# To transmit from 2 counter-rotating shafts into 1 perpendicular shaft?

• Al-Layth
In summary: This allows the input shafts to rotate in opposite directions, but the output shaft to rotate in the same direction as the input shafts. A differential is then used to combine the two input shafts' rotation onto the output shaft, resulting in a perpendicular output shaft. In summary, a car differential is used to combine the rotation of two input shafts onto a perpendicular output shaft. This is achieved by using bevel gears that allow for a fixed ratio of input shaft speeds and a reversing gear that allows the input shafts to rotate in opposite directions. The differential then combines the rotation of the input shafts onto the output shaft, resulting in a perpendicular output.

#### Al-Layth

TL;DR Summary
How do I transmit power from two shafts, rotating in the opposite directions at different speeds to one shaft perpendicular to both of them?

Well it's kind of what a car differential does. You'd have to reverse one of the two to get them rotating the same way, but if you can't figure out how to do that, you're in the wrong business.

Halc said:
Well it's kind of what a car differential does. You'd have to reverse one of the two to get them rotating the same way, but if you can't figure out how to do that, you're in the wrong business.
you mean make the two input shafts rotate in the same direction?
I can't do that, they absolutely have to rotate in the opposite direction heh

Al-Layth said:
you mean make the two input shafts rotate in the same direction?
I can't do that, they absolutely have to rotate in the opposite direction heh
You have a 'mystery transmission element' in the picture. You mean you're not allowed to put gears or other moving parts inside that? If you are, then what restriction is preventing you from doing so?

Al-Layth
Halc said:
You have a 'mystery transmission element' in the picture. You mean you're not allowed to put gears or other moving parts inside that? If you are, then what restriction is preventing you from doing so?
no
i can put anything in the mystery area

I'm afraid a mystery area containing a vacuum is probably not going to meet your needs.

Al-Layth
Al-Layth said:
How do I transmit power from two shafts, rotating in the opposite directions at different speeds to one shaft perpendicular to both of them?
Do the two input shafts have to be coaxial? If you can offset them a bit from each other perpendicular to their axes, that would make it simpler.

Al-Layth
berkeman said:
Do the two input shafts have to be coaxial? If you can offset them a bit from each other perpendicular to their axes, that would make it simpler.
yes i can move them anywhere but they have to remain horizontal

2) If you can put anything in there, put in a gear to reverse the rotation direction of one of them, and then put in a differential, just like the one on the old rear-wheel drive cars, and only a little different than the one on the front-wheel drive models. Both serve the same purpose, but only the former has one shaft perpendicular like that.

I know all about differentials, having built a couple out of toys, and having melted one in my Grand Marquis. It was a sight to behold

Lnewqban
Al-Layth said:
yes i can move them anywhere but they have to remain horizontal
Great. If you offset them you can use fairly simple gears in that transmission, IMO. Offset one shaft up and the other one down and use bevel gears or similar to couple the two input shafts to the output shaft. If the two input shafts need different gear ratios, use seperate bevel gears to do the coupling.

https://m.media-amazon.com/images/I/613n+C3ARML.jpg

Al-Layth
Actually, if the different gear ratios are the only issue, then you may be able to just offset one of the input shafts up the output shaft a bit to couple via a different set of bevel gears with a different ratio compared to the bevel gears at the end of the output shaft...

Al-Layth said:
i can put anything in the mystery area
Let us assume that the perpendicular output shaft speed must be the sum of the speeds of the two counter-rotating, independent, input shafts.

1. Three bevel gears.

2. One reversing gear and a differential.

3. Two hydraulic pumps, in parallel, driving one hydraulic motor.

4. Two DC voltage generators, in series, driving a DC motor.

5. Two shaft encoders, a microcontroller, and a servo or stepper motor to drive the output shaft.

Al-Layth
Baluncore said:
Let us assume that the perpendicular output shaft speed must be the sum of the speeds of the two counter-rotating, independent, input shafts.

1. Three bevel gears.

2. One reversing gear and a differential.

3. Two hydraulic pumps, in parallel, driving one hydraulic motor.

4. Two DC voltage generators, in series, driving a DC motor.

5. Two shaft encoders, a microcontroller, and a servo or stepper motor to drive the output shaft.
for 1.
How could 3 bevel gears work here?
if one is mounted on each of the shafts and the input shafts both interlock with the output shaft then won't the input shafts just subtract from each other?

(here's I have artistically illustrated how I imagine ur three bevel gear idea. ignore the gearboxes )

Baluncore said:
2. One reversing gear and a differential.
I swear Im not playing dumb

Whats a reversing gear ?

Al-Layth said:
How could 3 bevel gears work here?
It is the simplest, but limited solution. The bevel gears would need tooth counts that allowed for a fixed ratio of input shaft speeds.

Al-Layth said:
Whats a reversing gear ?
One pinion drives a second pinion on a parallel side shaft, called a counter-shaft, which must then counter-rotate.

If your two input shafts are coaxial, then the other shaft will also need to be offset by the same amount. That can be done using two slightly smaller pinions, coupled by an intermediate idler pinion of any convenient size.

You might consider using a pancake differential to combine the two axial shafts, followed by a right angle drive to the perpendicular output shaft.

Al-Layth said:
How could 3 bevel gears work here?
if one is mounted on each of the shafts and the input shafts both interlock with the output shaft then won't the input shafts just subtract from each other?
Since the input shafts are counter-rotating, the subtraction would become an addition.
The constraints on the speeds of the input shafts are unspecified.
Are they operating at a fixed speed ratio, or are the speeds quite independent.

## 1. How does the transmission process work?

The transmission process involves using gears or belts to transfer power from two counter-rotating shafts to one perpendicular shaft. The gears or belts are connected to the shafts and rotate at different speeds, allowing the power to be transferred from one shaft to the other.

## 2. What are the benefits of using counter-rotating shafts?

Using counter-rotating shafts allows for a more compact design and reduces the need for complex gear systems. It also increases the stability and balance of the system, making it more efficient and less prone to vibrations.

## 3. What factors determine the efficiency of the transmission?

The efficiency of the transmission depends on the type of gears or belts used, the angle of the shafts, and the speed and torque of the input and output shafts. Friction and mechanical losses also play a role in the overall efficiency.

## 4. Are there any limitations to using counter-rotating shafts?

One limitation of using counter-rotating shafts is the potential for increased noise and vibration. This can be mitigated by using high-quality gears or belts and ensuring proper alignment and balance of the shafts.

## 5. What are some common applications of this type of transmission?

This type of transmission is commonly used in vehicles, such as cars and motorcycles, to transfer power from the engine to the wheels. It is also used in industrial machinery and equipment, such as pumps and generators, to transfer power from a motor to a rotating component.

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