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Thread: FSAE Australasia 2018

  1. #21
    Quote Originally Posted by Z View Post
    Noah,

    "Was the Monash E-car 4wd or was it just a rwd monster with an emrax?"

    The Monash E-car #65 is in many ways the real standout of this competition.

    I say this because its on-paper spec is reminiscent of a bottom-of-the-ladder team's rough-n-ready attempt to enter the E-division, by taking their last year's (overweight) C-car, tossing the C-engine, replacing it with a biggish battery-pack, and then bolting a single Emrax (228?) BEHIND the rear-axle-line, with a chain-drive going forward to a spool. And, indeed, this is pretty much what Monash have done, quite openly, and with the aim of getting their two C and E-cars built as quickly and cheaply as possible.

    The "standout" part is how fast this Monash E-car is on track. It really does show that a car can have outstandingly good performance on track even when it is nowhere near as "optimized" as most students think it must be. Much kudos to Monash for being brave enough to take this seemingly "low-tech" approach. Especially so, when you consider that Monash have a high reputation to uphold, and going "low-tech" could have ended up being very embarrassing for them.
    ~o0o~


    Z
    Really hurts to read because that is what Cal Poly attempted to achieve the past few years but never quite got all the pieces together for race day. At least it's validating in a way that someone else was able to succeed with that strategy.
    Noah
    Student

  2. #22
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    I'm surprised it isn't done more often. Start simple, make that good, then make it complicated. Crazy to do it the other way...
    ex-UWA Motorsport

    General team member 2013-15, Vehicle Dynamics Team Lead 2012
    Project Manager 2011, Powertrain minion 2009/10

  3. #23
    Well, we did something similar with our first e-car in 2014. We took what we already had from the combustion era, placed the battery box where the engine was, and a donut-style motor (Yasa) right on the axle, housing the diff in it. The car was 240kg and "geared" (due to direct drive) to a top speed of 172kph, but it was dead reliable and thus faster than all previous combustion vehicles of the team.

  4. #24
    Unfortunately this year I was unable to make it for the first time since 2014, however it was an interesting comp to follow! (Albeit through people in my team, rather than SAE themselves). As you say Z it is dissapointing how the comp was organised and despite the SERIOUSLY cool cars this year, it was hard to follow any know what was happening without talking to my team. The most recent post from SAE is still from Friday.. anywho!

    Quote Originally Posted by Jonny Rochester View Post
    #E43 UTAS, 265kg without aero (but wings went on in pits then came off again). Only driven in the week before comp, (yeah, I drove it a bit. Had enough power.) Stuggled to get through EV inspections. Failed rain test the forst time. Then failed brake test and wasted time. Got to endurance but only made 2 laps as we couldn't charge the battery due to software issues with charger.
    Do you mind me asking how it failed rain test? The thought of an EV failing rain test has always made me uneasy and I am just a little curious. Great to hear you guys have a running EV though, im looking forward to seeing how it goes in years to come.
    Jack
    Student

    University of Auckland - F:SAE:47

    2014: Suspension ~ 2015: Suspension Leader ~ 2016: Chief Engineer ~ 2017: Misc suspension stuff ~ 2018: Misc aero stuff

  5. #25
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    Quote Originally Posted by noah View Post
    ...[the very simple Monash E-car] is what Cal Poly attempted to achieve the past few years but never quite got all the pieces together for race day.
    (^ My emphasis.)

    Noah,

    A "mission statement", or "team motto", that I suggest would benefit all teams is,

    "Do LESS, but do it BETTER, and do it SOONER!"

    Rule 1.1 challenges the teams to do five things, namely "...Conceive, Design, Fabricate, Develop, and Compete with small, formula style, vehicles.". So,

    1. Conceive ... the simplest possible vehicle that gets the job done. This requires making very good high-level assumptions, preferably backed up by wide-ranging studies of the prior-art, and realistic lap-sims.

    2, 3. Design and Fabricate ... the small number of essential parts of that vehicle. This requires high levels of "craftsmanship" skills to ensure every part works well, and never fails. Importantly, get this done ASAP, so you can spend as much time as possible on next phase.

    4, 5. Development and Competition practice ... because students' "craftsmanship" skills are rarely at the level needed, (because they are still learning!), so some parts inevitably need "fixing". Even Munchen's car had "fixed" brackets on it.

    MOST IMPORTANTLY - Learning to use CAD/FEA/CFD programs does NOT maketh thou a good craftsman. Only real-world practice, practice, practice..., gets you there.

    Anyway, above is pretty much Monash's recipe, and has been for as long as they have been winning. About a decade now.

    Z

  6. #26
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    Here is a link to some photos I found on UNSW's FB page.

    https://www.facebook.com/UNSWRedback...type=3&theater
    ~o0o~

    TOLD YOU SO MOMENT - Looking at these photos reminded me that the top-three cars in BOTH C and E-divisions ALL RAN DASDs! Well, almost. The only exception was #E31 Munchen's rear-Spring-Dampers, which were pushrod-rocker actuated to get them "out of the wind". However, Munchen's fronts, and all corners on all other podium cars, were all "Direct-Acting".

    (Edit: Oops, fake news! This year #7 ECU has the hydraulically interconnected "soft-warp" suspension, with their bespoke hyd-actuators driven by pullrods(f)/pushrods(r)&rockers. In previous years they have used DASDs.)

    Clearly, Push/PullRods&Rockers are NOT necessary for success. In fact, the "correlation" would now suggest that if you fit P/PR&Rs, ... then you go to the bottom of the ladder.
    ~o0o~

    Other noteworthy points.
    #14 Curtin - The Belt-n-Cones CVT's front-pulley, and a small part of the rear-pulley, are visible in front of the left-rear-wheel.

    #13 Canterbury - Had overheating problems pre-comp, so hastily bolted a "truck radiator" to side of car. This radiator was attached via some mild-steel angle-iron brackets with mill-scale finish. Such last minute modifications are typical of any project that "pushes-the-envelope".

    #E31 TU Munchen - Even the best have to make such last minute "fixes". Look for the bracket between top-of-main-roll-hoop and rear-wing. Apparently, the original, more "optimised", bracket (CF? Al?) wasn't up to scratch, hence the fabricated-sheet-steel version, complete with speed-holes!

    Ahh, yes, "fab'd-sheet-steel" will fix anything!

    Z

    Edit: Also #63 UNSW - This once "all-aluminium" car now has steel wishbones, steel driveshafts, and some other steel-stuff, and is rapidly climbing the ladder. Came second here, in C-division.
    Last edited by Z; 12-20-2018 at 06:02 AM. Reason: Fake news!

  7. #27
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    Further to the "fake news" edit in above post, it is worth considering why ECU used rockers to drive their hydraulically-interconneted-roll-springs, which, incidentally, act as "longitudinal-Z-bars".

    With the normal DASD suspension much of the under/oversteer handling balance can be adjusted via changes to Elastic-Lateral-Load-Transfer-Distribution. For big changes this is done by changing springs, such as using stiffer-fronts for more understeer, and so on. For finer adjustment rubber blocks can be inserted between the springs' coils to increase rate (<- see posts from several years ago on the Cincinnati car).

    With ECU's car the majority of the ELLTD comes from the hydraulic "roll-springs". Here the obvious ways to adjust ELLTD are:

    1. Change the diameters of the front or rear hydraulic rams. This means manufacturing many different diameter rams, with all their different sizes of pistons, seals, etc, which is considerably more expensive in time and dollars than buying a range of off-the-shelf steel coil springs. Also messier changing the rams (oil spillage! and then bleeding!) and harder to do fine adjustments.

    2. Adjust the motion-ratio between wheel and ram. This can be done over a smallish range with Direct-Acting rams, simply by changing the inclination of the ram.

    But my guess is that ECU wanted to give themselves a bit more flexibility in all these adjustments, so went with the Push/PullRods&Rockers.

    Z

  8. #28
    I believe one of the reasons they are using a push/pull rocker set up is that they're running a pitch spring front and rear, the hydraulics are connected such that the pneumatic rolls springs don't carry the weight of the car (unlike longitudinal z-bars). You might have noticed they have what look like quite light coil springs on each corner. Speaking with them before comp, if my memory serves me right, they said that they use these to make fine lltd adjustments.

  9. #29
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    Ambrose,

    Yes, indeed, my fake news correction above may be even faker.

    To repeat my excuse, given the lack of any "program" listing the basic cars specs, I didn't bother taking any notes, so most of my above comments are just from memory of many conversations with many people. Also it is hard to decipher hydraulic systems from images of a car, because the operation depends on how exactly the tangle of plumbing is connected.

    So, how does the ECU system work? I guess someone from ECU will have to explain.
    ~o0o~

    But while I am here, a "Roll-mode-ONLY" hydraulic springing system can be done by connecting each side-pair of wheels with a hydraulic analog of a longitudinal-Z-bar, namely top-front-ram connected to top-rear-ram, and bottom to bottom. Then the four longitudinal hoses (2 x L, 2 x R) are connected laterally by a single "hydraulic-U-bar" that acts as the "Roll-spring", namely top-left-hose connected to bottom-right-hose, etc, with sprung-pistons somewhere in these lines. Many traps here...

    However, note that such Roll-mode-ONLY springing is more complicated than allowing Roll to be coupled with Heave. This is because controlling any SINGLE four-wheel-mode requires interconnecting ALL four wheels to its controlling spring. However, aiming to only separate any two modes from the other two modes, only requires connecting the wheels in pairs. So a pair of longitudinal-Z-bars will control Roll+Heave while having no effect on Pitch+Twist(=Warp). Err..., but all this depends on the strict definition of the modes.

    In FS/FSAE it can be useful to have both Roll and Heave quite stiff, for less scraping of sidepods or chassis on ground, so the same "spring" (= longitudinal-Z-bars) can be used. Pitch should also be stiff-ish, for no scraping of chassis-mounted-front-wing or engine-sump. Meanwhile, Twist can be very soft, although it should still have bump-stops at each end of its soft travel, as discovered rather alarmingly by one of the UQ cars several years ago.

    All up, this can be done perhaps most simply with 2 x longitudinal-Z-bars + 1 x lateral-Z-bar, all of the steel-torsion-bar variety, or similar.
    ~o0o~

    MAIN POINT I should stress here is that with the billiard-table-smooth tracks in FS/FSAE there really is NO NEED for good suspension. Despite many students wanting to push this particular envelope, there is very little reward on offer for building any kind of "interconnected suspension".

    Cars with go-kart-stiff suspension have won in the past, and are capable of winning again in the future. Imagine a lightweight, mega-aero car, with minimal attempt at suspension, other than squishy tyres (eg. go-karts or F1). This situation will continue until the tracks get some REAL BUMPS, AS ARE FOUND ON REAL ROADS!

    A good start at such "real bumps" would be to pick a naturally "undulating" track, namely a surface with long-wavelength bumps (10+ metre crest-to-crest) that "twist" the suspension. Then add some short-wavelength bumps, or "corrugations", that test single-wheel "shock-absorbancy", with these corrugations preferably placed near the corner apexes. Such corrugations could be done with removable rubber dome-shaped speed-humps, about 1+ metre diameter, 3+ cm high in middle, tapering to 5 mm at edges.

    Then get rid of the "mandatory +/- 1 inch suspension travel" rule, which is redundant. In an objective, engineering, world, the track determines which solution is fittest. Incidentally, well set-up DASDs will work better than P/PR&Rs on such bumpy tracks, for the many reasons I have given before. A fully-mode-separated suspension will work even better.

    But I have been publicly pushing for such "real bumps on track" since 2005, and so far nothing. Apparently bumps are "sooo NOT F1"! An "engineering" contest this ain't!

    Real bumps on track => REAL NEED for good suspension => MUCH LEARNING by students => better road cars.

    Z
    Last edited by Z; 12-26-2018 at 10:37 PM. Reason: Many words...

  10. #30
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    Some more pictures, via Monash's FB.

    https://www.facebook.com/monashmotor...type=3&theater

    Miscellaneous comments:

    MONASH - * Normally running on 10" Hoosiers, but on 13" Goodyears in the wet.
    * Still using mild-steel tubeframe (with CrMo roll-hoops, because more accurate wall thickness). Rumour is that carbon-tubs are coming soon...
    * Front DASDs at ~45 degrees (or less) to horizontal, giving Motion-Ratio <0.7:1. This gets squared in the relevant equations, giving 0.7 x 0.7 = 0.49. So is Monash's suspension only half as good as all those cars with the "optimum" MR = 1.0?
    * Rear DASDs are much steeper. This, no doubt, is to clear the aero-tunnels, which this year seem bigger than previous years.

    TILT-TEST - Photo shows how unrealistic this is, with this particular tilt-table. I'm not sure about the rules here (haven't checked for a few years), but the ~10 cm high "wall" supporting the lower tyres here makes the "60 degree", or "1.7 G", rollover test much easier to pass. Hypothetically, a car with a ~9 cm high CG could be tilted past 90 degrees without falling over. That's "infinite G"!

    TU-FAST MUNCHEN - World leading aero, so look closely!
    * The front-wing is very cambered, or "U-shaped", with an up-turned nose, and the whole thing is quite high off the ground. My guess is that this is to be "gentler" to the wind, and not mess it up too much before it reaches the other aero-stuff.
    * They don't have a normal undertray, namely something like a "full-length floor", but instead have three quite distinct wings, Front, Mid, and Rear. These three wings are physically quite widely separated, although there is undoubtedly a lot of aero interaction between them.
    * The car's track-width is 1200 mm, c/c of tyres (from dodgy memory), making it one of the widest cars running these days. Much talk from other aero-students about also going up in width, simply because it gives MORE WING AREA!

    Z

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