Measuring internal dimensions

[GMM]

Normally a little bit of error on an internal dimension doesn't really matter but it'll be important on this job. Both 'ends' are buried (so it's not possible to read the scale of a tape) and one end is at an angle (so a small deviation will provide a significant error), so it's important to measure just the right spot. One trick I've used before (and may use here) is two gardening canes and a rubber band: Wrap the band around both, then slide them apart to meet the target, then let the rubber band hold them in position as the whole thing is withdrawn and measure the overall length (if that makes sense!). It occurred to me though that someone here may have a better solution for this.

[Peter Taylor]

The idea of two canes is great, it's a similar idea to the way to make a template with overlapping hardboard panels. But the ends need to be pointed so there's only one point of contact.

Not sure about the rubber band though, which could move out of position. Why not simply make a pencil mark across both canes, so you can measure from the end on each one and then add the dimensions together?

[Andrew Mawson]

What you are describing is a crude form of Gunter Rule - which is two lath shaped pieces of (usually) boxwood, each with a longitudinal slot through which passes a bolt and thumb screw. The Royal Navy uses a large version when making emergency shoring up repairs to war damage on board. The Gunter Rule is used in the holed compartment (usually dark and pretty full of water!) to measure the length of shoring timbers. The rule can be passed though a small hole to other compartments where the timber is cut to size.

Andrew

[Mike Barnes]

I'm not sure about exactly what it is you're measuring, but you could use two tape measures (one from each end), read them at any convenient point where they cross, and add the readings. Or it might be more convenient to make one of them a rigid rule.

[GMM]

I don't know if I've seen one of those or it was just the product of a fevered imagination but that is pretty much what I had in mind. It's particularly good to be able to put a name to it: That way it sounds like I've built a pro tool rather than a bodge from a few scraps of wood and some nuts and bolts ;)

Since the range of measurements I need to make will range from ~20cm to around 65cm, I'll probably have to knock up more than one (or an extension piece to make the mid section).

[Rick Hughes]

seen window companies using a telescopic version to do same thing when measuring for windows.

[djc]

Laser measure?

[The Medway Handyman]

Advent 2in1 Gap Tape

Bloody brilliant!

[The Medway Handyman]

How clever is that!

[Ian Guest]

djc is correct in suggesting that a laser measure should be utilised.

Laser to measure A laser measure, measures uses a laser to take a measurement so removing the requirement for a physical contact between the two measuring points. If you can see the place you would like to measure too, then you can measure to it.

Accuracy Accuracy is improved over a tape measure and especially a cane. Leica Geosystems have developed instruments with accuracies of 1mm over distances of 200 meters.

Time Saving Forget using a tape measure anyway, you need two people to take a measurement, one to hold the tape and the other to place the end. As shown in previous conversations, where you cannot actually get to a point you have to improvise so reducing the accuracy of the measurement.

So with a laser measure, one person can measure a house, office, warehouse and even a construction site in a fraction of the time. Commonly a quarter of the time with a vastly improved accuracy.

Leica Geosystems manufacturer a range called Leica Disto starting at just ?99. So checkout their range at 'Leica DISTO laser measures | Survey Express Services | Surveying & Safety Equipment Specialists'

A good source of measuring and testing equipment is Survey Express Services 'Survey Express Services | Surveying & Safety Equipment Specialists'

they have over 40 years experience and office throughout the UK. Plus a little arm twisting and you can get a discount!!!

Hope this helps Ian Guest

[fred]

Make your own.

Unfortunately I've found them to be very fragile