Stepladder

[Nick Maclaren]

Unless the ground is absolutely level, it will lean, and THAT is the form of instability it is twice as prone to (relative to its base dimensions) as a tetrapod ladder. Even a slight lean is a worse danger than most people realise, because it will put extra weight onto the downhill legs and, if the ground is not absolutely solid, that will cause the ladder to lean further as the user climbs it. Quite often suddenly and unexpectedly.

If tripods did not have a serious disadvantage over tetrapods, they would have replaced the latter millennia ago, because they are simpler to make, lighter and (as you say) easier to position.

Regards, Nick Maclaren.

[Tim Watts]

Not entirely - they are less suitable for building work. With a tree or a hedge, you can get the 3rd leg around the tree or through the hedge.

With a building, you can't and that puts the top, which is not as wide as the 2 step bearing legs, well away from where you want to be.

I don't think it is a simple as "one is better". They are made for different purposes and each suits its purpose better than the other, mostly (there are always exceptions).

Cheers, Tim

[Nick Maclaren]

I didn't say they were useless - I said that they are NOT more stable than tetrapods (as was originally claimed) and, in fact, are less stable. Yes, you can fix that by increasing the base by about a factor of two but, as you point out, that means they cannot be used straight ahead and must be used diagonally sideways (or straight up). I should be surprised if the tripod ladder in the link was enough larger in all dimensions to achieve the same stability as the 10' ladder I have - yes, the width is ample, but what is the length from the steps to the single leg, and how far is the step from the single leg (in a horizontal direction)? With those figures, I could easily calculate the relative stabilities.

Returning to what you responded to - being unsuitable for many (most?) of the uses that stepladders are used for surely counts as a serious disadvantage?

Overall, my advice to the non-expert is "watch out, and remember that it is as important to ensure the ladder is upright as it is for a tertrapod."

Regards, Nick Maclaren.

[Chris J Dixon]

Which is?

The web site fills in some of those figures. The 3 m ladder has a base width of 1.45 m and the spread to the back leg is 1.93 m.

Chris

[Nick Maclaren]

Youngman's industrial 3m.

Mine is 62cm and 191cm. If I assume the angles are the same, mine has a 10% longer distance to the nearest imbalance point. But, equally importantly, it maintains its stability when on the top and reaching forward to work. That is a very big deal, because it is the recommended way to use a stepladder and means that it can really be used as a 10' ladder, not as an 8' one with a 2' extension.

Regards, Nick Maclaren.

[Nick Maclaren]

I should have given some numbers. Mine loses essentially no sideways stability, no matter how far you lean forward - though, if you move the CoG more than 72cm forward (a LOT), you will fall flat on your face. The tripod starts at 91% of mine, and loses c. 10% for every

8cm you move the CoG forward; even holding your hands out with a heavy implement makes a significant difference, let alone leaning.

Regards, Nick Maclaren.

[Vir Campestris]

What a quadruped ladder will do which a tripod will not is to flop between two stable states. On rough ground with one foot slightly off the ground these states are scarily close to normal use - it will often move from one to the other as you climb up. Even if it doesn't go over this is disconcerting. And as it moves, and you gain momentum it's quite possible it will go past the other stable state and fall over.

You can get around this by chocking one of the feet every time you move it. If you are doing a lot of work outside - for example, picking fruit in an orchard - this is time consuming.

A tripod ladder intended for use in such an environment can afford to have a wider base which would be impractical in a ladder intended for use indoors.

Andy

[Chris J Dixon]

Thanks, that is an interesting option. I have a heavy old wooden ladder extension ladder that is seldom used, and a real pain to get out of its place in the roof of my garage. If I went for a 3 section aluminium combination, something like:

together with stabilisers like you have, assembling a bit like:

it might well be more versatile (and possibly safer) than the big tripod, and be much easier to store.

Chris

[Chris J Dixon]

To complete the story, after looking at lots of data, I eventually chose the Zarges Skymaster Trade Ladder 3-Part 3 x 7 Rungs:

Together with their safety legs:

I was able to negotiate a good deal too.

It seems to be very sturdy, and (importantly for one who doesn't really relish heights) feels remarkably stable. It is small enough to fit in the garage, and be used on indoor jobs, yet should reach anything outdoors that I ought to be tackling.

Chris