LibertyMKiii's dream speed build (shooting for 200+mph)

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LibertyMKiii

RCTalk Champion
Messages
199
Reaction score
203
Location
Dallas TX
RC Driving Style
  1. Bashing
If you have never seen it before, my inspiration is Nic Case who holds the world record for RC cars at 202mph.
His setup was very custom to say the least.
https://www.bigsquidrc.com/200-mph-rc-car-speed-barrier-broken/

Here is the details about my build. I wanted a small aerodynamic footprint much like Nic's car (1/10 scale on-road). I prefer shaft drive over belt drive (Nic used belt). I have built and run many cars over the years but wanted to do a build that is custom. This build will have a stretched chassis (around 2 ft long) as I need room for several batteries, a long motor, and big esc. The ideal platform for going fast on-road is 1/10 scale most are challenged with weak differentials, small bearings and overall weak parts. This is why most people end up running 1/8 scale cars for speed. I have done 1/8 and want to explore 1/10 further due to its aerodynamics benefits. I ended up choosing the redheaded step child vehicle that gets hated on due to low price and brand name stigmas. The RedCat Lightning STK happens to have a nice quality metal diff that is used on some of their other off-road models. They also have a large product offering of aluminum parts like a diff case which is very useful under heavy torque loads. Wayne Peeples (look him up on YouTube) currently has one that has hit 150mph (maybe more since I last checked).

Factory chassis with aluminum upgrades:
118873



Aluminum parts:
118874


I have since stripped them of their anodization and starting on polishing to a chrome look.

118875


Adding power to an RC car is pretty easy. Making the car stay straight down the road is likely the hardest part. Aerodynamics are the largest factor limiting an car from going faster. Without getting very technical on the math involved you want the car to be slippery and the smallest it can be to reduce drag force on the car. At the same time you have to manage down-force on the front and rear with some level of balance.
Taking an out of the box RTR car over 70mph is quite the experience. Buggies can get up around 100mph pretty easy with big motors and proper tires (foams or GRP rubber belted tires). Typically from there people turn to Delta Plastics for a speed run (thick) aerodynamic car body. Getting in the 110-125 range is quite the achievement. Only a select few have been in the 130-170 range with modified RTR cars. There are such a small number of persons over 170mph than you can count them on one hand, and only 1 over 200mph. This is no small challenge, many try and fail miserably! Crashes at these speeds often cost hundreds of dollars. Finding a smooth flat road with little to no obstructions along with no traffic is much like finding an unicorn. I will hope to run my car on a airport runway or similar location that is "perfect". It is a sad build in that tons of work will go into it with little actual drive time. Good thing I enjoy the build almost more than driving and I have other RCs for general use and bashing.

Now for the fun part. I will not show all my design yet, but the side profile looks pretty darn good!
118876


With that comes an CFD analysis (orange and white is higher speed airflow):

118877


Lots of work to do ahead of me, I am a busy guy with 2 young kids and wife.... so this will be a slow moving project.
It currently needs nearly everything worked on and details figured out.

118878




-Liberty
 
Last edited:
Looking forward to this! Are you cutting the CF parts with cnc or by hand?

I might have access to CNC, but was planning on doing most of the work by hand. I have a pretty decent assortment of tools along with lots of PPE to work with hazardous particles like cutting finished CF.

-Liberty
 
If you have never seen it before, my inspiration is Nic Case who holds the world record for RC cars at 202mph.
His setup was very custom to say the least.
https://www.bigsquidrc.com/200-mph-rc-car-speed-barrier-broken/

Here is the details about my build. I wanted a small aerodynamic footprint much like Nic's car (1/10 scale on-road). I prefer shaft drive over belt drive (Nic used belt). I have built and run many cars over the years but wanted to do a build that is custom. This build will have a stretched chassis (around 2 ft long) as I need room for several batteries, a long motor, and big esc. The ideal platform for going fast on-road is 1/10 scale most are challenged with weak differentials, small bearings and overall weak parts. This is why most people end up running 1/8 scale cars for speed. I have done 1/8 and want to explore 1/10 further due to its aerodynamics benefits. I ended up choosing the redheaded step child vehicle that gets hated on due to low price and brand name stigmas. The RedCat Lightning STK happens to have a nice quality metal diff that is used on some of their other off-road models. They also have a large product offering of aluminum parts like a diff case which is very useful under heavy torque loads. Wayne Peeples (look him up on YouTube) currently has one that has hit 150mph (maybe more since I last checked).

Factory chassis with aluminum upgrades:
View attachment 118873


Aluminum parts:
View attachment 118874

I have since stripped them of their anodization and starting on polishing to a chrome look.

View attachment 118875

Adding power to an RC car is pretty easy. Making the car stay straight down the road is likely the hardest part. Aerodynamics are the largest factor limiting an car from going faster. Without getting very technical on the math involved you want the car to be slippery and the smallest it can be to reduce drag force on the car. At the same time you have to manage down-force on the front and rear with some level of balance.
Taking an out of the box RTR car over 70mph is quite the experience. Buggies can get up around 100mph pretty easy with big motors and proper tires (foams or GRP rubber belted tires). Typically from there people turn to Delta Plastics for a speed run (thick) aerodynamic car body. Getting in the 110-125 range is quite the achievement. Only a select few have been in the 130-170 range with modified RTR cars. There are such a small number of persons over 170mph than you can count them on one hand, and only 1 over 200mph. This is no small challenge, many try and fail miserably! Crashes at these speeds often cost hundreds of dollars. Finding a smooth flat road with little to no obstructions along with no traffic is much like finding an unicorn. I will hope to run my car on a airport runway or similar location that is "perfect". It is a sad build in that tons of work will go into it with little actual drive time. Good thing I enjoy the build almost more than driving and I have other RCs for general use and bashing.

Now for the fun part. I will not show all my design yet, but the side profile looks pretty darn good!
View attachment 118876

With that comes an CFD analysis (orange and white is higher speed airflow):

View attachment 118877

Lots of work to do ahead of me, I am a busy guy with 2 young kids and wife.... so this will be a slow moving project.
It currently needs nearly everything worked on and details figured out.

View attachment 118878



-Liberty
Wow I'm looking forward to this!!!! Goodluck! I'm rooting for u to beat Nic's 202mph record!
 
Wow I'm looking forward to this!!!! Goodluck! I'm rooting for u to beat Nic's 202mph record!

Thanks! That would be pretty amazing if I can. He set the bar high!
Maybe if I can pick up some sponsors that might help some. Nic had quite a few resources, but the hobby was different at that time.

-Liberty
 
Finally finished polishing the aluminum parts. There are many complex curves and inside corners. I regret doing this :dead:

118953
 
After spending some time handling these parts I simply couldn't imagine them handling 10+ hp.
The build will remain mostly the same but is now going to use 1/7 scale Arrma Limitless parts.

This image shows a typical Arrma Kraton center spool and dog bone setup versus a double 168mm Arrma Limitless dog bone setup.

119299


Layout on the carbon chassis (needs to be cut still) Plenty of room for dual battery setup as well as a longer motor.
This motor is the TP4060 which is 97mm long and has TONS of room still.

119300


119301



Ordered some blades for the saw specific for cutting CF, so for now this is it.

-Liberty
 
Chassis is cut and now working on the tedious process of drilling the holes, counter sinking, and some milling for the front and rear diff gear.

Kraton 6s chassis next to the new CF stretched chassis:

119336


Typhon 6s body for size perspective:

119337
 
Small update... nothing too exciting.

Limitless spool built from ordering all the individual parts. Photo comparison to the Hot Racing spool.
(Limitless is beefy with an 8mm shaft)(on the left)

119371


119372


Limitless battery trays installed:

119373
 
Last edited:
Forgot to update this thread.

Center/top brace fab'd

TP Power 4070 motor is in (8s motor) (4070 motor measures 40*107mm)
Castle Mamba XL-X esc

working on soldering connectors and general wiring layout still.

119581


-Liberty
 
Tidy strips servo wire holders installed for a clean (no wires on top look)
Plus a plastic spark plug wire holder for the esc to motor wires to be safely suspended above the center front drive shaft.

119663


Had it out for a first test drive. Every thing went smoothly and drove as expected!

119664


The car is wrapped up and ready for clay sculpting of the body shape.
That is 25 LBS of terracotta plasticine clay directly behind the car.

119665


-Liberty
 
Air dry clay was not a good choice. Had many issues to say the least.
Ended up using some foam to fill in the large cavities getting started.

119687


After having issues with the clay I transitioned to sheet rock joint compound aka mud. It works well for building shapes and can be sanded down easily.

119688


Currently working on ensuring there is enough space around the tires for expansion and steering. This was some exploratory holes to see where the tires are. Not nearly enough room for steering. Currently adding more material on and will repeat the process.

119689
 
Air dry clay was not a good choice. Had many issues to say the least.
Ended up using some foam to fill in the large cavities getting started.

View attachment 119687

After having issues with the clay I transitioned to sheet rock joint compound aka mud. It works well for building shapes and can be sanded down easily.

View attachment 119688

Currently working on ensuring there is enough space around the tires for expansion and steering. This was some exploratory holes to see where the tires are. Not nearly enough room for steering. Currently adding more material on and will repeat the process.

View attachment 119689
looking good! body will be made out of carbon fiber right?
 
looking good! body will be made out of carbon fiber right?
Not 100% sure yet.
I don't believe it adds any benefits other than looks.
For reference CF blocks Radio signals and conducts electricity. Neither are qualities I am thrilled about, although the chassis is already carbon fiber....
 
Not 100% sure yet.
I don't believe it adds any benefits other than looks.
For reference CF blocks Radio signals and conducts electricity. Neither are qualities I am thrilled about, although the chassis is already carbon fiber....
didnt know that, ok then what are you thinking?
 
didnt know that, ok then what are you thinking?
Probably just fiberglass, but I may do a carbon body also. I'll be making a mold to be able to re-create these bodies.
 
Still working on getting the shape as close to parallel on both sides as possible. I purchased a small circular hole bit for the drill to make accurate holes. With measuring calipers I am setting it up to have 10mm clearance above the tire (For expansion and any suspension compression). On the rear tire side 7-10 mm, and the front tire has 20mm on the side for steering purposes (although limited).

This whole process has been far more time consuming than expected, but I do enjoy it and want to make sure it is correct!

119773


I have also started shaping a tail from a piece of balsa wood.

-Liberty
 
That's a serious project. I'll be following this build. Best of luck breaking the record and not the car.
Thanks! I hope so too!!!!!!

Not much progress but I got the shape finalized and sprayed the epoxy primer.
Wet sanded today. This picture is after a rinse. There is a solid coat of water on it so it looks shinny. With the gloss of the water you can really see the shape better.
119821


Next will be mold release wax and the fiberglass mold creation.

-Liberty
 
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