Backhoe slow bucket response
- Thread starter magyarbacsi
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Super Member
Shift....I found the speed up for the bucket dump! No...don't get excited. It goes from dead slow to just slow. I watched a Cat 960G pay loader the other day dump its bucket. Ours is as fast as that.
bindian
Super Member
When dumping my 511 BH bucket, I extend the dipperstick at the same time. Just timing the bucket.... ....will "seem" slow.
hugs, Brandi
hugs, Brandi
Shift4200
Gold Member
Ugh, not the news i was hoping for. Sadly I had a similar experience when playing with a "friend of a friend's" Massey last weekend. It's a ~30hp tractor and in all honesty, i think ours dumps a little faster. The only thing I preferred on the Massy is the loader control handle being progressive in speed vs our "progress to regress to progress" type setup.
Take that loosely, I really only had 5 min or so to mess with it. This was the first time I met the guy, and within minutes of our first handshake i was asking to try out his loader.....
-J
oldnslo
Super Member
Slow speed on a single function is not an oil problem. Sounds like either a restriction in the line from the factory or the cylinder and geometry is such that full speed is still slow. Has anyone timed the cylinder travel speed in inches per second and then back figured what the flow rate of oil is in GPM to see if it matches the pump out put flow?
formula is: Q = VA
Q= = flow rate in GPM
V = cylinder velocity in IPS (inches per second)
A = cylinder area in square inches
example: 2 1/2 bore cylinder extends at a rate of 4 IPS
2 1/2 bore = 4.9 square inch area X 4 IPS = 19.6 cubic inches per second of oil flow
19.6 divided by 3.85 = 5.09 GPM
3.85 constant is derived from 231 cubic inches per gallon divided by 60 second in a minute
formula is: Q = VA
Q= = flow rate in GPM
V = cylinder velocity in IPS (inches per second)
A = cylinder area in square inches
example: 2 1/2 bore cylinder extends at a rate of 4 IPS
2 1/2 bore = 4.9 square inch area X 4 IPS = 19.6 cubic inches per second of oil flow
19.6 divided by 3.85 = 5.09 GPM
3.85 constant is derived from 231 cubic inches per gallon divided by 60 second in a minute
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Super Member
I'm willing to bet ...no. Basically, I for one have little idea about what you are talking about. I acquire the gpm which is 7.8 @ 2600 rpm's. The bore is 1" and extends to 4" in one second so its .78x4" = 4 cu ins oil flow. Now if I read you correctly that 3.85 is a "constant" and divide that into 3.12, I get a little bit over ".8". Something seems not right here if pump flow is 7.8? What'd I do wrong? In the manual, lock to lock dump speed is 2.6 seconds. Mine is closer to 7 seconds.
Last edited:
oldnslo
Super Member
Arrow,
your math is correct.
If you are talking about dumping a back hoe bucket you would have to use the differential area of the cylinder for figuring flow since the cylinder retracts to dump. Differential area is the rod area subtracted from the cylinder bore area.
On a loader bucket typically extending dumps the bucket so you would then use the cylinder bore area and if their are two cylinders you would then have to double the area to get an accurate flow rate.
Dumb question but.. With the back hoe raised off the ground and the bucket curled fully (like lifting a scoop full of dirt) and the engine off. If you move the control valve to dump the bucket does it drop slowly?
your math is correct.
If you are talking about dumping a back hoe bucket you would have to use the differential area of the cylinder for figuring flow since the cylinder retracts to dump. Differential area is the rod area subtracted from the cylinder bore area.
On a loader bucket typically extending dumps the bucket so you would then use the cylinder bore area and if their are two cylinders you would then have to double the area to get an accurate flow rate.
Dumb question but.. With the back hoe raised off the ground and the bucket curled fully (like lifting a scoop full of dirt) and the engine off. If you move the control valve to dump the bucket does it drop slowly?
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Super Member
No back hoe but yes, it dumps rather slowly.
J_J
Super Star Member
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- Sep 6, 2003
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- JACKSONVILLE, FL
- Tractor
- Power-Trac 1445, KUBOTA B-9200HST
Are you running the engine at max?
You only have max flow at max rpm.
In order to do a cyl speed test, it has to be a goood cyl with no leaks.
Are you using regen if it has regen?
Check your fitting and make sure there are no restrictor fittings in the flow path. Restrictor fittings will limit the GPM, and hence your flow.
Have a hyd shop put a flow meter in the line and see what the flow is.
You can do a flow test yourself by removing the bucket hose and put in a 5 gal bucket. Then use the lever to put hyd fluid in the bucket.
If you can fill to the one gal mark in 6 sec, then you have a 10 GPM flow.
A good cyl will have a speed factor, but the mechanical hookup will also
play a part by the distance of the bucket pins to the cyl connecting point.
The closer the cyl connection to the pivot point, the faster the dump.
You only have max flow at max rpm.
In order to do a cyl speed test, it has to be a goood cyl with no leaks.
Are you using regen if it has regen?
Check your fitting and make sure there are no restrictor fittings in the flow path. Restrictor fittings will limit the GPM, and hence your flow.
Have a hyd shop put a flow meter in the line and see what the flow is.
You can do a flow test yourself by removing the bucket hose and put in a 5 gal bucket. Then use the lever to put hyd fluid in the bucket.
If you can fill to the one gal mark in 6 sec, then you have a 10 GPM flow.
A good cyl will have a speed factor, but the mechanical hookup will also
play a part by the distance of the bucket pins to the cyl connecting point.
The closer the cyl connection to the pivot point, the faster the dump.
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Super Member
I did measure at the 2600 rpm rev point calculated for the pump of 7.8 gpm. I think it is slow because the desire of curl capacity from the factory out shone speed. The hoses look inordinately small (narrow) from others I've seen. I do not see how Mahindra advertises a 2.6 second dump time as it is no where near that.
