Spring design for lifting a cover 1

[CampEngr]

I am assisting a client who is using a 275 gallon home heating oil tank as an out door cooker. He's laid it on its side, and cut it horizontally. He wants to put hinges on one side and use what were the bosses for the feet to mount a handle. The problem is that the lid will be dangerously heavy. I've suggested that he use either a coil spring that adds torsion as the lid closes, or perhaps a coil spring wrapped around three pins, two mounted on the lower section, and fastened to the third pin on the lid. I haven't considered that sort of design since undergrad school, but I know that it can be done. (Incidentally, my personal preference is the torsion setup around a rod, in case it lets go).
Anyone know how to approach this, and then specify and find the parts to make this happen?

 

[TheTick]

I've done dozens of these on a smaller scale for car console hinges.

The best place to start is to make a graph of closing torque versus angular position. Closing torque is a function of the lid weight, distance of CG from pivot, and cosine of CG position from vertical over the pivot.

From there, you can determine how much torque you want to exert to counter the lid weight torque. Determine counterbalance torque for two key points and you will have a straight line which shows spring rate (torque per degree) and preload torque.

I may have a spreadsheet which does this.

I could be the world's greatest underachiever, if I could just learn to apply myself.

http://www.EsoxRepublic.com

-SolidWorks API VB programming help