Sequential in Autos?

[ZoomZoom]

Just a stupid question I was thinking about. Why aren't sequential manual transmissions (like a motorcycle) popular in cars?

 

[evelrod]

I don't suppose there are any stupid questions, only stupid answers---

1) Cost to retool from the system in use since the 1920's to a modern sequential box of sufficient strength.
2) Reluctance in OEM management to change from the "tried and true". ("If we can't sell it, you can't build it.")
3) The inability/reluctance of the general public to accept anything new or different, eg. the new CVT's. (re: #2)
4) Sequentials I have tried (race cars) are not very smooth in low speed use (street?) but I am sure that could be attended too should there be a sudden change in demand. The clunks and lunges you readily accept on a high hp, low weight bike would be unacceptable in car.

As I recall, several Japanese cars of the 70's and, I'm sure, many others that I don't know of, had motorcycle engines and/or sequential trans. Many of the current high dollar high performance cars have sequential boxes, paddle shift, etc.---eg. the new Ferrari. As far as I know, not in the "grocery getter" catagory---yet!

Rod

 

[ZoomZoom]

My guess is if a company came up with a sequential transmission for say a honda civic, subaru WRX, and other sport compact cars, the company would be rolling in $$$. Kids these days spend couple grand on wheels and tires alone, you can't imagine the $$ they would spend on something like a solid sequential transmission!

 

[GregLocock]

It's not much of a change to the mechanism, just a grooved cam to drive the selector rods. A smart person could design their own and test the market. I'll take a 10% royalty for that suggestion.

Cheers

Greg Locock

 

[rpmag]

I believe there are already a couple of versions available, even here in Australia. I believe that there has been some concern that if a gear is 'lost' then it has a much more significant effect as it is almost impossible to drive around in the sequential box as you cannot shift past/through that gear.
Modena engineering is building both a sequential 6sp gearbox and transaxle, the latter for GT40 type replica's

 

[DesignOutsourcing]

At Automechanika a few months ago, LUK had a very nice little AMT (Automated Manual Transmission) system on display. It is a compact electro-hydraulic system which bolts onto existing manual transmissions and does the clutch and gear changing for you. It is activated by paddles or a "sequential" floor mounted gear lever.

It is quick and even has a hookup for the engine control system to cut the engine for a few milliseconds for the change up. It is already offered on several European cars as an option. The OEM cost of the system is about 150 euros and the option is being offered by the car companies at about three times this.

I think it has huge aftermarket potential. cheers, derek

 

[NormPeterson]

Best guess I've got as to why sequential gearboxes aren't commonly found in cars is that drivers in general aren't 'plugged in' to the notion of downshifting one gear at a time as they come to a stop. Or of banging away at the selector mechanism several times having finally come to a stop. The majority of drivers do not have motorcycle experience in their background, and can be expected to view this only as an inconvenience. Keep in mind when thinking in terms of 'convenience' that only a few percent of the cars and light trucks sold are equipped with a manual transmission of any sort.

If you could find a way to get past that operational issue or, alternatively, make it a bigger part of the appeal (here's where the sport-compact marketing comes in), I think you might well find wider/earlier acceptance.

Norm

 

[gerhardf]

Norm, as a side note: I'm not really sure, but I think the worldwide percentage of cars and light trucks with manual transmission is over 50%. AFAIK, the USA is the only country worldwide where automatic transmissions dominate in this market. (But not much known about sequential transmissions either...)

 

[crysta1c1ear]

America is not the only country where automatics are preferred. Transmisions are going drive-by-wire and the number of gears is increasing. There comes a point where an H-gate is clumsy to use and +/- controls become more intuitive. I don't expect my two seater sports car with 7-speed dual clutch transmission to have an 8 position H gate (if you include reverse) when I get it.

So car companies are designing transmission controls like this.

That's an Audi picture, but I can find similar pictures for almost any manufacturer. Some will be dual clutch, some will be AMTs. Getrag have designed AMTs with two electric motors for the gear changes, so that the changes don't have to be sequential - either motor can move, or maybe even both at once, give several possible gear changes. But if you consider just one motor, or a dual clutch transmission restricted to go {1,3,5}<->{2,4,6} then it makes sense to give the driver a sequential control. If the driver has an H gate and goes 4 to 2 the gear change would feel odd to him going 4 to 3 to 2. If you make him operate a +/- control twice, it will seem more natural to him. After a while, these controls will probably be left in drive anyway: Europeans (used to manuals) will get accustomed to a lazier approach to driving as traffic and the number of gears goes up, and automatic modes become available due to drive-by-wire transmissions, without the losses of conventional ATs.

So for things like the AMTs and dual clutch transmissions, sequential user interfaces have a logic behind them. Another note - maybe I got it from this thread, I'm not going to check - is that drivers complain about the length of time AMTs take for a gear change. Its not that they are slower than manuals. In a manual, a driver is busy for the duration of the gearchange and not really consious of how long it takes. If he presses a paddle shift, for him the oeration is over, and yet for the transmission it has just started. This makes the driver much more aware of the duration of the shift. Getrag's AMT2 cut the duration of the shift, to reduce the nodding dog effect. Getrag's AMT3 increased the duration again - with powershifting making the shift smoother, the incentive to cut the shift time was removed.

Now Powertrain Limited is developing 6-speed transmissions which powershift like a dual clutch transmission, ie clutch-to-clutch shifting, (well friction plate to friction plate, as some are brakes), but from any gear to any other, eg direct 4 to 2 and not via 3rd. They can do this by having a set of friction plates per gear ratio, 6 in all. (They just release the friction plates for the offgoing gear and simultaneously activate the friction plates for the oncoming gear.) Here the incentive for a sequential driver interface is removed again. It will be interesting to see what driver interface they use.

Honda sequential mode gearchanges.

What goes around, comes around.

 

[ZoomZoom]

My original question was more to do with historic reasons for adopting transmissions with a typical H-pattern for shifting gears. If I was an engineer for GM in the '50s, I would have tried to get a sequential transmission to be untilized instead of the H-pattern.

 

[ZoomZoom]

ooops, I meant "utilized".

 

[crysta1c1ear]

Zoom
Maybe you can tell us why you as an OEM engineer in the 50s would want to give customers a restricted level of service?

I have a 5-speed manual. I'll often accelerate 1,2,3 and then have reach the speed limit for the country road I'm on and drop it into 5, or accelerate 1,2, and have reached the speed limit for the village I'm driving through and go straight from 2 to 4. I have friends that drive a bit more agressively that will regulary drop a couple of gears to overtake.

I see little reason to make these operations more difficult.

 

[patprimmer]

I agree with crystalclear for up to 4, or possibly 6 speed transmissions, but as the # of gears increases, and the ratios get closer together, and cars get quieter and engines get smoother over a wider rpm range, it does get harder to remember what gear you are in, and to select one that is a known number of gears different to the one you are in, hence the paddle change gets to be more of an advantage than a disadvantage. If you want to go two or three gears at a time, you just hit the paddle two or three times in succession. F1 guys seem to have no problem.

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[ZoomZoom]

crysta1c1ear, well in the 50's a manual transmission had what 3 maybe 4 gears? I don't think too many people would be skipping gears. Further, it's not that hard to shift a sequential transmission two gears, I agree it would be a bit odd, but not difficult. If you want to skip 3rd, press clutch in, push (or pull) lever forward twice and let clutch out.

Obviously a sequential transmission would be geared towards sports enthusiasts. In my humble opinion, a '69 Camaro would be more inticing with a sequential transmission than a regular H-pattern. But that's just me!

 

[crysta1c1ear]

There are trucks with automated manual transmissions and sequential lever shifting. There can be two push or pull positions, the second postion harder to find, rather like finding reverse on some cars - the lever meets resistence and a more solid force applied to the lever overcomes the resistance and allows the second (more remote) lever postion to be attained.

I think that's not a bad solution to the occasions when you want to knock down a couple of gears at once.

==

F1 drivers ...
I read something, and I think it was in the context of Le Mans or DTM racing, that drivers are irritated by the counting that they mentally do while braking for bends, eg 6, 5, 4 ,3, so that they have the right gear on exit. The reason its particularly annoying to them, is that the bend is what requires particular attention, correct braking point, hitting the apex, modulating the throttle precisely (or pumping it in the case of Senna), etc.

I'm not sure if the F1 remark was serious or tongue in cheek, but that is my tuppence worth, for what its worth, maybe not a lot, and maybe tuppence!

 

[icrman]

Its much easier to take an automatic transmission and
put a clutch in place of the torque converter.
That was very popular in the drag race circles in the late 60's and early 70's. They used one of the 3, Torkflite, Turbohydramatic, Cruiseomatic. Chopped off the bell housing and bolted an adapter to the front pump/stator support area, and had a drive spyder to engage the through out fingers on the pressure plate to drive the pump.
There ya go a perfect non gear clashing inline shift pattern, impossible to miss a shift, semi automatic transmission.