Rules Enquiries: Q&A


This page provides a list of questions received by the Formula SAE-Australasia Rules Committee, along with the corresponding answer.

 

Question

 

Answer

DUAL FUEL INJECTION: Since there is no mention of dual stage injection in the rules, we were wondering if it is allowed to use engines with such capabilities. For example, our selected engine is Honda CBR 600 2009 which uses a dual stage injection system and in addition to the 4 injectors that inject the fuel into the cylinder head, another 4 inject fuel into the intake manifold. In response to your recent enquiry regarding Fuel Injection Systems, Dual Stage, or dual injector location, systems are permitted.  If the system is wholly a Low Pressure System it must meet all of the requirements of Clause IC1.91 or, if High Pressure or Direct Injection, the requirements of Clause IC1.9.2.    If the system is a hybrid of Low and High Pressure, then all requirements of both clauses must be met.
FUEL LINE CLAMPING: Attached is a picture of the OEM fuel rail on which our fuel lines are to be clamped, we were wondering whether or not this fuel rail fuel entry satisfies the condition of being barbed or not. Furthermore, are the clamps whose picture is attached in the enquiry satisfies the three conditions of required clamps per this rule or not.

With respect to your recent query relating to acceptable fittings and clamps for fuel lines, the spigot with the exterior circular beads qualify as satisfying the barbed or bulb requirement, provided the tube is clamped between the two raised beads.A wire clamp would definitely cut into a hose and therefore the double wire clamp you show is unacceptable.A flat band clamp with rolled edges is what is expected. Examples are shown on the USA FSAE website Frequently Asked Questions.
GRADE 8.8 BOLT REQUIREMENTS: Does an OE combination satisfy the conditions listed in rule number T11.1.1. The stud is not 8.8 grade bolt and we have difficulty understanding the extend of the mentioned rule to whether or not the bolts used to attach the wheels to the hub must be 8.8 grade. Furthermore, does the fact that they are flat head contradicts with rule number T11.1.2 or not? The Fastener requirements in clause section T11.1 relate to the Metric Class and head type for nuts and bolts used to retain clevises, hubs, uprights, wishbones etc. They do not apply to the pressed in wheel studs and where OE wheel studs/lug nuts would be satisfactory.  The example shown would appear to be more than adequate for a Formula type vehicle.


Li BATTERIES FUSING IN IC CARS: In regards to the regulations on the use of Batteries based on Lithium Chemistry & specifically the Discharge current cut off switch: I have been unable to locate a battery on the market with a built in cut out for high discharge. The battery we are proposing to use has high and low voltage protection. Is the voltage cut off enough to satisfy safety concerns or is a Fuse in the line is required. The battery proposed (SSB Power Sport LH7B-4-GK) is rated to 150A discharge and has a cut of 8.2 Volts. In response to your query regarding the protection for Lithium batteries in the rules, a fuse or other overcurrent protection is required.  The low voltage cut- off does not satisfy the requirement for which the overcurrent protection is intended and is to protect not just for thermal runaway but more to protect the wiring/personnel.  Lithium Ion batteries of all chemistries have a significantly higher short circuit current than lead acid, and are likely to be in the range of thousands of amps.



ACCUMULATOR HOLES PROTECTION: Ducts are being added to our accumulator for cooling. They are made of non-conductive material and are in contact with the cells and accumulator walls, however the smallest duct (shown) is 60mm from cell to wall. There is no opportunity for anyone to contact the Tractive Path of the system. Does the current design meet the intent of the rules?




The intention of rule EV4.5.1 is to prevent accidental contact of fingers or tools to live parts of the accumulator, either with the car assembled, or during maintenance. You should also consider the insulation on the battery pack itself. If you are able to demonstrate that the insulation on the battery pack itself is adequate for the full tractive system voltage, and a probe cannot be inserted from the exterior to contact the cells or internal HV items, then your design should be compliant. You should be able to check this for yourselves with a sample probe.  If either the insulation on the cells is not suitable for your full pack voltage, or contact can be made with the probe, you should consider adding additional insulation or an  additional means of preventing the insertion of the test probe.
ELECTRIC MOTORS LOCATION & PROTECTION: The team wished to apply the Wheel Mounted motor exemption for a motor mounted in an exposed position outside the main frame.



The intent of this rule EV 4.2.3 was to allow wheel embedded motors without the obvious incompatibility with frame protection. Apart from ensuring adequate electrical disconnection protection for your motor, the mounting must also fully comply with EV4.2.2 with surrounding tubular structure per T3.4.  It appears that your motor is mounted in a position subject to this rule but no surrounding structure is shown, as will be required.
GROUND PROTECTION FOR WIRING & FUEL LINES: Given that the triangulated lower face of our monocoque, will not impact the ground under any circumstances. Will routing brake lines and LV wiring through this area satisfy rule T7.1.7? The intention of rule T7.1.7 is to protect the electrical and brake hardware on the vehicle from impacts, both from the ground and from foreign bodies. As the exposed equipment will still be susceptible to damage from foreign bodies, the proposal is not acceptable.

HV CONNECTOR CLAMPING: On our cell stack PCB, we are using a Radlok connector. This connector is fastened to the PCB by an M6 cone lock nut, one of the material layers of the PCB is an FR-4 standard fire retardant composite material. Given the strength of this material is this considered to be compressible and therefore not meet rule EV4.5.8? PCBs being made of fiberglass are considered to be compressible and so are not allowed to be included in a bolted high current path connection. This is because once compressed, the resin can gradually flow, causing a relaxation of the joint. Note also, nyloc nuts are not suitable for securing high current connections, as the nylon has a relatively low softening temperature, making them ineffective when the joints get hot.
ACCUMULATOR MOUNTING DESIGN: The mounting point makes use of an 8mm Metric Grade 8.8 stud to fasten the accumulator to the car. Due to the inherently unserviceable nature of studs, the use of a slot in plate has been conceptualised. The plate must be located with other fasteners to both react the torque of the stud and to locate the plate longitudinally during the fastening of the accompanying M8 nut.The smaller fasteners serve only for locating and torque reacting purposes. They are not intended to carry any impact load.  Does the use of smaller-than M8 fasteners to locate this bracket contravene EV3.4.8 c ii?
The proposed arrangement as shown in your component drawing appears not to be acceptable as a replacement for the required M8 mounting bolts. Per Clause 3.4.8 c The mounting must “Be able to withstand 20kN in any direction” and thus are intended to secure the battery box in 3 dimensions against forces generated during an impact or possible rollover event. As presented, the pins indicated in your design would provide adequate restraint in 1 or 2 dimensions only so are not an adequate replacement for the required bolts.




ACCUMULATOR COOLING LIQUIDS: For accumulator cooling is silicone oil permitted given it is defined as an oil?  We’re attempting to implement an active cooling system for our accumulator and require a dielectric heat transfer material with a viscosity similar to water. This is the safest material we have found to meet our needs.










By the Safety Data Sheet, the material is classified flammability level 2 “moderate”. Despite the rules requirements that the battery pack be operated at or below 60 degrees C, there will be insufficient margin between the operating temperature and the flash point of the fluid. There are likely to be localized hot spots within the pack, so it is possible that flammable gasses could accumulate in the air spaces within your battery pack. Due to the high energy content of the battery pack, it will not be possible to demonstrate that ignition sources are not present within the battery, so the fluid must be assumed to be unsafe for this purpose. As there are currently no rules specifically governing cooling fluids for battery packs, the rules committee suggests the following for guidance:
- The fluid should be non-flammable, or at least self-extinguishing
- The fluid should be stable at any temperatures up to at least 90 degrees C to prevent localized boiling or off gassing
- The fluid should not be listed as dangerous goods
BENT TUBE SUPPORT: Per T3.5.5; If the bent tube in question is the upper side impact member, is this it required to have a support tube of the same diameter and thickness (1.375’’ x 0.047’’) as stated in the rule above or is this already accounted for in the increased diameter of the tube?
If your Upper Side Impact tube is bent, then it must have at least one tube of the same diameter and thickness running from where the furthest deviation due to the bend is located back to a node on the chassis.  If of the correct dimensions, a tube running from the centre of your USI tube back to the node at either the base of the Main Roll Hoop or Front Roll Hoop would meet this requirement.
EV OVERCURRENT PROTECTION - 1/3 RULE: We would like to ask clarification for the first item in rule EV6.1.5. Specifically, requiring a “three time lower” requirement on the external overcurrent protection device? If we put 7 cylindrical cells (where each cell has 2 fusible links, rated at 22.5A each) in parallel and form a battery block. Then we connect 110 of these cell blocks in series to form the accumulator pack. The sum of parallel fusible links rate will be 22.5 * 2 * 7 = 315A, does this mean we have to connect in series an external fuse with a rating lower than 105A?



You are correct in your assumption that a fuse rated at 105 Amps or less will be required to protect the battery pack in that configuration. The 3x rule (EV6.1.5.1) is an attempt to make sure that 2 scenarios don’t happen; A: If a single fusible link blows there is time for the AMS to detect it and shutdown the vehicle and we don’t have a chain reaction where as soon as one link blows the rest blow because the remaining set of fuses has an overall smaller ampacity) and B: If the entire pack is subject to an over-current the main pack fuse which is rated for full TS voltage blows before the parallel cell fuses which are not voltage rated. Given the different shapes of the time current curves, the 3x factor was adopted as a reasonable way to have a simple requirement for the teams to follow but make sure we keep adequate spacing at all points on the time current curve between the main pack fuse and the cell fuses.
SHUTDOWN BUTTON ELECTRIC SYMBOL: Can you provide us a close picture of the button or model name of the button mentioned in EV5.3.4? I was unable to find the button with a red spark on a white-edged blue triangle.
You appear to have misunderstood the rule. It does not require the Shut Down Button to carry the symbol but it be clearly located adjacent to the button.  You could draw and produce your own symbol or they can be located on line.

HEADREST PADDING DIMENSIONS: Rule T5.6.2.  Does this rule require the energy absorbing foam to be a minimum of 1.5 inches thick or is the rule only requiring the assembled thickness of the restraint to be a minimum of 1.5 inches thick?
The foam padding must be a minimum thickness of 38 mm.   If the dimension were applied to the total head restraint, inadequate thicknesses of foam could result.

 
FRONT RADII ON WING SECTIONS: Rule T9.5 & T9.5.1. 1. Does this rule assume the front radius of aerodynamic devices in a ‘normally operating’ configuration i.e. the running configuration of the vehicle?  2. How will front radii be measured given the radius of an aerofoil is constantly changing?  3. Will the secondary flap of a front wing and by extension any other forward facing aerodynamic device be measured? All forward facing edges are potentially contactable by a pedestrian so must comply unless protected by a grille or some other guarding.  The radius could be measured in any operating position so if devices are adjustable, your design must ensure compliance throughout the range of movement.



SES QUERY: T3.19/T3.32: SES Query; T3.19/T3.32.   The UTSS (N)” in the FBH Support Structure fails SES. The guidance notes within the SES gives an alternate method to prove the equivalence provided that the value is >33%. Do we need to provide equivalent calculations for: 1. ONLY “UTS (N)” because that is the only criteria we fail, or  2. All the three properties “Moment of Inertia”, “Buckling Modulus”, “UTS (N)” 
TBA #27







FIRST YEAR VEHICLE DEFINITION: A6.8.  First Year Vehicles: In the 2017 competition, a car was run with a chassis that was mostly aluminium honey comb monocoque with a steel space frame rear section. For the 2018 competition, if the front monocoque section is significantly redesigned but we reuse the rear section with minor modifications of brackets, suspension mounts and engine mounts, will the vehicle be classified as a first-year car?
Provided the front monocoque is significantly different, plus there are some modifications to the rear structure and not a carryover rear suspension, the vehicle will be accepted as 1st Year Car.  You may not gain the maximum points in Design because of the lack of new design approach to the rear structure. 




WHAT IS "BRAKING HARD": EV5.6 Brake System Plausibility Device (BSPD). 1.Can you please give a clearer definition of “braking hard”? Is there a certain pressure value at which we consider as braking hard? 2. Regarding the following section: “The action of opening the AIRs must occur if the implausibility is persistent for more than 0.5 sec.” Does it mean we need to open the AIR within 0.5sec after the BSPD fault is detected?





The pressure required to be considered ‘braking hard’ needs to be determined by the team as it is dependent on the design of the braking system. It should be close to the point of locking the wheels. At technical scrutineering the scrutineer will select one of your drivers (usually the smallest) and ask them to demonstrate that they are strong enough to active the protection system. As such, you should seek to strike a balance between too high a braking force that the drivers cannot active the system in an actual emergency and too low where it causes nuisance trips. The action of opening the AIRs must occur if the implausibility is persistent for more than 0.5 sec.” should be taken to mean that the driver panics and depresses the brake pedal hard, the AIR must trip. It is allowable for you to have a timer which checks for a consistent brake press for up to 0.5 seconds before tripping to reduce nuisance trips.
EV; SUPPLY OF POWER FROM TSMS: Rule EV4.11.2 requires any pre-charge circuitry must be supplied directly from the TSMS. 1. Can AIR be supplied by 12V voltage line before the TSMS?  
It is a requirement that the actual current flowing through the AIRs passes through the TSMS, such that when the TSMS key is removed the current path to the AIRs is physically broken. As such the arrangement suggested is not acceptable.
LV FAN INSTALLED IN ACCUMULATOR: Rules EV 4.1.4 & EV 4.1.5:    We are designing a cooling system in the accumulator container which involves fan in the accumulator. We would like to clarify if fans are allowed in the accumulator container if they are powered by the LV battery but galvanically isolated.
LV equipment within the battery container should be avoided wherever possible. If an LV system must be installed within the battery compartment it must be galvanically isolated from the chassis and be physically protected from the tractive system by either an insulating barrier or the defined air gap.

MONOCOQUE MAIN ROLL HOOP MOUNTING: Regarding Rule T3.34.2  Given the rule states the hoop must be attached at the top, and the bottom, and at an intermediate location: are three attachment points required on each side to attach a main hoop to a monocoque chassis, as shown in the following diagram?


Your interpretation of the rule T3.4.2 is a correct interpretation of the intent of the rule. A tube frame structure would usually have three welded mounts; one at the top of the body structure; another at the Upper Side Impact Tube; and one at the bottom of the  body structure.The drawing you included showing mounts at the top, bottom and adjacent to the height of the USI tube would be in full compliance. This rule will be clarified in the 2019 US FSAE Rules and/or 2019 Local Addendum.
SES QUERY; EV 3.4.6 ALT MAT'L EQUIVALENCY: SES. EV 3.4.6 Alt Material - Shear. Given the inherent advantage of being able to tailor the mechanical properties of a composite materials to suit an application, does the required “proof of equivalency” dictate the entire alternative material panel must meet the same shear strength as the steel baseline or is there scope to meet shear equivalency only in regions where such shear strength is required?
TBA #35








FASTENER EDGE DISTANCE: 
Regarding Rule T11.1.3  Does the second bolt hole on the same bracket (and therefore the chassis) count as a free edge?
The edge distance is intended to be the distance from any bolt hole within the mounting plate/reinforcement to a neighbouring free edge of the monocoque. The distance to an additional bolt hole within the mounting plate/reinforcement itself may be less than this dimension.
SES Query: EV3.4.6 Alt Matl – Shear 
Alternate Frame Accumulator Container Perimeter Shear Test

Given the inherent advantage of being able to tailor the mechanical properties of a composite materials to suit an application, does the required “proof of equivalency” dictate the entire alternative material panel must meet the same shear strength as the steel baseline or is there scope to meet shear equivalency only in regions where such shear strength is required?

Similar to how monocoque structures only need to show equivalent shear strength within the front bulkhead support and side impact structures, and how hard points are expected where necessary to distribute loads through the panel.

With regard to equivalence of a composite material accumulator container to steel and if the equivalence requirement applied to the complete panel surface, we advise that it must be equivalent to 0.09/1.25 mm thick steel over the whole panel surface area, not just at load bearing points.

Steel also provides localised impact/penetration protection for the Li batteries over the whole panel surface, therefore the composite must be equivalent to the nominated thickness steel over the full area.

Electronic Throttle Control 
What is the meaning of “Notice of Intent to use deadline” on Electronic Throttle Control (ETC)? We are confused with the deadline for ETC on 14 Sept for IC vehicles.

 

The Notice of Intent is a specific form available on the US FSAE website and is as required per the rules. This is all clearly spelled out in Clauses IC1.11 through IC1.18 and their related sub-clauses. It must be agreed to by the officials in advance for you to be allowed to use an ETC. The September 14 date is for the submission of the FMEA. Very few teams attempt to use ETC and we would recommend that any new team not attempt to adopt ETC in their early years.

Head Restraint Width 

Rule Reference T5.6.2 c.  Does the total head restraint width have to be greater than 15cm or can the head restraint at one point be less than this?


The width of the head restraint must be a minimum of 150 cm over the complete restraint if an adjustable restraint, or over the full minimum height of 28 cm for a fixed restraint. A fixed restraint of greater than 28 cm height could have the width reduced outside the 28 cm height.
BMS Outside the Accumulator
We want to confirm if it is allowed to have the BMS outside the accumulator container. We are using a 132 cells model Orion BMS 2. It is equipped with 2.5kV isolation for every 36 cells and 100V isolation for every 12 cells.
It is the intention of the rules that when the AIRs are open, no tractive system voltage should be present outside of the accumulator enclosure. 
Wires in Accumulator Container

EV4.5.11 Wiring that is not part of the tractive system must not use orange wiring or conduit.

EV3.3.8 Every wire used in an accumulator container, no matter whether it is part of the GLV or tractive system, must be rated to the maximum tractive system voltage.

GLV wiring colour, Per EV 4.5.1, even inside the accumulator container, orange wiring may not be used for GLV wiring which is not part of the tractive system.


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