help pinion rack

[garide]

Good morning

I ask help to you for the sizing of a rack and a pinion, I searched in the forum and around but not found great things, and are at the first experience in the matter.

My application is strange and I hope I can explain it well.

the pivot that rotates on one side has a toothed wheel, hooked to the rack, on the other there is hooked a brake (like that of a bicycle) and the rack is moved by an oleodynamic cylinder.

the application previews this, from the stand position the pin has to rotate for 8 turns clockwise, stop for a couple of minutes, then turn of another 8 turns anticlockwise to return to the initial position. to move the pin and win the brake resistance, I have to impose an initial force of 20kg , or made a test with a dynamometric key
how do I dimensional the toothed wheel and the rack so that it resists and does not break, all possible with less encumbrance possible, in fact the larger the toothed wheel, the longer the rack and the more running I will need in the pencil, occupying more and more space.

I read around that the size of the toothed wheel depends a lot on the effort it will have to support, but an example to understand how I did not find it.

this is the first part of the problem, the second concerns the sizing of the pencil.
the 20 kg of rotational force impressed in the dynamometric key, corresponding to 20 kg of linear force that must develop from the pencil? If I'm not mistaken for a levers speech, I think the bigger the toothed wheel the less force will serve, the smaller, the more force must have the pencil
Thank you.

 

[gerod]

the sizing of a toothed/coated wheel was, as you said, already treated.
the sizing passes through a bending test of the tooth + verification to wear.
using google you will find many docs in this regard.
without input data is a bit hard to make a sizing. did you not write the masses, the speeds, etc. in short, without these data that you do?

the 20 kg of rotational force impressed in the dynamometric key, corresponding to 20 kg of linear force that must develop from the pencil? If I'm not mistaken for a levers speech, I think the bigger the toothed wheel the less force will serve, the smaller, the more force must have the pencil

on this topic I can tell you that I have already answered a few weeks ago.
Let's sort out ideas.
a dynamometric key measures a couple (well I said couple, not moment) not a force. and the pencil where it pushes, or where is the force?

here we need a scheme otherwise it is like talking about the sex of angels.
Thank you.

 

[meccanicamg]

Hello garide,
Let's see if I understand cinematism: hydraulic cylinder that pushes on a rack and discharges the force on the teeth of the pinion that transforms the force into couple. on the pinion tree there is the strong torque made by brake.

1) for checking pinion rack use uni 8862, as indicated in other posts and it is sufficient to check the pinion provided the rack has similar characteristics of material and finishing

2) for hydraulic actuator, force = pressure * area at the limit with yields

3) if the kinematics is right, except yields, you have that at greater radius of pinion you get a larger pair, keeping constant the strength of the cylinder

4) with dynamometer you measured a pair in kg*m not a force in kg.

the material on the net is not missing, the summary indications you have. If you want more details, you need to post more data, calculation drafts etc.