oledinamico cylinder - cushioning dimensioning / braking system

[braudo]

Good morning to all,
I have to design a braking system for a hydraulic cylinder with this principle:
- before arriving at the end-race the cylinder passes in front of the hole of the oil mouth, in fact choking it
- while the hole is rubbed, the oil comes out through a meato (clearence or gap) between the piston and inner diameter of the cylinder
- the fall of delta p determines how slow the race

given to large lines the principle with which I want to perform braking, I must determine the size of the oil passage meate
during the hole chopping.
this meato (or clearance) is derived from a formula that I found on a treaty of an Indian professor
trivially, by doing the reverse formula you could get c, but unfortunately I do not have any other notions so deep of algebra
to solve the formula.


I ask anyone who has knowledge/experiences about it if I can help.
these cylinder data:

alesaggio = 63mm
cylinder stroke = 360 mm
brake stroke = 25,4 mm
pressure = 207 bar
max cylinder speed = 70 mm/sec
arrival speed = 7.25 mm/sec
output during braking = 0,882 - 2,05 l/min

thanks to who will help me.

 

[meccanicamg]

I would say that apart from finding formulas without knowing what's behind it can be more harmful than useful, I would say that first you have to understand that a hydraulic brake of damping works because you force the oil to pass in a small hole at reduced reach where the pressure rises, there are high load losses, and then the oil comes out little at a time making it slow down.
the shutter profile made as extension of the stem changes the way to slow down more or less gently.
Moreover the adjustment screw manages the fine adjustment of the oil flow in braking and therefore increases or decreases the damping time.

but buying a hydraulic cylinder already made and dimensioned by a serious manufacturer does not agree?
I'll train you some notes where to think.


we are talking about 13 l/min to be downloaded from the rear chamber at speeds of 70 mm/s to brake to a tenth of the speed i.e. to 7 mm/s with capacity about 1 l/min I would say that by making the account of the servant you will have to have a 2 mm hole adjustable screw.
talk about speed of arrival and flow rates but you have not given the diameter of the stem that is fundamental if you have to size the front brake.

 

[meccanicamg]

Moreover the technique attached to you to make braking with diameter of the shutter poor compared to the hole, not regulated by screw is a bad system for the management of a braking especially if the braking mass is high.

 

[braudo]

Hi mecca (I hope the alias is right ), while I thank you for the critical answer and for the schematic contributions you gave me and I ask you in advance to apologize if I wanted to fix as a starting point of discussion, how much I found on the net.
Let's say that what was posted was very close to the concept of cushioning that I would like to apply to the cylinder I'm designing, and this in response to the question about buying a cylinder directly from a manufacturer.
work in a company that makes cylinders, and the system in question has the task to brake the arm of a sprayer machine, avoiding that it closes on the structure with too much violence.
all this at a reduced cost, therefore avoiding using adjustment screws that, however useful, is not necessary to my system, and for this I am directed towards a system with meato (in the formula called "clearence").

said this, and I repeat, as a true profane in the matter, probably a braking with "nasino" is better than the piston passing in front of the hole and strozza. As soon as I align myself with the different works, I will try to study what you posted to me and in case I will bother you with some questions (in case I thank you in advance).
then I wanted to ask you the value of 13 l/min where you got it. I can't tell if you've considered the 207 pressure bars.
is it appropriate to ask our customer, so we will have to make the cylinder, the mass to be braked? Sorry the banal question, but I see it's a fact that I've never seen it give us.

Thank you for the moment.

 

[meccanicamg]

If you try to look at the atos catalog there are formulas related to decelerations and there is the speech of mass and kinetic energy to be dissipated. you will find the design on a tilted plane that shows you in synthesis the concept. If you don't know how the application is made you can hardly measure it right...then without adjustment you have no margin of error and you'll have to do some test at the counter with a similar cylinder.