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Thread: 1st revision of 2015 rules released

  1. #71
    To get some data to support the craziness of the ETC rules, I went out in a production car and collected some data of basic parameters, including engine RPM, vehicle speed, longitudinal acceleration (measured), brake torque (calculated from pressure), throttle angle, and pedal voltage. This particular car was an automatic, naturally aspirated, all wheel drive.

    I found that, while I was able to get the car to -1G for over 0.5s (and -0.8g for approximately a second), at roughly 80% (gas) pedal input, the engine output torque target continued to follow the pedal in all cases (NO reduction in engine torque, at 1G deceleration and 80% pedal). The throttle remains approximately WOT, without any other torque reactions (let alone closing to the 9deg/10% specified in the FSAE rules). Power enrichment is active for much of this, as well.

    I'm also beginning to capture stuff like this on my daily driver car (turbo mtx), showing how much pedal input is needed while on the brake (not surprisingly, it's a lot).

    How do they seriously expect FSAE cars to downshift with 10% throttle? What about turbo cars? Why can't the driver stand on both pedals in preparation of a launch in accel (or any other event, for that matter)?
    Andrew Palardy
    Kettering University - Computer Engineering, FSAE, Clean Snowmobile Challenge
    Williams International - Commercial Turbofan Controls and Accessories

    "Sometimes, the elegant implementation is a function. Not a method. Not a class. Not a framework. Just a function." ~ John Carmack

    "Any sufficiently advanced technology is indistinguishable from magic" ~Arthur C. Clarke

  2. #72
    Senior Member
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    Nov 2010
    Location
    NSW, Australia
    Posts
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    Good point regarding downshifts. There are already enough bad drivers going 'chudder chudder chudder' into corners because they can't blip properly without forcing such things on those who can. Without a slipper clutch, failing to rev-match can be quite unsettling, and downright dangerous (especially on a bike).
    Jay

    UoW FSAE '07-'09

  3. #73
    Quote Originally Posted by Kevin Hayward View Post
    - 2011 was the previous big aero change, 2013 added Percy legs, and a host of small changes. These were also the years of alternative frames and then EV inclusion into the main rulebook."

    - The next 3 worst growth years were 2003, 2005, and 2009. I don't have the rules for 2003, but 2009 was the year chassis templates were introduced.
    Kev: I have been creating a bit of a database of comp results for analysis and just pulled out the number of forfeits and withdrawals from Michigan Comp which I thought could be interesting: (Cheers to who-ever in Michigan releases all the results in xls!, with weight, no. of cylinders, allows some interesting analysis)

    The number of withdrawals from Michigan seem to have a strong correlation to rules changes, 2009:template introduced, 2011: new aero rules, 2013: percy legs and other minor changes. Template changes seems to have had the greatest effect in recent years with 28 teams withdrawing or forfeiting their first year in effect


    The results don't appear to show the rule changes having an affect the finishing rate in Endurance which I thought they might. They fluctuate around an average of ~38% with no discernible relationship in rule change years. (FSG and MI, 2014-2006).
    Curtin Motorsport Team
    2011 - 2014

  4. #74
    can somebody tell me why does the turbo compressor has to be downstream of the restrictor. because last time i read that the choked mass flow rate is dependent on upstream pressure. so the compressor wont be doing any good by creating more vacuum downstream. instead now the restrictor will be choked at even lesser rpm because of higher VE which is a bad thing i suppose. or am i misunderstanding something ?

  5. #75
    Can someone help me interpret/visualize how this rule may/may not change the front bulkhead support from previous years? Anything will help:

    "[I]T3.20.2 The Front Bulkhead must be supported back to the Front Roll Hoop by a minimum of three Frame
    Members on each side of the vehicle; an upper member; lower member and diagonal brace to provide
    triangulation.
    a. The upper support member must be attached within 50mm (2) of the top surface of the Front
    Bulkhead, and attach to the Front Roll Hoop within a zone extending 100mm (4) above and
    50mm (2) below the Upper Side Impact member.
    b. The lower support member must be attached to the base of the Front Bulkhead and the base
    of the Front Roll Hoop.
    c. The diagonal brace must properly triangulate the upper and lower support members
    NOTE: Each of the above members can be multiple or bent tubes provided the requirements of T3.5.5
    are met"

    Thanks,

    Mike
    --
    Michael Hauptmann | Iowa State University
    Cyclone Racing | 2014-2015 Tech Director
    2013-'14, '14-'15 Chassis Team Leader

  6. #76
    Quote Originally Posted by apalrd View Post
    How do they seriously expect FSAE cars to downshift with 10% throttle? What about turbo cars? Why can't the driver stand on both pedals in preparation of a launch in accel (or any other event, for that matter)?
    How am I supposed to do smokey, smokey burnouts using 10% throttle?
    There's nothing that stops a cable throttle from using 100% throttle and brake input right now, why should ETC be limited? I think the burnouts might be incentive alone to use a cable throttle...



    ...on the serious side, this does disrupt some other maneuvers that affects cars with a clutch pedal such as blipping the throttle under braking as mentioned. There is no interlock to check for clutch actuation by the rules. And for all, "left foot braking" while still on the throttle to unsettle and balance the rear end as requested would not work.

    We're still working on the noise complaint to the rules committee so hold tight...
    Kettering University Vehicle Dynamics
    Formula SAE 2010 - 2015
    Clean Snowmobile Powertrain 2012 - 2015

    Boogityland 2015 - Present

  7. #77
    Quote Originally Posted by Khanjee View Post
    can somebody tell me why does the turbo compressor has to be downstream of the restrictor. because last time i read that the choked mass flow rate is dependent on upstream pressure. so the compressor wont be doing any good by creating more vacuum downstream. instead now the restrictor will be choked at even lesser rpm because of higher VE which is a bad thing i suppose. or am i misunderstanding something ?
    This rule makes perfect sense, actually.


    As you said, mass flow is dependent on upstream density (temperature and pressure), and flow velocity through the nozzle. The flow velocity through the nozzle hits a limit at mach 1, which corresponds to a pressure ratio of roughly 0.528 across the nozzle (off the top of my head and assuming temperature is fixed).

    So, in order for a restrictor to restrict effectively, the upstream air density and restrictor area must be fixed for all teams. Since the greatest air density possible is ambient air (of the ambient temperature and barometric pressure), and a poorly team-designed restrictive air filter/intake or pulling air from behind the radiator can only make things worse, it makes perfect sense for a fixed area restrictor to limit all teams at that competition to the same mass air flow.

    So, you do in fact need to create vacuum downstream of the restrictor to pull air through it (without a pressure difference, what will motivate the air to flow into the engine?). Once the pressure ratio across the restrictor hits 0.528, then stop pulling vacuum because the restrictor has reached choked flow.

    A turbo makes sense still, because it allows teams to hit choked flow continuously, at all (or the vast majority) of RPM points that the vehicle runs. A large engine (610cc) would reach choked flow at some rather high RPM, so above that point (in theory) the engine will follow a flat power curve and torque will drop off. So if you want to run a 300cc engine, you will never reach choked flow at any same RPM, but with boosting (turbo and supercharging), you can reach choked flow at all RPM points you use (assuming your 300cc engine can handle the peak cylinder pressures of running that much boost).

    It's up to you to decide if the added benefit of reaching choked flow at low RPMs is even worth it, due to traction or mechanical or whatever reasons. Or you might decide it's worth it to add a turbo simply because you can't meet noise any other way (which is a very valid reason with the 2015 rules).
    Andrew Palardy
    Kettering University - Computer Engineering, FSAE, Clean Snowmobile Challenge
    Williams International - Commercial Turbofan Controls and Accessories

    "Sometimes, the elegant implementation is a function. Not a method. Not a class. Not a framework. Just a function." ~ John Carmack

    "Any sufficiently advanced technology is indistinguishable from magic" ~Arthur C. Clarke

  8. #78
    Quote Originally Posted by mhaupt14 View Post
    Can someone help me interpret/visualize how this rule may/may not change the front bulkhead support from previous years? Anything will help:
    Mike,

    Here is the rule from the 2013 rulebook:

    T3.20.2 The Front Bulkhead must be supported back to the Front Roll Hoop by a minimum of three (3) Frame
    Members on each side of the vehicle with one at the top (within 50.8 mm (2 inches) of its top-most
    surface), one (1) at the bottom, and one (1) as a diagonal brace to provide triangulation.

    The only differences I read is they added specific places where the support tubes must join with other tubes. Other than that, I don't think it changed the support locations all that much.

  9. #79
    Senior Member
    Join Date
    Feb 2012
    Location
    Cincinnati, Ohio
    Posts
    117
    Quote Originally Posted by mhaupt14 View Post
    Can someone help me interpret/visualize how this rule may/may not change the front bulkhead support from previous years? Anything will help:

    "[I]T3.20.2 The Front Bulkhead must be supported back to the Front Roll Hoop by a minimum of three Frame
    Members on each side of the vehicle; an upper member; lower member and diagonal brace to provide
    triangulation.
    a. The upper support member must be attached within 50mm (2”) of the top surface of the Front
    Bulkhead, and attach to the Front Roll Hoop within a zone extending 100mm (4”) above and
    50mm (2”) below the Upper Side Impact member.
    b. The lower support member must be attached to the base of the Front Bulkhead and the base
    of the Front Roll Hoop.
    c. The diagonal brace must properly triangulate the upper and lower support members
    NOTE: Each of the above members can be multiple or bent tubes provided the requirements of T3.5.5
    are met"

    Thanks,

    Mike
    It seems to me like if your upper side impact tube is not within 4" of the top of your FRH, then your upper front bulkhead support tube will not be able to tie to the top of your FRH. This could drastically change the front end of the frame designs, as I don't think any of the frames that I built would meet this new rule...
    Matt Davis
    University of Cincinnati
    Bearcat Motorsports: 2012-2013: Suspension guy

    Bilstein: 2013 - ??: Product Engineer

    This post is a collection of my own thoughts and opinions, and in no way, shape or form reflects the thoughts/opinions of my company, my university or anyone else but myself.

  10. #80
    Quote Originally Posted by mdavis View Post
    It seems to me like if your upper side impact tube is not within 4" of the top of your FRH, then your upper front bulkhead support tube will not be able to tie to the top of your FRH. This could drastically change the front end of the frame designs, as I don't think any of the frames that I built would meet this new rule...
    This was my concern. I was unsure as to whether this was more of a rule change or simply a clarification. The front end design would then be more complicated if teams still chose to throw tubes from the top of the FBH to the top of the FRH and then their "upper Front bulkhead support" would have to be triangulated in accordance to the weird 45 degree triangulation rule back to the range around their Upper Side Impact Member.

    I feel, if a team wished to keep it simple (like most designs previously were), they would have a very odd looking front end being that most Upper Side Impact Members are much shorter than the FRH heights. This also may introduce awkward geometry in order to clear the leg template, and introduce problems for teams who mount their dampers and rockers on top of their frame in the front.

    Either this is the case, or I'm completely misunderstanding the rule... Again, any insight will help.

    Thanks,

    Mike
    --
    Michael Hauptmann | Iowa State University
    Cyclone Racing | 2014-2015 Tech Director
    2013-'14, '14-'15 Chassis Team Leader

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