Issue: June Vol: 2014
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Contents

[p.1] 2014 Freedom Sprints

[p.2] CTT and PDX Reset!

[p.3] Pueblo Majors - Shifting Gears

[p.4] Records Fall Saturday at Pueblo Majors

[p.5] Mid-States Majors Wraps in Pueblo

[p.6] Audi Welcome Porsche Back To Le Mans

[p.7] Transmissions – Floppy Whoppies

[p.8] Pit Rally - Gambler's Edge

[p.9] SnakeBytes

[p.10] SCCA Set to Host Formula SAE Lincoln

[p.11] Classifieds

[p.12] Advertisers Quick Reference

Transmissions – Floppy Whoppies

By ROWONE

As a mechanical engineer, my friends know I am a bit outspoken when it comes to racecar design and driver controls in a racecar. I believe cars in professional series should push the boundaries of technology while keeping cost in check and providing vehicles in which drivers can showcase their talents. What drew me to cars as a kid and even now are gear changes and the sounds – both of which are quickly becoming extinct in an increasingly complex sport riddled with politics and money. One of the challenges I enjoy as stated above, gear changing, has been nearly eliminated in pro racing with the widespread use of paddle shifters, which I refer to as floppy whoppies due to my intense dislike of them. I love the challenge of clutchless down and up shifts, really mastering my skills behind the wheel of a car I have complete control over, and learning to do things average drivers cannot do. Please do not judge me as old school, but there is no denying the connection between “man and machine” is much stronger in older racecars without such controls as opposed to newer ones. Any driver can flip and flop paddles. If you think I am stubborn, my father who is also a mechanical engineer does not even believe in rev limiters and drag raced a modified ’57 Chevy back in the day without a tachometer since he could not afford one! I do however acknowledge that times are changing and that I am in the extreme minority when it comes to being a car customer. Besides my older sister and myself, I do not even know of anyone personally who took his or her driver’s test on a standard shift.

As an engineer I am strongly encouraged by management to prevent technicians making assembly mistakes and the ultimate user making operator mistakes by robust design which takes away as much freedom/control from both. As things get more complex in this world we engineers support greater and greater roles in this endeavor of “dummy-proofing” and automation (thoughts from the Pixar movie WALL-E come to mind). One thing which has made me feel a little better over the years is that paddle-shifted transmissions are finally being correctly categorized as semi-automatic, automatic, or twin-clutch automatic transmissions. The driver is not shifting, the computer is in complete control. The main focus of all my racing articles is driving technique and not technology, but I feel having a basic understanding of evolving car technology is an essential element to becoming a successful racecar driver.

Two main paddle-shifted transmissions out there are the twin-clutch design and the CVT (continuously variable transmission). The twin-clutch designs generally are more efficient in terms of transferring power from the engine to the drive wheels and can transmit large amounts of power if designed properly for the application. The CVT is primarily for regular street cars and not suited to transmitting large amounts of power due to the nature of its design. It is also generally a little more power parasitic when transferring power.

The twin-clutch design is just that – two concentric shafts with a clutch on each. The odd gears are on one shaft and the even gears on the other. The computer controlling the transmission knows whether the vehicle is accelerating or decelerating and preselects the next gear and matches the engine rpm to the transmission. When the driver hits the upshift or downshift paddle, one clutch in the transmission disengages and the other one engages. Bottom line – the computer is doing the shift, you are just giving the clutch disengage/engage command. This is the direct opposite of how a driver does a clutchless up or downshift in an old-style H-pattern gearbox. Also in that case the driver is in control and not a computer (refer to MAGAZINES, BOOKS, AND AN STi – July 2013).

I got the opportunity to drive a car with a CVT transmission with paddle-shifters last year – a 2013 Subaru Impreza. When it comes to the basics of a CVT, think of F500s in SCCA. Engine rpm stays constant right in the power band while you accelerate full throttle (think lawn mower drone – boo!). Although a CVT is continuously variable, its overall gear ratio range is limited once set. Another good example to understand how they work would be to look at a snowmobile or a small utility vehicle. There is a primary clutch on the output shaft of the engine and a secondary clutch on the input shaft of the remaining transmission. Both are usually spring actuated and have a belt that rides on dual cones on each one. As the vehicle accelerates the primary develops a larger pulley radius and the secondary develops a smaller one. These things can be tuned by changing the springs, ramps, etc. for an engine’s particular power band characteristics. We used them in my Baja SAE team in college. They can be a real pain to tune.

Well, I hadn’t driven this Subie 5 minutes when I put it in “manual mode” and started messing with it. In manual mode, the continuous CVT becomes something like a 5 or 6 speed fixed-ratio transmission with distinct gears (I cannot remember how many it had). I tried to start from the highest gear at a stop sign and the thing would not go any higher than second gear no matter how many times I hit the upshift floppy. Strike one – computer will not let you start from a stop in anything higher than second gear. I tried being stupid and got the car up to fifth gear and refused to downshift to the next stoplight. Strike two – the transmission automatically shifted itself back down to first. While shifting in manual mode, one could keep higher revs and even get engine braking, but the car just did not shift as smoothly in manual mode compared to being in automatic mode – strike three. After that, I put the car in drive, put myself in grandma mode, and drove home – disappointed and annoyed because sometimes the paddles would get in my way while working the steering wheel through corners.

Although I am disappointed where transmissions are going in terms of sacrificing driver satisfaction and accomplishment for reliability and safety through eliminating driver error opportunities, I can be happy vintage racing exists and maybe that’s where I will end up one day. As for professional driving, I must look at it like I look at designing things as a mechanical engineer. With the economy as challenged as it is, professional drivers really don’t get a say in what they drive. They are just fortunate to drive for pay and must look at themselves as driving mercenaries as I look at myself as a design mercenary who does not get a say in what I am told to design. However, if a driver is really good he might not be told HOW to drive the racecar he is provided, just as a good engineer might not be told HOW to design something. There’s some satisfaction in that. Competition in racing also gets much closer and more fierce as designs eliminate driving mistakes and variables. I have seen this first hand in the top open-wheel racing series here in the United States where it is not unheard of for the top six qualified cars to be all within .25s for a race (i.e. sixth car is only .25s slower than the polesitter).

Love them or hate them – floppy whoppies look like they’re here to stay.