitting at the end of the cam shafts) but he's managed to source a replacement for £30 second-hand. Now all fitted and appears to be the only issue.

At least he's learned from that one.

Thanks all.

 

[sxturbo]

Well, what started as a disaster, resigned to the fact that it was his own fault in using the wrong bolts, has turned out to not be too bad after all. The engine dropping to the floor had broken off part of the cylinder head (a cast fitting at the end of the cam shafts) but he's managed to source a replacement for £30 second-hand. Now all fitted and appears to be the only issue.

At least he's learned from that one.

Thanks all.

That's a result, thanks for the update always good to hear a happy ending

 

[Slow-Slow-Slow.]

My son has purchased an engine stand from Halfords rated at 340kg. He is swapping over the engine in his BMW from the 4-cyclinder to the 6-cyclinder.

The stand to engine fixings are 4 bolts that screw into the end of the block and the whole thing simply 'hangs' from these. He purchased 4 bolts from Halfords. He asked about suitability and the chap behind the counter says "yeah, should be fine".

So, screwed-in the bolts, let off the hoist and starts work. The bolts then fail (shear) and the engine drops to the floor a foot or so, cracking the head and other damage. Oil everywhere.

My questions:
- is this to be expected, bolts aren't designed for this or, should I suspect a flaw in the bolts?
- presumably I can claim costs of damages back from Halfords?
- anyone else experienced an issue like this?

Thanks

Edit:
It would seem that the bolts were M12 coach bolts and the doom-shaped head/s failed (I believe)

IF your Son clearly stated what his intended use of the bolts was for and the assistant gave the answer that those bolts would be suitable, then halfords is liable for any costs due to their failure, unless your Son has caused the damage by abuse of the bolt...which seems unlikely given the weakest part of a bolt is normaly the threaded section.

 

[Stivino]

There should have been four bolts securing the engine to the stand. At least one bolt appears to have sheared and, one bolt was bent.
What I would like to know is, what about the other two bolts?

 

[mointainwalker]

IF your Son clearly stated what his intended use of the bolts was for and the assistant gave the answer that those bolts would be suitable, then halfords is liable for any costs due to their failure, unless your Son has caused the damage by abuse of the bolt...which seems unlikely given the weakest part of a bolt is normally the threaded section. .

Let's be real here. He won't even know which "Keef" he spoke to -and they won't own up.

 

[Lower]

IF your Son clearly stated what his intended use of the bolts was for and the assistant gave the answer that those bolts would be suitable, then halfords is liable for any costs due to their failure, unless your Son has caused the damage by abuse of the bolt...which seems unlikely given the weakest part of a bolt is normaly the threaded section.

No, they’re not.

Halfords will exclude consequential liability in there terms and conditions of purchase, as do all retailers.

 

[Avocet]

Let's be real here. He won't even know which "Keef" he spoke to -and they won't own up.

No, if he still has the receipt (or e-receipt) it will probably say something like "you were served by XXX". Even if it doesn't, they have to log on to the till, so the system will know who it was. Of course, it won't know what they said verbally.

 

[Avocet]

I have (what I imagine is) a similar stand from Machine Mart (which I've actually never used in anger). The problem is that they can give a maximum engine weight, but not a distance out from the stand where the centre of gravity of the engine is allowed to be. I think normally, the user would be expected to use 4 of the bellhousing bolts to hold the engine to the stand? (And on a straight 6 engine, I think even that would be pushing it, because the engine is so long and isn't designed to be supported like that).

Coachbolts come in a variety of grades, the softest being incredibly soft. Metric grade 4.6. This means a breaking stress of 400N / square millimetre. The BMW bellhousing bolts are likely to be at least grade 8.8 (which will have a breaking stress at least DOUBLE that of a Grade 4.6 coach bolt). Of course, they do make grade 8.8 coach bolts, but I think they're quite unusual. They're normally only designed for holding wooden things together. It would be interesting to see if there's anything stamped on the bolt heads (or the packaging).

All that said, I'd still be a bit worried about hanging a straight 6 off its bellhousing mounting holes, regardless of what the bolts were made of!

 

[cdbe]

Surely if the bolts and the stand were bought in the same transaction and the purchaser states in writing that the seller advised that the bolts were suitable for the stated use then you have reasonable grounds for complaint. Personally I would email "head office" and explain that this could have resulted in serious injury but luckily it didn't and the matter was resolved for the sum of £30 plus some inconvenience, and you would like a gesture of goodwill to recognise this (I think a £50 gift voucher would be reasonable) - I often find this approach is easy for them and usually gets a result.

Otherwise, return the bolts and maybe even the entire stand (when finished with it) on the grounds that the package is not fit for purpose.

 

[JohnD]

slightly off-topic, I received some stainless bolts today and they are stamped "A2 70"

which I looked up and it is a grade with a defined strength and composition.
It says "minimum tensile strength of 700N/mm² (MPa)" but I don't know if that is considered good or bad.

In my case I am just using them for fence posts, but I don't remember seing the grade stamped on other screws or bolts I have bought, apart from HTS marked ones.
I have certainly snapped a cheap one with nothing but hand strength and a regular spanner.

These ones look less bright and silvery than usual.

 

[Avocet]

slightly off-topic, I received some stainless bolts today and they are stamped "A2 70"

which I looked up and it is a grade with a defined strength and composition.
It says "minimum tensile strength of 700N/mm² (MPa)" but I don't know if that is considered good or bad.

In my case I am just using them for fence posts, but I don't remember seing the grade stamped on other screws or bolts I have bought, apart from HTS marked ones.
I have certainly snapped a cheap one with nothing but hand strength and a regular spanner.

These ones look less bright and silvery than usual.

700N/mm2 is a bit weaker than a standard grade 8.8 "high tensile" carbon steel bolt (which has a minimum tensile strength of 800N/mm2). It would be stamped "8.8" on the head, meaning that it fails at 800 and yields at 80% of that. Stainless steels don't behave in quite the same way as carbon steels so they tend not to have a yield strength on them.

 

[Harry Bloomfield]

It is one of the stronger SS's, almost as strong as the plain steel 8.8.