carousel storage & questions

[kp516]

Hi,

I am a student of mechanical engineering and that's my first post here.
First of all – I do not want to ask someone to calculate something for me.

I did my best (I hope all is correctly) – can you briefly check it and answer my additional questions? I am especially interested these questions – I always have some doubts during calculations.
I still have a feeling that I am missing some essentials and fundamentals regarding torque etc.
So - I went thru this project completely, now it's time to ask someone who knows more than me how far away from correctness I am.

--
Ok, so I need to roughly calculate carousel storage motor parameters - that's the task. Drawings in attachment came from brochures.

Please take a look at my attachment.

I am assuming that only 5 of boxes on one side will be loaded with 200 kg. This is the worst case.

Imagine I want to lift the lowest one up to 6 meters in let’s say 30 seconds.

W= mgh= (5*200 kg) * 10 m/s^2 * 6 m = 60000J = 60 kJ

P= W/t = 60000 J/30 s = 2000 W = 2 kW <- required motor power


Q1) There is a gear in my sketch – does this gear has any influence to formulas for power used above?

Q2) By the way – if all boxes will be loaded to max can it be calculated like a lift with counterweight?

Can anyone provide more information about “counterweight effect” which “helps” motor?

----

Now I'm calculating a torque_motor and speed:

torque_motor / radius_1 = torque_2 / radius_2

torque_2 / radius_2 = weight -> torque_2 = weight * radius_2

so:

torque_motor / radius_1 = (weight * radius_2) / radius_2 -> torque_motor = weight * radius_1

so torque_motor = 10000N * 0,5m (more or less) = 5000 Nm

Q3) This is a minimum of course – how much additional percentage do you suggest to add considering belt efficiency etc.?

---

speed (0,2m/sec)

rps_motor * radius_1 = rps_gear_2 * radius_2

rps_gear2 * 2 * pi * radius_2 = velocity_weight -> rps_gear2 = velocity_weight / (2 * pi * radius_2)

so

rps_motor = ((velocity_weight / (2 * pi * radius_2)) * radius_2) / radius_1

rps_motor = velocity_weight / (2 * pi * radius_1)


Q4) BUT NOW PLEASE NOTICE that there is no radius_2 in both of these equations (torque and speed)! So what’s the reason of this gear (bigger pulley)?... maybe equations are in the fact are not ok? THIS IS SOMETHING MY INTUITION CAN NOT UNDERSTAND, but if my formulas are ok - then the motor shaft could be directly attached to big pulley?



Q5) By the way – if torque and speed are given now, isn’t it natural that there must be a motor power which is combined with this parameters – on the other hand – was it required to determine power at the beginning of this post?

Q6) Any other tips for this application?


Thanks for anyone who will support me a little bit!

 

[tygerdawg]

Not going to review your equations much. But don't believe you're on the right path.

You must supply torque to the driving axle of the bucket elevator. The torque required = "peak torque" :
[ul]
[li]torque needed to accelerate all rotational masses up to speed[/li]
[li]torque needed to accelerate all translational masses up to speed[/li]
[li]torque needed to lift masses against gravity[/li]
[li]torque needed to overcome friction[/li]
[li]and so on...hope you get the idea[/li]
[/ul]

That acceleration thing is T = (mass moment of inertia "J") x (rotational acceleration "alpha"), where alpha = (delta velocity) / (delta time).

Sum all torques to Peak Torque, add a Safety Factor, buy a gear motor to match. You can learn a lot from gearmotor manufacturer's catalogs and engineering guides. Also websearch & download the Smart Motion Cheat Sheet with all those dynamics equations.

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering

http://www.bluetechnik.com