Lieutenant Scott wrote:
On Tue, 01 May 2012 18:41:22 +0100, John Williamson
wrote:

Lieutenant Scott wrote:
On Mon, 30 Apr 2012 23:45:59 +0100, Davey wrote:

On Mon, 30 Apr 2012 21:44:06 +0100
"Lieutenant Scott" wrote:

On Mon, 30 Apr 2012 21:27:02 +0100, newshound
wrote:

On 30/04/2012 19:58, Lieutenant Scott wrote:
On Mon, 30 Apr 2012 15:44:47 +0100, Lieutenant Scott
wrote:

I was going to burn down some tree stumps aided by some petrol to
get it going. Having a bottle of white spirit to hand I thought
I'd use that instead of going to the garage to get petrol. It
won't light!!!!

This is the exact product, and it says flammable on the side. But
it bloody well isn't.


http://www.bartoline.co.uk/products_...vent%20Ra nge





Sorted.

I bought a jerry can of petrol and tried burning them, but they
kept going out. So I took the easy option.

To my neighbour's horror, I reversed the car into the back garden,
tied the tree stumps to the towbar, and yanked them out of the
ground. She was particularly concerned that my car (or flying tree
stump) was aiming directly for her kitchen window. She took the
dog for a walk while I did it :-)

Glad it's sorted. Can't have been much of a tree stump in that case,
though (unless it was very rotten below ground). When it's the
other way round, a small tree can stop a surprisingly fast or heavy
vehicle.

It's a 1.9 turbo diesel, and I took a good run at it. Snapped a tow
rope and a chain before getting all 10 out. Automatic gearbox helps
too.


Remind me not to buy a car from you.

You seem to be under the mistaken idea that a car can't pull something
that hard. Think how tough a towbar and attachments has to be to pull a
caravan safely.

Not all that strong, as you're pulling a rolling load at either moderate
acceleration or at a steady speed. Back of envelope says a maximum of
half a ton total, summing the horizontal and vertical components.

What about when you put your foot to the floor while towing? You've
still got the full power of the engine pulling on the towbar. I suppose
I was adding momentum of the car too though, but then again there will
be some safety margins I can make use of.

Work out the torque at the driving wheels, which will let you work out
the acceleration, then compare that with the force required to
decelerate the mass of the car at about ten times that accleration. For
most cars, maximum acceleration is well under 1G, while the deceleration
when you're snatching a stump is at least 5G. The safety margins are on
the order of 100%, not 500%.

A steady pull of that magnitude is fine. Pulling out a tree stump is a
shock load which is well in excess of what the towbar and its fixings
are designed to take. I'll try it with a Land Rover with a good chassis,
but I'll use a kinetic energy recovery rope to do it. The clue here is
that you managed to snap a towrope and a chain, which says that the peak
loads were way above the design limits of the car and towbar.

No, it says they were above the design limits of the chain, which is a
lot thinner than the towbar and fixings.

Then you must be driving a tank. The towbars on most cars are fastened
to metal which is less than 1mm thick. Even my Land Rover has a chassis
which is less than 3mm thick at the point of attachment, and that's
reinforced for kinetic energy recovery, which is a posh name for doing
to bogged down vehicles what you were doing to trees.

Luckily, I live somewhere your car will never be sold.

Are you sure? I sold a Honda CRV to a guy in London.

Still safe. I left London a decade ago. London's also big enough that
you can always find a fool who'll buy anything you want to sell. ;-)

--
Tciao for Now!

John.