Transmission Prototype

"JohnH3ASP" (jh3-21) 01/21/2017 at 12:36 • Filed to: None

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Modern cars have an engine and a gearbox. What if we have a second gearbox in the car?

How It Works

Paddleshifters will be required. The gears will go (from shortest gear to longest gear)

1:1 —> 1:2 —> 1:3 —> 1:4 —> 1:5 —> 1:6 —> 2:1 —> 2:2 —> 2:3 —> 2:4 —> 2:5 —> 2:6 —> 3:1 —> 3:2 —> 3:3 —> 3:4 —> 3:5 —> 3:6

Effectively you have 18 gears, even though you really have 9. I remember a while back Ford tried to make an 11-speed gearbox, but we can have upwards of 30 gears simply. It could also work for an automatic, and if a gear is not needed, you could skip the gear altogether.

Drivetrain

99% of drivetrains follow a simple path of

Engine, Transmission, (Differential), Wheels

My drivetrain would go:

Engine, Transmission, Transmission, (Differential), Wheels

This would increase efficiency in cars, make cars faster, and all by quadrupling the amount of usable gears. Sure, the car would be heavier, and sure, there would be less room, but I am sure manufacturers could solve those problems. Maybe we could put all the gears together, in the same box.

That Bastard Kurtis - An Attempt to Standardize My Username Across Platforms > JohnH3ASP 01/21/2017 at 12:44

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So basically like a splitter transmission in a big rig. Usually rather than three six speeds it’s more like two nine speeds, for a total of 18 gears.

The Crazy Kanuck; RIP Oppositelock > JohnH3ASP 01/21/2017 at 12:49

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So a spiltter.

My bird IS the word > JohnH3ASP 01/21/2017 at 12:50

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They make these under/overdrives for classic muscle cars that operate on a similar principal. I assume there is a good reason for not implimenting them on consumer automobiles.

If only EssExTee could be so grossly incandescent > JohnH3ASP 01/21/2017 at 12:51

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So it’s like an old fashioned overdrive or a two speed rear end but with more gears. Interesting concept, but I feel that the weight of a second whole transmission would negate any economy gains.

jimz > JohnH3ASP 01/21/2017 at 12:51

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Junkrat aka Rick Sanchez: Fury Road Edition > JohnH3ASP 01/21/2017 at 12:52

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Just do it in the diff like some commercial trucks do. If it’s FWD you could make the diff a small CVT. You would have the ability to lock it out at pretty much any gearing, or have it be dynamic and program a 60 speed if you wanted. Just a thought.

jimz > Junkrat aka Rick Sanchez: Fury Road Edition 01/21/2017 at 12:53

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the thing back on the leading axle differential is the “power splitter,” AFAIK. it can lock the axles together in case one starts to slip in low traction conditions.

Cé hé sin > That Bastard Kurtis - An Attempt to Standardize My Username Across Platforms 01/21/2017 at 13:06

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More complex than that - you have a three, four or five speed with a two speed in front and another behind so three boxes.

AfromanGTO > JohnH3ASP 01/21/2017 at 13:19

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So it’s basically a 3 speed overdrive.

FTTOHG Has Moved to https://opposite-lock.com > JohnH3ASP 01/21/2017 at 13:23

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I get what you’re trying to do here, but at some point doesn’t it just make more sense to design a heavier-duty, larger ratio spread CVT than mess with this many gears?

HammerheadFistpunch > JohnH3ASP 01/21/2017 at 13:28

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This is done all the time off road, with doubled up transfer cases.

trans > t-case 1 (2 speed) > t-case 2 (2 speed) > final drive

makes the crawl speed hilariously slow.

TheNeonDriver - Now with More BMW! > JohnH3ASP 01/21/2017 at 14:26

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Didn’t the C4 corvette have something like this set up?

From Wiki:

From 1984 through 1988, the Corvette was available with a Doug Nash “4+3" transmission - a 4-speed manual coupled to an automatic overdrive on the top three gears. This unusual transmission was a synergy that allowed Corvette to keep a stout 4 speed, but add an overdrive

JohnH3ASP > That Bastard Kurtis - An Attempt to Standardize My Username Across Platforms 01/21/2017 at 16:17

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Crap. I thought it was original.

JohnH3ASP > TheNeonDriver - Now with More BMW! 01/21/2017 at 16:18

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Cool!

JohnH3ASP > HammerheadFistpunch 01/21/2017 at 16:18

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Well, cock.

JohnH3ASP > FTTOHG Has Moved to https://opposite-lock.com 01/21/2017 at 16:19

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I almost put something about CVT’s in here, but CVT’s don’t have acceleration or top speed. Ever floored it in a Civic? Nothing happens.

JohnH3ASP > AfromanGTO 01/21/2017 at 16:20

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Sorry, no clue what overdrive is :P

JohnH3ASP > jimz 01/21/2017 at 16:20

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Well, crap. There goes a good idea. Is that an automatic transmission?

JohnH3ASP > If only EssExTee could be so grossly incandescent 01/21/2017 at 16:21

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Economy is not the issue, top speed is.

JohnH3ASP > The Crazy Kanuck; RIP Oppositelock 01/21/2017 at 16:21

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What’s a splitter?

jimz > JohnH3ASP 01/21/2017 at 17:03

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manual, for heavy trucks.

jimz > My bird IS the word 01/21/2017 at 17:04

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muscle cars had 3 speed automatics, now we have 8-10 speeds. at some point increasing the ratio spread even more doesn’t get you anything.

jimz > JohnH3ASP 01/21/2017 at 17:06

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easier to link this:

http://www.wikihow.com/Shift-a-Semi-Truck

jimz > JohnH3ASP 01/21/2017 at 17:10

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“overdrive” is any gear ratio where the input gear is spinning slower than the output gear. usually expressed as fractional gear ratios e.g. “0.75:1"; for every revolution of the output gear the input gear will only have turned 3/4 of a revolution.

lower gears (on a car, 1st through 3rd) are “underdriven,” where the input gear is spinning faster than the output gear. e.g. a 4:1 gear ratio. this also has the effect of multiplying the engine’s torque output.

jimz > JohnH3ASP 01/21/2017 at 17:13

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any vehicle’s top speed is going to be drag limited*, meaning they simply don’t have the horsepower to go any faster. Drag (as a force pushing back on the car as it moves through the air) increases with the square of the car’s speed. meaning, if you go twice as fast, the air will “push back” four times harder. Worse, the horsepower required goes up by the cube of the car’s speed, so you’ll need 8 times the power to go twice as fast. adding more gear ratios isn’t going to help.

*exceptions are cars with electronically limited top speeds; usually done to protect the tires or other driveline components.

If only EssExTee could be so grossly incandescent > JohnH3ASP 01/21/2017 at 17:29

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In a vacuum, more gears will increase speed. Thet’s not necessarily true in real life applications. There’s two ways for a car to hit top speed. One, it doesn’t have enough power to overcome wind resistance and stops accelerating. This is the case with 99.9% of all cars “maxing out”. The other reason a car would hit top speed is if it’s under-geared, and it’s hit redline with no more gears to change up to. You only see this in very specific cases, like an old car that’s been given a ton of power but still has a 3 or 4 speed transmission. The vast majority of cars however, are aerodynamically limited instead of mechanically limited.

My bird IS the word > jimz 01/21/2017 at 17:36

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My problem is implimentation. My mini has a six speed, but the overdrive is way to short. Awful to drive at 60 mph. no excuse, my trans am pulls 2500 rpm on the freeway. It does have a dogshit 2.41 rear axle though.

BloodlessWeevil > JohnH3ASP 01/21/2017 at 18:09

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This is essentially how transmissions are developed. Adding planetary gear sets in an automatic or just more gear sets on the lay shaft/output shaft of a manual. However, as some other commenters have pointed out, multiple units are sometimes used.

Additional gears increases efficiency by lowering RPM at a given speed. This was the original reason for overdrive ratios and the impetus behind the current trend of adding gears, but keep in mind that the engine must be able to produce enough power to move the vehicle at that speed and might need to downshift to accelerate.

Adding gears might help acceleration, but there is a limit as shifting gears takes time away from putting power down. Faster shifting transmissions and increased top speeds* have have made the trade off worth it in recent years/decades.

The reason we do not have thirty ratios in cars is that the gains are currently not worth the increased size, complexity, and cost. That might change at some point just as five and six speeds replaced three and four speeds (and eight/nine/ten speeds currently are.)

*necessitating an increased spread between highest and lowest ratios.

JohnH3ASP > jimz 01/21/2017 at 19:56

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Neat. Almost looks planetary. “Almost”...

JohnH3ASP > jimz 01/21/2017 at 19:58

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2 types of top speed: Rev-Limited (Not Enough Gears) or Aero-Limited (Not enough horsepower). So 18 gears and Koenigsegg’s engines will make something fast.

JohnH3ASP > jimz 01/21/2017 at 19:59

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I want to drive a semi.... really bad.

jimz > JohnH3ASP 01/21/2017 at 22:04

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nope, not contained within a ring gear. they’re still parallel gearsets. double-countershaft manual transmissions like in heavy trucks are strong, but parallel gearsets have an inherent weakness in that when torque is applied, the driving and driven gear are trying to push each other apart. the more torque you apply, the harder they push against each other. planetary gearsets are contained within the ring gear, and have nowhere to push each other away to. plus if you want to make them stronger you just add more planet gears.

jimz > JohnH3ASP 01/21/2017 at 22:05

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can you point me towards a car on the market which has it’s top speed limited by engine revs?

jimz > JohnH3ASP 01/21/2017 at 22:05

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trust me, it gets old.

Fast.

pip bip - choose Corrour > JohnH3ASP 01/22/2017 at 07:01

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make it so!

JohnH3ASP > pip bip - choose Corrour 01/22/2017 at 08:08

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I don’t have millions of dollars, and I don’t know a transmission perfectly well. Sorry lol. I know manuals are simple, though.

JohnH3ASP > jimz 01/22/2017 at 08:09

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Any car with a 3-speed?

Rock Bottom > JohnH3ASP 01/22/2017 at 12:58

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It’s terrifying for 20 minutes, then it’s fun for 20 minutes, then it’s just frustrating for the rest of eternity. You’re not missing much.

ateamfan42 > jimz 01/23/2017 at 08:53

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can you point me towards a car on the market which has it’s top speed limited by engine revs?

Not currently, on the market, but not that old either: 2004/2005 Mazdaspeed Miata. With the 6500 rpm redline and 4.10 final drive, the car is gear limited to about 129 mph, but has the power to be able to go faster.