Power rake project

[Zick]

I'm working on designing a Power rake (Aka Harley rake) for my Kubota BX2350 and needed some double checking on my setup.

I decided to go with a hydraulic motor vs PTO gearbox.

I wanted to keep the drum RPMs around ~250.

I picked out a 3.15 cu in motor that with 3.7gpm I should be seeing 271 rpms. But I wasn't sure if I would always get a true 3.7gpm so I put in an 80% efficiency which drops me down to about 3gpm and 220rpms.
Here is the motor I was looking at: 3.15 cu in DYNAMIC BMRS50H4KS HYD MOTOR

I was also thinking about running the hoses (3/8") up to the loader controls and using the FEL level to run the rake until I get around to putting in some rear remotes.
Is there anything I need to worry about with using the FEL remote?

 

[J_J]

If you use the FEL to run the Power Rake, which circuit will you use for the motor on the rake?

The lift circuit or the curl circuit.

Some curl circuit have regen and could cause you problems.

Do you plan on holding the lever or use bungee cord to lock in place.

Do you have remotes.

Does your FEL valve have PB.

You could use a true 3rd function to run your Power Rake.

 

[Zick]

I guess I didn't realize there would be a difference between the lift and curl circuit.
I was just planning to hold the FEL level for the time being.

No remotes right now, but might look into getting Kubota factory rear remote.

Not sure what a PB is for the FEL valve?

Is this the 3rd function your talking about? 3rd function auxilliary hydraulic kits for all brands of tractors and loaders! purchase online, free shipping within 1,000 miles!!
If so, I would probably just get the factory rear remotes as I believe it's about 1/2 the cost of this kit.

Thanks for your help so far. :thumbsup:

 

[Zick]

Apparently it sounds like both circuits have a regen feature.

http://www.tractorbynet.com/forums/kubota-owning-operating/233590-bx25-front-plow.html

Guess that means I probably shouldn't try using the FEL circuit. Oh well, I was trying to save some pennies.

EDIT:
After reading this thread: http://www.tractorbynet.com/forums/...26-bx25-fel-valve-curl-detent.html?highlight=
It sounds like I could still use the FEL curcuit. I would just have to make sure the level is pushed pasted the detent.


Q: Why couldn't I just plumb it so that using the Level in the down position (raising the bucket, no regen) runs the hyd motor in the correct direction?
I really only need it to spin one way (would have been this way if using PTO) but being hyd gave me the option to reverse it too.


EDIT #2
Whoops, ignore my first statement. I thought both circuits had regen but I had misread. Only the curl curcuit has the regen feature. The lift circuit just has the float feature which as long as I use put it into this mode won't give me any issues.

Sounds like this will work after all if I use the lift circuit.

 

[J_J]

You can use the curl work port that tilts the bucket up. and lock the lever down.

They make a lever or solenoid motor spool valve that if the lever is in detent, you will have constant supply, or a solenoid with a switch that will switch the the solenoid to run fwd or reverse.

Just depends on the about you want to spend to get the job done.

 

[Zick]

I would think that using the lift circuit and using the lift fuction to spin the motor correctly would be the simplest because I could just keep my hand resting on the level to hold it down.

But I'm not against looking into alternative options.
Got any links to these solenoid spool valves?

Sorry, hydraulics are not my specialty.


Btw, do you see any problem with the hyd motor that I selected?

Thanks

 

[oldnslo]

Zick,
Not trying to second guess you here but with the hydraulic drive you are talking about you will generate around 3.5 - 4 HP while with the PTO you would have 18 - 20 HP available. I think you will be very disappointed in how little torque or work this rake will do with the proposed hydraulic drive.

 

[Zick]

Zick,
Not trying to second guess you here but with the hydraulic drive you are talking about you will generate around 3.5 - 4 HP while with the PTO you would have 18 - 20 HP available. I think you will be very disappointed in how little torque or work this rake will do with the proposed hydraulic drive.

No problems w/ second guessing, that's exactly what I'm hoping people will do is to make sure I'm not calculating this wrong.

I ran some calculations and figured that with about 17hp pto that I would be making about 360-432 in lb torque at 540 rpms. While reducing the speed in half to 270 I would double the tq to about 720 to 864 in lbs.

With a 3.15 cu in hyd motor and 3.7 gpm I would have 271 rpms and 1003 in lbs of torque. But I dropped the gpm down to 3 just to factor in for decreased efficiency and came up with 220 rpms and torque should stay the same unless I'm mistaken here.

I got my hyd motor calculations from this page: Hydraulic Motor Calculations | Womack Machine Supply Company

 

[oldnslo]

Zick

Formula I have for figuring torque is torque (in lbs) = HP x 63025
RPM

17 x 63025 = 1071425 / 540 =1984 in lbs torque


the reason I questioned this in the first place is I figured pump HP by taking 3.7 GPM x 2500 PSI = 9250 / 1714 = 5.4 HP to drive the hydraulic pump.

 

[Zick]

I might be way off base on my PTO torque findings. Trying to double check them now.

I got my PTO in lb calculations from this equations, see post #3 http://www.lawnsite.com/showthread.php?t=250005

you take the engine torque rated at x rpms then take the pto rpms and divide it by x(engine rpms) = gear ratio.
Take gear ratio and multiply that by engine torque which will result in PTO torque minus parasitic/drivetrain losses.

Torque curve from this chart, post #82
http://www.tractorbynet.com/forums/hydraulics/239712-bx25-mid-pto-pump-bust-3.html

In my case, I see I make 30 lb ft at 3000 rpms.
540 / 3000 = .18
.18x30=5.4 ft lbs
5.4ft lbs = 64.8 in lbs at 540 rpms. Cut that in half to 270 should result in 129.6 in lbs of torque.