Hydraulic Chipper/Shredder Project

[MossRoad]

With a hyd motor, the rpm will decrease with an increase in displacement, with a set GPM. Perhaps a comprise could be made to lower the rpm for more displacement, and moee torque. The chipper is going to chip, at whatever speed, but there is a desired speed for efficient chipping. The 3ph Bearcat that I have not only chips, but shreds. The rpm of the PTO is increased, but I don't know the rpm.

Maya be something like this.

https://www.surpluscenter.com/item.asp?UID=3516020513353108&item=9-7073-100&catname=hydraulic

That is a nice motor. Just about matches the specs of the PTO on the PT425 at 1800 RPM.

So I guess the O.P. needs to determine at what RPM the original chipper shaft turns...

 

[smartguyz]

Hi David,

I'm having trouble trying to get the spec on the RPM of the original engine. According to this spec table, the newer units will do 2714 "chipping hits per minute".

MacKissic Inc.

I believe that there is only 1 chipper blade on the chipper. I am making the assumption that the pulleys are in a 1:1 ratio.


This 'see-through' photo of a demo unit seems to imply that there is only 1 chipper blade.

A & D Reisman Lawn Service - MacKissic MightyMac

Thus, it seems that a 2700 RPM is a decent guess. I could always call the factory and talk to an engineer who would know for sure.

-Rob

 

[MossRoad]

Yeah, the shredder is a bunch of hammers flailing around while the chipper is usually one or two blades mounted on a heavy flywheel.

 

[smartguyz]

Hi guys,

Well, I picked it up. Here are some photos. The 5HP Briggs and Stratton gas engine is just toast. I bought a few parts and tried to resurrect it, but I really don't think it will be worth it. I've already spent $25 on parts, and it will probably take another $50 before I finish IF I can get the gas motor working again. As you can see by the photos, it's a wreck. I don't think I've ever seen so neglected an engine. It's clear it sat outside for years before I picked it up today. Water in the gas tank, rust everywhere, ick! When I pulled out the 'foam' air filter, it was like styrofoam, and was falling apart in my fingers. Ugh! It's so corroded that the pushrod for the ignition points is rusted and stuck inside the engine - that's why there's no spark - the points don't have anything to ride the camshaft and break the points open, if you are familiar with how these engines work. A mess. I could buy the breakerless ignition and work around this problem, I'm not convinced its worth it.

Anyway, I picked up the whole contraption for $70, and despite the neglect, the shredder itself is quite sturdy. It is made of sheet steel with hefty steel hammers and a thick steel filter grate. It's sturdy, like a PT! A similar item from MacKissic today runs around $2000, although newer units have a chipper as well as the shredder.

You can see that if I take out the gas powerplant, and put in a hydro motor with the centrifugal clutch-pulley on it, then it should work. I'll need to fabricate some kind of sliding mount for the hydro motor (the v-belt tension is adjusted by moving the gas engine back and forth on its engine platform.) and I'll need to drill off the pulley (it's rusted on the gas engine) and tap it and reattach to the hydro motor.

The photos speak for themselves.

I admit it looks pretty rough, but it's all surface rust, and the mechanics are sound. The bearings on the shredder have no play and spin freely. The hammers actually don't look very used. The wear is completely due to exposure to elements.

Your input is solicited.

-Rob

 

[smartguyz]

You already know that the PT425 main PTO is rated at 8GPM@2500PSI.

You have to determine how many RPMs you want the chipper shaft to turn at.

The hydraulic calculator on the Surplus Center site will take your flow (8gpm) and your desired RPM (3600 or 1800 or whatever you choose) and calculate the size of the hydraulic motor that you need to achieve the desired RPMs. This, of coursed, is based on 1:1 pulleys.

For instance, 8GPM flow and 3600 RPM shaft speed will require a 0.5 cubic inch motor displacement while 8GPM flow and 1800 RPM shaft will require 1.0 cubic inch motor displacement. However, you could change that by gearing system up or down with pulleys.

For instance, lets say your 1" hydraulic motor tuns at 1800RPM and you want to turn the chipper shaft at 3600 RPM. You would need to put a pulley on the chipper shaft that is 1/2 the diameter of the pulley on the hydraulic motor.

So, the question is, what do you need?
A larger displacement hydraulic motor turning at less RPMS geared up with pulleys...
A normal displacement hydraulic motor turning at the same RPMs with no gearing of pulleys....
A smaller displacement hydraulic motor turning at higher RPMS geared down with pulleys....

That is the question I would like the TBN membership at large to answer... should we use a larger displacement motor or a smaller displacement motor?

OK, so Moss (per normal), gives us a baseline for calculating this project. Here are the inputs. As you can see from the photos,

- The engine pulley has a diameter of 3.5".
- The shredder pulley has a diameter of 5"

This means that the shredder hammermill is rotating at a speed of 3.5/5 of the engine/motor speed. This calculates out to 70% of the engine speed.

So, if the typical Briggs and Stratton 5HP Horizontal Shaft engine turns at 3600 RPM, a 70% reduction would give 2520 RPM. That's pretty close to the estimate from the spec sheet of 2714 RPM. I wasn't real exact on my measurements of the pulley diameter, and I could easily be off by 5%. So, I think we can go with a 75% ratio.

OK, so that does mean that we want a hydro motor that turns around 3600 RPM or thereabouts.

Where's that nifty hydro motor calculator on the website?

-Rob

 

[smartguyz]

Allrighty then.

According to the equations on the SurplusCenter.com,

Hydraulic motor speed (RPM) = 231 x GPM / motor displacement (in3/rev)

So,

3600 RPM = 231 x GPM / motor displacement (in3/rev)

GPM / motor displacement (in3/rev) = 3600 / 231 = 15.58 cubic inches/rev

Given a target RPM of 3600, 2500 PSI and 8GPM from the PT425, this means I need a

0.5 cubic inch motor, which will give us 3696 RPM at 8GPM.

Also, this results in 199 inch-pounds of torque at 2500 PSI and 14 HP.

OK, looking at Surplus Center, they don't sell anything that looks like that. A 0.5 cu in hydro motor is small and spins really fast with low HP and torque.

What am I doing wrong?

The motor pulley has an integrated centrifugal clutch, which kicks in when the motor gets to a certain speed. My understanding is that this makes it easier to pull-start the chipper. We could move to a 5" diameter pulley, and eliminate the centrifugal clutch, since we don't have that issue with the PT.

Ideas?

-Rob

 

[smartguyz]

OK. Still thinking...

I could do the following:

1) Use a 1 cu in hydro motor, as suggested: https://www.surpluscenter.com/item.asp?UID=3516020513353108&item=9-7073-100&catname=hydraulic

2) Use a 7.5" pulley on it. Coupled to the 5" driven pulley, this will give us a speed up in RPM making the 1800 RPM of the motor become 2700 RPM.

3) The hydro motor has an output rating of 10HP. This is a massive 2x increase in HP from the 5HP Briggs & Stratton, and will make it just like the newer units, which have similar HP engines.

4) I can use a plain pulley instead of a centrifugal one, since we're not worried about needing to start the engine by hand.

So... Question time (thanks for your patience - I feel like such a newbie):

A) Does this make sense?
B) If so, what kind of mounting bracket can I purchase or easily fabricate?
C) What kind of relief valve should I use? I browsed the SurplusCenter site, and it is confusing to me.
D) What kind of hoses and couplers do I need?

Any other ideas? Am I insane to try this?

-Rob

 

[J_J]

Just to clear things up, since it doesn't have a side chute, that is only a shredder, It does not chip. I thought you had a later model of the one that I had. I have used both a gas engine, and electric on the shredder and it ran so so. I believe the blades can be reversed. I think you will have to sacrifice some rpm for torque. These people also have some of the products you might need.

Bailey Hydraulic Cylinders Manufacturer

You will need 3000 psi hoses, some QD's, and a relief valve for the motor, and QA plate for the shredder.

https://www.surpluscenter.com/item.asp?UID=2100020706320710&item=1-3242&catname=hydraulic

If you want variable speed, you can add a flow control valve.

https://www.surpluscenter.com/item.asp?UID=2100020706320710&item=9-4169-10&catname=hydraulic



https://www.surpluscenter.com/item.asp?UID=2100020706320710&item=9-6135-50-H&catname=hydraulic

Good luck.

 

[3238dpw]

I am following this thread with great interest. As you can see I have the same project going on and I am happy to let Rob figure it all out for me. Actually I have been thinking about mounting it on a Garden Tractor like the last pic. Not sure. Either way it is one less engine to worry about.

Unfortunatly my project is a little low on my list of things to do. So I am not going to be working on it for a little while.

 

[MossRoad]

As J_J mentioned, it appears to be only a shredder, not a chipper/shredder.

Having operated a shred only unit in my youth and I gotta tell you I would not proceed with the project. Burning fuel to shred leaves that will rot on their own with little labor on my part never made sense. My dad made me operate the unit for days on end each fall. Rake, haul, dump, pick up by hand, put in shredder, repeat.

I finally convinced him to push the leaves into a corner of the yard and let them rot into compost. I still do that in my yard to this day, only with a twist. I mow the leaves with my PT, which shreds them, and I TOW a Brinley lawn sweeper cart behind the PT as I go. The leaves get shredded AND picked up in the same motion. Then I dump them in a corner of my yard and use them in flower beds, garden, etc... as needed.

I don't mean to be a downer. If you have a use for the shredder, I think you have the perfect donor unit there. Low, low cost and should be easy to swap out the gas motor for a hydraulic motor.

I think your calculations are correct. You have to decide on the size of the motor and pulley. You might want to pose the question in the hydraulics forums as to if it is better to use gear up, gear down, or 1:1 on the motor and see if anyone can give you an advantage for either way to achieve the proper RPM of the shaft.

 

[3238dpw]

As far as I am concerned, I want it more for the chipper and to throw in a pumkin or something like that every now and then.

My leaf pile I use the roto tiller to mix it and it breaks down the leaves very quickly. The first pile of leaves I make from early in the fall season is almost broke down by the time I make the last pile in late fall. This is done so fast just by mixing it regularly with the tiller. One year when it was in the low 40s in december the pile was cooking away at 147 degrees ( I have a thermometer)

By the way that is the picture in my avatar with the steam coming off the pile.

 

[smartguyz]

As J_J mentioned, it appears to be only a shredder, not a chipper/shredder.

Having operated a shred only unit in my youth and I gotta tell you I would not proceed with the project. Burning fuel to shred leaves that will rot on their own with little labor on my part never made sense. My dad made me operate the unit for days on end each fall. Rake, haul, dump, pick up by hand, put in shredder, repeat.

I finally convinced him to push the leaves into a corner of the yard and let them rot into compost. I still do that in my yard to this day, only with a twist. I mow the leaves with my PT, which shreds them, and I TOW a Brinley lawn sweeper cart behind the PT as I go. The leaves get shredded AND picked up in the same motion. Then I dump them in a corner of my yard and use them in flower beds, garden, etc... as needed.

I don't mean to be a downer. If you have a use for the shredder, I think you have the perfect donor unit there. Low, low cost and should be easy to swap out the gas motor for a hydraulic motor.

I think your calculations are correct. You have to decide on the size of the motor and pulley. You might want to pose the question in the hydraulics forums as to if it is better to use gear up, gear down, or 1:1 on the motor and see if anyone can give you an advantage for either way to achieve the proper RPM of the shaft.

Hi David,

Thanks for the input. I thought about this quite a bit before deciding to proceed. I can't afford a big chipper shredder at this point in time, and the only thing available this cheap (i.e. $70) was the broken-down shredder. I did watch a YouTube video where someone with this exact model shredder-only was putting what appeared to be about 1" branches and such into it, and it absolutely shredded them. I calculate that perhaps 80% of everything I am pruning on my acreage is in that size range. If all it could do was leaves, I'd totally agree. However, it appears from everything I've read that this unit, properly powered, can do 1" branches and shrubs, weeds and such.

I think I'm going to modify my strategy. I'm going to go-ahead and spend the extra $25 and repair the engine, see how well it works, and if it meets the promise of being able to actually shred something close to 1" or more, then I'll look at doing a hydro-power project. If not, then I'll stop there.

Thanks so much you guys!

-Rob

Here's the video that convinced me this could work. This is the exact same shredder.

YouTube - MacKissic shredder attachment

 

[smartguyz]

I also agree with MossRoad that using such a unit for 'leaves only' seems really crazy. Personally, I keep a small push mower around for picking up leaves only. I just bag the leaves, and the mower does a very good job of picking up the leaves, cutting them a few times, then packing them into the collection bag. I usually follow the mower around with the PT, using the large bucket to allow me to dump the mower every few feet, since it fills up pretty quickly.

I actually bought a snapper riding mower that did a great job picking up leaves, but it died an ignominious death, with the gearbox grinding itself to death. Oh well. I donated it to the local repair shop for parts.

I also purchased a tow-behind lawn sweeper like MossRoad, but it only got used once a year, and seemed like quite a waste. PLUS, the lawn sweeper could not be 'disabled' when going over non-lawn areas, thus it just kept sweeping no matter where I towed it. Pretty annoying. I returned it to the place I bought it from in mint condition.

I know I'm off-topic, but the biggest problem on the property right now is WAY too much for the burn pile, and its all clippings, weeds, and little shrubs, with the occasional large branch thrown in.

-Rob

 

[MossRoad]

Here's the video that convinced me this could work. This is the exact same shredder.

YouTube - MacKissic shredder attachment

Jeez! Kinda like a blender with the lid off!

 

[smartguyz]

Jeez! Kinda like a blender with the lid off!

Yeah, pretty nuts, eh? It would help if he actually used the debris shield...

-Rob

 

[MossRoad]

Yeah, pretty nuts, eh? It would help if he actually used the debris shield...

-Rob

Yeah, I remember using our beast when I was a kid. It had a top load chute. I was feeding leaves into it and they got stuck. I used a rake handle to push them down. Looked just like those sticks.

Our shredder had two rotating lawnmower looking blades about 10" long stacked one over the other about 2" apart. They rotated parallel to the ground on the shaft of the vertical shaft engine. Leaves went in, mulch came out. It would fling them pretty darn far with quite a bit of force. You drop a rock in there and it had the potential to kill you with a head shot. Just like a lawnmower only two blades. Scary machine. Made by Sears!
It had a garbage bag attachment so you could mulch directly into garbage bags. However, you ever blow a coton ball into a jar? Can't do it. The thing would blow half the leaves back out at you. If you dropped a stick in there, it would blow a hole in the bag. You had to use "special" heavy duty Sears leaf mulcher bags. And if you filled them, you could not lift them. At least I couldn't. Overall, the machine was dangerous, scary and very good at shredding the $%^!! out of stuff. Tim Taylor would have been proud.

 

[smartguyz]

Yikes! That's a scary story. Sounds like you were preserved with all your limbs intact by the mercy of the Almighty. I'm surprised Sears didn't get sued big-time for such a contraption.

UPDATE: I was able to get the gas motor up and running after rebuilding the carb and rebuilding the ignition. Both were clogged/shot/shorted, etc. However, it is spitting flames out the muffler, leading me to believe that the exhaust valve is pretty shot. That's it, I'm giving up on this thing. I don't think its worth pulling it apart. Maybe I'm wrong.

I'm leaning towards buying a better platform (i.e. one that includes a chipper) if I am going to go to the expense and work of converting it to a PT Hydro-powered unit. Although the engine is on its last legs, I was able to run half a dozen branches (up to 3/4") into it, and it gobbled them up no-problem. It spit out tiny little mulch chips. Noisy, but very effective.

OK, I'll sit back and noodle on this some more. Nonetheless, it was fun to resurrect the engine, even though its pretty worn out. Reminded me of auto shop in High School.

Your input and comments are still solicited!

-Rob

 

[ponytug]

Congratulations on gettting the engine going! These look like pretty amazing chippers.

Just to be a mild contrarian...given the expense of a PT and of a PT engine, would it be better to have this chipper on a Q/A plate, but self powered, so it could run unattended, and without the wear and tear on the PT?

Just a thought.

All the best,

Peter

 

[MossRoad]

Congratulations on gettting the engine going! These look like pretty amazing chippers.

Just to be a mild contrarian...given the expense of a PT and of a PT engine, would it be better to have this chipper on a Q/A plate, but self powered, so it could run unattended, and without the wear and tear on the PT?

Just a thought.

All the best,

Peter

You know, I think about that often... a self powered machine VS an attachment to the PT.

I guess we all have to identify our needs and uses and then determine if we would be better served by a machine with its own power source or by an attachment to the tractor.

Self powered allows you to use the tractor to bring stuff to the machine while it is running. A chipper/shredder and a log splitter come to mind. Another stand alone machine would be a generator, as when we have power outages, they are usually due to storm damage or snowfall, which I want to use the tractor to clean up.

However, the trade off is you have another engine to maintain. Personally, I want to have as few engines to maintain as possible. For instance, my firewood gathering... I bring it all home already cut into pieces and pile it up until splitting day. On splitting day I split and stack in the same place. No need to have a tractor available to move things around, so I could power the splitter from the PT as an attachment. If I had a chipper, I would probably gather all the stuff to be chipped into one pile, then chip it into my compost area directly, so I could power a chipper from the PT as an attachment as well.

Lots to consider for each person.

 

[smartguyz]

Hi guys,

The curiousity got the better of me, so I removed the cylinder head (surprisingly easy to do!) and took a look at what's going on in there. The valves move freely, and do seem to move up and down properly. They do not appear to be damaged. They were quite carboned-up, so I used some PB Blaster on it (Wow! That just melts the carbon!) and cleaned it all up. I then used the dremel tool with a little wire wheel and carefully cleaned off the carbon on the valve seats and the valves themselves. After all was pristine, I put it back together.

No joy. It's still spitting flames. My thoughts are that it is worn out, and the valve spring is not strong enough to keep the valve closed, so during the power stroke the hot gasses (with flames!) are leaking past the exhaust valve. At least in my mind that's what appears to be happening. Feel free to chime in...

So, I'm back to thinking about powering this thing hydraulically. Perhaps the least expensive thing to do is to put a non-variable control motor on it, with a proper relief valve. Couple of questions:

1) If I get an inline relief valve, how do you tie the bypass back to the return? Is there some kind of 'joining' device?

2) If I put in the variable control, then again, how do you tie the bypass back to the relief bypass and the return line?

I took "Fluid Mechanics" in High School and I think I understand how this stuff works, but I can't seem to locate stuff on the Surplus Center sight, or at least they assume that the reader knows exactly what they need and what it is called.

Thanks guys!

-Rob