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Fabia130vRS

An idea I wanted to share ! thoughts please.

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the idea is using 4 small motors with propelers pointed through the chassis into the ground just 5mm over ground.

 

imagine a tiny quad drone upside down facing the ground, on full throttle the quad would fly if it is turned around the right way.

 

but this way?

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would it push a F103LM towards ground greating grip force?

 

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having the quad in the middle just net to the battery, or maybe tear the drone in half and 3 print mounts to the middle outter space?

 

 

Lotus gave me such an idea honestly hah :D

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I'm no Adrian Newey when it comes to even simple aerodynamics, but in theory this should work. I'm not sure how effective it will be, since I think it will just lower the ride height and not generate too much of a ground effect or downforce with as simple of a setup that you described, but I'd say to just give it a go out of curiosity. I've always wanted to do some aero work with fans on an RC and I'd love to see if this works. 

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I am a fan of physics and aerodynamics but my knowledge does not go further then imagination.

 

the worst parts is how to pair it to a radio? probably a multiple channel TX/RX and maybe replace the eachine e013 board with a furybee betaflight compatible flight controller.

 

so higher the throttle goes on the cars motor, so the fans would gain in throttle also. programable TXs are I believe capable of that

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I wouldn't link it to the throttle, at least not that way. When lifting off for corners, the last thing you want is for your downforce to go away. Maybe rig it so that the fans throttle up in response to increases in lateral g?

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20 minutes ago, TurnipJF said:

I wouldn't link it to the throttle, at least not that way. When lifting off for corners, the last thing you want is for your downforce to go away. Maybe rig it so that the fans throttle up in response to increases in lateral g?

if you turn the FC (flight controller) upside down and reset the gyro it should save that position as neutral.

 

So if you throttle up a drone to full throttle as terms of height... not left right or any other direction then up, is spins the motors at full rpm but the gyro holds level. motors spin accordingl to reset level on the flight controller as on beging.

so you could also conncet to the transmitter from the car,  1 axis of the ''lean'' left and right + ''pitch'' forward and back from the quad,  in order to switch centre of ground force effect?

 

the point to me is how could I sync the quad and car to shift the drone downforce to each side to which it is neccessary in order to corner better??

 

if that makes sense

 

edit:

for example a bench test of that prototype would be, 

 

car on a stand so tires move free

throttle to 70%

steer right and left

quad behavier should I believe be

thrttle 70% of car, quad throttle 100%

steer right with car, quad left 30% right 70% throttle 

steer left with car, quad left 70% right 30% throttle etc.. 

 

also to note such small drones fly on 1s but should not be hard to fit a 1s batter of 250mAh should last enough for 5min

 

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Hi, perhaps looking into ducted fans (EDF) is a good idea. In my other rc hobby of fighting robots many in the "antweight" 150g class increased down force via EDF leading to HUGE grip, traction and handling  advantages. They were eventually banned!

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So the theory works very well. Be very cool to see something mounted to an RC car. 

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It would need skirts for it to "suck" it to the floor if not your just sucking air from outside in. 

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I remember the Chapperal and the later Lotus and then the development of ground effect cars. It would be brilliant if you could engineer a system that would work. As mentioined you would at least need some kind of side skirts to hold incoming air back to produce a big enough vacuum. Good luck will watch with interest.

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1 hour ago, svenb said:

It would need skirts for it to "suck" it to the floor if not your just sucking air from outside in. 

Yes, like a hovercraft, but if the area is large enough and the ride height is low enough even without skirts you should get a big enough depression for some downforce.

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Questions... how overpowered can you make an rc car motor? Can you make it so overpowered that the car would normally be impossibly traction limited? Then for simplicity have the fan on all the time? So if it ends up matching the speed of the competition on the straight it will destroy them in the corners? Then perhaps you just need your own version of drs to reduce fan at v max. How quick to spin up are the fans? My gut feel says anything driven by measurements of lateral load will have too much lag to generate down force. And if they are instantaneous you might have to adapt to some crazy oversteer. 
if you skirt it, have a think about where to duct the airflow, rather than blowing it out the back or sides it could be used to energise some of the other aero features. You could actually make a shroud to partially restrict the fan at straight wheel angle, easier to mechanically limit rather than electronically.

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1 hour ago, svenb said:

It would need skirts for it to "suck" it to the floor if not your just sucking air from outside in. 

I am 99% sure skirts could be made out of a bicycle inner tire. And some tire cement.

as my idea would be to use a Porsche LeMans body.

Plenty of room inside for 3d printed vents.

I think the most important part is the venturi shaped case on the tinywhoop drone that creates so much power through physics. Because a eachine e013 is fast. Idk the specs now. But might put some details on paper tomorrow.

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this car had a gearing by speed calculators it in theory could reach 190kmh with a fdr 1.54. On a 4.5T mod motor. Sounds ridiculous but it happend and was dummy fast and it flew through the air after two runs the esc thermaled out

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These ground effect cars work mainly  by creating an area of low pressure under the car, which means the normal atmospheric pressure above the car presses down on it. The resultant force (downforce) is the difference in pressure multiplied by the area. So my advice is to maximise the area of low pressure.  

If you look at Hobgoblin's picture, there is a huge flat plate surrounding the fan under the robot. This maximises the area in the pressure*area equation, which maximises the downforce. 

I would say skirts are not necessary - you just need a big ol' flat plate under the car - as big as you can fit. 

As for using a drone and drone controller to control left and right downforce - I think this is unnecessary and might lead to unusual handling. You really only need a single high efficiency fan (or maybe 2, spinning opposite directions to prevent any weird torque effects) and have it act on the whole car. And the only time you wouldn't want it running at full power is when you are at full speed on a straight. As soon as you need to brake for the first corner though, you need it back on so you'd probably just be better off with it on full all the time. 

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I thought the 1/1 fan cars were pushing air out the back of the car and all but the back of the car was “sealed” to reduce the amount of air from getting under it?

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In the type of ground effect the Lotus cars used, the ground effect is a product of the car's speed, as there were no moving parts apart from the skirts, and in the type 88 the whole chassis moved, but was essentially recreating the effect of a skirt. Someone correct me if I'm wrong but I think the 2022 F1 rules allow ground effect again which should be interesting but I digress.

In cars like the Brabham BT46B and the Chapparal the ducted fans produced the suction, which would have been tied to the gearbox, probably the outdrive, so again the suction created is a function of the speed of the car. I don't know if they had a seperate gearbox driving the fan, certainly the BT46B didn't. In the BT46B they used the 'big flat plate' method of sealing under the car, it had big flat areas where the chassis flattened out as much as possible. I think the Chaparral used skirts, I'm not as familiar with it.

An idea - could the skirt be a brush rather than a flat plate? It might not seal as well as a plate but might be better than nothing.

As for how to control the drone fans - I would think you would want them at full power all the time for the greatest advantage. The time it would take to spool up if based on G loads I think would be too slow for the rapid changes in G-loads an RC car experiences. Consider scale here - the loads an RC car experiences don't scale up to bigger cars, it would be the equivalent of a full size F1 car pulling 20Gs through a corner. In real life they can tip 5Gs laterally. I suspect top-speed RC cars would easily hit 5G, but on such small and light bodies (compared to full size) the effects are not as pronounced. And the driver is not subject to them either. :lol:

Does anyone have any data for lateral G-force on an RC car? The only data I have is that a lightwieght recevier got ripped off heavy-duty velcro in a buggy by G-force, and that was with a silvercan. I suspect RC cars experience very high G-forces which would also have an influence on ground-effect forces.

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48 minutes ago, c64orinoco said:

Does anyone have any data for lateral G-force on an RC car?

This should be simple enough to estimate from videos of cars going around race tracks. 

If you take a look at a car during a corner, and assume the car's speed is roughly constant around the corner (or at least the portion you are measuring), then the lateral acceleration can be calculated by estimating the number of radians the car turns through per second, squaring this value then multiplying the result by the radius of the corner in metres.  The answer will be in metres per second. 

As an example, let's say you see a car go around a 90 degree corner with radius of curvature of 2m in 0.5 seconds. 90 degrees is pi/2 radians, so the angular speed is pi radians per second. The acceleration therefore would be pi*pi*2 = about 20 m/s/s, or about 2g. 

0.5 seconds is quite conservative for rc cars with grippy racing tyres, so I expect the maximum possible lateral acceleration to be much higher. 

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