Request help for my project black 600

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Ruthenian
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Request help for my project black 600




by Ruthenian » 08/09/12, 17:16

Today I have finished designing my hydraulic mast.
Before going further I wanted to do a test of going up empty.

Fortunately; it doesn't go up ..

2.5 Tons cylinder
Mat 12 meters
Weight 195 Kg.

I don't know if it's a cylinder or pump problem. As soon as the climb test, the candelabra tries to climb and I can no longer pump.

I must have made a serious miscalculation to push.

Starting angle of the cylinder about 20 °.

Can anyone help me with the calculations?
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loop
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by loop » 08/09/12, 21:56

Hi ruthene,

The angle of inclination alone does not make it possible to determine the lever arm of the jack.

To schematize, I made you a sketch:

We can consider that the weight of the mat is exerted at half of its length (center of gravity). To raise the latter, it is therefore necessary to apply to it, thanks to the jack, a moment at least equal to the moment of the weight relative to the axis of articulation.

Weight moment = Lp x D = 6m x 195 daN = 1170 mdaN

Moment of the cylinder = Lf x F = Lf x 2500 daN

Hence Lf = 1170/2500 = 0.468 m (it is a minimum)

You may encounter 2 sizing problems during design.
You want to be able to raise -> you put the right lever arm but the stroke is insufficient to reach the vertical.
Your cylinder is too weak in section -> you are not reaching the right force.

In this type of kinematics, it is necessary to check the departure geometry, that of arrival and some intermediate positions, to be sure that the jack will be able to retain the load.
Is the operating pressure of the pump sufficient? (180 bars?)

Image

Give me the cylinder stroke, the piston section, the pressure reached and I will determine all of this for you Monday at the office.

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by Ruthenian » 09/09/12, 00:43

Thank you for your help:
Here is the data I can give you.
Cylinder: 570 - 970 mm
Max stroke: 400 mm
Inner rod diameter: 25 mm
Diameter External cylinder 50mm
Piston diameter (I think): 40 mm
Pushed to 2.5 Tons

Candelabra: 12 meters.
Weight: 195kg
Wind turbine + adaptation and weather station about 40 kg:
Cable and sheath: 20 kg.

Image

Image

the pump and the cylinder:

http://www.ebay.co.uk/itm/Hydraulic-D-A ... 48396f344d

..
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loop
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by loop » 09/09/12, 09:23

Bonjour,

At first sight, the actuator lever arm is too weak.
Try to measure the length L according to the photo below, virtually extending the cylinder axis.

Image

Regarding hydraulics:

The cylinder does have a D40 piston, i.e. an area of ​​12.56 cm2
At an operating pressure of 200 bars it effectively pushes 2.5 T

The pump can go up to 350 bars but there is a built-in pressure relief valve which may be set at the factory to 200 bars to protect the cylinder.

On the other hand, I must warn you about the use of a double effect system in your application.
During the lifting phase, the load applied to the cylinder causes the large surface of the piston to work -> the pressure chamber is on the correct side. The chamber on the rod side will empty directly into the reserve of the pump.
During the descent phase, it's the opposite, you send the pressure on the rod side to tilt the mast, but as soon as the center of gravity has passed to the other side of the articulation point, the mast will want to continue movement alone. This is where it will become dangerous insofar as the small surface of the jack will work in load retention -> cavitation and there is any risk of suddenly falling.
It will therefore be necessary to check that by replacing the distribution lever on the "raised" side, you will be able to control the descent.
Otherwise there are "parachute" valves which slow down the flow in one direction.

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Philippe Schutt
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by Philippe Schutt » 09/09/12, 10:08

maybe if you compensate part of the weight of the pole with a spring or a counterweight? Especially a spring, whose force is proportional to the deformation, would give the most force when you need it the most, and does not need to be in contact throughout the race.
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by Ruthenian » 09/09/12, 10:48

Looping -> I have a lever arm of around 225mm.
For the descent you are right, by the way when testing we realized that there was no restraint. We were wondering if it was normal or if the pump is out of order. Can you tell me if this is normal?
If this is normal, can you tell me what I need to manage the descent and if you see it in the shortcut I put you above to see what it looks like.
For the pressure too, I don't have a mano so I don't know how much the pump is limited. The fact remains that as soon as we start the ascent phase, we feel a relief but it blocks direct.

Philippe => I don't understand your spring story.
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by Philippe Schutt » 09/09/12, 18:27

At 675 mm from the axis, your 195 kg represent 1733 kg, and the 40 kg another 711 kg, or 2444 kg.
Your jack pushing at an angle of 20Â ° you must multiply your 2500 kg by the sinus, or 0.34. You actually have 850 kg of effective push.
a further 1600 kg of thrust must be found perpendicular to the pole, i.e. 4700 kg at 20 °. In all you would need a jack of 2444 / 0.34 = 7188 kg and the axes quite sturdy.

Or else, modify the assembly so that the cylinder is vertical when the mast is laid down, but then the stroke will be much greater.

edit: By putting 2 cylinders at 330 from the axis and which are vertical when the mast is laid down it would go.
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by loop » 09/09/12, 21:55

Good evening,

A lever arm of 225 is clearly too weak, or as Philippe mentioned, you would have to use 2 cylinders, and you would still be too tight.
In any case, it will be necessary to modify the points of application of the forces in order to straighten the jack.
You can either dig in the ground or put the jack on the side of the pole. I confirm this to you after the graphic determination of the kinematics.

For load retention, it is normal that the pump with double-acting valve does not do this, unless the lever is raised / lowered in the upward direction, as soon as the mast begins to fall and drop a bit of debit by hand. It is frankly dangerous.
To limit the rate of descent, therefore the speed during tilting, you need an accessory like this (unidirectional model):

Image

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by Ruthenian » 09/09/12, 22:52

Philippe Schutt wrote:At 675 mm from the axis, your 195 kg represent 1733 kg, and the 40 kg another 711 kg, or 2444 kg.
Your jack pushing at an angle of 20Â ° you must multiply your 2500 kg by the sinus, or 0.34. You actually have 850 kg of effective push.
a further 1600 kg of thrust must be found perpendicular to the pole, i.e. 4700 kg at 20 °. In all you would need a jack of 2444 / 0.34 = 7188 kg and the axes quite sturdy.

Or else, modify the assembly so that the cylinder is vertical when the mast is laid down, but then the stroke will be much greater.

edit: By putting 2 cylinders at 330 from the axis and which are vertical when the mast is laid down it would go.


Philippe and looping thank you for your explanations,
I do not understand the 1733 kg.

Looping, I hope your simulations will be encouraging.

For the axes, what diameter is necessary for 2.5 T, 4 T and 7 T?
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by Philippe Schutt » 10/09/12, 11:39

195 * 6 / 0.675 = 1733
and the 711 = 40 * 12 / 0.675

At the axis it is necessary to count with 7T therefore axis of 20mm

And in my opinion the simplest and cheapest will be to dig as Looping says to have the vertical cylinder, reduce the center distance to 330 because of the short stroke and put 2.

Relieving with a spring, at this level of force will probably be too expensive.
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