+ Reply to Thread
Page 2 of 2 FirstFirst 1 2
Results 11 to 20 of 20

Thread: Information about gear shifting

  1. #11
    Senior Member
    Join Date
    Nov 2010
    Location
    NSW, Australia
    Posts
    352
    Federico,

    Velocity isn't really the issue as you can just increase your ignition cut times, but at that point you are slowing your shifts and the whole point of the system is lost. What engine are you using? If you've done your gearing appropriately and have a reasonable power spread then it's likely that on a typical FSAE track you will only use 2-3 gears. Personally I don't get why people bother with complicated shifter systems when a simple hand actuated stick does the job with much less headache.
    Jay

    UoW FSAE '07-'09

  2. #12
    Quote Originally Posted by Jay Lawrence View Post
    ...I don't get why people bother with complicated shifter systems when a simple hand actuated stick does the job with much less headache...
    Because money-shift.

    There are a number of positive reasons to complicate shifting, but nothing beats a hand-actuated stick for reliability. It comes with closed-loop control and on-the-fly programming!
    Jay Swift
    Combustion Powertrain
    Global Formula Racing 2013-2014

  3. #13
    I agree with you, Jay. But I think the driver has a lot of other thougths during a competition and I find quite disappointing to obligate him to change gear manually.
    The image above is a part of data acquisition in which I show the velocity of the servo. I realised that every time the velocity is lower than a specific value, the gear isn't disengaged. As I said before, our problem should be a lack of torque.

    I would like to make this discussion a clear schedule of the prons and cons of different actuators. What do you think? In this way everybody can have an organic vision of the topic, without headache in searching for dispersed information.

    Hoping to help people in answering their questions,
    Federico

  4. #14
    Federico, your image is very small and unreadable. If you would like anyone to review the data and give their input, please upload it in a larger size.

    Many successful teams run a hand-operated shift stick, such as Monash, UTA, Missouri S&T, Maryland, and many others I am forgetting. And looking at professional racing there are many series that use a hand-operated shift stick (BTCC, WTCC, WRC, many lower formula categories, shifter karts, etc.). Don't rule out a simple sequential shifter.

  5. #15
    The manual option is not a bad option.

    We here at WWU have, in the past, run with a mechanical paddle shift utilizing a push pull cable meant for boat throttles. We have since gone back to a lever though to reduce hand fatigue.

    Many have also run a variation of this setup, integrating a clutch into the downshift side of the paddle with the ability to pull the clutch separately. Oregon Institute of Technology ran one like this in 2012 that was really simple and very functional. I mention this one as it is one that I have seen myself, but I'm sure there have been many others like it.

    I know that this does not get at the specific question of OP, but mechanical shifting should not be thrown. It is a reliable solution that will not hamper the preformance of the car in any large way.
    Last edited by SomeOldGuy; 12-05-2014 at 07:47 PM.
    WWU FSAE
    2010-2011 Chassis/Welder
    2011-2012 Tech Director
    2012-2014 Project Manager/Welder

  6. #16
    If you're driver is having an issue operating a sequential shifter, you have driver problems.

    If you can go faster because of an electronic shifter, and it's cost effective, then you have reason to improve.
    Micah McMahan
    Red Bull Powertrains Performance Design Team Leader
    3MI Racing LLC Owner/Engineer
    Former MSI Defense Solutions - Sr. Design Engineer/Project Manager
    Former Roush Yates Engines - Sr. Design & Analysis Engineer
    ODU FSAE 04 member, 05 controls leader, 06 control/ergo/brakes leader, 07 brakes/MC22 turbo engine/Asst Team Leader

  7. #17
    Quote Originally Posted by Swiftus View Post
    Because money-shift.
    Have problems at some point, Jay?
    Kettering University Vehicle Dynamics
    Formula SAE 2010 - 2015
    Clean Snowmobile Powertrain 2012 - 2015

    Boogityland 2015 - Present

  8. #18
    Quote Originally Posted by MCoach View Post
    Have problems at some point, Jay?
    Only on Chump teams with some chumps .
    Jay Swift
    Combustion Powertrain
    Global Formula Racing 2013-2014

  9. #19
    I have upload a bigger image, it is clear enough to understand what I mean:
    Confronto_forum.jpg
    The picture shows that in correspondence of the vertical yellow line the pink bent is up of the horizontal red line. The red line is a lower limit, below of which the servo velocity is not enougth to complete the shifting. We estimated it around a value of 100 mm/second. When the resistance force is higher than a critical value, probably when the car is accelerating and maybe wheel-sleeping, the velocity reached is too low and the gear finishes not to be disengaged.

    There is no doubt as far as the reliability of an hand actuator. From the other side it is very difficult to predict if an electro-actuated shifter is relevant in terms of seconds per lap, but it is also true that the electronic one makes a more precise driving.

    I want to do anything but to say that one is better than the other, it depends on drivers' habits, it is only a question o design, the result of a choice.
    There isn't the perfect actuator, but a perfect actuator for every team.

    I think we solved our troubles, at least we recognized the main problem.
    Thank you everybody for having actively partecipated in the discussion

  10. #20
    Not to digress, but the 2014 Rolex 24 hours of Daytona overall went to a car with manual sequential shifting in a series where pneumatic shifting is allowed. The car did have flat shifting capability (no clutch up or down), but those transmissions are basically oversized motorcycle transmissions.

    I've become familiar with pneumatic (megaline) which is used throughout Motorsports but I have been interested in electronic options which should be a bit more precise and less physically complex (no separate compressor, valving, lines etc).

    I don't see much in your data, but drum position is probably the most important shifting feedback. It's critical information to recognize when the current gear is not being released(typically not enough power reduction, but also a function of drivetrain stiffnesses), when you hit dog to dog of the next gear and when full engagement occurs. That information enables easier fine tuning of timers and adjusting the logic to recognize the next gear. I will say that downshifting is probably more complex than up shifting, especially with FSAE and rules regarding the throttle.
    'engine and turbo guy'
    Cornell 02-03

+ Reply to Thread
Page 2 of 2 FirstFirst 1 2

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts