Please Check My Logic and Arithmetic...

[ianh1968]

According to my 1978 Zeus Precision Data Charts,
a 5/16" UNF bolt has a nominal major diameter of
0.3125" and an effective diameter of 0.2854".

Q: So what is the effective cross sectional area of the bolt?
A: It's Pi-R-Squared...

Q: Please Explain...
A: OK.

Pi is 3.1415926 Approximately
R is the radius, which is half of the diameter.

So we have:

Area = ((0.2854/2) x (0.2854/2)) x 3.1415926
Area = 0.06397 square inches.

Q: So why do you want to know this?
A: Well, someone was taking the piss out of me for saying:
"You could quite easily hang the WHOLE CAR off ONE 5/16" bolt..."

Q: OK, I see your point, you are not in the habit of making unsubstantiated
bullshit statements on this forum, so you want to justify your remarks?

A: Yes -Before I made that remark, I made a few enquiries and
offered the following document as backup evidence...

http://www.americanboltcorp.com/tech/techgr.pdf

Q: So, your point is, exactly?
A: Well, the data in that document says that the weakest 5/16" UNF bolt
they list has a tensile strength minimum poundage of 4,300 pounds.

When I last put my car on the weighbridge, it came to 800Kg, with
me sitting in it.

As there are 2.2046 pounds to the Kilogram, my whole car with me
in it, including "too many pies", would be 1,764 pounds.

Q: So what?
A: Well, if I am not mistaken, 1,764 is less than half the 4,300
pound stated capacity of ONE 5/16" UNF bolt.

Q: OK, you've got me there, but what about the Zeus book data?
(And your stupid calculations...)
A: Well, the bolt document gives the PSI rating for the 5/16" UNF
bolts as 74,000 PSI.

74,000 x 0.06397 square inches = 4,733 pounds capacity for
cross-sectional area the bolt. This compares quite closely with
the 4,300 pound stated in the data.

Q: So you were wrong, then.
A: Yes - Sorry
"You could quite easily hang TWO WHOLE CARS off ONE 5/16" bolt..."

Ian

[ivor badger 2]

Well look at it this way. If you wanted to lift the car with a light chain, would 1/4" links suffice and the answer is yes.

Remember also that bolt quality matters. Conversation with scrutineer over the size of cap screws holding coil spring damper units to the trailing arms. Are these strong enough? Well they are 1/2" unf cap screws that are X quality and they will handle a 12,000lb tension load and an 8,000lb radial load and the whole car weighs about 1000 lbs. So that's around a safety factor of 8 for a radial load on one back wheel. Reply =OK!

[wantafaster1]

Well, as a rough rule of thumb I was told as an apprentice, an inch of weld would carry a ton, and a quarter bolt would carry a ton.
So I just use the rocker cover studs for an engine change. I'm sure Colin Chapman had all this figured out better than us though!

[Lakeland997]

Q: So why do you want to know this?
A: Well, someone was taking the piss out of me for saying:
"You could quite easily hang the WHOLE CAR off ONE 5/16" bolt..."

I hope you don't mean me Ian . My 'Flat Earth' comment was meant to emphasise my ignorance not yours.

Andy

[ianh1968]

Q: So why do you want to know this?
A: Well, someone was taking the piss out of me for saying:
"You could quite easily hang the WHOLE CAR off ONE 5/16" bolt..."

I hope you don't mean me Ian .
My 'Flat Earth' comment was meant to emphasise my ignorance not yours.
Andy

Andy, this is something that I have never really understood.
I've seen ARP bolts with outrageous PSI numbers being quoted.
You gave me the opportunity to check out some numbers and
I detailed my findings in a way that I hope will be useful to others.

I have also checked out my cable hoist in the garage and the
anchor point at the top is a single M8 bolt. This approximate
size is much stronger than many think.

I have said many times that we can all learn things from others
on the forum.

My post was intended as being humourous so maybe we could
both learn something... (And I didn't want to hijack your thread).

There is nothing wrong with a bit of piss-taking - providing its
given and taken in good spirit! (Which it was...)

Best wishes,

Ian

[Spider]

There is nothing wrong with a bit of piss-taking - providing its
given and taken in good spirit! (Which it was...)

Best wishes,

Ian

Unless you're a 'wanker'.





Enjoyed the opening post by the way

[Chalkie]

Ian that is amazing bit over the top but hey gotta love that weldone

[ianh1968]