dimensional emergency brake/station

[mecch]

Hello everyone, I would have a question to propose concerning the size of a disc brake:

on a rotation axis I have a pulley to which a load is connected and a counterweight through a rope. the same axis is connected to a brake and a motor. In practice it is a lift.

assuming that I can calculate angular acceleration with the formula:

w = summary(copies) / summary(moments of inertia)

for example we take the following case:

w = (cmotor - ccarico + ccontrappeso) / summary(j)

I would say that in conditions of station the torque provided by the brake must simply balance (by adding an appropriate safety margin) the torque provided by the load and that of the counterweight by writing
cfreno = (- fcarico + fcontrappeso) * rpuleggia.

in emergency conditions instead, assuming that the engine is removed power and neglecting the inertia, it is possible to replace the cfreno to the cmotore in the above equation:

cfreno = w * summary(j) + ccarico - ccontrappeso

or should I also add the required torque to the station?


Thank you.
greetings

Palo

 

[gerod]

Meanwhile welcome (a minimum presentation did not spoil!!!)
in emergency conditions always apply the balance of moments.
so if the engine is not there you have to balance all the components that participate (it is not true that the inertia of the motor + reducer does not contribute (you have to bring everything back to the main axis, that is on what you do the calculation).
I would say that there are the rules that in this case help you to perform the sizing properly.
From one ochhiata to harmonized standards under the lift directive.
Hi.

 

[mecch]

Meanwhile welcome (a minimum presentation did not spoil!!!)

Thank you in the meantime for the answer, excuse me if I've been a bit rough in submitting the question, I didn't even know how to start the speech and say I jumped. . .

(it is not true that the inertia of the motor + reducer does not contribute (you must report everything to the main axis, that is on what you do the calculation).

to verify if the formula is correct I applied 0 as deceleration value and I return the static torque value so I would say I am on the right path. then at the end the major module in the 4 cases of operation climbed/descent full load/empty will be the torque value for my brake, right?

regarding the inertia of the motor at the moment having not yet chosen it should not consider it in any case should be negligible regarding that of the plant that are a couple of tons of weight on the vertical. . .
I hope I'm not wrong, but in the end I will certainly make a general verification of the whole system.

I would say that there are the rules that in this case help you to perform the sizing properly.

Of course, it's the first thing I looked at but these only give me the permitted deceleration values not the moment.. .

Thank you very much for the answer

greetings,
Palo

 

[gerod]

regarding the inertia of the motor at the moment having not yet chosen it should not consider it in any case should be negligible regarding that of the plant that are a couple of tons of weight on the vertical. . .
I hope I'm not wrong, but in the end I will certainly make a general verification of the whole system.

inertia is important. consider a 1/100 report on the reducer ... and you will see that it is important. Meanwhile fixes a motor, then similar the calculation.
what norm do you use?

 

[mecch]

inertia is important. consider a 1/100 report on the reducer ... and you will see that it is important. Meanwhile fixes a motor, then similar the calculation.

In reality it is a system without a reducer however when I have the definitive data surely recalculates also with the component of the brake.

what norm do you use?

the reference standard is the en81.1/2008 (for cable systems) is the main one regarding the design of new installation plants.

at this point an important component that I miss is the force of friction. the direction of this will be directed in the opposite direction to the motion and sum algebraically to the weight force? about the first detachment friction where I could try some formula / coefficient to be able to make an estimate of the point to start the system?

greetings,
Palo

 

[gerod]

the friction force generates a braking moment (of course that is opposite to that generated by the load and the inertia - apart from the counterweight).
try or find formulas? .
depends on what you use, disc brakes, strain brakes?

to make an estimate of the point to start the system?

so to my nose I think I use a negative brake (without power it blocks the system) so what do you need the first detachment? When you drop the brake, don't you want to start with the brakes locked? How would you do that? I don't understand!

 

[mecch]

the friction force generates a braking moment (of course that is opposite to that generated by the load and the inertia - apart from the counterweight).[...]What do you need the first detachment?

the friction I would like to take into account is the one caused by the stripping of the skates on the guides, fe360 lubricated steel on smooth surfaces of plastic material. these are mounted on both the cabin and on the counterweight so what I thought was to sum up a friction force opposite to that weight if the cabin moves down and vice versa if it moves up the same do for the counterweight. the friction I do not consider it for the brake because it is a disc brake that as you have already said opens even before the plant leaves (it is kept electrically from the engine at this stage) and I suppose if in good state it does not have a residual couple when it is powered.
the first detachment is precisely that necessary to start the cabin and the counterweight that tend to "paste" to the guides when the plant is still.

greetings,
Palo

 

[gerod]

I didn't understand.
here you find something but I remember seeing other tabs on the web but I can't find them.http://www.tecnocentro.it/ita/tabella_coeff_attrito.htmhttp://www.itchiavari.org/chimica/tabelle/attrito.html

 

[MBT]

the friction I would like to take into account is the one caused by the stripping of the skates on the guides, fe360 lubricated steel on smooth surfaces of plastic material. these are mounted on both the cabin and on the counterweight so what I thought was to sum up a friction force opposite to that weight if the cabin moves down and vice versa if it moves up the same do for the counterweight. the friction I do not consider it for the brake because it is a disc brake that as you have already said opens even before the plant leaves (it is kept electrically from the engine at this stage) and I suppose if in good state it does not have a residual couple when it is powered.
the first detachment is precisely that necessary to start the cabin and the counterweight that tend to "paste" to the guides when the plant is still.

greetings,
Palo

Look, for the little experience I have..,
tribology is one of the most complicated and opinable sciences with which a mechanical designer can collide.
you just need a mismade process or a different type of lubricant, even as the piece is stored to change your calculations....

 

[mecch]

...
you just need a mismade process or a different type of lubricant, even as the piece is stored to change your calculations....

Perhaps I should consider a coefficient of general performance of the system type 0.9 or 0.8 oversized and who is seen in effect.

 

[MBT]

Perhaps I should consider a coefficient of general performance of the system type 0.9 or 0.8 oversized and who is seen in effect.

I would say yes...
I have seen friction of first detachment even 5 times the raving friction in operation. . .
the famous slip-stick.. .
But how do you expect the intensity? practically impossible.:frown:
in practice, try to stay tall with the torque/point strength, hoping that it is enough. :redface:

on general performance, also put 0.7
consider that with the going of time are born games, wears unforeseen frictions...

 

[gerod]

Perhaps I should consider a coefficient of general performance of the system type 0.9 or 0.8 oversized and who is seen in effect.

mmm, wrong approach especially on the "who's seen is seen". and if a tomorrow someone took you in front of a judge to prove the goodness of your calculations that you tell him?
do well the accounts, do not shoot, do not have too many doubts that then the calculations already hide errors.
do well a scheme of forces at stake and apply the most unfavourable situation, although it will be unlikely.
You're always on the side of the cheese because it puts people on it.
Hi.

 

[Francesco CATIA V5]

Hello, here is a link that can help you find the correct way to dimensioning.... click on this link : http://195.103.237.153/ministeries/... norms uni per %sector ascensors.htm? id=263

 

[gerod]

io userei queste.Commission communication on the application of Directive 95/16/ce of the European Parliament and of the Council of 29 June 1995 on the approximation of the laws of the Member States relating to liftsfresh day! ! ! !

the doc reported by francesco is old because, for example, the 10001 has been withdrawn!
I think others have been withdrawn.

 

[mecch]

It is always good to go through them even if I read them already. But I think they can help me from the point of view of the general criteria of design but in the detail of which forces and how to consider them I really think not...

with regard to the coefficients, rather than crazy in complex calculations that then as mbt says perhaps are not correct in the actual conditions of use I thought to establish myself to start a coefficient of performance that helped me to oversize the machine then surely before realize something commercial I should do tests on prototypes and however the maximum of the sfiga that can happen is that an undersized motor can not lift the load that is stopped on its brake. I don't see the question so dramatic, and in any case we're talking about values that should be negligible to the load otherwise I would have designed a machine to warm the guides more than to raise people.
Am I right? i.e. if the frictions become so important more than oversize the engine, I should find a system to reduce these frictions anyway.

greetings,
Palo

 

[Francesco CATIA V5]

I believe that the road above ♪ be the + appropriate, do not lose too much head on secondary calculations if you feel insecure but simply increase some point the safety coefficient, on certain oversized things is + impotent that make good figure for saving some euro.... then you see that everything else is automatic .

greetings