Limitless LibertyMkiii's 200+ or bust project

LibertyMKiii

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For those of you who follow me on YouTube the cat is out of the bag...
I am making a 100% custom car with the goal of 200+ mph! This will be my final build as I want to get back into 1:1 cars.
The plan is to go see my local CNC guy in the next week or two and take my 3d print mock up to be made in aluminum for the motor mounts and bearing carriers. The lower and upper chassis will be carbon fiber. The body will be carbon fiber also (more on that later)


Here is a few renderings of the car in completed form:

bodyCapture.JPG

bottom chassis and body Capture.JPG

rearCapture.JPG
 

The Donut Man

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Can’t wait to see the progress! Cutting the width of the cross-sectional area roughly in half is a great move for reducing drag. Is the dip in the profile where the nose transitions to the rest of the body purely aerodynamic, or is it there for stiffness?
 

LibertyMKiii

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Can’t wait to see the progress! Cutting the width of the cross-sectional area roughly in half is a great move for reducing drag. Is the dip in the profile where the nose transitions to the rest of the body purely aerodynamic, or is it there for stiffness?

Absolutely... the key to going fasters is reducing the aero drag!

To answer your question.... Both

I wanted to generate downforce enough to have grip with the foam tires (goal #1)
The contours of the body to provide stiffness.

I used this channel through the front rising towards the rear to generate downforce for both the front and rear. I may additionally add a small airfoil on the vertical stabilizer.
 

LibertyMKiii

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So cool! And a little sad to hear it will be your final build. I do hope it results in new RC world record

ps. Any chance you used https://airshaper.com to validate your aerodynamics? They have really improved a lot since the last time i used it.
Had never heard of it before but gave it a try. (I figure I spend $100 to make a mold of the body + more to make the body.... so a $50 test is worth it.)
Everything looks pretty good to me. I'll be honest I think the Fusion CFD might be better although harder to setup...
About 2 hours after a rep from Air Shaper emailed me to talk about the airflow on my design. He was asking if I was looking for downforce in the front or outright reduced drag. That is nice they offer to assist with the purchase of the simulation.

I have done enough trial and error along with CFD analysis on these bodies now that I think I must have it down pretty good ;)

Horizonta streamlines Capture.JPG

Horizontal streamlines rear.JPG

vertical streamlines.JPG

Surface friction 1.JPG

The view angle of this software makes the nose look much longer than it is...
 
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LibertyMKiii

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Adding to my intro of this build....


After building several speed RC cars I have come to the inevitable conclusion in this journey where you realize what must be done…. to build a RC speed machine capable of 200+ mph it needs to be custom made.

I absolutely love drawing in CAD and honestly don’t know why it has taken me so long to get to this point. Like all things it does take time to learn the ins and outs of a hobby. Speed running is highly technical and takes engineering to solve the problems the car faces during a run.

Arrma cars are very capable and on the brink of cracking 170 mph soon. The 1/10 4tec 2.0 has nearly reached 180 mph and has more potential still. I had build a very capable stretched 1/7 scale length 4tec 2.0, but didn’t trust the axles, hubs, 12mm hex, and center driveshaft to support the power. Any production RC car will need a significant investment to strengthen the drivetrain and chassis setup to accommodate the batteries and big power. Every out of the box car I had modified seemed to have constraints and limitations that I couldn’t live with. (This is a large part of why I was always changing projects)

I have been avoiding it for a long time, but all paths seem to lead back to the design that Nic Case did years ago when he went 202 mph. This new build of mine is a belt drive solid axle / no suspension design like Nic Case built. The large difference will be that my car will run on production 1/8 103mm foam tires (minus some height from truing the foams down). His car ran on 12s and mine will be on 8s. Also I will be running a body that has gentle sweeping curves and looks darn sexy if I don’t mind saying so myself.

I don’t have any specs for Nic’s car so I went about designing my own based on the parts I wanted to use in the car and my ideal layout. The car will have an XLX2 and battery slots to accommodate 4s LiPos. The motor will be 40mm and can accommodate lengths over 110mm as needed. The motor being used is to be determined, but I will likely start out with testing with a TP4070. The design is such to keep the wires as short as possible between the motor to ESC as well as batteries to ESC.

When trying to go really fast aerodynamics are a massive hurdle. I have a great graphic related to airplanes that illustrates how at a certain speed the power required curve goes nearly straight up. This is like putting dual motors and ESCs in your RC car and not gaining speed. The problem was never power… The issue is aerodynamics!

air plane Capture.JPG

This other graphic is related to bicycles and the power required. Note the GoldRush is a streamliner recumbent (pictured below the graph). The power required is insanely low compared to very expensive racing bikes.

Bicycle drag comparison Capture.JPG
GoldRush bike.JPG
For perspective:
  • 1/7 Arrma or most 1/8 cars the front width is around 305mm. (depending on the tire/wheel choice) +/- 3mm
  • 1/10 on road cars like the 4tec 2.0 are around 200mm width.
  • My design has a 154mm width from outside edge to outside edge of the front 1/8 wheels/tires.
Aerodynamics can be a wormhole of discussion, so I won’t go too deep into this but, the key requirements for this build was the following:
  • Retaining enough downforce for foams to get grip!!!
  • Internal components that can handle big power.
  • Reduced aerodynamic frontal area below 200mm 1/10 scale cars.
  • Proper airflow management for low drag.
  • Low losses from drivetrain (belt drive)
This combination should net result a 200mph car if all goes well.

After testing with the car I might consider selling/producing this as a product. I just want my chance to get some runs in and see if I can set a record first 😉. This car requires a significant amount of CNC work which can be pricey. As it stands right now I am estimating this will be my most expensive to build RC car yet.
 
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(me sounding like i have a real clue of what i am talking about)

Horizontal and vertical lines are looking good, very nice. Did you get a Cd < 0.12 ?
I do wonder if you would benefit from doing more with your floor design and some minimalistic diffuser. This awesome streamline doesn't create much downforce. Just thinking back about how Raz also didn't really get the expected downforce (my interpretation) and went up in the air multiple times. Some Venturi effect on the bottom might get you some more sticking to the ground with minimal effect on your Cd. Obviously keeping your acceleration in bounds would solve this problem too, but then you would need a extreme long road/radio range.

To be honest, I mostly just like the Belgian accent of the airshaper's owner
 

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(me sounding like i have a real clue of what i am talking about)

Horizontal and vertical lines are looking good, very nice. Did you get a Cd < 0.12 ?
I do wonder if you would benefit from doing more with your floor design and some minimalistic diffuser. This awesome streamline doesn't create much downforce. Just thinking back about how Raz also didn't really get the expected downforce (my interpretation) and went up in the air multiple times. Some Venturi effect on the bottom might get you some more sticking to the ground with minimal effect on your Cd. Obviously keeping your acceleration in bounds would solve this problem too, but then you would need a extreme long road/radio range.

To be honest, I mostly just like the Belgian accent of the airshaper's owner
The friction drag which is the green model with the blue spot on the nose, looks absolutely amazing. It seems I got this design pretty good on my first shot. The software didn't tell me the Cd sadly. I expect it is quite low as you mentioned. The body will have a front splitter like all my other have, but that is something I add on during the mold process and not included in my CAD drawing. This will improve the downforce and venturi under the car as well. I will be experimenting with a diffuser in the rear also.

I have been talking back n' forth with the CEO of air shaper. He must have taken an interest in it? I am trying to find out if I can get the moments data to show downforce on the front and back tires to determine downforce balance. That was something I could never determine in Fusion CFD and would be a game changer for me. Without that I am just taking educated guesses at how much downforce it will need.
 
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The Donut Man

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The friction drag which is the green model with the blue spot on the nose, looks absolutely amazing. It seems I got this design pretty good on my first shot. The software didn't tell me the Cd sadly. I expect it is quite low as you mentioned. The body will have a front splitter like all my other have, but that is something I add on during the mold process and not included in my CAD drawing. This will improve the downforce and venturi under the car as well. I will be experimenting with a diffuser in the rear also.

I have been talking back n' forth with the CEO of air shaper. He must have taken an interest in it? I am trying to find out if I can get the moments data to show downforce on the front and back tires to determine downforce balance. That was something I could never determine in Fusion CFD and would be a game changer for me. Without that I am just taking educated guesses at how much downforce it will need.
That’s fantastic; I hope that convo goes somewhere!
 

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Sounds amazing, this will be the most epic RC build ever.. Form truly does follow function with any extreme performance vehicle, and it is very interesting seeing how your computer renderings of your design have slowly evolved along the lines of Nic Case's design.. I'm particularly interested in how what changes you make to the body design would affect the aero balance front to rear.. With that aero body, super narrow cross section and big power the need for traction from foams will be of paramount importance, and also durability.. have any foams ever gone past 180mph without tearing themselves apart? At some point do you anticipate looking into some sort of metal or composite wheels/tires like Nic Case had to do? I'm sure ill have many other questions as you go along lol, great work as always Liberty
For those of you who follow me on YouTube the cat is out of the bag...
I am making a 100% custom car with the goal of 200+ mph! This will be my final build as I want to get back into 1:1 cars.
The plan is to go see my local CNC guy in the next week or two and take my 3d print mock up to be made in aluminum for the motor mounts and bearing carriers. The lower and upper chassis will be carbon fiber. The body will be carbon fiber also (more on that later)


Here is a few renderings of the car in completed form:

View attachment 132595

View attachment 132592

View attachment 132593
The front of your design is somewhat reminiscent of the nose of the Thrust 2 and also the Bloodhound, minus the jet engine intakes of course. Very cool
 

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jondilly1974

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For those of you who follow me on YouTube the cat is out of the bag...
I am making a 100% custom car with the goal of 200+ mph! This will be my final build as I want to get back into 1:1 cars.
The plan is to go see my local CNC guy in the next week or two and take my 3d print mock up to be made in aluminum for the motor mounts and bearing carriers. The lower and upper chassis will be carbon fiber. The body will be carbon fiber also (more on that later)


Here is a few renderings of the car in completed form:

View attachment 132595

View attachment 132592

View attachment 132593
Here is a video you can use to explain the resin bubbles in the CF bodies 😜🤘🏻

 
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For those of you who follow me on YouTube the cat is out of the bag...
I am making a 100% custom car with the goal of 200+ mph! This will be my final build as I want to get back into 1:1 cars.
The plan is to go see my local CNC guy in the next week or two and take my 3d print mock up to be made in aluminum for the motor mounts and bearing carriers. The lower and upper chassis will be carbon fiber. The body will be carbon fiber also (more on that later)


Here is a few renderings of the car in completed form:

View attachment 132595

View attachment 132592

View attachment 132593
No don't stop. Rc hasn't took all of you money yet
 

LibertyMKiii

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Here is a video you can use to explain the resin bubbles in the CF bodies 😜🤘🏻

Those darn resin air bubbles kill me!

That is pretty genius to have inflatable bubbles like that. I have a little separation along the top of the car. Maybe I could utilize this technique :unsure:
Sounds amazing, this will be the most epic RC build ever.. Form truly does follow function with any extreme performance vehicle, and it is very interesting seeing how your computer renderings of your design have slowly evolved along the lines of Nic Case's design.. I'm particularly interested in how what changes you make to the body design would affect the aero balance front to rear.. With that aero body, super narrow cross section and big power the need for traction from foams will be of paramount importance, and also durability.. have any foams ever gone past 180mph without tearing themselves apart? At some point do you anticipate looking into some sort of metal or composite wheels/tires like Nic Case had to do? I'm sure ill have many other questions as you go along lol, great work as always Liberty

The front of your design is somewhat reminiscent of the nose of the Thrust 2 and also the Bloodhound, minus the jet engine intakes of course. Very cool

Technically BSR foams have gone past 180, Nic's cars used foam from John's BSR. Beyond that reference I don't think any others have gone that fast. We will have to see! I am hoping that cutting them down on the lathe to 100mm will help the foams hold up better. The plastic wheel itself is of concern as you noted. I guess we will see how it does also. I don't believe spinning them in the air to 200mph RPMs will prove much as the forces on the wheel and tire are very different in actual road use.

Salt flat land speed cars are definitely the shape to look at for inspiration. They have some very talented engineers designing those cars. For sub-sonic speeds more rounded shapes do best so I avoided any pointed designs or sharp body lines.

Ultimately the goal was to keep the body slim and tight to the chassis and wheels, while retaining smooth curves that will retain downforce with minimal drag.

A modified cutaway view of the front that does not show the steering function for example: (that part is top secret)
FrontSection Analysis Capture 2.JPG
 
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LibertyMKiii

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Small update.
Got the first 1/3 of the body 3D print done. This will be used to create the mold. It was a 34 hour print using PLA and with a 5% infill, overall it went smoothly. This is a solid object so I cannot place it over the wheels/chassis to help visualize the correct placement. I think it is looking good so far!

(not easy to tell but the 3D printed part is propped up on 5mm wide bearings to simulate actual use height.)
Front2Capture.JPG

Center over front Capture.JPG

Another thing I have been thinking on was buying a carbon fiber plate for the chassis. I want the lower chassis to be 3mm plate.
The length needs to be over 29", which means I'll likely have to purchase a 36" carbon fiber plate. These are quite expensive due to their size. After thinking on it I decided it would be ideal to have a test piece incase I discover any issues. I'd be pretty upset to cut up a $300 piece of carbon plate in the wrong way.

I had a good amount of extra CF fabric and some hybrid fabric that I wont be using. Longer story short, I decided to make my own plate for testing uses and will make the final version later out of plate that is professionally done. My homemade CF plate does not have a perfect resin to fiber ratio for strength and hardness.
This one contained 7 layers of fabric and I sandwiched it between two sheets of wood with some weight on top for 2 days while it cured. This would have turned out pretty good if I had more vacuum bagging plastic. This plastic had been used already and was wadded up under my work bench. The wrinkles translated out to the final surface finish. That is fine for me since it is for test use anyway (y)
I still need to cut it and determine what thickness it came out to.

I realize this could have been done out of Acrylic/Lexan or wood, but these materials will most closely simulate the final version of what I want.

Test chassis plateCapture.JPG

Test chassis plate 2Capture.JPG
 

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Small update.
Got the first 1/3 of the body 3D print done. This will be used to create the mold. It was a 34 hour print using PLA and with a 5% infill, overall it went smoothly. This is a solid object so I cannot place it over the wheels/chassis to help visualize the correct placement. I think it is looking good so far!

(not easy to tell but the 3D printed part is propped up on 5mm wide bearings to simulate actual use height.)
View attachment 134035

View attachment 134036

Another thing I have been thinking on was buying a carbon fiber plate for the chassis. I want the lower chassis to be 3mm plate.
The length needs to be over 29", which means I'll likely have to purchase a 36" carbon fiber plate. These are quite expensive due to their size. After thinking on it I decided it would be ideal to have a test piece incase I discover any issues. I'd be pretty upset to cut up a $300 piece of carbon plate in the wrong way.

I had a good amount of extra CF fabric and some hybrid fabric that I wont be using. Longer story short, I decided to make my own plate for testing uses and will make the final version later out of plate that is professionally done. My homemade CF plate does not have a perfect resin to fiber ratio for strength and hardness.
This one contained 7 layers of fabric and I sandwiched it between two sheets of wood with some weight on top for 2 days while it cured. This would have turned out pretty good if I had more vacuum bagging plastic. This plastic had been used already and was wadded up under my work bench. The wrinkles translated out to the final surface finish. That is fine for me since it is for test use anyway (y)
I still need to cut it and determine what thickness it came out to.

I realize this could have been done out of Acrylic/Lexan or wood, but these materials will most closely simulate the final version of what I want.

View attachment 134037

View attachment 134038
Looking forward to see the end result :)
 
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