I think you are all wrong

You are talking about doubling forces to lift things ??? etc.

In reality you still have the same force ie 'F=ma', m being mass of the drive and a being the deceleration force acting in a foward direction on the seat belt. Therfore if you draw a correct free body diagram with all acting forces you will find that the force on the B-pillar is half.

Look closley at your diagrams 1 and 2 you are doubling the mass content to prove a point????

But that weight (you, probably dead by now) was there in the first place.


AAAAArrrggghhh this is all too hard for me.

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Cheap, Fast, Reliable. Choose two.

No - that body mass was at rest even though the car was doing xx kmh. Its only when there is a sudden deceleration that that mass becomes a weight and loads the pulley. Its why people get busted ribs and bruises in a crash from seat belts but they dont get those same fractures and bruises from simply wearing seat belts in a non crash situation.

Should we be driving minis?

If you fail to brake and crash into a solid wall in your mini you will decelerate quickly.

If we assume a uniform deceleration rate (wildly inaccurate assumption) and assume that the front of the car crumples by about 1/2 a metre, then we add belt stretch giving you an additional 1/2 a metre, then you've come to a dead stop in 1 metre.

Here is a table of the average deceleration rate you will experince in that 1 m. Other distances thrown in for interest.

If the deceleration rate is over about 10 g and you apply all that body weight through the belt (or your face on the wheel) you will be well rooted. So, if the value is red, you're dead!

Speed (km/h) distance (m) decel (g)

40 2 3
40 1 6
40 0.5 13

60 2 7
60 1 14
60 0.5 28

80 2 13
80 1 25
80 0.5 50

100 2 20
100 1 39
100 0.5 79

If you go in side-on, you'll have about 0.2 metres to stop so the fatal speed is much lower.

Motto, don't crash but if you have to, crash into something that will allow you a longer deceleration distance and lower deceleration rate. Meaning the parked car is better to hit than the tree/wall. Avoid side on crashes.



So, who's up for a fang this weekend??

When its all said and done, there are some people on here who have walked away from some pretty horrendous crashes that should have killed them, other have been injured but lived. Then we all know of people who have died in relatively minor incidents.

Certainly minimising risks in incredibly important, be it driving styles or component choices. However, at the end of the day we dont have the final choice of what happens in an accident.

Some other being does.

And prefereably the cheapest one you can find in the limited time available..............

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1967 Cooper S - new front bearings to do.
1965 Cooper S shell - Slow progress. No time or money!
1966 Deluxe- next rustoration!
Mk 2 & XJ6 Jags. Less said the better.