h a l f b a k e r yRenovating the wheel
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Not sure if this has ever been done or suggested, but I think some of the problems associated with continuous transmissions could be avoided by having lots of discrete gear ratios. My suggestion is to have the engine output go through a series of five reduction steps. Each one would either be engaged,
or not (transmision 1:1) by a system of clutches. The ratios would be set up such that each combination of reduction steps would produce a different gear ratio. This would give 32 gear ratios. I haven't actually worked out what the ratios would have to be, or for that matter if it is possible to create evenly spaced ratios in this way.. but this is "half"bakery after all.
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Gearing is multiplicative rather than additive, so the ratios would not be evenly spaced. |
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Nice title. Really descriptive. |
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Without even getting into the idea itself, I have two issues with this idea
1) You haven't invented binary numbers, so the name is pointless and useless.
2) The 'this is only "half"bakery argument' annoys me when put in a context of 'so I don't have to put thought into whether or not it could actually work'. I consider something half-baked if the poster hasn't thought about a market for it, superiority to competing products, cost to make vs sale price, whether it actually makes sense as a new invention or a number of other things, not if they haven't thought about possibility of creation. (In fact, I don't even mind it that much, I just dislike using the name to justify not putting effort into the idea) |
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what are the problems with continuous transmission you are trying to overcome? wouldn't you lose power (and response) at each of the five steps (through friction)? |
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I can't seem to find the article where I read it, sorry, but the limitations I was referring to had to do with apparent design limitations limiting the force that could be transmitted. Apparently a number of vehicles had higher horsepower versions released only on more traditional transmission designs because the continuous versions would not hold up to the higher stress while still retaining the level of reliability that would be expected. |
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I am aware that the spacing of the steps would have to be non linear to achieve 32 steps, I will attempt to work out some numbers and possibly repost with a much better title. Feel free to mfd if you feel it necessary. |
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Since it's better to have gear ratios in a geometric rather than logarithmic sequence, the fact that gearing is multiplicative rather than additive would be useful. |
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The bigger problem is that each set of gears through which power is transmitted will have a certain amount of friction. Cascaded transmissions would thus tend to waste power. |
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Transmissions could be constructed to eliminate friction on the stages that were set for a 1:1 ratio. If that were done, it might be reasonable to have a set of three transmissions for forward gears, plus a reversing gear. A more interesting approach might be to construct a transmission with three sets of gears to connect the crank shaft to the lay shaft, and three sets of gears (two forward; one reverse) to connect the lay shaft to the drive shaft. That would allow six forward speeds and three reverse (though normally one would only use the lowest reverse speed). |
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I want to know if an engine is possible with sufficient flexibility to render the gearbox completely unnecessary. I'm aware that this would need to be a very clever system indeed (variable valve timing, compression ratios, maybe inlet geometry, the works) but my question is whether it would ever be a viable concept? |
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Using an internal combustion engine, there is no way to avoid using a transmission in a vehicle that is capable of both high-speed travel and idling while stopped. If a vehicle will only travel at low speeds (was with some walk-behind mowers), a clutch may suffice but trying to use a high-speed vehicle in one gear would cause excessive wear (note: a manual-transmission Mercury Tracer can get up to about 45mph in first gear, but such operation is decidedly not recommended except when necessary to avoid a collision). |
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Using an internal combustion engine to produce too much torque at low speeds will cause excessive wear. When operating at higher speeds, the piston will have already started moving downward by the time most of the gasoline in it has ignited. And when used with a constricted throttle, there's not a whole lot of fuel in the cylinder so it doesn't matter much if the piston isn't moving downward before it burns. The problem is that if the piston hasn't moved down enough before a lot of the fuel has burned, not only will the peak pressures be higher than they should be, but those higher pressures will cause the remaining fuel to burn even faster than it otherwise would. |
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Incidentally, purely-electric transmissions have been used in diesel locomotives for a very long time. They are generally not used in cars, however, because they weigh more than mechanical transmissions of similar capacity. In a car, weight is bad. By contrast, in a railway locomotive, weight is good. |
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"Using an internal combustion engine, there is no way to avoid using a transmission in a vehicle that is capable of both high-speed travel and idling while stopped." |
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Actually, not true. The Boss Hoss motorcycle, powered by a 350 cubic inch Corvette V8 engine (or optional 502 ci engine) originally had only a (heavy-duty truck) clutch, not a transmission in the conventional sense (current production Boss Hoss models have a 2-speed transmission). The large V8 produces enough torque at idle to accelerate the vehicle from rest (I believe idle engine speed moves the vehicle at about 10 mph, starting from rest requires a good bit of clutch slippage- throttle is not applied until vehicle is rolling). |
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If the engine produces enough torque at idle to move the vehicle, a transmission isn't needed. |
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For a passenger sedan this would require about a 1,000 cubic inch engine (about 16,000 cc?) or larger. Impractical, yes, but possible. Something similar to Jay Leno's "Tank Car?" |
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How about a transmission with only 2 gears? One of them cone shaped, becoming steadyly wider, with an extra tooth added whenever necessary to continue to mesh with the other gear. |
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//with an extra tooth added whenever necessary to continue to mesh with the other gear// |
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Now THAT's a halfbaked idea... Do you know what two meshing gears look like? Do you know what helical gearing is? Do you know anything about the tolerances and alignment required to have a gear mesh survive more than a couple thousand revolutions without coming apart? Hold that thought. Now think about your cone gear. Think about what it should look like to work. Having trouble bringing the two ideas together? Congratulations. |
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