boom mower project

[nealfris]

For anyone interested, this is my winter project.
My property in VT is very steep and comes with the usual honeysuckle, saplings and wild grape vines. I hope this thing will reach over barb wire fences also.
Making sure the weight is kept down to limit the need for counter weight, the project begins.
Starting with an old iron JD 30" mower deck with 28" blade. After all the usual trial and error bugs are worked out of this thing, if the mower deck proves not worthy than I'll rebuild the deck. The tractor/ BH arm test was better than expected. The tractor had no tipping or stress issues at all. I am a little concerned about the stress on the curl piston on the arm.
My BH is powered off remotes rather than a pto pump. The only negative was the levers on the BH were jumpy with the mower fully extended. I think installing flow restrictions on quick connectors while using mower will help.
As you can see, this unit is not powered yet. I have asked for help from the Guru's on the hydraulic forum about a hydraulic motor for power.
To jump off topic for a minute, I plan on adding a 3 spool valve above my loader valve for remotes. I will be putting a grapple on the front and that leaves me two more remotes to the back for TnT.
Back to the project. I was told the 6.9 gpm and only approx. 14 hp left for torque out of 30 hp motor was far less than was needed for any blade tip speed. However, The feed back was assuming the Hyd pump would turn the blade directly. This is not the case. I intend on off setting the motor from the blade shalt to allow for a sacrificial belt and the ability of stepping up blade tip speed. I was very grateful for the input but I could not get a response on that scenario. I am unsure on the math and have little knowledge about hydraulic systems. Please help!
That led me to think of adding a pto pump which I was told would now give me closer to 20 gpm. A lot of money to spend you might say. Well here's the other issue; my BH working off the remotes is mediocre at best. All I here all day is the relief squeal. I have owned a little Terrimite rental BH for 20 years and it would out dig my Woods 750 all day long powered by only a 18 hp Briggs. So, the boom will not be used very often once I get my property manageable and apply herbicides. At that time I would switch my pump over to operate the BH for (hopefully) much better performance.
Then again part of me thinks; put a lawn mower engine in it and move on. The problem with that of coarse is oil starvation. the deck will only be able to be tilted slightly.
I would greatly appreciate any and all input and advice.

Thanks, Neal

 

[nealfris]

opps, pictures didn't upload

 

[beenthere]

Clever build.
I'd think you wouldn't have to worry about the curl piston, as it seems it will always be in tension, and never compression where it might bend.

My only reservation would be the deck blade throwing debris back at you as the operator. But adequate protection for your safety would likely be in your plan.

Good on the project.

 

[Rustyiron]

I like your idea, I have thought of making a similar type mower for reaching in and clearing around stumpy/rocky area's but I also am aware that there are some expensive components involved that need to be properly sized and trial and error (my usual method) could get expensive! From what you said in your post it sounds like you may need to go with an aux, pump, that means a hyd reservoir. of prolly 20+ gal. I think that is the rule of thumb when sizing a res. ( 1gal. res for each gpm pump) for running cylinders and that hyd. motors may require even more (tank size) due to the heat that motors create. You see where I'm going with this, hanging a 20+ gal. tank & new pump and valves, hoses.... were talking alot of weight and space tucked in around your hoe. I wish that I new more in this area, I think hydraulics are wonderful, sending horsepower thru a hose!! how nice is that! Keep doing your homework! There must be a way. The point that I wanted to make when I read your post (before I got distracted in my other thoughts) was on your coment of hyd, power that you have available, it made me think of what I do know is, I have a 110 HP skid steer with 38gpm @ 3500psi available at the aux hyd. I have an factory built hyd. mower for it and it, and it's not to hard to bog it down in the heavy stuff.
I wouldn't worry about your curl cyl. or a belt drive to absorb shock I think that the hydraulics are forgiving enough for that concern, but hopefully sombody will respond that actually knows what he's talking about. LOL!
Good luck and keep us posted.

 

[dfkrug]

I was told the 6.9 gpm and only approx. 14 hp left for torque out of 30 hp motor was far less than was needed for any blade tip speed. However, The feed back was assuming the Hyd pump would turn the blade directly. This is not the case. I intend on off setting the motor from the blade shalt to allow for a sacrificial belt and the ability of stepping up blade tip speed. I was very grateful for the input but I could not get a response on that scenario. I am unsure on the math and have little knowledge about hydraulic systems. Please help!
That led me to think of adding a pto pump which I was told would now give me closer to 20 gpm. A lot of money to spend you might say. Well here's the other issue; my BH working off the remotes is mediocre at best. All I here all day is the relief squeal.

Interesting project, Neal.

I have sized some hyd motors for PHDs and a concrete mixer.

You have a limited amount of hydraulic power that you can deliver with
your tractor's engine. You can not increase that with a PTO pump or
using a step-up pulley system. In the latter case, which seems to be your
current plan, sizing the motor correctly will give you the blade speed that
you want. A lower displacement motor will turn faster than one with a
higher displacement, for a given flow rate. You must get the rotational
speed correct first. Varying the displacement of the motor (where
flow and pressure limits are the same) is like changing the gearing in a
gearbox or pulley system. The only reason NOT to use direct drive
between your motor and the load is when you want to offset the motor,
or you are trying to use the wrong size motor. For example, in the case of a
posthole digger, direct drive caused height/depth issues, so I went with
a right-angle gearbox.

Then the question becomes, what is the power demand that my blades
will have, chopping thru the brush you expect? You can always cut too
big of a bite. The question is, what will be acceptable performance? I
would think that 2000psi at 7GPM will be good enough for some brush, but
you may bog the engine if going too fast.

 

[toolbox5]

i made somthing similer i used a 2cycle lawn boy engine and i fabed a mower deck it works pretty good except for the engine don't run very well , needs tune up . i also didn't put an extension on . you've got a good start , 2cycles don't have a sump to starve but if you hold it on it's side too long i think it screws up the float position . i just cut quick and try to get back to level or close to it and keep cutting .

 

[J_J]

This PTO pump will get you to where you want, using only 18 HP. 11.4 GPM'sat 2000 psi

https://www.surpluscenter.com/item.asp?item=9-1047-2-C&catname=hydraulic

Some one makes a lawn mower called a FlyMow, that float on top of the ground and is used to cut ditches, etc. It uses a two stroke engine.

YouTube - da power of flymo

YouTube - Flying Mower

 

[nealfris]

Thanks everyone for your input. I sure wish I could glean all the helpful info in to formulating a hydraulic design. I guess at this point it's honestly over my head. I just don't know enough about hydraulics, there are so many choices and mistakes are too costly.
I refuse to give up! I have yet to find anything similar to get earnest ideas off of. Some how I need to drill down on the variables. If I use a high rmp motor, which one? If I go with pto pump, what is the list of components to make that system, and still, which motor? Why is there no impact to the scenario if there is a belt and pulleys to change the rpm's?
The physical build exceeded all my expectations. It was an idea I'm sure everyone has thought about. I expected it to be too heavy to extend so I slapped it together expecting to fail. But its not too heavy at all.
As far as the danger of debris, I designed the adjustments so it never can aim horizontally at me. I also will put a rubber shield on the side facing me and of coarse wear proper fighting gear. :laughing:
Thanks to TBN there's a place to talk it out.

 

[aczlan]

As far as the danger of debris, I designed the adjustments so it never can aim horizontally at me. I also will put a rubber shield on the side facing me and of coarse wear proper fighting gear. :laughing:
Thanks to TBN there's a place to talk it out.

I would probably look into adding some guarding like this tractor has: http://tractor4hire.com/images/Boom Mower.jpg if you will be using this often. It would be a lot cheaper than an ER visit.

Aaron Z

 

[o2batsea]

I'd be interested in it's real world capability and how you use it. So I'm guessing that you'll be stationary when using it and just operating it from the seat? The pitch pivot ( the tractor's rear wheels) is pretty far away from the business end. Unless you are running on a dead flat track the mower will be hopping up and down madly when the tractor is moving. That's why they mount these things in the center of the tractor. Hope it works for you.

 

[J_J]

Thanks everyone for your input. I sure wish I could glean all the helpful info in to formulating a hydraulic design. I guess at this point it's honestly over my head. I just don't know enough about hydraulics, there are so many choices and mistakes are too costly.
I refuse to give up! I have yet to find anything similar to get earnest ideas off of. Some how I need to drill down on the variables. If I use a high rmp motor, which one? If I go with pto pump, what is the list of components to make that system, and still, which motor? Why is there no impact to the scenario if there is a belt and pulleys to change the rpm's?
The physical build exceeded all my expectations. It was an idea I'm sure everyone has thought about. I expected it to be too heavy to extend so I slapped it together expecting to fail. But its not too heavy at all.
As far as the danger of debris, I designed the adjustments so it never can aim horizontally at me. I also will put a rubber shield on the side facing me and of coarse wear proper fighting gear. :laughing:
Thanks to TBN there's a place to talk it out.

There is impact to the scenario by using belts and pulleys. If you increase the rpm of the blades, the torque goes down.

 

[nealfris]

JJ, If I were to use the 11.4 GPM PTO pump as you suggest, could you please tell me what you would recommend for a motor???

 

[J_J]

With 11.7 GPM's, a 3 cu in hyd motor will turn at around 900 rpm. I believe that is the size hyd motor that is used on the 48 brush cutter below. It runs on 8 GPM, at 3000 psi .

The PTO pump max pressure is 2200 psi.

The object is to get the blade tip speed up high and still have enough torque to do the work.

 

[nealfris]

JJ, this is the only one with RPM as high as you described. Would this do the trick?

Surplus Center - 3.15 cu in DYNAMIC BMPH50H2KP HYD MOTOR

 

[ns_in_tex]

We built something similar for our front end loader about 10 years ago. We don't like to run our engine full throttle, so we figured around 5 to 6 gpm on flow. I think this may have figured to around 5 HP on our 30" mower deck. We used a Barnes Hydraulic motor, purchased from WW Grainger, P# 4F657-3. We used belt drive, I think for 2 reasons. To get blade tip speed and we were afraid the motor bearings would not stand up to direct drive pressures. The mower deck already was set for belt drive & it was just easy to do this.

Of course, we always want more power, but it probably performs as well as a 5 or 6 HP gas engine mower would.

 

[J_J]

JJ, this is the only one with RPM as high as you described. Would this do the trick?

Surplus Center - 3.15 cu in DYNAMIC BMPH50H2KP HYD MOTOR

That would probably work, but it does have a case drain line that needs to go to a cooler or tank. Three hoses.

Continuous pressure is only 1840 psi. What is your tractor relief set at?

 

[Tenn_Blue]

Been following this post with interest. I have been considering a similar idea for my miniX. Its a small one (4k lbs), too small for the commercial exc. mowers I have seen (more money than I want to spend as well...).

The x has good aux. hydraulics, and the tracks let it go places the tractor can't (safely). The reach of the boom would be good to clear culverts and hill sides I do now with a weed eater. And would be great for clearing brambles and brush at the fields edge.

I'm considering using a (don't laugh...) push mower. Leave the bottom half of the engine case on the frame (roller bearings and crank shaft). Then use a pulley/belt and hydraulic motor mounted on an adapter plate screwed on the top of the engine case (roller bearing for the other side of crank as well). Cut off the skirt on 1/2 of the mower deck (the part away from you) and fab a 2 part blade like a bush hog.

But I'm trying to figure out the hydraulic needs and motor size before I go any further with the idea.

So let us know how you figure things out! I got this ratty old push mower just sitting here..... :laughing:

 

[boggen]

when i initially saw thread title. then saw the mower deck pictures. i was surprised it was not a sickle bar.

perhaps. i have just seen a few to many sickle bars with side mounted on a tractor to deal with ditch mowing.

anyhoots. my concern is with tubing size. if ya go to small say 1/2" vs going 3/4" or 1" size. you may end up with hyd oil over heating. and less power at the pump on the mower deck. i honestly haven't done friction loss for hydraulic hoses. but i would imagine over the length of hose you are talking about. going to small could cause you problems. go bigger hose and reduce at the ends.

as far as pump/motor sizing, i would expect to be able to call manufacture and get some sort of flow chart. for RPM to GPM for any given pump/motor over a range of RPMs. once i got a enough charts. i would overlay them all into a single chart. then if doing pullys / belt drive. were pully on blade is smaller than pully on the pump/motor. i would work out the difference and plot the blade tip speed on the one chart. to find the best pump to suit given needs. ((in regular water pumps for say sizing a pump for a pond or well)) this would be more known as creating a system curve and applying different pump curves to the system curve to find correct pump for the given setup.

 

[dfkrug]

To size hoses for continuous motor duty, you can use the equation
D = sqrt(Q/2.45V), when D is in inches, Q is the GPM flow rate, and
V is the fluid velocity in ft/s.

A max velocity for a pressure line is about 25 ft/s, but that's pushing it.
If you went to half of that and 7GPM, a half inch hose is fine, if not
absurdly long.

You can get PDF catalogs for commonly available motors. The designer
must find his operating conditions on a manufacturer table like the sample
I posted. This is a White RS motor, which is not the ideal one for this
task, but they are commonly available. RS motors are slow speed, so
getting the right final load speed would require a step-up belt/pulley.
Understanding the use is important, too. Will the load be at max pressure
intermittantly or for longer periods? I would try to use a motor that
made use of the max pressure available from the implement pump.

 

[boggen]

To size hoses for continuous motor duty, you can use the equation
D = sqrt(Q/2.45V), when D is in inches, Q is the GPM flow rate, and
V is the fluid velocity in ft/s.

i would assume this is inside diameter of hose?

if Q = 7 GPM
if V = 12 ft/s
D = 0.49 inches.

A max velocity for a pressure line is about 25 ft/s, but that's pushing it.
If you went to half of that and 7GPM, a half inch hose is fine, if not
absurdly long.

continuous duty, and i am going to assume once he tacts on clamps and extra hose to get around joints of the back hoe and then the extended arm. 30 to 40 feet of hose one direction. plus double that for return hose, for a total of 60 to 80 feet.

i would consider that a pretty good length. then again. i don't know hydraulic specs. just water specs for ponds and wells. and don't know how much friction loss or rather PSI loss that would occur. but i would assume a good amount of psi loss, perhaps i am in the wrong.

You can get PDF catalogs for commonly available motors. The designer
must find his operating conditions on a manufacturer table like the sample
I posted. This is a White RS motor, which is not the ideal one for this
task, but they are commonly available. RS motors are slow speed, so
getting the right final load speed would require a step-up belt/pulley.
Understanding the use is important, too. Will the load be at max pressure
intermittantly or for longer periods? I would try to use a motor that
made use of the max pressure available from the implement pump.

*scratches chin*

if the you know the GPM and PSI of the pump and a motor of like equal size. you should have approx equal. RPM's and torque at the motor. with exception of pressure loss form hoses and efficiency losses of motor and pump.

if you had a bigger hydrualic pump on tractor. that sent more GPM and had more PSI than motor can handle. then there would be a good chance of the motor over heating. due to spinning way to fast. or not able to handle the pressure.

if you had a smaller hydrualic pump on tractor, and a bigger motor, that could handle GPM and PSI. the motor will not spin as fast. BUT, you would not be over spinning the motor to a point of over heating. or cracking it due to much pressure. to deal with motor not spinning as fast. it would just require a bigger pully on motor and a smaller pully on the blades.

to me "dfkrug" you are stating for a motor = to or bigger than the pump on the tractor for both GPM and PSI. if so i would be in agreement.