Anyone heard from...?

[Grant Mahler]

Anyone heard from Big Bird, Cement Legs, Z, or Garlic recently? Anyone know how they are doing, where they are, things like that?

They (and others) used to provide some informative and provocative discussion on these boards...which I rarely see now.

[Grant Mahler]

Anyone heard from Big Bird, Cement Legs, Z, or Garlic recently? Anyone know how they are doing, where they are, things like that?

They (and others) used to provide some informative and provocative discussion on these boards...which I rarely see now.

[Garlic]

A lot of noise lately.

Z officially said he was stepping out as he was spending too much time on here, or some sorts. To his credit he stuck to it.

Big Bird has an occasional long helpful post, but it gets caught up in the noise.

I've been around but I am a lot less likely to put my 2 cents in than I used to be. Usually it's only when there are heaps of incompetence.

For example, see my last post
http://fsae.com/eve/forums/a/tpc/f/125607348/m/62510883...10434241#31410434241 (http://fsae.com/eve/forums/a/tpc/f/125607348/m/62510883241?r=31410434241#31410434241)

[Big Bird]

Thanks for the compliment Grant, most appreciated. I think Garlic has got it in one, seems to be a lot of noise on here of late and not much to really stimulate the creative juices. I don't sign on too often these days, just the odd venture to see what the latest lazy request is. (We need to design the suspension. What formula do we use?)

I've always been more interested in the engineering design side of this project, rather than the engineering science. I've got full appreciation for those who show depth of knowledge in their area of expertise, whether it be fuel injection systems, suspension design, brakes analysis, etc. But the stuff that gets me going is the interrelation between the various systems, and how we choose an overall strategy that maximizes the overall result. And quite often, the optimum overall result is not the same as a sum of supposedly optimized parts.

My favorite analogy is the go-kart. We have a pretty decent FSAE car, with a refined 55hp engine package, the best diff for the job, our supposedly ideal suspension, stiff chassis, etc etc etc. We can convince ourselves that the sum of all these optimized parts is some brilliant machine. And then our driver gets into a 15hp go kart with no gears, no suspension, one brake, and a locked rear axle - and whips the FSAE cars butt. There's something in that.....

But there seem to be few that want to talk about this sort of stuff these days. Its a shame really....

Cheers all

[Big Bird]

Sorry, didn't answer your question as to where I am now. I'm still at RMIT, juggling postgrad study with a bit of teaching. We are building a DSR-style car for research purposes, I'm looking after the rolling chassis side of things. Pretty neat little project, should be a bit of fun. The dumb thing is I made it through 3-4 years of FSAE without ever learning how to use a CAD program, so I'm finally getting to have a play with it.

Cheers,

[Freedom Fries]

There is a reason the kart is faster...tires.

When 3 or 4 manufacturers go through 30 years of tire iterations specifically for an FSAE car, I imagine there will be a different outcome.

Chris

[Composites Guy]

This brings up a question that's been in my head for a while. Why does a cart pull more g's in a corner than a FSAE car? Is it just tires???

Big Bird.. I'm a 5th year grad student and have been watching SAE projects for a while now. For years my advisor has been trying to get our undergrads to build essentially a carbon fiber go-kart modified to pass FSAE rules. Ultra-light weight, powered by a turbo'd Biland go-kart engine. Its nearly impossible to get the herd instinct of the team to think that far outside the box. But... 5 years ago it was nearly impossible to get the herd instinct to think outside the tube-frame, 600cc box.

[Freedom Fries]

Composites guy...

It isn't aero making a kart corner fast. And it certainly isn't a superior suspension setup to a well designed FSAE car. From a VD standpoint, a kart has absolutely dismal characteristics. So I think it is safe to say that it is tires.

As for a carbon fiber go-kart to pass FSAE rules, what do you mean by that? That is really an oxymoron. The distinguishing feature of a kart is that it doesn't have a suspension to speak of, which is what you would need to add in order to pass FSAE rules (which are basically designed to prevent people from making go-karts).

If you want people to "think outside the box" then prove to them that it is better (With some sort of mathematical model preferably). I'm not sure what your involvement on teams has been, but if you have been following the competitions, the dominant teams are still running tube-frame 600cc setups. Yes, RMIT won with a composite tub and a small engine. And Western Australia is always finishing very well. But look at the time sheets for autox and endurance. Look at UTA, Cornell, Texas A&M (1st place this year, but not a 600cc engine), Toledo, UW Madison (1st place this year), Michigan, etc.) They blow the doors off of almost every composite tub team, including RMIT the year they won.

Even in terms of weight, I have seen many carbon tub setups that are heavier than a well designed tube frame. Just look at Penn State, Purdue, Northern Illinois, Toledo...

I am probably now officially ranting, so I apologize. We're also way off the original topic. I just think that "outside the box" is one of those cheesy corporate buzz phrases that allows managers to whittle extremely complicated exercises down to layman's terms. Just because an idea is new, doesn't mean it is better. Believe it or not, there are really good reasons why so many teams continue to run tube frame chassis and 600cc engines. Of course, the opposite of this argument is true as well, which is why you need to attempt to quantify which overall design is better.

Chris

[Composites Guy]

Freedom Fries...

I understand the need to quantify and justify all design choices on the car. I also understand the emmense amount of time that it takes to do it! Sadly, I'm getting near the end of grad school and I no longer have that kind of time.

By go-kart I mean a car which disregards a lot of the comlexity associated with "real" race cars. No diff... not 4 wheel independent suspension (perhaps a rear swing arm)... no fancy traction control, electronic shifting, etc. Dare I say that you might even be able to justify the loss of the the rack-and-pinion? Just the basics. 4 wheels (8 inch with custom ordered slicks), an engine... and the bare mininum of parts of the car to pass rules.

We have a couple of go-karts, and I believe Big Bird is correct. They make our 350 lb car look like a lumbering beast on a tight autocross course. It is possible to build a 250 lb car with 40 horsepower that passes rules. Put a trained 100 lb freshman girl in as a driver and you have a serious contender given enough drive time.

Frankly though, the aggresiveness work load and leadership needed to make that actually work is probably outside the scope of the undergraduates abilities at my school. And the 150lb guys that build the car aren't willing to give up their spot in the drivers seat.

Why aren't all the top 10 cars under 400 lbs and made of carbon and titanium... that's easy... 1.) Cost. 2.)Complexity 3.) Resistance to change something that already works well.

[Buckingham]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">We have a couple of go-karts, and I believe Big Bird is correct. They make our 350 lb car look like a lumbering beast on a tight autocross course </div></BLOCKQUOTE>

I'm guessing that this kart didn't have a 60" wheelbase.

[drivetrainUW-Platt]

Gokarts.....

I would love to drive a shifterkart or fast single speed, I am sure they are absolutely insane!

Gokarts in FSAE...

Ever heard of Dearborn? They basically took a gokart and made it a formula car. First year they showed up with a carb Briggs and it got them around the track consistantly. Yes they hoped up the briggs some, but it worked. The next year they went to fuel injection and had some problems with that before competition, but they got that worked out and again made many consistant laps around the track.

Does there car look cool, fast, expensive, no but it gets the job done and it is dirt simple.

[Mike Cook]

Uh, there are 3 things which make karts faster imo.:

1) Way better tires....Also they get way hotter, fsae tires might not be that bad if we could get them up to 170 deg.

2) Shorter WB, and maybe more rear weight (not sure about this though) but way better dynamic wt transfer for long. acceleration.

3) Less inertia.

If your professor thinks that dumbing down a fsae car to make it like a cart will make it faster, he is wrong, most likely because he doesn't understand exactly what makes a kart fast.

Also, depending on track speed, a lot of aero on a fsae car can make it faster than a kart (i.e. nationals)



On edit - There are a few more things which help out a shifter kart which i'm not going to mention. BUT if you all do the math you will figure some of it out. That said, a lot of things mentioned specific to fsae cars make them faster. I mean, a properly working TC system will make the car faster, period. If karts could use TC they would be faster too.

[flavorPacket]

I'd say the cg/track ratio is also much better for a kart than a FSAE car. We're near production sports car levels.

[Bill Kunst]

Hey. no one asked where I was???

Anyway, lets think about the cart. they are about as long as they are wide, shifter karts have about 40 hp, weigh in at 395 WITH RIDER, no suspension, no traction control, no 80lb aero package, tires that rock, wheels that are 5" in diameter, no roll cage, no safety devices to speak of. Yeah, that pretty much sums it up. I guess that someone could make a better mousetrap, but not when the FORMULA is the same. That is the one thing about this competition, the rules/formula for the car have been well thought out and limit you to picking strategies that may be different (single vs. multicylinder) but end up with very similar results.

Its also not just about the ability of the vehicle, its about the ability of the student engineers to sell there design and price it to be competitive.
Bill

[Composites Guy]

It seems that you guys are making a good argument for a kart-influenced FSAE car. A car under 400 lbs with driver, 40 hp, custom ordered super sticky 8" wheels, driver position almost laying down to lower roll hoops, minimal track and wheel base, minimal trappings of the traditional Formula-style car (steering rack, independent axles, diff, traction control and so on).

Mike Duwe. I am familiar with Dearborn's 2005 CVT car if that's the one you are reffering to. I took tons of pictures of it and it remains one of my all-time favorite FSAE cars for its simplicity. But... it was NOT kart-like... it was more of a Baja car converted to FSAE rules. It was big and heavy compared to a kart. I think you could get more horsepower for less weight out of a Biland engine, and you definitely could get lower to the ground and lighter.

[drivetrainUW-Platt]

I am aware that it was a baja car...
The problem with building a kart is the rules themselves. They make you build safety features (for good reasons of course) You need front/side/rollover protection. You also are required to run suspension.

Ever seem some of the kart accidents...not pretty!

[jsmooz]

Sorry, off topic on the off topic....

Composites Guy - As I was one of the main designers on the UM-D team from 05-07, thanks. Usually people just look at us funny when we roll up our car. Nice nice to hear some other competitor agree with the KISS philosophy.

[Ecks]

Having done a few autocrosses in an 80cc shifter with FSAE cars, I can offer a bit of information on what sets them apart.

On the chassis side of things, smaller track width seems to be the most significant advantage that a kart holds. This allows the driver to pick wider lines in the corners and carry vastly more speed though slaloms. On the skidpad, a narrow track allows the driver to place the vehicle's CG closer to the center of the circle. And with centripetal accel = r^2*omega, we know omega= accel/r^2. With r being the distace from the center of the skidpad to the vehicle CG, it's easy to see how reducing track (which allows a reduction in r) can increase omega, and hence reduce skidpad time. It should be noted though, that track reduction comes at a cost of CG/Track ratio, which can have adverse effects on vehicle handling.

On autocross circuits, I had my clock cleaned on anything resembling a straight or a braking zone, but made up the time in the slaloms and hairpins. Typically, the shifter was about .5 sec off the pace of the quicker FSAE cars over a 45sec run.

From a power standpoint, the FSAE cars are generally superior to karts, but this power advantage only comes into play at higher speeds when the tires are not the limiting factor in longitudinal accel.

It is very important to realize that karts and cars share very little in common from a VD standpoint. What allows a kart to corner quickly (inside rear tire lift, for example) is completely different that what allows a suspended car to corner quickly (I don't know, to be honest).

What can we take home from this? Aside from what I've said about size, karts show us that simple, reliable solutions, even if not optimal (think lack of diff), can still make for a very fast vehicle.

[Adam L]

Not to add more noise, but really the main factor is the contact patch size and the weight. Imagine if an FSAE car had 10" slicks on all corners and things would be considerably different.

I took this picture from my balcony sometime back, this is my CRG/Rotax combo, the seat is about 20" wide. You can't fit more than one rear tire in the seat just to put that into perspective. At 385lb min weight the contact patch/weight ratio is huge, even when compared to most race cars.

Saying that a kart has a simple suspension system is correct in theory. In actuality it is a bit of a beast to dial in. You have chassis flex which is determined by front/rear track, seat position, camber/caster settings, weight distribution, and all the previously mentioned items have their own characteristics that they bring with them. For example changing the front track will change your jacking and chassis flex which alter the rear axle's handling characteristics... its a freakin nightmare sometimes. So I threw it into the hay bails a few months ago http://fsae.com/groupee_common/emoticons/icon_smile.gif

http://www.adamlarnach.com/blogpics/main.php?g2_view=core.DownloadItem&g2_itemId=229&g2_serialNumber=1

[Ecks]

Correction to previous post: The equation should be centripetal accel = r*omega^2.
Perhaps I should have paid a bit more attention in high school physics.

[Frank]

What mainly sets them apart is when you run into a tree at your local hill climb race, the FSAE driver gets hurt, and the kart driver dies.

Another thing that sets them apart is that any kid with fanatical (financial?) parents gets to drive karts; and except for our precious ringer drivers, engineers drive FSAE cars.

[LU-Bolton]

After doing this for four years and seeing the changes and evolution of both cars and rules, I've come to the conclusion that an idea like CompositesGuy's is almost impossible to achieve. Slapping a simple and well thought out car together like "a go kart that barely passes rules" will not win.

1. The rules are against you. Every year it gets harder, more rules are put in place to keep us safe. This is fine, but it drastically limits how far outside the box you roam. Things that drastically limit you: 60" wheelbase, cockpit cardboard cutout rules in '09, roll hoop requirements, and all other crash-worthiness requirements. Bottomline: To make a &lt;250 lb car you have to seriously lose weight everywhere. My guess is it's possible, but you may sacrifice safety. If so, they won't let you run at comp and they shouldn't.

2. Like said above, the tires just aren't there. They probably never will be in a size that an FSAE go-kart is looking for. 8", 6", whatever.

3. Other advancements that teams are bringing to the table are only going to narrow the gap between kart and FSAE. Traction and launch control are a good example. Even if you wanted to throw TC on your FSAE kart to make it faster too, you would be defeating your initial purpose of making the car as light as possible. Catch 22.

4. There is no engine that accomplishes what you want. The Biland is sort of close. It weight 35 lbs, and makes 30hp if you're lucky. It has no transmission, which means you need a CVT which means more weight. 30 hp isn't enough and the motor is already high strung as it is. Add a turbo and you've already added weight and complexity. The Aprilia's are the closest thing to perfect, but they weigh too much for a sub 250 lb car.

It's difficult. I want to see new and innovative things as much as anyone. But there is too much against most FSAE teams to pull off such a car. Short of paying a 100 lb girl to drive everyday for months, I still haven't met such a girl who is willing to put her whole-hearted effort into FSAE and be there when it counts. Moreover, to really reach full potential you'll need four of them to compete in all events at comp. Otherwise you have to continue designing for your 6'0" captain in mind.

There are a lot of really good teams out there that are only getting faster each year. The evolution of cars and teams is what wins. A go kart FSAE car would need a team equally devoted to the direction and evolution of the concept to even think about winning.

Aaron Cassebeer