Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Automotive External mechanical drive for cars and trucks

  1. Aug 19, 2012 #1
    Hi everybody!

    I've been toying around with ideas for using electricity to propel any type of vehicle - gasoline, diesel, hybrid, or electric. The problem is I am not a Mechanical Engineer. So I'm wondering if anybody can tell me whether a drive system like this may be designed to be practical and efficient?


    Thanks for any feedback!
  2. jcsd
  3. Aug 21, 2012 #2


    User Avatar

    Staff: Mentor

    The idea is to tow all the cars and vehicles around with long belts and chains?
  4. Aug 21, 2012 #3
    Hi berkeman, and thanks for your response.

    It's a long article that discusses lots of different issues. I tried to paste a picture of the drive itself so that I could ask a question about the mechanics, without wasting people's time on the other discussions in the article (benefits of electricity versus gasoline and diesel, etc). But for some reason I could not get the picture of the drive to show up in the forum.

    So here's my specific questions. If you look at the second picture down from the top of the page at that link. Is it possible to design a drive like this that will:

    1) propel a vehicle at highway speeds (approximately 65 mph)

    2) transfer energy efficiently (say 90% or above)

    3) work reliably in outdoor weather

    Thanks again!

    Oh... and if you know of a good source of information that would help a non-mechanical guy understand the feasibility of the various options for the mechanical transfer of energy between the highway and vehicles, that would also be greatly appreciated!
  5. Aug 21, 2012 #4
    Well I guess somebody has hacked my site, as I am now unable to access even my own pictures. I don't know how much sense you can make of the article without the pictures.
  6. Aug 21, 2012 #5

    jack action

    User Avatar
    Science Advisor
    Gold Member

    Your answer lies with the concept of cable car. According to Wikipedia:
  7. Aug 21, 2012 #6
    Anti-Gravity Drive for Cars and Trucks

    Been trying to discuss this on TheSaturnWire.com, but my site keeps getting hacked. Without the ability to post pictures, I'll just describe it in writing.

    Cars and trucks are dragged up a mountain slope with a mechanical drive, something like a roller coaster. Vehicles in the opposite lanes (going downhill) engage a similar drive system, generating energy as they descend. The energy generated by descending vehicles propels vehicles that are climbing the mountain.

    The mechanical drive is actuated by electric motors. This allows hybrid and electric vehicles to apply their regenerative braking systems full force whenever they engage the drive system. The motors (in the highway) provide enough power to not only propel these vehicles, but to charge their batteries as well. Because motors in the highway are not carried on board vehicles, they may easily be sized with enough power to realize these design goals.

    Hybrid and electric vehicles periodically engage a similar drive system on level ground in order to allow them to apply regenerative braking for the purpose of battery charging. This allows vehicles to "fuel" without stopping, and provides infinite range for electric vehicles. It also allows hybrid and electric vehicles to have smaller, less expensive batteries, a key requirement for expanding the adoption of hybrid and electric vehicle technology.

    I am thinking that mechanical couplings are able to transfer energy at high rates and with high efficiencies, so batteries may be charged quickly (over short distances) compared with other technologies. This means a charging system does not require a lot of infrastructure. Hopefully a vehicle could charge for (say) one mile, then drive for 10 miles on its on power, then charge for a mile, etc. Of course, there are other ways of building a system that would look similar to this one - vehicles riding on electric rails, as an example. But my question (which will appear at the bottom of this post) is about the mechanical drive.

    The drive system is connected to the local electricity grid. Any imbalances in the production and consumption of electricity are handled by the local electric utility. (They already know how to do this, and already have the infrastructure to do it. Plus it allows vehicles to generate electricity for other purposes that have nothing to do with transportation (in the event more electricity is being generated than is being consumed.))

    I am not a mechanical engineer, so my ideas about what a drive like this would actually look like are probably pretty naive. They include:

    * A motorcycle chain like drive, or a similar belt drive. The chain or belt engages a "sprocket" on the axle of a vehicle's wheel. The sprocket rotates at the same rpm as the tire. But the sprocket is half the radius of the tire. This allows the belt or chain to travel with a speed of X mph with respect to the ground, and the vehicle to travel with a speed of X mph with respect to the chain, and with the speed of 2X mph with respect to the ground.

    * Spinning tires protrude through slots in the highway, engaging a pad on the underside of vehicles. Or spinning tires have vertical axes, and are located on the right and left side of a lane. Vehicles have pads on their right and left sides. In this case the tires squeeze the pads on either side of the vehicles and propel them forward much like the operation of a baseball pitching machine. Whenever no cars are coming, regenerative braking is used to bring the tires and motors to a stop, thus recovering the energy that is suspended in their motion.

    * Some kind of worm drive that looks a little like this:

    http://www.bigjacktools.com/images/6%20inch%20ice%20bits.JPG [Broken]

    The worm pushes on a little wheel that extends from the car. I wonder if direct drive would be possible here... since the worm could rotate at a very high rate.

    The main reasons for my interest in the mechanical drive are:

    * High rates of energy transfer are possible, (hopefully) allowing fully loaded tractor trailers to ascend a mountain at 65 mph, and (hopefully) allowing electric and hybrid batteries to be quickly charged.

    * The mechanical transfer of energy is potentially very efficient.

    * A mechanical system allows any type of vehicle - gasoline, diesel, hybrid, or electric - to be powered by electricity (at least over the portion of highway that is provided with the drive system). It also allows any type of vehicle to use regenerative braking to recover kinetic and potential energy.

    * The system allows any source of energy - coal, natural gas, wind, etc. - to propel any type of vehicle - gasoline, diesel, hybrid, or electric.

    There are many more benefits, but I'm trying to be brief in this post.

    So here's my question:

    * Can an "external" mechanical drive propel vehicles at highway speeds (65 mph?), and if so, what kind of drive would do that?
    Last edited by a moderator: May 6, 2017
  8. Aug 21, 2012 #7
    Couldn't get this thread to work, so I started a new one instead. Is there a way to delete this thread? I don't want to clutter the forum.
  9. Aug 21, 2012 #8


    User Avatar

    Staff: Mentor

    Multiple posting is not allowed. I'll merge the two threads into one. Why would starting a new thread fix something?
  10. Aug 21, 2012 #9


    User Avatar

    Staff: Mentor

    Ah, now I see that the "other thread" was a copy of your own website posting. It's merged into this thread now.

    Did you see Jack Action's post? That should give you your answer as to why this is not a practical idea...
  11. Aug 21, 2012 #10
    Yes, I saw Jack Action's post. However, it doesn't address the "pitching machine" idea in post #6 above. Also, I guess I didn't make clear that the proposed system would have many short segments of "cable" (belt, chain, or whatever). In this case, there would be no (or few) sheaves and guiderollers... no? And finally, the proposed system would charge electric and hybrid vehicles.

    Also, cable cars were invented years ago, long before we had strong, light-weight, composite materials.
    Last edited: Aug 22, 2012
  12. Aug 22, 2012 #11
    I don't think these ideas can be dismissed merely as "cable car". For one thing, there are so many incarnations. Consider this one for example. An electric car driving in the city encounters a mechanical drive that stretches for 1/4 mile. It is in the right hand lane, and the speed in this lane is only 10 or 20 mph. Though the mechanical drive is moving slowly, it is powered by motors capable of providing a large propelling force for the car. So the car applies regenerative braking full force. But this is not the usual regenerative braking. For the purpose of discussion, suppose the car has a separate electrical generator specifically for recharging its battery under this circumstance. So the generator is connected to the wheels through a transmission. Though the wheels rotate slowly, the generator is rotating rapidly. It is rotating at a rate optimized for recharging the battery at this exact low speed. Because the external drive is able to apply considerable motive force to the car, a lot of electricity can be generated in a short space of time. So the car does a lot of recharging, but doesn't even stop at a fueling or recharging station. No congested traffic, little time waiting to be refueled, smaller, cheaper, lighter batteries because you don't have to go far before you'll encounter another external drive to charge some more. I can believe that it might be difficult if not impossible to design a mechanical drive that will propel vehicles at highway speeds, but surely there is a mechanical solution for a low speed drive like this?
  13. Aug 22, 2012 #12

    jack action

    User Avatar
    Science Advisor
    Gold Member

    You don't seem to be able to realize how big needs to be the mechanical drive to propel your vehicles and how much wear goes into this.

    The SF cable cars go only 9.5 mph, and the cable only needs to transmit enough power to move them; there is no need to recharge battery in addition. The length of the cable creates an enormous mass that needs to be supported by pulleys, otherwise the cable will not stay straight (even if you put a succession of short cables, you still need those pulleys). All of these pulleys will require power to turn them.

    While pulling your vehicles, the cable will wear, at the very least stretch. It will need to be change frequently. The SF cable cars change their cables every 6-8 months. That's costly.

    You can replace the cable by a chain. Chains takes power, wear and stretch too. They can transmit more power than cables, but they also cost more. Sprockets are more costly than pulleys too.

    You could also go with driveshafts and gears (for your spinning wheels on vertical axis system), you are still stuck with similar problems of cost and maintenance.

    Any design that you can think of, it is either cheap to buy, but costly to operate due to wear, or it is costly to buy because of complexity, but cheaper to operate. With some systems you might end up with high costs everywhere. And any way you look at it, power loss to move the mechanism will be there.

    The way to transmit power on a long distance with the least amount of losses - and that is cheap and low maintenance - is still electricity by cable.
  14. Aug 22, 2012 #13
    Yes, the more I think about it, the more I think you must certainly be right. But there is one exception, and that is the idea of a drive that is the "mirror image" of the drive that vehicles already use. This would have a tire protruding through a slot in the highway. The tire engages a pad on the underside of the car. At least during the time that a tire is engaging the underside of a vehicle, the efficiency of this drive would have to be the same (actually, probably better) than the efficiency of what cars currently do, since it is really exactly the same thing. Cost and maintenance would also be the identical, if not better. If these things are true, then the question becomes how much energy is wasted due to the inability of the system to recover 100% of the energy that is left suspended in the rotary motion of the tire and the generator after the car has disengaged from the tire. It seems to me that this would depend mostly on the amount of traffic. There are highways here in southern California where a tire in a system like this would be in constant contact with a vehicle, because there is so much traffic on the road. (This might be especially true if such "charging segments" attract traffic because people want to charge their vehicles.) In this case, the tire just keeps on spinning even in between cars, and no attempt is made to use "regenerative braking" to recover the spinning energy. So if a highway has short segments that are like this for recharging hybrid and electric cars, seems like it might be effective, especially when you consider the convenience of charging in motion, and the possibility of smaller batteries for hybrids and electrics. But I guess I just don't have a concept of how much energy is wasted in the energy recovery process, and in having the tires spin even when there is no car to engage them... I guess it is possibly quite a lot of energy.
  15. Aug 22, 2012 #14
    Oh... by the way, I still think there is some merit to using the energy generated by cars going down a mountain to power cars going up the mountain. But you are probably correct in asserting that this energy should be transferred from one vehicle to another in the form of electricity, through electrified rails or something like that. And the system is load balanced by connecting it to the local electricity grid. The reason I was focused on a mechanical drive is I was wondering if non-electric (diesel and gasoline) vehicles could participate in such a system, and also because I thought it would be pretty cool if a fully loaded tractor trailer could go up a mountain at 65 mph.

    The only other way I can think of to power gasoline and diesel vehicles with electricity would have electronically dispatched "helper vehicles" available at the top and bottom of mountains. In this case, when you begin to ascend the mountain, you punch a button on the dashboard that signals the helper vehicle that you want to be pushed or pulled up the mountain. The helper vehicle is powered by electricity, and I guess it would probably ride on rails. So you pull in behind the vehicle and hitch to it, and it pulls you up the mountain, or something like that. When the two of you reach the top of the mountain, you detach from the helper vehicle, and the helper vehicle goes over into the descending lane of traffic and waits for a car or truck that needs help descending the mountain. When helping a vehicle down the mountain, the helper vehicle's regenerative braking system is applied, which charges its battery. A system like this wouldn't need to be grid connected because it is able to store enough energy in its battery to meet load balancing requirements. Well... it could be grid connected, just not through some cumbersome apparatus such as electrified rails. Instead, it would just plug into the grid while waiting at the top or bottom of the mountain. And based on your feedback Mr. Jack Action, I guess this might be a better type of "mechanical drive" for charging hybrids and electrics as well. One nice thing about it - it would require minimal modification of existing vehicles... basically just add a hitching mechanism, or maybe a bumper if it was being pushed.

    Oh... by the way, the helper vehicle, being specialized for going up mountains, has LOTS AND LOTS of horsepower, and can move a fully loaded tractor trailer at high speeds up the mountain. This is cost effective, and does not waste energy, because the vehicle is able to recoup any kinetic or potential energy invested in its motion or elevation via the regenerative braking mechanism.
    Last edited: Aug 22, 2012
  16. Aug 22, 2012 #15
    OK... I'm going to update the original article to reflect these ideas... as I have time to do so:

    http://www.thesaturnwire.com/technology-from-saturn-and-neptune/every-car-is-an-electric-car [Broken]
    Last edited by a moderator: May 6, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook