Response to Kim Goltermann's Comments
MegaRail Transportation Systems, Inc.
I have been reading the comments of Kim
Goltermann with great interest. Goltermann is bringing a healthy dose of
common sense to the debate. I find myself in agreement with most of his conclusions,
as they are largely identical to those that I developed over many years of study and
analysis of both the problems and potential solutions to the same. I want to take
this opportunity to add my on comments in both areas of agreement and the few areas in
which I disagree.
After being attacked by both dedicated steel rail and maglev advocates for the use of pneumatic tires in MegaRail, it is comforting to hear someone else make such an excellent case for pneumatic tires. I will add a few comments of my own on this matter.
First of all, the use of pneumatic tires for dualmode vehicles on conventional roads is essential. Unless we are to provide an entirely separate (and probably prohibitively expensive) set of supports and drive trains for automated guideway travel, we are forced to use pneumatic tires. Thus, from a practical, economic standpoint, it probably essential that these vehicles use pneumatic tires. Consideration of anything else is probably unrealistic.
The need for pneumatic tire for dualmode cars is one of the major obstacles to use of any sort of maglev for such cars. It is one of the primary reasons that MegaRail has not adopted a maglev approach, although we believe that we have developed means to overcome much of the added cost problem for such maglev applications.
Again, I want to emphasis the point that I am convinced that we must provide a system the enables eventual (and gradual) transition to affordable, dualmode electric cars. The need for such is inevitable because of the increasing cost of hydrocarbon fuels and the increasing need to reduce emissions into the atmosphere. The latter reason is already urgent in large cities around the world.
Goltermannıs assessment of pneumatic tire problems, advantages and limitations is excellent. I want to address some of the points made in the paper. Pneumatic tires are indeed inexpensive and highly reliable. The reliability of pneumatic tires used on a smooth steel rail such as that in MegaRail is expected to greatly improve both reliability and tire life. The absence of any rough or broken pavement in the MegaRail application removes all of the usual causes of damage to tires that can cause either air loss or blowouts. The only major remaining tire reliability factor is that of heat build-up. In MegaRail, this factor is reduced by the following steps: Top speed is limited to 125 mph to maintain tires safely within operating speed limits; the tires are always fully inflated to high pressure to minimize flexure, heat generation, and energy waste; and adequate cooling air flow around the tires is assured by the rail and vehicle design. MegaRail vehicles will use an automated tire monitor and inflation system to assure correct inflation at all times. In the case of dualmode cars, the system will adjust the pressure between street and guideway uses. (Note that when operating on an absolutely smooth steel rail, little tire flexure is needed, thus allowing use of increased tire pressures.)
Goltermann correctly mentions the uncertainties of tire traction with various traction surface conditions such as water, ice, snow, etc. This problem is avoided in MegaRail by providing an enclosed rail design in which the tires always operate on dry surfaces inside the enclosed rails. This feature enables the system to operate safely under any kind of weather conditions. Such a capability is essential for any automated system even in such dry area such as southern California. It must be remembered that there are very few places on the planet in which it never rains. A practical transit system must neither shut down nor endanger users because of weather.
I agree with the Goltermann contention regarding the energy efficiency of pneumatic tires. Much of the energy loss (as heat) in pneumatic tires results from sidewall flexure of the tires rather than just the compression of the rubber in the tread. By use of high pressures, as is possible and desirable on a smooth rail surface, the energy loss is greatly reduced. True, the loss will always be greater than that involved in steel wheels on steel rails, but it is well within acceptable limits. The loss may also possibly be somewhat larger than the drag losses in maglev systems, but the loss in efficiency is probably more than balanced by the far lower cost pneumatic tire systems.
At the present time and with current technology, maglev is also probably not acceptable from the standpoint of economics except for possibly very limited high-speed applications. Itıs use for in-city transit, dualmode cars, and short haul travel is not likely to become practical. I make this point although MegaRail is actively working to alter this situation. [Other views on the future of maglev]
Steel wheels operating on steel rails has been offered as a solution. However, such systems typically present three major problems. First of all, without a separate means of propulsion such as some sort of linear motor, such systems have unacceptable grade performance for most applications. Secondly, steel wheels on steel rails generate unacceptable levels of noise at high speeds to permit their use in many locations. Thirdly, any dualmode car would have to have separate, extendable steel wheels and drive mechanisms to operate on a steel rail guideway. (Such a requirement for separate suspension and drive mechanisms probably makes a dualmode car largely impractical.)
I agree with Goltermannıs assessment of the difficulties involved in providing high speed switching for a maglev system. It is far more complex and expensive than the relatively simple switching mechanisms that can be provided for pneumatic tire systems.
After all of the above agreement, I must disagree with the Goltermann conclusion that LSM propulsion in conjunction with wheeled system is an attractive approach. Although LSM offers some potentially attractive speed control and absence of moving parts advantages, LSM does not have an overall advantage for a number of reasons. If the traction problem is solved by use of pneumatic tires operating on smooth dry surfaces, more conventional and lower cost rotary electric motors can also do the job at far less overall cost. Furthermore, use of multiple motors per vehicle offers a higher level of protection from motor failures. It is also neither an easy nor an inexpensive matter to equip a dualmode car with a separate LSM propulsion system for guideway use only. Bear in mind, that a true dualmode car must be the ultimate objective. Like maglev suspension, LSMs must also be protected from weather elements if practical use is to be made of such systems. Such protection is not easily provided. Other than in our own MegaRail maglev designs, I have seen no evidence of anyone proposing use of such a system providing any effective weather protection other than covering the entire guideway in some manner. Finally, both guideway and vehicle cost and complexity are greatly increased with the use of LSMs, without any major benefit. Sure, LSM has the same sort of high tech appeal as maglev, but high tech appeal alone does not justify use of either in a practical system!
The argument has been advanced in the dualmode debate that LSMs have no moving parts and offer higher efficiency than rotary electric motors. Such is not necessarily the case. The writers may be considering energy loses in and complexity of gear trains often used with rotary motors. If a concentric motor-wheel is used, the efficiency is essentially equal.
Goltermann cites the usual claim that LSMs offer a simple solution to the problems of vehicle spacing and speed control as a major reason for LSM use. This claim is valid as long as no motor failures occur. Unfortunately, any propulsion failure can instantly eliminate this control, making it necessary to provide some reliable backup capability. Both the vehicle-along-track position and speed control problems can also be handled by other very reliable means. Use of multiple redundant, voting electronic control systems can provide the needed control with the necessary degree of safety and reliability. The techniques for multiple redundant control with voting and automated failure recovery developed for use in fly-by-wire aircraft flight control systems can be easily adopted for this use. Because of the greatly reduced complexity of the automated transit vehicle control problem from that of aircraft flight control, the size, complexity and cost of such controls are affordable for transit use.
Goltermannıs assessment of the problems of getting people off of a failed system in which vehicles are suspended from above should be taken seriously by all involved in automated transit system design. This problem was considered to be of importance in the MegaRail design. Both MegaRail dualmode and rail-only vehicles are equipped with small internal batteries that provide a limited means to move the vehicles along the track in the event of major power outages. System control systems are protected from power failures by use of non-interruptible power supplies. MegaRail will also provide means for vehicles to push vehicles with disabled propulsion systems along the rail to exit points. As a last resort, MegaRail will also provide for push out escape doors on the sides of transit vehicles to enable passengers to exit the vehicles to the top of the rail. The top of the side-mounted MegaRail provides a narrow, but usable escape walkway away from the vehicle.
Kim Goltermann offers an excellent analysis of the speed question. He is entirely correct with regard to the energy used to overcome drag at high speeds. Because the energy to overcome aerodynamic drag increases in proportion to the square of velocity, we pay a major penalty in terms of energy for high-speed travel. Consequently a careful trade must always be made between the objective of short travel time and energy use. Such factors as loss in pneumatic tires are well down in the noise in comparison to drag losses. This is one of the reasons for setting an upper speed limit in MegaRail at 125 mph. The energy cost start to become unacceptable for most users above this speed. Wind noise is another major consideration in limiting dualmode and carried conventional automobile speeds in the system. Most passengers are not willing to accept high noise levels and it is difficult to build sufficiently clean automobiles to keep wind noise within acceptable levels at high speeds. One of the major noise problems in the cleanest of automobiles is aerodynamic buffet from the outside mirrors that are almost essential in modern traffic. I know that in my very aerodynamic and well sound proofed Chrysler LHS, these mirrors are the major source of wind noise.
Goltermann is entirely correct in the statements that dualmode transit systems should not attempt to compete with airliners. The total costs involved in such a competition are beyond the range of practical affordability. Fortunately, a moderate (125 mph) speed such as MegaRail can offer provides a significant level of competition for airline travel for short haul routes for several reasons. The ability for a user to drive his or her personal car onto a ramp and travel non-stop at 125 mph to an exit ramp in a destination city offers a significant travel time reduction. The total overall trip time for trips of up to several hundred miles can be significantly less than the time for airline and related ground transit time. A similar situation is also true for inter-city PRT or scheduled inter-city car service. The weatherproof nature of MegaRail can also be a major factor in inter-city travel time. It never has to wait for rain, fog, ice, thunderstorms, or runway position.
The points regarding high-speed cargo shipment are excellent. Few cargo carriers need extremely high speed nor will be willing to pay the price for 200-mph cargo travel. This was another reason for limiting the MegaRail top speed to 125 mph. By providing a high degree of aerodynamics for MegaRail automated cargo containers, the shipping cost will be competitive with that for current 75 mph over the road trucks with drivers driving heavy truck tractors to pull the trucks. MegaRail is also offering a separate heavy cargo rail system for use along railroad rights-of-way for lower (75-mph) speed, heavy cargo containers. Such heavy cargo systems will be far more limited in coverage than standard MegaRail, but will enable a major increase in railroad capacity for carriage of much current heavy truck cargo. This capability is designed to provide much needed relief of major highways from heavy truck traffic.
Kim Goltermannıs comments are comforting to us at MegaRail after the several attacks in the dualmode debate pages on MegaRail. MegaRail has been castigated for: (1) using wheels with pneumatic tires instead of far more expensive maglev or more energy efficient steel wheels on steel rails; (2) using rotary electric motors rather than rushing headlong into use of far more expensive LSM propulsion; (3) limiting speed to 125 mph instead of attempting to run at 300 to 400 mph; (4) providing a ferry system rather offering dualmode only; and (5) offering a low-cost system that can be built in the near term rather than waiting for some ultimate system capability.
We have seen a lot of discussion on the dualmode debate page insisting upon use of high tech (and expensive) features such as maglev and LSMs for a future dualmode system. In most of the papers presented, system cost does not appear to be any real consideration. Most contributors seem to assume that the U.S. Federal Government is going to somehow provide almost unlimited tax dollars to build a national dualmode network. MegaRail was even referred to as a "cheap" system by one of the writers and MegaRail was blasted for having a goal of making a profit from its efforts!
In closing, I want to say that I do not believe that we are going to see the U.S. Federal Government be able to commit the funds to build any of the often proposed high-tech and expensive systems on a wide scale basis. In the end, the only system that can really be built on a large scale is a system that can pay for itself from operating revenue generated by the system. Furthermore, such a system can probably be developed and implemented only by a for-profit company committed to the task. Government organized committees directed by bureaucrats will not be able to do the job. MegaRail Transportation is a for-profit corporation dedicated to solving the problem and we are not ashamed of our intent to earn a return for our investors.
I want to remind the readers of this page that Henry Ford organized a for-profit company that was largely responsible for the development of the mass produced automobile. From first hand experience, I can assure you that the Ford Model T was really not much of a car. Iım of the age that had to ride in Model T cars a few times. It wasnıt a very good ride, but it beat the walking alternative. The Model T had the great feature of being designed to be affordable by the general public and that was the key to success. I have no doubt that critics did not also attack the Model T for being a "cheap" car of lesser quality than other cars of the day.
Last modified: September 07, 2000