torque calculation- solar tracker

[NTRSwamy]

my team is designing a solar tracker, the module mounting structure has been designed considering dead load and wind load into consideration. I am supposed to calculate the torque or thrust required to tilt or rotate the structure using a linear or rotary electrical actuator. The arrangement is similar to a mechanism used to operate elevators in aircraft, i.e. using a push-pull rod, which is connected to torque arm.

The only difference is that, much of the load is carried by the leg members in my case. as for calculation, I am getting a very high value of torque. I have attached the calculation, please look into that. and I request you to comment on it.

if you need any more information, let me know.

 

[IRstuff]

A picture would probably help

TTFN
faq731-376

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[chicopee]

Half of the panel weights and half of the wind load normal to the solar panels should assist the torque. There should also be a shear load from the wind to assist the torque. From the shear wind there should also be an uplift on the panel thereby lessening the weights of the panels.

 

[IRstuff]

Missed your drawing. Is the drawing showing an elevation view or plan view? Where is your pivot point? The way your drawing looks, the pivot point is near the tie rod? Your wind load is absurd, I think; it comes to 105 mph, which is hurricane force from Wikipedia, or tornado.. Are you really going to be move solar panels during a hurricane or tornado storm? IS your structural guy confused by maximum wind load as opposed to operational wind load? Your operational wind load should be considerably less. MIL-HDBK-310 lists a 1% extreme wind speed of 22 m/s. IF your wind speeds are that high and more often, you should be designing a wind mill and not a solar farm.

You need to identify where your pivot point is. Hypothetically, it should be close to the panel than the tie rod. In which case, you should have some mechanical advantage due to the lever arm difference between the tie rod arm va, the mounting arm. This would allow you to trade torque for a longer throw on the tie rod. There is no reason to make this worse, since you really don't have a time constraint, so the tie rod can take a rather long time to move the panels.

TTFN
faq731-376

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[tbuelna]

Looking at the sketch provided, there does not seem to be enough details of the mechanism given to determine what the required output from the actuator should be. For example, the coefficient of friction in the pivot bearing is provided, but the radius the sliding contact in this pivot bearing occurs at is not given. The same goes for the pivot joints in the rest of the mechanism.

 

[MikeHalloran]

Gravity shouldn't be a huge part of the problem, provided that you use a counterbalanced 'equatorial mount'. Google the quoted phrase real soon.


Mike Halloran
Pembroke Pines, FL, USA

 

[rb1957]

so the overall assembly consists of 6 "structures" which consist of 12 modules
and the steel frame for a structure weighs 200kg and the module (solar array?) weighs 20g ?

a wind load of 178kg per module for a wind of 47 m/s ... can you detail that calc ?

does the wind and weight cause the same torque ?

i guess this structure moves slow enough that you don't need to consider the Iw^2 of the arrays ?

is the wind load constant ? at 0deg wouldn't the wind load be zero ?

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