Quick drop feature on blade

Sorry for the daft question,but what exactly is the quick drop feature on the blade used for?.I’ve looked in the manual and it just shows how to disable it on the ECU and what the light on the dash is for.
Many thanks

I'm not sure of it's design purpose.
I always thought it was on them as a result of the float function.
I used the quick drop quite often.
When I did, I never stopped the blade on the way down. I leter hit the ground.

Great question. It makes the blade act like a cable blade machine. I always figured it was a hold over from the way the older machines worked. In the logging industry some of the shovels have a free swing modification installed that lets the house turn on its momentum like an old line machine. That function was installed only because some buyers had old operators that wouldn't run them new fangled machines. I killed that function on half a dozen machines after nearly smashing the side in on a company service truck.

When you say quick drop ,would that be the same as the float function?
Can anyone say what the true purpose of float is?
Ive used it for back blading my ski jumps out which is in complete contradiction to what i was taught by real operators. It was always said if the blade was meant to run backwards it would have another cutting edge on the back side.

The float function is installed in the control valve and allows all oil in the blade circuits to flow freely. The quick drop valve is installed on the top of the cylinder barrel and allows oil to flow from the rod side to the piston side as well as pulling oil from the main control valve. They are two completely different things.

nicky 68a said:

Sorry for the daft question,but what exactly is the quick drop feature on the blade used for?.I’ve looked in the manual and it just shows how to disable it on the ECU and what the light on the dash is for.
Many thanks

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I always understood Quick Drop as being for getting the blade on the ground quickly after you'd backed up with the blade raised as high as possible.

Here's an illustration of the controls on Nicky's D8T.
12A = Float, 12B = Quick Drop, 12C = Lower, 12D = Hold, 12E = Raise.



Quick drop is not the same as Float. Float is designed to allow the blade to follow the contours of the terrain underneath it when it's already on the ground.

When you push the control lever to the Quick Drop position the blade drops like a stone under it's own weight.
In fact it drops so fast that the flow rate of oil that is required to enter the head (upper) end of the blade lift cylinders is more than the maximum rated flow of the implement pump, even at zero pressure. In that case there would be a vacuum and resulting cavitation in the control valves and the lift cylinder circuit. What the quick drop valve is designed to do is take oil from the rod end of the blade lift cylinders (that would under normal circumstances be returned to the tank) and divert it to the head end of the lift cylinders to augment the flow from the pump and prevent vacuum/cavitation in the circuit.

I do not know anything about the hydraulic circuits and how they work in those two functions..
I didn't mean to infer that they were one and the same.
Both functions were very useful for me.
I always grit my teeth when someone says you should never back-blade with a dozer.
It has its purpose. Many discussions about back-blading turn into a never ending argument that I will never participate in.

The Quick Drop oil control valving has been about for years on D8's and 9's and smaller Dozers, the Recycling Valve send the lower rod side oil into the piston side it's nothing new or fancy, on the excavators the Recycling valve is now also in common use, the soft swing switch control was/is a nice thing to have CAT calling it Orifice Control, it was just a soft bleed off valve.
tctractors

The soft swing in the Cat line isn't the same thing as what we put on logging machines. What we had mirrored exactly a gear machine. Let off on the swing lever and the machine would continue to swing like there was nothing to stop it. It also took longer to start the house turning. It was installed to satisfy a few dinosaurs at the Weyerheauser company. Some of those machines ended up at smaller logging companies and caused more that a few close calls. It wasn't a nice thing to have at all.

Interesting reading her lads.
I’m still not really sure why it’s a feature.I’m not keen on dropping blades onto the floor quickly .Those bigger blades would hit the deck with a loud bang in rock.Can’t be good?
I can’t figure out how you operate it from the lever,and why you’d want to.
I suppose it could be handy for logging tractors on steep slopes in an emergency.
I’ve hired another D9T in to help out at the moment.I’ve been driving it myself as it occasionally drops the blade without warning.This happens perhaps 3 times in the whole day.
At first I’d wondered if I’d knocked the control,or if a jolt of rock under the tracks caused the blade drop to activate?I kind of knew I was kidding myself though.
Anyway,I’ve read the manual in the D8 cab and I’ve disabled the feature the last 2 shifts and it’s stopped doing it.Unfortunately,it does reset itself if you switch it off.
It’s hardly noticeable since disabling it,but I’m convinced it’s suddenly dropped an inch or so when I’m ripping.
Anyway,last night I’m sat in my pickup filling the timesheets in for the tractors and this D9T is idling down for the night and it starts to squeak somewhat.I look over at it and nothing to see.It keeps doing it and I get out and go over to it and realise that it’s very quietly raised itself up on the blade!
Now I allways switch the handbrake on these machines on,but still haven’t got used to disabling the hydraulics on them.
This tractor has been sat rusting for a couple of years and I’m in the third day of running it.
It’s sorted all the annoying fault codes and alarms out itself with a little help of a service and the tech chap plugging things in here and there.It’s calmed down and I wondered if flat batteries had been at the source of it all.
I’m going to continue driving it myself for a few more days to monitor this blade drop thing.
I’m happy to operate the thing without issues myself,but I’m wondering about issues in an unsuspecting lowloader driver or fitter catching a tap on the head from that blade.
What are your thoughts?
I’m still not certain it isn’t my bad knowledge of this quick drop feature as I’m old fashioned

It is so when pushing sticky material up a bank. when you reach the top and the blade is over the berm, you can drop the blade to the end of the travel and it stops as it slams onto the head gland and the stopping shock shakes the dirt off and if I was the boss gets you sacked.

Well,after a few slugs of tea and a biscuit,I’ve reread all your comments.
John C has pointed out that these quick drop valve things are fitted to the top of the ram.Interesting as this D9 has 2 new receant rams fitted and the rear guard is missing on the left one .
Nige’s pic of the blade control displays just how close the blade functions are to one another.Those levers are trigger happy and a far cry from a D9G control that requires 2 weetabix for breakfast to move it.
Tony’s post has just reminded me that on the old D8/9 tractors of the 1970’s you’d have to push that big blade control hard over the indent to get it to drop into float or fast drop.
Perhaps,there is some sort of valve issue on the rams,or perhaps that blade control is just too sensitive or at fault.I’m ruling out operator error as I wasn’t in it when it jacked itself up.
I’ve had 5 of these D9T RJS and TWG tractors on hire over the last 12 months and more and I’ve kept the first RJS as it’s a good old dog that I’ve grown fond of.They are all at the 30000 hour mark and have been treated badly by drivers,in-house fitters(that should be ashamed of their work) and bad management in both maintenance and their ability to put them to work(when ever they’ve been bogged,they are happy to just rag them out with a big excavator grabbing them by the muckrail and rippers.Bend fenders,ripped of pinpullers and buckled muck rails are the norm for these old tractors.
The in-house maintenance is appalling.Regular servicing of filters etc,bent mufflers and exhausts that simply aren’t fitted properly and so many grab rails and guards missing or bent and tacked back together with snot weld or cheap nasty bolts from Asda kind of boils things in my bladder.
Undercarriages are often run to total destruction resulting in various issues .
However......the positive thing about having monkeys attempting to maintain them is that Finnings end up doing most of the work and this results in many of these tractors sporting new or refurbished major componants from new air conditioning knobs,new break and deacellerator peddles to new engines and new major bogies,cannons etc.
These girls ain’t pretty,but they’ve all been trouble free and strong machines thanks to Finnings.

I can’t remember off the top of my head but is there a calibration for the position sensor that lives underneath the blade lift control lever.? That would explain a lot. Even if there is it would need ET to do the calibration.

Pushing black dirt or clay up a 3/1 slope or steeper is when the quick drop really helps shed the dirt off the blade.
I for one, would never ever drop a blade down on rock.
I was running a D8N once and the blade wouldn't stay up. It would drift down very slowly. It was impossible to cut finish grade with it like that.
I didn't repair it, but I was told something in the quick-drop feature caused it.

The pistons in the valves can get junk in them and they can get beat up and just leak. I got the opinion a long time ago that the function is just not needed and that nearly all the operators would never know if it was disabled. The other thing I notice about the function with operators that used it all the time is the blade joints, cylinder trunnions and hard nose pins and joints all get sloppy.
I seem to remember that the sensitivity of the controls can be changed from the monitor screen. Sometimes the detents in the control handles can also get worn out and the hand easily shifted.

John C. said:

I seem to remember that the sensitivity of the controls can be changed from the monitor screen. Sometimes the detents in the control handles can also get worn out and the hand easily shifted.

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I've seen that on M-Series graders, not sure it's on Large TTT though. A brief search shows nothing in the O&M.

Many thanks for all your thoughts on the problem.
I’ll keep my eye on it and get the tech kid on it if it keeps reoccurring.
I’ll certainly keep disabling it

John C. said:

The other thing I notice about the function with operators that used it all the time is the blade joints, cylinder trunnions and hard nose pins and joints all get sloppy.

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Same thing happens when the “blade shake” function gets over-used and abused.

the quick-drop pistons are also probably fluttering somewhat whenever the blade is used in the float position-ie. backblading or snowplowing and brush clearing on frozen ground but i'm only speculating

Update,I’m currently disabling the quick drop and float feature every morning on this D9 and it seems to be behaving itself.
I’ll watch it