landroversforever Posted October 14, 2015 Author Share Posted October 14, 2015 Not quite what is being asked in this case but for general calculations. Remember you are dealing with line pull effectively a point load, with a standard low line winch there is also an element of rotational forces on the mount (why the line should come out the bottom of the winch!), mounting feet forward mostly negates that as I believe is being done in this case on the mount but it will still be there on the bumper mountings to the chassis. Also think about where the recovery eyes are, if you do a double line pull then 5 tonnes is applied on each line hence 10 tonnes total, if the recovery eye is part of the winch bumper, make sure the entire bumper doesn't come off!, what is it actually attached to and how?. Multiple pulleys and it can get confusing, had to give a talk to a senior engineer early this year to explain why when pulling a 250klbs load up it showed 240klbs on the weight indicator but when lowering it it showed 260klbs, all to do with the number of sheaves in use and where the load was actually measured from. It was a very big winch, think the system was rated at 1,200klbs!. Useful info for others to think about, but as you say not much use to me as this is all regarding my rear winch. Quote Link to comment Share on other sites More sharing options...
zim Posted October 14, 2015 Share Posted October 14, 2015 Multiple pulleys and it can get confusing, had to give a talk to a senior engineer early this year to explain why when pulling a 250klbs load up it showed 240klbs on the weight indicator but when lowering it it showed 260klbs, all to do with the number of sheaves in use and where the load was actually measured from. It was a very big winch, think the system was rated at 1,200klbs!. Aaah... the joys of a straight hole - I've looked up the reason for this before. From memory it was due to the friction experienced throughout the system (sheaves) and the fact that your load cell is on the dead end of the line. This goes away once your hole has some angle - back to the more conventional PU & SO weights due to drag. G Quote Link to comment Share on other sites More sharing options...
discomikey Posted October 14, 2015 Share Posted October 14, 2015 my book states that lifting and pulling equipment should generally have a FOS of 8-9, i realise that doesn't really help with your weight saving but then a block of ali in compression should be able to take a fair load! Quote Link to comment Share on other sites More sharing options...
landroversforever Posted October 14, 2015 Author Share Posted October 14, 2015 Cheers for the info Mike! I thought the FOS for lifting was 7 and more like 3 or 4 for pulling from memory. Impressive when you think our big gantry crane at work has a SWL of 150T on the main hook The block in compressing is going to take a hell of a lot of load to damage it, I was just trying to remove any flex from it. I did a couple of rough sketches in Powerpoint as I was trying to explain it to Dad as he's away in Brussels at the moment. Please excuse the basic 'qualities' of them They were thrown together between text messages as I don't have any models of the winch. Quote Link to comment Share on other sites More sharing options...
Cheesy Posted October 14, 2015 Share Posted October 14, 2015 My honest answer would be with a load cell, as you use to test cranes etc. However for a home user i think you'll battle to find a cell G They are quite common for racing yachts to keep an eye on forestay tension.... Being for a boat though they would probably cost more than both winches Quote Link to comment Share on other sites More sharing options...
zim Posted October 15, 2015 Share Posted October 15, 2015 my book states that lifting and pulling equipment should generally have a FOS of 8-9, i realise that doesn't really help with your weight saving but then a block of ali in compression should be able to take a fair load! From memory we (well whoever is out there to inspect) load test pad eyes to double when they get welded on, But i think that reduces to something like 1.5 once over a certain weight. They'll be MPI'd before and after. G Quote Link to comment Share on other sites More sharing options...
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