Quick Dump hesitation

[Chris527]

Hi Gang,

I have a TC-30 W/7308 fel and guess what..same thing. It surfaced about a year after i had my tractor. I asked my dealer about it and he sugested it might be the quick coupler is sticky on that circut and mabe to try to disconnect and re-connect. Well it did not help. I actually took the cover off the valve body and looked everything over,all the linkages seemed tight and in working order. I have just lived with it for now, it seems espically bad when moving snow in the winter time in the colder weather and that might be a clue to the problem. I actually think it is a defect in the valve body if so many of us are having the same problem. I have noticed when i go to use the quick dump there is a delay and the bucket just flops fast like there is no hydrolic fluid in the cylinders just BANG. That might be a air problem in the circut someplace but for now i will just live with it until i get time to play with it.

Chris

 

[Chris527]

Hi Again all.

I have just read mads link on hydrolics. It is a great post on the how and why. I guess my question is this. Why did this work flawlesly for one year and i did move a ton of dirt and was very happy and just like overnight this problem devolop. Their has to be somthing wearing or defective in the circut if this is happening. Just a thought.
Chris

 

[jinman]

Mine has had the hesitation always; was told it is normal. If it has the regen feature; why are they doing it?

Dave, I think the problem is that with the regenerative feature, oil is allowed to bypass the normal circuit from the curl up side to the curl down side. With the weight of the bucket (and weight in the bucket), the effect is that there is slight cavitation. The pumped fluid can't keep high pressure on the circuit because the weight in the bucket can "draw" more fluid than the pump can supply. The delay until the pump can catch up to the falling weight in the bucket is the delay you are seeing. It's the switchover from vacuum in the lines to pressure. By having the rpm higher, you allow the pump to produce more flow and reduce the effect of the cavitation.

That's my explanation and may have flaws.

 

[dqdave1]

Jinman; I agree with what you stated. I am sure that is what is happening; I have a 68" bucket , which taxes the unit. Too bad the regen system wasn't designed to keep up; A little better flow rate would help but I understand engineeering and one thing leads to another, plus price increases. I have learned to live with it. I guess I hope that hydraulic engineers from CNH read these forums and try to solve our "problems"

 

[JerryG]

The dump cylinders are captivating. They do that when the weigh in the bucket pulls the bucket down faster than fluid is going into the backside of the cylinder. Air separates from the fluid and causes the slow down. The regenerative valves will eliminate it almost entirely if the lever is put directly into the regenerative position when you need to dump. If you use the regular dump position to start and then go to the regenerative position, then the separation has already taken place and the slow down is already set up. If a heavy load is in the bucket it is important to go directly to the regenerative position if you want to dump fast and over come this lag.

 

[SacandagaBrad]

If you use the regular dump position to start and then go to the regenerative position, then the separation has already taken place and the slow down is already set up. If a heavy load is in the bucket it is important to go directly to the regenerative position if you want to dump fast and over come this lag.

BINGO! That is how I have learned to use mine. If you are trying to feather a load out, like spreading gravel or dumping stone on drain pipe a little at a time and then dump the last bit quickly, you are going to experience the lag. But its still a very handy and efficient feature having the two dump speeds so that you can do fine-touch work or quick dump for high volume work with these machines. Just takes a little getting used to.

Brad