Thought this would be the best place to ask, as people here seem to have answer for everything.
I may (depends on if the required components will fit in the given space) be making a winch that will need a reasonably substantial/hard wearing clutch, but I can't seem to find anything suitable via google. The clutch will be single sided, so I'm looking for some kind of material that can be rivetted or possibly bonded on, and suitable spec sheets, so I can figure out if I can fit the clutch where I want it, and have it transmit the required amount of power (guessing about 30-40hp, but low speed so fairly high torque is needed).
I assume you cant adapt an existing (car) clutch plate?
I have some surplus clutch plates if that would help, I suppose you could drill the rivets and steal the friction lining? can you use a metal on metal clutch? what about brake pads as clutch pads? more info might lead to an easy to obtain answer.
Diving in the deep end here and may be making it more complex than it needs to be, but 40-50hp sounds like a lot of torque at low speeds, though no mention of speed range. I would first look at the torque required at expected speed. Then use this in frictional coefficient sums for the material (clutch plate / brake lining ?) chosen, to get some idea of surface area required. All the math will be on the web somewhere, as will friction plate mnaterial characteristics. Ideally, run the clutch at the high speed end of the geartrain to minimise the torque, as this is really what defines the surface area required.
Looking at car or m/c clutch components might be a good start, similar bhp. Alternatively, use a dog and / or sprag clutch, which would have no problem handling that sort of power...
It's for a forrestry winch/dozer blade to be mounted on the front of a tractor driven from the PTO (rated at 540rpm, or possibly 1000rpm if extra speed would be needed).
Inital figures for a 3500kg pull (dead pull, not rolling), with a reel centre diameter of 100mm, gives a torque of 1746Nm at the reel. Now reeling speed is still to be figured out, but probably looking at something in the region of 100 rpm, so with a 5:1 ratio, I'm still looking at 350Nm if I can fit the clutch on the input shaft. Having the clutch on the input shaft is the key to this winch, as I want to minimize stack height of the winch drum/clutch.
The commerical winches have the clutch working directly on the reel, and is a disc of friction material rivetted to the driven sprocket, with the other side pressing directly on the underside of the winch reel.
My main issue is finding the frictional co-effcient figures so I can work out what size of clutch plate would be needed, aswell as a source of suitable material. Dismantling a commercially available clutch is one option, but I still need figures as the torque transmission is going to be pretty critical, as it also acts as a slip clutch for overload protection. The whole lot is going to be hydraulically controlled, so adjusting the pressure of the thrust ram will be done to fine tune the clutch slip point, but I still need to get in the ball park in the first place.
A modern car may be developing (say) 100 HP but it does it at something over 3000 rpm, so the torque is considerably less than your
540 rpm application. Maybe stacked plates alternating friction material and metal like a motorcycle clutch. Alternatively look at the brake assemblies for Newage axles as used on dumper trucks - they are an oil bath stacked plate arrangement operating at low rpm and high power.
There is a place supplying friction material in the Holmthorpe estate in Redhill. I just did a google search and found the place. Capel Mills Friction UK Ltd. It was listed on a page of places supplying friction material.
From a (not entirely expert) reading of specs, diesel engined cars tend to have higher torque than petrol engined ones. Just looking at the spec for my car (petrol) compared with its diesel equivalent shows torque of
350 and 650 respectively - they don't quote units but I assume it's Nm. The 650 is given at 1800-2500 rpm compared with 3200 rpm for the 350, so it's more than just an inverse relationship.
No they don't. For a given capacity normally aspirated diesel engines have significantly lower torque and bhp than normally aspirated petrol engines. However, most modern car diesel engines are turbocharged to overcome this limitation. What you then get is a diesel engine that still doesn't rev very high but has high torque and the same bhp per litre as a smaller normally aspirated petrol engine. Of course if you turbocharge the petrol engine you'll then get both higher torque and higher bhp per litre at the same boost level as the diesel engine.
Just looking at the spec
What is your car? Whatever the units 350 and 650 are fecking high torque figures for a car engine. Are you sure you don't drive a railway loco?
I've got a TwinDisc industrial clutch here off a Lister diesel, waiting to go in the scrap. No idea of its capabilities, but you can take it away if it's likely to be any use.
A diesel engine will always have a higher torque than an equivalent petrol, due to the far higher combustion pressures involved. It's just that the diesels max revs are far lower than the equivalent petrol. It's what you do with the torque that matters. By the time the engines geared to similar speeds, torque levels will be fairly similar for any given hp of engine.
My 1.7 diesel is rated at 285Nm, but that's not running that high a boost pressure. The ford 2.2tdci must be putting out a fair amount of torque...
They might manage it a few times, but your average vehicle clutch, doesn't need to be engaged under full torque/load very often. I know the speeds I'm considering burn out shouldn't be an issue, but sheering is. And sheering when you've got a 60ft tree balanced with the winch is not really an option!
I have considered using a clutch plate from a vehicle, but instead of driving it through the centre as it would be in a vehicle, have it so when engaged, it's clamped between the driven and non-driven plates, but I'm not entirely sure how the clutch plate would react. This is still a serious option.
You're going to use hydraulic pressure to engage the clutch? Not very good idea from a safety point of view. If pressure falls or the engine stops for any reason, the winch lets go.
BTW MH gives the a co-efficient as .4 for brake type material on cast iron. The formula: Power Transmitted by Disk Clutches. - The approximate amount of power that a disk clutch wi]] transmit may be determined from the following formula, in which:
H = horsepower transmitted by the clutch: p = coefficient of friction; f = mean radius of engaging surfaces; F = axial force in pounds (spring pressure) holding disks in contact; N = number of frictional surfaces; S = speed of shaft in revolutions per minute:
That's the whole idea. Should anything go wrong, it's far safer for the winch to stop, and the brake to come on (the winch will have a band brake operating directly on the winch reel, which needs hydraulic pressure to release). Even the mechanically operated winches need to be held in drive.
Thanks for that. I've got that in a college textbook somewhere, but it'll save me having to find it! Only issue is with the co-efficient spec,as I'll be using steel. I'm guessing that there won't be much difference from cast iron, as steel is used for some brakes, but I've yet to find a source that will confirm that.
It will be interesting to see how the clutch apply pressure will be balanced against the brake release pressure so that there is simultaneous release of one and the application of the other. Especially when a bit of wear & tear takes place. Perhaps the odd accumulator will be required. Inadvertent release of winch ropes before brakes take up can be a trifle disconcerting.
The clutch and brake will be operated of seperate spools using closed centre hyrdraulics, which will at a later date have electrical control added (for remote operation) I know the commercial units somehow manage it of one control, but I'm not entirely sure how they manage to compensate for different loads on the winch to get a smooth transition from braked to pulling or unreeling. I know it can be done using some extra mechanicals, which I will be allowing for adding at a later date if needed.
I eventually found that after much googling last night. Can do what I want with a 200mm diameter clutch, but applying the force required is going to need a bit of a rethink, as I suffered a bit of brain fade when thinking about the pressure needed to release a standard diaphragm clutch plate (totally forgot about the leverage ratio for the fingers, and the resultant actual force on the clutch!).
Just need to get some proper design drawings done, and make sure everything is going to fit in on paper, then I can start cutting some metal, rather than my usual approach of working it out as I go.
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