Janey Posted April 29, 2006 Report Share Posted April 29, 2006 For the last week my car has had no rear bracing (previously had a rear seatbelt tower brace on) and I have noticed a high amount of 'body flex' when cornering etc. The rear end feels very un-planted (front still has strut & chassis bracing on) and although its not actually effecting the main drive too much, there is a definate flexing movement going on. I am wondering wether this could have an effect on the geometry as if the rear half of the car is moving around in a way which as such 'doesn't seem healthy' Anyone got any ideas on this little theory of mine ?????? Quote Link to comment Share on other sites More sharing options...
Tony Posted April 29, 2006 Report Share Posted April 29, 2006 For the last week my car has had no rear bracing (previously had a rear seatbelt tower brace on) and I have noticed a high amount of 'body flex' when cornering etc. The rear end feels very un-planted (front still has strut & chassis bracing on) and although its not actually effecting the main drive too much, there is a definate flexing movement going on. I am wondering wether this could have an effect on the geometry as if the rear half of the car is moving around in a way which as such 'doesn't seem healthy' Anyone got any ideas on this little theory of mine ?????? If the car wasn't so modified in the suspension area then the detection i feel would be minimal.. but since the car is so rigid... then i feel the retraction of the braces is very detectable. 'Twinkle' you are going to 'Duff' me up for this but i cannot help myself The car has 'angular polar movement'.... The angular movement due to the flexibility from the rear allows the front Yew to rotate the rear outside of the expected polar transition. The weight transfer no longer supports the angular inertia hence the loose rear end.... .......... there i said it In real life it is a little worrying that the 5 could feel so un-stable without braces..... i wonder?.... what made you feel the need to add braces? was it recommendation or just the feel of the drive? Quote Link to comment Share on other sites More sharing options...
Janey Posted April 30, 2006 Author Report Share Posted April 30, 2006 If the car wasn't so modified in the suspension area then the detection i feel would be minimal.. but since the car is so rigid... then i feel the retraction of the braces is very detectable. 'Twinkle' you are going to 'Duff' me up for this but i cannot help myself The car has 'angular polar movement'.... The angular movement due to the flexibility from the rear allows the front Yew to rotate the rear outside of the expected polar transition. The weight transfer no longer supports the angular inertia hence the loose rear end.... .......... there i said it In real life it is a little worrying that the 5 could feel so un-stable without braces..... i wonder?.... what made you feel the need to add braces? was it recommendation or just the feel of the drive? Ahh so in theory: For example, angular acceleration is an axial vector. In classical mechanics, such interactions can be described by Euler's equations for rotational motion: M = Jw. (J - the moment of inertia, w - angular acceleration, M - external momemt) So we can formulate the following definition: If an interaction results in axial accelerations, then this interaction is an axial (torsion) interaction. It should be emphasized that there exist no fundamental generalizations for the equation M = Jw in the modern theory of fields. Thus the modern theory of fields operates only with polar interactions, and torsional interactions are not taken into consideration. Now I get it It is a little disconcerting that there can be that much noticable movement without bracing A friend has a 1990 Roadster with absolutlely no bracing anywhere at and he feels the flex when cornering and over the winter with a hard top on every bend in the road resulted in a creaking where the top was staying put and the chassis was moving My car came with a factory front strut brace, I added the seatbelt one, then did the front chassis one & have now got the roll cage to go in & probably a rear strut & possibly chassis brace. Main reasons for doing this was that people pointed out how bad the car looked in the pics (roll etc) when I was drifting so in theory amongst other bits like changing the knackered shocks & springs, bracing was the next best thing Quote Link to comment Share on other sites More sharing options...
Tony Posted April 30, 2006 Report Share Posted April 30, 2006 If the car wasn't so modified in the suspension area then the detection i feel would be minimal.. but since the car is so rigid... then i feel the retraction of the braces is very detectable. 'Twinkle' you are going to 'Duff' me up for this but i cannot help myself The car has 'angular polar movement'.... The angular movement due to the flexibility from the rear allows the front Yew to rotate the rear outside of the expected polar transition. The weight transfer no longer supports the angular inertia hence the loose rear end.... .......... there i said it In real life it is a little worrying that the 5 could feel so un-stable without braces..... i wonder?.... what made you feel the need to add braces? was it recommendation or just the feel of the drive? Ahh so in theory: For example, angular acceleration is an axial vector. In classical mechanics, such interactions can be described by Euler's equations for rotational motion: M = Jw. (J - the moment of inertia, w - angular acceleration, M - external momemt) So we can formulate the following definition: If an interaction results in axial accelerations, then this interaction is an axial (torsion) interaction. It should be emphasized that there exist no fundamental generalizations for the equation M = Jw in the modern theory of fields. Thus the modern theory of fields operates only with polar interactions, and torsional interactions are not taken into consideration. Now I get it It is a little disconcerting that there can be that much noticable movement without bracing A friend has a 1990 Roadster with absolutlely no bracing anywhere at and he feels the flex when cornering and over the winter with a hard top on every bend in the road resulted in a creaking where the top was staying put and the chassis was moving My car came with a factory front strut brace, I added the seatbelt one, then did the front chassis one & have now got the roll cage to go in & probably a rear strut & possibly chassis brace. Main reasons for doing this was that people pointed out how bad the car looked in the pics (roll etc) when I was drifting so in theory amongst other bits like changing the knackered shocks & springs, bracing was the next best thing In theory no! your car has M+J+Y adding angular Yaw to the equation. The Yaw determines the rotational inertia of an object for a given rate of rotation. The 5 without the brace measures M+J+Y+C center of gravity and roll centre. Quote Link to comment Share on other sites More sharing options...
Janey Posted April 30, 2006 Author Report Share Posted April 30, 2006 In theory no! your car has M+J+Y adding angular Yaw to the equation. The Yaw determines the rotational inertia of an object for a given rate of rotation. The 5 without the brace measures M+J+Y+C center of gravity and roll centre. Darn that Newton bloke So taking out the extra yaw factor (which we don't need/have in this situation ) the gravity points and roll points (as far as I am aware the 5 is pretty centrally balanced) are unstable, & without bracing (generally without in standard in Mk1's, 2's & 2.5's) the car is liable to flexing and therefore possibly causing geometry problems Yes ?? Quote Link to comment Share on other sites More sharing options...
Tony Posted April 30, 2006 Report Share Posted April 30, 2006 In theory no! your car has M+J+Y adding angular Yaw to the equation. The Yaw determines the rotational inertia of an object for a given rate of rotation. The 5 without the brace measures M+J+Y+C center of gravity and roll centre. Darn that Newton bloke So taking out the extra yaw factor (which we don't need/have in this situation ) the gravity points and roll points (as far as I am aware the 5 is pretty centrally balanced) are unstable, & without bracing (generally without in standard in Mk1's, 2's & 2.5's) the car is liable to flexing and therefore possibly causing geometry problems Yes ?? No because you now have Y+C in the initial sum will move on to A+I..(Angular Inertia) and respective forces. so as a sum we would have J+M+A+I then +M or M+J+C+Y+C+A+I - the driver... bless Quote Link to comment Share on other sites More sharing options...
Janey Posted April 30, 2006 Author Report Share Posted April 30, 2006 No because you now have Y+C in the initial sum will move on to A+I..(Angular Inertia) and respective forces. so as a sum we would have J+M+A+I then +M or M+J+C+Y+C+A+I - the driver... bless Blimey we are going to have the whole alphabet soon So let me get this right........The car has angular polar movement due to the flex being present which is due to the weight transfer no longer supporting the angular inertia, so therefore in theory a small pothole in the road would cause a worse long/short term effect to the geometry of the car than the lack of bracing Do I get my Physics degree now Quote Link to comment Share on other sites More sharing options...
Tony Posted April 30, 2006 Report Share Posted April 30, 2006 No because you now have Y+C in the initial sum will move on to A+I..(Angular Inertia) and respective forces. so as a sum we would have J+M+A+I then +M or M+J+C+Y+C+A+I - the driver... bless Blimey we are going to have the whole alphabet soon So let me get this right........The car has angular polar movement due to the flex being present which is due to the weight transfer no longer supporting the angular inertia, so therefore in theory a small pothole in the road would cause a worse long/short term effect to the geometry of the car than the lack of bracing Do I get my Physics degree now Well yes congratulations in truth with the chastity belt off the rear is M+J+A+I sensitive we will move on to 'roll centres' as soon as i can catch up with the math Quote Link to comment Share on other sites More sharing options...
Tony Posted May 28, 2006 Report Share Posted May 28, 2006 No because you now have Y+C in the initial sum will move on to A+I..(Angular Inertia) and respective forces. so as a sum we would have J+M+A+I then +M or M+J+C+Y+C+A+I - the driver... bless Blimey we are going to have the whole alphabet soon So let me get this right........The car has angular polar movement due to the flex being present which is due to the weight transfer no longer supporting the angular inertia, so therefore in theory a small pothole in the road would cause a worse long/short term effect to the geometry of the car than the lack of bracing Do I get my Physics degree now Well yes congratulations in truth with the chastity belt off the rear is M+J+A+I sensitive we will move on to 'roll centres' as soon as i can catch up with the math Bump M+J+A+I+......The suggested (?) Clue Mazda MX5 NA has 45/55.. find the missing denominator.... Quote Link to comment Share on other sites More sharing options...
Janey Posted May 29, 2006 Author Report Share Posted May 29, 2006 BumpM+J+A+I+......The suggested (?) Clue Mazda MX5 NA has 45/55.. find the missing denominator.... W ?? R ?? Quote Link to comment Share on other sites More sharing options...
Tony Posted May 29, 2006 Report Share Posted May 29, 2006 Bump M+J+A+I+......The suggested (?) Clue Mazda MX5 NA has 45/55.. find the missing denominator.... W ?? R ?? Nah your miles away CG+PC (centre of gravity + polar centre) Interesting principle with a 45/55 ratio... Quite important though for the light 5 Quote Link to comment Share on other sites More sharing options...
Tony Posted July 30, 2006 Report Share Posted July 30, 2006 Bump... Ever seeking knowledge i retract my thoughts on 'over-bracing' The reason is that my immediate realm is the 3D environment of Geometry dynamics. I felt uneasy with the steer axis not being able to react during cornering, in particular corner in/on under braking and the diagonal Castor lift effecting the rear. My retraction is based on this...... The 'over-bracing' most times is a compliment to the lower suspension and rated sway-bars so the Geometry needs less involvement during weight transfer allowing the car to maintain a more consistent roll centre, the rigidity of the chassis ensures the camber disparity f/r stays balanced (within reason).. My only concern now is that Castor diagonal lift since the phenomenon happens at the most vital cornering moment. Quote Link to comment Share on other sites More sharing options...
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