UTAS build thread

[Z]

Jonny,

First the good news.

I agree with Jay that your approach of "build first..." is good for an inexperienced team like yours. As noted, getting the other students motivated by having something real to sit in can be a huge factor in improving your end-of-year results. The fact that you are also ready to modify whatever you have built, based on what you have learnt from the last build (eg. not enough foot/elbow/engine room, or whatever...) is also good.

The truth is (IMO ), MS tubing is dirt cheap, and the build time doesn't cost much either (especially while you are enjoying it), so you will be learning far more by following your approach than by sitting in front of some myopic CAD box. In fact, I reckon the only advantage of spending a year looking through the keyhole of a typical CAD system, is that it better prepares you for a future career as a gynaecologist!
~~~o0o~~~

Now the bad news.

The pictures of your first frame are down there with the worst FSAE spaceframes I have ever seen (well, not including the Indian efforts ). But your CAD image is EVEN WORSE!

SIMPLIFICATE! Add fewer tubes. Add fewer nodes. Add fewer bends... The tubes that are mandated in the Rules are almost all you need. You are using an engine at the lighter, lower power, end of the spectrum (= the best end, IMO), and hopefully also 10" wheels (?), so you DO NOT NEED the Sydney Harbour Bridge to hold it all together.

Your current frames (built and CAD) have very little torsional stiffness. I know this just by looking at them. Please measure the Nm/deg of your built frame. It only takes about an hour of simple testing to get an answer within 10% (ie. 90+% accurate, which is much better than most team's (non-) number!).

Randomly adding more diagonals won't improve things. A sheet steel floor might help a little, and you need a floor anyway (spot weld in 0.6 - 1.0 mm galvanised sheet). Perhaps increase the diameter of the main longitudinal tubes (top and bottom SIS) to, say, 30-40 mm. Keep them same wall thickness, but make them straighter (just slight outward bow, front to rear).
~~~o0o~~~

Finally, Curtin U came second at FSAE-Oz 2013 with a car that weighed 260-280 kg (with NO driver or fuel!). I believe their overall approach was similar to yours of build->test->improve... (Though much different overall philosophy of four+wings.) So don't worry about your rod-ends being TOO big (maybe a few hundred grams extra, all up?).

Oh, and if you manage to build->test->improve a car that can actually drive 30 kms, at an average speed of ~50 kph, then you will beat half the other teams at Oz-2014. Many of the teams below you will have followed Claude's advice.

Z

[Jay Lawrence]

Claude,

I was pretty sure you would disagree with the 'build first, design later' approach. I understand that and I fully understand that in the professional world of racing (or even more so, consumer cars) there is too much money flying around for this to work (you can't keep going back to expensive suppliers with slightly tweaked designs and expect fast delivery, for example), but in this category I think it can work. In fact I believe the first Wollongong car was built that way (including some Formula Ford bits as per Jonny's car), and it was lauded as the best first year car ever. Anecdotal I know, and there are plenty of rubbish first year cars, but it can work.

I do agree about the spherical/welding issue though. For a while we ran a spherical cup with a circlip on one side, but then moved to staked Aurora bearings, which is neater and eliminates the circlip. Either way I don't think they should be machined to size then welded, regardless of how good you are at welding. Compliance is a killer and having a misshaped bearing housing doesn't help. But hey if it works it works

[Claude Rouelle]

Jonny,

You should not spend money on data acquisition, especially with National Instrument who love collaboration with universities. If you know how to sell your dream these things should be free of charge for a FSAE / FS team.

[Claude Rouelle]

Jonny, Jay.

University of Bologna went to FS Spain in 2011 (I was the chief design judge) where there was only about 20 cars but they won the design competition and finished second overall. It was their very first competition. Their faculty adviser did not allow them to access any machining and the workshop until the COMPLETE design was finished. The whole car, jig included, was built in 7 weeks. There was no surprise, no missing parts, no unnecessary over time or over budget. Pretty good example of thinking before building.

[Jonny Rochester]

Claude,
I just googled Bologna, and it seams you missed somethings in translation. They had comprehensive designs in 2008, a complete car in 2009, and competed at both Italy and Spain in 2010. And since this they compete at 3 FS events per year, 2011 included, as they are in Europe and can travel. And they have 60 people. So you got that wrong.

But lets just imagine Spain 2011 was their first event, and they did ALL design work first (without having knowledge of any physical fsae car). This means that when the chassis was welded by a student, that was the first time that student had done any welding. When the axle was machined, that is the first time the student had ever used a lathe etc. And nothing went wrong...

[Jonny Rochester]

I agree that it is good to aim for a complete CAD assembly before building. Not always possible.

The bearings will not have to be pressed in, it is a slight clearance fit. Loctite bearing retainer will be used as previously mentioned. Going to staked Aurora bearings would be nice, but that would require buying new bearings with the G groove. Unnecessary cost.

[Jonny Rochester]

I am having trouble finalizing the seating position and knowing where the pedals should go. There are so many variables, it's hard to know what to anchor. It's hard to sit inside a CAD model. How do we do it?

(Never mind the torsional stiffness issue, chassis not finalized, it's just a bracket!)

[Z]

I am having trouble finalizing the seating position ...
It's hard to sit inside a CAD model. How do we do it?

Jonny,

I'm pretty sure you know how...

More to the point, I reckon your chassis could be about half a metre shorter. This would give it lower mass, more stiffness, lower Yaw inertia (probably the most important one here), so better all up.

To do this, push the engine further back, so shortest chain run that works, and diff possibly behind axle line a bit (10 cm is OK). Then push the driver further back too, so the seat-back is as close as feasible to the cylinder head and exhaust (couple of cms is OK). Then think about a neat and tidy foot/pedal-box area, with no unnecessary forward overhang.

Then, get rid of about half the tubes in the above images!

Nevertheless, congratulations on progress for Oz-2014 so far, and for posting all your work here.

Z

(Edit: PS. Your 4 x main longitudinal tubes (top and bottom SIS) each have two bends in them, at the FRH and MRH. I suggest they only have a slight bend at the MRH, then straight-line to the Front-Bulkhead. Straight lines are always easier...)

[nowhere fast]

It's hard to sit inside a CAD model. How do we do it?

Jonny,

I’m not sure if your last post was tongue in cheek, but my team would mock up the driver position in two stages.

First we would put drivers on a mock up seat back made from wood that we could adjust the seat back angle on, and then measure where their feet and hands needed to be.

Once we had a rough chassis design (developed on a whiteboard and in CAD) we would make a physical mock up from wood or cardboard (our chassis’ were made from folded aluminium panels) to check ergonomics, visibility, packaging, etc.

I agree with Z about moving the engine and driver further back and as close together as possible; but will add that another advantage is increased rear weight %.

Finally; it’s good to see UTAS returning to FSAE, and it’s interesting to see your progress in this thread.

[Thijs]

For what it's worth, I'm pretty sure Claude meant FS Spain 2010, where Bologna won design and endurance. It was actually their second event, but still their first car.
They finished 16th out of 40 overall in Italy a month or so earlier, 19th in design, 19th in endurance in a much more competitive field.
A fine performance for a new team, and perhaps more indicative of how good the car was, because honestly, FS Spain was very uncompetitive that year. There were 11 teams there, the overall winner was 333rd on the WRL.

A team that really impressed me was Vienna in 2008. They finished overall 4th out of 77 teams at FSG that year with 839 points. That was their first car.
Unfortunately I never got to talk to those guys, but I've never seen such build quality on a first year car.
Purely judging from that I'd say they must have had their design in order by the time they started building.

Thijs