Flail Mower Let's talk flail mowers

[dlmpsy]

Thanks for the recommendations. I've been thinking about the Caroni since last summer. It's about income tax time, so I'm getting ready to bite the bullet.

 

[Waratah15]

Hello All,

I originally posted this in the Build It section but think it may be more appropriate here.

Planning to build a flail mower for my ASV Skid Steer, realise you are PTO kinda guys...if it's any consolation I do have a Kubota BX1800. But reading through the forums there is an absolute wealth of knowledge here and I was hoping you may be able to help me out.

Just after some advise before I get into the 3D drawings stage, I'll be drawing it all up in Solidworks and would be more than happy to share laser cutting files etc once I get to that stage.

Plan to run a hydraulic motor something like this one
Surplus Center - 2.8 cu in CHAR-LYNN 101-1001 HYD MOTOR

This style of motor runs at about 1000rpm

I have 16.3 gpm and a 3000 psi relief pressure on my hydraulics to run the mower

Seems like flail blades need to run at around 8500 fpm, I'm guessing that the overall diameter of the main shaft and blades - cutting tip to cutting tip is about 12 inches. That means that if I run the shaft at 1:1 with the motor (via belts) @ 1000 rpm I will only be getting 1' x 3.14 x 1000 rpm = 3,140 fpm.

So my options seem to be, either 3:1 with the belts or combination of inline gearbox and upping the ratio with the belts. of course I could always increase the diameter of the cutters tip to tip but don't want to make the whole thing too massive considering its a low flow skid steer.

Maybe I need to run a motor like this, with 5000 rpm (scary!) and gear it down with the belts.

Surplus Center - About Us

Any suggestions here please?

Next question - the main shaft that the flail blades are attached too, are they solid steel? Maybe 3 or 4" diameter with the ends turned down for the bearings. That's one heavy shaft at 72 inches, couple of hundred pounds right there. I realise this assembly will need to be dynamically balanced.

Hoping I'm not wearing out my welcome here, regarding the hydraulics, if someone with some experience here could chime in I'd really appreciate it. My ASV has controls in the cabin for forward and reverse but I'm looking at what I will need on the mower deck for the circuit. Seems like I need a pressure relief valve to keep the psi in the acceptable range for the motor, is there anything else that I should be putting into this circuit in terms of flow control or cushion valves?

Some of the lower end skid steer flail mowers lack the ability to 'float' in relation to the skid steer. The Bobcat one looks really nice and seems (although I'm not exactly sure) to have a mechanism that lets it articulate up and down as well being able to rock one side higher than the other. At the very least I'd make it free in the up and down plane to follow contours more effectively.

Any thoughts/opinions/advice gladly received, thanks, Jonathan

 

[GinNB]

Why such a small diameter cuttershaft? 12" tip to tip for the blades is pretty small. The increased RPM required would probably be harder on bearings, assuming that you could keep such a small cuttershaft stiff and straight. Larger diameter tubing is much stiffer than smaller diameter or rod. I'd check a materials manual to see the amount of force required for much deflection in the center of the shaft. What happens if it hits a rock in the middle? Lose a pair of teeth and going around how many thousand times before you can stop it? Rigidity in the center of the shaft is good. Overkill is the best. I'd use a bit larger tubing to help with the needed tip speed.

Haven't checked recently, but off the top of my head I think I remember the tip speed on an Alamo SHD is in the 3500+fpm range. 3800 maybe? I was told that at a dealer ages ago but couldn't find it in print when I looked. If they were right and my memory is good, you aren't that far off.

 

[Waratah15]

Thanks GinNB, only picked 1' out of the air, trying to work out the scale of the machines I've seen on-line. Starting with clean sheet so I can do it any size I want. I got the 8 or 9000 fpm figure from the Bobcat site but I haven't been able to work out how most of the mowers powered by a 580 rpm PTO could get anywhere near that so what you are suggesting makes sense. Don't want to run anything anywhere near 5000 rpm on equipment like this.

If anyone could measure or roughly know the size of the centre shaft and the total tip to tip diameter that would be a great help.

 

[IslandTractor]

Thanks GinNB, only picked 1' out of the air, trying to work out the scale of the machines I've seen on-line. Starting with clean sheet so I can do it any size I want. I got the 8 or 9000 fpm figure from the Bobcat site but I haven't been able to work out how most of the mowers powered by a 580 rpm PTO could get anywhere near that so what you are suggesting makes sense. Don't want to run anything anywhere near 5000 rpm on equipment like this.

If anyone could measure or roughly know the size of the centre shaft and the total tip to tip diameter that would be a great help.

Do you have the capability of dynamic testing and balancing of the rotor? That is the most critical part of the fabrication as the rest is really just a PTO or hydraulic power transfer device. If you don't, perhaps it would make sense to bite the bullet and purchase a rotor from Alamo or Caroni or one of the other companies that make these mowers. You might find it cheaper in the long run to purchase a PTO flail and convert it. Depending on what duty machine you want, that might be the cheapest and fastest way to do it.

 

[Code54]

My center shaft is 9" in diameter (think the book said 3/8 wall thickness) not including the shackle or knives. It is a Bomford/Turner commercial model. The overall weight is 1258 if I remember correctly.
Hope that helps

 

[Waratah15]

Do you have the capability of dynamic testing and balancing of the rotor? That is the most critical part of the fabrication as the rest is really just a PTO or hydraulic power transfer device. If you don't, perhaps it would make sense to bite the bullet and purchase a rotor from Alamo or Caroni or one of the other companies that make these mowers. You might find it cheaper in the long run to purchase a PTO flail and convert it. Depending on what duty machine you want, that might be the cheapest and fastest way to do it.

I'll certainly have the shaft and blades balanced after construction, it's possible to buy flail mowers in Australia with the bobcat attachment but they are insanely expensive. The other option is to buy an second hand pto unit and convert that. Just love designing and making things! It's a disease I have and there doesn't seem to be a cure!

 

[Waratah15]

My center shaft is 9" in diameter (think the book said 3/8 wall thickness) not including the shackle or knives. It is a Bomford/Turner commercial model. The overall weight is 1258 if I remember correctly.
Hope that helps

Thanks Code54, that may be a little too big for my hydraulics but sounds much better than the 3" solid I was thinking of.

 

[Waratah15]

Just sourced some 6 1/4" OD 3/8" wall cold drawn seamless hydraulic cylinder tube - $300 for 72"

Can't quite work out why these units are $10,000 dollars here! I know these are excavator mount units but there are some big margins as far as I can work out.

Excavator Brush Mowers

 

[leonz]

Hello Warata,

Before you get too too far on this-

You should vistit the everything attachment site or the skid steer attachments.com and you can purchase a quick attach kit that can operate a standard PTO drive three point hitch type heavy duty flail mower with your ASV hudraulic system using a pump mounted in the quick hitch that rotates the flail mower gearbox at the rated 540 RPM using the ASV hydraulic system.

I have one question is your ASV unit a high flow unit?


Save your time and money and do it this way.:thumbsup:

 

[Waratah15]

Hello Warata,

Before you get too too far on this-

You should vistit the everything attachment site or the skid steer attachments.com and you can purchase a quick attach kit that can operate a standard PTO drive three point hitch type heavy duty flail mower with your ASV hudraulic system using a pump mounted in the quick hitch that rotates the flail mower gearbox at the rated 540 RPM using the ASV hydraulic system.

I have one question is your ASV unit a high flow unit?


Save your time and money and do it this way.:thumbsup:

Thanks for the advice Leonz, only problem is that the 3 point adaptor low flow attachment in Australia from skid steer solutions is $3097, that before I buy a flail mower!

http://www.skidsteersolutions.com.au/Skid_Steer_LF_3_Point_Adaptors_s/53.

Pretty sure I can build the whole thing for way less than the cost of just the 3 point attachment, found a much better motor now from Surplus Centre, runs at 1800rpm @ 15.5 gpm. I'm lucky enough to have a very nice workshop, lathe, mill, mig, tig and some expertise with designing in 3d cad. Just have to make sure I really get the basics sorted in terms of speccing the components. Now I realize this isn't a simple project, have a good buddy that says everything you plan in terms of time and cost for a project should be multiplied by the magic number pi

Oh and by the way, my skid steer has low flow, 16 gpm.

Any advice on tip speed of cutters most welcome, seems like it's somewhere between 3000 and 9000 fps from what I've read and been told - thats a pretty broad target....

 

[leonz]

Thanks for the advice Leonz, only problem is that the 3 point adaptor low flow attachment in Australia from skid steer solutions is $3097, that before I buy a flail mower!

http://www.skidsteersolutions.com.au/Skid_Steer_LF_3_Point_Adaptors_s/53.

Pretty sure I can build the whole thing for way less than the cost of just the 3 point attachment, found a much better motor now from Surplus Centre, runs at 1800rpm @ 15.5 gpm. I'm lucky enough to have a very nice workshop, lathe, mill, mig, tig and some expertise with designing in 3d cad. Just have to make sure I really get the basics sorted in terms of speccing the components. Now I realize this isn't a simple project, have a good buddy that says everything you plan in terms of time and cost for a project should be multiplied by the magic number pi

Oh and by the way, my skid steer has low flow, 16 gpm.

Any advice on tip speed of cutters most welcome, seems like it's somewhere between 3000 and 9000 fps from what I've read and been told - thats a pretty broad target....

Hello Warata, save your money and buy the attachment with the integral pump!!!!!!!!!!!!!!!!!!!!! I can tell you that from experience of owing and operating flailmowers for 30 plus years that you cannot build one for less than they sell them for in OZ

The reason the flailmower units cost so much in OZ is the construction as many of them have carbide tipped or carbide tooling welded to the cutter drums which are very thick in actual construction.


You do not need a wide flailmower for your ASV Warata, Perhaps even a Vrisimo vineyard mower Cabe or a Caroni with a 2 row rotor would be well within your budget.

Talk to Iron Horse before you spend anymore time on this pursuit as he will be the best source of information on this as he is in Oz and uses flailmowers.







About the flail mower rotor and knive tip speed; the rotor diameter is going to govern the entire issue. The small steel tubes they are using for most all flail mowers now require a longer knive versus the drum type knive mounts which have a shorter knivve and allow for a slower knive speed.

Depending on the rotor size you may see tip speeds of 200 M.P.H.,strictly depending on the mower model and rotor type.




I am going to very very strongly suggest that you contact Iron Horse here Via a Private message as he has been mowing plenty of brush and jungle in OZ for quite a few years now and he will help you understand why its better to buy a good flailmower for the job.

You will be better off buying the attachment adapter tool carrier

 

[Waratah15]

Thanks for your advice Leonz, will certainly talk to Iron Horse. The crazy situation here is that an identical product sells for roughly twice what you guys pay for it. I actually imported my ASV privately from the US.

Not quite sure what you mean about the carbide cutter, I'm looking at a flail mower, not a mulcher with carbide tipped cutters.

As I mentioned earlier, the 61/2 tube 3/8 is probably reasonable but even going to 1/2 wall the actual tube in the length I would require would be well under $500. The knife clevis plates are simply laser cut and welded onto the shaft, then it's simply a matter of buying off the shelf knives.

I have experience with building and designing equipment as my profession and even at home built a mobile gantry crane spanning 16', tandem trailer for the ASV, hydraulic tube bender.

The satisfaction I get from working through all the issues is half the fun!

Appreciate your comments though, thanks again.

 

[GinNB]

3/8" should be plenty thick for your tubing thickness if you're using 3/16"-ish knives for grass and light brush. I've never had a mower apart that used hammer knives, and I know you're not building a stump grinder or forestry mulcher. I'm not sure what grades the tubing comes in but I wouldn't use regular pipe. The metal is too soft. Same goes for the clevis plates. 3/8" AR400 is what I'd recommend for the plates. Preferably cut with a water jet. Plasma takes the temper away from the edges of where it is cut. Not a huge deal for clevis plates, but if you've got a choice and the price is the same, go with the water jet. We redid one of our cutter shafts and had a local shop cut the clevis plates for us. Not sure who forgot to make sure that good steel was used, but they wore out fairly quickly. The ends bang up when they hit rocks and the clevis pins wear through and pull out through the plates after a while.

 

[Rip]

By the way Waratah, last time I checked Iron Horse has not been on TBN for several years now......just sort of dropped off the radar......hope he did not get snake bit as he was talking about in some of his last posts!

I have been contemplating a medium-duty 3pt flail for our new 4 acre property on N coast of Tassie, but probably a little ways off at this point. Does seem like the best all-around option.

Have fun and good luck with your project ! Cheers, Rip

 

[Waratah15]

OK I'm getting closer with specs for the flail mower I'm going to build.

Now the big question, Y knives or hammer type blades, from what I have read it seems that the Y knives may use a little less power and I only have about 20hp at the hydraulic motor. Of course it's easier to fabricate the shaft with fewer blades so that's also a plus for the hammer blades.

The other knife related question is layout on the shaft, seems that some have a spiral arrangement and some have opposing blades seemingly at right angles to each other or at 12, 3, 6, and 9 o'clock. If anyone could describe what they have I'd really appreciate it.

Some of the companies quote percentage overlap of blades and that can go as high as 45%, I'm much more concerned with brush and paddock cutting rather than finished lawn so my priority is efficient power use and a pretty robust setup rather than perfect finish.

Any wisdom gladly accepted, thanks all.

 

[GinNB]

How wide? 5hp/foot is adequate for a shaft and belt driven flail and moving the tractor around. Our triple gang 9' hydraulic flail manufacturer recommends a minimum of an 80 pto hp tractor to make it hum, so roughly 9hp/foot. 70hp makes for a bit of a pooch. Fluid drag sucks power and you want enough to travel at more than a crawl when doing more than a light trim.

 

[Waratah15]

How wide? 5hp/foot is adequate for a shaft and belt driven flail and moving the tractor around. Our triple gang 9' hydraulic flail manufacturer recommends a minimum of an 80 pto hp tractor to make it hum, so roughly 9hp/foot. 70hp makes for a bit of a pooch. Fluid drag sucks power and you want enough to travel at more than a crawl when doing more than a light trim.

Thinking 5 feet wide, the width of the skid steer. The skid steer is an ASV RC-60 and I have 16.3 gpm flow and 3000psi pressure for accessories, I got the 20hp from the specs of the motor I'm planning to use:

Surplus Center - 1.80 cu in CROSS HYD MOTOR 40MH18DACSC

And that 20hp is at 1800 rpm so I think thats pretty conservative because max rpm of the motor is much higher, I'll keep looking for a motor that maxes out more at my gpm max. So that 20hp is output from motor not skid steer motor total power.

I realise it won't set the world on fire but should be fine, thats why I'm trying to get the most efficiency out of the knives. Could go 4 foot cutter and offset it I guess, that would give me a lot more grunt for tougher brush but would much rather cut the whole width if possible.

 

[Rip]

Waratah, I know you are keen on building your own, but was wondering if you have seen the Hanmey Implements (dot com.au) line of (mostly Chinese) implements which includes several flail mowers that look identical to the ones sold in the States by various outfits?

Not sure if they have skidsteer-type (most are 3 pt), but they may be willing to sell one without the PTO drive & gearbox and mounts such that you could add hydraulic motor and custom mounts for less than starting from scratch. Looks like they have some mid-season price reductions going on also.

Just a thought. Good Luck Cheers, Rip in Tassie

 

[GinNB]

If the skidsteer creeps along, I wouldn't worry about width quite as much as being able to cut a complete path. 5'6 even. I'm not a hydraulics engineer, so my next move would be to call my dealer and ask what's the biggest, nastiest hydraulic motor they would put on it, and then find one with those specs rather than limit myself to what I could find quick, cheap, and easy. The strongest motor possible would repay you in increased travel speed and reliability.