make vehicles with really immense gearing ranges. When I ride my bike, I can go slowly, sometimes very slowly up, almost any hill, and quickly, sometimes very quickly, the other way?
Or maybe they do and I just don’t know about it.
I’d get a boat if my car had such a transmission.
Because it’s not necessary? Your engine doesn’t feel pity, remorse, or fear. And it will not stop. The answer is the same reason they don’t make motorcycles with really immense gear ranges. Bicycles are designed to be powered by hyoo-mans.
Why would you buy a boat? Are you talking about what we referred to in less politically correct times as a “canoe”?
They do. The cars with CVTs have an infinite gearing. The Toyota Lexus LS has an 8-speed transmission!
Or, are you talking about a granny gear up to overdrive? Most cars, even with tow packages, don’t generally benefit from a granny gear. You can get a similar effect with a true 4WD that has a transfer case with a low gear and high gear. The low gear in first gear works like a crawler gear, even more effective that the old ‘granny gear’ trucks. But, it does nothing for fuel economy.
Heavy duty machinery has such gears. Why would you want such gearing in a passenger car? A 150-hp engine can tackle any reasonable slope, fast or slow, without the muscle fatigue that cyclists must contend with.
We dont need them. With 6 speeds and an accelerator we already do that.
I think you could take a rear wheel drive car and one close ratio four speed transmission and one wide ratio 4 speed transmission. Mount them so that the output shaft of the first transmission goes into the input transmission of the second transmission. This will give you 17 forward speeds and 8 reverse speeds. The shifter for the second transmission will be in the back seat, but it will give the back seat driver something to do.
There are cars with continuously variable transmissions, as another poster has said. The trend these days on ‘normal’ automatics is ever-increasing numbers of gears. There are cars being produced with 8-speed automatics. IMHO there is not much point for more than 6 speeds on a transmission in a passenger car. Many semi trucks have 15 or more gears, for exactly the reason your bike does.
A car engine obviously has a lot more power than a human, so 10 speeds or more is not necessary to keep the output of the ‘engine’ in its powerband for maximum efficiency with a ‘normal’ load of passengers. But even a car engine with hundreds of horsepower runs out of grunt eventually, no matter how many gears there are.
There’s no substitute for horsepower. If your car had 50 gears, you could certainly pull a boat up a mountain, but you’d still have to do it very slowly unless you got a horsepower upgrade.
Are you looking for more gears or a wider range to the overall gear ratio?
The more gears you put in a car transmission, the less efficient the transmission becomes because of the parasitic drag of all the unused gears squeezing gear lube out from between their their teeth as they still turn even though they aren’t being used to transmit power. You get to a point where the extra friction losses offset any benefit realized by the increased number of ratios.
I had a “12 speed” bicycle and having time on my hands, I counted all the teeth on the spockets and made a chart of its gear ratios. I found that I only had about 8 usable gear ratios because several of the gear combinations were duplications or near duplications of other gear combinations so don’t assume that your “27 speed” actually has 27 usable gear ratios.
I have found that I can achieve the highest average speed by standing on the pedals giving it everything I got whenever I am going up hill and letting gravity do the work while letting my muscles recover while going downhill. Pedaling downhill is mostly a waste of energy, you’re better off letting your muscles recover so you can tackle the next uphill with everything you have.
Hee, hee, good one.
Many years ago, I was a class A bicyclist. Those days are long gone, of course. But, when, for example, I rode a Century ride (100 miles in one day) or on a week long ride across state, those “near duplications” at times were an important change.
We had the tough guys, the guys who would do 100 miles in 4:25, we called them stallions, and they had the power to handle fewer gear changes. But, for most of us guys, we found a small change in gearing made a big difference on a long haul. For example, a slight upgrade lasting a mile or more, with a head wind, that difference was very beneficial.
On a more serious note, I do remember an aftermarket option for 1946-48 Fords was a Columbia two speed rear axle. This gave the car 6 forward speeds. I think a person selected the axle speed depending upon whether acceleration performance or economy was desired.
B.L.E. I don’t know anything about transmissions so para. #1 was interesting to me.
Paras 2 & 3 are basically common knowledge, with the exception that pedaling downhill is not a waste of energy because being aerobic exercise it burns off excess lactic acid more quickly than just coasting. Yes, muscles can use lactic acid as fuel.
with the exception that pedaling downhill is not a waste of energy because being aerobic exercise it burns off excess lactic acid more quickly than just coasting. Yes, muscles can use lactic acid as fuel.
Hmm, I never considered the possibility that exercising muscles might recover from anaerobic exertion faster than resting muscles. I’ll have to modify my riding somewhat and see what happens.
I was riding on New Mexico 518 from mile 52 (Sipapu ski resort) to mile 43 and back, uphill the whole way out and downhill the whole way back last summer. On that ride I did pedal downhill just to keep warm. Those early morning temps were in the 50’s even in the middle of August.
http://www.caranddriver.com/features/09q4/how_to_shift_a_semi-feature
they do.
They don’t do it on cars because it’s not necessary. A 4-6 speed transmission allows the car to go anywhere from 0 to somewhere north of 100mph. Unless you’re using it on a race track, you don’t need to exceed those parameters. If you are using it on a race track, and you need to go faster than the car was originally meant to go, you’re probably not using the stock transmission.
Most all racing sactioning bodys have rules on how many gears a transmission may or must have. More is not always better. Every gear shift is a short power interruption and even if that power interruption is only .1 second, it adds up if you are going through 6 or 7 shifts after every turn.
Just as bicycle races are won or lost on the uphills, car races are won and lost in the turns, where the cars are going their slowest. Maximum acceleration without spinning the wheels is tricky enough without having to go through a bunch of gear shifts while you are driving out of a turn.
Trying this again because my previous response to you has mysteriously disappeared.
There’s a good book that lays out the science behind this, Covert Bailey’s Smart Exercise:
It’s basically the science behind interval training, with which you are no doubt familiar.
You might also want to google Clarence Bass or Tabata Protocol.
Bike peddling works comfortably with good power over only a narrow range of RPMs: about 60-90RPM.
Low speed torque is there, like an electric motor, but power climbs with speed.
So a wide range of closely spaced gears allow the rider to stay in the “sweet spot”.
A gasoline or diesel engine however works strongly and efficiently over typically about a 3 to 1 range of speed (say 1500-4500 or 2000-6000RPM).
So there can be fewer gears and more widely spaced.
The Model T Ford chugged along with only 2 forward speeds. Other manufacturers adopted a transmission with three forward speeds and the Model A had a three speed transmission. Sometime in the 1930s, Borg-Warner introduced its overdrive which added a higher gear above the 3rd speed direct drive and this became an option on some cars. In fact, on the WIllys Jeep Station Wagon which came on the market in 1946 had this overdrive as standard equipment to reduce the rpms on the highway.
On my stick shift cars with the three speed transmission from the late 1940s through the 1960s, I would often start in first and shift directly to high when on level ground. The range of rpms in the engines allowed this.
Cyclists have a very limited range (pedaling RPM) at which they’re efficient, so more gears are needed to compensate. There is also a great deal of overlap on bicycle gearing to prevent “cross chaining”. Cross chaining is a condition wherein the small chainring is driving the small cassette ot vice-versa. This creates excessive lateral strain on the chain, adding drag for the cyclist and excessive wear to the chain, the chainrings, and the cassette.
Car engines, on the other hand, have a wide enough efficient range to be able to go well past the legal speed limit with only three gears. Four and five add to efficiency, but beyond that they simply add to top end speed and/or acceleration capabilities.