(Found) Looking for story set on a low tech world where there is a metal door/structure that the inabitants have open.

[Mickey2412]

I remember they need to discover that principles of metal expansion and contraction enable them to open the door. Would be at least 20 years ago.

 

[Danny McG]

Extract below is from the Wikipedia entry for "Earthsearch 2" by James Follet - the sequel to Earthsearch. It was the novelization of the weekly radio series.

The crew examine the tower, finding that there is a door set into one side which cannot be opened. Peeron says that many of his predecessors have made attempts over the centuries - for example, by hitting the door with battering rams - but it will not budge. It is said that it is held shut by a "lock of knowledge". Darv eventually works out how to open the ingeniously simple lock, which requires a low grade of technology which would only be available to people who have already worked out basic principles of science and engineering. The door is a very close/accurate fit in the aperture, and contains mild heating elements that cause it to expand and lock in place. These heaters do not heat it to the point that it is warm to the touch. Simply attaching a refrigeration system to the door and cooling it a few degrees causes the door to shrink and move freely

 

[Mickey2412]

That's it I'm sure. Thanks so much I'll try and get hold of a copy.

 

[Danny McG]

No probs, as soon as i saw your question I browsed for Earthsearch, long time since I read it

 

[monkeypooper]

Wow these ring a bell added to my tbr pile i have already but so long ago actually i think i only read earthsearch not the other 2 i read it because he wrote for blakes7 and i loved that show