A prototype 'Air-Van'. This is based on a Commer 'walk-through' chassis with a power take-of driven air compressor.
Development of New Rodding Equipment
It should be noted that all new ducts will have a draw-rope which has been inserted by the contractor. The draw-rope is highly resistant to conditions in the duct and should remain usable for many years, and will have a breaking strain of 1200 lb. Each new cable will have a draw-rope drawn-in with the cable, if there is space in the duct for any further cable. This will mean that a better type of swivel is required since the present one does not operate well on small loads. There is a new type of swivel on field trial at present. (See also article on Connectors Swivel in this Issue.)
The ductmotor causes less damage than any other device, and a good supply is available.
(b) The use of cane rods has been superseded by PVC which is much better to handle – has lower friction in the duct but is still subject to a PVC phenomenon, known as 'cold shatter' at low temperature. The PVC rods (Rods Duct Nos. 1 and 2) are being supplied in 9 ft. lengths for rodding parties and 6ft. lengths for jointers and can be carried in 15 cwt. vehicles.
It is possible to extrude PVC in long lengths and six hundred lengths of 200 yards on the new type of reel are on order, for use instead of steel. These reels must be mounted in the vehicle. The PVC rod has a hollow section and can be used to carry a water jet or air, under pressure, for silt clearance.
The PVC rod can be used in a space of just over 1 in. diameter, and the development of a machine to push the continuous PVC rod is in hand.
(c) Continuous Steel Rods. The b in. diameter steel rod can be pushed by hand or by machine.
Proposed Equipment Arrangements
Where the vehicle cannot park at or near enough to the box (at either end) the party will use 9 ft. PVC rods by hand. (Two men can push 180 yards with these rods.)
A recommended fitting layout for 30 cwt. and 2 ton Utility vehicles has been issued by OP Branch.
To avoid damage risk to existing cables, particularly coaxial, the ductmotor will be tried wherever there is a 2 in. space available. To make the best use of the equipment each 2-man rodding team will be issued with four ductmotors -two with large bags and two with small - so that by setting up at one box the duct route can be rodded forwards and backwards at the same time. Provision of ductmotors allows for this and the 15 cu. ft. compressor provides sufficient air. If there is insufficient duct space for operating the ductmotor then a continuous rod will be used.
The 5/16 in. diameter steel continuous rod can generally be pushed only about
135 yards and then must be carried from the other end. The PVC continuous
rod and the PVC 9 ft. rods can often be pushed 180 yards depending on the state
of the duct.
Whilst these devices can individually be driven by other motive power, air power is convenient. It is possible to get this air-power from a new type of compressor mounted under the vehicle floor and driven from the vehicle engine, and this is commercially available at a reasonable price.
This concept is considered to be the specialist duct-rodding vehicle of the future and a prototype is being fitted out. The savings achieved would be:
Last revised: February 06, 2021