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bearmtnmartin
bearmtnmartin GRM+ Memberand HalfDork
4/17/13 1:25 p.m.

I sometimes wonder if people who are so eager to bastardize Triumphs have ever really looked into what they can do with the stock components set up properly. They are not slower than a Miata. I have never raced one but I have watched them destroy much larger cars on a tight track. Below is just an example, and you will notice the winning Triumph was 14 seconds ahead of the closest MIATA.

ELKHART LAKE, Wis. - Provisional Results from Friday’s F Production National Championship Race, part of the 48th SCCA National Championship Runoffs at Road America with finish position, starting position in parenthesis, driver, hometown, car and laps complete.

1, (1), Steve Sargis, Frankfort, IL, Triumph Spitfire 1500, 13. 2, (2), Eric Prill, Topeka, KS, Mazda Miata, 13. 3, (5), Charlie Campbell, Corry, PA, Mazda Miata, 13. 4, (10), Sam Henry, Republic, MO, Mazda Miata, 13. 5, (7), Bill Wessel, Madison, WI, Nissan SPL311, 13. 6, (8), Robert Bramlage, Junction City, KS, Mazda Miata, 13. 7, (12), Scott Lunder, Mentor On The Lake, OH, Honda Civic, 13. 8, (14), Joe Walker, Richland, MI, Lotus Super 7, 13. 9, (15), Sean Powers, Peoria, AZ, Mazda Miata, 13. 10, (13), Robert Keller, Algonquin, IL, Volvo P1800, 13. 11, (16), Mark Weber, Saint Louis, MO, Mazda Miata, 13. 12, (17), Chris Patrick, Derry, PA, Triumph Spitfire 1500, 13. 13, (19), Mike Gnadt, Kiel, WI, MG Midget, 13. 14, (18), James R Smith MD, Alvin, TX, Honda Civic Del Sol, 12. 15, (22), Brent Louzon, Colorado Springs, CO, BMW 2002, 12. 16, (21), Paul Jensen, Colorado Springs, CO, Mazda Miata, 12. 17, (9), Mason Workman, Reynoldsburg, OH, Mazda Miata, 12. 18, (4), Kevin Ruck, Delaware, OH, Acura Integra, 11. 19, (3), Ken Kannard, East Troy, WI, Mazda Miata, 7. 20, (11), Dieter Griesinger, Maple Park, IL, Triumph Spitfire 1500, 6. DNF, (6), Donald Kraftson, New York, NY, Elva Courier, 4. DNF, (20), Gerald Lamb, Oswego, IL, MG B, 2. DNS, (23), Lee Feineigle, Van Buren, OH, MG Midget, 0.

erohslc
erohslc HalfDork
4/17/13 1:27 p.m.
Ian F wrote: ... A Spitfire is a deceivingly tightly packaged car. When you open that huge bonnet you think, "Wow! Look at all that room!" but in reality there's barely enough room for what's there and even then they had to make compromises.

True Dat!

There are a few swaps involving minimal changes that make sense, but IMHO, most do not.

Curmudgeon
Curmudgeon MegaDork
4/17/13 4:35 p.m.
erohslc wrote: The Spitfire/GT6 are both derivations of the Herald chassis and running gear. A GT6 is basically a Spitfire with a 6 cylinder motor. So just about any of the Spitfire/GT6 pieces can be swapped, usually as a bolt-in. The Rotoflex was a clever way (Chapman-esque clever) to get a 4 link IRS instead of swing axle. It's basically just an SLA design, but upside down. No one complains about that design. Those throwing stones at using the transverse spring as the upper link should redirect their ire at the implementation of the cast iron lower link, equalled only perhaps by the T-Bird IRS lower link as the heaviest and most inelegant piece ever designed. Another thing, when modeling the camber curve, remember that we are dealing with a quarter elliptic spring section, not a solid link. This means that effective length *decreases* with deflection, since the spring curves rather than pivots, drawing the top of the vertical link inwards more than a link would, increasing camber. I doubt that many (any?) of the suspension modelling software packages get that part right. In addition, since a leaf spring is *very* stiff in transverse plane, there is no need for upper fore/aft location, ie upper trailing arms. Given that, the PRI system is basically just a replacement for the transverse spring, requiring the addition of coilovers to perform spring duty. On a Spitfire (or non-roto GT6), the spring is not really a suspension member, it has no effect on camber. So the PRI setup does absolutely nothing on those, even though it will bolt up. On a roto GT6, there is an opportunity for improvement, since the inner pivot could be relocated to alter the camber curve. I'm not aware that this opportunity was taken on the PRI design. And anyway, the same effect can be had by relocating the *lower* pivot. That said, I tend to agree, enjoy them for what they are. Carter

The bolded items are the two really poorly thought out areas of the GT6 Rotoflex suspension. The other thing is that the upper outer eye describes a different arc (shallower) than the lower outer eye's sharper arc, this leads to a camber curve that starts out negative at full droop and goes toward positive as it compresses. The toe links don't help, they are short and thus describe a 'sharper' arc than a longer one. So you have a really strange camber curve combined with a far amount of dynamic toe in the understeer direction on the outside. What's not to love?

About the only real fix I could think of would be to make shorter upper control arms, lose the transverse spring, add coil overs and much longer toe links with repositioned front pivot points.

foxtrapper
foxtrapper PowerDork
4/17/13 8:26 p.m.
Curmudgeon wrote: So you have a really strange camber curve combined with a far amount of dynamic toe in the understeer direction on the outside. What's not to love?

The only thing that could make it better would be if the car were to have reverse ackerman angles up front when the turn the front wheels far off center.

erohslc
erohslc HalfDork
4/17/13 9:22 p.m.

Ha, nice one Fox ;)

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