Sunday, 13 January 2013

Couplers & Buffers

Upon entering the world of 7 mm NSWGR the first question asked was  - " What standard are used for couplers and buffer heights? "  

The answer was at this time none are defined but check the prototype...! 

So after examination of all the kits in stock the Waratah S truck would be the worst to modify the coupler pocket but was close to prototype standards. This was chosen as the basis of the standard to be applied to this project.

Construction of a Waratah RU - Bergs LCH - Aust-O BCH proved that all need some or a lot of modification to match the "S Wagon Standard " but it stood the test.

With the problems of buffer height and coupler centres resolved selection of a coupler was the next consideration. After reviewing the current lost wax couplers and the Kadee none met the necessary criteria of operation or appearance.

Wagons coupled

It was decided to use an undersized couplers from San Juan Car Company for a number of reasons. Firstly they can be made to operate with a HO Rix magnetic un-coupler thought this is a work in progress. Secondly the head size was more acceptable and the trip pins [air hoses] are not as low as the Kadee placing them in a more prototypical location.
These couplers have some special requirements for mounting and the plastic whiskers are a concern as they are not a proven solution and will be reported on here much later..!

Couplers and Buffer Lock.

This was a common problem in the operation of NSWGR O scale wagons and justified an effort to define a suitable settings for this project.

It was decided that a fixed relationship on the rolling stock would be required for the buffers and couplers with a minimum operating radius. The datum for both is the buffer mounting face on any piece of rolling stock.

  • Buffer length - 9.5 mm tolerance + 0.1 / - 0.2 mm overall. 
  • Coupler to inside face knuckle 10.0 mm tolerance +0.25 / - 0.0 mm or 11.75mm to the face San Juan coupler
  • Minimum radius 1650 mm




This allows coupling on a 1650 mm radius curve [minimum] and the cars to operate correctly with no apparent buffer or coupler lock when fitted in the standard manufacturer coupler boxes.

Four wheel wagons on 1650 radius curved point

The standard developed may have to adjusted but so far it has allowed the equipment to work correctly and will be continued to be used as described unless a unforeseen problem is encountered. 

If fine tuning or scraping is required in the future it will be noted on this page...!.

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