Calculating Loads for Static Fan of 6,060kg: Help Needed

[Peirianeg]

The attachment provided shows a frame in which a large fan is to be rested on. The fan is to remain static and has a weight of 6,060 kg and the location of the centre of gravity is shown in the attachment. Each frame member has a cross-section of 200h x 90w. I would like to know HOW to calculate the loads at each point. Could anyone please provide some help on this problem?

 

[SteamKing]

Are the points 1-8 the supports of the frame or the points at which the fan is to be attached to the frame?

 

[Ryoko]

The problem is statically indeterminate. To illustrate the problem, suppose that one of the mounts is sitting up a little higher than the others. Much of the weight would then be carried by that point while others did nothing. Of course in reality, the frame will have some give to help balance the load. The amount of give is not something that's very easy to solve by hand.

Is the fan going to be sitting on some vibration mounts? These would distribute the load and you can treat them like springs which makes the problem solvable.

 

[Peirianeg]

Points 1-8 can be considered as vibration mounts in which the load is distributed.

 

[Peirianeg]

Using the loads at each point I can then calculate the distribution percentage between the points to find out how evenly the load is being distributed.

 

[Ryoko]

It's still a tough problem to solve by hand since you have a big list of unknowns. You have the load at each point plus the resting height and angular rotation of the fan assembly.

 

[Peirianeg]

The resting height of the fan is 267mm. You could take the shaft diameter to be 100mm (stainless steel) and the speed can be taken as 1300rpm. These values differ depending on the type of fan used though, but for this example these values should be sufficient. Anymore information required, just let me know.

 

[Ryoko]

There's almost enough information, but I think you may have missed the point that it's a set of 11 simultaneous equations that need to be solved. That isn't something you want to solve by hand. It's usually easier to treat the load as a point load and assume a worst case loading arrangement while leaving yourself a safety margin. But you'll need to consult a structural engineer familiar with the appropriate building codes to do this for you.

 

[Peirianeg]

Okay, thanks for the advice. I will try and contact a structural engineer and see if I have any luck. Thanks again.