# Chipper Clutch Engagement



## vanlannw (Mar 27, 2002)

Hello,
I am an engineering student working on my senior design project. I have been assigned to design a hydraulic clutch engage/disengage system to replace the manual clutch system to be used primarily on wood chippers. I have had very little exposure to wood chippers and I would like to hear your thoughts on manual vs hydraulic systems.

Chipper Info
6.8L Ford V-10
Fuel: LPG - 280ft-lbs(continuous), 160HP

Hydraulic system concept
Push a button -> Clutch Engages

Thank you for your time

Nick


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## John Paul Sanborn (Mar 27, 2002)

I've often joked that the curent engaement systems are so good the only improvment possible would be automatic.

For safety reasons I think it would have to be push and hold, or a similar turn switch. Same for disengage so that it cannot be bumped in/out.

RPM lockout, will not (dis)engage unles in a certain range of RPM. Ive heard that many require a set rundown time at low rpm to cool the bearings. So to disengage you would turn down the throttle, hold the switch till a light comes on, then when the RPM and time requirment are met, the clutch disenguages.

Similar for enguage, especialy in cold weather, you get a timed start up so that everything gets a chance to warmup. Flip a switch and the computer contol waits for the engin temp to come up before enguaging the PTO, then the PTO meets the timed warmup the throttle enguages it all could be run from a single pannel and you dont have yanking the throtle handle off.


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## DDM (Mar 29, 2002)

John? thats the first ive ever heard about 
lowering the RPM until the bearings cool 
Should i start to do that on my Whisper chipper?


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## John Paul Sanborn (Mar 30, 2002)

I've been told it will extend the life of the bearing. I first heard it with new Morbarks, I started passing it around and a buddy with an early 80's model called the service department and asked if he should do it. Thier reply was that it would not hurt.


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## Treeman14 (Mar 30, 2002)

Doesn't Vermeer have that on their big stump cutters? Just flip a toggle switch to engage the clutch?


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## treeclimber165 (Mar 30, 2002)

I know from my association with many lawn maintenance guys that almost all the riding mowers nowadays have an electromagnetic clutch engagement system. Ya just wanna cringe when ya hear the blades engage, but all the companies are going to this system.


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## DDM (Mar 31, 2002)

John, I tried the lowering rpm's yesterday on the whisper chipper.It slowed the drum down a lot Faster than just disengaging the clutch. If i just disengage and let it stop by itself it takes it about 15 min to come to a complete stop.It only took it about 3 min when i lowered RPM and stopped it.


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## John Paul Sanborn (Mar 31, 2002)

Are you saying that you used to dis engage at full RPM?

Every manual I've read as a limit like 8k.

On method i've used for emergancy slowdown is to bump the clutch slightly a few times. Like when there is infeed blockage or stones vibrating in the infeed.

"How many times do I have to tell you NOT to load the thing with a shovel   !!!!"


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## Methoss084 (Apr 1, 2002)

I know that Vermeer has a huge belt type system with automatic trottle up on their BC1000's. I used to keep a fleet of BC1230's humming. Would have been great if they had some kind of Automatic type transmission instead of that phony ceramic padded clutch disc on the "Autoclutch" clutches. Is there any manufacture that does have an automatic type clutch/transmission system?


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## John Paul Sanborn (Apr 2, 2002)

Maybe that is why Nick got the assignment.

I have not seen any tow behind units with anything but manual engage.


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## DDM (Apr 2, 2002)

Yes John, Just disengaged the clutch At full Rpm It takes like 15 min for the Flywheel to stop rotating But remember we are talking about a whisper chipper. 
seems like when i lower the RPM's first the engine gains ALOT of back pressure.


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## John Paul Sanborn (Apr 3, 2002)

Does not sound good for the engine to have the load taken off of it at high RPM.

Ain't hurt it yet I guess.

Instead of turning it all the way down, maybe find a optimal level. With the some of the bigger ones I worked with if you throttled down compleatly, then it would stall out. 

When you figure out where this position is, scribe the throttle lever as the rundown position. I did this on a POS bandit I ran that had no tach on it.


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## Tom Dunlap (Apr 3, 2002)

To continue the original engineering question...Are you looking at mounting a slave cylinder to take the place of the clutch arm? That would be an interesting solution. One of the issues would be to have a sensor system to monitor and modify, the engine speed, speed of engagement, and force needed to engage the clutch. All of this is fine and dandy. BUT! Is there a real need to add on a whole new complicated system when a manual engagement seesm to work fine? The manual system seems to be effiecient enough and the procedure can be taught to new operators quite easily. 

This seems like another costly improvement for a free solution. I've owned three chippers in my career and have never had to replace a clutch. All were bought used but I babied the clutch. When I put in a rebuilt engine in my orignal chipper, a 1962 "whisper" [whoever named that chipper should be shouted at, if he can hear!] chipper I put in a new clutch because it was prudent and cheap since the engine was out. With care, clutches should go a long time in a stationary industrial machine.

Sometimes, lo tech is the way to go.


Think of an engine as an air compressor. When you're driving the flywheel you're using the comnpressed air to turn the flywheel. When it's time to shut donw you have a flywheel spinning with a lot of energy and the engine is just loafing along, even at high speed. If you throttle down, you use the engine as a brake since you're attempting to run the air compressor in reverse. Think of it in the same way as drving down a hill and downshifting rather than braking. Much easier on the machine. 

Disengaging the clutch under a load is not the best procedure for the engine because it will tend to over rev now. Might not blow it up but why would you do something that is harmful when you can do something to reduce the wear, so easily?

Have you ever heard a semi truck hit the Jake brake? They are using the engine as a compressor to slow the truck down not the tranny and brakes.


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## MidwestTree (Apr 7, 2002)

Nick - I think that you should look into the electronic clutch on a newer John Deere combine. There are two different types, one for the unloading auger and one for the seperator. Both withstand tremendous amounts of torque and both have withstood time, early '90's. I would think that this could be adapted to the chipper. I am sure that Case IH would have something similar.


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## CapitalSawmill/Vermeer (Nov 5, 2017)

DDM said:


> John, I tried the lowering rpm's yesterday on the whisper chipper.It slowed the drum down a lot Faster than just disengaging the clutch. If i just disengage and let it stop by itself it takes it about 15 min to come to a complete stop.It only took it about 3 min when i lowered RPM and stopped it.


I run a bandit 250 and used to work at Vermeer and I was taught to NEVER disengage the clutch at a full rpm it's a bad thing to do that is not necessary for multiple safety and practical reasons. While technically yes you could get away with this. For one, the engine braking is designed to slow the wheel/drum down since ita spinning a couple thousand rpms. Secondly, not many people know this, unless you've serviced chipper clutches regularly, when you disengage the clutch the throwout bearing actually pins against the pressure plate splines, the same way with a truck. The only difference is this bearing is held under spring pressure all times during disengagement. My point is why score that throw out bearing up by introducing it to a lot of Rpms when you could engine brake and disengage at a safer speed? Optimal disengagement speeds are about 1000 rpm


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## Eq Broker (Nov 8, 2017)

Another consideration when engaging a manual clutch is to make sure that the drum/disc are spinning while engaging. If not, there's a piece of wood blocking the drum/disc. Usually automatic clutches are used on tub/horizontal grinders. They're also used on stump grinders as there is usually nothing blocking them when you engage the clutch. My preference would be a manual clutch on a chipper as I would be worried that the employees would just start the automatic clutch without checking for something blocking the drum.

Hope this helps!

Dave
Global Equipment Exporters
770-420-6400


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