# Ratchet based automatic transmission

• Automotive
Would this work?

To explain simply, shaft 1 has three different sized gears on it drawn red. Also red but on shaft 2 exists another set of gears. But they are not connected to shaft 2, they spin freely and independent from each other. They are connected to the gears on shaft 1. There by we have three different gear ratios. Now the blue crosses symbolise ratchets gears. The three gears on shaft 2 are connected to shaft 2 via ratchet gears. This means the gears can spin shaft 2, but not get spun by it.

The idea here is that because of the different gear ratios, the gears on shaft 2 will all have different speeds. This means the smaller gear of the three, will spin the fastest. As it spins shaft 2 faster then the other gears, they will not get spun by shaft 2, because of the ratchet gears. If torque of the small gear is insuficient and it can not spin shaft 2, the next bigger gear starts spinning shaft 2 and so on.

What do you think?

What do you think?
There must be friction clutches somewhere that will slip at a specified gear-change torque. That will generate heat in the gearbox oil, which will consume power, and degrade the oil.

Baluncore said:
There must be friction clutches somewhere that will slip at a specified gear-change torque. That will generate heat in the gearbox oil, which will consume power, and degrade the oil.
The slips happens because, when the torque of the small gear is insuficient. Shaft 2 stops spinning, meaning its slow enough for the middle gear to get a grip on it via the ratchet gear. No friction involved.

If torque of the small gear is insuficient
Why would the torque be insufficient? Why would the torque change at all?
and it can not spin shaft 2,
Once the ratchet mechanism is locked, how would it unlock? How do you make sure no two gear sets are locked at the same time?

Which is the input shaft?
Which is the output shaft?

This looks like a manual gearbox, shaft 2 is the main shaft, while shaft 1 is the lay shaft or countershaft. One end of shaft 2 would be the input, the other end would be the output. When no gear pair was driven, direct drive would go straight through shaft 2.

Should have made myself more clear.
jack action said:
Why would the torque be insufficient? Why would the torque change at all?
Basically shaft 2 is the output shaft. When the load is too big (for example a ramp), the small gear on shaft 2 ( so the fast one ) has insuficient torque.

jack action said:
Once the ratchet mechanism is locked, how would it unlock? How do you make sure no two gear sets are locked at the same time?
That was one of the main problems I encountered, thats why im here for some opinion and help. The idea was that the gears one shaft 2 are connected to shaft 2 via the ratchet mechanism. That means first of all, that the gears can act as input to shaft 2 but not the other way around. As each gear on shaft 2 has different speeds, the fastest gear would lock in, and that means the speed of shaft 2 would gain the speed of the fastest gear. As shaft 2 spins faster then the other middle and big gears, they never have a chance to lock in, unless the fast (small) gear would stop due to insuficient torque, decreasing the speed of shaft 2, giving the other gears a chance to lock in.

The problem i was talking about, was that although each gear on shaft 2 is independent from each other they are all connected to the gears of shaft 1. The gears on shaft 1 are directly conncted to shaft 1 meaning they all have the same speed. Shaft 1 is the input shaft of the engine. If lets say the small gear on shaft 2 stops spinning due to insuficient torque, then that would in turn stop shaft 1 to spin and the rest of the gears of shaft 1. They would not be able to spin any of the gears on shaft 2.

One way i could solve that, would be by adding a another ratchet mechanism to shaft 1 and its gears. This ratchet mechanism though, would be held by springs, so if the big gear on shaft 1 stops spinning, shaft 1 could just slide past the gears as it pushes the spring held ratchets away.
But i wanted to have a system without any of the friction.

Another solution, would be to replace shaft 1 and its gears with two differentials. The input is connected to the carrier of one differential, while on output of that differential goes to one gear of shaft 2 and the other output goes to the input of the next differential. You could add fourth gear to shaft 2.
Problem here is that it adds to the complexity, the whole ratchet mechanism becomes obsolete anyway.

What would you say?

Baluncore said:
Which is the input shaft?
Which is the output shaft?

This looks like a manual gearbox, shaft 2 is the main shaft, while shaft 1 is the lay shaft or countershaft. One end of shaft 2 would be the input, the other end would be the output. When no gear pair was driven, direct drive would go straight through shaft 2.
I‘d recommend to read my answer to jack. Basically shaft 1 is connected to the input while shaft 2 is connected to the output.

So, each gear on shaft 2 is free spinning until you hit the magical speed where it takes the load and the ratchet locks in?

I would say you’re borderline developing a solution in search of a problem.

No offense, but if this idea was practical and reliable, it would probably already be on the market. The ratcheting mechanism introduces too many moving parts and too many failure points to be worth the trouble. There’s no way to offload the prior gears’ ratchet, either.

A operator-controlled clutch on the input shaft to shaft 1 and an idler gear that you can slide along a shaft between 1 and 2 to select the gears engaged is probably the easiest solution.

This isn't anything particularly new. Using a sprag clutch in gear trains accomplishes part of what you are doing. Usually it saves one clutch pack. The lowest gear will have the sprag. So if no other clutches are engaged the sprag clutch catches and drives the output shaft. If the output shaft is spun faster by engaging a clutch to drive a different gear the sprag over runs with no harm done. However, you describe slipping of clutches when the torque gets too high. That is unacceptable.

unless the fast (small) gear would stop
How would it stop? It is still connected to the input shaft 1. It can only stop if shaft 1 stops as well, and thus the other gears are also stopped.

I understand that a slower shaft 2 speed will permit the middle gear to engage, but how will slowing shaft 2 disconnect the smallest gear?

Normally, shaft 2 speed would be initially zero and you would want the largest gear to be engaged and the other two disengage. How are the other two disengaged in your gearbox at a very low speed for shaft 2?

To me, a ratchet mechanism looks something like this (although the locking mechanism would be in reverse in your case as the gear is the input):

What do you think?
You have my sympathy. I remember, the occasion over 50 years ago, the first time someone tried to explain the operation of a differential gear to me, unsuccessfully. It took persistence on my part, and time to think about it.

Before you start inventing new gearboxes, I think you should study how a traditional manual gearbox, with a clutch and a countershaft operates. https://en.wikipedia.org/wiki/Manual_transmission

Then look at the more recent dual clutch, dual countershaft, automatic gearbox configurations.
https://en.wikipedia.org/wiki/Dual-clutch_transmission

When you get stuck, break the system down into smaller components. Study those, and play with them, until you understand the concepts without thinking.

As you need help, ask more questions here.

Baluncore said:
There must be friction clutches somewhere
Or, as is most manual constant mesh gearboxes, dog clutches to engage just one of the free gears on the output shaft (at a time). The other two gears rotate freely. The dogs are moved by the gear stick. A disconnecting clutch is needed to allow a gear change and there are additional 'synchromesh' rings to bring gears to the appropriate speed so the dog will engage without 'graunching'.
Flyboy said:
So, each gear on shaft 2 is free spinning until you hit the magical speed where it takes the load and the ratchet locks in?
I had an arrangement like this on a 49cc moped which started off in a very low gear 1 and then shiften up to the running gear 2. It would only re-engage gear 1 when the bike was stationary. Thius it didn't need a change down facility.

But, as mentioned higher up, why try to re-invent a system until you have full knowledge of existing systems.

Flyboy
jack action said:
How would it stop? It is still connected to the input shaft 1. It can only stop if shaft 1 stops as well, and thus the other gears are also stopped.
You are right I discussed this problem in the same answer below.

Baluncore said:
You have my sympathy. I remember, the occasion over 50 years ago, the first time someone tried to explain the operation of a differential gear to me, unsuccessfully. It took persistence on my part, and time to think about it.

Before you start inventing new gearboxes, I think you should study how a traditional manual gearbox, with a clutch and a countershaft operates. https://en.wikipedia.org/wiki/Manual_transmission

Then look at the more recent dual clutch, dual countershaft, automatic gearbox configurations.
https://en.wikipedia.org/wiki/Dual-clutch_transmission

When you get stuck, break the system down into smaller components. Study those, and play with them, until you understand the concepts without thinking.

As you need help, ask more questions here.
I‘ve already informed myself on these systems. Thanks a lot for your consideration and help!

A mentor on this forum already asked me to clear up what I mean by auto. I should have made clear that by auto I mean automatic. Sorry for the confusion.

If torque of the small gear is insufficient and it can not spin shaft 2, the next bigger gear starts spinning shaft 2 and so on.
What begins to slip when the torque becomes too high for the smaller gear on shaft 2 ?

Baluncore said:
What begins to slip when the torque becomes too high for the smaller gear on shaft 2 ?
That was the big thinking mistake. Its directly connected to shaft 1. So it wouldn‘t work.

You would have to build some kind of friction mechanism too, which would make the whole purpose obsolete.

The only way to do it without friction, would be to replace shaft 1 with a few differential gears. (Already exists)

Baluncore

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