Stalling an HST tractor

[BOC]

I thought I would revisit this post and try to educate myself further....

I recently was tilling with my new JD3038 and 57" rototiller. I was not on virgin ground, but ground that had already been worked. I set my tiller a little deeper this time and wound up finding a fence post. The RPMs at the time of this encounter were somewhere around 2200-2500 (I don't know if you would consider this low RPM or not). It all happened very suddenly and the next thing I knew the tractor was silent. I started it right back up to ensure proper cooling.

My questions below stem from reading numerous posts and in talking with the dealer.

In layman's terms, it sounds like even with the slip clutch set correctly, a HST possesses a relief valve that acts somewhat like a "fail safe" (dealers term) and ends up killing the tractor. Is this what the bypass "relief" valve is intended for? Can I take comfort in knowing that my tractor did what it was supposed to do to prevent any further damage?

Also, to further confuse me, I was told in a HST tractor you should expect it to stall from a jammed tiller as soon as you take your foot off the pedal. I imagine this is exactly what happened since I was startled and froze. Again, is this another fail safe or just a design function? I can't imagine I am supposed to press harder on the pedal and increase the RPM's to power through it.

To sum it up, with the slip clutch set properly like the dealer ensured me it was, I am curious how to avoid this in the future if I hit another hidden object.

Clear as mud????? I guess along with being educated I was hoping to find a little piece of mind.

BOC

 

[k0ua]

It would seem to me the resistance of the tiller thru the PTO stalled the tractor. If you press harder on the Hydro pedal, that would tend to make the wheels move faster and therefore jamb more untilled soil down the throat of the tiller thereby increasing the load on the tiller and the pto and stalling the tractor engine. If you let off the pedal or raised the 3pt then the tiller would have less resistance from the unbroken ground and would lessen the load on the PTO and the engine. In other words, go slower and let the tiller have time to chew up the soil and lessen the load on the tractor and/or raise the tiller a little with the 3pt so it does not dig so deep all in one pass and thereby lessen the load on the tractor.. Thats what I think..

James K0UA

 

[TripleR]

I have the slip clutches set to where they will bog the engine down a bit, but slip and not kill the engine.

I would check the manual to see how your slip clutch should be set as opposed to just taking the dealer's word for it.

I am not sure I get the HST fail safe as the PTO doesn't run through the HST and should be no different than a geared unit or at least I can tell no difference between our geared independent PTOs and HST, but I am not a mechanic so I may be way off.

 

[BOC]

Both good points. I just want to be clear, the tractor didn't stall because I overloaded the tiller, it stalled because I struck a fence post that got tangled in the tiller. Also, my owners/operators manual for my Frontier tiller and bush hog both do not say anything specific about how to set the slip clutch. It is very vague and they just mention to check it.

 

[TripleR]

Both good points. I just want to be clear, the tractor didn't stall because I overloaded the tiller, it stalled because I struck a fence post that got tangled in the tiller.

To me at least how it got overloaded is less important than how it reaxted when it did.

I overload both our cutters, one on a L5030 HSTC and one on a M8540 HDC a few times every year hitting unseen obstacles and the engines don't die, the slip clutches slip.

 

[beppington]

Both good points. I just want to be clear, the tractor didn't stall because I overloaded the tiller, it stalled because I struck a fence post that got tangled in the tiller. Also, my owners/operators manual for my Frontier tiller and bush hog both do not say anything specific about how to set the slip clutch. It is very vague and they just mention to check it.

From what I think I got from your description, it seems normal, but maybe your slip clutch is a little too tight. Maybe, that is.

Just like stalling a stick-shift car: Put the front bumper of the car against a wall & start slowly slipping the clutch, & for a while it will slip & just start slowing engine RPM. Let the clutch out too far & the engine dies of course. I think you did basically the same thing, but all at once quickly. So 1) you either loosen the slip clutch so it can (almost) never kill the engine, which may cause some unnecessary slipping during normal operation when it encounters extra hard dirt or you're driving too fast, or 2) just know that once in a while you may kill the engine if you're not quick enough to turn off the PTO. Regardless of what you're doing with the HST pedal, if the PTO can't go, & can't slip enough, then the engine can't go, ie letting off on the HST pedal will give the engine a little more RPM & therefore give the PTO a little power boost, buy enough to grind up a fence post? Doesn't seem like it. Prob no real harm done, & prob normal operations. All IMO of course

 

[k0ua]

Sorry somehow I missed the part about the fence post, OK then well it sounds like the slip clutch on the tiller should have slipped and it did not. as that fence post was a sudden drag on the PTO. There have been several threads about adjusting the slip clutch on here, and also you might try another brand of tiller manual, I know King Kutter has theirs on line and I think they have a procedure to adjust the slip clutch in their manual.. Of course it could be a different slip clutch too. so watch out..

James K0UA

 

[jinman]

I set my tiller's slip clutch on the loose side. When you adjust your clutch, be careful to loosen each tension bolt exactly the same number of revolutions until it slips as soon as you lower the tiller to the soil. Tighten the bolts evenly until you can till normally in untilled soil with no slippage. My tiller's clutch slips when I hit any obstruction in the ground or even if I go too fast. I'd rather have it that way than be too tight. I've had a rock catch my tiller and not realize it until the clutch starts smoking. Even so, the clutch seems to have suffered no damage and certainly my tractor didn't have the stress and shock of an instant engine stall.