sand-eel
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Registered: 15th Mar 07
Location: carluke/braidwood--IRNBRULAND
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Just done a analysis on two springs very simple ones 300mm and 260mm high both have, pitch 50mm(distance between coils), profile 30mm thick, steel, diameter 200mm. oh yeah and a 2000N load.
Decide for yourselfs if they are a bad idea or not.........
displacement uncut 5.173mm
displacement cut 4.704mm
strain uncut 0.0913 N mm
strain cut 1.077 N mm
stress uncut 151 N/mm^2
stress cut 491 N/mm^2
Well the displacement "movement" decreases on the cut spring so possibly an increase in spring rate.
The strain goes up when cut but is still very low at just over one newton per mm.
Stress on the cut spring goes up alot this happened possibly because when i cut the spring there was a sharp edge somewhere so will not be that high probably around the 350 N/mm^2 mark, this is still low because steel yields "breaks" at around 1000N/mm^2 or more for normal stuff you can get really crap steel at around 300 N/mm^2 but i doubt people would use that on car springs somehow.
[Edited on 10-06-2008 by sand-eel]
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Colin
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Registered: 4th Apr 02
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MS Paint 
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sand-eel
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Registered: 15th Mar 07
Location: carluke/braidwood--IRNBRULAND
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Pro-Engineer
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antoni
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Registered: 30th Dec 07
Location: irlam, manchester
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i dont get it 
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Archie
Organiser: Scotland
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Registered: 18th Dec 07
Location: South Ayrshire
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quote:
Originally posted by kangaroojack
i dont get it
x2
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sand-eel
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Registered: 15th Mar 07
Location: carluke/braidwood--IRNBRULAND
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ok cutting the springs technically should be fine.
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Sean-B
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Registered: 1st May 07
Location: Wolverhampton Drives: 200SX S14a
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whoop, did my thread inspire this by any chance?
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John G
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Registered: 18th Jul 05
Location: Wirral, Merseyside
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Persoanlly i think your analysis would fall flap on its hoop if you were do it for rear springs.
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sand-eel
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Registered: 15th Mar 07
Location: carluke/braidwood--IRNBRULAND
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yes.....yes it did
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sand-eel
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Registered: 15th Mar 07
Location: carluke/braidwood--IRNBRULAND
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quote:
Originally posted by John G
Persoanlly i think your analysis would fall flap on its hoop if you were do it for rear springs.
cutting rear springs are a bad idea though, because of there shape, they won' sit properly anymore.
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John G
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Registered: 18th Jul 05
Location: Wirral, Merseyside
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quote:
Originally posted by sand-eel
quote:
Originally posted by John G
Persoanlly i think your analysis would fall flap on its hoop if you were do it for rear springs.
cutting rear springs are a bad idea though, because of there shape, they won' sit properly anymore.
I fear your analysis will only stride people on to continue cutting rear springs, peronally any home bodging of this sort is beyong me!
[Edited on 10-06-2008 by John G]
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mattyross
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Registered: 22nd Dec 05
Location: lincolnshire Drives: 1997 C12NZ
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excellent work man
i am a dab hand finite element analysis myself
impressed by this, i like to see practical uses for pro-mechanica
just a suggestion, you could lower the legend value for the stress/strain
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Ellis
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Registered: 11th Sep 07
Location: Aberdeenshire
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Whats the conclusion for the rear springs?
Are they likely to fail if cut? At what load?
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Gareth F
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Registered: 16th Jan 08
Location: Location Location
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Put me right, always thought it was a bad idea due the spring not sitting properly.
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ainsley_brader
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Registered: 24th Mar 02
Location: Tattershall, Lincolnshire
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are corsa springs the same diameter and same distance between coils?
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mikesc20let
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Registered: 13th May 08
Location: nottingham
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if your a real tit arse then you can cut the front springs but not the rear as the rears are impossible to cut and get to sit rite but after all the hassle why dont you just buy a second hand kit or just sum properly lowered springs
[Edited on 10-06-2008 by mikesc20let]
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Brett
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Registered: 16th Dec 02
Location: Manchester
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Wow, look how clever you are! 
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Mase
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Registered: 16th Sep 01
Location: Derbyshire
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this is my kind of thing!
Pro-mechanica isn't that hard really... only used it briefly mind....
My only concern regarding the analysis is that it cannot take account of any fatigue. I would be concerned about existing fatigue cracks, which would have a tendency to open if loaded with a greater stress, reducing its service life....
Mase
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mattyross
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Registered: 22nd Dec 05
Location: lincolnshire Drives: 1997 C12NZ
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quote:
Originally posted by Mase
My only concern regarding the analysis is that it cannot take account of any fatigue.
good point. i think you can set a model for cyclic fatigue, i remember doing it.
good effort sand-eel.
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RCS
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Registered: 26th Jan 05
Location: Lichfield/Dundee
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Where does maximum stress occur on the cut spring? And how have you applied the load?
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sand-eel
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Registered: 15th Mar 07
Location: carluke/braidwood--IRNBRULAND
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The constraint is at the top where the spring sits at the strut top and the load is applied at the bottom where it sits, but it doesn't matter where because it's the same size either way so you could do it opposite and it would be the same.
The maximum stress is at the top where the cut was made, if you smooth out any sharp edges max stress will reduce.
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sand-eel
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Registered: 15th Mar 07
Location: carluke/braidwood--IRNBRULAND
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quote:
Originally posted by Mase
this is my kind of thing!
Pro-mechanica isn't that hard really... only used it briefly mind....
My only concern regarding the analysis is that it cannot take account of any fatigue. I would be concerned about existing fatigue cracks, which would have a tendency to open if loaded with a greater stress, reducing its service life....
I can do a fatigue test yes....
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sand-eel
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Registered: 15th Mar 07
Location: carluke/braidwood--IRNBRULAND
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actually i can't because i need the hardness level for steel......
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