Measuring the Radius of a currently installed shower tray

[omniflow]

Looking for tips.

I need to replace the shower enclosure and I don't really want to install a new tray, so I need to find a like for like replacement. It's a 900x900mm quadrant and it would appear that these are available with different radii, 500mm and 550mm being the most popular.

My investigations so far have concluded that a 900mm tray with a 500mm radius means the straight part is 400mm long before the curve starts and a 900mm tray with a 550mm radius has a straight part that is 350mm long. Therefore it should be quite easy to measure the straight part and then calculate the radius.

However, using some basic maths, it seems that for the first 5 or 10 cm of a curve of that radius, you're talking virtually a straight line. After 5cm it's a gap of 0.25mm and after 10cm it's a gap of 0.76mm for a 50cm radius and 0.23mm and 0.69mm for a 55cm radius. So if I measure at 45 cm I should either find a gap of 0.25mm if it's got a radius of 50cm and 0.69mm if it's got a radius of 55cm. Less than half a mm.

Anyone got any better ideas?

BTW - I've already dismissed the idea of ignoring it and just taking a punt. I use this shower every day, and if I got it wrong it would bug me - every day.

[Simpo Two]

I'm no good at maths so would do it empirically - ie take a piece of string and offer it up and move it back and forth adjusting the pivot point and length until it traces the arc accurately. Then measure the string.

[mgtony]

Cut a cardboard template and take it along to your local bathroom showroom.

[Gingerbread Man]

Does this help?

[omniflow]

Gingerbread Man said:

Does this help?

Thanks - seen that. It's the very simple instruction in there that I'm struggling with - "measure up to the start of the bend" - when exactly does the straight finish and the bend start. Given that after 5 cm the bend is only 0.25mm off the straight and after 10 cm it will be 0.7mm off the straight, it's not really that easy. That's the sort of distance that being sat 1ft different will make.

[Gingerbread Man]

With ya. Who made the shower enclosure that you are replacing? Also who makes the tray? They must have their standards within the manufacture surely?

[wormburner]

Cut two circles from cardboard and see which matches better.

[omniflow]

I think I've cracked it.

I need to measure out from the edge of the shower tray 900mm - might as well do it on both sides. That will give me a square. Then from the corner of that square it will be 207mm to the shower tray if it's a 500mm radius and 228mm if it's a 550mm radius. Shouldn't be too hard to see which.

For anyone interested, that's based on it either being the diagonal of a 350mm * 350mm Square + 550mm or the diagonal of a 400mm * 400mm Square + 500mm. Then subtract this from the diagonal of a 900mm * 900mm square and you have your 2 alternative measurements.

This is still just theory - I can't try it out until the rest of the house has woken up.

If it fails, then I'll follow the suggestion above and cut 2 part circles out of paper and see which is best fit.

[omniflow]

In case anyone is interested, nothing I tried gave me an answer I was truely happy with. I was leaning towards 550mm. However, I eventually managed to dig out the orginal installation instructions for the tray, which didn't have the radius, but did have the model name of the tray. Google then found me some obscure site in Taiwan that had a 10 or 12 year old catalogue on-line. Looking through that then confirmed a radius of 500mm. Measuring it would not seem to be that easy.

[mk1fan]

Surely a straight edge on the outside edge would show where the curve starts.

Although seems sorted now.