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Non Life Sciences
Physics, Astronomy & Cosmology
Ladders
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Ladders
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syhprum
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Re: Ladders
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Reply #20 on:
12/09/2006 19:02:33 »
No not a hook but just a bending of the last 15 CM so that when the ladder is at an angle of 45° to the ground this short section lays flat on the sill, I think that this would introduce less instability than having wheels at the top.
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swalker
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Re: Ladders
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Reply #21 on:
12/09/2006 19:52:58 »
Ok, I see.
The wheels are there to make it easier when moving the head. For example; we can leave the head in contact with the wall and change the height and angle by shifting the heel in or out, Only the "135" ladder has wheels, the small ones don't. I imagine that the maths theory doesn't change much if it has wheels or not.
If there was a projection it could catch on something. If the top extension is pulled up it disengages the pawls that hold it up ( this can be a bad thing).
Ladders are definitely far more complicated than they appear at first sight.
Out of interest (and before my time): we used to use a hook ladder that was hung from the window sill - that looks a bit scary. We also used to use a ladder called an "escape" that had big wheels at the heel.
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syhprum
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Re: Ladders
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Reply #22 on:
12/09/2006 20:07:49 »
As you say wheels are probably the best bet, how do you erect a 105 KG ladder? too much for one normal man, do two do it?
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syhprum
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Re: Ladders
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Reply #23 on:
12/09/2006 20:11:12 »
P.S I had a trip up an 'escape' when I was a young lad installing a TV in the canteen of my local fire station, no big deal for me as I was used to installing antennas.
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swalker
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Re: Ladders
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Reply #24 on:
13/09/2006 06:31:08 »
The 135 needs 4 people to pitch it. Quite a team effort - especially with a bit of wind on an uneven site. There are "props" that are hinged levers (about 5 m long) attached to the top of the bottom extension. These are used to help steady the ladder.
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Last Edit: 13/09/2006 06:36:21 by swalker
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