i'm not sure how. it wasn't an extrapolation.
it was an exclamation on my opinion of how you run yoyur torque limiter... then followed by how most companies say to setup their torque limiters with respect to driving and driven equipment. I was not estimating beyond the known facts.. which an extrapolation would be.
you like your torque limiters to essentially.. not function.
if your mower can stall your tractor.. the torque limiter seems superflous in your setup.
your machine.. you may use or abuse it as you wish.. I statedt eh above so that others who may want to save their multi thousand dollar tractor at the expense of a 100=200$ torque limiter.
I'd much rather repalce a failed limiter than a pto clutch or a tranny or crankshaft.
your call on what you'd like to replace.
Those are extrapolations beyond the pale.
... To develop:
I believe you talk of a special case where, on old Fords, parts of the system where upsized externally without internal augmentation. The recipe for failure. Parts of a system must be designed to perform in concert. A tractor PTO clutch is ordinarily designed with this in mind.
...The fact that this clutch is there and is sized for the tractor makes it able to protect the tractor by slipping on a catastrophic overload. That this clutch is exercised regularly and is housed is a stable internal environment favor its stability of action. This in no way means you should not use an external protective device to prevent it seeing such overload - just that malfunction of the external device is not a death knell to a well designed pto system.
... This friction plate type clutch is made to accommodate some slip, whether on engagement or overload. Slipping wears them. Thats the main reason you dont want the interior clutch to slip under full engine power. During implement startup it must slip some as it is engaged so that there is a graceful startup. After engagement it has to be designed such that it can take
full engine torque -
and then some - so that it will never slip under normal drive circumstances. To do this it must sustain enuf torque to stall the tractor engine. Under a slow stall or bog down situation it shouldnt slip at all. If it did we would see them replaced frequently on tractors that run rotary cutters. Shearing a 3/8" Gr5 shear bolt takes about 100HP worth of torque at 540 RPM. Since 30 - 40 HP tractors have little problem shearing these it shows that the internal clutch slips near or above the 100 HP torque rather than anywhere near the 35 HP torque. You would really like to set an
external slip clutch somewhere pretty high in the range but below where the shear bolt gives. Since a slip clutch sustains a [relatively] steady torque when slipping it would bog or stall the engine fairly promptly if set at an 80 HP torque. The internal clutch would not come anywhere near as close to slipping as it did breaking the shear bolt. If friction is set down anywhere near engine stall torque tho you definitely have potential slip clutch problems and will have to frequently adjust it for wear and be very alert to prevent burning it up if you use the equipment to capacity.
My point in all of this is that the tractor pto is pretty strong and has a clutch sized for it that has an overload slip point well above the tractor torque [so it doesnt burn up], but low enuf to slip within the strength of pto components. Still, you dont ever want it to slip except as you engage it and you always would want to use external means to keep it from seeing overloads sufficient to slip it. This would wear the clutch out and stress parts repeatedly to near their full strength. There is however, a large safe range above the tractor steady state torque and below the pto clutch slip torque. Shear bolts make use of the top of this range on ~35HP tractors. They break in an instant, and since the tractor may hardly slow you arent aware of the huge transient load on the pto system. Theres just no reason to be conservative for the tractor sake when adjusting an external
slip clutch. High in the range is
still below where those shearbolts are breaking.
My experience with serious heavy duty use of a bushog over a 40 year period on 2 different tractors is that this internal clutch protects the tractor side effectively. At a guess Id estimate this clutch is designed to slip at about 3 times the steady state torque that the tractor engine can apply and that this slippage point is within the safe region for all internal drive line components. I adjust my 5' bushog
slip clutch by dropping the bushog onto a pile of loose dirt at full rated rpm. With a 35 to 45HP tractor it should bog the tractor very quickly. You have to act quickly to keep from stalling. Next, I disengage the PTO drive and drop the BH in the dirt to stop it -
then quickly feel the slip clutch for heat. If there is none it hasnt slipped - loosen and repeat. If it is
hot it has slipped a
lot [and you may have noticed that the tractor didnt bog]. In this case the clutch is too loose and must be tightened or it will burn up quickly in heavy steady state cutting like thick grass. This is why sneaking up on a correct setting can be counterproductive.
The mating of a 5' or 6' bushog to a tractor in the 40 HP range forms a robust system that does not require coddling. However, if the bh is light duty or this size is being run by a 70 hp tractor then one end of the system is comparatively weak. You could
not set the slip clutch quite as I do because, even with the compliance of soft dirt a quick bog or stall may output from the PTO stub a transient amt of torque associated with ~3x70 HP. Heavy/medium Duty 5 and 6 foot bushog gearboxes rate at around 100HP. ... So 200, tho momentary, would be pushing it. If the slip clutch is frozen you will probably twist the telescoping pto shaft or else damage the bh gearbox. This is not necessarily too much tractor, but the situation demands a tighter balance to keep from burning up the slipclutch or damaging the implement when you encounter a situation that requires its full capability.
,,,,:confused3: ... Ill settle on replacing nothing. Its worked so far.
larry
