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Amicale Spitfire Bienvenue sur Cyberspit ! Ce forum est réservé aux discussions autour des Triumphs. Lisez-moi |
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| barzoi 1971 24/11/2014 20:21 |
ressort |
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| Bonjour à tous, je me pose une question: quelles différences y a t'il entre un ressort de suspension arrière de Spit MK1 ou 2 et un ressort de gt 6 rotoflex ? Je suis sûr que beaucoup d'entre vous le savent........ FC |
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| collete 24/11/2014 22:12 |
re : ressort |
| La référence du catalogue. | |
| barzoi 1971 24/11/2014 23:01 |
re : ressort |
| Merçi collete pour cette réponse quelque peu laconique. Je supose que si les références ne sont pas identiques, il y a des différences en longueur, nombre de lames, cambrure, dureté etc. C'est plus ça que je demande.......... FC |
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| Pas_volay 25/11/2014 12:02 |
re : ressort |
| Je ne pourrais pas dire mieux que Paul Geithner que j'ai déjà, cité dans un autre fil, donc voici: ------------------------------------------------------------------- Hi Mike- Just to add to what Charles and Joe have said. The primary disadvantages of the swing axle setup are poor camber control, a high roll center and limited tunability. A way to radically reduce the rate of rear camber change, lower the rear roll center and provide greater tunability is to eliminate the swing axles altogether and switch to a fully-independent multi-link rear suspension architecture in which the drive elements are not themselves suspension links. Triumph achieved this with the "rotoflex" suspension it used on the GT6 mk2, a.k.a. GT6+, and early GT6 mk3 (rotoflex was used on the 2 liter Vitesse mk2 too). Instead of swing axles, a lower wishbone plus a radius arm on each side serves as the lower suspension link. The transverse spring is the upper suspension element and a vertical link houses the hub bearing. The drivetrain element is a two-piece shaft connected by an elastic "donut" that is stiff enough in rotation to transmit drive torque yet flexible enough orthogonal to rotation (i.e., along the direction of the shaft) to allow the assembly to vary in length (plunge and extension) and thus permit inboard and outboard motion of the wheels and proper suspension articulation. The rotoflex suspension has the distinct advantage of reduced rate of camber change, a lower rear roll center and greater tunability (e.g., adjustable camber curve and roll center), but it is much heavier than the swing axle setup (about twice the mass), has a higher parts count and is difficult to maintain. The vertical link is rather massive and unsprung. The lower wishbone is heavy too and is partially unsprung, and the elastic rotoflex donuts are heavy, mostly unsprung, prone to wearing-out and difficult and expensive to renew. One other note on this setup is that it has a 49 inch track (1 inch wider than the "short swing axle" Spifires and GT6 mk1, but 1 inch narrower than the "long swing axle" cars). So, the GT6 mk2 rotoflex design is a compromise. Given the swing axle architecture's advantages in simplicity and reduced parts count and hence low cost, low maintenance and reduced mass, plus things like the swing spring to compensate for its primary disadvantage, it's not a mystery why swing axles reappeared in the later GT6 mk3 and persisted in the Spitfire. There is one very good upgrade to the rotoflex design that addresses most of its shortcomings, and that is to replace the rotoflex driveshafts themselves with constant velocity (CV) joint driveshafts. Canley Classics has developed such a driveshaft, deriving it from one that Triumph used in its front wheel drive 1500. Nick Jones in the UK makes similar CV jointed driveshafts and slightly modified vertical links/hub bearing carriers. These CV driveshaft options weigh less than the rotoflex ones, are easy to install, have a smaller envelope and require little maintenance. Plus there is little to no stress from plunge and extension of the CV driveshafts like there is from the elastic rotoflex donuts on the hub bearings and inner u-joints of the stock rotoflex arrangement (albeit the stress of rotoflex donut plunge and extension is much less than what swing axle u-joints experience from lateral loads). Also, you can get lighter weight alloy vertical links and aluminum wishbones or make tubular steel ones to further significantly reduce mass (the wishbones are curved to clear the rotoflex donuts, but CV driveshafts permit straight ones). The combined mass savings of CV driveshafts, alloy vertical links and aluminum wishbones is roughly 5 kg per side, much of which is unsprung, reducing total mass of the setup by about 25 percent and roughly splitting the difference in mass between the rotoflex and swing axle setups: GT6 mk2 rotoflex setup = ~20 kg one side (includes brakes and radius arm) GT6 swing axle setup = ~12 kg one side Setup with CV driveshafts, alloy links and aluminum wishbones = ~15 kg one side To answer your question about front anti-roll bars (ARBs), a larger front ARB is used with the swing spring because the swing spring has lower roll stiffness than any of the fixed springs and so using the thicker bar with a swing spring maintains total vehicle roll stiffness (the fixed spring in the GT6 rotoflex cars has a semi-elliptical spring rate of 185 lbs/in, resulting in a wheel rate on the same cars of 66 lbs/in and a rear contribution to roll stiffness of 114 ft-lbs/degree; the semi-elliptical rate of a Spitfire swing spring is 320 lbs/in for a wheel rate of 110 lbs/in on long axle cars and a nominal rear contribution to roll stiffness of around 41 ft-lbs/degree; everything being stock, the total vehicle roll stiffness of a rotoflex GT6 is about 350 ft-lbs/degree, and a Spitfire 1500, weighing about 100 to 200 lbs less, is about 320 ft-lbs/degree). While on the subject of ARBs, note that adding rear roll stiffness by fitting a rear ARB is typically not a wise idea on a swing axle car because it exacerbates jacking. This is why zero-roll stiffness devices that add vertical stiffness to limit camber change, like Z-bars and leaf-style camber compensators, have been applied to various swing axle cars for decades. An ARB, which adds roll stiffness without affecting vertical stiffness, is the mechanical converse of a Z-bar or leaf-style camber compensator, which adds vertical stiffness without affecting roll stiffness. Controlling rear camber change and reducing or precluding jacking are paramount objectives of swing axle control, which results in compromises. When switching to a multi-link independent rear suspension (IRS) architecture like the rotoflex or its derivatives, then keeping a thinner bar up front with the fixed spring at the rear is OK and adding a rear ARB is an option. Some folks, like Laurence Cochrane, even use a swing spring as part of a multilink IRS (in his case, he uses sliding driveshafts rather than rotoflex or CV ones; I think Steve Smith [GT6Steve] may use sliding shafts as well, but with a custom fixed spring). The major point here is that the multi-link independent rear offers another dimension of flexibility of tuning in that both front and rear bars may be employed and tuned separately to achieve a wide range of roll stiffnesses and front to rear roll stiffness biases. Joe's point about changing out the transverse leaf spring for hinged arms and coil-overs on each side is an interesting one--it affords even more tuning flexibility in that ride height and vertical stiffness can be tuned independently and more easily. On a different note, it's a good idea to have multiple lower wishbone fulcrum attach points to tune static wishbone angle and hence static roll center location and the camber change curve, as well as tweak ride height. Again, the great thing about a rotoflex rear suspension and its derivatives is that they are true multilink IRS's and so afford a lot more flexibility of tuning (rear camber curves, rear roll center, and roll stiffness and roll stiffness distribution), but at the expense of added mass and complexity. If you employ mass savings and maintenance improvement options to the rotoflex approach, the added flexibility of tuning and higher potential for performance are pretty attractive. That said, many people--hobbyists and racers--have been able to get good performance with high reliability and low maintenance out of a swing spring + swing axle setup. Paul Geithner http://auskellian.com/paul/spit.html ------------------------------------------------------------ Pour une traduction approximative mais c'est mieux que rien, voir ici: https://translate.google.fr/translate?sl=de&tl=fr&js=y&prev=_t&hl=fr&ie=UTF-8&u=http%3A%2F%2Fwww.triumphexp.com%2Fphorum%2Fread.php%3F8%2C737757&edit-text= (poste du 6 mai 2012 à 22h17) |
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| barzoi 1971 25/11/2014 16:44 |
re : ressort |
| Merçi Pas Volay Ca fait avancer........ FC |
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| Belligou * 25/11/2014 19:29 |
re : ressort |
| Bonsoir, Sur GT6 Mk2, le ressort a 6 lames . Epaisseur d'une lame = 5,9 mm.(doc. atelier). Ne peut être monté sur Spit Mk1/2. Pour info, le ressort à lames de la Spit Mk1 et Mk3 (et non Mk2) peut être monté sur la GT6 Mk1 non rotoflex (http://www.canleyclassics.com/triumph-gt6-mki/ii-rear-suspension-non-rotoflex) Jean |
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| néo69 26/11/2014 21:46 |
re : ressort |
| Ressort gt6 plus dure et swing spring, ressort mk 1 2 spring fixed . Peux tu nous communiquer tes intentions? Es ce pour un de tes voitures de course? Peux tu êtres plus precis dans ta question? | |
| barzoi 1971 26/11/2014 23:04 |
re : ressort |
| Bonsoir Néo, En 1965 une Spit, proche des usines a couru avec un 4 cylindres en 1300 cc et une suspension arrière style gt6 r, un peu comme les gt6 plus tardives. Elle gagnait parait il presque toujours sa classe de cylindrée. Voilà, je réfléchis à ça mais ça ne verra peut être jamais le jour. FC |
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| néo69 27/11/2014 00:29 |
re : ressort |
| J'ai entendu parler de cette voiture qui aurai couru en GTP, en 65 à la coupe des alpes, avec un 1300, mais pas de SPIT. Pour la lame de GT6 j'en ai aussi entendu parler par quelqu'un qui courrait avec, mais modifié façon "special Turing for triomphe Spitfire". | |
| néo69 27/11/2014 00:32 |
re : ressort |
| Mais peux être parle tu de l'auto Peter Cox? |
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| barzoi 1971 27/11/2014 09:07 |
re : ressort |
| Néo, Je ne sais pas comment était montée la voiture de Peter Cox. Moi je pense à ERW 412C de Bill Bradley. FC |
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| néo69 27/11/2014 20:42 |
re : ressort |
| A la vue de cette voiture, il apparaît un carrossage négatif important, qui me laisse penser qu'elle a un train arrière à bras tendues. Tu nous parle bien de lames ressort de gt6 et non du système rotoflex? | |
| barzoi 1971 27/11/2014 22:11 |
re : ressort |
| Graham Robson dans son livre Sur les Triumph donne les indications que j'ai rapportées plus haut. Je n'en sais pas plus. FC |
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