jjustin

I'm doing a class project in my engineering tech program to come up with a unique invention. My invention is to put a air turbine system on top of RC cars which will charge the RC car when the turbines spin from the movement of the car. This will hopefully increase battery life by a good amount. i would like to ask other Rc car hobbist if they would enjoy a device like this and if battery life can be a problem.

transam388

I think what you will run into on most RC cars and trucks is that for a turbine to produce anywhere near enough power to make a significant charge would weigh to much and create more drain on the car as a whole than what it can provide. So you need to be able to produce more energy than the weight and drag of the turbine would take from the car and then also have that ratio be high enough to even warrant doing it.

Now, do not get me wrong as I think it is a cool idea and you should do some research to see if it is an achieveable goal. The other thing and this I do not know how you would do but would this actually charge the battery or just assist the battery so less total energy is taken from it? See what I mean? It basically does not charge the battery but only tries to provide additional power so less would be taken from the battery thus providing longer run time.

Now this one I am going to say is not what you want to hear. I know personally I would not want to put a turbine on top of any of my vehicles just for the way it looks. So this would somehow need to be worked into the body of the vehicle so the outer body is not changed. Another reason I would not want it on top is the center of gravity would make the vehicle more unstable in corners. This again is why I say you would need to try and keep this down in the chassis so the CG is not brought up to high. Regardless the body is going to have to be modified with a set of holes to allow air in and out so in order to really get the best flow this would need to be on top of the vehicle.

So first I would calculate for the average speed of these cars, what speed would a trubine have to spin to generate enough current to warrant this project.
Second, is a trubine that would fit these cars able to produce the above current when run at that average speed?
If yes, where would this be mounted to keep vehicle handling stable?
How much weight is added with this and does this produce more power than it would draw?

Anyway, i am rambling! Give it a try and see what you come up with. Who knows, you might come up with a really cool system and start your own company.? Good luck with it!!

jjustin

Thanks for the reply, but we have already considered some of these problems you have brought up. We have decided that the turbine system can be made almost completely of a light-weight material, something like a plastic or foam, to help avoid adding too much weight to the car. As far as the appearance and center of gravity, we have ideas to mount the turbine(s) to the frame, and keeping it lower to the ground, as well as partially hidden(but with enough space to allow sufficient airflow to the turbine(s). Thanks a lot for your input and we appreciate the speedy reply. Your help and any other ideas would be greatly appreciated as well.

transam388

Cool, good to hear you have already been checking on this stuff.

One thing with RC is that most people do wreck these things so make sure the turbine if plastic or foam is able to withstand some abuse or is protected. So have you tried any wind testing to see if this turbine will even produce enough power at the speeds these RC run?

Check weight and size of turbine and related systems as you really want this in the center of the vehicle so to keep things fairly stable in corners. Putting this on the side of a car would obviously change it's handling.

Ducting is very important. A one way duct will still back up if it has no outlet and of course cause more drag. In order to keep drag adding up even with an input and outlet duct you almost need a tube through the whole thing so air does not wander in the body of the car. Good for cooling but is drag.

So is this going to provide additional current to the systems or actually try to charge the battery / batteries? Of course I think the first is the way to go but just my opinion.

Anyhow, glad you are already working on it and hope it comes together for you!! Good to see some initiative and learning taking place!! [8D]

Access

"put an air turbine system on top of RC cars which will charge the RC car when the turbines spin from the movement of the car"
Is the sole source of the turbine spinning from the movement of the car?
If so, isn't this a non-practical idea, any energy you gain from the turbine is lost in drag(?). Think of running while holding a pinwheel. The pinwheel isn't free energy, it's creating a force counter to your running. Wind utilization (ie. sailing) is one thing, but you can't utilize your own wind, and you can't get something for nothing, conservation of energy is one of the laws of physics. Sailing works b'cos the wind is already there.

Find a physics professor and run the whole thing by him to double-check what I am saying. There are things like microturbines that create their own exhaust (through compression and combustion) and then utilize some of the power of that exhaust to create rotational motion, some of which goes back into the turbine, some which can be used to turn a generator. While they have their disadvantages, one of these microturbines can outdo a 'nitro' (ICE) engine in terms of power/weight ratio. Do something like this and hobbyists will really look up to you.

maybelater29

My Feedback: (1)

Didn't Tekin have an ESC back in the day that had a re-generator...it would pump power back into the battery while you where coasting...using the motor rotation to generate the power......[link=http://s195302033.onlinehome.us/CX/ESC/TekESC11.pdf]here it is.[/link] great idea and keep us posted...

Access

Most modern brushless ESCs do that too, it's a form of 'regenerative breaking'. Basically reversing the flow of energy and using the motor as a generator, the battery as a load. If you hook a scope directly to your battery and brake, you'll see the battery voltage go above the open-circuit voltage, this is one why you never use schottky diodes anymore in RC. I know about this b'cos I had a problem with this in one of my cap-cars, when I broke the power would go back into the DC-DC converter and have nowhere to go, it would end up blowing up the converter if it wasn't designed properly.

Note this only works when you brake, again it's not 'free energy', if it is happening when the ESC is coasting that's b'cos it has 'drag brake' turned on so it is essentially braking any the throttle is in neutral.

transam388

You have the same stance as I stated here..."So you need to be able to produce more energy than the weight and drag of the turbine would take from the car and then also have that ratio be high enough to even warrant doing it. "

As you said, nothing is for free but if you can actually come up with something so efficient that it can create more power than it takes to use then you are onto something. IE turbos and superchargers on real cars. They do actually take power to make power but the gains are way above the power used.

Anyhow, we are on the same page. I still am just glad to see some people in school using their heads and taking some initiative to try something new. If it does not work, you have still gained knowledge. If it does work out, Terrific!!

J.D.T

go large scale, a fan mounted to a car alternator will make 13.5 volts and 60-155 amps, you will need a voltage regulator to keep from boiling the battery dry unless you match the in and out current pretty well, I would try a single big motor but wheel motors are always an option

Access

Yeah, the turbo works b'cos it makes the high-end combustion more effective. In other words, a secondary process that consumes power, but improves the efficiency of the primary process, and/or to raises the maximum output of the primary process.

breezerboat

no, b/c my trucks crashes end over end too much. Not to mention it would increase drag, thus slow my RC down.

Little Green Man

Sorry, but no I would not like a device like this simply because it wouldn't work.

The amount of energy you gain from a turbine would be less than the amount you lose from drag and extra weight. This would actually reduce the battery life. Regenerative braking is the only practical mechanism to extend the battery life, as it only impedes the motion of the car when that's useful - ie when you're braking.

i8tweety

My Feedback: (11)

Effectively, you are attempting to create a perpetual motion machine. The energy used to propel the turbine forward to generate power will always be greater than the energy created by the turbine. Unless you've found a way around the laws of conservation of energy (we're talking nobel prize for life here), it will not work.

jjustin

We are in no way trying to create energy in a form of "free energy."(or trying to go for the nobel prize) We are more or less trying to convert energy by sacrficing speed for longer operation time. We understand there will be a challenge in overwaying the loses with gains but our main goal here is to make operation time longer. This device will most likely not be targeted to the racing side of RC cars.

i8tweety

My Feedback: (11)

Operating time will decrease, not increase. The increased load on the system (force used to operate the turbine) will always consume more energy than it can generate. You end up with a net loss of energy due to inefficiencies in power generation, heat, friction, etc. Increased load on the electric motor used in propelling the vehicle forward will result in that motor's efficiency to decrease as well.

Access

Why not just drive slower / gear lower? KISS. You are taking a very indirect route to solving the problem, and one that will not be as efficient as the direct route.