simonr Posted September 16, 2010 Share Posted September 16, 2010 Does anyone know roughly the stall torque of any of the common winch motors? For a series wound motor, knowing the Horsepower of it is actually not that useful so manufacturers usually quote stall torque and max unloaded RPM. I have back calculated using published figures for TDs winches - 9500 Lbs on the first wrap and 173:1 reduction. That yields a figure of 8.74Nm - which feels a bit low to me! For the 12,000Lb version of a TDs, the same calculation gives 7.51Nm despite having the same motor. It could be that the 12,000 winch actually pulls 14,000lb or that a 9500lb winch only really pulls 8200Lb - or it could be that the figures are just made up! I have to assume that this is not the stall torque, but a torque at which the line is still moving at a certain speed. I have an Iskra PM DC motor which quotes a stall torque of 30Nm. You would expect a similarly sized series wound motor to be higher! I want to use a winch motor as a power source for something - but need to know the peak torque to work out how strong the shafts need to be and what reduction ratio is required. Si Quote Link to comment Share on other sites More sharing options...
Retroanaconda Posted September 16, 2010 Share Posted September 16, 2010 Failing someone just knowing, could you make up a rig with an arm of known length on the end of the motor, and then a force reading taken off the end of that arm somehow upon the motor stalling, this should give you the stall torque? Ie. if the arm was 5 feet long and you got a force of 50lbs off the end of it then it would be producing 250lbs-ft of torque. Quote Link to comment Share on other sites More sharing options...
simonr Posted September 16, 2010 Author Share Posted September 16, 2010 True - but it was to save me building a test-rig. It may come to that though. I do actually have a 100,000N (10 ton) load cell - so I guess I could measure the actual pull a winch is generating. Si Quote Link to comment Share on other sites More sharing options...
bishbosh Posted September 16, 2010 Share Posted September 16, 2010 Si - surely the drive shaft of the TDS would tell you how strong your shafts need to be? They don't break when the winch stalls. A conservative assumption of material properties combined with the cross section of the shaft should give you a reasonable estimate? Quote Link to comment Share on other sites More sharing options...
simonr Posted September 16, 2010 Author Share Posted September 16, 2010 Si - surely the drive shaft of the TDS would tell you how strong your shafts need to be? They don't break when the winch stalls. A conservative assumption of material properties combined with the cross section of the shaft should give you a reasonable estimate? I wondered about that - but there is no easy way to tell what material or heat treatment it has had. Also, is it over or under engineered and by how much? Even the difference between 8Nm and 30Nm makes a big difference in drive component spec! Si Quote Link to comment Share on other sites More sharing options...
bishbosh Posted September 16, 2010 Share Posted September 16, 2010 My guess that it would be chineese monkey metal with no special treatment. Yield stress of say 200N/mm2, maybe 250? Being a volume product, I can't see it being over engineered by much, but I am only guessing. The other thing to bear in mind is it is a hexagonal shaft so probably selected from readily available stock? IIRC it doesn't have any modifcatins at all, it is just a plain bar. Quote Link to comment Share on other sites More sharing options...
simonr Posted September 16, 2010 Author Share Posted September 16, 2010 Mine is a round bar with the hex milled / broached on the ends! Si Quote Link to comment Share on other sites More sharing options...
Night Train Posted September 16, 2010 Share Posted September 16, 2010 If you have one on a winch could you load it up it and measure the voltage and current at ever decreasing rpm until it stalls and then plot that to find out, somehow? Quote Link to comment Share on other sites More sharing options...
simonr Posted September 16, 2010 Author Share Posted September 16, 2010 I could just tie the back of the LR to a tree and connect my load cell between the winch and another tree to see what the actual pull is. I was just hoping to avoid having to do it as it should be a simple question. I'm starting to wonder if it's not quoted because armed with the reduction ratio, you can calculate what the actual winch pull should be. I'm wondering how closely that relates to the published pull oif the winch? Si Quote Link to comment Share on other sites More sharing options...
Bush65 Posted September 16, 2010 Share Posted September 16, 2010 I could just tie the back of the LR to a tree and connect my load cell between the winch and another tree to see what the actual pull is. I was just hoping to avoid having to do it as it should be a simple question. I'm starting to wonder if it's not quoted because armed with the reduction ratio, you can calculate what the actual winch pull should be. I'm wondering how closely that relates to the published pull oif the winch? Si The problem with that is to know the mechanical efficiency of the winch - friction and other losses in the bearings, gears, brake, drum are significant. Quote Link to comment Share on other sites More sharing options...
Daan Posted September 16, 2010 Share Posted September 16, 2010 THe problem youre having is that with 173:1 ratio, the drag in the system can be quite high, combined with the rather carp design of some drum bearings I have seen, you could easily loose 50 % of torque in the system, so just finding out the pull of the winch doesn't tell you much. Did you ask david bowyer this question, caus I bet he knows things like this. Daan Quote Link to comment Share on other sites More sharing options...
simonr Posted September 17, 2010 Author Share Posted September 17, 2010 I've actually asked each of the winch motor manufacturers (that I know of). David has been the most helpful - but I still have no answers! That's why I'm thinking there is a conspiracy of silence! It seems nobody knows or is willing to tell. I plan to measure the motors I have this weekend if I have time and I'll publish the results! Si Quote Link to comment Share on other sites More sharing options...
Night Train Posted September 17, 2010 Share Posted September 17, 2010 That seems like a good idea. It would give a real indication of the 'strength' of the motor and also the overall efficiency of the winch. Quote Link to comment Share on other sites More sharing options...
nicks90 Posted September 20, 2010 Share Posted September 20, 2010 Si, i did a backward calc of the torque from the official figures on the warn 9500lbs winch with the 6hp xp motor. Torque figure came out at 3.48Nm! so either the motor is appalling, or the gearing and bearings used in the construction are horrendously inefficient. Quote Link to comment Share on other sites More sharing options...
Lara Posted September 20, 2010 Share Posted September 20, 2010 May be interesting or not But a couple of years ago I did some load cell tests of a few winches and motors etc and found a massive difference in efficiency between winches that were supposedly the same and even fitted with the exact same motor (actual motor from the other winch) and treble checked for repeatability and comparability! I mean over 25% in some cases (forgive the pun) I think you would need to test the motor directly to get any real figures! I would make up a disc brake with the calliper connected to a load cell and calculate from there! Hope comments are of some help. Lara Quote Link to comment Share on other sites More sharing options...
simonr Posted September 20, 2010 Author Share Posted September 20, 2010 Thanks Chaps! I didn't have time to do any testing over the weekend - but I'll try later in the week. Undoubtedly there is a big difference in the drag in different types of winch but I'm increasingly thinking that the headline winch pull figure is just made up! Si Quote Link to comment Share on other sites More sharing options...
BogMonster Posted September 21, 2010 Share Posted September 21, 2010 It could be that the 12,000 winch actually pulls 14,000lb or that a 9500lb winch only really pulls 8200Lb - or it could be that the figures are just made up! Electric winch figures, total fabrication? Perish the thought! Quote Link to comment Share on other sites More sharing options...
Bush65 Posted September 21, 2010 Share Posted September 21, 2010 Because most vehicle winches don't have self aligning bearings, just the state of alignment when the winch is mounted up to the bar and when the assembly deflects under load will have a significant affect on the line pull vs motor torque. I have seen results of some poor winch installations. Quote Link to comment Share on other sites More sharing options...
simonr Posted September 21, 2010 Author Share Posted September 21, 2010 Because most vehicle winches don't have self aligning bearings, Which could actually be a good modification! Si Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted September 21, 2010 Share Posted September 21, 2010 Electric winch figures, total fabrication? Perish the thought! Surely this thread is a very dangerous :ph34r: Quote Link to comment Share on other sites More sharing options...
fozsug Posted September 21, 2010 Share Posted September 21, 2010 Which could actually be a good modification! Si "X-Winch Bearings" ? Quote Link to comment Share on other sites More sharing options...
elbekko Posted September 21, 2010 Share Posted September 21, 2010 Or just "X-Winch" perhaps? Quote Link to comment Share on other sites More sharing options...
simonr Posted September 21, 2010 Author Share Posted September 21, 2010 Surely this thread is a very dangerous can of worms Why? I had a quick look at bearings big enough to go in a TDs winch - and for 2.5" ID, 4"OD (Smallest I could find), they were a mere £275. Don't think I'll be rushing out to replace mine! I might have a look at IGUS Polymer bearings though. I've had very good results with one of their materials that self lubricates and is happy submersed in muddy water. Si Quote Link to comment Share on other sites More sharing options...
landroversforever Posted September 21, 2010 Share Posted September 21, 2010 Or just "X-Winch" perhaps? So Si, when is this being released? the winch to beat all winches? hydro or sparky at the flick of a switch. large drum, fast or slow, Quote Link to comment Share on other sites More sharing options...
simonr Posted September 21, 2010 Author Share Posted September 21, 2010 So Si, when is this being released? the winch to beat all winches? hydro or sparky at the flick of a switch. large drum, fast or slow, Almost - but not quite! I'm building electric grass-skis! Using Harley Davidson toothed drive belts inside out as caterpillar tracks. Load cells in each ski which are used to vary the motor speed differentially for steering. They could either be very cool - or very painful. I can see doing the splits at 30mph being less than desirable! I've tried using a little Mag-Motor that we used for Robot Wars as well as a couple of Iskra PMDC motors - but none of them have the right sort of torque / speed characteristics. Winch motors are a little bigger than I intended - but worth a shot as I have several. If that fails, the next step is to use a number of RC car motors in each ski. Just looking at the possibilities at the moment. Si Quote Link to comment Share on other sites More sharing options...
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