I do worry whether my fork is rated and certified though for a snatch n shovelmao , well that’s one way to get a sugar rush
Hicap phill
Well-Known Member
Ok so this has taken me a while to work, in my (fag packet head) and since you have edited, no worries.
I would love to see your fag packet workings on this. As I see it you went over the SWL (I didn’t say the tested load) of pretty much everything you used, except your 8t snatch blocks.
What is the rating on those “low load pulleys”?
I am asking as it needs to be asked for peeps that come along and just find something on the net.
J
There is a whole raft of stuff on the mechanical advantages of using blocks but in simple terms it's like this ...
Lets say the load is 6 tonne.
The landrover has a winch
Winch to load = 1 line
To move the load the winch produces 6000 kgs which is transfered to the load and the winch.
In this scenario the landrover would get dragged towards the load.
Next we take the winch rope to the load and come back, through a pulley, towards the landrover and attach the rope to the landrovers recovery point.
Winch to load = 2 lines. The same 6000 kgs of pull is applied.
We still don't move the load as we are still sharing the load between us but now we move together at half the speed. The load is still on only 1 rope as the line from the winch to the first pulley is simply changing the direction of pull.
Instead of attaching the 2nd line back to the recovey point on the same landrover with the winch, we attach a pulley to an anchor (another landrover for example) and pass the rope through that and go back to the load.
Now the load has 3 lines attached to it. 1 (from the winch) and two supporting the load to two anchors.
We produce 3000 kgs of 'pull' from the winch and the 6000 kg load moves.
If we added another pulley to the load and took that line back to another anchor (a tree this time) we would only need 2 ton on the winch to move the 6 ton load.
Add another pulley at the tree and go back to the load and now you need only 1.5 ton on the winch.
Another pulley - 1.2 ton
Another - 1 ton
Haltrac Hoists typically have 8 pullys wheels (or sheaves) and the load is therefore moved with a 8:1 ratio.
1 ton lifts 8 ton
125kgs lifts 1000 kgs, you can easily lift a landrover engine out of the car using a Haltrac Hoist but just pulling on the 'tail'.
Haltrac (and other engine) hoists are typically made up of 2 multi sheave pully frames which have 3 connection points.
#1 is you pulling on the chain/rope/tail
#2 is the frame
#3 is the engine (or load).
The total weight of the load is supported by the frame (or anchor point) and your 'pull' is amplified 8 times so lifting the engine out is easy.
Having more than 1 anchor point splits the load (equally) between them.
So: (Fag Packet = simple division) Load Wieght/number of pulleys = pull on landrover required to move the load.
6000/3 = 2000
6000/6 = 1 ton
Do I need to "beef up" my D90 recovery points = No
The various recovery points/bumper/chassis legs/dumbirons etc will take around 9000kgs before they deform. My winch and line is rated @ 5000kgs (with margin).
My D90 weighs approx 2500kgs, in gear with the brakes on and a brick/chock at each wheel it needs around 3000kgs to move it (might be a but less but hey ho, safety) so I know when I winch 'in' and the landy tries to climb over the bricks i've reacherd about 3 ton.
2 pulleys I move 6 ton
4 pulleys I move 12 ton
If I tie the back of the landy to something I can pull circa 20 ton - all within a safety margin.
They are not rated.
They are not designed for 'lifting'.
I have some 50mm sheaves on a 2T WWL shackle and a 90mm sheave on a 3.25T shackle.
The shackles are 5:1 rated.
The sheaves likely to be no more than 5 tonne - i've not broken one yet . If it does collapse i'm not overly concerned as the pin of the shackle will 'save' the day.
Hippo
Lord Hippo
That's a lot of fuking about and all dependent on a gut feeling of bricks chocking wheels.
Why didn't you ask the hi-ab delivery driver to lift the old container to its new position with the truck he delivered the new container on?
Not a gut feeling, playing with a weigh bridge
Couldn't put the high-cube down cos there was a wall in the way. An iron fairy would have reached
How does a weigh bridge measure the weight of a pull, friction coefficient etc? Not alot adding up here. Talks a good game though.Not a gut feeling, playing with a weigh bridge
Couldn't put the high-cube down cos there was a wall in the way. An iron fairy would have reached
300bhp/ton
Well-Known Member
A kinetic rope would have worked better
Sometimes you have to work with what you have gotA kinetic rope would have worked better
chap in the middle of nowhere is stuck down a hole, you do what you can to get him out!
300bhp/ton
Well-Known Member
Very true. I suppose the solution would be to carry a KERR when off roading.Sometimes you have to work with what you have got
They are banned by so many clubs. It's a bit like banning folks at work from using a ladder. In the absence of such, they stand on a chair or desk. Such is lifeVery true. I suppose the solution would be to carry a KERR when off roading.
300bhp/ton
Well-Known Member
Personally I think the dangers of KERRs are very misunderstood. Anything you do with a KERR that is dangerous, would be equally as dangerous with a strap or non-KERR rope.
Also sometimes you can't just take up the slack and apply a steady pull. It depends on the terrain and how much traction there is, plus how stuck the vehicle is. It is perfectly possible that the recovery vehicle will just spin its wheels. Which means you won't be recovering a vehicle in that manner.
BTW - I think you posted about tow balls previously. These are heavily used in off road competition in the UK. For competitions regulated and sanctioned by the authorising body the MotorSport UK (aka MSA).
As in my pictures and description, I had little traction and he had none. I backed up and gave it some and out he popped as he gained traction. In many peoples eyes, this was 'dangerous' and they would be correct.
In my eyes, it was a calculated (I say gut feeling but it seems to upset some who don't understand that gut feelings come from 40 years experience) risk and it payed off.
No I didn't mention tow balls but others have in this thread. I don't like the idea but I have used the lower pin to pop a sling in on a lower force tow.
300bhp/ton
Well-Known Member
Where was the kinetic ROPE in that vid??
But a very good example of doing all the wrong things for all of the wrong reasons.
see thats it.. a risk assessment isn't about removing all the risks, its about calculating whats acceptable and how to work with the risks
300bhp/ton
Well-Known Member
Do you have a reading problem?
