SLHS 4. Narrowboat Acceleration System

More Information

1. 
   

2. See Chris Deuchar: Horse Boating

Background: Accelerating Vehicles Need Help

All vehicles will have a source of power, an engine or motor, that is just powerful enough to overcome friction and keep it coasting at a steady speed. However to get the large mass of the vehicle up to that speed would take a very long time if the engine or motor merely had to to start it off from scratch with it directly connected to the wheels.

In fact the torque (turning force) of an internal combustion engine is very poor at low speed. So, as we are all familiar, it revs up and gears are employed to more closely match the speed of the engine to the rotation of the wheels until the vehicle has been accelerated to the required speed.

The problem is worse the larger the disparity between the size of the vehicle and the power of its engine. For instance trucks can have 24 gears ! Steam locomotives and electric locomotives achieve a similar result but in exceedingly clever other ways*.

● These items have aspects that uniquely contribute to national or world history.

Accelerating Barges Need Help

You will not be surprised then that the early bargemen found exactly the same problem. A 7 ton barge, with a 25 ton load, presented a serious struggle for a single horse to draw. Occasionally two horses had to be employed but that incurred twice the cost of feed, shoeing and tending. And because of slight jostling you may not quite get twice the horsepower -not to mention twice the chances of one going lame especially as they might walk side-by-side or not quite perfectly one in front of the other (we’re straying off topic -Ed).

Therefore there was always going to be a laborious and wearing exit of barge from lock. This slowed the transit of goods right down and meant that the horses needed more rest. In fact this lack of maximum tractive effort as they got older might mean that old nags might be sent to the knacker before their potential canal working life was over.

Frankly canal companies weren’t exactly happy about this either. Their profit came from tolls. They wanted more barges per day to pass through their waterway -slow ones held the line up. Surely there was nothing that could be done ?

Never was the phrase Necessity is the mother of invention more true than during the Industrial Revolution. There had to be a way to get barges moving quickly without adding more horses.

Pulley And Slip Hook

As with so many Victorian solutions the answer was brilliant, cheap, simple and automatic. Two-to-one gearing in either direction was used. A hook was simply mounted on each lock exit and any barge could add a pulley at the front and take the rope that goes from the horse to the barge and put a loop at the end (see diagram below).

Operation

1. 1.As usual before arriving at the lock the horse would be slowed down so that the boat would also slow down and coast into it. Heavy boats were actively slowed down by loosely placing the tow rope round a fixed bollard at the entrance to the lock - if not a tree but 32 tons is a huge amount of pull (Do you ever see saplings at lock entrances ?)
   

2. 2.As the barge entered the lock the horse was guided forward, also in the usual way, but only half the distance forward.
   

3. 3.While the lock took its time to empty/fill the loop in the rope was pulled forward taking up the slack. It was then placed on the forward hook.
   

4. 4.When the water levels equalised, and the gate opened, the horse was encouraged forward in the usual way firstly taking up any slack then actually pulling the barge.
   

5. 5.However the horse only felt half the resistance because of the pulley’s two-to-one Mechanical Advantage.
   

6. 6.With the normal amount of pull afforded by the horse the barge could accelerate twice as quickly.
   

7. 7.Crucially as the barge sped up, and passed the hook, the loop would become unhooked. As it slipped off it would thread it’s way back to the pulley and get caught in a retaining bracket on the barge automatically. Thus the horse was now out of first gear and into second !
   

8. 8.Sometimes a knot was placed a little way from the loop to facilitate early unlooping to smooth out the little jolt that the horse might receive when “changing up”. They thought of everything - after all the horse was their living.
   

9. 9.Thus the horse found it much much easier each time AND the barge had got out of the lock twice as quickly.
   

Later, in the days of steam, this actually remained a problem on hills and so a banker was added at the bottom of the hill to push the heavy train up eg the steepest hill on the Briitish rail network is 1:37 which employed the famous 0-10-0 Lickey Incline Banker.

Canal Lock Pulley System - Plan View.

A barge fitted with a pulley is drawn out at twice normal speed.

A barge leaving the lock.

A rope ready to slip off the hook built into the parapet

It is not known how many locks on the Stratford Canal were fitted with this system nor how many boats utilised it. Perhaps due to corrosion, or perhaps vandalism, not many remain. It is said that there’s a hook at one of the locks in Lapworth.

● Canals With Gears

The Problem

The Solution

To return to Master page click on ‘Canal’ above.

Examples

Blocking Pulleys

Such was the number of barges using the Stratford Canal that in some places there are further pulleys to aid this process.

Capstans

As more canals were constructed their capacity for larger barges was made. The acceleration problem would always remain and so manual, and later powered, capstans, commonplace in the Royal Navy, were installed to facilitate both slowing down, retaining control during lock level changes and ultimate acceleration back up to speed.

A Blocking Pulley at Lapworth.

On the Barnsley Canal

Other Wonders

If you like to see the unusual aspects of canals there are 100’s but the more significant popular ones are listed here:    Wonders Of British Waterways