Converting PTO Slasher to Hydraulic

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Thank you for your reply,The horsepower required to turn my slasher is unknown unless it is relative to the capacity of the slasher,ie the slasher has a 40 hp gearbox but i am of the belief that this means that any more than 40hp tractor runs the risk of breaking the gearbox due to the torque.I am unsure if 40hp is the power required to turn it.All i am totaly sure of at this point is that i can rotate the gearbox by hand with ease and once spinning has enough inertia to keep rotating for a bit.Do you have any idea how i can measure the force required to turn it?The only way i can think of is to wrap the shaft with strong string and hang a known weight off the string and increase the weight untill the slasher turns,not sure if this will give me the info i need but if anyone has a better idea i am open to sugestions.If what you say is correct about me having around 20hp of hydraulic flow then i think this should be enough as like i said it is quite easy to turn.Another thought is to maybe go for a 1 to 1 gearbox instead of the 1 to 2 that is on it and run a motor with the same flow rate and torque but twice the rpm.Any ideas or is this getting too confusing?i know my brain is hurting.cheers.

Perhaps some 'general information' would help.

Generally speaking the horsepower requirement for a slasher is a function of width.

A 1m/3ft is typically 15 hp. 1.2 m/4ft, 30 hp. 1.5m/5ft, 50hp

The further variables being the toughness and bulk of the stubble and feed rate (tractor speed).

Slashers need some form of clutch (usually ahead of the of the gearbox in the PTO shaft flange) to protect the gearbox/blade in case of a stoppage.

The 'standard' PTO rpm of a farm tractor is 500 rpm (when engine is run at the indicated rpm) so the gearbox ratio, is to produce a 'designed tip speed' on the cutter bar, relative to the diameter/s.

Exceeding tip speed is a bad idea for a raft of reasons - as is not having a safety clutch.

2¢

Hi 34 point 5 and thankyou for your input.My slasher is 4ft with the clutch and 1-1.9 ratio gearbox,acording to tcmtech i have 22 usable hp of flow.Acording to you i need 30hp.What are your thoughts?am i trying to do something outside the capabilities of my machine?There are factory built hydraulicly driven slashers out there that will run on my machine so i believe that the right match of components will be achievable.With this information at hand and that already explained in the previouse threads are you or any other learnerd members able to give me some reasonably reliable guesses as to what capacity motor to purchase for me to get a start on my project.

This depends on whether you want to keep the gearbox versus couple the hydraulic motor directly to the slasher. With a 2:1 step-down gearbox, the hydraulic motor needs to turn 1000-1200 rpm, which would match up with ~2.34 in³ displacement. With direct, the motor would turn 500-600 rpm, with ~4.68 in³. (Or, if the gearbox is really step-up, 250-300 rpm, with ~9.36 in³.)

Hi Tornado and thank you for your input.Is what you are saying mean that because i have a 1-1.9 ratio gearbox and are wanting to achieve aprox 500 rpm i should be looking for a motor of the following size

250-300 rpm

9.36 in3

40lpm

3000psi ?

These numbers make sense to me but chances are i am still missing something.What are your thoughts?

Regarding running the motor directly to the blades that also has been on my mind but my thoughts were that ifd i already have this gearbox and clutch connected then why not use them.I have a female to female connector that will link it all up as well.

Do you think however that running it directly to the blades then i may reduce the power required and increase my chances of success?

All input greatly apreciated.Cheers guys.

You will gain a little power with a direct drive setup plus being hydraulically driven you don't need a slip clutch being your hydraulic system automatically limits the pressure thus limiting the available torque.

One common thing I have seen done to many older model skid steers that had limited axillary hydraulic power capacity was that they simply switch out the pump for one with a greater flow rating. At that point you are basically limited by what engine horsepower you have available and by what limits the hydraulic cooling system can handle continuously.

Fortunatly in most cases the cooling system is not usually an issue when higher auxiliary power is required because the propulsion system is typically at a minimum output and thus adds very little heat itself.

Hi jim, Garrie here .Have just read your thread and am considering going the same way with my P>T>O> driven slasher . I have a 50 hp bobcat and 3 foot slasher,and thinking of taking off the gear box of the slasher and powering same with hydraulic direct drive motor using skidsteers bucket(3 in 1 ) connections to power the motor. I will follow the thread with anticipation that you get an answer from someone with far greater understanding on the subject than wa.