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Thread: UTAS build thread

  1. #11
    Claude,
    -I can't show you the whole car as it is in secret development (code for not yet designed). Major parts are designed by some 4th year students as their honours project. And in Australia those reports are not submitted till about October/November? However we are planing to have the car running by June/July.

    -7/16" and 5/16" spherical bearings are chosen for a very good reason, it's what the old car had.
    But I have found drawings of a Formula Ford that generally uses the same bearings, but they use reducers to accept a smaller bolt. eg: 7/16" sphericals with reducers and a 5/16" bolt. And on other places 5/16" bearings with reducers and 1/4" bolts. With the celvis bolted to the chassis using a mixture of M8 and M6 bolts. I'm talking about Swift Cooper SC95 chassis. I'm drawing some influence from well designed Formula cars rather than student designed.

    -The bucket for the bearing will be machined first. It will be setup for welding, it will be quickly TIG welded by an expert student (myself). Remove scale and the bearing should go in perfect. (See test sample above). We use a shoulder and 1 circlip.

    - as for weakest point in chassis... It may not matter, because if we build to min amount of metal as per the rules, that may be strong enough regardless of poor triangulation. Did you ever see a legal FSAE car that could not compete due to chassis flex through the middle?
    University of Tasmania (UTAS)

  2. #12
    Jay: - The front hoop (dashboard) only looks tall on our welded chassis, because it is too narrow, and because the front bulkhead is probably too low. Looking at the CAD picture, that is changed. The ladder chassis was designed in 2011-2013 by former 4th year students.

    -The BMW motor was chosen for a very good reason. It was given to us.
    University of Tasmania (UTAS)

  3. #13
    Pat: The uprights are being designed in an engineering design class, however they are only designing the materials, weight, stiffness and a few clearance issues. I have designed the geometry of the uprights myself (after some group meetings using a white board and a few scribbled diagrams on an envelope). So the geometry of the uprights is fixed, and known, (and constrained a little as we are using the old cars wheel bearings and axles etc.).

    -I can't agree with you about stiffness of our suspension bracket. It is only tack welded for now, but it will probably get changed. Very similar design, but may use welded in studs rather than welded captive nuts. With captive nuts we may have to drill and wire the bolts. With studs we can just use nylocks.

    -The extra chassis bay at the back is for orange jacking bar, and rear trailing wishbone mounts.
    University of Tasmania (UTAS)

  4. #14
    Quote Originally Posted by Jonny Rochester View Post
    ...

    -7/16" and 5/16" spherical bearings are chosen for a very good reason, it's what the old car had.
    ...
    We sarcastically have a tile hanging above the maintenance bay which says "Because they did it like this last year..." (in Dutch "Omdat het vorig jaar ook zo was..."). Try telling that to the judges.

    On your note to the Formula Ford: Those cars are over 400Kg dry and have a lot higher loads to process. You can get your car up to that weight but then you break the tilt table (as happened at FSUK once).
    Tristan
    Delft '09 Team member, '10 - Chief Electronics
    'now' (Hardware) Security Engineer

  5. #15
    Jay

    " I would argue that to a certain extent it's not a bad idea for a first year team to 'build first and design later"

    I totally, totally disagree with you. That is the worse habit to acquire for news designers/manufacturers. It is bad project management to start building car without ALL the components being part of the design.

    I see every year too many FSAE/FScars where it was clear that the students started to build their car without thinking about where to put the muffler, the ARBs, the steering rack, the radiator(s), what the shape of the fuel tank will be and where the seat or the seats belts will be attached. The car ended up being a mess, look bad, weight more, often loses structural integrity or do not pass tech because for example "we had to cut that tube to install this part'

    It ends up costing more time and more money, it creates frustration and tensions in the team. It shows the inability of the team members to use their imagination of a complete product and to control their emotions by rushing to a "touchable" but unfinished concept.

    Mistakes are often caused by making a decision without sufficient information or evidence. Starting to build a car without accumulating enough evidence of where each car components is situated is a big mistake.
    Claude Rouelle
    OptimumG president
    Vehicle Dynamics & Race Car Engineering
    Training / Consulting / Simulation Software
    FS & FSAE design judge USA / Canada / UK / Germany / Spain / Italy / China / Brazil / Australia
    [url]www.optimumg.com[/u

  6. #16
    Jonny,

    BunMan is right on when he writes "Those cars are over 400 Kg dry and have a lot higher loads to process"... while you car should be in the 200 kg (monocymonder) 230 kg (4 cylinders) maximum driver and fuel included.

    For the same lateral, longitudinal, vertical accelerations with less mass you will have less forces and so for a given stiffness target less material will be needed so less weight and so on..... To push the reasoning at the extreme....how big would your chassis torsional stiffness need to be if your mass was 0 Kg?

    The lighter the car is the lighter it can be.
    Claude Rouelle
    OptimumG president
    Vehicle Dynamics & Race Car Engineering
    Training / Consulting / Simulation Software
    FS & FSAE design judge USA / Canada / UK / Germany / Spain / Italy / China / Brazil / Australia
    [url]www.optimumg.com[/u

  7. #17
    Jonny,

    "- as for weakest point in chassis... It may not matter, because if we build to min amount of metal as per the rules, that may be strong enough regardless of poor triangulation"

    Ok let's say you are right... if your goal is "just to compete" but that is not in the spirit of FSAE/ FS competitions which are engineering exercises. What about performance? What about response? What about driver ability to feel and control the car which has a chewing gum (and probably a huge hysteresis) between the front and the rear wheels?

    *****

    "The bucket for the bearing will be machined first. It will be setup for welding, it will be quickly TIG welded by an expert student (myself). Remove scale and the bearing should go in perfect. (See test sample above)."

    Wrong. The hole for the bearing will be deformed in the welding process. You might still be able to press the bearing in the hole but you will have huge friction which are detrimental to handling and driver feedback. Make a small hole for your jig. then weld, then re-machine with the eaxt tolerances.

    *****
    "We use a shoulder and 1 circlip" So if the shoulder is that important to avoid the bearing to be dislodged from its housing, your left front top wishbone cannot be used on the right front, correct? So more spare parts, correct? Up to you if you want to work had or work smart.... Have a look in catalogue and see how much axial force a circlip can sustain; no need for a shoulder.
    Claude Rouelle
    OptimumG president
    Vehicle Dynamics & Race Car Engineering
    Training / Consulting / Simulation Software
    FS & FSAE design judge USA / Canada / UK / Germany / Spain / Italy / China / Brazil / Australia
    [url]www.optimumg.com[/u

  8. #18
    Quote Originally Posted by Claude Rouelle View Post
    BunMan is right on when he writes "Those cars are over 400 Kg dry and have a lot higher loads to process"... while you car should be in the 200 kg (monocymonder) 230 kg (4 cylinders) maximum driver and fuel included.
    230 kg including the driver? That would mean for a 70 kg driver, 160 kg?

  9. #19
    All the small details, the nuts and bolts of the wishbones, I have my head around that. You missed the bit when I said I had already done a test weld, pic included? We have the capability to machine stuff if needed. But workshop time is valuable. And a shoulder is better than a circlip. And buying 1 circlip is better than buying 2. And machining 1 groove for a circlip is better than machining 2.

    But some things are more important than others. To me, it is about getting a drive-able car, and that is linked to cost. It's not about the cost report, it's about real money to buy real things. Using a few 7/16" spherical bearings is not going to blow the car from 200kg to 500kg. Instead it is going to build in reliability, and save real money. The tilt jig is capable of 2000kg. All the rod ends and bearings will be from our 2001 car. The students are dumbfounded that these Aurora bearings measure funny and are not metric, as we havn't been taught inches yet in our degree.

    Claude, I was going to say you are wrong about many assumptions you have about our team, and that you are even wrong about the competition. But I was the one that lay the bait. You took it, hook line and sinker.

    But I will say this. You can not give me an example of a team that designed a whole car from scratch in CAD, then just built it with minimal changes. If you do try and give me an example, it will just say that that team had the previous years car to work from, which effectively was the "try it and see" proto-type.

    Also, if this is just an engineering competition, then the students should not have to build anything (unless they themselves are qualified tradespeople). If this is just an engineering competition, then the students should not have to drive the car, because then it would be motorsport (which it is).
    University of Tasmania (UTAS)

  10. #20
    But we have spent a lot of money on this:


    It's not my project so I can't speak about this. But it will be data acquisition of chassis stress/movement/stiffness, as well as logging suspension movement. The focus will be on chassis, not suspension.
    University of Tasmania (UTAS)

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