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LibertyMKiii · 03-19-2018, 04:19 PM

Hello all,

Let me start by stating that this is an out of the normal post in what might seem like the wrong forum. Oddly enough this is a great place for some aerodynamics advice even though most of you have not seen 70+ mph since your youth

I am attempting to build an high speed RC car to beat the world speed record. Currently this record is held by Nic Case at 202 mph.

I do not want to get side tracked on the equipment involved as I have those portions figured out. Instead id like to focus the topic on aerodynamics methods between two ideas.

Idea 1: Building for airflow under the car to utilize the low pressure zone as the down force much like the John Cobb in 1939 went over 369 mph (later went over 400 mph) Railton Mobile special

Idea 2: Build for minimal air flow under the car. This would be much like Collin Chapman's designs from the golden era of F1 with floating side skirts sealing the under side of the car. This design also utilized minimal ride height.

The example here is Speed Demo land speed car which really didn't improve much over the Railton car given 70+ years of advancements. Their "record" was 439mph and had seen speeds much higher (462 mph) during their run outside of the official zone.

I cannot make mine exactly like example 2 as my vehicle is a standard 4 wheel car configuration, where Speed Demon is setup more like a 3 wheeled vehicle with the "pointy rocket" nose cone. I am hopeful to get some insights about aerodynamics at these velocities and near ground aerodynamics.

These RC cars like to go air-born over 70mph so they require some significant downforce. The acceleration is also very extreme as it will get from 20mph up to max speed in less than 15 seconds.

Some technical details for reference:
The weight is around 12-15 lbs. Width will be around 11" and length will be a fairly good size estimated around 30"
The tires / wheels are 4.15" and ill likely shave them down to 4" So I can estimate the total height being around 4.5"
the nets:
Frontal_area_m_2 0.03193542
Drag_N 34.49627467571459
Max power 330 amps at 34V
Electric motor power 11,000 - 15,000 watts

Thanks for any feedback / input you can provide.
This topic tends to be exciting for engineers since you can create the ideal package given there is no driver who needs visibility. (inside the car)

-Liberty

03-19-2018, 04:19 PM	#1 (permalink)
LibertyMKiii EcoModding Lurker Join Date: Mar 2018 Location: Dallas, TX Posts: 35 Thanks: 0 Thanked 7 Times in 6 Posts	High speed aerodynamics advice Hello all, Let me start by stating that this is an out of the normal post in what might seem like the wrong forum. Oddly enough this is a great place for some aerodynamics advice even though most of you have not seen 70+ mph since your youth I am attempting to build an high speed RC car to beat the world speed record. Currently this record is held by Nic Case at 202 mph. I do not want to get side tracked on the equipment involved as I have those portions figured out. Instead id like to focus the topic on aerodynamics methods between two ideas. Idea 1: Building for airflow under the car to utilize the low pressure zone as the down force much like the John Cobb in 1939 went over 369 mph (later went over 400 mph) Railton Mobile special Idea 2: Build for minimal air flow under the car. This would be much like Collin Chapman's designs from the golden era of F1 with floating side skirts sealing the under side of the car. This design also utilized minimal ride height. The example here is Speed Demo land speed car which really didn't improve much over the Railton car given 70+ years of advancements. Their "record" was 439mph and had seen speeds much higher (462 mph) during their run outside of the official zone. I cannot make mine exactly like example 2 as my vehicle is a standard 4 wheel car configuration, where Speed Demon is setup more like a 3 wheeled vehicle with the "pointy rocket" nose cone. I am hopeful to get some insights about aerodynamics at these velocities and near ground aerodynamics. These RC cars like to go air-born over 70mph so they require some significant downforce. The acceleration is also very extreme as it will get from 20mph up to max speed in less than 15 seconds. Some technical details for reference: The weight is around 12-15 lbs. Width will be around 11" and length will be a fairly good size estimated around 30" The tires / wheels are 4.15" and ill likely shave them down to 4" So I can estimate the total height being around 4.5" the nets: Frontal_area_m_2 0.03193542 Drag_N 34.49627467571459 Max power 330 amps at 34V Electric motor power 11,000 - 15,000 watts Thanks for any feedback / input you can provide. This topic tends to be exciting for engineers since you can create the ideal package given there is no driver who needs visibility. (inside the car) -Liberty Last edited by LibertyMKiii; 03-19-2018 at 05:36 PM..