What RPM to rub BH92?

[MOlivin]

Hi all,

Just got the BH92 all mounted and plumbed on our L6060... through the directions there is no info on what the optimal RPM should be to run it.

Any advise?
We'll be using a 16" trench bucket digging into some extremely rocky ground.

Thanks all!

 

[pokey1416]

You'll get all kinds of answers, start slow until you get the hang of it. I think the manual "recommends" at least 75%. I usually run mine at WOT as it helps keep the DPF clean and makes up for all the low RPM puttering I do.

 

[MOlivin]

You'll get all kinds of answers, start slow until you get the hang of it. I think the manual "recommends" at least 75%. I usually run mine at WOT as it helps keep the DPF clean and makes up for all the low RPM puttering I do.

Isn't running at WOT incredibly hard on the tractor? Even running our MX6 brush hog I only run the PTO at 380.

 

[hagrid]

Isn't running at WOT incredibly hard on the tractor?

@lugbolt

 

[pokey1416]

Isn't running at WOT incredibly hard on the tractor? Even running our MX6 brush hog I only run the PTO at 380.

Lugbolt is one of our local experienced Kubota mechanics and knows a whole bunch more than me. He's helped countless people here, kind of like one of our "grandmasters". Hopefully he'll respond.

The short answer is "no" it won't hurt it and you'll watch your DPF % decrease at the same time.

 

[nbryan]

I run my BH77 on B2650 at the tractor's "rated RPM" as advertised, which is 2500rpm and mid-pto 2500rpm for the blower.
2398rpm is the rpm that produces 540 rear PTO rpm
The "working" rpm is not WOT. WOT runs my machine past 2700rpm which is not ideal for the engine on the HP/Torque output curve, and likely uses more fuel for the same work.
So I run at suggested recommended or rated rpm.

 

[TheOldHokie]

Isn't running at WOT incredibly hard on the tractor? Even running our MX6 brush hog I only run the PTO at 380.

NO. Plus you are doing the mower and tractor a disservice running the PTO at 380.

Dan

 

[lugbolt]

Kubota designs the engines to run at rated RPM, which is close to maximum.

Mowing specifically, they want it at close to maximum rpm on most tractors. On the BX's and G/GR series diesels, wide open while mowing, nothing less. The faster you run it the faster the engine cooling fan and water pump run, which aids in cooling. Plus the blade tip speed is "on up there" which gives you a better cut. It's more efficient overall to run at rated rpm.

with backhoe use the faster you run the rpm the faster the backhoe works. Not that you "have" to run at max speed, but if you do it works faster. Maybe a little jerky for some peoples' preferences. If that fits you, slow it down a little.

someone's gonna say "excavators run at 1800-2200". Yep a lot of them do. Difference is, excavators use a completely different hydraulic system, most Kubota tractors run a fixed displacement pump which runs off of the engine, so the faster you run the engine the faster and usually more powerful your hydraulic functions are. Excavators/skid steers use a variable displacement pump(s) which mostly vary the output based on user demand rather than engine speed.

 

[Runs With Scissors]

Maybe a little jerky for some peoples' preferences. If that fits you, slow it down a little.

I find that running my 77 at about 1900 rpm is my sweet spot between "jerky'ness" and speed/power.

I'll adjust as needed, (but I need longer arms.)

Edit: I Almost forgot to congratulate the OP on his new "best buddy".....I love my hoe!

 

[fried1765]

Kubota designs the engines to run at rated RPM, which is close to maximum.

Mowing specifically, they want it at close to maximum rpm on most tractors. On the BX's and G/GR series diesels, wide open while mowing, nothing less. The faster you run it the faster the engine cooling fan and water pump run, which aids in cooling. Plus the blade tip speed is "on up there" which gives you a better cut. It's more efficient overall to run at rated rpm.

with backhoe use the faster you run the rpm the faster the backhoe works. Not that you "have" to run at max speed, but if you do it works faster. Maybe a little jerky for some peoples' preferences. If that fits you, slow it down a little.

someone's gonna say "excavators run at 1800-2200". Yep a lot of them do. Difference is, excavators use a completely different hydraulic system, most Kubota tractors run a fixed displacement pump which runs off of the engine, so the faster you run the engine the faster and usually more powerful your hydraulic functions are. Excavators/skid steers use a variable displacement pump(s) which mostly vary the output based on user demand rather than engine speed.

I NEVER run my 2006 L48 TLB (3 hyd. pumps) at more than 2000 RPM,..... and often less!
By the way: What's this "DPF" thingy..... that so many folks seem to be focused on?

 

[MOlivin]

Got it, thanks all for the help, it's greatly appreciated!

Takeaway notes for future readers:
-Run MX6 cutter at at rated pto rpm... 540 @ pto per JD.
-Run BH92 backhoe as fast as possible, barring the jerkiness. As my ground is mostly rock, I'm sure I'll need all the power I can get to break through.


On a side note, the only drawback I've found with the BH92 is the lack of trencher buckets, more specifically either a 4.5" or 6" wide. It came with a 16" trencher and a mechanical arm... I have a lot of wire and 4" pipe to run so digging 16" wide or even 12" wide with the smallest bucket they make is way over kill.
Any suggestions on this is appreciated too.
Thanks again all!

 

[fried1765]

Got it, thanks all for the help, it's greatly appreciated!

Takeaway notes for future readers:
-Run MX6 cutter at at rated pto rpm... 540 @ pto per JD.
-Run BH92 backhoe as fast as possible, barring the jerkiness. As my ground is mostly rock, I'm sure I'll need all the power I can get to break through.


On a side note, the only drawback I've found with the BH92 is the lack of trencher buckets, more specifically either a 4.5" or 6" wide. It came with a 16" trencher and a mechanical arm... I have a lot of wire and 4" pipe to run so digging 16" wide or even 12" wide with the smallest bucket they make is way over kill.
Any suggestions on this is appreciated too.
Thanks again all!

If you have any amount of clay content in the soil you dig, you will quickly learn to hate any sort of narrow bucket.
A 4.5"- 6" bucket will be plugged all the time.

I considered a 12" (quick attach) trenching bucket for my BT1100, but did not get it, because my thumb is 14" wide, and I did not want my thumb to define the trench width.

I bought a 16" (Kubota - Werk Brau - quite spendy) trenching bucket, works fine, and even though I have no clay content, it sometimes will not empty completely.

If you are really stuck on this narrow bucket thing, you might contact the Rhinox Group at 1-267-861-0812.
They make VERY narrow trenching buckets!
They are a Great Britain Mfg. with offices/sales facilities in Texas, and have excellent reviews.
Their website will show you some photos.
sales@rhinox-group.us

If you have lots of rocks, you might also consider a root ripper to first rip the ground up.
I recently bought a 28" root ripper (only 1" wide) from Ox Thumbs, in Carrollton, GA.
What a neat tool.
Puts the entire BH force on any 1" wide spot/rock/etc.
I have the Kubota BH "quick connect" system so changing BH buckets/attachments is very easy for me.

YMMV........