B7800 RPM "sweet spot."
- Thread starter Muleskinner
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OP
Muleskinner
Gold Member
Bird
Rest in Peace
Rick Jay
Platinum Member
- Joined
- Apr 6, 2000
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- Tractor
- Kubota B2910, also Honda HT3813 with mower and front blade.
Re: B7800 RPM \"sweet spot.\"
Muleskinner,
O.K....I'll bite...I don't want you to feel abandoned. /forums/images/graemlins/grin.gif And I'm guilty of being one of the ones that viewed your first post without responding. /forums/images/graemlins/blush.gif
I've got a B2910, but it's the same drivetrain as the B7800.
For normal grading and loader use, I usually have the throttle between 1200 and 1500 rpm, depending upon what I'm doing.
However, for PTO operated implements, I usually run at about 1500 rpm for my PTO pump equipped backhoe. The PTO snowblower pretty much needs full PTO speed, so I think that's around 2600 rpm. And for my posthole digger, I usually use about 1000-1100...just over idle. It's easier to control if it's not spinning too fast. I don't have any experience on the roto-tiller, but my guess is that will need full PTO rpm like the snowblower.
I hope this helps.
~Rick
Muleskinner,
O.K....I'll bite...I don't want you to feel abandoned. /forums/images/graemlins/grin.gif And I'm guilty of being one of the ones that viewed your first post without responding. /forums/images/graemlins/blush.gif
I've got a B2910, but it's the same drivetrain as the B7800.
For normal grading and loader use, I usually have the throttle between 1200 and 1500 rpm, depending upon what I'm doing.
However, for PTO operated implements, I usually run at about 1500 rpm for my PTO pump equipped backhoe. The PTO snowblower pretty much needs full PTO speed, so I think that's around 2600 rpm. And for my posthole digger, I usually use about 1000-1100...just over idle. It's easier to control if it's not spinning too fast. I don't have any experience on the roto-tiller, but my guess is that will need full PTO rpm like the snowblower.
I hope this helps.
~Rick
fishman
Veteran Member
Re: B7800 RPM \"sweet spot.\"
I'm with Bird on this one. I've got a 2910 which has the same engine as the 7800 and I find that 2200 rpm seems to be about right when performing loader tasks. I occasionally run my loader as low as 1900 rpm, but that is usually when I don't care if the speed and power are somewhat lessened.
Now for box blading I might run it at anything from 1500 to 2200, depending on the terrain and how big a bite I've taken.
2200 just seems to be optimal for getting most of the power and speed of the tractor with quite a bit less engine noise.
I'm with Bird on this one. I've got a 2910 which has the same engine as the 7800 and I find that 2200 rpm seems to be about right when performing loader tasks. I occasionally run my loader as low as 1900 rpm, but that is usually when I don't care if the speed and power are somewhat lessened.
Now for box blading I might run it at anything from 1500 to 2200, depending on the terrain and how big a bite I've taken.
2200 just seems to be optimal for getting most of the power and speed of the tractor with quite a bit less engine noise.
OP
Muleskinner
Gold Member
Re: B7800 RPM \"sweet spot.\"
That's about what RPM I felt works good and developes good torque. I began at 1500 RPM while breaking the engine in, but found that RPM lacked the torque to do any heavy FEL or box blade work. Thanks for the replies.
That's about what RPM I felt works good and developes good torque. I began at 1500 RPM while breaking the engine in, but found that RPM lacked the torque to do any heavy FEL or box blade work. Thanks for the replies.
Re: B7800 RPM \"sweet spot.\"
</font><font color="blue" class="small">( If you have the shop manual it should have a graph with the torque and horse power plotted, where the plotted line for the hp and the torque cross is the rpm you are looking for. )</font>
There's only one place where these can cross, and it's the same for all engines--5252.1 rpm (actually 33,000 divided by two pi). I doubt you could, or would want to, run the Kubota that fast. It has to do with the fact that horsepower is a number calculated by multiplying torque by rpm, then dividing by a constant (5252.1). From that formula, you can see that torque equals horsepower at 5252.1--always.
</font><font color="blue" class="small">( If you have the shop manual it should have a graph with the torque and horse power plotted, where the plotted line for the hp and the torque cross is the rpm you are looking for. )</font>
There's only one place where these can cross, and it's the same for all engines--5252.1 rpm (actually 33,000 divided by two pi). I doubt you could, or would want to, run the Kubota that fast. It has to do with the fact that horsepower is a number calculated by multiplying torque by rpm, then dividing by a constant (5252.1). From that formula, you can see that torque equals horsepower at 5252.1--always.