Feb 022015
 





Tire size calculator

The results of this calculator are based on the mathematical equations of the sizes
entered, not the actual tire specs provided by the tire manufacturers. Please refer to the guides
supplied by manufacturers for exact specifications.Results within +3% of stock are considered acceptable.

Input

Please enter actual Tread width – Aspect Ratio and Wheel / Rim diameter
(e.g. 205/65-R16)

Original Alternate
 /  –   /  – 

Results
Graph
Graph: Actual speed vs. speedometer reading (km/h)
 
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More about tires

Tire sizes are expressed by the manufacturers with three sets of numbers:

Tread width – Aspect Ratio – Wheel diameter (e.g. 215 55 R16)
Automobile tires are described by an alphanumeric tire code (in American English)
or tyre code (in British English, Australian English and others), which is
generally molded into the sidewall of the tire. This code specifies the
dimensions of the tire, and some of its key limitations,
such as load-bearing ability, and maximum speed.
Sometimes the inner sidewall contains information not
included on the outer sidewall, and vice versa.
For more in dept information about tire size and tyre codes see Wikipedia


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Apr 202012
 



infoFormula used in this
calculation is from the famous Wheelers approximations
which is accurate to <1% if the cross section is near
square shaped.

L (uH) =31.6*N^2* r1^2 / 6*r1+ 9*L + 10*(r2-r1)

where…

  • L(uH)= Inductance in microHenries
  • N = Total Number of turns
  • r1 = Radius of the inside of the coil in meters
  • r2 = Radius of the outside of the coil in meters
  • L = Length of the coil in meters
Multilayer air cor inductors

NOTEThis formula applies at ‘low’ frequencies (<3MHz) using
enameled copper wire tightly wound.

Multilayer air coils Please note that the diameter is measured from center of wire trough
center of the coil and to center of the wire on the opposite side.

Inductance (L):
Coil Inner Diameter (d=2*r1):
Coil Length (l):
Wire Gauge: AWG
Number of Turns (N): turns
Turns per Layer: turns/layer
Number of Layers: layers
Coil Outer Diameter (D):
Wire Diameter:
Wire Length:
DC Resistance (R): Ω (at 20°C)

image

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Apr 192012
 


infoSingle layer air core inductor calculator.
Winding the wire in a single layer produces an inductor with minimal parasitic capacitance, and hence gives the highest possible self-resonant frequency (SRF). Striving to obtain a high SRF and low losses is the key to producing coils which have radio-frequency properties bearing some useful resemblance to pure inductance.
The calculation is based on Wheeler’s 1928 formula for a single-layer solenoid which is given in its original form as:
L = a² N² / (9a + 10b) [microHenries] , b > 0.8a
Where b is the coil length in inches, and a is the radius in inches.

To convert this formula to SI units, we will use the symbols r = radius, D = 2r = diameter, l = solenoid length.
Factoring b from the denominator gives:
L = 10-6 a² N² / [ b (10 + 9a/b)] [Henrys] The quantity a/b is dimensionless, and so we can immediately substitute in the denominator:
L = 10-6 a² N² / [ b (10 + 9r/l)] = 10-6 a² N² / [ b (10 + 4.5 D/l)] Factoring 10 from the denominator gives:
L = 10-7 N² ( a² / b ) / (1 + 0.45 D/l) [Henrys]


where..

  • L is the inductance in Henry
  • D is the coil diameter in meters
  • r is the radius in meters (or D/2)
  • l is the lenght of the coil in meters
  • N is the number of turns
Please note that the accuracy of this formula is ±0.33% if the ratio of D/l>0.4. so this formula fits best for long solenoids.

noteThis formula applies at ‘low’ frequencies (<3MHz) using enameled copper wire (magnet wire) close wound.

Tip 1Small reductions in the inductance obtained can be achieved by pulling the turns apart slightly. This will also reduce self-resonance. Other combinations of wire and coil diameter may be tried but best results are usually obtained when the length of the coil is the same as its diameter.

Tip 2 If you need good induction stability in the presence of vibration then wind the coil on a support made from a suitable non magnetic plastic or ceramic former and lock the windings using epoxy glue or other suitable adhesive.

Please note that the diameter is measured from center of wire trough
center of the coil and to center of the wire on the opposite side.

Dimensions

Required Inductance (L):
Coil Diameter (D):
Wire Diameter (d):
Calculate
Coil Length (l):
Number of Turns (N):

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Apr 182012
 


Info This is an popular coil geometri used in todays wireless charger circuits.
The formula used in this calculation is based on the
Harold A. Wheeler approximations
for air core flat spiral coil inductor.

…where:

  • L = inductance in μH
  • Di = inner diameter in inches.
  • s = distance between windings in inches
  • w = wire diameter in inches
  • N = number of turns

1 inch = 0,0254m=2,54cm = 25,4mm.
This formula applies at ‘low’ frequencies (<30MHz)
using enameled copper wire. Some people call it "magnet
wire".

Click on image to enlarge

Flat spiral coil inductor example

Please note that the outer and inner diameter is measured from the center of the wire.
Flat spiral coil dimensions drawing

Dimensions

Coil inner diameter (Di):
Number of turns (N):
Wire Diameter (w):
Spacing between turns (s):
Inductance (L):
Outer diameter (Do):
Wire lenght (Wl):
      

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More about spiral inductors..

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Apr 172012
 


Push image to enlarge
Square planar spiral coil Hexagon spiral coil inductor Octagon spiral coil inductor Sircular spiral coil inductor
InfoThe first approximation is based on a modification of an expression developed by Wheeler; the second is derived from electromagnetic principles by approximating the sides of the spirals as current-sheets; and the third is a monomial expression derived from fitting to a large database of inductors (and the exact inductance values).
All three expressions are accurate, with typical errors of 2 – 3%, and very simple, and are therefore excellent candidates for use in design and synthesis. The thickness of the inductor has only a very small effect on inductance and will therefore be ignored.
Notes:
Fill in appropriate values in the white fields.Then push “calculate”.
1μm =0.001mm
1μm =0.00003937007874015748 inch
Number of turns (n): turns
Spacing between turns (s): μm
Turn width (w): μm
Outer Diameter (dout): μm
Calculated Inner diameter (Din) μm
Fill factor p=(Dout-Din)/(Dout+Din)
  Square Hexagonal Octagonal Circular
Modified Wheeler nH nH nH nH
Current Sheet nH nH nH nH
Monomial Fit nH nH nH nH

 

Reference:
S.S. Mohan, M. Hershenson, S.P. Boyd and T.H. Lee
Simple Accurate Expressions for Planar Spiral Inductances
IEEE Journal of Solid-State Circuits, Oct. 1999, pp. 1419-24.
For multilayer spiral pcb coils see here:
A new calculation for designing multilayer planar spiral inductors

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