FSAE Michigan 2013

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Originally posted by Kevin Hayward:
... in design events: ...
- Confidence and delivery can be more important than the content you are delivering.

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Originally posted by Edward M. Kasprzak:
... Our feedback sessions talk specifically about the team's car and give suggestions on how to improve.

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As he usually does, I reckon Kevin has got it right.

If the Design Judges are really giving the students useful feedback, as Edward suggests, then why is it NOT working?

Almost every other form of "motorsport", amateur or professional, always shows a steady improvement in performance, at least until the Rules are changed to slow the cars down. In FSAE the rate of improvement has been glacial, even though the aero rules have recently been freed up!

I am quite convinced that if there was an amateur drag-racing class with similar rules to FSAE (20mm restrictor, 75m distance, etc.), then over the last 20+ years the Acceleration times would have dropped to the low 3 seconds, possibly even high 2s. Likewise, Skid-Pad times should be in the 3 seconds by now. But instead the times have hardly changed (average times have probably increased, if you include Indian teams).

The problem, IMO, is the all too common attitude these days that "There are no wrong answers, just different choices...", or similar drivel. The oft-repeated DJ version of this is "We don't mind what design decisions the teams make, just as long as they can defend those decisions convincingly..." (see Kev's quote). Of course this is nonsense, and is probably why so many teams keep making the same wrong decisions.

Yes, some decisions are plain STUPID. A good example at this recent comp was the large number of cars with front pushrods leading to rockers and spring-dampers mounted ON TOP of the noses. Yep, rockers and spring-dampers mounted to give the highest possible CG, the maximum yaw inertia, and all that extra, though unnecessary, chassis tubing and bracketry up there.

Now I am sure that the teams adopt such bad designs because they see so many other teams doing same (ie. quite natural for H. Sapiens to follow the flock). Yet there is absolutely no valid justification for this sort of design. But do the DJs point out such bad decisions to the teams? Apparently not, because the teams keep repeating them.
~~~o0o~~~

Anyway, I reckon a better example of design feedback, and perhaps the way the Design event could go, is the "driver swap days" after the Australian events. Experienced team members drive the other teams' cars, and then publicly give very interesting and useful critiques of the cars, good or bad.

But until something like that starts happening, any team aiming to win outright had better look for a 100+ point jump on the opposition in the Dynamic events, just in case they are dudded in the Design tent.

Z

(PS. In the interests of openness and transparency, are we ever going to hear why UWA only got 3/200 Design points in FSAE-A 2012???)

I think the biggest problem with what you're saying is the glacial progress of the competition (other than the tires available and the skill of the drivers, but thats not my point) is the fact that unlike an amateur drag racing class, if you're lucky you can keep a core group of members going for 4 years in FSAE. Almost every year you've got someone (or a group of people) who are leaving the team who have hopefully lent their knowledge to the members still on the team to continue on. It doesn't matter how much you try to teach, it takes quite some time researching and learning to get to a certain level. A lot of times, when you realize that you're at the level where you have at least an understanding of a system on the car and how to solve the problems behind it, it is time for you to graduate. You can't teach most freshmen how to solve an 8 DOF tire model (random example). Or if you can, the chances of them truly understanding it and being able to build on it are slim to none.

In most other motorsports, you get AGES to continue developing things. Your chief engineer and technical specialist don't change every year, and with each leader a new goal for the car. And then, unless you see something break, you may repeat that mistake in the future, simply because you didn't know. Its the school of real world engineering, and you've only got 4 good years in this sport before you have to move on to something bigger (or grad school).

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Originally posted by AxelRipper:
I think the biggest problem [is]...
... you're lucky you can keep a core group of members going for 4 years in FSAE...

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Axel,

I agree. It seems that every few years the teams "reboot", and are back at square one.

An interesting thing is that many of the post-FSAEers on this Forum look at the problem from a much bigger-picture point of view (eg. Geoff and his "Reasoning..." thread), and, IMO at least, see the problem as being a lot easier to solve than when they first started. Namely, focus on the really important stuff, and keep everything else as simple as possible. By contrast, most newbs want everything as complicated as possible, because "Hey, we're building a mini-F1 car here!".

The disappointing thing is that FSAE is supposed to be an "educational competition". All these useful lessons should be passed on to each new intake of students. On the face of it, we should expect FSAE to have the fastest rate of improvement of all types of motorsport. Relatively liberal rules, hundreds of universities around the world, thousands of research theses each year, all with the singular goal of building "the fastest possible autocross car, ever!". But it ain't happening...

Honestly, I have to blame the Design event as being a major reason for this almost complete lack of progress. Too many newbs have (or are given?) the impression that their job is to impress the DJs with their "mini-F1" car...

Z

Well to be fair, doing things based on lesson learned is one thing, but new teams sometimes want to do things differently. Its their freedom and its their lessons to learn. Another thing different from the real world is that results don't necessarily translate directly to funds or lack of funds. Because the focus of this being a student competition, its again coming back to the question of winning or learning should come first....

Zee, did you ever wonder...

http://ct.fra.bz/ol/fz/sw/i55/5/6/22...ey--9085f4.jpg

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Originally posted by Z:
Yes, some decisions are plain STUPID. A good example at this recent comp was the large number of cars with front pushrods leading to rockers and spring-dampers mounted ON TOP of the noses. Yep, rockers and spring-dampers mounted to give the highest possible CG, the maximum yaw inertia, and all that extra, though unnecessary, chassis tubing and bracketry up there.

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Thank you for bringing such a brilliant example. You may be personally convinced that this is the case, but there are some very good reasons for having the dampers on top of the nose. The forces you introduce into the chassis can be massively reduced and you can get to extremely better spring rates, especially when using 10'' tires.
For me your sentence is definitely a zero-pointer. All the disadvantages of a push rod system you bring here are correct, but you miss some important advantages. The first five cars from our team had the push rods on top of the nose, then in 2011 the team decided to switch to a pull rod configuration. In 2012 this was kept as the moulds for the monocoque were reused. This year they switched back. Most people I know who tried both prefer the push rod configuration.

This has gone a bit off topic, but it is so great to show that sometimes it really isn't clear what's the right decision...

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Originally posted by Z:
Yet there is absolutely no valid justification for this sort of design.

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In addition to Bemo's points: I'm betting Z has never tried to package an electric motor in a 10" front wheel http://fsae.com/groupee_common/emoticons/icon_smile.gif

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Originally posted by Bemo:
... The first five cars from our team had the push rods on top of the nose, then in 2011 the team decided to switch to a pull rod configuration. In 2012 this was kept as the moulds for the monocoque were reused. This year they switched back. Most people I know who tried both prefer the push rod configuration.
... sometimes it really isn't clear what's the right decision...

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Bemo,

The disappointing thing here is that you seem to suggest that there are only TWO possible decisions. Namely, "Do we use push-rods, or pull-rods?"

This is especially disappointing given that this thread's originator, RobbyObby, has the signature quote,

"A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away." -Antoine de Saint-Exupery

YOU DO NOT NEED PUSH-RODS OR PULL-RODS, AT ALL!

In fact, I would say that the reason that there is so little progress in FSAE is that you are all wasting far too much time on such useless decisions.
~~~~~o0o~~~~~

To explain above, I earlier suggested FSAE Acceleration times should be in the low 3 seconds by now, and Skid-Pad times in the high 3 seconds (possibly lower for both). I mention these Dynamic events because they are the most objective, so times can be compared (AutoX and Enduro have changing layouts each year).

Anyway, some simple big-picture "decision making" suggests that you can get into the 3 seconds in Skid-Pad by building a simple, lightweight car, with as much aero downforce as you can find. Push or pull-rods are irrelevant (in fact, a disadvantage). Power-wise you only need about 10 kW. And it should be quite obvious that this sort of car (with a bit more power) will also do well in AutoX and Enduro.

In Acceleration, my numbers suggest a maximum power car (~90 kW at crank) with the usual FSAE weight distribution of ~50:50 can at best get into the ~3.8 second times. This confirmed by the results over the last 20 years. On the other hand, a simple lightweight car, with only about 50 kW at the crank, but with rear weight between 60% and 70%, and the right launch technique (the first 5-10 metres are the most important), will get into the ~3.5 second times.

Now good Acceleration times are not very important for overall FSAE results. But squashing the major masses (ie. driver and engine) backward to give ~60+% rear weight can also significantly lower yaw inertia, and that does give a big performance advantage overall.

So why do most current FSAE cars have 50:50 weight distribution, and also an unnecessarily large yaw inertia? Because, "Well, err..., that's what everybody else is doing...". It is nothing but mindless copying of the motor-bike-engine-with-forward-leaning-cylinders-that-pushes-driver-forward-and-over-the-front-wheels. Just like the mindless copying of push and pull-rods...

When are you students going to learn some engineering?

Z

Z,

A couple questions.

1) How much do two FSAE spring/damper units weigh?
2) How much do two human legs weigh?
3) How much more important is it to lower item (2) by one inch than it is to lower item (1) by one inch?

I agree that we could get into the low-fours on the skidpad if we were allowed a decent (wooden!) skirt on our tunnels. However, the FSAE rules state VERY clearly that nothing other than the tires may touch the ground.

Good luck designing the 65% rear weight distribution car, or finding two tires, one with twice the cornering stiffness of the other, that otherwise have identical cornering characteristics (not just the lateral vs vertical force functions but identical paths to operating temperature from cold). If you are anywhere near the minimum wheelbase, and are opposed to building a big heavy car with a big heavy four-banger engine, you will have to start with a "sidewinder" engine and its compromises and be very careful with your driveline part selection to get anything like 65% of the weight on the rear tires.

Charles,

Z has indicated a preference for direct mounted shocks instead of pullrods / pushrods. This allows for low legs and low shocks, as well as being a very simple light option. Motion ratios for a double a-arm would be in the region of 0.6 to 0.7 which isn't far off what a lot of teams run with the mountain bike shocks anyway.

Kev