Tony Posted December 16, 2007 Report Share Posted December 16, 2007 Sam as you know the Geometry calibration has the opportunity to raise-lower the sprung body, extend or reduce the track and wheel base. In view of this have you or do you intend to experiment with this by calibrating a chassis whilst the car is on corner weight scales and the Geo machine simultaneously. Reason i ask is that manipulation between the un-sprung and the sprung chassis will change the CG and the DI.... It would be interesting if the sprung position could be balanced better by simply calibrating the chassis? In addition if the car is intended for the track would you think it's wise to adjust the body trim height to accommodate the drivers body weight? (assuming the coils are adjustable) I have experimented with this with varying results..... Concern is the coil ratios will be different over the axel or diagonally... This then seems to open a can-O-worms regarding damper ratios. I am aware that for true track use the coil-damper position is so ridged to maintain aerodynamics the drivers body weight falls into insignificance but for the track enthusiast any engligtenment would be valuable. Quote Link to comment Share on other sites More sharing options...
Sam@TDi Posted December 17, 2007 Report Share Posted December 17, 2007 Good series of questions Regarding the manipulation of the corner weights purely by adjusting the static geometry, I've never measured the effects but I would expect them to be negligible. Changing the wheel base by adjusting the static geometry is more likely to be useful as a tuning technique, however normally speaking a movement of 5mm or more would be necessary to produce a measurable change in the handling. Now spring rates, there's more to a spring rate than just keeping the chassis off of the floor. In simple terms the car is made up of two major sections - an unsprung mass and a sprung mass, both normally are in motion. The springs and the dampers form the primary link between these two masses and control the way forces that are present in one mass are passed onto the other. The science of Harmonics plays a massive part in calculating the correct spring rates and it's easy to get this part very wrong. I personally wouldn't specifically modify spring or damping rates in reaction to an imbalanced chassis, especially not across an axle. But as far as I'm concerned it's perfectly logical to set the ride heights so that the chassis is even when loaded in the way that it will eventually be used. This ensures not only accurate static geometry but also even progression of kinematic geometry, this in-turn makes the chassis more predictable and easier to both drive and tune. Quote Link to comment Share on other sites More sharing options...
Tony Posted December 17, 2007 Author Report Share Posted December 17, 2007 That's very interesting Sam thank you very much... As you know i don't currently use weigh scales so i cannot test my own theory's.... One of the cars i often set is the highly adjustable MX5.... Some time back i wrote a set-up for the cars called "fast road", this has proved very popular but i still feel me research is incomplete. To advance on my original question.... For the fast road calibration i sweep the castor forward an additional two degrees (quite a sum).... I cannot measure set-back at the moment but i would assume this additional castor extends the wheel base by at least 20mm. To my question Since the MX5 has a 50/50 weight distribution and i assume a DI of 1.0?... Would the move in castor increase or decrease the DI. Sorry for all the questions..... Quote Link to comment Share on other sites More sharing options...
Sam@TDi Posted December 18, 2007 Report Share Posted December 18, 2007 Extending the wheel base by 20mm would lower the DI. The MX5 is from memory very close to 1.00 as it sits without driver but with a 75kg driver the DI will shoot up to around 1.10 so adding the wheelbase will edge you slightly back towards 1.00 ... If i take an average car weight with a DI of 1.00 thanks to it's wheelbase then added 20mm to the wheelbase the resulting DI would edge down to 0.97 Quote Link to comment Share on other sites More sharing options...
Tony Posted December 18, 2007 Author Report Share Posted December 18, 2007 Superb.... This means my fast road set-up works because the DI is at 1.00 ..... This is the problem in having the theory but not the equipment to test it.... Maybe soon Quote Link to comment Share on other sites More sharing options...
Sam@TDi Posted December 18, 2007 Report Share Posted December 18, 2007 The DI being 1.00 is definitely desirable but don't do your self out of too much credit here as it's only a portion of the picture. The caster angle, static camber and toe will make a more immediate difference to the chassis than the DI. Quote Link to comment Share on other sites More sharing options...
Tony Posted December 20, 2007 Author Report Share Posted December 20, 2007 The DI being 1.00 is definitely desirable but don't do your self out of too much credit here as it's only a portion of the picture. The caster angle, static camber and toe will make a more immediate difference to the chassis than the DI. Problem i have is not knowing the complete picture.... It aggravates me!! For the MX5 fast-road set-up i did some calculations for the castor/camber gains/loses with the wheel at a 10 degree lock... The gains on the inner wheel where amazing lucky me since the math was reasonably simple.... Next stage would be to add some dynamic "pull downs" to simulate weight transitions but i cannot do this without weigh scales and a laser horizon plotter. Quote Link to comment Share on other sites More sharing options...
Sam@TDi Posted December 24, 2007 Report Share Posted December 24, 2007 I think your getting very close to seeing the entire picture in the area of DI, Static and Kinematic Geometry. When your totally comfortable with these major first chapters we should then start discussing dynamic weight and force transfer Quote Link to comment Share on other sites More sharing options...
Tony Posted December 24, 2007 Author Report Share Posted December 24, 2007 I think your getting very close to seeing the entire picture in the area of DI, Static and Kinematic Geometry. When your totally comfortable with these major first chapters we should then start discussing dynamic weight and force transfer Indeed.... I need to do some "proving" to ensure my theory does translate correctly.. So far on paper and customer feed back i can scratch the itch but i feel uncomfortable with this until i have conclusive data. My diary for next year is to consume.... 1> RWD squat gains for the track car (researched using the 200sx) 2> TOOT study with an economical modification for the track car 3> Lock angle accentuater for Drift cars 4> wim table of calibration positions for the Mazda MK3 NC 5> Study of kinematic transitions on weigh scales including static Geometric graphs Mark suggested some insight to aerodynamics....... I think not for a year or two at least Quote Link to comment Share on other sites More sharing options...
Sam@TDi Posted December 27, 2007 Report Share Posted December 27, 2007 I think that's a sounds plan, the chassis dynamics rabbit hole certainly does go very deep Quote Link to comment Share on other sites More sharing options...
Tony Posted December 27, 2007 Author Report Share Posted December 27, 2007 I think that's a sounds plan, the chassis dynamics rabbit hole certainly does go very deep Objective for 08 is not to go bunny eyed or turn rabbit because the topic is heavy... The Drift research needs concluding asap..... Ever more so since Driftworx drift team want wim to set their cars Quote Link to comment Share on other sites More sharing options...
scorps Posted December 27, 2007 Report Share Posted December 27, 2007 Driftworx drift team want wim to set their cars When did this happen?.......nice one guys Quote Link to comment Share on other sites More sharing options...
Tony Posted December 27, 2007 Author Report Share Posted December 27, 2007 Driftworx drift team want wim to set their cars When did this happen?.......nice one guys Today .... Looks like our insight for the Drift community is making waves. Quote Link to comment Share on other sites More sharing options...
TDIPLC Posted December 27, 2007 Report Share Posted December 27, 2007 Driftworx drift team want wim to set their cars When did this happen?.......nice one guys Today .... Looks like our insight for the Drift community is making waves. Excellent news Tony. Well done. Sam assisted Jap Performance magazine recently to compose a technical article on chassis dynamics in general and for drifting. The article is due to be published shortly so that should help raise peoples awareness too Quote Link to comment Share on other sites More sharing options...
Tony Posted December 28, 2007 Author Report Share Posted December 28, 2007 Driftworx drift team want wim to set their cars When did this happen?.......nice one guys Today .... Looks like our insight for the Drift community is making waves. Excellent news Tony. Well done. Sam assisted Jap Performance magazine recently to compose a technical article on chassis dynamics in general and for drifting. The article is due to be published shortly so that should help raise peoples awareness too I'll look forward to that article .... I will admire Sam if he's managed to compress chassis dynamics explanation to anything less than 50 pages, it's a nightmare Quote Link to comment Share on other sites More sharing options...
Sam@TDi Posted December 29, 2007 Report Share Posted December 29, 2007 I definitely haven't I just skimmed over the main chapters. The frustrating thing is that as I was trying to simply summarize these difficult subjects the natural tendency of the journalist was to ask what he thought were simple questions that in fact required in depth understanding of some complicated sub-subjects to explain properly, but we got there in the end. I think he filled up one and a half 90min audio tapes over a 4hr period He told me he'd send me the article to proof before it goes to print so it'll be interesting to see how it's written. Quote Link to comment Share on other sites More sharing options...
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