Another S2K race car project
07-13-2012, 09:21 PM
#21
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Sorry for my English but I didn't really understood (no offence). What exactly do you mean?
Thanks
Ted
[/quote]
Sorry Ted, no offense taken and nevermind what I said...I was trying to be funny, but it was just stupid.
Awesome stuff, thanks for the write up!
Thanks
Ted
[/quote]
Sorry Ted, no offense taken and nevermind what I said...I was trying to be funny, but it was just stupid.
Awesome stuff, thanks for the write up!
07-14-2012, 09:50 AM
#23
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After looking at the car closely, collecting bits of information, actually starting to design bits it was evident that there actually are some real issues in a way of designing a quick car. I talked to Alexander (car owner) and decision came to do things a bit differently. Many tuners offer some bits like adjustable a – arms, boll joints that alter RC height etc. I don’t know how they came up with their results and don’t have time/funds to check/measure/analyze them all.
Why don’t we do something that wasn’t done too often? Redesign the car so that only few areas leaves us wishing it was different. Budget is very restricted so we cannot go really far but this project will have:
BT4 T45 steel roll cage designed so to increase torsinal stiffness as much as possible. If one gets it stiff enough than he doesn’t have to worry about strength because it will be many times more than actually needed.
Purpose designed front and rear suspension geometry.
Purpose designed front/rear subframes, a – arms, tie rods, steering rack, blade type ARB’s.
Purpose designed uprights.
Goals that it should allow to achieve:
1. Significantly reduce overall mass, as well as unsprung masses of the car.
2. Suspension geometry that will avoid pitfalls inherent in OEM street car design and will allow high degree of tunability in short time (adjustment time is always crucial because track time is expensive/restricted) .
3. Package effective aero parts.
So here we started with roll cage:
One of the main goals was to stiffen as much as possible suspension pickup points as well as subframe mounting points. There's no point in having stiff chassis while installation stiffness is low. Triangles help as always.
Hint - think about chassis flex in this way: There are two spring pairs front axle and rear axle. Chassis is the 3d spring connecting it. If this spring is not stiff enough than changes to roll stiffness at front or rear would not effect overall weight transfer distribution significantly enough. Also it may react to road and driver inputs very inconsistently.
Notice that there’s no gussets on this 3D model – they will be added later.
Thanks
Ted
Why don’t we do something that wasn’t done too often? Redesign the car so that only few areas leaves us wishing it was different. Budget is very restricted so we cannot go really far but this project will have:
BT4 T45 steel roll cage designed so to increase torsinal stiffness as much as possible. If one gets it stiff enough than he doesn’t have to worry about strength because it will be many times more than actually needed.
Purpose designed front and rear suspension geometry.
Purpose designed front/rear subframes, a – arms, tie rods, steering rack, blade type ARB’s.
Purpose designed uprights.
Goals that it should allow to achieve:
1. Significantly reduce overall mass, as well as unsprung masses of the car.
2. Suspension geometry that will avoid pitfalls inherent in OEM street car design and will allow high degree of tunability in short time (adjustment time is always crucial because track time is expensive/restricted) .
3. Package effective aero parts.
So here we started with roll cage:
One of the main goals was to stiffen as much as possible suspension pickup points as well as subframe mounting points. There's no point in having stiff chassis while installation stiffness is low. Triangles help as always.
Hint - think about chassis flex in this way: There are two spring pairs front axle and rear axle. Chassis is the 3d spring connecting it. If this spring is not stiff enough than changes to roll stiffness at front or rear would not effect overall weight transfer distribution significantly enough. Also it may react to road and driver inputs very inconsistently.
Notice that there’s no gussets on this 3D model – they will be added later.
Thanks
Ted
07-14-2012, 11:03 AM
#24
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Now get to suspension design:
Set dimensional and packaging constraints.
Get an idea on expected wheel travel window.
Get tire data
Set geometry limits, targets and main objectives.
Start design process. (hundreds of iterations)
When arrived with 3 – 4 geometry variants (normally 3 variants that do one specific thing slightly better while other areas are good enough and one that has no one particular advantage but every area is very close to best possible.) it’s time to put it through it’s paces.
Initially one would use simple path files simulating generic cornering loads. Than one would build a full simulation model that is driven by on track logged data. One of great things that Mitchells software does is allow to run your suspension model around the track where it will replicate every move based on suspension travel sensors data. Another great thing is that it can export this data in a form that can be used to run full weight transfer simulation model. I have some stuff in use – starting with V-grade and ending with hand written in excel software that I actually prefer to use. It’s more like in-house software packages that high level teams use to simulate and setup their weapons. There you can see how exactly wheel loads, wheel positions, ride heights, steering, etc., etc change when car model replicates its movement from actual track session. Than you can make changes to springs, shocks, corner weights and individual ride heights, arb’s, suspension geometry (anti dive, anti squat, jacking forces), aero maps, fuel load, etc., etc. Rerun the simulation and see how setup changes effect the car performance.
If you start with car from scratch (no previous logged data) and have no tire data than job still has to be done. One will have to work with approximations. I used end of last decade BTCC championship winning team on track data. Rear wheel drive and relatively similar power and weight characteristics. It’s still better than nothing.
It’s all written on less than a page but in reality in takes weeks and months of endless design/analyses iterations.
How can I add youtube video’s here???
Thanks
Ted
Set dimensional and packaging constraints.
Get an idea on expected wheel travel window.
Get tire data
Set geometry limits, targets and main objectives.
Start design process. (hundreds of iterations)
When arrived with 3 – 4 geometry variants (normally 3 variants that do one specific thing slightly better while other areas are good enough and one that has no one particular advantage but every area is very close to best possible.) it’s time to put it through it’s paces.
Initially one would use simple path files simulating generic cornering loads. Than one would build a full simulation model that is driven by on track logged data. One of great things that Mitchells software does is allow to run your suspension model around the track where it will replicate every move based on suspension travel sensors data. Another great thing is that it can export this data in a form that can be used to run full weight transfer simulation model. I have some stuff in use – starting with V-grade and ending with hand written in excel software that I actually prefer to use. It’s more like in-house software packages that high level teams use to simulate and setup their weapons. There you can see how exactly wheel loads, wheel positions, ride heights, steering, etc., etc change when car model replicates its movement from actual track session. Than you can make changes to springs, shocks, corner weights and individual ride heights, arb’s, suspension geometry (anti dive, anti squat, jacking forces), aero maps, fuel load, etc., etc. Rerun the simulation and see how setup changes effect the car performance.
If you start with car from scratch (no previous logged data) and have no tire data than job still has to be done. One will have to work with approximations. I used end of last decade BTCC championship winning team on track data. Rear wheel drive and relatively similar power and weight characteristics. It’s still better than nothing.
It’s all written on less than a page but in reality in takes weeks and months of endless design/analyses iterations.
How can I add youtube video’s here???
Thanks
Ted
07-14-2012, 03:47 PM
#25
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Just post the URL link.
For example...
www.youtube.com/.......
IT will post the video in the correct format
For example...
www.youtube.com/.......
IT will post the video in the correct format
