Building Custom Flail Mower

[lectro88]

Hello all.
I've been poking around this forum and decided to join.

I need a little help selecting a hydraulic motor.
My excavator is 27.8 kw hp. aux hyd 15.6 gpm @3000 psi.
What motor will give me max torque with undue stress on the pump and machine ?

Additional info about pump
pump type 2piston/2gear
hyd flow gpm. 9.9 x 2/5.8 x 1/2.7 x 1
aux flow gpm. 15.6

 

[J_J]

If your system has 3000 psi pressure, then a 20 CU IN motor, 3000psi, will produce 9.554 in lbs torque. Something like this , but it has spline shaft. Will turn 180 rpm.

https://www.surpluscenter.com/item.asp?item=ME211407AAFG&catname=hydraulic

Tapered shaft wheel motor, less displacement, less torque

https://www.surpluscenter.com/item.asp?item=9-7741&catname=hydraulic

 

[lectro88]

Thank you JJ.
The 1st link shows a roller vane pump, Is this vane similar to that found in say chevy transmissions and keroscene space reddy heaters, only a lot bigger? with what I would call large needle rollers.
in the research I've done a gear pump is used. pros/cons ?
Also manufactured flail unit drums turn about 1800 rpm. I kinda wanted to couple the drum and pump with duel 5/8" belts for, hopefully a "little" cushion and I could adjust speed/torque if need be.

JJ can you tell me a little more about your torqe figure, you said the linked pump would produce 9.554 in lbs torque (was that just a typo error , . )
I think the spec. on the motor reads 8533 in lbs torqe is that roughly 711 ft lbs.
And if so, how well do you think it will drive the drum ?

 

[J_J]

The 9,554 in lbs was for a 20 cu displacement hyd motor, using a pressure of 3000 psi. That was to get you in the ball park with a motor that could use the 3000 psi, and give a high torque.

If you use the figures for a particular motor, the in lbs will be different. There is also the efficiency of the pump to motor of about 85 %. Whatever the rpm of the motor you choose, you will have to work out a sprocket or belt pulley ratio to get you to the drum rpm.

The torque of a drive train with all the loads and inefficiencies will have to be considered. That goes above my basic math. There are probably some engineering types on here that might step in and give a practical solution. All of the above was to help get you started.

Do you have any idea of the weight of the drum with teeth that you are thinking about?

It just might have to do with HP to weight ratio.

 

[lectro88]

JJ.
I really appreciate your helping with this right off. Alot of times people will shun a new member.

The drum I'm thinking of down sizing in length to gain some recovery from stalls if you think its worth while. I'm open to suggestions, I was thinking of running duel 5/8" pulleys and maybe putting a magnetic clutch or transmission sprag to releive sudden stops as you well know it happens, especially on unknown property, or forgotten areas.

Ok. The drum, what I had in mind was 6-8" dia x 1/4" thick min pipe x 20"-30" long. Cutters was thinking 3"-4" angle x 3/8"-1/2" 10-14 cutters 1" x 3" long grade 8 boltsw/nuts, maybe 2 nuts each, welded pipe insert on on each angle to aid in true swing and prevent twist factor of cutters(does that make sense)not just a hole drilled in the angle and passing a bolt through it.(swing yes. twist no) so 12"-14" drum OD. And guessing 50-100 lbs. Thats a big variable, but I think its close figuring a total through shaft of 1"- 1-1/4" solid.
Of course weigh and grind each to match 1 another.

How am I doing so far ?
Think it will work ?

 

[J_J]

One of the most important things is balance. You might not have a way to balance all the metal you will be welding to the drum. I think I would go to the web site, Flail Masters, and check out their drums. A finish flail will have many more cutters than a rough cut hammer flail.

Flail-Master - Mower Replacement Parts, Commercial Riding Mower Parts, Rotary Cutter Parts, Blade grinders, Trimmer Line, Mowing Accessories - Flail Master - Flailmaster -

 

[lectro88]

JJ
Is it ok to PM you ?

 

[J_J]

Yes sir.

 

[ptexer]

I saw you were using grade 8 bolts. I am not sure of this whole design. I have run machines for a long time and appreciate when a soft bolt brakes and prevents damage to expensive parts. I just offer this for consideration and I am not saying your plan is flawed.