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Background information on the locks at Llangynidr.

This location is just to the West of the village of Llangynidr approached along the B4558 running from Crickhowell towards Brecon. (Do not try the B4560 from Bwlch if you are driving a minibus as the bridge over the river is alomost too narrow for cars!!).
At 155195 alongside the road you will find free parking on the South side and toilets and a playing field on the North side alongside the Community hall. This is an ideal location to have lunch. (If anyone has forgotten their lunch go down the road towards Bwlch and you will find a very general good stores on the left just before the river bridge.)

For this visit drive from 'lunch' on towards Brecon and then turn North by the bridge alongside the Coach and Horses pub down the 'yellow road'. Park in the layby by the lock at 146200. You can then walk along the canal back past the Coach and Horses pubto reach the visit location at 145198. Here you will find four features:-

Canal Feeder Channel.
Ask the pupils to think about where the water comes from to fill the cannal. On the Brecon and Abergavenny the answer is mainly from rivers. The main source is from the Usk at Brecon. However here in Llangynidir is a minor source.

Cross over the footbridge at the foot of the first lock and you will find the feeder stream, joining the canal at 145198. A very pleasant 300 metre walk through the woods takes you to the feeder weir pictured below. Points to note are:-

The weir which directed water into the feeder channel.
The planks which control the ammount of water admitted.
The side draining sluice halfway between the weir and the cannal under the footpath.
The modern measuring aparatus with a concrete trough close to the canal.

Cannal drain plug to empty water out.
Ask the pupils how they think the water could be removed if repairs are needed. Get them to think how they empty their bath. (At least one will have a mum who empties it with a hose to feed the plants!)
It used to be done by means of huge plugs in the bottom of the canal. This took the form of a trapdoor sealing the top of the drainage channel. The trapdoor was attached to a chain which usually lay on the bottom of the canal. When the drain needed opening the canal man pulled the looses end of the chain onto the bank and attached it to a roller. The use of bars fitted inbto this roller formed a windlass to aply pressure to the chain to open the trap door against the prerssure of water.
Alongside the canal near to the mouth of the feeder channel are the remains of such a trap door removed from the bottom of the canal and put on display. Alongside is the original roller. Both are pictured below.

Canal aqueduct.
Define a canal as a 'level' water channel. Then explore the idea of how canals crossed over valleys. Mention the idea of embankments, to be picked up later at Talybont. Then discuss the idea of a bridge which carries the water over the valley.
At 145198, just before the main flight of locks the canal crosses over the Afon Crawnon by means of a massive aqueduct.

It can be best seen from the main B4558, you can point it out when you drive on this road later. On the oposite side to the towpath there is a path leading downwards, near the start of the feeder channel, which gives a good close view of the aqueduct. (The plastic pipe sticking out of the side is the end of the modern drainage channel.)

The Llangynidr flight of locks.
Get the pupils to understand why a canal channel must be level. (Or else the water flows to fast!) Then get them to think how difficult it is for a boat to climb up a hill. Here at Llangynidir that is just what the boats do.
The basic sequence to operate a lock is: -

First fill or empty the lock, if required, by means of the sluces operated by the padles, till it is at the same level as the stretch of canal your boat is on.
Then open the gates, take your boat in, and then close the gates afterwards.
Now open the sluices to change the water level within the lock.
Finally open the gates to let your boat continue.

It is impossible to open the gates unless the water is at the same level both sides of them. However it is quite possible to leave open the sluices and hence waste water. They must always be clossed after they have been used.
If you are fortunate to see a boat using a lock watch them closely, but not not do anything without asking the people on the boat first. Most people will be delighted to let the children help out if they follow their directions. However remember that: -

a lock being filled or emptied can be a very dangerous place to fall into, so make sure the children do not hang over the edge.
Never, never, stand between the lock beam, that is the long pole attached to the top of the gate and the lock, especially if your pupils are pushing it towards you! Watch that children do not go to both sides of a beam to push and pull it open as them some can end up hanging over the edge!

You are now at the bottom of a series of four locks. It is well worthwhile walking up past all the locks. Look out for: -
- The lock gates themselves.
- The 'paddles' at the top and bottom of each gate where by fitting a windlass the sluices can be opened to adjust the water levels.
- The overflow bypass weir alongside the top gate where surplus water flows past the lock.
- Just below the top lock the side pond to the North of the towpath to compensate for the short distance between the top two locks.
- Stop planks stored on the 'offside' of the top lock which fit into the groves just in front of the top gate to hold back the water if the canal is to be drained.
Look at a pupils' account of a visit to this location.

Look at a pupils' account of making a model lock.

Go on to the background information on Talybont.

Go back to the background information on the limekilns and Llangattock Wharf.

Back to the first page for our Canals Project.

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