Bradfield Deck Insulator

Oliver K

Jul 8, 2018
Hello! I have read many times that a "Bradfield Type Deck Insulator" was used on RMS Titanic, after some research i discovered this is a patent type of insulator patented by W.W Bradfield of Marconi Co.

Information i have gathered from various sources:

A Bradfield type Deck Insulator, rated for the 5-kW marine generator set and able to withstand a minimum of 30,000 volts, was used to insulate the aerial from the steel structure of the ship. The insulator was elevated on an approximately 6-foot-high wooden trunk, square in cross-section, to keep it clear of a canvas awning that was part of the design for the roof of the Officers’ Quarters but never utilised during the ship’s short career. In order to protect the Bradfield insulator from the strain of the aerial being pulled by the wind, the lead-ins were firmly attached to a screw eye in the roof of the Officers’ Quarters and electrically isolated by a single strop insulator. Electromagnetic energy was transferred between the aerial and the Bradfield insulator by way of two flexible wires that ran from the terminus of the lead-in wires to the insulator’s shackle head. The brass terminal socket on the lower end of the insulator rod inside the Silent Room secured the wire connection to the Aerial Tuning Inductance as well as to the two plug sockets mounted on the aft bulkhead of the Marconi Room. The plug sockets were located within easy reach of the operator so that he could switch the aerial from the earth arrester to the induction coil in the emergency set.



"Aerial Lead-in.—This is a 1/2 in. metal rod in a long ebonite tube, which passes through a cast-iron gland fixed on the roof of the cabin. A zinc cone is fitted to the external end of the rod to ensure that a considerable length of the ebonite will remain dry in all circumstances. A shackle head on the cone takes the strain of the aerial, and prevents the connection being worked loose by the vibration of the aerial wire. Three ebonite discs spaced along the external part of the ebonite tube prevent surface sparking in event of heavy weather causing the insulator to be wet with salt spray. (Fig. 7.)"


The History of Science museum owns a Bradfield insulator and this is their description on it

" Bradfield Leading-In Insulator No.1, for marine 5kW aerial lead-in, with iron rain cone, deck mounting plate, three anti-spark discs and ebonite rod, on iron stand for display."

There are also pictures of it that can be found




Now i have a few questions about this insulator, 1 - In the last image, why is the aerial wire such a thin gauge? surely that wire would burn up if the power was sent through it from the transmitter.

2 - Does the wire run through the ebonite rod or does the ebonite rod itself act as the wire therefor leading-in to the silent with a wire coming out at the bottom?

3 - Did it pose a hazard during the sinking? was the lead-in caulked? or did water drip through it during the sinking? it would have happened after Jack Philips and Harold Bride left the room, but was there any sign of water affecting the transmitter or receiver?

4 - The rod got bent by about 90 degrees when the ship broke, do you think this would have sent an iron cone flying across the deck into the water? was there an unlucky passenger who was hit by a rain cone? same with the aerial, did that hit anyone when it snapped?

I'd love to hear a thoughtful discussion on this, aswell as more information on this insulator, i can assume they are pretty rare nowadays as they were insulators and treated as such, many of them likely ended up in a junk-pile of old ship parts after ships using wireless got scrapped, or they failed and ended up being replaced.
Nov 14, 2005
"Now i have a few questions about this insulator, 1 - In the last image, why is the aerial wire such a thin gauge? surely that wire would burn up if the power was sent through it from the transmitter."
It didn't need to be a heavy gauge wire. Wire is sized for current not voltage. The output of the secondary side of the transformer that charged the condersers was around 10,000 volts. So at 5KW which is 5000 watts the current would only be around a half an amp give or take a little. Think of it this way. A spark plug wire in your car runs anywhere from 20,000 to 30,000 volts. But the current is very small...hence the small wires. Most of what you see is insulatation. The wire itself is actually pretty small inside. Being an open air aerial there wasn't a need to insulate the wire itself. It just needed to be isolated from the structure of the ship.

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