Large lid support prop strut

[loughfy]

Let's be honest I am an electrical engineer, but I have been given a very mechanical problem to solve (and I cant do it).

My company produces large GRP tanks with lids that measure 1.3M by 2M, each lid wieghs 37Kg and are hinged on one side.

The problem is that at the moment we use gas strutts to keep these lids open (the same one that are used on the boots of cars), however some of our customers do not like thase because on occasion they go POP. (twice in living history, I understand!!!)

So I have been asked to find a product that can replace them.

It will need to ;
Be located at the opening end of the lid
Be able to be locked in open position
Approx 1.2M when fully extended
Be able to be fully operated in safty by one person

If we could buy one off the shelf then this would be preferred, however if I need to get one made any ideas on how it should operate.

Martin Lough

 

[bradphillips]

Are you using only one strut?
If you are then you are asking for trouble because they are not designed to handle a twisting load.
If you are using 2 struts, possibly you could oversize them so if one fails,the lid will not close abruptly.

The failed strut could be replaced.

Find out what causes the strut to "pop" .

 

[loughfy]

We are using two.
As I say the only time they have pop is on two occasion. As i understand this can occasionally happen.

The problem is not so much the lid coming down although this is also a percieved problem (ie it could possible happen, but never has); no the reason the customer does not like them any longer is the risk assessment that the operator could be startled by the pop and jump into the tank (no laughing please) I need to find an alternitive or a back up to the gas struts.

 

[bradphillips]

There are hydraulic dampers or gas springs. I don't know if hydraulic dampers "pop" like an air spring strut.A damper designer should be able to solve the problem. Risk Assessment will find a problem with hydraulic damper.

 

[MadMango]

Look into door checks, not just gas springs. These lock in the open position.

http://www.allegiscorp.com/jsp/displayTypes.jsp?cat=Door Assists

Also, you might want to investigate mechanical struts over gas springs. You won't have to worry about seals or temperature extremes.

http://www.asraymond.com/mechanical/default.asp

MadMango
"Probable impossibilities are to be preferred to improbable possibilities."
Have you read faq731-376 to make the best use of Eng-Tips Forums?

 

[MintJulep]

I have never seen an off-the-shelf cover stay this long. Doesn't mean that they don't exist though.

I would be inclined to use two telescoping tubes with a locking mechanism similar to the half ball and spring that holds vacuum cleaner extension wands together.

The advantage to this approach is that it can be dimensionally identical to the existing struts, so no further desing change is needed, and it could be retrofitted in the field.

 

[unclesyd]

Why not go back to the old style over center mechanisms used on bonnets of the cars of old. They were spring assisted or just plain mechanical. There are still in use on hoods of some trucks and cars.