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Dr Ian Plummer

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Technical
Hoop Specifications

The properties of hoops are listed in a number of places and this document attempts to bring the specifications together.

  1. For General Play
  2. For Tournament Play
  3. For Croquet Association Approval
  4. Related Material

A). For General Play

Firstly the Laws define the basic dimensions of a hoop:

Law 3

  1. 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.
    2. COLOURS The hoops may be left unpainted or coloured white and, in addition, the crown of the first hoop (hoop 1) is coloured blue and that of the last hoop (rover) is coloured red.

Secondly Appendix 1 of the Laws adds tolerance values:

Law

Subject

Imperial Units

Tolerance

Metric Equivalents

Tolerance

 

 

 

 

 

 

3(b)

Hoops

12 inches

+/- ½  inch

300 mm.

+/- 12.5 mm.

 

 

4 inches

+/- 1/32 inch

100 mm.

+/- 0.8 mm.

 

 

3 3/4 inches

+/- 1/32 inch

95 mm.

+/- 0.8 mm.

 

 

5/8 inch

+/- 1/8 inch

16 mm.

+/- 3 mm.

Croquet Hoop
Standard Croquet Hoop - next to 12" Rule.

Material: cast iron. Weight: 5 lb 10.5 oz (2.57Kg). Carrot length: 8". Carrot max diameter: 1-3/8". Upright diameter: 5/8". Crown diameter: 5/8". Height top of carrot to underside of crown: 12". Internal gape of hoop: 3-11/16". The centre of mass of this hoop lies 1.5" above the top of the carrots.

The Official Rulings on the Laws of Croquet (ORLC) adds the following to aid interpretation of the above:

3.2 The hoops (Law 3(b))

3.2.1 Note the reference in Law 3(b)(1) to Law 53(b) for tournament and match play to permit the use of hoops narrower than 3¾ inches.
3.2.2 Note the tolerance of +/- 1/2 inch in the height of the hoop, which is to allow hoops to be firmed up by knocking them into the ground as a tournament proceeds.  However, a player is entitled to expect that hoops will be set so that their carrots do not protrude significantly above the ground, as otherwise they would not comply with the requirements for the uprights in Law 3(b)(1).

B). For Tournament Play

As the following is part of the Laws it applies world-wide.

Law 53

  1. HOOP DIMENSIONS
    1. The hoops shall be set according to the conditions advertised for the event. Hoops with larger uprights and crowns may also be specified.

Within the domain of the Croquet Association (UK governing body) the following is defined in the Tournament Regulations:

APPENDIX 1 - Hoop Setting, Ball Specification and Inspection Requirements

  1. ACCEPTANCE STANDARDS
    1. 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 Fixtures Calendar, or as stated below, hoops must be set such that the clearance is as near as possible equal to, but not less than, 1/16" for Championship and other events played under conditions of Advanced Play, and 1/8" for other, including mixed, events, with an upward tolerance of 50%. The Manager may, in accordance with M2.C.10, alter the advertised clearance by up to 50% in steps of 1/32" in either direction, provided that this and the reason for it is publicised before play starts that day.
    2. HOOP RIGIDITY. Hoops must be set firmly and securely such that no perceptible movement occurs when the crown is pushed/pulled with considerable force.

C). For Croquet Association Approval

The following text lays out the characteristics for hoops requiring CA approval. CA approval is only appropriate for the CA's domain

Approved Croquet Hoops - Specification

1 Hoops

In order to provide security for clubs considering the purchase of new types of hoops, a scheme for CA Approval has been initiated (December 2000). Approved hoops are recognised for use in CA Tournaments and Championships, but the use of Approved hoops is not a requirement in such events.
Standard Approval may be given to hoops of unstressed upright separation 3 11/16 inches to 3 13/16 inches, and both Championship and Standard Approvals to those with separation in the range 3 11/16 inches to 3 3/4 inches. The Championship range provides for a 1/16 inch clearance on all Championship Approved balls and the different upper limit of the Standard range accommodates a 1/8 inch clearance. By stressing the hoops in the ground it is expected that most designs will produce both 1/16 inch and 1/8 inch settings at ball half-height; the rules for Approval also aim to cover hoops of fixed width such as may be more suitable for use with artificial surfaces.

The requirements in Section 2(c) were revised in 2004 to permit greater upright diameters for cast iron hoops. Cast iron hoops have traditionally had more substantial uprights and a greater diameter eases problems in the casting process. The hoop crown has traditionally had a greater diameter than the uprights, so despite the requirement in the Laws of Association Croquet (2000) for a 5/8" diameter with an upward tolerance of 1/32 inch (total 21/32 inch), Approval is available to hoops with a crown diameter up to 13/16 inch.

Hoops with Approval

Hoops that have current Approval are as follows: Omega Adjustable Hoop (Steel; Standard and Championship Approval, December 2000) Jaques Championship Hoop (Cast Iron; Standard and Championship Approval, July 2005).

Manufacturers seeking Approval are required to submit one (non-returnable) fully finished hoop for testing, to arrange a Field Test at an agreed venue and for an agreed period, and to provide written assurance that the manufacturing processes are adequately reproducible. The Equipment Committee will be responsible for preparing a report of performance in relation to the stated criteria and will provide a check list of items for the Field Test. The report will include a general description of the hoop system and indicate whether the hoop is suitable for fixed or adjustable setting. Approvals will be announced in an appropriate manner by the CA. A hoop system may be accorded Approval in either or both of the Standard/Championship categories. The report will be made available to the maker and for an Approved hoop it may be published by the CA.

A hoop system for use with artificial surfaces has been developed by Mr R.H. Rawden of the Bury St Edmunds Club (Approved 2003) 2(c) The diameter of each upright....permitted. For cast iron hoops the upper limit is 23/32 inch (18.3 mm). 2(d) Open Square brackets before 'The ranges were derived as follows.' 2(e) The crown......between 19/32 and 13/16 inch (15.1 mm and 20.6 mm)

2 CA Standard and CA Championship Approval of Hoops

Imperial measurements are definitive; metric equivalents are given for convenience. The criteria apply to hoops of fixed setting and to hoops whose setting may be adjusted by stress through the anchorages or otherwise.

Notes of explanation are enclosed in square brackets. The specifications for Approval are derived from the requirements for clearances of 1/8 inch ('handicap setting') or 1/16 inch ('advanced setting¹) with any ball meeting the internationally recognised Championship Approval standard - i.e. diam. 3 19/32 - 3 21/32 inches.

(a) Construction

  • A hoop comprises two vertical uprights joined at the top by a horizontal crown and must be provided with a means of anchorage at the base of the uprights.
  • The uprights and crown should be straight and the anchorage system must not hinder free passage of the ball.
  • The uprights and crown must be constructed of solid metal of adequate hardness and the hoop must be rigid.

(b) Height

  • The hoop must be capable of a setting in which the top of the crown is between 11.5 and 12.5 inches (292 and 317 mm) from the ground.

(c) Upright diameter

  • The diameter of each upright should lie between 19/32 and 21/32 inches (15.1 and 16.7 mm); minor deviations at the top and bottom are permitted.
  • Three measurements are to be made for each upright: high, low and mid length: all diameters must lie within the allowed range. Here and subsequently, high = approx. 13/4 inches from underside of crown; low = approx. 13/4 inches above base of upright.
  • The high and low points avoid minor deviations at the top and bottom of the uprights and approximate respectively to a ball radius from the underside of the crown or the ground (13/4 inches = ideal ball radius minus 1/16 inch).

(d) Uprights parallel

  • The inner surfaces of the uprights must be approximately parallel and of separation between 3 11/16 and 3 13/16 inches (93.7 and 96.8 mm) for Standard Approval or between 3 11/16 and 3 3/4 inches (93.7 and 95.25 mm) for Championship Approval. For a set of hoops the separations must not differ by more than 1/16 inch (1.6 mm).
  • Three measurements of the separation between the inner surfaces of the uprights of an unstressed hoop are to be made at high, low and mid length: all three measurements must be within the allowed range and the difference between the largest and smallest measurement shall not exceed 1/32 inch; for a set of hoops the difference between the largest and smallest of the 18 measurements should not exceed 1/16 inch.

The ranges are derived as follows.

  • Standard Approval:
    3 19/32 (min. ball) + 1/8 (hcp setting) - 1/32 (hoop tolerance) = 3 11/16 inches
    3 21/32 (max. ball) + 1/8 (hcp setting) + 1/32 (hoop tolerance) = 3 13/16 inches
  • Championship Approval:
    3 21/32 (max. ball) + 1/32 (min. clearance) = 3 11/16 inches
    3 21/32 (max. ball) + 1/16 (adv. setting) + 1/32 (hoop tolerance) = 3 3/4 inches]

The uprights between the high and low positions will be tested for coplanarity: when one upright is in contact with a plane surface, no point of the relevant length of the other upright may depart from the plane by more than 1/16 inch.

(e) Crown

  • The crown must be straight, at right angles to the uprights, and have a diameter between 19/32 and 21/32 inch (15.1 and 16.7 mm).
  • Any logo must comply with these limits.

(f) Field Test

  • The hoop must be capable of being set firmly in suitable ground.
  • Evidence of satisfactory performance in setting, durability, and play with Championship Approved balls must be available.
  • A check list will be prepared to ensure that the Field Test has appropriate scope.

D. Related Material

The Effect of Hoop Upright Diameter on the Acceptance Angle of a Hoop

Calculations of the Effect of Varying Hoop Dimensions

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Updated 28.i.16
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