Guthrie's Lifting Bridge

 

This unique lifting bridge was invented by a Mr. Guthrie as a means of protecting the entrance to a fortification. The bridge was lifted and rolled into the fort during times of danger, so that no portion of the bridge was accessible to an enemy. It could be rolled out and dropped minto place to span the drop ditch in front of the gateway. The gates to the fort could be closed with the bridge in either the run-out or run-in position. To assist with running the bridge out and in a large pair of heavy counterweight arms balanced the bridge so that a small force was required to start the bridge on its lifting motion. One drawing of this bridge can be found in a military manual entitled "Permanent Fortification for Military engineers" by Colonel Lewis, published in 1889. This shows one man operating the bridge but evidence in a military report concerning a bridge on the Portsdown Hill line points to problems with these bridges when they were left in the out position for a great length of time. It explains that it took 40 men a day to shift the bridge and run it in! Instructions for operating the bridge at Fort Pembroke, Malta state that not more than six men were to be employed to work these bridges.

 

Guthrie Bridge Fort Pembroke

Guthrie Drawbridges : Instructions for working
5. Not more than 6 men are to be employed to work these bridges, and it is essential that there should be no jerking or violence.
6. To draw in the bridge fix the tackle to the ring bolt in the roadway, take in the slack of the rope, and put 4
men on the fall.
7 Remove the stopper at end of bridge with the special lever provided.
8. The 4 men on the tackle will pull steadily, and if the bridge does not come in at once, the other 2 men will slightly lift the end of the bridge with handspikes, applied under the end of handrail on each side. A steady pull must be kept on the
tackle the whole time and care must be taken only to lift the bridge, just enough to start it.
9. In Running the bridge out, great care must be taken to do it slowly and carefully, 2 men will weigh down on the special lever the end of which will be put through the ring on bridge. The other 4 men will be placed 2 on each side of the lever
bearing down with the flat of their hands on the floor of the bridge and pushing it gently along. The 2 men at the lever will see that the bridge is running straight, as otherwise it
may not engage both the supports at the same time.
10. As soon as the bridge is in its place, the stopper will be replaced in its hole, and kept there until the bridge
is again drawn in.
11. The lever should be kept in the guard room.
12. Officers in charge of parties working these bridges will be careful to see that these orders are attended to. Accidents to these bridges occur most frequently when too many men are employed and when the bridge is drawn in, or pushed out,
too quickly.

A drawing of the Guthrie Bridge at Fort Pembroke, Malta showing the lifting arms and bracing struts.

 

 

Nelson Guthrie bridge
Nelson Guthrie Bridge
 

The Lifting arms of the Fort Nelson Guthrie Bridge

Section
The Verne Lifting bridge

The Fort Nelson Guthrie Bridge

The remains of the Guthrie bridge at The Verne Citadel, Portland

 

Guthrie drawbridges are known to have been fitted at the following forts:
Forts Nelson, Wallington, Widley, Purbrook, Southwick, all at Portsmouth;

Fort Pembroke, Rinella and Cambridge Batteries at Malta;

The Verne Citadel at Portland.

 

There are no examples of a complete bridge remaining but some portions remain at The Verne and some of the Portsdown Hill forts.

Fort Rinella, Malta has been restoring and renovating its Guthrie bridge in order to produce a fully working example.

Click on the drawings below to enlarge.

 

Guthrie bridge: Plan and side view.

Guthrie bridge: Top plan with wood portions.

Guthrie bridge: Bridge in the 'out' position.

Plan and side elevation

Top plan with wood portions

Bridge in the 'out' position

Guthrie bridge: Bridge at the initial lift position.

Guthrie bridge: Bridge running in.

Guthrie bridge: Bridge fully run in.

Bridge at point of initial lift

Bridge running in

Bridge fully run in

 

 

 

 

 

Download a fact sheet showing the sequence of lifting a Guthrie Bridge pdf