Trying to shed some weight on my design, any thoughts?
I am trying to design a lifting mechanism and I would love some insight/opinions as to how I can shed some weight off it.
The current weight I have for my mechanism is 187.5kg, however, this is supposed to be something that is "easily transportable"
I am using stainless steel. Originally we had 20.3m of steel with a cross section of 40mm x 40mm and 10mm thick. Seeing as 187.5kg is quite high I am looking to reduce the weight. 215
I will admit the material and cross section were chosen relatively arbitrarily, but we wanted to be sure that our structure could hold any load without actually worrying about the calculations for that.
The main stress that will be exerted on the beam is bending, as the structure is built like a table, and will have a weight suspended from the middle. I looked up that the yield stress for stainless steel is 193MPa (I took the lowest value I could find for safety reasons) and I have applied various different cross sections for the steel.
For my original dimensions 40 by 40 by 10mm thick:
O (sigma) for bending is (M*y)/(EI)
Assuming my table top is completely made of a hollow rectangle of stainless steel:
M = (2009.81500) (lifting 200kgs 50cm away from it) = 98100
I = (40^4 - 20^4)/3 = 800000
y = 20
E = 193MPa
Therefore Ob = 0.0127MPa
I worked in mm because 1kg/(mm*(s ^2)) = 1MPa
A reduced, solid cross section of 20mm gave a bending stress of:
M = 98100
I = (20^4)/3 = 53333
y = 10
E = 193MPa
Therefore Ob = 0.0953MPa
I know stainless steel is a very strong metal, which is why I leaned towards using it originally. I would just really like to know if the logic behind all of my calculations make sense? Am I on the right track for this or have I done something horribly wrong that I am unaware of? I am aware I did not include self weight, but did not see the need for it.
Thank you for reading, I would appreciate any thoughts on this.
Edit: this is for a university project, I am mainly looking for pointers on my conceptual design and work. 193