Thursday, October 11, 2007

Running a temperature

Being the second in the rivetting series etc etc ...

On our last visit to Warrior we also changed the engine thermostat. The old one was a second hand one that Compo found in the back of his van - I'm not sure what was in it before the rebuild. Actually this was working fine, but the new one finally arrived from RN, so we thought we'd fit it. There was sone discussion, I remember, in the early stages of what sort of thermostat it should have and what its running temperature should be. Before we started any work on the engine it was running at 80+; I think (but might be remembering wrongly) that there wasn't a great deal of agreement at RN about what its ideal running temperature should be, with recommendations ranging from 60 max to over-eighty-is-fine.

Also I am not 100% sure what the thermostat actually governs; I think it is the temperature at which the cooling water switches from the calorifier to the skin tank. Anyway, the 'old' one was meant to be 60 degrees - and may well have been for all I know. But when we were beasting up the Nene/Ouse/Hundred Foot the engine was frequently running at eighty and nudging beyond that. In fact, so skilled did I get at reading it, this became the most reliable guide to the revs and/or speed we were going at. I got to be able to tell from walking past the engine whether it was running hot, when I would poke my head out and say, perhaps we might try slowing down a little bit... So, we changed the thermostat, but haven't had a run since so don't know if it will make any difference.

I suspect it might not. If it works as I think it does, then it's not the thermostat that's the problem (if problem it be). It's letting the water through to the skin tank OK. I know that because when we were really going for it the top of the skin tank was too hot to touch. Seems to me that the 'problem' is that this is an engine that was designed to be cooled by a constant supply of raw, cold, sea water. Our little skin tank just can't dissipate that heat fast enough. (And I did try not to put too much blacking on it.) But I hesitate to call it a problem. The problem is that sometimes we go too fast ...

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