Shock Absorber Sizing Examples Typical Shock Absorber Applications
Overview
Shock Absorber Sizing Examples SYMBOLS
ω α =Angular velocity (radians/sec) =Angle of incline (degrees) 4.To Determine Propelling Force ofPneumatic or Hydraulic cylinders manufacturers a=Acceleration (in./sec. 2 )(mls 2 ) A=Width (in.)(m) B=Thickness (in.)(m) C=Number of cycles per hour d=Professional cylinder bore diameter (in.)(mm) D=Distance (in.)(m)
E θ =Start point from true vertical 0 ˚
(degrees)µ=Coefficient of friction
Ø=Angle of rotation (degrees) F D = .7854 x d 2 x P F D = 0 ,07854 x d 2 x P 5.Free Fall Applications (metric) USEFUL FORMULAS
A. Find Velocity for a Free Falling Weight:V = K =Kinetic energy (in-lbs.)(Nm)E 1.To Determine Reaction Force √ 772 o x HV = √ 19,6 x H (metric)B. Kinetic Energy of Free Falling Weight: E T =Total energy per cycle (in-lbs./c)(Nm/c), E K + E W F T P =E K = W x H E C=Total energy to be absorbed perhour (in-lbs./hr)(Nm/hr)E S x .85 T For PRO and PM Series only, useF 6.Deceleration and G Load A. To Determine Approximate G Load with aGiven StrokeG =F W =Work or drive energy (in-lbs.)(Nm)F T I D =Propelling force (lbs.)(N)F =Mass moment of inertia (in-lbs./sec P =E S x .50 =Shock force (lbs.)(N)H=Height (in.)(m)
Hp=Motor rating (hp)(kw) P - F D P G =F P - F D (metric)Wkg x 9,81B. To Determine the Approximate Stroke witha Given G Load (Conventional DampingOnly)S =E 2.To Determine Impact Velocity A. If there is no acceleration (V is constant)(e.g., load being pushed by hydraulic cylinder or motor driven.) B. If there is acceleration. (e.g., load being pushed by air cylinder) V=DtV= 2 )(Kgm 2 )K=Radius of gyration (in.)(m)
L=Length (in.)(m)
P=Operating pressure (psi)(bar)
R K 2 x Dt GW .85 - .15 F D S = Mounting distance from pivot point (in.)(m) 3.To Determine Propelling ForceGenerated by Electric motor *For PRO/PM and TK Models:
S=Stroke of shock absorber (in.)(m)
t=Time (sec.)
T=Torque (in-lbs.)(Nm)
V=Impact velocity (in./sec.)(m/s)
W=Weight (lbs.)(Kg) S =E K GW .5 - .5 F D F NOTE: Constants are printed in bold .
D = 19,800 x HpF D = 3 000 x KwVV (metric) The following examples are shown using Imperial formulas and units of measure.
EXAMPLE 1: Vertical Free Falling Weight STEP 3: Calculate work energy STEP 5: Calculate total energy per hour E (W) Weight=3,400 lbs.
(H) Height=20 in.
(C) Cycles/Hr=2 STEP 2: Calculate kinetic energy E =W x SE E
W W =3,400 x 6 E
T C=E
T x CE
W =20,400 in-lbs.
T C=88,400 x 2E C=176,800 in-lbs./hr STEP 4: Calculate total energy per cycle E
T K =W x H E STEP 6: Calculate impact velocityand confirm selection
K =3,400 x 20 = 68,000 in-lbs. Assume Model OEM 4.0M x 6 isadequate (Page 31).
T =E
K + E
W E
T =68,000 + 20,400 E
T =88,400 in-lbs./c V= √ 772
o x HV= √ 772
o x 20V=124 in./sec.Model OEM 4.0M x 6 is adequate. EXAMPLE 2: Vertical Moving Load withPropelling Force Downward
STEP 1: Application Data STEP 2: Calculate kinetic energy STEP 1: Application Data E STEP 3: Calculate work energy STEP 5: Calculate total energy per hour E (W) Weight=3,400 lbs.
(V) Velocity=80 in./sec.
(d) Cylinder bore dia.=4 in.
(P) Pressure=70 psi
(C) Cycles/Hr=200 F
2 D =[ .7854 x d
2 x P] + W F
D =[ .7854 x 4 x 70] + 3,400 F
T C = E
T x C E
D =4,280 lbs.E
T C = 45,307 x 200 E
W =F
D x SE
T C = 9,061,400 in-lbs./hr Model OEM 4.0M x 4 is adequate.
W =4,280 x 4 E
W =17,120 in-lbs. W W W
2 2 STEP 4: Calculate total energy per cycle E
K = 772772 x V =3,400x 80 E
K =28,187 in-lbs.Assume Model OEM 4.0M x 4 isadequate (Page 31).
T =E
K + E
W E
T =28,187 + 17,120 E
T =45,307 in-lbs./c
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