Artillery Trailers

[Rob Beale]

The No. 7 trailer may be used as either the carriage trailer or as the front vehicle of the section ammunition trailers. It is used by units for mechanised draught having rubber-tyred wheels (as with the Mark IIR carriage) and has fittings for a No. 17 engine draught connector.
The ammunition box is constructed of steel plates rivetted together...carries 38 rounds.

No pic available

[Rob Beale]

The No. 8 trailer may be used either as the carriage trailer or as the front vehicle of the section ammunition trailers. It is used for mechanised draught having steel tyres and fittings for a No. 21 engine draught connector.
The ammunition box is as for the No. 7 trailer, constructed of steel plates rivetted together...carries 38 rounds

No pic available

[Rob Beale]

The No. 9 trailer is used as the rear ammunition trailer for horse draught having steel-tyred wheels.
The ammunition box is as for the No. 10 trailer, with steel doors and shield... carries 38 rounds.

[Rob Beale]

The No. 10 trailer is used as the rear vehicle of the section ammunition trailers. It is provided with rubber-tyred wheels for use with mechanised draught.
The ammunition box has steel doors and shield... carries 38 rounds.

no pic available

[Rob Beale]

The No. 4A trailer differs from the No. 4 in being fitted with draught joints in lieu of hooks, to take a No. 21 engine draught connector for mechanised draught.
(It is restricted for use with the Mark I carriage.

no pic available

[Rob Beale]

The No. 29 trailer differs from the No. 7 in being fitted with pneumatic-tyred wheels on drop hubs and is for use with the Mark IIPA carriage.
The ammunition box is as for the No. 7 trailer, constructed of steel plates rivetted together...carries 38 rounds.

Drop hub diagram shown, is to fit the end of the original axle, and lower the wheel centre for the smaller radius steel disk wheels and pneumatic tyres.
Low pressure tyres, 7.50" by 24" are fitted. Note I am not sure if this is the dia of the rim as used in WW2 and later, or the old system of outside dia of the tyre. Remember tyres then had a 100% profile where the width was the same as the height so the tube was effectively circular inside the tyre.

The manual also shows the No. 27 trailer was used for the 18 pdr.

[Rob Beale]

Wheels were developed from wooden spokes and rims with steel tyres for horse draught to rubber tyres on thes wheels for mechanised draught.
(I assume this was traction engines and the like).
Final change was to pneumatic tyres for draught by motor vehicles like gun tractors.

Speed Limits:

Pneumatic Tyres: 20 mph on good roads, 10 mph on indifferent roads

Rubber-tyred or padded wheels and unsprung: 15 mph good roads, 10 mph indifferent roads

Wooden wheels steel tyred 8 mph (no mention of road type!)

The WW1 equipment described in the threads above used the No 45 2nd class C wheel which had 6 pairs of spokes and a 6 part rim (felloes) of 56 ' diameter. The pic shows a cross section of the wheel. Spokes are oak and felloes are ash