Hydraulic spec help

[Justme]

I have a firewood processor that is powered via a PTO.

I wish to remove the need for a tractor & power it via a stand alone engine.

I could just find a pto engine in the 40hp range & shaft it to the machine.

However having a set of pumps driven direct from the engine would open up a lot of options.
For a start having the noise further away from the operator.

The makers spec for pto is 40hp but via elec motor 11kw (15hp).

That sounds odd.

Ok pto is running at 1500-1620 rpm via a 3-1 gearbox & elec motor direct coupled at 1440rpm.

They use different pumps.
pto powered 2 x 22.5cc & 1 x 8.2cc
Elec powered 2 x 25cc & 1 x 11cc

I get that would make up for the reduced rpm. But why the huge power needed difference?

When I calc the flow rates & psi at max output the pto power actually needed is 30hp. So accounting for gearbox losses 40hp min seems sensible.

What am I missing re the big difference between pto & elec?

 

[doobin]

I have a firewood processor that is powered via a PTO.

I wish to remove the need for a tractor & power it via a stand alone engine.

I could just find a pto engine in the 40hp range & shaft it to the machine.

However having a set of pumps driven direct from the engine would open up a lot of options.
For a start having the noise further away from the operator.

The makers spec for pto is 40hp but via elec motor 11kw (15hp).

That sounds odd.

Ok pto is running at 1500-1620 rpm via a 3-1 gearbox & elec motor direct coupled at 1440rpm.

They use different pumps.
pto powered 2 x 22.5cc & 1 x 8.2cc
Elec powered 2 x 25cc & 1 x 11cc

I get that would make up for the reduced rpm. But why the huge power needed difference?

When I calc the flow rates & psi at max output the pto power actually needed is 30hp. So accounting for gearbox losses 40hp min seems sensible.

What am I missing re the big difference between pto & elec?

On the electric version is the saw driven via hydraulics or is it an electric motor?

 

[Justme]

On the electric version is the saw driven via hydraulics or is it an electric motor?

Every thing is hydraulic. Powered via the three linked pumps.

 

[craig]

Does it mean the HP of the tractor, rather that the power at the shaft?

 

[V8Druid]

if it's a 3:1 step up rather than reduction, it'll need plenty of donkeys to cover it ... 15 Leccy HP @ 1440 rpm -- x 3 = 45 donkeys 'stepping up' to the 1500 rpm (think of it like reduction / mechanical advantage, in reverse)

 

[Justme]

Does it mean the HP of the tractor, rather that the power at the shaft?

40hp at the shaft

That said the specs on mine are 58hp at engine & 51hp at pto. SO would not make a huge difference.

 

[Justme]

if it's a 3:1 step up rather than reduction, it'll need plenty of donkeys to cover it ... 15 Leccy HP @ 1440 rpm -- x 3 = 45 donkeys 'stepping up' to the 1500 rpm (think of it like reduction / mechanical advantage, in reverse)

I agree it will use some but surely not 15-25hp worth?

That would be a serious amount of heat to dissipate.

 

[Justme]

Original plan was to use a 22hp engine but the pump specs suggest that's far too low.

Jumping up to 35-40hp massively increases cost & complexity of the build.

 

[Quattromike]

If you have 45hp at 540 rpm and feed that through a gearbox approximately 3:1 ratio to get 1500 rpm you effectively divide by 3 which gives you 15 hp at 1500 rpm.

 

[Rob65]

I think I have read somewhere that a hydraulic system driven by an electric motor will require twice the HP if an engine is used.
What the justification for this was I can’t remember. It might have been to do with engine power at the same rpm as the electric motor so no help really.

 

[Justme]

If you have 45hp at 540 rpm and feed that through a gearbox approximately 3:1 ratio to get 1500 rpm you effectively divide by 3 which gives you 15 hp at 1500 rpm.

Ok so how does that mesh with the pumps spec that needs 30hp to work at peak?

 

[V8Druid]

I agree it will use some but surely not 15-25hp worth?

That would be a serious amount of heat to dissipate.

consider it in leverage terms ... to lift 100kgs with a bar with a fulcrum set at a quarter the length of the bar ... you'd need 33kgs down force .. 3:1 advantage in your favour to balance the energies/down forces... now consider it the other way round ... to lift the 33kgs it'd need 100kgs ... mechanical disadvantage
gears are the same principle ... a 3:1 advantage turning summat reduces the effort required to a 1/3rd of that of a direct drive .... reverse it to a mechanical disadvantage - 1:3 and you need triple the effort/power

 

[Justme]

consider it in leverage terms ... to lift 100kgs with a bar with a fulcrum set at a quarter the length of the bar ... you'd need 33kgs down force .. 3:1 advantage in your favour to balance the energies/down forces... now consider it the other way round ... to lift the 33kgs it'd need 100kgs ... mechanical disadvantage
gears are the same principle ... a 3:1 advantage turning summat reduces the effort required to a 1/3rd of that of a direct drive .... reverse it to a mechanical disadvantage - 1:3 and you need triple the effort/power

Yes I get that but all that energy must be going somewhere. Normally lost as heat.

I cant see over 10kw of heat not cooking the gearbox.

 

[V8Druid]

Yes I get that but all that energy must be going somewhere. Normally lost as heat.

I cant see over 10kw of heat not cooking the gearbox.

or consumed as transferred energy, burnt elsewhere - saw blade/rams/whatever -- the max energy is only required at full load

 

[Justme]

or consumed as transferred energy, burnt elsewhere - saw blade/rams/whatever -- the max energy is only required at full load

Every cut / split cycle will be full load as both can be done at same time.

 

[GazCro]

One thing about electric motors to remember is that they produce max power and torque all the time.

 

[JD450A]

Lister TS3 or similar with a large capable flywheel. Be fine IMHO

As for electric vs engine. Electric is often far torquier, particularly at lowish revs. Hence larger pumps to keep the flow rate right at lower RPM. You will overcome it with a engine with a large flywheel to cover the inertia required and keep it from stalling at peak load.

Pick up a old dumper engine and give it a go. Worst case it does'nt work.

 

[Mogman]

I have a firewood processor that is powered via a PTO.

I wish to remove the need for a tractor & power it via a stand alone engine.

I could just find a pto engine in the 40hp range & shaft it to the machine.

However having a set of pumps driven direct from the engine would open up a lot of options.
For a start having the noise further away from the operator.

The makers spec for pto is 40hp but via elec motor 11kw (15hp).

That sounds odd.

Ok pto is running at 1500-1620 rpm via a 3-1 gearbox & elec motor direct coupled at 1440rpm.

They use different pumps.
pto powered 2 x 22.5cc & 1 x 8.2cc
Elec powered 2 x 25cc & 1 x 11cc

I get that would make up for the reduced rpm. But why the huge power needed difference?

When I calc the flow rates & psi at max output the pto power actually needed is 30hp. So accounting for gearbox losses 40hp min seems sensible.

What am I missing re the big difference between pto & elec?

I may have just the thing for you

air cooled deutz engine with a swash and gear pump mounted on the back hydraulic oil cooler radiator and the control dashboard I’ve probably got a oil tank somewhere too

 

[V8Druid]

I may have just the thing for you
View attachment 19244View attachment 19245View attachment 19246View attachment 19247View attachment 19248View attachment 19249
air cooled deutz engine with a swash and gear pump mounted on the back hydraulic oil cooler radiator and the control dashboard I’ve probably got a oil tank somewhere too

tha's the same lump as in the 'Drema... BF4M with integrated liquid cooling system ... that's water-jacketed with a rad at the back/left side of the motor BTLs ........ great motors and used everywhere ..... that looks a nice package for what the OP wants

 

[Mogman]

Also got this lump

not been commissioned since a total rebuild then they asked me to shift it
It was used to power this press