Liberty's "Unlimited" dream speed build

LibertyMKiii

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I have built a few speed machines over the years and learned tons about RC cars, motors, batteries, and ESCs along the way. Each build I ended up selling off because I realized a better setup or simply wanted to try something new.

My physical location has been a frustration on using the speed machines as smooth open roads do not seem to exist around here (Dallas TX area).
My enjoyment in RCs often is the build more than anything, which is likely why I sell them off after completing the build.

A little history on speed vehicles I have built would be:
X-Maxx 8s - 72.5mph on 8s power. (used to be worlds 2nd fastest till 2 weeks ago)
Slash 4x4 - 83 mph on 3s (castle mm2 2200kv setup) Hit 94.5 mph one time on 6s but had a crash in the process. Certainly capable of well into the triple digits given the speeds on 3s.
4 Tec 2.0 around 68mph on 2s (setup was a MMX with TP 4040) also another triple digit machine had I found a road to open it up on 4s.

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/


**** Edit 07/08/2019 this is now a "stretched" Arrma Limitless project using a hand cut carbon fiber chassis, naming it "Unlimited" ***


The current Stage I plan is a large 40mm can motor like the TP Power 4070 run possibly run on 8s with the Castle Mamba XL-X esc, however I may jump straight into a dream setup.
I have a plate of 3mm carbon fiber that I will be cutting to make my own stretched chassis. Still working out details on the dogbone setup for the center of the car.

Like mentioned in the thread title, this will be a slow process.
 
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LibertyMKiii

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Attempting to test/compare CFD data between 2 designs. (very limited FREE resources for CFD simulation)
Not really sure what the outcome will be, but I am very excited with this part of the build :p

Here is one of the possible body designs version 2 if my version 1 does not perform as good as I am expecting. Keeping V1 a secret for now.
(Drawn with Autodesk Fusion 360)

37826

-Liberty
 
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Lazy Bushman

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nice work guys....I wish all you speed runners the best. Not sure I would have the skill to take on a big speed run but I love reading what you guys are doing, looking at the pics and watching any vids(y)(y)
 

LibertyMKiii

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nice work guys....I wish all you speed runners the best. Not sure I would have the skill to take on a big speed run but I love reading what you guys are doing, looking at the pics and watching any vids(y)(y)
I'm not sure that I have the skills to pilot this thing, time will tell.
 

LibertyMKiii

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I find a gyro helps, once you get it dialed in.
Really think so? (honestly interested in any thing that might help) I have a few of them.
Seems like they do not kick in or do anything until the car has some significant angle differing from the direction of travel. From my experience above 80mph once a car is sideways it is game over. The car takes flight and does more flips than the Olympics.

My thoughts are they are better suited for off-road use. My cars typically drive very straight if my alignments are good and throttle application is smooth. I am getting a bit shaky as I get older...


CFD images from design V2. Identifies a few areas that can be improved (orange), which had mostly to do with my laziness during the drawing. Testing at 67 meters per second (150mph)
Yes that means that 200mph is nearly a football field per second. CRAZY!

38109

38110
38111

-Liberty
 
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Notorious J

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Really think so? (honestly interested in any thing that might help) I have a few of them.
Seems like they do not kick in or do anything until the car has some significant angle differing from the direction of travel. From my experience above 80mph once a car is sideways it is game over. The car takes flight and does more flips than the Olympics.

My thoughts are they are better suited for off-road use. My cars typically drive very straight if my alignments are good and throttle application is smooth. I am getting a bit shaky as I get older...


CFD images from design V2. Identifies a few areas that can be improved (orange), which had mostly to do with my laziness during the drawing. Testing at 67 meters per second (150mph)
Yes that means that 200mph is nearly a football field per second. CRAZY!

View attachment 38109

View attachment 38110
View attachment 38111

-Liberty
What happened to the rc toy talk forum I was watching before? If I knew there was going to be a physics test, I would have studied (but still failed). Love the extremes that you and all the speed runners are going to. It's becoming some of the most interesting reading on the forum. Good luck to you all in breaking those ridiculously high speed barriers that you keep setting for yourselves (y)💪🏎🏁
 

LibertyMKiii

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V1 design is running through CFD analysis currently. (takes about 2 days)
Really digging this one! I won't show all angles that would give away the secrets, but it should be pretty amazing.

The shark fin will house the antenna, which I am in the process of revising to a better shape (less drag). Any sort of length above ground is helpful for reception. Also doubles as a rudder (yaw control) to help keep it traveling straight.

38159
 
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LibertyMKiii

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The CFD software I have used so far is decent showing air flows, but that is about the extent of what it can do. I was looking for data on downforce distribution. Too much force in the rear could cause the front to lift etc... I spoke with a few companies about trial software and that appears to not be an option at this time. Autodesk CFD for example is a subscription for 1 year at $10k. Consultation companies charge around $2-4k. Wind tunnel time is outrageous.

SO it looks like I may build a scale wind tunnel in the garage with 4 sensing pads (1 for each wheel) to measure downforce, plus a 5th sensor in the rear measuring drag force. Based on some calculations it appears I can get wind speeds up around the 120-150mph range through a small test area. This may be my summer project.

Also it may provide some side money providing test simulations for other test projects at some to be determined fee.

-Liberty
 

LibertyMKiii

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For the other speed guys here is a comparison of the GRP (3.76") vs BSR (4.151")
39124

BSR next to a Kraton tire:
39125
 

martysmith223

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a long time ago they made a couple race cars with really strong fans that stuck the car to the ground and expelled the air out the rear of the car witch made a low pressure area... two of the cars was banned from racing that I know of but I'm wondering if or how this could contribute to an rc build...
just throwing some crazy ideas at ya lol
 

LibertyMKiii

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Yes I have spent the last few years researching automotive aerodynamics as well as airfoil concepts. I had given the fan idea some serious consideration (the sucker car), but decided to go another route. My current design will be sucking the car to the ground using some "ground effect" theories. Collin Chapman's ideas in the early years of F1 were highly innovative with sliding side skirts creating a sealed low pressure zone under the car. There are many different ground effect concepts used in F1 (they are limited by rules I am not). The method I am going with (not the skirt method) will reduce my aerodynamic frontal area by 1/3, provide good down force, and looks killer too so it was a win/win scenario. Having no driver inside the car allows car design/shape that automotive engineers dream of.

All will be revealed later this summer once I get to the steps of building the body.

I have some ABEC-7 ceramic bearings on the way. So that I can re-assemble everything.

-Liberty
 
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martysmith223

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I just seen how deep / serious your into it lol.. had to see if you had at least given it some thought not many people know of the concept .. Cant wait to see how this turns out I'm rooting for ya and hope to see some big numbers in the near future
 
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