Hydraulic Chipper/Shredder Project

[smartguyz]

Hi guys,

It's been a long time. I've been thinking of doing a hydro chipper/shredder project to take advantage of the strong hydralic PTO on my 425.

I may have access to a Mighty Mac Chipper/Shredder as shown here:

MacKissic Inc.

It is intact, but has a dead engine.

I spoke to one of their engineers on the phone, and he said that as long as I put in a powerplant with similar HP and speed, and lined the pulleys up so that it is straight - it should work just fine.

I like this design, because it seems I could mount a hydraulic motor in place of the gas engine, and end up with a hydro chipper!

Here's the question - what size/kind of motor do you think I should get for the 425 to run this, and where's the best place to buy such a beast?

Thanks so much.

-Rob

 

[J_J]

First, you need to determine the rpm of the spindle of one you would like to convert. It will then be easy to find a motor that will produce that rpm and torque. I believe your mower deck uses about a 3 cu in motor. Give me the rpm desired, and the GPM you have available.

https://www.surpluscenter.com/hydraulic.asp?UID=2009081811133609&catname=hydraulic

Baileynet.com

 

[J_J]

The 8 GPM, at 2500 psi for the 425 requires about 14 HP, and when transfered that energy to the hyd motor,and should develop about 11.9 HP.

I am also thinking, that one of the PT owners converted a chipper, or blower awhile back.

 

[3238dpw]

JJ I think this is the thread you were talking about.

http://www.tractorbynet.com/forums/power-trac/111083-rip-your-chipper.html

 

[smartguyz]

J.J.!

Great to hear from you. Thanks for responding. I believe the engineer from Mighty Mac said that the new ones have an 11HP Gross rating. I think that a 14HP would a bit stronger, but would likely work just fine. I don't know what the RPM would be. I would likely need to guess.

-Rob

 

[smartguyz]

JJ I think this is the thread you were talking about.

http://www.tractorbynet.com/forums/power-trac/111083-rip-your-chipper.html

Thanks, I've read that thread. I'm interested in the Mighty Mac 12P primarily for the following reasons:

1) Uses a fractional HP v-belt = automatic safety. If a limb gets stuck, then you will mangle or burn the belt, but it will give you a fighting chance to shut the thing down before something really bad happens.

2) Looks like I can likely mount a hydro motor on the motor mount platform very easily.

-Rob

 

[smartguyz]

The 8 GPM, at 2500 psi for the 425 requires about 14 HP, and when transfered that energy to the hyd motor,and should develop about 11.9 HP.

I am also thinking, that one of the PT owners converted a chipper, or blower awhile back.

I'm not very good at this. I'm going to guess that a typical engine of that type would have a max RPM of around 2200. It would probably be around an 11-12 HP unit.

So... what kind of hydro motor should I get for this project?

-Rob

 

[BobRip]

Rob, don't break a belt to protect the chipper, put a relief valve in or use the existing one in the PT. That is the beauty of hydraulics, a nondestructive safety. Don't ask me how to do this. Can someone else suggest something.

 

[MossRoad]

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?

 

[J_J]

Most of the small engines will turn at to 3600 rpm. If you have the chipper with engine, look at the pulleys and determine if it is 1 : 1, or whatever. That will be the rpm you need for the hyd motor. To protect the hyd motor, a relief valve should be used across the motor.

Determine the shaft rpm of the chipper at max power, I think we know everything else.

Maybe something like this, geared up to match chipper shaft rpm.

https://www.surpluscenter.com/item.asp?UID=3508020416414429&item=981-1025&catname=hydraulic

 

[BobRip]

To protect the hyd motor, a relief valve should be used across the motor.

Thanks J_J, that's what I was looking for. Remember you are not trying to protect just the hyd motor, you also want to protect the chipper. Chippers are subject to a lot of abuse.

 

[smartguyz]

Wow, this is great info. I've been away for so long, I've forgotten how much you guys know about stuff like this. Thanks for chiming in so quickly to advise a 'prodigal' TBN member. I'm going to run some more calculations and see if I can acquire that broken chipper/shredder.

-Rob

 

[Gravy]

I'd try to find a 3600rpm motor and direct couple it. Any sort of gearing or belt drive wastes some power due to frictional losses.

 

[J_J]

A direct drive hyd motor using 8 GPM, and turning at 3600 rpm, will have a displacement of .513 cu in. The torque on that motor using 2500 psi, will only be 204 in lbs. That does not seem like enough torque.

One needs to look at the torque produced by a 11 or 14 HP gas engine to compare.

 

[MossRoad]

A direct drive hyd motor using 8 GPM, and turning at 3600 rpm, will have a displacement of .513 cu in. The torque on that motor using 2500 psi, will only be 204 in lbs. That does not seem like enough torque.

One needs to look at the torque produced by a 11 or 14 HP gas engine to compare.

That's why I asked would it be better to use a larger displacement motor running at lower RPMS for the added torque and then put a larger pulley on it to get the chipper shaft up to the proper RPMs.

 

[BobRip]

That's why I asked would it be better to use a larger displacement motor running at lower RPMS for the added torque and then put a larger pulley on it to get the chipper shaft up to the proper RPMs.

The larger pulley would raise the speed, but lower the torque at the chipper shaft. There is no such thing as a free lunch.

 

[MossRoad]

The larger pulley would raise the speed, but lower the torque at the chipper shaft. There is no such thing as a free lunch.

I agree about the free lunch, but which of the three choices would be better?
1. A smaller displacement high speed hydraulic motor with a small pulley.
2. A larger displacement low speed motor with a big pulley.
3. A perfectly sized hydraulic motor (according to the calculator at Surplus Center) with either a direct connection or 1:1 pulleys.

 

[ponytug]

Repeat after Bob, while clicking your ruby slippers together;
"There is no place like home, there is no place like home..."

Or such a thing as a free lunch.

I would opine that for a chipper, all the below options are equivalent, except #3A. The directly connected motor will be subjected to extensive shock loading, and will need to be designed for it.

The v-belts and slippage will help shield the motors in the other cases.

The chipper speed is fixed, as momentum is important, and one would like to operate at the design knife velocity.

The math suggests that the 425 has more than enough PTO power to run this chipper.

All the best,

Peter

I agree about the free lunch, but which of the three choices would be better?
1. A smaller displacement high speed hydraulic motor with a small pulley.
2. A larger displacement low speed motor with a big pulley.
3. A perfectly sized hydraulic motor (according to the calculator at Surplus Center) with either a direct connection or 1:1 pulleys.

 

[BobRip]

I agree about the free lunch, but which of the three choices would be better?
1. A smaller displacement high speed hydraulic motor with a small pulley.
2. A larger displacement low speed motor with a big pulley.
3. A perfectly sized hydraulic motor (according to the calculator at Surplus Center) with either a direct connection or 1:1 pulleys.

I would go with the 1:1. That if needed it's easier to go up or down in speed.

 

[J_J]

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 more 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.

Maybe something like this.

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