Sizing snatch blocks for linkage/ tractor winches

[Logan]

Wills, I came up against same thing with our lgland 55A a few years ago, and it was like brush utter said. We needed all 100 odd metres of 11mm cable fitted to go out and back. Couldn't find a 6t block with 12t shackle with 11-12mm Shreve, they were miles bigger. Used a quality 4t American block with its whatever rated shackle, can't remember. Did feel bit nervous standing by winch pulling ropes.

 

You don't want to assume only using the weight of the log or whatever, and shackles and blocks need to be rated above the max possible pull, coz if that log hooks up on a stump at 2m/s you will quickly jerk to max and if using lower rated shackle it will come apart and be shot at you like shrapnel.

 

It's crap that there are no large diameter pulley, smaller Shreve diameter blocks available.

 

Cheers, John

[mendiplogs]

hello jon, went and had a look on igland site and could only see a odd mix of funky looking blocks, thought they'd have bit more info too?

 

Cheers, John.

 

HI LOGAN its on he igland site mate thanks jon

[openspaceman]

 

Heaviest usage for a forestry winch would be using a snatch block attached to the load and the end of the winch line brought back to anchor point near to tractor- so doubling the line pull I believe at the snatch block.

 

 

I think you are right, also as you say LOLER does not normally apply, though a PC has recently required full LOLER on a 3 tonne winch hauling on an embankment because the load would drop if a rope or chain snapped. Outcome was a new 10mm rope and loads restricted to its 1.25 tonne SWL.

 

In the bad old days prior to PUWER or LOLER we all used Highland Bear pulley blocks as snatch blocks. On the skyline these would keep going untill the wire rope wore through the sheave. They were pressed steel with sealed roller bearings. I attach a picture of a highlead block (currently deep inside my shed where it's languished for 30 years) but the pulley was the same and attached by a 3 tonne bow shackle to a strop.

 

 

The justification was that the SWL was half the proof load which was half the breaking strain. I never broke any bits for these non lifting purposes other than the occasional wire through wear and tear. Here it is, the red one beneath the grey, one being abused with the 4tonne Igland DD.

 

 

I would expect these pulleys still to be obtainable.

 

Farmi 3 point link winches have a re direct pulley and this is of a similar roller bearing type, side plates for a shackle could easily be made. I may still have a sheave and bearings from my 8 tonne.

 

I wonder if these gloves are still available, quite handy for pulling wire rope out but generally pull the chain not the rope.

 

[Wood wasp]

I remember those blocks! We used to skyline big timber off the hill, full length trees too so a fair bit of weight and drag. Ropes would break but the blocks never failed other than wearing through time which you could see on the pulley and side plates.

[steve collins]

dont forget you will lose pull due to friction from the pulley sheaves and also the angle that the cable is being re directed at. although you may think your doubling your pull from say a 4 ton to 8 ton your not and your only probably getting just over 6 ton pull. I was told 2 1/2 times what your winch can pull empty on a course hope this helps

[mendiplogs]

I think you are right, also as you say LOLER does not normally apply, though a PC has recently required full LOLER on a 3 tonne winch hauling on an embankment because the load would drop if a rope or chain snapped. Outcome was a new 10mm rope and loads restricted to its 1.25 tonne SWL.

 

In the bad old days prior to PUWER or LOLER we all used Highland Bear pulley blocks as snatch blocks. On the skyline these would keep going untill the wire rope wore through the sheave. They were pressed steel with sealed roller bearings. I attach a picture of a highlead block (currently deep inside my shed where it's languished for 30 years) but the pulley was the same and attached by a 3 tonne bow shackle to a strop.

 

[ATTACH]170553[/ATTACH]

 

The justification was that the SWL was half the proof load which was half the breaking strain. I never broke any bits for these non lifting purposes other than the occasional wire through wear and tear. Here it is, the red one beneath the grey, one being abused with the 4tonne Igland DD.

 

[ATTACH]170556[/ATTACH]

 

I would expect these pulleys still to be obtainable.

 

Farmi 3 point link winches have a re direct pulley and this is of a similar roller bearing type, side plates for a shackle could easily be made. I may still have a sheave and bearings from my 8 tonne.

 

I wonder if these gloves are still available, quite handy for pulling wire rope out but generally pull the chain not the rope.

 

[ATTACH]170557[/ATTACH]

HI MATE great old pics there mate thanks jon

[wills-mill]

I've just spotted that Uncle Gruber has got some lovely blocks, decent loads and sized for smaller winch cables

 

'Umlenkrolle' is the magic word- Suchergebnisse für: 'umlenkrolle' - Grube KG

 

http://www.grube.de/nordforest-pulley-sr-fs16-160-kn-16-t-payload-44-306.html

[Logan]

Good find wills, there's a SRL F12 on the English page that has the correct spec for me, max 12mm cable, 6t input line, 12t on shackle. Pretty good diameter 135mm I think, will try order one up.

Edited December 19, 2014 by Logan
Sore eyes

[mendiplogs]

Good find wills, there's a SRL F12 on the English page that has the correct spec for me, max 12mm cable, 6t input line, 12t on shackle. Pretty good diameter 135mm I think, will try order one up.

 

Hi all so did anyone get a large snatch block thanks all Jon

[LGP Eddie]

Spotted these in the latest Land Rover Owner mag, and did a bit of research.

 

It seem seems they may be available up for up to 13mm rope on the manufacturers site, but these are only for 10mm, so perhaps worth a call to see if they can get larger sizes? They are super light being all alloy construction too.

They have a very high rating at 17,500kg which should tick all the boxes for many.

 

 

Snatch Block Lighweight Aluminium

 

 

 

Eddie.