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  #11   IP: 94.196.232.75
Old 18-03-2018, 06:02 PM
doobin doobin is offline
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Default Re: Gear pump v piston pump

I though all minis bar the most basic are piston pumps now? Certainly seemed to be the case when I was looking.
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  #12   IP: 86.153.6.246
Old 19-03-2018, 07:08 AM
pond digger pond digger is offline
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Default Re: Gear pump v piston pump

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Originally Posted by doobin View Post
I though all minis bar the most basic are piston pumps now? Certainly seemed to be the case when I was looking.
On the Volvo 1.7D there is the option (according to the spec sheet).
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  #13   IP: 95.147.232.252
Old 25-05-2018, 11:46 AM
Old Operator Old Operator is offline
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Default Re: Gear pump v piston pump

In theory axial piston pumps added to a machine should reduce engine HP by about 20% (as against gear pumps) on an otherwise identical sized machine.
Reason is I am told, is that with a gear pump the engine needs to be able to sustain peak flow at max pressure, while with an axial it can develop max flow at lower pressures while swashing back to a lower flow rate when max pressure is needed (e.g. prying out a tree root)

That said an axial needs a higher spec hyd fluid with more additives. It is also said that a machine can wear out 3 sets of gear pumps in its life BUT when axials break up they send small particles around the system that score up other hyd components giving the machine a much shorter life, - Source here
http://www.vannattabros.com/iron1.html

Another thing to bear in mind is if a machine is on self drive hire - will the hirer top up the fluid with the correct spec oil. Also if you hire in any attachments - breaker, jack hammer etc, then they may be full of a lower spec oil that the last machine was running off. Gear pumps are pretty bomb proof & relatively cheap to replace, often generic parts can be supplied cheaper (Flowfit, Interpart). If doing your own servicing long term the gear pumps are simpler to diagnose faults etc.
I went through all this when comparing the 8018 vs 8020 & came to the conclusion that the difference did not justify the extra cost (on paper at least) - probably not so on bigger machines. If you do go axial by no means agree to biodegradable hyd fluid, as these pumps have a much shorter life on it.
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  #14   IP: 109.146.120.232
Old 25-05-2018, 07:33 PM
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V8Druid V8Druid is offline
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Default Re: Gear pump v piston pump

Quote:
Originally Posted by Old Operator View Post
In theory axial piston pumps added to a machine should reduce engine HP by about 20% (as against gear pumps) on an otherwise identical sized machine.
Reason is I am told, is that with a gear pump the engine needs to be able to sustain peak flow at max pressure, while with an axial it can develop max flow at lower pressures while swashing back to a lower flow rate when max pressure is needed (e.g. prying out a tree root)

That said an axial needs a higher spec hyd fluid with more additives. It is also said that a machine can wear out 3 sets of gear pumps in its life BUT when axials break up they send small particles around the system that score up other hyd components giving the machine a much shorter life, - Source here
http://www.vannattabros.com/iron1.html

Another thing to bear in mind is if a machine is on self drive hire - will the hirer top up the fluid with the correct spec oil. Also if you hire in any attachments - breaker, jack hammer etc, then they may be full of a lower spec oil that the last machine was running off. Gear pumps are pretty bomb proof & relatively cheap to replace, often generic parts can be supplied cheaper (Flowfit, Interpart). If doing your own servicing long term the gear pumps are simpler to diagnose faults etc.
I went through all this when comparing the 8018 vs 8020 & came to the conclusion that the difference did not justify the extra cost (on paper at least) - probably not so on bigger machines. If you do go axial by no means agree to biodegradable hyd fluid, as these pumps have a much shorter life on it.
where do you get this from Old Op.?? The Drema has run Fuchs' Plantohyd 40N all its life ... 5,500hrs give or take a few, currently
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  #15   IP: 86.178.87.17
Old 25-05-2018, 10:37 PM
bri963 bri963 is offline
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Default Re: Gear pump v piston pump

There aren't many machines where you get a choice, it's what the manufacturer uses. Where do you think the particles from a worn out gear pump are going? Piston pumps definitely have better characteristics, such as load sensing, running cooler due to not pumping constantly and better efficiency.
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  #16   IP: 165.120.92.55
Old 26-05-2018, 10:34 PM
pond digger pond digger is offline
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Default Re: Gear pump v piston pump

Quote:
Originally Posted by Old Operator View Post
In theory axial piston pumps added to a machine should reduce engine HP by about 20% (as against gear pumps) on an otherwise identical sized machine.
Reason is I am told, is that with a gear pump the engine needs to be able to sustain peak flow at max pressure, while with an axial it can develop max flow at lower pressures while swashing back to a lower flow rate when max pressure is needed (e.g. prying out a tree root)

That said an axial needs a higher spec hyd fluid with more additives. It is also said that a machine can wear out 3 sets of gear pumps in its life BUT when axials break up they send small particles around the system that score up other hyd components giving the machine a much shorter life, - Source here
http://www.vannattabros.com/iron1.html

Another thing to bear in mind is if a machine is on self drive hire - will the hirer top up the fluid with the correct spec oil. Also if you hire in any attachments - breaker, jack hammer etc, then they may be full of a lower spec oil that the last machine was running off. Gear pumps are pretty bomb proof & relatively cheap to replace, often generic parts can be supplied cheaper (Flowfit, Interpart). If doing your own servicing long term the gear pumps are simpler to diagnose faults etc.
I went through all this when comparing the 8018 vs 8020 & came to the conclusion that the difference did not justify the extra cost (on paper at least) - probably not so on bigger machines. If you do go axial by no means agree to biodegradable hyd fluid, as these pumps have a much shorter life on it.
Yes, that last sentence is a bit concerning. I was planning on bio oil of some kind, given I might well be working near water. I was thinking perhaps that Panolin stuff might be a wise choice. Not so sue now.
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  #17   IP: 95.147.232.252
Old 26-05-2018, 10:47 PM
Old Operator Old Operator is offline
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Default Re: Gear pump v piston pump

To be honest I got the bit re the higher spec oil from a hydraulics design forum
I used to be a member of. Various experts from such companies as Eaton & Rexroth regularly used to show up there. If I can find it again I will post a link to it. I took it on board because I wondered if the correct oil would have been used in a second hand machine. All this goes back to me being involved in design of very small kit machines - I was interested at the time in a very small spider. I do know that a small variable pump could not be got for less than 1300 Euros whereas a single gear pump was about 50 & a twin unequal was about 180. These were if the sizes you might put on a 9 to 13 Hp Honda.

The 8018 had a triple gear set as std, with twin axial + 1 gear as an option, the 8020 had the axials only.
I doubt I am the best to ask in all this because I drove & part owned an old 3C Mk 3 for years, had to be my own fitter, & we ran the thing on a tight budget. It still runs, a farmer has it.
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  #18   IP: 95.147.232.252
Old 26-05-2018, 10:49 PM
Old Operator Old Operator is offline
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Default Re: Gear pump v piston pump

To be honest I got the bit re the higher spec oil from a hydraulics design forum
I used to be a member of. Various experts from such companies as Eaton & Rexroth regularly used to show up there. If I can find it again I will post a link to it. I took it on board because I wondered if the correct oil would have been used in a second hand machine. All this goes back to me being involved in design of very small kit machines - I was interested at the time in a very small spider. I do know that a small variable pump could not be got for less than 1300 Euros whereas a single gear pump was about 50 & a twin unequal was about 180. These were if the sizes you might put on a 9 to 13 Hp Honda.

The 8018 had a triple gear set as std, with twin axial + 1 gear as an option, the 8020 had the axials only.
I doubt I am the best to ask in all this because I drove & part owned an old 3C Mk 3 for years, had to be my own fitter, & we ran the thing on a tight budget. It still runs, a farmer has it.
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  #19   IP: 109.146.120.232
Old 26-05-2018, 11:33 PM
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V8Druid V8Druid is offline
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Default Re: Gear pump v piston pump

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Originally Posted by pond digger View Post
Yes, that last sentence is a bit concerning. I was planning on bio oil of some kind, given I might well be working near water. I was thinking perhaps that Panolin stuff might be a wise choice. Not so sure now.
well like I said Chris .... Drema's been on it all it's life, in water treatment plants, hence the use of the Fuchs Plantohyd 40N

Currently at 5,500-ish hrs .... smelly ... and sticky stuff though, if it gets on the floor. Don't half bind planings
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  #20   IP: 109.146.120.232
Old 26-05-2018, 11:38 PM
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V8Druid V8Druid is offline
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Default Re: Gear pump v piston pump

Quote:
Originally Posted by Old Operator View Post
To be honest I got the bit re the higher spec oil from a hydraulics design forum
I used to be a member of. Various experts from such companies as Eaton & Rexroth regularly used to show up there. If I can find it again I will post a link to it. I took it on board because I wondered if the correct oil would have been used in a second hand machine. All this goes back to me being involved in design of very small kit machines - I was interested at the time in a very small spider. I do know that a small variable pump could not be got for less than 1300 Euros whereas a single gear pump was about 50 & a twin unequal was about 180. These were if the sizes you might put on a 9 to 13 Hp Honda.

The 8018 had a triple gear set as std, with twin axial + 1 gear as an option, the 8020 had the axials only.
I doubt I am the best to ask in all this because I drove & part owned an old 3C Mk 3 for years, had to be my own fitter, & we ran the thing on a tight budget. It still runs, a farmer has it.
yeh you certainly would not want any old oil slung in with a bio-oil ..... totally im-miscible and intolerant of more than 1% contaminant .... frothing/foaming, separation and all sorts of other of chemical 'reactions' with additives, etc. ...... pretty well documented issues for sure
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