CTE of different shapes of 4130
CTE of different shapes of 4130
(OP)
I have a cylinder that I am working on that has pretty tight tol. and I am questing the basic design. Picture a 8.0000 diameter x 6.000 solid double acting piston with a rod diameter of 6.000 in an 8.0005 cylinder with 6.0005 bearings. In order to reduce the hydraulic working area of the cylinder for resolution purposes, the band-aid design uses two rings at 8.000 x 6.0002 x 1 to attach to the rod at the piston.
My question...
Will the piston, rings and cylinder expand at the same rate and to the same relative dimensions when heated from 75 degrees F to 200 degrees F? I contend that they will not, and that the rings will change enough to cause possible damage to the cylinder walls.
And don't ask me why the tolerances are so tight, I have no idea, it seems crazy to start with to me.
Thanks in advance for your reply.
My question...
Will the piston, rings and cylinder expand at the same rate and to the same relative dimensions when heated from 75 degrees F to 200 degrees F? I contend that they will not, and that the rings will change enough to cause possible damage to the cylinder walls.
And don't ask me why the tolerances are so tight, I have no idea, it seems crazy to start with to me.
Thanks in advance for your reply.





RE: CTE of different shapes of 4130
Mike Halloran
Pembroke Pines, FL, USA
RE: CTE of different shapes of 4130
Aaron Tanzer
www.lehightesting.com
RE: CTE of different shapes of 4130
Thanks again.
RE: CTE of different shapes of 4130
Rule of thumb: .0001" interference per inch of diameter is a good start. Two thou is a fairly heavy press fit for steel even at 6.000 diameter.
If the piston and cylinder and end cap diameters, all of them, are not dead nuts concentric, and they pretty much can't be, that's another contributor to stress, and should be checked. The usual preventive measure for problems like that is a little extra clearance in one set of mating diameters.
Photos of the failure might get you additional inputs.
Mike Halloran
Pembroke Pines, FL, USA
RE: CTE of different shapes of 4130
RE: CTE of different shapes of 4130
Something to think about....