Unusual ways to change gear, cont'd

"Cé hé sin" (michael-m-mouse) 01/16/2020 at 19:10 • Filed to: Cotal, Semi automatic

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Time to go to France and things French, like the very French Cotal semi automatic electromagnetically operated gearbox.

Yes, it’s a bit of a mouthful. It was de rigueur on luxury (and some not so luxury) French cars between the wars and on to the 1950s. Designed to spare the driver the considerable inconvenience of learning to change gear quietly and smoothly in the pre synchromesh era, it used instead a pair of epicyclic gear sets and four electromagnets. The epicyclics provided the ratios and the electromagnets were an alternative to other means of engaging friction materials.

To begin, here’s an epicyclic about its business.

The central gear is the sun wheel, the smaller silver ones orbiting about it are planet wheels which are attached to a red planet carrier and around all these we have an annulus or ring gear (or as Cotal called it, a couronne or crown). If you hold one of these elements (sun, ring or planet carrier) still, apply power to a second and take power from a third you can in principle obtain two overdrive speeds, two reduction speeds and two reverses. Join any two elements and you obtain direct drive with no reduction or multiplication. In the gif, the ring gear is blocked and the planet carrier is turning more slowly than the sun gear. If you drive the sun and take power from the planet carrier you’ve got a reduction gear.

The Cotal had a pair of these, each equipped with two magnets and each providing a different reduction gear (which is crucial).

For the first of its four speeds, the first gearset is just as above. The engine drives the sun, one of the magnets blocks the ring gear and drive is taken at a reduced speed from the planet carrier.

Now the tricky bit. The planet carrier drives the ring gear of the next gear set. The sun is blocked by another magnet so the planet carrier turns in the same direction as the ring gear, but slower. We’ve now succeeded in reducing the rotational speed in two stages.

Next up is second gear. The first epicyclic stays as it is but the second is lo cked by another magnet and doesn’t provide any reduction so the output shaft is now turning faster.

Third comes next as you would expect. Remember how the two epicyclics are different? That’s important because there’s now a swap. The first epicyclic is locked (no reduction), the second has its sun blocked (another magnet) and provides a reduction but less so than the first gear set. That’s a higher gear.

To finish off we lock both epicyclics so no reduction and direct drive.

There was also an overdrive version which arranged the second epicyclic differently.

So overall, power going left to right:

Ist low-low

2nd low -high

3rd high- low

4th high-high

To control all this, a little lever in a little gate, like so:

It was called a moutardier, a mustard pot, because it looked like a spoon stuck in an old fashioned mustard pot.

You’ll notice we haven’t mentioned going astern. The epicyclics didn’t lower themselves to that so there was a separate reverser built into the front of the box, resulting in principle in four gears in each direction. In practice you were supposed to use third in reverse because the latter was much lower than forward and first reverse was therefore so low that the torque would do the rest of the transmission an expensive mischief.

Also unmentioned is stopping and starting, handled by a traditional clutch and pedal. You can see the lever in the first image.

So now you know how to deal with driving your first Delahaye. They nearly all had Cotals.

4kc > Cé hé sin 01/16/2020 at 19:34

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Thank you for doing these

“An expensive mischief" is my favorite thing I've heard all day

just-a-scratch > Cé hé sin 01/16/2020 at 19:59

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Thanks for the excellent article. I hadn't heard of these before.

feather-throttle-not-hair > Cé hé sin 01/16/2020 at 20:42

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Ow, my head.

But also I love this series, thank you!

Urambo Tauro > Cé hé sin 01/16/2020 at 21:06

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That little shifter is just too cute. I bet the proper shifting method looks a little something like this:

Jim Spanfeller > Cé hé sin 01/16/2020 at 22:59

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This is cool. I love weird F rench cars; they’re so mechanically fascinating.

MiniGTI - now with XJ6 > Cé hé sin 01/16/2020 at 23:10

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I feel like I’ve seen a miniature gear lever like that in an American car of the same time period in a museum somewhere. Did Tuckers have something like that?

winterlegacy, here 'till the end > Urambo Tauro 01/17/2020 at 00:27

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French cars seem to be one of two things: incredibly delicate machines or things you beat on hard to make them work.

kanadanmajava1 > Cé hé sin 01/17/2020 at 04:19

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Cotal transmissions were mostly used in very expensive cars but Ford Vedette is one exception. They are still somewhat affordable and this ‘51 convertible could be bought for €25,5 00. Sedans are more common and of course much cheaper.

Cé hé sin > MiniGTI - now with XJ6 01/17/2020 at 07:26

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Bendix preselector used by Cord.

Cé hé sin > kanadanmajava1 01/17/2020 at 07:28

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I saw one for sale for about €7,000 a couple of years ago.

kanadanmajava1 > Cé hé sin 01/17/2020 at 11:42

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That would a nice price for car with a very interesting transmission.

Cé hé sin > kanadanmajava1 01/17/2020 at 12:50

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I’ve checked again. Advertised for €7,500 in 2016.Couldn’t find any for sale now.