Mounting winches amidships?

On Thu, 6 Apr 2006 07:27:48 +0100, Ian Rawlings wrote
(in article <[email protected]>):


>
> I'm not sure how much winch power gets sapped by using rollers and
> pulleys to guide it in any of these various installations though. If
> you route a cable through an angle then a lot of force is going to get
> put on the pulley, and that force has to come from somewhere. Damn my
> comprehensive school level physics ;-)
>
>

Energy = force x distance. The rollers don't move in the direction of the
force so they don't use any power. They do use some in the friction of the
bearings, but again energy = force x distance, except this time distance is
the number of rotations of the roller and force is the friction in the
bearings. So long as the bearings are sound, they won't require a lot of
force to turn so they won't use any significant amount of power.

The biggest wastage of energy will probably be the flexing of the cable
itself, which will be greater the tighter the bend the cable goes around, but
that would manifest itself as heating of the cable, and at the power your
winch will have available, the heating would be noticeable if it was a
significant proportion of the total power of the winch.

Nick.

On 2006-04-06, Nick Williams <[email protected]> wrote:

> Energy = force x distance. The rollers don't move in the direction of the
> force so they don't use any power.

If you've got a 90 degree bend in the cable as it goes around a
pulley, then the pulley mount is going to have to be strong to resist
the pressure on it. That pressure has to come from somewhere, so it
surely has to come either from the load, or the winch, or both. So
the load will be a bit harder to shift and/or the winch will exert
less pull, I don't see how it could be any other way. If the pulley
has no effect on the system, where does the pressure on it come from?

--
Blast off and strike the evil Bydo empire!

Roberts wrote:
> Hi Group
> Another military vehicle, the ancient petrol engined Scammell 6x6 had
> the winch amidships and could be routed to front or rear with pulleys
> at the rear and vertical rollers at the front. It was no fun
> switching it around especially in temperatures exceeding 100F.
> Alan

Sounds like the old Scammell Pioneer - used by REME, I believe, for tank
recovery purposes. I 'borrowed' one once to extract my S11A which was stuck
in a bog, down to the headlights & still going down. The Scammell winch rope
did not even pull taught before the Series came out, albeit with trivial
chassis damage caused by this irresistable force dealing with a seeming
immovable object. I learnt a fair bit about driving in swamps that day/night
....

Karen

--
"I'd far rather be happy than right any day."
- Slartibartfast

Ian Rawlings <[email protected]> wrote:

> If you've got a 90 degree bend in the cable as it goes around a
> pulley, then the pulley mount is going to have to be strong to resist
> the pressure on it.

Looking at the forces applied to a pulley doing a 90 bend
I reason that there are two forces. The load pulls one way
and the winch pulls another. Doing the old parallelogram of
forces thing I get 1.4 time the load applied to the pulley
spindle. Of course if it was a 180 turn back on itself it
would be twice the load.

We are looking at more than drill a hole and pop a bolt in.

nigelH
Physics geek


*** Free account sponsored by SecureIX.com ***
*** Encrypt your Internet usage with a free VPN account from http://www.SecureIX.com ***

On Thu, 6 Apr 2006 09:54:10 +0100, Ian Rawlings wrote
(in article <[email protected]>):

> On 2006-04-06, Nick Williams <[email protected]> wrote:
>
>> Energy = force x distance. The rollers don't move in the direction of the
>> force so they don't use any power.
>
> If you've got a 90 degree bend in the cable as it goes around a
> pulley, then the pulley mount is going to have to be strong to resist
> the pressure on it. That pressure has to come from somewhere, so it
> surely has to come either from the load, or the winch, or both. So
> the load will be a bit harder to shift and/or the winch will exert
> less pull, I don't see how it could be any other way. If the pulley
> has no effect on the system, where does the pressure on it come from?
>
>

Sorry, Ian, but you're illustrating a fundamental lack of understanding of
the laws of mechanics. No energy is used in the application of any force
unless that the object to which the force is applied force moves. It might
be counter-intuitive, but it's a basic rule of physics!

The force exerted on the roller is passed to its mount, and unless the mount
moves, no energy (and hence no power) is used in the application of that
force. However, the rolling motion of the rope over the roller does introduce
friction, both in the bearings of the roller and (especially) in the flexing
of the cable. The more tension in the rope and the tighter the bend around
the roller, the greater the bearing and flexing friction will be, so to that
extent you are correct that some power is lost in the roller chain, but none
of the losses are as a result of the force exerted on the chassis of the
vehicle by the roller (unless the mountings of the roller, or the chassis,
bend).

It's probably helpful to think of this in terms of the tension in the winch
cable. If you have a straight pull directly off the winch drum, the tension
in the cable is obviously the same at the load end as it is at the winch
drum. If you put the cable round a pulley, the tension is still the same
unless you loose some of it in making the roller turn. In practice this is
what happens - the forces required to turn the pulley and bend the cable
round the pulley absorb some of the cable tension so the tension in the cable
length between the winch drum and the pulley is slightly higher than the
tension in the length between the pulley and the load while the load is
moving (they are the same if the load is static).

The 'wastage' in the pulley/roller will be a function of how well the cable
rolls over it and how tight the turn is in relation to the diameter of the
cable. Tight turns distort the cable more so they create more friction.

The moral of the story is to make the roller/pulley as big as possible, and
mount it as rigidly as possible. This way you will minimise the losses in the
cable transport system.

Nick.

On 2006-04-06, Nigel Hewitt <[email protected]> wrote:

> Looking at the forces applied to a pulley doing a 90 bend
> I reason that there are two forces. The load pulls one way
> and the winch pulls another. Doing the old parallelogram of
> forces thing I get 1.4 time the load applied to the pulley
> spindle. Of course if it was a 180 turn back on itself it
> would be twice the load.

Hello Nigel, what I was originally wondering was not how much of the
load the pulley would have to handle, but how much harder the winch
would have to work in order to pull via a 90-degree bend pulley than
it would if it were pulling with a straight cable. Can you apply your
physics geekery to that? Would be useful info.

--
Blast off and strike the evil Bydo empire!

People Hi,

I believe some of you may know the IBEX vehicles. For a few years now you
can order your IBEX with a very interesting centraly mounted winch which can
operate both from the front and the rear of the vehicle.

As for the discussion related to the loss of power or forces generated on
the pulley and in relation to the angle the wire rope has to sustain in
order to have its pulling direction altered by 180 degrees I believe that we
could also discuss about the synthetic winch ropes which tend to be a far
better choice for such applications due to their extremely good flexibility.

Take care
Pantelis

"Nick Williams" <[email protected]> wrote in message
news:[email protected]...
> On Wed, 5 Apr 2006 20:38:57 +0100, Roger wrote
> (in article <[email protected]>):
>
> >
>
> >
> > I've always wondered at the logic of the mid mount on the 101s - was
> > it done to shorten the overall length of the vehicle, because having to
> > change the cable direction whilst upto your family jewels in cold water
> > does not appeal at all. Maybe it was just a method of getting the
squaddies
> > to drive carefully - "Oops I'm stuck", "You stupid tosser, now get out
in
> > that freezing water and re spool the winch cable and pull yourself out
> > backwards"
>
> I suspect it may have something to do with the vehicle's military
heritage.
> The 4 ton 4x4 Bedford truck which was the next size up military utility
> vehicle from the 101 has a mid mounted winch with a vertical axis on the
> drum. It also had a very large drum diameter - always put me in mind of
the
> winch on a ploughing (steam) engine.
>
> Nick.
>

On or around Thu, 6 Apr 2006 11:55:58 +0100, Ian Rawlings
<[email protected]> enlightened us thusly:

>On 2006-04-06, Nigel Hewitt <[email protected]> wrote:
>
>> Looking at the forces applied to a pulley doing a 90 bend
>> I reason that there are two forces. The load pulls one way
>> and the winch pulls another. Doing the old parallelogram of
>> forces thing I get 1.4 time the load applied to the pulley
>> spindle. Of course if it was a 180 turn back on itself it
>> would be twice the load.
>
>Hello Nigel, what I was originally wondering was not how much of the
>load the pulley would have to handle, but how much harder the winch
>would have to work in order to pull via a 90-degree bend pulley than
>it would if it were pulling with a straight cable. Can you apply your
>physics geekery to that? Would be useful info.

not much. The rate at which the load moves is the same and the losses
created by bending the pull are, as someone else said, frictional. There's
a sideways force on the pulley, due to the angle in the cable, which will
try to straighten. This force doesn't use energy unless the pulley starts
to move... If the bearings are good and the rope fits the pulley nicely
then it still pulls the same, near enough.

consider the case of using a pulley in the roof to lift a load from the
floor by pulling downwards. The downward pull needed is the weight of the
load plus any frictional losses to balance the load and anything more than
this weight will lift the load.

Sure, there's a force holding the pulley to the ceiling, but you get that
"free", it's supplied by the structure. You don't have to pull twice as
hard as you would if simply lifting the load direct, you just pull in the
opposite direction.

This is not to be confused with using pulleys to multiply the force at the
expense of distance moved. If , when pulling a vehicle, you attach a pulley
to the load, run the cable around that and hook it back to the winch
vehicle, then you get double the pulling power but half the distance. The
difference is that the pulley moves with the load. If you have 2 pulleys,
and another on the winch vehicle, you can get 4x the load by going around
twice. This is how your traditional rope crane manages to lift 10 tons on a
cable that's only good for 1T on a straight haul - the use about 10 runs of
cable, by going around 5 pairs of pulleys, and the byproduct of that is that
the winch hauling it only needs 1T capacity as well, although it needs a big
drum and miles of cable.



the thing altering forces applied is vectors: it applies, for example, if
your load is a vehicle in deep ruts and you're pulling off-line. The load
is constrained to move in the direction of the ruts, so your most efficient
pull is in that direction. If you pull off-line, you waste a part of the
force applied by the cable proportional to the angle between the optimum
direction and the cable direction. If that angle gets to 90 degrees, then
the forward component of the applied force is zero.

In addition to this you may add drag to the load, by pulling it sideways
against the walls of the ruts, thus further reducing the force available to
move it forwards.

Same point applies to a vertical misalignment of cable on load, although if
the thing's stuck in deep mud, then adding a vertical-up component to the
force may in fact help free it.

--
Austin Shackles. www.ddol-las.net my opinions are just that
Appearances: You don't really need make-up. Celebrate your authentic
face by frightening people in the street.
from the Little Book of Complete B***ocks by Alistair Beaton.

On Thu, 6 Apr 2006 07:27:48 +0100, Ian Rawlings <[email protected]>
wrote:

>If it could be made re-routable as well then that
>could sort out the niggles regarding half the length in one direction
>and the convoluted path in the other if the need was great enough.

As I said it is an elegant solution to providing some tug fore or aft
and I think it would get you out of most difficulties. It also has the
advantage of keeping the winch relatively safe.

If you really do need to re route it then there are a number of
options which come from timber winching. One is the idea of tag lines,
you have a soft eye in the winch wire to which you attach a short
length of wire rope with your hook on. One tagline with hook does the
rear recovery and the other does the front, the front tag line is long
enough so that while the hook is wound in as far as the front bumper
the joint is at the end of the route to the rear. The idea is that the
tagline never gets wound in far enough to spool on the reel.

This system requires that all the fairleads are rollers so that the
joint can run past them. Proprietary joints with C hooks are available
but are too bulky, I prefer two opposed soft eyes and a wire quoit
made up between the two, this quoit is expendable and can be cut with
an axe in an emergency. NB this is for pulling only, not for any
suspended loads without a full secondary back up.

On 2006-04-06, Nick Williams <[email protected]> wrote:

> Sorry, Ian, but you're illustrating a fundamental lack of understanding of
> the laws of mechanics.

Indeed, it's a bad habit of mine. I wouldn't have bought a Lotus and
a Landy if I knew about the laws of mechanics, e.g. the chances of
both vehicles being off the road being proportional to the amount of
rain.

> No energy is used in the application of any force unless that the
> object to which the force is applied force moves. It might be
> counter-intuitive, but it's a basic rule of physics!

OK, that makes sense, Austin agrees too so that backs up an already
sensible explanation.

<useful and detailed explanation snipped>

Thanks muchly.

--
Blast off and strike the evil Bydo empire!

On 2006-04-06, Austin Shackles <[email protected]> wrote:

> not much. The rate at which the load moves is the same and the losses
> created by bending the pull are, as someone else said, frictional. There's
> a sideways force on the pulley, due to the angle in the cable, which will
> try to straighten. This force doesn't use energy unless the pulley starts
> to move... If the bearings are good and the rope fits the pulley nicely
> then it still pulls the same, near enough.

<rest of explanation snipped>

Thanks Austin, nice explanation, I hope your fingers don't smart too
much after all that typing.

I've just shelled out the money for the pinzgauer so hopefully once
the bank account has calmed down a little after such trauma I'll be
able to look at putting the ideas into practice. Both the pinz and
the Landy would lend themselves well to having a central winch if I
can swing it.

--
Blast off and strike the evil Bydo empire!

The sensible way to go is an electric motor on each wheel at least that is
the way my mums four wheel drive four wheel steer offroad electric
wheelchair worked.

For something powered by a couple of traction batteries it had a lot of
oomph.

--
þT

L'autisme c'est moi

"Space folds, and folded space bends, and bent folded space contracts and
expands unevenly in every way unconcievable except to someone who does not
believe in the laws of mathematics"


"Derek" <[email protected]> wrote in message
news:[email protected]...
>
> "Ian Rawlings" <[email protected]> wrote in message
> news:[email protected]...
> > On 2006-04-05, Derek <[email protected]> wrote:
> >
>
> It's probably the way to go once the technology is sorted I expect they
> will be more efficient than conventional 4wd with less energy loss (
> friction diff loads etc).Couple that with regenerative braking which has
> been around for a long time the only missing piece in the jigsaw is a
> battery or rather power storage medium that doesn't have the weight
penalty
> of the stuff available now it can't be long coming? ( the bridge carriers
I
> saw are just the babies of the range makes you wonder what they make for a
> really big job)
> Derek
>
>

On Thu, 6 Apr 2006 15:17:08 +0100, Ian Rawlings <[email protected]>
wrote:

>I've just shelled out the money for the pinzgauer

Did you get a 6 wheeler?

I remember seeing one of these off on an expedition to the Antarctic,
or the other one, it cost GBP12k, about 24 times my annual wage but I
was determined to have one. In the end I settled on a 1965 Haflinger
which promptly failed its MOT on a suspension bush. I just could not
get the bronze bush out of the aluminium housing and just wasn't nouse
enough to solve the problem as I would now. I asked a mate to fix it
and it took about a year of asking till I was fed up, went round to
check and he had sold it! It was then I learned about the difference
between theft and illegal conversion :-(.

AJH

On 2006-04-06, AJH <[email protected]> wrote:

> Did you get a 6 wheeler?

In theory. I don't want to tempt fate but I've transferred the money
and had the seller sign a "purchase order" that I bunged up, and he
will have the money tomorrow. Asking price was £10k inc vat but he
was in a pickle so I put in an offer of £7K inc vat and was told to
feck off, but he called me a week later and accepted it. He's got the
loot now and if all goes to plan I arrange collection tomorrow. If
the transport company is up to snuff and the seller doesn't go home at
lunchtime then it should arrive tomorrow.

The reason for the large reduction is because he works for a company
who bought it to armour it and then blow it up, but Pinzgauer UK found
out about it and sent him a new model and a spare chassis for free, so
now the one he bought has just sat there taking up space for four
months, not moving, they have no use for it any more. It's not even
road registered for the UK yet. To get it registered requires some
simple mods on the back lights, an MOT and then paperwork with the
DVLA.

I had a look at it but given that I couldn't test drive it properly (I
was able to take it round the yard a few times), and it was outside of
the dealer network so I couldn't compare it to other ones that were in
stock, I couldn't justify buying it at the original price when I could
buy it at that price from dealers already registered and MOTed. Given
the doubts I had about it, he got a low offer from me. I didn't think
he'd get better and it seems I was right. If I decide not to keep it
I should be able to get what I paid for it at least.

> I remember seeing one of these off on an expedition to the Antarctic,
> or the other one, it cost GBP12k, about 24 times my annual wage but I
> was determined to have one.

A new six-wheeler will cost over £70K ex vat, a good 1973 model costs
£10K inc vat, and that's what he paid for it, I know the chap who sold
it to him so know what kind of history it's had.

> In the end I settled on a 1965 Haflinger which promptly failed its
> MOT on a suspension bush.

Haflingers are great, I saw one once that had massive tyres, they
weren't ludicrously large but as the vehicle was so light, it was able
to float in water! ISTR that he rowed it with a paddle ;-)

> I just could not get the bronze bush out of the aluminium housing
> and just wasn't nouse enough to solve the problem as I would now.

It's unexpected problems that I didn't have the time or opportunity to
check for that prompted me to put in such a low offer, hopefully if he
doesn't scupper the deal at the last minute then any problems I have
won't eat up the £3K saving, but I know these things can be a money
pit so it's a calculated risk.

> I asked a mate to fix it and it took about a year of asking till I
> was fed up, went round to check and he had sold it! It was then I
> learned about the difference between theft and illegal conversion
> :-(.

****ter! I hope you took one of his kneecaps home with you..

Anyhow, the deal seems set in stone now so I should have the thing by
early next week, then will keep it for a few months and then decide
which to sell, the landy or the pinz!

--
Blast off and strike the evil Bydo empire!

On 2006-04-06, AJH <[email protected]> wrote:

> Did you get a 6 wheeler?

Yes I did :-D

It's sat out on the drive, making the 110 look very very small indeed,
despite them being about the same size. I need to convert the rear
lights to have separate brake lights, indicators and sidelights, then
get a class 7 MOT IIRC, then have some fun!

the grin will be rather forced tomorrow when I'm doing the finances,
but it's a lot of vehicle for the money..

--
Blast off and strike the evil Bydo empire!

On or around Fri, 7 Apr 2006 19:20:15 +0100, Ian Rawlings
<[email protected]> enlightened us thusly:

>On 2006-04-06, AJH <[email protected]> wrote:
>
>> Did you get a 6 wheeler?
>
>Yes I did :-D
>
>It's sat out on the drive, making the 110 look very very small indeed,
>despite them being about the same size. I need to convert the rear
>lights to have separate brake lights, indicators and sidelights, then
>get a class 7 MOT IIRC, then have some fun!
>
>the grin will be rather forced tomorrow when I'm doing the finances,
>but it's a lot of vehicle for the money..


..JPEG!
--
Austin Shackles. www.ddol-las.net my opinions are just that
"For when the One Great Scorer comes to write against your name,
He marks - not that you won or lost - but how you played the game"
Grantland Rice (1880-1954). my opinions are just that

On 2006-04-08, Austin Shackles <[email protected]> wrote:

> .JPEG!

Heh, I'm rewiring the lights at the moment (after de-butchering the
rear wiring, when they replaced the body many years ago they took out
all the multinational wires and just left the swiss), then I'll park
it next to the Landy and take a few pics.

In the meantime, just imagine a big green box with six wheels and
that's about it!

--
Blast off and strike the evil Bydo empire!