http://auto.howstuffworks.com/...x.htm

Periodically, I read articles on this site (www.howstuffworks.com). This one is interesting. The inner workings of a sequential gear box.

 

cool read. thx for the link!

 

"The advantage of this system is that shifting mistakes are impossible. You always go to the next gear."

Unless you get a false-neutral.

 

cool . . . I've been wondering about this lately tho . . .

"On a sequential gearbox, you simply push the lever up for every gear change. "

reading that and looking at the pic below would indicate that to upshift you push forward (towards front of car) and downshift pull back (towards back of car). Is this correct? The reason I ask is because in my mind all these years I've thought of it as the opposite. Upshifts are a pull-back motion while downshifts are a push-forward motion.

 

Because its talking about a champ car engine is in the back it may be backwards for them. Where the tranny is up front youpull on the lever to go up gears and push it forward to downshift. Same with my GoKart.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nonsense &raquo;</TD></TR><TR><TD CLASS="quote">cool . . . I've been wondering about this lately tho . . .

"On a sequential gearbox, you simply push the lever up for every gear change. "

</TD></TR></TABLE>

 

i've been hearing stories about how some bmw drivers are blowing their engines with the new SMG:

the wheel's been rotated 180 degrees, which means up/down are reversed, and guys go to grab the next gear up, and downshift at redline instead.

kinda makes me nervous.

also, when i'm shuffesteering there are times when neither of my hands are close to 3 and 9, which makes it hard to actuate the shifter were i to be in a sequential car...

 

that makes no sense. BMW SMG are fully eletronic controlled so it shouldn't downshift unless the rev at current gear is at a low enough point.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ghettoracer &raquo;</TD></TR><TR><TD CLASS="quote">that makes no sense. BMW SMG are fully eletronic controlled so it shouldn't downshift unless the rev at current gear is at a low enough point.
</TD></TR></TABLE>

Agreed i used to be a BMW tech of the problems with the SMG that was not one of them

 

I don't know about blowing engines but I did run into the experience of being crossed up and and hitting the wrong button.

When we were loaned an SSMG for Koni development on the M3, I looked at the standard location console shifter and thought "Who the hell is going to use that when you what shifters on the wheel?". When I took it out for a drive, I headed up a road wiuth extremely tight switchbacks where the wheel was turned quite a bit. I normally shuffle steer when the wheel is going more than 90 degrees from normal. Several times I basically lost track of which paddle was which and shifted up when I wanted to go down. I quickly realized that when the wheel is turned enough that you lost your frame of refernece, the console shifter was the one to use.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ghettoracer &raquo;</TD></TR><TR><TD CLASS="quote">that makes no sense. BMW SMG are fully eletronic controlled so it shouldn't downshift unless the rev at current gear is at a low enough point.</TD></TR></TABLE>

i would imagine that that would be the case, but i hear what i hear?

i've never driven one so i don't have a real opinion on it, and it could be internet neatofanboy talk, which i fully admit to listening to in this case or even propogating, but it does bring up an interesting question:

preventing you from downshifting at redline is obviously a good thing, but how many other decisions should the computer make for you and at what point does that take away from the experience? at what point does the computer say, let you or not let you downshift? and are there other decisions that you may or may not make on purpose that the computer will override?

Lee: that makes sense

 

The current M3's were blowing up at an elevated rate before the smg was available and BMW was blaming the drivers. Then SMG came out and a similar percentage of motors were still blowing up. A few months later they made changes to the bearings and replaced parts on certain build dates of motors. They also spec a really expensive, super wide range oil; something like 10w60, synthetic of course. I've seen nothing that suggests the SMG caused the blowups.

As far as concerns about the transmission deciding what you can do, what is your feeling about rev limiters? ABS? Traction control? I see plusses and minuses on all of them. The new M5 forces you to buy SMG or a different car, is this bad or not? Given the price tag and the likely problems with all these controlls as the cars get older, I doubt I'll ever have to worry about it myself but it raises questions about where things go as these technologies trickle down to cars normal joes can afford.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mohudsolo &raquo;</TD></TR><TR><TD CLASS="quote">
As far as concerns about the transmission deciding what you can do, what is your feeling about rev limiters? ABS? Traction control? I see plusses and minuses on all of them. The new M5 forces you to buy SMG or a different car, is this bad or not? Given the price tag and the likely problems with all these controlls as the cars get older, I doubt I'll ever have to worry about it myself but it raises questions about where things go as these technologies trickle down to cars normal joes can afford.</TD></TR></TABLE>

Yeah it's not a cut and dried case of "I, the driver, demand full control" since i do like rev limiters and at this point ABS. Traction control as it filters down to us, no.

You have to admit though, that at some point there will be a car that practically drives itself, (Lexus computer controlled cruise control, for example), and while i'd appreciate it on my morning commute, i'd hate to have to fight the car's bells and whistles as well as physics to get it to drive the way i want.

about the M5: yeah i'm bummed that there's no traditional 6speed box in it, and i'd probably prefer the e39(?) m5 anyway. or, true to rr/ax form, a C6 Z06

sequentials are new to the market, and i recognize their empirical superiority, but i think carmakers have a long way to go before they're nailed down, design or otherwise.

 

I have a Golf 1.8t as a daily driver, for sale as a by the way, and ran it at a track school a few years ago at Lime Rock. Dead stock, 4 door on skinny 15" Goodyear all weather tires. Twice I forgot to turn off the traction control. Each time I had to really work to keep the car on the track as it decided to save me from wheelspin by applying front brakes when I was trying to power out of turns. The system is so conservative that in the same turns with it off, there was zero noise from the tires. This "helper" is a good example of building to the least common denominator. Ask me what I think of a car with well known three wheeling tendancies that has 3 channel ABS and will shut off the brakes if one back tire isn't turning.

BMW has been at the forefront of automotive electronics since the 80's and a number of their cars have become a nightmare to keep everything working as they have aged. I fear all cars are heading in that direction. As far as the car driving itself, look at F1 a few years ago, or the competition mode on newer 'vettes. An average driver can get within a few percentage of what a topnotch one can do without the helpers. I've also seen two drivers who rely on ABS destroy tires when it stopped working. In both cases they kept the pedal on the floor and ground holes in the front tires I could reach my arm through. In both cases there was plenty of room to release the brakes and re-apply less agressively but they never tried. Average driver relying on "help" to go fast?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ITAIntegraLS &raquo;</TD></TR><TR><TD CLASS="quote">Because its talking about a champ car engine is in the back it may be backwards for them. Where the tranny is up front youpull on the lever to go up gears and push it forward to downshift. Same with my GoKart.</TD></TR></TABLE>

yeah that is what I though too. I'd think that the linkage would be set up so that it's the same across the board. It's kinda funny, I've never driven a car with a seq. gearbox (ridden motorcycles tho), but when I was driving a rented Mitsubishi Diamante with the "sequential shift" option it was "backwards" to me. Whenever I used the shift mode I'd shift the wrong way. It seemed completely wrong to me

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nonsense &raquo;</TD></TR><TR><TD CLASS="quote">

yeah that is what I though too. I'd think that the linkage would be set up so that it's the same across the board. </TD></TR></TABLE>On the bike-engined Radicals, and probably many other cars, with a small linkage flip, it can be set up either way - just a matter of driver preference I suppose.

 

None, zero, of the street cars that use sequential shifting use a mechanical linkage. All are completely electronically controlled. The direction to shift is entirely up to the car designers. In theory, if you knew how to work the program, you could program it the way you like. I would be inclined to have it pull back for up and forward for down. I like the setup I've seen on some WRC cars with a full ring that pulls toward the wheel for up and away for down. I think that's a better design than separate up and down paddles that don't rotate with the wheel.

 

BMW's SMG in the M3 isn't really like the dedicated sequential gearboxes you see from Hewland or Quaiffe. Its a regular automotive, manual gearbox, with hydraulic actuators.

The gearbox controls, however, are electronic and will prevent you from downshifting too many gears. This also means the actuation (paddles and/or a gear lever) is totally electronic, and its up to the engineers to choose whether pushing the lever forward or backwards denotes upshifting or downshifting. Ditto for the paddles: You can either have the right paddle be upshift and left downshift, or have two way paddles (pull forward = upshift, push back = downshift).

An interesting bit of tech tidbit: The new 7 speed SMG gearbox on the M5 wasn't layed out like a typical gearbox (which places the gears so that the typical H pattern results). Instead, 1st and 2nd gears are placed in the strongest sections of the gearbox. This means the shift patter isn't a typical "H"... it would be far too complex for a person to manually shift, but computer controlled hydraulic controls don't care!

Quaffes and Hewlands are like a motorcycle transmission. You must go through each gear. The connection between the shift lever and the gearbox is generally completely mechanical. There are systems on the market which adapt a solenoid to actuate the gearbox and paddes or buttons to control the solenoids.

 

I'm surprised the SMG would allow a destructive downshift... I know for a fact that a Legacy GT auto won't, as I pulled the lever back expecting an upshift from 2-&gt;3rd when in fact I was "downshifting" during an autocross. The computer saw through my idiocy and didn't allow any damage to occur. I was impressed that the GT would hold 2nd gear when I bumped the limiter, which was good since a gearshift in the middle of the slalom I was negotiating would've been much more disruptive than bumping the limiter.

The bike engine stuff should generally be reversible since as JZR said, the shift linkage can be flipped. I've installed the linkage backwards accidentally on a street bike and it had this effect.

Good ABS systems are easy to rely on. I give you the example of two friends I took to the kart track recently. The one who drives a E46 M3 (ie, ABS of God's Creation)
struggled with braking technique MUCH more than the other who drives a '71 Fiat who actually had to learn to squeeze the brakes properly in order to keep the unforgiving mid/rear-engined car with NO aids whatsoever from spinning out.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by WRXRacer111 &raquo;</TD></TR><TR><TD CLASS="quote">The bike engine stuff should generally be reversible since as JZR said, the shift linkage can be flipped. I've installed the linkage backwards accidentally on a street bike and it had this effect. </TD></TR></TABLE>

Our Formula SAE Team purchased a wrecked Honda CBR600 F3. We got it in the shop and were shifting the bike between 1st and 2nd to try and get it in nuetral. It turns out the previous owner flipped the linkage, and we were actually between 5th and 6th... DOH!

The previous owner did a good job of beating on the bike up until he wrecked it. The shift linkage was flipped (which I assume was for drag/street racing), rear tire was totally bald in the center and hardly worn at the edges, JB Weld on the head, and the bike had been laid down once before (fiberglass patches over the backs of the panels, the panels had been repainted from white to black, and the gas tank didn't match).

Jonathan

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BUJonathan &raquo;</TD></TR><TR><TD CLASS="quote">

Our Formula SAE Team purchased a wrecked Honda CBR600 F3. We got it in the shop and were shifting the bike between 1st and 2nd to try and get it in nuetral. It turns out the previous owner flipped the linkage, and we were actually between 5th and 6th... DOH!

The previous owner did a good job of beating on the bike up until he wrecked it. The shift linkage was flipped (which I assume was for drag/street racing), rear tire was totally bald in the center and hardly worn at the edges, JB Weld on the head, and the bike had been laid down once before (fiberglass patches over the backs of the panels, the panels had been repainted from white to black, and the gas tank didn't match).

Jonathan</TD></TR></TABLE>

the bike guys flip the shifting for preference and correct me if I'm wrong but most race bikes are setup that way. After riding my friend's bike, upshifts are easier while accelerating hard.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CRX Lee &raquo;</TD></TR><TR><TD CLASS="quote">I don't know about blowing engines but I did run into the experience of being crossed up and and hitting the wrong button. </TD></TR></TABLE>

Just curious - why were you shifting mid-corner? Doesn't seem like a good idea, regardless of shifter and transmission type.

 

read carefully, in the next paragraph Lee explains it...

"When we were loaned an SSMG for Koni development on the M3, I looked at the standard location console shifter and thought "Who the hell is going to use that when you what shifters on the wheel?". When I took it out for a drive, I headed up a road wiuth extremely tight switchbacks where the wheel was turned quite a bit. I normally shuffle steer when the wheel is going more than 90 degrees from normal. Several times I basically lost track of which paddle was which and shifted up when I wanted to go down. I quickly realized that when the wheel is turned enough that you lost your frame of refernece, the console shifter was the one to use."

 

Does anyone have any pictures/diagrams/sliced views of how the ratched on the manual systems work? It's a two way ratched, working both ways on the fly.