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Dr Ian Plummer

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Technical
Hoop Widths

The rules for what widths hoops should be set to are not entirely easy to comprehend. Hopefully the tables below will summarise the information.

Non-Tournament Settings

The 'generic', non-tournament, setting for general croquet is given as the internal width between the hoop uprights (the gape). It should lie between 3 ¾ inches and 4 inches.

3.b HOOPS

  1. SPECIFICATION Each hoop is made of solid metal and consists of two uprights connected by a crown. A hoop must be 12 inches in height above the ground measured to the top of the crown and must be vertical and firmly fixed. The uprights and the crown must have a uniform diameter of 5/8 inch above the ground although minor deviations at the top and bottom are permitted. The inner surfaces of the uprights must be approximately parallel and not less than 3 ¾ inches or more than 4 inches apart (subject to Law 53(b) for tournament and match play). Each hoop on a court must have the same dimensions within a tolerance of 1/32 inch. The crown must be straight and at right angles to the uprights.

Further digging in the Laws book (Appendix 1) reveals these measurements have a tolerance of +/- 1/32"

HOOP CLEARANCE
Non-Tournament Settings

Maximum
Gape

Minimum
Gape

 

Absolute Maximum Gape
including tolerance

Absolute Minimum Gape
including tolerance

Non-tournament

4"

3 ¾"

 

4 1/32"

3 23/32"

Tournament Settings

These settings come from the UK Tournament Regulations (2016). Other countries may have different regulations and hence permitted dimensions.

Regulations for Tournaments 2016
APPENDIX 1 - Hoop Setting, Ball Specification and Inspection Requirements

  • HOOP WIDTH. The clearance is defined as the difference between the distance between the inside edges of the uprights at half-ball height and the maximum diameter of the largest ball to be used on the court. Unless otherwise advertised in the Calendar, or as stated below, hoops must be set such that the clearance is as near as possible to:
  • 1/32" for Championship events (see C2(b)(3))
  • 1/16" for events played under conditions of Advanced Play and events played under mixed conditions
  • 1/8" for handicap and other events

Tolerances on hoop settings are +0% and -50% in each case. The Manager may, in accordance with Regulation M2.C.10, alter the advertised clearance by up to 50% in either direction, provided that this and the reason for it is publicised before play starts that day.

HOOP CLEARANCE
Tournament Settings

Standard clearance

Minimum Standard clearance
(clearance minus 50% tolerance)

 

Maximum clearance
if pre-publicised
(std clearance +50%)

Minimum clearance
if pre- publicised
(std clearance minus 50%)

 

Minimum clearance
if pre-publicised
including tolerance
(minus 50%)

Handicap and other events

1/8"

1/16"

 

3/16"

1/16"

 

1/32"

Advanced Play and events played under mixed conditions

1/16"

1/32"

 

3/32"

1/32"

 

1/64"

Championship events

1/32"

1/64"

 

3/64"

1/64"

 

1/128"

 

Coloured entries mark the maximum and minimum permitted clearances for a hoop to be set to.

 

Comments

Ian Plummer adds:

My opinion is that any setting of less that 1/32" is becoming impractical. There are at least three factors to consider: i). ball maximum and minimum diameters; ii) ball expansion and iii) hoop setting.

The hoops are set to (the maximum diameter of) the biggest ball.

  1. Championship ball specifications state:
    • The maximum and minimum diameters of a ball must not differ by more than 1/32 inch (0.8 mm).
    • The maximum and minimum diameters of balls in a set must not differ by more than 3/64 inch (1.2 mm).

    So one ball in a set can be 3/64" smaller in diameter than the others. If the biggest ball encouters a 1/64" gape then the smallest will encounter a 1/16" gape! The whole geometry is different. The narrower the gape the more marked this difference is.

  2. Unsubstantiated reports suggest that a ball can expand by 1/64" over 20°C. If hoops are set to 1/64" in the cold morning, then once the sun gets up balls will jam and the referee will be out with his bucket to adjust the hoops .

  3. Martin French (personal communication) said that he set hoops to 1/64" before breakfast. He went out after breakfast (hoops untouched) and they had all become larger (guessing the spring of the hoops favoured a wider gape). Soil is not rigid and hoops can move. Most hoops' natural gap is larger than 1/64".

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Updated 21.iv.17
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