question about expanding metals

[steveo3002]

ive got a steel bar thats a sliding fit inside a alloy housing like a tube , its part of the shifter mech in a car gearbox

now ive just fitted a load of new parts and something is getting tight once its warm

how would those parts behave once warm ..is it likley the steel bar would expand more than the alloy tube and begin to nip up , its under oil and only gets warm not scadling hot

parts on the lft of this pic

 

[tigler]

In a word, no. Aluminium expands more than steel at a given temperature.

 

[steveo3002]

ah good so that eliminates that then , it would get slacker when warm if anything

 

[tigler]

Thats correct.

 

[cumbriasteve]

Thinking out of the box here:..if the aluminium expands, then I assume in expands in all directions, could it not also expand on the internal diameter and tighten onto the steel shaft

 

[gordon stephenson]

If the outside of the aluminium is not constrained then the bore will grow bigger,

 

[rtbcomp]

I look at from the point of view that all the dimensions increase. It works in practice as you heat ally pistons in hot engine oil to allow the gudgeon pins to slide in easily.