Slower Speed Stump Grinder question

woodlandfarms · Jan 3, 2009

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 · Jan 3, 2009

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 · Jan 3, 2009

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 · Jan 3, 2009

woodlandfarms said:
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 · Jan 3, 2009

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 · Jan 3, 2009

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 · Jan 3, 2009

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 · Jan 3, 2009

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 · Jan 3, 2009

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