Acceleration/Braking Event

[TG]

Alright, on the Rule Changes to Mix Things Up (http://fsae.com/eve/forums/a/tpc/f/125607348/m/38310815621) thread, there was interest in incorperating a brake test of some sort into competition. I've gone through the thread and here are the ideas so far:

- A measured braking distance after the acceleration run

- Accelerating and braking between two pilons with very narrow, controlled speed areas around the pilons

- I'll add to the list something like a 0-(x speed)-0 with a radar gun or daq and large display in drivers sight

The points would have to come from somewhere, maybe 50 from the endurance event.

The only disadvantage to this would be some flat spots on the tires if they lock (which they must be able to).

I'll let others chime in on what they think of something like this.

[TG]

Alright, on the Rule Changes to Mix Things Up (http://fsae.com/eve/forums/a/tpc/f/125607348/m/38310815621) thread, there was interest in incorperating a brake test of some sort into competition. I've gone through the thread and here are the ideas so far:

- A measured braking distance after the acceleration run

- Accelerating and braking between two pilons with very narrow, controlled speed areas around the pilons

- I'll add to the list something like a 0-(x speed)-0 with a radar gun or daq and large display in drivers sight

The points would have to come from somewhere, maybe 50 from the endurance event.

The only disadvantage to this would be some flat spots on the tires if they lock (which they must be able to).

I'll let others chime in on what they think of something like this.

[adrial]

I think accelerating from 0 -(x speed)-0 would work well.

Driver launches, accelerates through the standard acceleration distance then gets hard on the brakes.

Radar would be used to track the braking of the car. A minimum speed is picked such that all cars are capable of it, and braking distance is calculated from that speed to zero.

However, the biggest issue with this is variations in the parking lot. Lets say braking from 40mph to 0 is chosen for the test. Car A accelerates to 60mph and starts braking, it will be on different pavement during its 40-0 stop than a car that accelerated only to 40. I am not sure how big an issue this would be, depends on where they setup the event...if there is a large bump towards the end of the braking zone...etc.

[Kamil S]

I think it should go 0 - 40? - 0, and they should time the whole run and the seperate 0 - 40 and 40 - 0 runs, and take distances covered.

This makes sure that the drivers need to be aware of their speed at all times, and hopefully teaches some good downshifting techniques!

[Kevin Hayward]

Accelerating to a set speed is going to be difficult for these cars. Most vehicles do not have a speedo. Even if they did how could you ensure callibration. A lot of cars have the wheelspeed sensors necessary.

However it is likely that this sort of event will increase the cost and complexity for most if not all teams.

How about a different method of requiring teams to make space to strap on a packaged g-sensor. These could be provided by the competition and strapped on near the start line and taken off after the runs are completed. That way you would not need one for every car. The score could be calculated based on highest maintained g-force or something during braking. Maybe pick any speed and take the average of the negative g's. Something like this shouldn't be too hard to implement and may reduce the driver requirement.

There are some pretty good g-sensor packages about used for karts etc that should make this relatively painless.

However I do wonder about how you would be able to add an extra event to the US comp without extending the overall length of the competition or reducing the number of teams. It is run very well and there does not seem to be a lot of free time.

Cheers,

Kev

[Nick McNaughton]

I'm a big fan of this - a simple go-to-whoa would be my choice. Start at this line, drive over there and stop with some part of the car between those two cones as quick as you can.

It could even be done by breaking a beam at the start and finish, with the non-disqualification requirement that the car stops across a line drawn between two cones, so long as the line is contained by the vehicle wheelbase - the front wheels have crossed it, and the rears haven't. And crossing it sideways doesn't count either. No speed measurement or G sensors needed...

It's a pretty harsh test of driver skill, vehicle setup, acceleration and braking capability, and requires the same equipment as the acceleration event. I think it'd be a great addition to the comp...

Cheers,
Nick

[Charlie]

Nick maybe I'm missing something but you make it sound way too easy.

I would love to see a braking competition, but how do you accomplish it?

In your explanation of the event, how fast are the cars going before they brake? That is the problem.

I see it the same as Kevin. It's be fantastic, but incredibly difficult to do properly and fairly. If you've seen or competed in the Road and Track competition, you've seen what I mean.

If you rely on a signal from officials that you've reached a certain speed, you are relying on at least the driver's reaction time, and possibly someone else on the sidelines. The fix for this would be a system that automatically senses speed and tells the driver when they've reached it. This would also be better because the driver could practice with it. But, not everyone can afford this and it shouldn't be mandatory, so its a monetary advantage.

A setup to accel and then brake puts better accelerating cars at a disadvantage, and how do you score it?

Like I said Nick you make it sound simple, and I'd love it to be, so if you have solutions to my problems you'd definitely have a great competition addition on your hands.

[Dan G]

Sounds exactly like a Gran Turismo license test. I agree, running a braking test would be difficult. It'd be much easier to run a go-woah with the required stopping area. Get there as fast as possible, must come to a full stop within the cones. Although I'm not sure it'd be easy to get electronic times. It could just be a simple light beam for the start/finish as long as the car stops within the specified area.

But you'd have to give the driver's 2-3 shots at it each. Cause they'd definiely slam the brakes too early or too late one of those times. Prepared teams would be allowed to measure off a "brake here" flag from the finish line, then let the driver adjust as needed.

This event *could* replace the acceleration event, as that would be a huge portion of the time/points. But that would probably draw a lot of complaints.

[Eddie Martin]

When measuring long. and lat. g in the skid pan and acceleration events, time between beams is used because it is the only really practical solution for such a large competition so a similar simple approach would need to be used for this test.

So i have to agree with Nick that it be run as a go-to-whoa eg. the vehicle has to get from point a to point b and stop as fast as possible. (similar to some of the license tests in gran turismo) (Dan, You got your post in while i was typing http://fsae.com/groupee_common/emoticons/icon_smile.gif ) I still can't work out how you would stop the clock accurately when the vehicle has stopped.

If you did try to get cars up to a certain speed and then brake, I can't see how you would accurately police the exact speed you need to brake from and whether you could get 200 + drivers to do it in a day. If you are traveling any faster or slower than the set speed it would be an advantage or disadvantage depending on whether you are over or under the speed.

It would also be a nightmare for the organisers, logistically. Add to this the fact that most teams are making full use of the current events to mandate extra tests.

[Denny Trimble]

I agree with Charlie, telling the driver he's reached a high enough speed was a difficult thing in the Road and Track Challenge when we did it in '03. They had a big display hooked up to a radar gun, but it only updated at about 1Hz! Apparently they said it would "blink" when it sensed 60mph, but our driver saw 48, 58, 68, then hit the brakes http://fsae.com/groupee_common/emoticons/icon_smile.gif

Requiring all cars to reach a minimum speed would be difficult, I saw several cars run the accel event at about 25mph.

I like the "go and stop over this distance in the minimum time" idea. The start could be just like the accel event (light beam with a short staging distance). The finish could be a light beam, followed by a "DNF" beam two car lengths (or so) away. So, if the car triggers the stop light but not the DNF light, they get a time. If they continue and trigger the DNF light, no good. I guess there doesn't even need to be a light beam for the DNF; there could be a "cone on a string" like in the skidpad event, in the path of the car until it stops, then removed to let the car get off the track.

The "no spinning" rule would have to be enforced by judges; perhaps "both front tires must cross the line before any rear tire" would be a good rule of thumb.

[Nick McNaughton]

I'll try and make a little more sense in this post..

Since a pure braking test is logistically difficult to do, the only feasible alternative I can think of is the go-to-whoa concept over some fixed distance.

Stopping the clock at the right time is the tough aspect - the layout favours cars that only just stop inside the box, in order to cross the beam at the highest speed possible. If this is a problem, the 'box' could be very short - but then drivers would keep messing it up and run a real risk of not posting a time at all. I don't think it's a problem, as the 'stop by here' line has to be drawn somewhere, and the timing beam doesn't necessarily have to be on it.

If we had a 75m straight, with the same staging setup as the acceleration run, the 'stop timing' beam could be at the 75m mark, with the back edge of the box at the 77m mark, perhaps with another beam to disqualify the latest brakers. Everyone would try and be stopped at 76.99m, but that's okay, they've got to put the line somewhere. The height of the beam would have to be defined too - broken by nosecone, wing or tyre? The no-spinning clause could be policed by making the gate exactly as wide as the minimum wheelbase - Requiring stability under brakes isn't a bad thing.

If we're that keen on measuring deceleration and taking the accelerating bit out of it, it could be done with two speed traps on the way into the box. Four timing beams would be required to measure speed at two points, from which deceleration can be easily calculated - but that requires more resources and some thinking, which won't happen.

The only problem I can see is that driver skill would play a big part in posting a great time for this sort of thing. It wouldn't be as bad as autocross, but there's still no really good way to separate driver performance and car performance.

[Rob.C]

the only way to separate driver skill from car performance is to have one driver do everything in every car! and that is just silly to even contemplate!

i think that the go-to-woah is a good idea, possibly use the acceleration run as it is and then add an extra distance then this 'box' that the vehicle must come to a stop in, that way we still ge the standard acceleration event but then the braking event after it! and if the driver jumps on the anchors too early they are penalised in the acceleration event! therefore encouraging teams to have good brakes!

[adrial]

I think the go-to-woah is a bad idea as it places a lot of emphasis on the driver.

What if the driver hits the brakes too early and misses this box that the car must end up in??

Just a few days ago there were several members complaining about how much the autocross depended on the driver.

[Buckingham]

It would probably be a good idea for the event to have countdown signs (5...4...3..2..1..) every 5 or so before the end line. That way drivers can practice their braking spot against a standard reference.

I'm against the 0-x-0 (Road and Track style) event. Hitting the target speed is impossible, that is unless you have your ECU programmed to shut off the engine after the car hits the target speed, or your teammate is in the pits watching via telemetry and remotely kills the engine while they watch vehicle speed. The second the driver felt the engine cut they could just mash the brakes.

Wish I would have thought of that before this year's road and track event.... http://fsae.com/groupee_common/emoticons/icon_smile.gif

[CMURacing - Prometheus]

so far, the go-to-whoa event seems like the best idea here, discounting z's with the hairpins (doesn't require fancy timing stuff).

as far as go-to-whoa, you'd also have to ensure the whole car is in the box. the simplest way i see of doing this is to rig a bunch of negative-edge triggered timing lights (i.e. it stops the clock at the on-to-off transition, so it hits the end of the car) to measure when the car stops, and a positive edge DQ light 1.5 car lengths forward. then you'd take the longest stop time from the neg-edge lights.

at least that's my thoughts on how to do it relatively simply.

[Micko..]

I don't think that a go to whoh event would be any more dependant on driver skill than any other event. It is just the opposite to the acceleration event (at least the whoh part is), with practice I think that that drivers skill wouldn't play a huge part in the success of this event and the cars designed acceleration (positive and negative) capabilities would be the real points scorer.

Most teams might have 1 maybe 2, maybe none, "good" drivers, and with the way points are allocated they are always going to be driving the endurance and autocross events, so I think that practice would be the real difference as far as the driver aspect is concerned.

I recon that this would be an excellent modification to the acceleration event. If it is set up as mentioned by Nick McNaughton it shouldn't be that much more effort for event organizers.

Just my thoughts http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Kevin Hayward]

I have seen video footgae of quite a few go-to-whoa contests. Watching old SumemrNats videos from Australia was a bad habit of mine a few years back. From what I can see it is an incredibly driver dependant event. I can see how a team could go about slightly modifying their instrumentation and driver training program to improve their position in the event. However a go-to-whoa is not a direct measurement of braking performance.

As for Eddies comments: the timing of the Skidpan event is a perfect way of measuring exactly what you want to compare the vehicles on. That is average lateral g's for a given distance.

The advantage of timing the Accelleration is the same. Average longitudinal g's over a given distance.

However there is no simple way to measure that value for braking from simple timing procedures without knowing a starting velocity. This has already been discussed as not being feasible.

The Acceleration and Skidpan are my favourite events in FSAE. They are the two events that are most car dependant. If a braking challenge were to be introduced it would be nice to see another direct car performance indicator. Assuming that we aim to have FSAE more as an engineering challenge than a racing challenge.

I still believe that a simple g-box style solution is possible. It could be triggered by two timing beams for start/finish. A simple algorithm could be designed to take the average negative g's. The car does not have to stop and can start braking at any speed (well any speed it could reach before the breaking beam). The box would have to mounted by the teams. There is no advantage to mounting such a box incorrectly as the best results would be obtained with the g-axis pointing straight forward. The major logistical problems would be the cost of the equipment (of which you would not need a box for each of the cars) and the downloading of data. All the events require significant post-processing of data anyway and given that the info would be computer based it could be done using simple programs.

I don't think that a system like this would have been achievable in the not too distant past but this sort of equipment is becoming pretty cheap and easy to use.

I can also see big advantages in design judging by having clauses in the rules that stipulate cars must be built allowing such a device to be mounted. If a 2-way accellerometer was attached to design finalist cars for the endurance etc it would give a great comparison between the cars on equipment callibrated by event staff. Like the dyno result but for vehicle dynamics.

Anyway this discussion goes I think it is worthwhile bringing the idea to the event co-ordinators. Maybe a trial of the event could be held at the completion of next years comp to test logistics of different solutions etc. A small group of cars could be taken aside at the same time as the Road & Track challenge. Safety guys should still be around. If it ends up being a logistical nightmare the whole idea could be shelved.

Cheers,

Kev

[Kevin Hayward]

Thinking about even a little bit more I think that a box could be made self contained with an LCD display that shows the result of the algorithm calculation of the last run(s). Hence the value(s) would only have to be recorded by somebody at the end of each run ... no downloading required.

The value you would look for would be average braking g's for a given time (or distance).

Kev

[adrial]

Kevin,

I like your idea.

Perhaps G-tech would sponsor the FSAE competitions and provide some of their units free of charge. The newer generation has 3 accelerometers, so mounting is not as critical.

[Sam Zimmerman]

Why not just keep the 2 events seperated? In the braking test, give enough room for the driver to reach a certain speed at the line, the measure the braking distance. A minimum speed of XX mph (measured as the front axle breaks the starting line) begins the event. The distance is then measured to the furthest tire at the end (assuming the car may be slightly off-angle when it starts.) If a car is less than XX mph at the starting line, a DNF is awarded.

Simple competition, easy to evaluate performance, no expensive equiptment for the teams, and the best part is that it encourages everybody to put a tach in their racecar. http://fsae.com/groupee_common/emoticons/icon_wink.gif

[Mike Cook]

I mentioned this in the other thread but to repeat. How about just have an immediate braking zone after the acceleration run. THe acceleration part is measure in time, and the braking part is measured in feet. There of course will be a weighting system such that those with faster acceleration runs will take longer to stop than those with slower acceleration runs. The only problem I see with this is that two cars could run the same acceleration times but have differing ending velocities and the one with the slower speed will have an advantage in the braking distance. However this still seems to be a pretty easy way to do a braking test.

[Nick McNaughton]

Measurements and strapping things to cars takes people and time, and those are two things the event organisers are desperately short of. They were sending a car every 15 seconds or so for the acceleration run, and that sort of thing has to be kept up if they're to run the event inside any sort of time limit. I know I wouldn't volunteer to measure braking distances - I wouldn't want to be anywhere near some of these cars trying to stop as hard as they can, let alone have them all driving towards me one after another, four times each.

A fancy way to do it would be to incorporate accelerometers and data logging into the beacons we all have to attach to the car, but that's expensive.

A simpler and automated way to do it is to use four beams in a designated "braking zone." Measure the time taken to travel half a meter at two places in the braking zone a calibrated distance apart, assume constant deceleration and you've got braking performance.

That way, the acceleration event would run as normal with the only difference being for the driver to brake as hard as possible for a ~5m section of track shortly after the finish line...