design trolley on tracks

[leonardo000333]

I know that only the meccanicmag title will say that it has been treated thousands of times and it is true, but I still have a question... if a cart rests with steel wheels on rails, but these wheels are not motrices or are crazy and the bike takes place thanks to a cremagle solidarity with the cart and to a gear motor with pinion on the ground, the crazy wheels will never be able to slip because they are not just driving? starting from station what factors of friction I use to calculate the moment that serves the rack?
I train you a sketch

 

[leonardo000333]

(the sketch is a frontal plane, the wheels do not go to slam on the pinion)

 

[Stan9411]

No. In these cases it can establish skating. If the friction coefficient between wheel and rail is too low, the wheel slides over it as a skate instead of creating a relative rotation .. as if you are on the ice and someone gives you a push.

 

[leonardo000333]

thank you, in fact, as I imagined, the problem is how I design wheel and rack because there is no skating? My cart can pass from a full load situation with 90000 to an exhaust with 8000n... is it a good problem?

 

[PIETRO2002]

Maybe it's not possible, not knowing the application, but replacing the wheels and putting skates?

 

[leonardo000333]

skates in what sense? the application is the transport of point-to-point materials with relatively low speed. the movement takes place along an axis and no more than one, I had thought instead of the tracks and wheels to put mad rollers on which it goes to lean the structure but the cost becomes excessive for the large amount of bearings to use, there is no formula for the design that takes into account the skate effect on the wheels?

 

[PIETRO2002]

but the cart that length has? What kind of race do you have to do? What speed do you have? put tracks with ball recirculation skates? to put a system like tank tracks? I threw you some idea from what was born what, if then maybe someone saw some ideas..

 

[leonardo000333]

the cart is 3 meters long and must have a linear move of 6 meters , the problem is that sometimes it can be loaded (serve a great moment to the rack) sometimes more unloaded (response skating for reduced weight agent on the wheels... tank tracks? ? ?

 

[Calender]

if you don't give us more directions it's difficult to guide you to the right choice. For example, in what environment does everything move? industrial warehouse,segheria,fonderia, port plants, candy factory ? You could draw some inspiration from the lifting and transport sector anyway. . I can see if I find a dispensation on this topic and I'll send it to you.

 

[meccanicamg]

Since it is yet another discussion, you could hook up to an existing one. ...just to maintain a completeness of topic.
the pinion on rack is tense therefore the whole couple uses it to constip.
the crazy wheels follow the bike of the carriage only if:
- support on the ground guide (it can be that you find a stone, a piece of iron, a transfer of the track etc.)
- and if the previous point is guaranteed there must be guaranteed the coefficient of friction multiplied by the vertical force of the wheel that contrasts the acceleration of inertia of the wheel.... otherwise even if not drive., the casso is accelerated but the wheel remains there.

Also remember that the crazy wheels consume couple due to the turning friction (reaction moved forward compared to the wheel center). since partially changes the eccentric reaction distance depending on the load, surely vacuum you will have a less difficulty and therefore less torque to roll the wheels.. .

can you place all the characteristics of wheels, weights, speed, accelerations, environment, etc?
But you couldn't put the rack on the ground?

 

[leonardo000333]

I could put it on the ground but then I should mount on the structure the gear. . .
As a speed I would like to have 2 available;0,5mt/s and 0.25m/s, I do not know how to accelerate but I think it is better a low acceleration in order not to increase the rack-route efforts.
when the system is loaded I have 100000 n to divide for 9 wheels on 3 tracks, when the system is unload I have 10000 n (always on 9 wheels)
I thought of using ball recirculation guides, they also seem interesting, I would avoid roller guides for the high cost, I need a 6 meter translation.

 

[leonardo000333]

the whole structure will go to a workshop where it can be that oil or similar paint the guides, even small-size chips (belt saw)

 

[meccanicamg]

what precision must have everything? can't you mount on traditional wheels instead of linear guides and skates that require milling?

 

[leonardo000333]

traditional wheels do you mean rubberized? However, the ball recirculation guides sell them already ready and I think they are obtained by extrusion, I don't know, they are aluminum profiles, because according to you the wheel-binary system in that situation is not possible to design it? the cart can not leave the trajectory established even if I would not define it a precision handling

 

[meccanicamg]

traditional wheels do you mean rubberized? However, the ball recirculation guides sell them already ready and I think they are obtained by extrusion, I don't know, they are aluminum profiles, because according to you the wheel-binary system in that situation is not possible to design it? the cart can not leave the trajectory established even if I would not define it a precision handling

I mean rail or similar iron wheels....see post 28 qui.
What are you talking about? Ball recirculation guides are made by a terrified track and a mounted cart. So...

but can you build some kind of trolley on normal rail?
It's a wagon weighing 10ton full load and 1ton empty...it's not so much stuff...I usually do them a little bigger... even up to 120ton.

 

[meccanicamg]

If it were a normal carriage, with two tracks, two wheel wheels and six crazy wheels ... if you touch them all on the track, we have that full load we can do the accelerations in 3 seconds. If they apply the same pair with the empty carriage, instead we will have a slip on the two wheels.
Let's imagine making it travel to 0.5m/s i.e. 30m/s which is a normal speed of semovent tanks.

10ton full load calculationcalculation at minimum load 1ton.for this reason your wagon is better than having the traction with pinion and rack, provided that the three seconds emergency stop are suitable for your application.

in the two calculations I kept the acceleration force equal....to have some balance then with the performance for the choice of the engine but in reality I should have changed the parameters and maintain the pair and therefore equal power....and it would have been worse....the slip would be much more accentuated.

However it would be good that the fixed carriage with weight reading so that you can manage the acceleration/deceleration ramp according to weight.

the crazy wheels however will strip and you will feel them whistle because you can not make them rest all unless you make a flexible frame. if they rest on the track all turn as long as the moment of friction and the moment of inertia of the mad wheels are in balance in relation to the coeffient of wheel/binary grip.

 

[leonardo000333]

so the optimal solution is the track with ball recirculation skate...which you mean that to stop it takes 3 seconds...I would like that when I stop the engine it stopped instantly but I think I understand that it is not so... what does a self-frenating engine need?

 

[meccanicamg]

so the optimal solution is the track with ball recirculation skate...which you mean that to stop it takes 3 seconds...I would like that when I stop the engine it stopped instantly but I think I understand that it is not so... what does a self-frenating engine need?

instantaneously there is nothing....if you want it to stop "instatedly" you have to consider 100/200 milliseconds....st cocks....we are at 15/30kw to brake. and you will have a deceleration force of 5 tons. . .

no brake motors serve to maintain the torque and do not serve to brake, otherwise burn them after about ten cycles.

must be done with motor, inverter, braking resistors bench if you want something so pushed.

but do you need all this? Do you have a client who wants too much? Do you not know what or how to offer an object? Where's the hippo?

 

[leonardo000333]

the problem is the final position of the cart, which must be more or less 5 mm, so if it puts 3 seconds to stop I should close the motor 3 seconds before the chosen position... hard enough

 

[meccanicamg]

if the final position is always at the same altitude you might think of air/oil decelerators type ace so that you dismorse the inertia of the carriage and get to beat accurately.

with a few hypotheses spannometrics comes as follows:and therefore would be a decelerator among these:even if I am convinced that the decelerator must be adjustable to ensure the position.

I am convinced that you can do differently, but you have to tell us better the application what transports, what the customer expects, what you are willing to do, an idea of budget....what we are doing an axis and not a wagon, we have to put on 2000€ of engine and 3000€ of electronics to manage it.. . .In the end it will take a nice toasted epicycloidal reducer, hoping you don't have to do too many cycles, otherwise you have to use a parallel orthogonal axes (so don't burn it).

but with this performance the uncontrolled load?