Is a Toroidal Engine a More Powerful Alternative to Reciprocating Engines?

[Kenneth Mann]

Does anyone know of any gearing assemply like what I am looking for - - - sort of the opposite of a Geneva Mechanism. It would have a drive that, during the first four 90 degree increments of the input, the output also increments in 90 degree intervals. In the fifth and sixth 90 degree increments (540 degrees total) of the input, the output is held stationary. In essence, 360 degrees out for every 540 degrees in).

An alternative would be for 180 degrees out for every 270 degrees in. Thanks.

KM

 

[Bob S]

What level of power (watts or HP) are you talking about and what RPM? You maybe could use a microprocessor and a stepping motor.

 

[Kenneth Mann]

What level of power (watts or HP) are you talking about and what RPM? You maybe could use a microprocessor and a stepping motor.

Looking for relatively large power handling capacity. It should be mechanical, and hopefully relatively efficient. To be sure, it's a mind experiment prompted by one of your other links - - - on torodal engines.

KM

 

[Danger]

I'll have to think on this for a while, since I'm well into the Scotch right now (my wife drank all of my beer). It seems to me, offhand, that it could be achieved with either a cam or an interrupted gear.
You mentioned that the output is to be held during the non-driven phase. Do you mean just not driven, or do you have to somehow lock it into position?

 

[Kenneth Mann]

I'll have to think on this for a while, since I'm well into the Scotch right now (my wife drank all of my beer). It seems to me, offhand, that it could be achieved with either a cam or an interrupted gear.
You mentioned that the output is to be held during the non-driven phase. Do you mean just not driven, or do you have to somehow lock it into position?

It needs to be locked. It can't float free.

KM

 

[Danger]

Is there power and space available to put an electromagnetic brake on the shaft?

 

[famousken]

Maybe you could use some sort of worm gear? perhaps from a windshield wiper motor or something. pulse the motor on and off with a microcontroller for stop/start times and the worm gear assembly will keep the output shaft from loosing it's position.

 

[Kenneth Mann]

Is there power and space available to put an electromagnetic brake on the shaft?

The answer is probably yes, but I think a mechanical solution would be better.

KM

 

[Kenneth Mann]

Maybe you could use some sort of worm gear? perhaps from a windshield wiper motor or something. pulse the motor on and off with a microcontroller for stop/start times and the worm gear assembly will keep the output shaft from loosing it's position.

I don't think so. It should be an integral part of the mechanism itself.

KM

 

[Kenneth Mann]

I'm going to try to put up a description of the concept itself. It was suggested by another string - - - a toroidal engine ides. It's just an idea exercise.

KM

 

[Kenneth Mann]

I'm going to try to put up a description of the concept itself. It was suggested by another string - - - a toroidal engine ides. It's just an idea exercise.

KM

 

[Danger]

Hmmm... I thought that the worm gear was a damned good idea, but if you don't want to pulse the motor...
Maybe a combination of an interrupted gear and a cam? When the non-toothed section of the gear gets to the driven gear, the cam applies a mechanical braking force to the driven shaft. If they're on the same driveshaft, they should remain synchronized.

edit: You could also use an interrupted gear to drive a worm gear. That might be the best of both worlds.

 

[Kenneth Mann]

Hmmm... I thought that the worm gear was a damned good idea, but if you don't want to pulse the motor...
Maybe a combination of an interrupted gear and a cam? When the non-toothed section of the gear gets to the driven gear, the cam applies a mechanical braking force to the driven shaft. If they're on the same driveshaft, they should remain synchronized.

edit: You could also use an interrupted gear to drive a worm gear. That might be the best of both worlds.

Actually, the gear/cam arrangement sounds pretty good to me. It would appear to have a faster response than a worm drive. Also the action appears more bi-directional. I'll try to supply some sketches of the envisioned toroidal system's operation soon. That might give an idea of what is needed.

KM

 

[Danger]

I'll try to supply some sketches of the envisioned toroidal system's operation soon. That might give an idea of what is needed.

KM

That would be very helpful. It's a bit difficult to give design advice without knowing the intended goal.

 

[Kenneth Mann]

That would be very helpful. It's a bit difficult to give design advice without knowing the intended goal.

I have the drawings, but need to convert them. I should have them by tomorrow.

KM

 

[Danger]

It just occurred to me (duh...) that the interrupted gear and the cam can actually be the same piece, rather than two separate ones on the same shaft. Don't know why the hell I didn't think of that the first time around. (Oh, yeah... Scotch...)

 

[famousken]

Mmmm...Scotch

 

[Kenneth Mann]

The engine shown in the accompanying drawings can be either Otto Cycle or Diesel cycle, and is equivalent to an eight-cylinder reciprocating engine since a cycle takes only one revolution. Only one chamber (volume between pistons) will be described, although there are four. A full four cycle operation takes place in each chamber with each revolution. Pistons can only move in a forward direction (clockwise), though each will be intermittently stopped. The following ten steps are taken to describe one full cycle: (Refer to plates 1 through 4.)

A. In the first phase, for the chamber we are examining, at the start the pistons are together. Both pistons are in motion, but the trailing one is stopped here.

B. (Intake Phase) The lead piston (yellow) is moving and the trailing piston (rose) is stopped.

C. Continuation of intake. Here, the piston ahead of the chamber (yellow) continues moving, and the piston that it has just overtaken (rose) is just starting. Here, the chamber is filled.

D. Here, all pistons move together, until they reach the point shown, and the piston ahead of the intaken air (yellow) stops.

E. (Compression Phase) Here, the piston following the intaken air (rose) continues, compressing the charge.

F. At this point, the compression phase is complete, and the piston ahead of the charge (yellow) starts to move again. The two pistons are now moving together.

G. (Ignition Phase) The two pistons continue until they reach the spark plug/injector. Here, the piston that is now trailing (rose) stops and the plug fires or the newly injected fuel pressure ignites.

H. (Expansion Phase) Only the lead piston (yellow) is here allowed to move. The expanding gas forces it ahead.

J. Expansion continues until the lead piston (yellow) reaches the one ahead of it (rose) which then starts to move, along with the piston behind the expansion chamber (also rose).

K. (Exhaust Phase Start) All the pistons move until the exhaust port is uncovered and exhaust starts. Then the piston (yellow) ahead of the chamber under discussion stops, while the following piston (rose) continues, forcing the gasses out.

L. The exhaust purge continues.

M. When exhaust has ended, the lead piston (yellow) and the trailing piston (rose) are together, and the lead piston again starts moving, while the trailing piston continues moving.

N. Both pistons continue moving until the starting position is again reached. Here the trailing piston (rose) stops, and the cycle starts again.

P. This is simply a typical view showing operation in all chambers at one point in time.

This is the application which I described as needing the "gearing assembly", to cause the pistons to start and stop when needed. Obviously the gearing has to be robust, because this is a power device, and it has to be fast acting. This is why I think a mechanical linkage is preferable. It should also have inherent feedback (bi-directional action) since it will go to drive the pistons, be driven by the pistons and ultimately drive the output. Finally, I feel that I must tell what I plan for this engine in this configuration. The answer - - - absolutely nothing! It is a thought exercise only, open to anyone interested. I think, however, that this approach is superior to any that we have seen, so far. Caveat: This configuration has the same drawbacks as all toroidal engines: 1) Because it is sealed, it cannot keep lubricating oil from mixing with the working fluids, and 2) It will be tricky to seal at its base (but easier than the Wankel), which makes it problematic for consumer automobiles (pollution??). On the other hand, it is probably quite suitable for racing vehicles, helicopters, speedboats and items like that.

(The last two figures are in the following insertion)

KM

 

[Kenneth Mann]

"The figures that were omitted."

 

[Kenneth Mann]

What I envision is a gearing something like the following:

 

[Danger]

That is an intriguing design. The only potential problem that I can foresee is a vibration issue arising from the starting and stopping of the pistons.
When I first started responding in this thread, I had no idea of what you had in mind. For some reason, I was thinking of a smaller electrically driven thing. I'm going to have to study the diagrams for a while; it's a lot more complicated than I had envisioned.

 

[famousken]

Hmm, do you think some kind of connecting rod between two shafts would work? I don't think the broken gear Idea would last very long, plus it won't lock the shaft while the rotor (piston) is supposed to be stopped. I know in a normal reciprocating engine, the pistons dwell a little while at TDC and BDC during every revolution of the crankshaft. What I am envisioning is using a crankshaft and connecting rod that go to your rotor assembly, timing would be set by rotating the housing in relation to the crank centerline. As far as vibration goes, I am not quite convinced that it is going to be a problem because it seems that as one rotor is stopping, the other is beginning to move in the same direction, so I am seeing a sort of balancing operation.

 

[Danger]

I didn't express my thoughts very well in my last post. What I meant by 'vibration' is that there will be a severe shock load when a piston locks up. That has the potential to not only shatter gear teeth, but also rip out motor mounts.

 

[Kenneth Mann]

I didn't express my thoughts very well in my last post. What I meant by 'vibration' is that there will be a severe shock load when a piston locks up. That has the potential to not only shatter gear teeth, but also rip out motor mounts.

That's what I'd like to find a way for. The problem is not in the pistons but in the gearing that links them in the illustrated example, so there is hopefully a way to implement this function without an open-tooth gear. After all- pistons stop on reciprocating engines. In this case one piston is always free to move, so there's no undue strain - - - I just don't know the best way to link them.

KM

 

[Danger]

That's what I'd like to find a way for. The problem is not in the pistons but in the gearing that links them in the illustrated example, so there is hopefully a way to implement this function without an open-tooth gear. After all- pistons stop on reciprocating engines. In this case one piston is always free to move, so there's no undue strain - - - I just don't know the best way to link them.

KM

While a reciprocal engine piston technically stops at the top and bottom of its cycle, remember that it's only for a millisecond at most, and the return stroke is not mechanically interrupted. The crankshaft, flywheel, and harmonic balancer ensure that things keep moving in the same direction due to conservation of angular momentum.

edit: You've got me hooked on this bloody idea, but I'm having a hard time seeing how to make it a reality.

 

[Kenneth Mann]

edit: You've got me hooked on this bloody idea, but I'm having a hard time seeing how to make it a reality.

Basically, this whole idea is just a toy to play with.

You are, of course, right about the problem with the instantaneous accelerations of the pistons and their gears. The torque on any such mechanism is defined by its angular acceleration, and for the gears, as shown, that would be approaching infinite - - - not a good thing!

It might be noted that the instantaneous acceleration is not necessary - - - it's just that the alternative can be really tricky. If a decent way of decelerating and accelerating the pistons could be devised it would be acceptable with just a little loss of volumetric efficiency. I might also point out that that is essentially what is done in a patent application in India, using elliptical gearing between the pistons (I'll try to find it's reference). The problems I see with this approach are: 1) In deriving the output drive the two piston gear speeds are constantly varying. It might be that they will additively balance out, and can be put through a differential unit, but I have no proof of that. 2) Elliptical gears, unless cut extremely accurately, tend to want to bind.

The ideal would probably be to find a way to have one accelerating while the other is driving the output - - - but how then would you switch back and forth. This is a tricky one.

I'll probably continue to diddle with it intermittently from now on.

KM

 

[Danger]

I'll keep thinking on it. Maybe some sort of hydraulic braking system for the pistons...?

By the bye, did you receive my 'friends' request? You don't show up on my friends list. I totally understand if you received and rejected it, since we don't know each other very well. (I usually reject requests, with an explanation, from people that I haven't dealt with a lot.) I just never received notification either way.

 

[RonL]

Basically, this whole idea is just a toy to play with.

You are, of course, right about the problem with the instantaneous accelerations of the pistons and their gears. The torque on any such mechanism is defined by its angular acceleration, and for the gears, as shown, that would be approaching infinite - - - not a good thing!

It might be noted that the instantaneous acceleration is not necessary - - - it's just that the alternative can be really tricky. If a decent way of decelerating and accelerating the pistons could be devised it would be acceptable with just a little loss of volumetric efficiency. I might also point out that that is essentially what is done in a patent application in India, using elliptical gearing between the pistons (I'll try to find it's reference). The problems I see with this approach are: 1) In deriving the output drive the two piston gear speeds are constantly varying. It might be that they will additively balance out, and can be put through a differential unit, but I have no proof of that. 2) Elliptical gears, unless cut extremely accurately, tend to want to bind.

The ideal would probably be to find a way to have one accelerating while the other is driving the output - - - but how then would you switch back and forth. This is a tricky one.

I'll probably continue to diddle with it intermittently from now on.

KM

It might be worth considering to make the pistons rectangles, they would have linear clutch bearings to ensure a forward action, with no recoil at all. The pistons would attach to the end plates, yellow on one side and rose on the other. Cam and locks would work with the two end plates. The entire assembly could rotate between pillow bearings.

Any locking devices would be controlled with pressure and cam action, much like the action of hydraulic lifters on a typical engine.

Just diddling with the thoughts.

Ron

 

[Kenneth Mann]

I'll keep thinking on it. Maybe some sort of hydraulic braking system for the pistons...?

By the bye, did you receive my 'friends' request? You don't show up on my friends list. I totally understand if you received and rejected it, since we don't know each other very well. (I usually reject requests, with an explanation, from people that I haven't dealt with a lot.) I just never received notification either way.

I don't think that I received it, but then I don't really know how the function operates. BTW, your inbox is full. You need to move some of the stuff out.

KM

 

[Kenneth Mann]

Shown in the first attachment is a series of charts to illustrate three approaches.

1) The upper section of the attached chart depicts the operation of the system from the previously referenced Indian patent (I still haven’t found it). "A" depicts the angular velocity of one piston assembly (from maximum to minimum RPM) and "B" depicts the other. These are apparently interconnected via an elliptical gear assembly.

The question regarding this configuration is "How is the output derived?" The obvious approach would be to simply sum the "A" and "B" outputs. It is not apparent, however, that this can be done. What is the relationship between the two piston velocities? To sum them (via a differential) that relationship would have to be linear. It is apparently elliptical.

2) The second section shows the relationship given in the series of piston motion views described in previous insertions. The advantage of this approach is in its simplicity. The two piston sets are simply tied together via a central gear, with a section of teeth removed - - - with each piston alternately held stationary when its gear encounters this section.

The problem with this approach is the extreme torque placed on each piston gear set as it accelerates and decelerates. (This is shown at the positions marked "X" in the drawing.

3) The third section shows the piston sets connected via a differential gear set. Each set, at selected positions, is retarded (and possibly also accelerated). This leads to the pistons being driven apart and together at the needed points. In this case, the accelerations and decelerations are linear rather than stepwise, and thus do not put undue strain on the pistons and their gears. Each piston (and the output) has a "Retarder/Accelerator" which controls the operations of the associated piston. (The one at the differential output is used simply to provide smooth output.) Each "Retarder/Accelerator" has a position/velocity sensor, which sends the information to the Phase Locked Loop (PLL) controller where the control signals are generated and sent back to the "Retarder/Accelerators". These controls can be either frictional (mechanical)(retard only), or hydraulic, or electrical (motor/generator).

This approach also has possible drawbacks. The most apparent is potential complexity (the three retarders). RPM limits may also be a consideration - - - this would take experiment to determine. Also, special design caution must be taken to prevent piston collision.

Still the preferred approach would be to find some sort of "simple" mechanical linkage (equivalent to the "pedal" arrangement of the 1955 Bradshaw Omega engine design.

The second figure below illustrates a possible cross section for the third alternative.


KM

 

[Kenneth Mann]

The main attraction of the toroidal engine is its power density which is a lot greater than that of the conventional reciprocating engine. As example, an engine of the size (to scale) of that illustrated in my previous insertion would have a displacement of approximately 118 cubic inches (1.9 liter). At any given RPM, its equivalent displacement would equal that of a reciprocating engine of twice the displacement (236 cubic in./3.8 l). An increase of toroid "tube" diameter to 4 inches and of the torus center to center of the tube also to 4 inches yields a displacement of approximately 280 cubic inches (4.6 l), (equivalent to 560 cubic inches or 9.2 l). This would be approximately 12 inches in diameter.

KM