Slower Speed Stump Grinder question

[woodlandfarms]

I am still playing with the idea of building my own Hydraulic stump grinder. 4K entry price seems pretty rich...

But, in looking at Hydrualic motors I am a bit stumped. From what I have read it looks like most grinders go at 800 RPM. I am looking at wheel motors as I feel they would be the strongest for this direct drive application, but they seem to be limited to 500 or 600 RPM.

Would additional teeth make up for less speed? Or do I need to just find a faster motor.

Carl

 

[Zinno87]

Woudn't is be more important to ensure that you have a sufficient tip speed? Of the grinders that you have looked at, do they all have the same diameter wheels?

 

[woodlandfarms]

Hmmm... That is a good question. I was going to slap a 24" Wheel (maybe bigger but I doubt it). I wanted to use it as a shallow trencher as well.

But, now you have thrown me. Gotta figure out this tip speed thing...

 

[J_J]

Hmmm... That is a good question. I was going to slap a 24" Wheel (maybe bigger but I doubt it). I wanted to use it as a shallow trencher as well.

But, now you have thrown me. Gotta figure out this tip speed thing...

Carl,

With your 18 GPM PTO , a 4.2 cu in hyd motor would turn 1000 rpm, and use 37 HP. However, if you used a straight shaft and ran double pulleys, you could get the rpm up by using the correct ratio on the pulley set up.

This motor is a 4.95 cu in

Burden Sales Surplus Center Item Detail

 

[dynasim]

J_J

The hp consumed depends on the pressure. Your number is likely correct for high press. systems, but not the normal pressure ones. I may be wrong.

Chris

 

[woodlandfarms]

Thanks JJ. I am trying to stay away from a pulley system. I do not have the skill set to make something work with pulleys.

dynasim. The tractor I own is much like a skidsteer. my system is rated at 18GPM at 3100 PSI...

 

[Stimw]

Have you found Burden Sales Surplus Center - Hydraulics, Engines, Electrical and More yet? (never heard of them called Burden before, I typed their web address and the site changed to this) Good supply of hydraulic items with good prices. Also baileynet.com (no www needed) has good prices and great service.

 

[Scotty370]

You know I've been looking at simular project, but I've opted to go PTO mechanical vs Hydro motor. I think Zinno has it correct with the tip speed aspect. For example: In my 540 PTO application with say a 1:1.47 speed-up at the gearbox, the cutter wheel axel would be turning at 794 rpms. with a 24" wheel, that equates to 4,986' per minute of tip speed. For extremes, a 8" wheel would only have 1,662' per minute of TS, while a 36" wheel would have a whopping 7,480 feet per minute of tip speed! For any size wheel you choose just multiply the diameter x's 3.14 x's the rpm's and divide x 12 for ft per min at the tip. Just remember The larger the wheel, the more teeth your going to need, and they don't come cheap. I'm starting out with a 22" wheel with 18 teeth. Keep us posted. ~Scotty

 

[woodlandfarms]

Scotty, thanks for the info. I am all hydraulic so I will not have the luxury of a PTO...

As for Burden, I have known of them for a while through JJ. Did not know about the Burden name, seems to have been a change in the past 6 months or so.. Knew them as Surplus Center.

Carl

 

[nostep]

Surplus Center is their web name. They've always been Burden Sales when you see the bill. Read their "about us" page. Very old business.

 

[Scotty370]

Carl- I only meant to pass on the 'math'!! The tip speed (I think) is critical. The units that I'm shadowing, seem to like about 5,000 feet per minute. With your 1000rpm Hydro unit a with a 20" wheel would be 5233' per minute. Right in the ball park!! ~S

 

[J_J]

Surplus Center is their web name. They've always been Burden Sales when you see the bill. Read their "about us" page. Very old business.

Hi Nostep, Is that a Magnatrac mini-dozer in your avatar? I have an M-1800 with a 16 hp motor. I am looking to sell mine.

 

[J_J]

Carl,

Are there any stump grinder dealers in your area? If so, you might be able to purchase the hydraulic head unit from one of the units that will match your GPM and pressure, or find a used one. If you have to make it your self, you will have to do a bit of machining, and then you will have to set up the teeth at the correct angle, and spacing. Although a machine shop can do all this, they aren't cheap. There are a lot of different teeth out there.

You probably know that I have the PT stump grinder/trencher, but I am planning to mount it differently so it will cut/grind left to right. not back at me. I also have a tow behind small stump grinder that uses a Honda 13 HP engine to double belt drive the cutting fead which is about 12 in in diameter, with eight carbide teeth. Although it has fewer teeth, the head turns about 2000 RPM, and it does a credible job. The teeth are only a couple of dollars apiece.