riff_raff wrote:autogyro:
Regarding some of the comments in your previous posts:
"In support of current layshaft gearboxes. Development in road vehicles and race cars has always mainly been aimed at the engine and the chassis/aerodynamics."
This is because a well designed manual transmission (MT) is already a very efficient device, so there's not much improvement to be gained here. A good spur gear automotive transmission is likely better than 98% efficient, input to output.
"The IC engine is almost at the end of any efficiency development and the essential improvments have to be found in other areas. The transmission is one of these prime areas of development."
The recip piston IC engine is improving in thermal efficiency and exhaust emmissions at a much faster rate than any other current type of automotive propulsion system, including battery-electric or fuel cell. And this has been the case for the past 20 or 30 years. Current production automotive diesels are now approaching BTE rates of 40% or better, which is an improvement of at least 35% over just the past decade. And newer combustion cycles, like HCCI and PCCI, will result in even greater thermal efficiency gains for the IC engine when they are employed.
As for transmissions, the only type of transmission that is getting more efficient is the conventional automatic (AT). But these efficiency gains come at the cost of much greater complexity, due to the greater number of gear ratios they now employ. In fact, a modern 6 or 7 speed AT is easily the most expensive and complex part of the car it is installed in. The basic manual transmissions has not gotten any more efficient over the last 20 years. However, dual clutch automated manual transmissions (AMT's) with sophisticated digital controls, are now displacing the conventional automatics, due to their lower costs and better efficiencies.
"A good gearbox can also improve the efficiency of a pure electric vehicle."
The reason this is true is due to the inherent operating limits of the typical AC motor used in automotive electrical propulsion systems. Many auto OEM's (such as GM) now use a "dual mode" (ie. dual motor) electrical drive system architecture in their hybrid car transmissions, just to address this very problem.
By the way, I'd be very interested in seeing your transmission design. Where can I get some more details?
Regards,
Terry
Good informative post terry. I have to disagree with your efficiency figures however. The torque in to torque out figures are much more complex and depend on many variables. One major factor being the input RPM another the level of input torque. The effects on IC engine efficiency has also to be calculated plus the effect on electric power input in a hybrid or pure electric.
The 98% given for some modern automatic multi clutch spur gear, lock up converter transmissions and layshaft boxes is the best condition figure and a marketing con. Usually it is calculated with converter locked and the least relative rpm between components and lowest o/s revs in that condition. It is not a fair definition of torque efficiency in over all use. Neither is it for the layshaft gearbox. For one thing the loss of torque through oil windage increases markedly with RPM. Of course any dual shaft box must have twice the laygear losses!
(years ago I used to machine off gears in oval circuit gearboxes to reduce oil windage and I never came close to 98% torque efficiency)
My system has no gears running in an oil bath, there is just an oil mist for tooth lubrication and some cooling, the actual gears have sealed bearings. Only one gear set is engaged for each ratio and the others do not rotate at all unless engaged. In direct top gear there are NO gears turning relative to each other and only one gearset/shaft support bearing. So each gear use in my system would give half at least of the torque loss in all conventional gearboxes, (over all in all gears) and as near to zero torque loss in top gear as you can get (one bearing and far better).
IC engines at 40% are closer to the inefficiencies of external combustion steam engines than to electric motors. It is the currently available gear systems that are defeating major improvements in electric vehicles. The conventional systems do not like the instant and high application of torque given by electric motors. This is why the Tesla went back to one direct gear (the three speed unit they tried first would only last 2000 miles). Which is not as some people say 'no gearbox' because there is a ratio drop. It is a one speed gearbox. Most small EV use belt drive for cost/efficiency reasons, they are yet to realize the horrible noise result in practice. Unfortunately the
transmission engineering has not yet been fully appreciated by the highly qualified electronics engineers who by and large have very little experience of practical vehicle development and even less in
transmission experience. It annoys me that they use the superb power delivery of electric motors to try and convince other engineers with years of experience in vehicles that no gearbox is needed.
All this is why it was a criminal move by Fota, when it forced Kers to be dropped.
Kers is an area of development that is essential for F1 and the continued development of vehicles through the EV revolution. The ban will hold back road vehicles by years and allow inefficient first generation EV's into production to bolster the big car companies through the government hand outs they now live off.
My ESERU can also be configured as an 'integral' part of a far more efficient energy harvesting unit for either Kers or non Kers use. It can also be used for a multi hybrid system or a full electric application for road use.