Some loud (and crazy) thinking on automobiles...
At iMechanica, almost none talks about topics from structural dynamics and design, theory of machines, automotive mechanics, space mechanics, etc.
Let me help correct this situation by raising two questions below. Well-thought answers from any individual are welcome.
First, some background for the questions.
Most Indian cities were not deliberately designed in modern times but have evolved over centuries. Therefore, the in-city roads are, typically, very narrow, with very sharp turns in the bylanes. Parking space is almost a dream. (BTW, many European cities too carry narrow roads, I have heard, though not as much of traffic congestion.)
So, in such cities, small and low-powered cars should fit ideally. Low power ought not be an issue. At least in India, due to heavy traffic in the city, you can't go above approx. 40 kmph anyways! (Head-on collision is not a concern, but fender-bender is such a routine that none even takes notice of scratches and little bumps for years!!)
For ultra-small cars like Kei cars (and I got to know of the existence of this category only yesterday after browsing Wikipedia), people *have* used engines as small as 100 to 360 cc in the past (in 1940s and 50s). There are others like Smart Fortwo.
Yet, the smallest car in India has the engine displacement as big as 800 cc (Maruti). It has the fuel efficiency of about 18 (km/liter), and costs, say, about 2.25 lacs (i.e. about 5,600 US dollars.) It has brake-power of some 27 kW.
Compare the above data to that for the modern, fuel-efficient motorcycles now available in India: 100 - 150 cc engine, fuel efficiency of 80 to 100+ km/liter, cost of about 0.40 to 1.0 lacs (~1000 to ~2,500 US dollars), and brake-power of about 6 to 10 kW.
Also, keep in mind the data for REVA (electric vehicle for two people with a range of 80 km on a single charge). Cost is 2+ lacs (pl. look-up) and the traction motor is rated at 13 kW (max) DC.
Auto-rickshaw: 175 - 275 cc, 6 - 7 kW, 30 km/liter
Now, the two sets of questions I have.
(1) Why can't manufacturers introduce car smaller than Maruti-800 for markets like India (and many other developing countries)?
I have no details on Tata's Re. 1 lac (2,500 USD) car. But the electric car REVA has even smaller wheel-base, which makes it far more easily maneuverable.
My idea is to have a petrol/diesel car of a size that falls in between REVA and Maruti-800, but of low power (just about 300-400 cc). It would be ideal for many Indian cities. You don't even need 500 cc. The choice doesn't have to be the lowly three-wheeler auto-rickshaw (which doesn't even have doors) and then, directly the Maruti-800 car. I think there is a lot of space in between. So, why not have a car in between? Are there any suppressive government controls? Are there a lot of licensing hassles (like a lot of road-safety tests) if I make a small car out of hobby?
(2) Trains can easily run on two or three engines--synchronization is not much of an issue there. What technical problems would arise if I directly put two 100/150 cc motorcycle engines, one each for the front and rear axles, without any transmission directly connecting the two engines? Say, with a mini variety of automatic gear transmission, separately for each axle? (Or, simply, the continuously varying belt.) There could be some embedded electronics to synchronize their running.
The transmission losses could come down this way. Another advantage is that the car will have redundancy built-in. (Even if one engine fails, I don't have to tow the car--I could at least make it back home.) An ability to keep one engine completely switched off if only one/two people ride the car is another (boosting the fuel efficiency). Availability of service expertise is yet another bonus.
With this dual configuratino, I could easily get, say, 15 kW of power (enough to make even difficult in-city gradients with 4/5 people), about 75 kmph of top speed, and about 40 km/liter of fuel efficiency (or much higher, if one engine is switched off while cruising), with far greater maneaverability, 1/3 less parking space. There are bound to be other advantages...
Of course, none puts two engines on two axles in the same car. I am sure people must have thought of it in the early history of car designing and then given it up for some good set of reasons. So, I am sure there are bound to be a lot of disadvantages. What are the glaring ones? And are they enough, in the modern context, to give up the idea of the double engine car?