Telescopic Overlap
Telescopic Overlap
(OP)
Readers,
I am in the middle of designing a telescopic support. It is simply a cylinder inside a cylinder. The base cylinders is 300mm OD x 274ID and 800mm long. The second (Sliding) is 273.8OD x 254ID and 700mm - Material is ASTM A316. I have a 120mm overlap at full extension.
There is a 15,000 Nm moment being applied to the top cylinder.
I am trying to determine the if the overlap length is sufficient to prevent jamming and also failure. I have completed this using FEA, however would like some possible hand calculations to verify the FEA Solutions.
Any help would be appreciated
I am in the middle of designing a telescopic support. It is simply a cylinder inside a cylinder. The base cylinders is 300mm OD x 274ID and 800mm long. The second (Sliding) is 273.8OD x 254ID and 700mm - Material is ASTM A316. I have a 120mm overlap at full extension.
There is a 15,000 Nm moment being applied to the top cylinder.
I am trying to determine the if the overlap length is sufficient to prevent jamming and also failure. I have completed this using FEA, however would like some possible hand calculations to verify the FEA Solutions.
Any help would be appreciated





RE: Telescopic Overlap
spread that out over 13*75 (WAG) mm,=1000 mm^2 gives a stress of 125 n/mm^2
I'd say you've got a problem with plastic deformation. 120mm overlap is ridiculously little given your tube geometry
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Telescopic Overlap
Also, with 316 running against 316, there could be some galling problems. Fairly high contact pressures around the openings of both tubes in the overlap under this load, as I am sure your FEA has shown.
RE: Telescopic Overlap
Cheers
Mark
RE: Telescopic Overlap
or possibly
wildly-accurate guess
TTFN
RE: Telescopic Overlap
Regards,
-Mike
RE: Telescopic Overlap