How to dimension an inflatable pneumatic jack?

inflatable air jacks with two stages

l in cm : width – E in cm : thickness – PG in bar : inflating pressure
L in cm : length or diameter – C in cm : stroke – P in kg : upward thrust

In order to dimension an inflatable pneumatic jack, you have to determine some criteria.

The choice of the MUSTpress®inflatable pneumatic jacks will depend on following criteria :

  •  Stroke: It is limited to the maximum stroke of the air jack :

C max. = 0.55 x l

how to dimension inflatable air jack?
  • Upward thrust:

The working surface (WS) of an inflatable pneumatic jack will decrease as the stroke increases. The upward thrust of an inflatable pneumatic jack is the product of the working surface by the inflatable pressure.

For a rectangular air jack :
W.S. = (L-(C+E) x 3.14/2) x (l-(C+E) x 3.14/2) cm²

For a square air jack:
W.S. = (L- (C+E) x 3.14/2) ² cm²

For a circular air jack:
W.S. = 3.14 x( (L-(C+E) x 3.14/2)/2)² cm²

                                                                  P = PG x WS

  • Mechanical resistance of the fabrics:

The maximum inflating pressure allowable of an inflatable pneumatic jack depends on the fabric’s mechanical resistance and the stroke.
R = 35 daN for standard – PG maxi = 2 x R/ (C+ E)

The best configuration will be obtained when the stroke divided by the WS is least. That increases the potential of upward thrust and inflation/deflation times of MUSTpress® air jacks .

Example: “Rectangular inflatable pneumatic jack: 30 x 20cm, C=4cm, PG =2 bar”
C max. = 11cm P = 218 x 2 = 436 KG.

Regarding the multi stage MUSTpress® inflatable pneumatic jack, the maximum stroke is a multiple of the maximum stroke of a simple stage air jack:

1,8 for a two-stage air jacks, 2,7 for a three-stage air jacks .
Concerning the upward thrust, you have to divide by 2 the stroke of a two stage inflatable pneumatic jack and by 3 for a three stage inflatable pneumatic jack and use the above formula.

Example : “Two-stages Rectangular air jacks : 30x20cm with a stroke of 4 cm and a working pressure of 2 bar ”.
C max. = 0,55 x 1,8 x 20 = 20 cm.
P = 325 x 2 = 650 KG.

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