Contemplating an Irish Bridge II

The stream when the weir hasn't been tampered with.

Judging from the comments I’ve been receiving, I guess a little more explanation, in the form of illustrations, is needed. The illustration to the left shows, crudely, sort of what the stream looks like when all the boards are in place in the weir. The depth in front of the weir is really probably only about 45cm or so. I’m not at the site right now, so I can’t measure it.

This is what happens when they lower the water level.

When someone wants to go across the stream and it’s looking a bit hazardous, or just annoying, they pull up a plank or two in the weir and lower the water level a little. The water continues to flow, of course, just a little shallower. The flow rate at the crossing is fairly slow as it’s comparatively wide and perhaps deep (I haven’t waded across it because you can walk across the weir). I’m surprised they just haven’t filled it in with something, but I presume rocks and such would make it a bumpy ride on a motorbike. I plan to keep the water at the weir at a fixed height.

This is sort of what I'm contemplating.

This is roughly what I’m contemplating, but it is completely out of proportion and, hopefully, much easier to do in reality. Everything is really much more subtle. I’ll have to confirm, of course, that I can raise the level of the water behind this ford as much as I’d like, but I’m pretty sure I can.

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4 Responses to Contemplating an Irish Bridge II

  1. Bob in Stow says:

    If you can set your penstock elevation lower than any board they are likely to remove, then it will not matter if they remove board(s) and your loss of head pressure will be insignificant.

    • richard says:

      That is very much true. But I’d like to make it a little better for them, and keep them away from the weir. I could easily put in a couple of culverts to make the passing generally dry except for times of heavier flow. Plus I’d like to raise the water level, even just a little bit, upstream. If the situation is now clear, the question is “How do I do it?”

  2. Bob Longridge says:

    Hi Richard, I get it now. Where I come from (Yorkshire) we call them Fords.

    As to your question, if I have got the question right. Put in another wier up sream of your Ford, Irish Bridge whatever, that’s what the diagram is saying to me. Does this make sense?

    • richard says:

      I don’t see why I’d need another weir. The ford is just a weir that starts with an “F.” Two weirs don’t make a right, do they? Anyway, I doubt I’ll get that far by the time you come to visit, so don’t worry too much. I shall, however, probably post a design I’m considering. I wish I’d thought more about it when I was last there, then I could have done more measuring. Even if I never make money there, I’ll be eternally happy just measuring things. . .

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