shredder/chipper attachment modification

[Marks481]

I have the opportunity to get a Mighty Mac PTO shredder fairly cheap, and I was considering welding it to a quick attach plate with a hydraulic motor coupled to the PTO drive shaft. The minimum speed of the PTO is 650 rpm, with 800 rpm being normal range.

Is this asking too much for the PTO circuit? And does anyone have a recommendation of a good model of hydraulic motor to couple to this?

Anybody have any objections to this idea? Am I better off just finding a used Troybilt Tomahawk and using that instead (which can also be found for reasonable prices this time of year). I like the idea of minimizing the number of extraneous IC engines that I have littering my garage, so making another attchment for my PT422 seems like a good idea.

 

[MossRoad]

Find out how many HP the chipper requires.

Then go to surplus center and use their hydraulic calculators to determine what size hydraulic motor you will need to get that much HP at the shaft at the required RPMs.

Then see if your PT will supply that much GPM at PSI.

I think I figured out once that the PTO on the PT425 puts out 8GPM at 2500 PSI which will work out to either 11 or 17 HP. I can't recall right now.

 

[J_J]

First, you need to determine how much horse power is required to turn the shaft. It will probably work on any PTO tractor, but there is a minimum On my Bearcat chipper/shredder, the speed is increased via belt drive, don't know how much, but real fast.
Say it takes 10 hp to run the shipper/shredded, you need to select a hydraulic motor to match the input hp, or more.

Hydraulic HP = Torque in inch pounds X RPM X 63025

There is a hydraulics calculator on the Surplus Hydraulics web site.

 

[KentT]

Tim,

Please keep us (me /forums/images/graemlins/laugh.gif) posted on your progress. I also want a chipper and would like to power it with my PT.

Out of curiousity, where are you finding these good prices in New England? I'm watching eBay and the Bargain News and not having much luck.

Ideally I'd like to find one that would handle 4" or larger, which the Troybilts will not...

 

[Marks481]

I will tell you were I am finding them AFTER I buy it... /forums/images/graemlins/grin.gif

What I really would like to modify is this BCS chipper, which is a good buy at $450, but it is way too far to drive, and I am sure shipping would kill the deal. It is pretty sweet looking.

EBay BCS chipper in Iowa

I am still wavering on the conversion, since I really need a chipper now, and I know the conversion would go slowly, since I am not a welder (yet).

Looking at the surplus center calculator, I need a 1.93 cu inch motor (957 rpm), 2.1 ci (880 rpm) or 2.6 ci (710 rpm) to get the speed I need from the PTO circuit (8 gpm). This gives about 11.6 HP output to the motor.

All the 1.93/2.6 ci low speed/high torque motors that surplus center sells won't work. Either they are rated for too little flow (6.5 gpm), or too low of a pressure (1700# cont, 2400# int).

This pushes me to high speed, low torque motors, which are a bit more expensive. The 1.7 ci Parker would probably work ($236), which would give me 1088 rpm, 2600# continuous, 21.5 gpm max. Guess I need to hunt on ebay now that I have generally figured out the motor range.

 

[Rip]

I did a similar adaptation to a BearCat chipper to run off my PT-1845. I chose to direct drive (via flex coupling) and while the flywheel originally was run at about 1800 rpm, I found that running it a bit faster (2000+) made it chip even better.

A machine shop made the adaptor bracket so the shafts lined up perfectly.

You will either need a motor that will internally free-wheel when input flow is shut off rather than try to act like a pump as the flywheel slows down, or plumb a one-way check valve between the input and return line so that the oil can free-flow back through the motor during shut-down.

My set up works much better than it did originally powered by a 20 HP Honda. It recovers much faster when it does bog down, but then there is a 45 hp Deutz behind it now. While you have less input power and flow to work with, most manual feed chippers should be able to work at least as well as before. Make sure you have (and maintain) real sharp blades and proper anvil clearance.

Good luck, Rip

 

[KentT]

Tim,

I was looking at that one in Iowa also -- but they won't ship it.

I'm also asking about one that I found for a Ingersoll/Case hydraulic tractor that would be within a day's drive...



Ingersoll chipper

 

[J_J]

Rip, I also have a PTO 3ph Bearcat chipper shredder. I have been using it with a Kubota diesel tractor. Although it works good, I am interesting in doing the same thing you did. What size hydraulic motor did you use, and what is the gpm going to the hydraulic shredded motor?. The PTO gpm on my 1445 is 16 gpm. My gas engine is also a 45 hp gas engine.

What is the make and model of the hydraulic motor?

Do you have any pictures? You know we like pictures.

That valve that allows the hydraulic motor to coast when shut down, is called a motor spool valve. It is very necessary, because the motor starts acting like a pump with all that inertia built up by the spinning blades. If it is shut down abruptly, something has to give, or break.

 

[Marks481]

seems like the ingersoll would be the way to go, if you can get it for a good price. Do you have any idea of the ratings of teh chipper (eg, is 8 gpm sufficient to drive it)?

I have been looking, but haven't seen any Ingersoll chippers for sale in New England.

 

[KentT]

</font><font color="blue" class="small">( seems like the ingersoll would be the way to go, if you can get it for a good price. Do you have any idea of the ratings of teh chipper (eg, is 8 gpm sufficient to drive it)?

)</font>
No, I'm still trying to get the specs on it. I also asked if it was a MacKissic -- who seemed to make them for most garden tractors. It's a 3" one, is all I could tell from the listing....

Ideally, I'd like to find a 4.5" one, but I'm not willing to pay over $2000 for one... too many other "tools/toys" on my wish list to spend that much on just one.