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thornycroft Q bb/4


brockwood

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It looks like it's function is simply to locate the spring by compression and likely that each spring leaf has a dimple for location. "some" heat won't change much. You need to have the casting up to red heat (and then let cool) to have any chance to break the bond. Heating the casting up will equally heat the bolt so no difference in expansion, however you might consider cooling the bolt by putting a lunch box (sealed with plasticene) around it and filling the box with crushed ice, or even liquid nitrogen, although the latter may leave the bolt too brittle for serious turning.

good luck!

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Ah, the joys of rusted bolts! This one will just clamp the spring into its seat and will stop on the top of the spring without going through. Heat is the key here. Get the casting just glowing red and keep it that way for a while. Put the spanner on the bolt, having released the lock nut first, and try to unscrew it slightly. The joint should crack. Don't try to keep unscrewing but work it back and forth a bit at a time. You will see the rust begin to drop out as a black powder. As you work it, it will move a little bit further each time until it really begins to move. Persistence is the watchword here. Don't forget that the spanner will very quickly become too hot to touch as well!

Good luck!

Steve

PS. Suggest that you get the axle resting on a big block of timber or axle stands so that you don't knock it off the jack!

Edited by Old Bill
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