INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Jobs

Automatic VS Manual transmission architecture

Automatic VS Manual transmission architecture

(OP)
Hi,

I just learned that automatic and manual transmissions don't have the same mechanical architecture. The first thing that came in my mind is why. Why manual transmission use 2 parallels shafts and the automatic transmission planetary gear set. (There are probably some exceptions but lets keep talking about the general case) What are the avantages and incovenients of each one?

Jean-Philippe

RE: Automatic VS Manual transmission architecture

Expensive planetary gearsets lend themselves to clutches and bands, which don't lend themselves to manual operation, while cheaper spur gearsets lend themselves better to synchronizers which are almost self engaging manually. My mind went blank trying to synchronize a planetary gearset:)  

RE: Automatic VS Manual transmission architecture

The above post is correct, but it's worth noting a couple of exceptions.

Although I don't know about their current models, Honda and Saturn automatic gearboxes in the past have used the same dual-shaft architecture as a manual transmission, with hydraulic multi-plate clutches engaging each gear in turn. So, it is possible to do it that way, it just hasn't been conventional. The VW/Audi DSG dual-clutch transmission uses the architecture of a manual transmission, including the synchromesh engagement.

The Ford Model T used a manually activated planetary gearset, but the way it was operated using foot pedals is hardly consistent with how automotive controls operate nowadays. A person who knows how to operate any manual transmission vehicle built in the last 50 years wouldn't have a clue what to do when sitting at the wheel of a Model T.

Planetary gearsets with the torque being transmitted through multiple paths (one path at each planet gear) lead to very high torque capacity for the size of the gearbox, too.

RE: Automatic VS Manual transmission architecture

The difference in architectures are due to the gearing. In a manual transmission (including AMT and DCT), a set of helical gears are used. The coupling of a gear set is best performed using a synchronizer and dog clutch, which are relatively cheap to manufacture, and have low parasitic losses. In addition, a typical manual transmission will not have a hydraulic pump, so actuation of a multi-plate clutch would not be possible.
The exception here is the DCT, which will have a small hydraulic pump. In this case, the pump is used to actuate the synchronizers to select the ratio, and to actuate the servos on the dual clutch to perform the ratio change. The use of multi-plate clutches in this type of transmission would result in higher parasitic losses, which would defeat the purpose of using the DCT.
For the typical automatic transmission, a planetary gear set is used, which is a more power dense gear set, and allows the transmission (rear wheel drive) to be on a single axis. For these transmissions, you could use a dog clutch, however, a multi-plate clutch is easier to control and allows power-on shifting (no de-coupling of engine torque during the shift)

RE: Automatic VS Manual transmission architecture

Brian, one of the locals had a T coupe at the  car show last month and made it available to anyone that wanted to sit in it.  The spark advance and throttle were okay to most (very similar to my 30 Model A ).  The starter button on the floor, too.  However, the "three pedals" just had everyone stymied...totally.  Not a single person, even guys my age that should have known, did not have a clue.  Even after attempts at explanation...no clue.  I'm not sure what that says about today's driver...........

Rod

RE: Automatic VS Manual transmission architecture

so one was brake, two clutches?

MfgEngGear

RE: Automatic VS Manual transmission architecture

my Pappi had one of these, when he was a youngster.

lol thanks for the link.

Mfgenggear

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close