Moment of Inertia     

CUTTING EDGE TECHNOLOGY:   MOMENT OF INERTIA (MOI)

The matching of golf clubs …
Is there a better way?

We as golf coaches and players have attempted, through practise, to repeat a swing with the aim of achieving consistency – of impact, of trajectory, of distance control, of direction and of feel.

The theory of achieving a repeating golf swing would appear sound until you realise that the energy required to square up a three iron is a lot higher than the energy required to achieve solid contact with a wedge.

Two old fashioned ‘matched’ clubs – same heads, shafts, grips & swing weight:

3 iron mass – 391 gms – M.O.I  = 2840 kgs/cm2

9 iron mass – 427 gms – M.O.I  = 2750 kgs/cm2

So the 3 irons resists you by an extra 90 kgs/cm2

Why is it so?

The old static measure of ‘swing weight’ (the club is stationery) is a balance of head weight and shaft length – so yes if you like the old D1 swingweight a telephone pole with enough weight at each end can be made D1. This rather large club would require more energy to swing than a golf club at the same D1 swingweight.

So total weight is also an issue – or is it also the balance point of the club?

Try this - swing your 5 iron – feel the weight – now grip the club head and swing the club – which is easier to swing?

The club swishes through easier when the weight is in the hands – because the balance point of the club is closer to the hands - Moment of Inertia is lower – the club resists rotation less.

Yes, the balance point is further from the hands in a 3 iron and closer to the hands in a wedge.

Do the balance points therefore need to be the same distance from the hands for consistent match? – no:  because the weights vary – a 3 iron may weight 383grams where the wedge may weight 432 grams using the same components.

We need to measure accurately –

  • the Club weight to .5 gram,
  • the length from point of rotation to the balance point,
  •  the period of oscillation in seconds to 4 decimal points

and these values are inserted into the formula to calculate the M.O.I of each club.

Our software will then indicate precisely how much weight needs to be added to the each club to achieve consistent M.O.I across the set.

The MOI match gives us the best consistency and sameness of feel across the set.