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Thread: The Newbies Thread.

  1. #1
    I created this thread especially for new teams' progress such as ours. It should be concerned more with your work progress other than random questions in order to check if your work is in line with the rules and engineering fundamentals. Document what you write and use pictures and graphs when possible. Good luck to you and us too.

    We'll post our work soon. And if any one has an idea or comment about such thread please comment.
    Conveyor Systems Design Engineer - EgyRoll
    AUMotorsports Team Leader 09-10
    Alexandria University, Egypt.

  2. #2
    Many years ago, I wrote a guide for newbie FSAE teams. The document has been published in many places, so may well be known to teams.
    The document is a little dated and I should revise and update it. One day!

    It seems appropriate to post it here for those newbies who have not seen it.

    Pat’s guide for newbie FSAE teams

    This document is in no way an instruction sheet on how to design and build a car for Formula SAE or Formula Student. It is intended as an advisory document for new teams to allow them to build that all-important first car and avoid some of the more common pitfalls. It is very easy for a new team to get carried away trying to build their own complex ‘Formula One’ car and lose sight of the objective. To get to the competition with a car that will allow them to complete the event and gain the satisfaction of competing in the best engineering competition in the world is what it is all about.
    They will also get to leave the legacy of a complete project for those who come behind them to learn from or to evolve to the next level. It is important to realise that it is almost impossible to build a winning car at the first attempt, however it is all too easy to have no car for the competition due to being distracted along the way or having unattainable aspirations.
    My favourite saying is "The trick is ~ there is no trick", and that applies especially to FSAE. The laws of physics are immutable, and if something seems to be reacting in a different way to what you expect, that is a message that you need to better understand the question before trying to answer it.
    Usually though, you have to try an answer first before finding whether it is correct or not. That is when you run into my second favourite saying, "There is always more than one correct answer"! Your task then becomes finding the answer that best suits your situation.
    It is important for a team to realise that it does not matter whether the Judges agree with your design decisions or not, as long as you can cogently argue in favour of your solution. After all, the final examination occurs on the last day of competition on the track, and there your solution will be validated by the stopwatch.

    Design Suggestions

    For a first year car, I recommend that a new team opt for a simple and straightforward steel tube space-frame chassis. It should be fitted with a conventional suspension system that is easy to understand and sort. The choice of wheel size, either 10" or 13" diameter is the subject of ongoing debate. Both sizes have their advantages, however would recommend that a team think about starting with a 13" wheel as this will allow more latitude in the design of their suspension package.
    It cannot be over emphasised that the choice of tyres is the most significant decision made in the design process. Tyre choice is important because all forces of acceleration, turning and braking are reacted through the tyre contact patch.
    FSAE cars are limited, by the formula and course designs, to a top speed of little more than 100kph, so traction is generated by well-controlled tyre/track interface with little aero download assistance available. A team should finalise its tyre choice very early in the design process.
    Competitive cars have evolved a kind of sameness as a result of evolution. Teams pick the best features of preceding designs, either theirs or from another team. As a result, and applying Darwin’s theory, the good cars are starting to feature very similar designs.
    Overall designs may be similar, however, as the old saying goes, the devil is in the detail. Judges will look at the overall design, and whether they agree or not with the evolution theory, will then look closely at the details of your design and construction. So a new team would be well advised to choose a conservative evolutionary design for their first car and then really sweat the details.

    Planning

    Before anything is bought, before a sketch is made or a tube is cut, a detailed plan must be developed.
    If the tyres are the most important technical component, then planning and project management is the most important logistical component.
    The one thing all winning teams have in common is a good plan and a competent manager. The best piece of advice I can give the team manager is that this is not a personality contest. The ability to ‘see through’ the project and carry it out means that there will be differences of opinion between team members. This happens! A good team manager will take this in his stride, find a solution and continue to drive the project forward.
    An important aspect of the initial technical planning is ergonomics. The car will not be successful if it is difficult to drive. Your prototype is supposed to be for production and should in theory be adjustable so all and sundry can fit in and drive it. It also must fit ‘Percy’, the 95% manikin and accept the chassis templates. Realistically though, the only people it is required to fit are your team members, so the ergonomics should be designed around those drivers. Take look at a production-racing car such as a Formula Ford, and copy the ergonomic layout.
    Forget about the rest of that car design as it was built to a totally different set of parameters. Circuit race cars are optimised for straight-line performance and relatively open corners. The layout of the typical FSAE course will consist of tight corners of various shapes. There will be no real straight, and the top speed will be limited by course design to little more than 100kph.
    A successful FSAE car will therefore have exemplary handling characteristics, be predictable to drive and easy on its tyres. The constant reversal of forces, cornering, braking and acceleration will exact a toll on the driver and chassis as well as the tyres!
    With all this in mind, I will now talk about a set of design parameters suitable for a first time FSAE car.

    Basic Design Parameters

    I will start with a few design requirements. The car must meet all the requirements of the FSAE rules! This is not Formula One where you are free to interpret the rules as you please as long as you can afford very expensive lawyers to argue your case.
    The rules are simply written as they are, and the officials will not be swayed by your interpretive skills in reading these rules. If there are any doubts, refer the question to the organisers of the event you wish to attend for a ruling before you proceed!
    The rules also require some common sense interpretation. If there is anything dangerous about your car in the opinion of the judges, you simply will not be permitted to drive it, regardless of how ‘legal’ it may be.
    FSAE encourages the use and development of new technology. Sometimes this will bring forward technology not foreseen by the rules committee. An example of this in recent years was ‘fly by wire’ throttle and steering controls.
    An innovation may require a decision from the Rules Committee before the car is allowed to compete, and so any team contemplating some ‘avant garde’ design features would be well advised to bring them to the attention of the Rules Committee in plenty of time for a decision to be made, and any required alterations to the car completed and tested.
    Be assured the committee will maintain your confidences and will not leak your design features to another team.
    Finally, a car that looks good will always get a positive reaction from the judges, so concentrate on the details and make sure the car looks right. Judges like elegant engineering solutions, so the old truism that ‘Something that looks right usually is right’ has relevance here. Paint is cheap and elbow grease is free, but inspiration is priceless.

    Dynamics

    Front of the car

    The dynamic characteristics of the FS competition require a car that turns into corners accurately and maintains good cornering speed. Camber control when the chassis rolls is critical. Camber gain as the suspension compresses is desirable, but the designers should take into account the camber changing effects of Steering Axis Inclination and Caster as the car is steered. SAI results in a positive camber change as the wheel is steered. Caster will generate some negative camber on the loaded wheel on turn in. It follows that a good FS design has plenty of Caster and not much SAI.
    Running a car with lots of Caster will result in significant diagonal weight transfer when turning into a corner or at any time steering lock is applied. On turn in, this diagonal weight jacking will unload the inside rear wheel so a team running without a locking differential of some sort may suffer traction difficulties.
    On the other hand, this weight transfer may unload the inside rear wheel to such a degree that a differential may be dispensed with as in go-kart designs. Steering feel and weight as a result of caster angles can be adjusted by altering the ?trail?. Trail is the position of the axle centerline relative to the steering axis. Altering trail will change the transverse weight transfer whilst not affecting the camber angle change.
    A little positive steering offset will give good feedback to the driver, too much will quickly wear him out and may even hurt his hands from kickback in the event of contact. Too little offset may make it difficult for the driver to place the car due to lack of feel. A balance may need to be struck between wheel offset and SAI to achieve good steering ‘feel’.
    ‘Bump Steer’ should be avoided over the range of suspension travel. Any decision affecting rack position, Ackerman etc, should immediately be checked for any bump steer side effect.
    Positive Ackerman geometry will result in an increase in toe out when the steering is turned away from straight ahead. Negative Ackerman is usually only seen on cars that encounter very high-speed corners and where aerodynamic stability in those corners is paramount.
    Does it follow that low speed cars on a tight track need positive Ackerman? You bet it does! And it is unlikely the amount of Ackerman you think you need will be enough. Increase it by at least 50% and you might be in the ballpark! Be aware that the position of the steering rack will alter the Ackerman effect, and some teams actually ‘tune’ their toe out on turns with an adjustable rack position.
    Camber on a FSAE car should never go positive on a loaded wheel in cornering. Judges will watch for this, and I have actually seen a judge accurately predict the SAI and Caster angles on a car by watching it on the track.
    Rolling a loaded tyre onto its outer edge will not only reduce the grip, but will quickly ruin the tyre. Excess negative camber is not so damaging. Generally, radial ply tyres respond to more negative camber than cross ply tyres and are more forgiving.
    Designers should be familiar with the effects of Camber thrust, the tendency of a tyre to run towards the positive camber angle. Cars that spend a relatively long time travelling in a straight line may have their toe angles adjusted to reduce the scrub losses induced by Camber Thrust, but on a FS car this effect can effectively be ignored.
    Stiff suspension rates, aggressive ’anti dive’ and ‘anti squat’ geometry and ‘third springs’ are usually seen to best advantage on cars where control of the aerodynamic platform is paramount. More compliant suspension rates are better suited to FSAE cars and will enhance the mechanical grip as long the wheel angles are controlled.
    Excessive dive under brakes can be controlled with a third spring or bump stop, but rearward weight transfer under acceleration may well be advantageous. Excessive amounts of Anti-dive geometry in the front suspension may result in a very ‘wooden’ feedback to the driver, and so should be avoided.
    Compliant suspension may result in changes of roll centres, both vertically and laterally as the suspension works. A mobile roll axis will send confusing feedback to the driver, making accurate control difficult. Judges are aware of this and will quiz the design team on the dynamic positions of the roll centres and roll axes. Pay attention to the migration of the roll centres under all conditions.
    A low roll axis and compliant springing may require the fitting of anti roll bars, and it is important to understand the side effects of the transverse weight transfer of these devices. In any effect, ARBs are a good way to fine-tune a car for various circuits and conditions. Whether a team decides to fit ARBs to their car or to omit them, they can expect to be quizzed on this issue by the Judges.
    A powerful force generated in a FS car is front wheel brake torque. Care should be taken to properly react this force into the chassis, avoiding steering changes or ‘tramp’?.

    Rear of the car

    At the rear of the car the forces are different but the basics are the same. Toe control is important so aim to have a wide toe control base.
    Try to avoid bump or roll steer, both of which may make the car undriveable in the heat of competition. Bump steer toe out will make the car very unstable on turn in.
    Drive shafts and CV joints should be aligned in all planes when the car is loaded. Provision should be made to accommodate drive shaft ?plunge? as the suspension works. Tripod joints are probably the best choice.
    Thought should be given to the rear brake arrangement relative to the differential type used. A single inboard brake may be used, but this will not be effective if the differential type does match this type of brake arrangement. Judges will quiz you on this! If outboard brakes are used, care must be taken to ensure the brake torque is properly reacted into the frame.
    Locked or locking differentials usually contribute to the generation of understeer, the bugbear of FS car handling. This can be relieved to a degree with proper understanding and implementation of the diagonal weight transfer discussed when talking about the front of the car.

    Safety

    There are stringent safety requirements written into the FS rules, and you can rest assured there will be no relaxation of these standards by scrutineers or officials. You should be aware that these rules do not necessarily cover every area of every car, and the judges may well disallow a car on safety grounds because of some feature that is not covered in the rules. This is for your own safety as well as their ?Duty of Care? under law.
    At all times during the design, build and preparation of the car, ask yourself "Would I like to be driving this if something goes wrong?". If something seems like a good idea safety wise, then it probably is. If there is ever any doubt give the Committee a call and they will help you through the process.
    Although ’anti-intrusion’ bars are not mandated on suspension A arms, I would recommend them. A relatively minor bump can push the A arm into the driver’s space and injure his feet or legs.

    Basic Design Checklist
    1. All load-paths should be direct and obvious to the judges. Judges love isosceles triangles and hate voids and indirect load-paths.
    2. Never load a threaded rod end in bending. Apart from it being poor design, Judges hate this and hate seeing it again and again year after year.
    3. Chassis stiffness should be such that the suspension can effectively work. If the suspension spring rate is such that the chassis flex becomes the de facto suspension, all your calculations go out the window, rapidly followed by handling and road holding.
    4. Weight is bad! Remember the immortal words of the late Colin Chapman, "Add lightness and simplificate". (By the way, Mr Chapman also said "Any suspension will work if you don’t let it"…but Judges watch out for that!)
    5. Cars with aggressive caster angles are self-adjusting with regard to corner weights. Therefore it is an absolute waste of time attempting to adjust corner weights unless the chassis is square, in proper alignment, on a flat and level surface and with tyre diameters equal front and rear.
    6. Push rod or pull rod suspension is a good idea for the following reasons.
    • It is possible to adjust the ride height or chassis attitude without altering spring preload, and vice versa.
    • By using a rod and bellcrank operation of the suspension components, the motion ratio can be increased to permit more effective damper travel for minor wheel movements.
    • Unsprung weight may be decreased and the mass of the suspension components can be located to lower the CG.
    7. Never forget it is ‘Wheel rate’ that is important, not ‘Spring rate’. Work out a simple mathematical equation for the wheel/spring travel ratio to allow easy calculation of the effects of spring or bellcrank ratio changes. Beware of bellcranks with aggressive multiplication ratios as these make the car very sensitive to minor adjustments.
    8. Roll control devices (ARBs) are a good idea. If not needed they can always be disconnected, however, such devices are invaluable for fine-tuning the handling to suit track or weather conditions.
    9. Ensure there is an adequate toe control base at the rear of the car, and that the components are stiff enough to prevent unwanted dynamic toe change. The judges will check for this using the old-fashioned ?Manual Labour? method.
    10. Things will flex under load, therefore it is a good idea to use spherical bearings at both ends of all suspension units.
    11. You will not be permitted to compete with a noisy muffler. Noise can be a difficult thing to measure, so a good safety margin is recommended. The muffler is not a good place to save weight!
    12. Under stress it is incredible how much pressure a frightened driver can apply to the brake pedal. Judges will look for flexing in the pedal mountings. The brake pedal should not go over-centre when the brakes are applied. Ideally, at full application the pedal should be just before a perpendicular load is applied to the push rod. Judges will also look for proper operation of the brake balance bar or for one master cylinder bottoming out and the full effort then being transferred to the other.
    13. Test, test and test some more. Plan to have your car built in plenty of time to allow testing. Things will break, and the competition is not the place for that to happen. This is part of the management plan we spoke about earlier. It is a critical element for successful teams.
    In the mean time, all potential drivers should get as much seat time in go-karts as is practicable. Not only will this give the drivers experience; it will permit the team manager to choose the best potential drivers. It also is a good team building exercise, and can even be used as a fund raising exercise.

    Finally

    Remember this is a learning experience, not a motor racing event. Sure, we all look forward to driving and the final competition, but the real winners are the competitors who learn something. Time and time you will hear bystanders, judges etc remark, "I wish there had been something like this when I was at Uni". They all see the benefits as well as the enjoyment. It rounds out your education, whether it is in engineering, electronics, management, marketing or any of the other disciplines pertinent to the competition. It is a killer achievement to put in your CV, and will greatly enhance your employment opportunities.
    Do not lose sight of the big picture and the opportunities the competition and its sponsors have given you.


    Hopefully, this is a good way to start RollingCamel's 'newbee' thread.

    Cheers
    Pat
    The trick is ... There is no trick!

  3. #3
    Excellent!!
    Conveyor Systems Design Engineer - EgyRoll
    AUMotorsports Team Leader 09-10
    Alexandria University, Egypt.

  4. #4
    Front and rear suspension documentation:
    Note: This design was made as an exercise in order to know how to draw suspension geometry. The chassis and suspension will be changed due to our assumptions. The CG position was ignored currently but will be introduced, thus the Anti-Dive and Anti-Squat geometry is nonsense.
    Constraints:
    1. Wheelbase >= 1525
    2. Smaller track >= 0.75 Large track
    3. Minimum wheel travel >= 50.8mm (25.4 mm jounce and 25.4mm rebound)
    4. Wheels Diameter >= 203.2mm (8”)
    5. Ground Clearance >=25.4mm (1”)

    Parameters:
    • Wheelbase = 1675mm
    • Front Track = 1300
    • Rear Track = 1100
    • Unequal length double wishbone (SLA)
    • 13” wheels and tyres.
    • Tyre diameter = 508mm
    • Tyre Width = 172mm
    • Wheel inner diameter = 319.311mm
    • Ground clearance at static load = 45 mm


    Front Suspension Parameters:

    • Caster Angle = 3 degrees
    • Kingpin inclination = 3 degrees
    • Scrub Radius = 51.463 mm
    • Static Camber= -2 degrees
    • SAL = 1502
    • Roll center position = 3mm below ground
    • Still no toe





    Rear Suspension Parameters:
    • No caster angle for now.
    • Kingpin inclination = 1.62 degrees
    • Scrub Radius = 60.466 mm
    • Static Camber= -2 degrees
    • SAL = 1164
    • Roll center position = 5 mm above ground
    • Still no toe




    Notes:
    • SLA suspension was used due to its great flexibility and simplicity.
    • According to Allin Staniforth from “Competition Car Suspension” Swing axle lengths:
    o Short SAL (20-40 inches) gives very good roll center location, keeps the outer wheel vertical in corners, but going badly to positive camber in drop and negative in bump (acceleration squat and braking).
    o Lang SAL (70-180inches) provides lower roll centers but less control over their sideways movement, minimal scrub (track variation), poor outer wheel control going into positive camber, but only small camber change in bump / droop.
    o Medium SAL (40-70 inches) mixed between short and long SAL.
    o Ultra-long SAL (near parallel) Provides excellent vertical control of very low roll centers but possible enormous sideways movement, wheel angles virtually unaltered in bump / droop but very poor control of wheels in roll, with near equivalency to body roll.
    We chose to try medium SAL and see the results.
    • Suspension geometry was drawn based on “Race car Vehicle Dynamics”, Millikin.
    • Steering geometry still in the works and we are having difficult time interpreting “Kingpin Axis at Tie Rod Outer Ball Joint Height”.


    • The push or pull rod geometry design guy will start soon.
    • I have inserted these parameters Lotus Suspension, but not have the weight, push rod geometry and steering geometry right means that we are quite limited with what we got.

    Camber Angle vs. Bump and Rebound of 30mm. (front)
    30 -3.1264
    25 -2.93327
    20 -2.74236
    15 -2.55362
    10 -2.36702
    5 -2.1825
    0 -2.00003
    -5 -1.81957
    -10 -1.64108
    -15 -1.46454
    -20 -1.28993
    -25 -1.11721
    -30 -0.94636

    Roll center location Relative to ground. (front)
    30 -52.3035
    25 -44.6434
    20 -37.0076
    15 -29.3952
    10 -21.8054
    5 -14.2375
    0 -6.69068
    -5 0.835669
    -10 8.342203
    -15 15.82953
    -20 23.29822
    -25 30.74879
    -30 38.18176

    I'm quite tired and should go sleep. Again this was an exercise rather than a real design, so plz excuse me of any mistake.

    Chassis part will follow but here is a pic of it.
    Last edited by RollingCamel; 04-15-2020 at 10:17 AM.

  5. #5
    Your front cockpit cross section template isn't in the right position, it's supposed to be parallel to the front plane, read the rules again
    -----------------------------------
    Drivetrain Leader 07-08
    Technical Director 08-09
    Team FSAE USB - Caracas - Venezuela.



  6. #6
    Is the top of your main roll hoop bracing within 6.3in of the top of the main roll hoop? Based on the location of Percy's head it might be a little low.

    And +1 on the orientation of the front cockpit template.
    ______________________
    Iowa State Univeristy FSAE Alumni
    http://www.sae.stuorg.iastate.edu/?page_id=144


  7. #7
    Originally posted by t21jj:
    Is the top of your main roll hoop bracing within 6.3in of the top of the main roll hoop? Based on the location of Percy's head it might be a little low.

    And +1 on the orientation of the front cockpit template.
    Initially we had it vertical but some members debated their interpretation of its orientation and with the "up...up" on the fig 9.

    And for the bracing position good notice. The dimension of 160mm was set in 2D but somehow i inserted it on the center of the arc not its tip. Hmm....The team has to revise each other more.

    Thanks for the comments guys.

    PS. What was about moving up and down while moving forward in the faq?
    Is there videos about the inspection in competition?
    Plus why there is not something like FSAE TV? to record the events' procedures and some judging?
    Conveyor Systems Design Engineer - EgyRoll
    AUMotorsports Team Leader 09-10
    Alexandria University, Egypt.

  8. #8
    Senior Member
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    Hey, a good, intelligent discussion of design by a new team. We're all very glad to help you guys out.

    You're not like the guys who ask "how do I design differential?!?"

  9. #9
    All new teams, please take note. This is how to ask a question about design and get a response. RollingCamel has already done his research, already done some engineering, and is now asking for a critique of his work. Now if only I knew more past what all those names mean to give you a hand.

    I know this will seem like an odd thing to point out, but I am an engine guy and its what I do. Watch how much room you have left between your exhaust ports/head and the firewall under the new thermal rules that have been introduced. You probably want to make sure you can actually fit an exhaust in there. Seems obvious, but its integration stuff like that that I have seen been overlooked by newer teams/members.
    Chris Noll
    UB Motorsports Formula SAE: RIP 1987-2010

    "A turbo: exhaust gasses go into the turbocharger and spin it, witchcraft happens and you go faster."- Jeremy Clarkson

  10. #10
    Originally posted by Hector:
    Hey, a good, intelligent discussion of design by a new team. We're all very glad to help you guys out.

    You're not like the guys who ask "how do I design differential?!?"
    Thanks for the complement but i think i realize something. This is our graduation project so we are quite experienced with basic mechanical experience. I think it could've been different if i joined a FSAE project on my first year or second. Not taught enough mechanical design and understanding the market and real world would result such questions.
    I do pitty young members and i wish that i joined FSAE since then cause as a suspension guy i want to make several designs and test them to know and feel the difference to get more understanding rather than scrambling just "to do it".
    As said before, it should better for new team to let the team captain to filter and post their questions.
    Conveyor Systems Design Engineer - EgyRoll
    AUMotorsports Team Leader 09-10
    Alexandria University, Egypt.

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