Limitless Talbot's fastest RC car project discussion

[LibertyMKiii]

My son used to live in the Springs when he was an intern at the Olympics. I don’t remember seeing many good quality flat roads there, but I’ve only visited for a few days a few times. There are ENDLESS crawling and bashing spots there though.

Oh and I think the most of the Springs is 7000ft and above. An hour drive up to Pikes gets you above 14,000ft.

Yeah I figure in the mountain regions you wont find any flat roads.
I was thinking more on the east side - outside of town. As you head towards Kansas it is just flat as can be!

 

[rotauq]

Hmm, I never realized high humidity lowers the air density(at higher temps). At least one aspect in which my country scores good, as height and temperature are not really helping.

Side note is that air density will also affect downforce

 

[LibertyMKiii]

Hmm, I never realized high humidity lowers the air density(at higher temps). At least one aspect in which my country scores good, as height and temperature are not really helping.

Side note is that air density will also affect downforce


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That is quite interesting about the humidity, however it only seems to have a good difference up around temps above 70c.
I wont go out in temps above 35c (95F)
The values are all very close when at those temps....

 

[jkflow]

So you are basically saying that you should run just before a hurricane hits in Florida with 90F/90% RH and the wind is blowing from the back.
Note that air pressure is way down as well, easily 10000ft height equivalent.

 

[jondilly1974]

So you are basically saying that you should run just before a hurricane hits in Florida with 90F/90% RH and the wind is blowing from the back.
Note that air pressure is way down as well, easily 10000ft height equivalent.

Tailwind?

 

[Sloclone100]

I thought this may be fun to discuss Talbot's Limitless build.

My list of concerns:
1. Having 2 motors that likely don't output the same KV. (This means one set of wheels is going to try and go faster than the other.)
2. Room for ESCs and Batteries.
3. Purchasing a 1mm body.
4.The radio he is using.
5. The lack of experience running over 100mph.

Overall I am glad he is doing this project to cast some light onto the speed run side of the hobby.

Hey buddy,

I've seen a guy use two electric jet engines attached to the Limitless. I did some research and found these engines are not capable of even half the speed of the motor he had onboard. This tells me that the jet engines may actually be slowing down the car as the onboard engine attempts to gain speed.

You are correct that no two electric engines or any engines that are similar will not perform the same. But strap-on two jet engines that are not even capable of the onboard's engine speed sounds ridiculous. You may as well strap a brick onto the chassis.

Any thoughts? -Dave

 

[jkflow]

Are you talking EDF units or truly jet turbines (scale style)?
If you are talking about the video below, yes clearly only done for fun and show, but he states that in the video. All about innovation.

 

[LibertyMKiii]

A friend and I were talking about a true turbine engine.
We calculated the thrust and it would be extremely fast. Problem is the cost of such a project and it wouldn't be a wheel driven car.

It would be like having an airplane that does not take off the ground.... its not really a car unless it is wheel driven.

 

[jkflow]

You can get a turbine with a gear box and not rely on thrust. It's ~ $5k plus ancillaries for another $1-2k.
Obviously they are prone to damage during acrash which hardly ever happens during speedruns

 

[rotauq]

Not driven but thrusted will require a lot of downforce to keep it in control, let alone when it does get out of control.

Running a turbine on a gearbox will have to be huge (or maybe motor assisted) to bring that initial torque. Adding a torque converter would be too inefficient.

 

[jkflow]

Biggest problem will be cooling, you would need a water cooler. They cool themselves a little with their own fuel, but that won't work for long, only at idle.

 

[SrC]

If you take a fueled jet engine. Scale planes. Thrust is very inefficient at low altitude. There are two factors in the equation. Air density is highest approching Sea Level. And Fueled Jet engines work harder to sustain thrust. For the purposes of surface RC's, Higher air density translates to thicker air that areodynamics must cope with. Air friction. I imagine higher altitudes in theory is better. If we lived in a Vacuum , speed swould be higher.

 

[rotauq]

If you take a fueled jet engine. Scale planes. Thrust is very inefficient at low altitude. There are two factors in the equation. Air density is highest approching Sea Level. And Fueled Jet engines work harder to sustain thrust. For the purposes of surface RC's, Higher air density translates to thicker air that areodynamics must cope with. Air friction. I imagine higher altitudes in theory is better. If we lived in a Vacuum , speed swould be higher.

A warp 10 RC spaceship

 

[Sloclone100]

Are you talking EDF units or truly jet turbines (scale style)?
If you are talking about the video below, yes clearly only done for fun and show, but he states that in the video. All about innovation.

As far as innovation, I believe design is more of an issue.

Yeah, it's those. I knew they would be a hindrance to power and speed. As far as innovation, I believe design is more of an issue.
Even as this sport went from 1200Mah/7.2v, to 200+, There will come a time when too much power will not matter. At that point, we will cross the boundaries of physics. Even with the rear wing raised your back wing will give so much downforce, Or the invention of lighter batteries IMO, may further speed but I believe will reach the limits of technology. The cars we run, right now, have a greater 'power-to-weight ratio than an F-16.
Just my pair of Lincolns.

 

[LibertyMKiii]

Yeah, it's those. I knew they would be a hindrance to power and speed. As far as innovation, I believe design is more of an issue.
Even as this sport went from 1200Mah/7.2v, to 200+, There will come a time when too much power will not matter. At that point, we will cross the boundaries of physics. Even with the rear wing raised your back wing will give so much downforce, Or the invention of lighter batteries IMO, may further speed but I believe will reach the limits of technology. The cars we run, right now, have a greater 'power-to-weight ratio than an F-16.
Just my pair of Lincolns.

I believe we are already there. An example like Raz's dual motor car, which has the ability to output in the ballpark of 20-30 horsepower.
The result was either breaking driveshafts, differentials, or if those would hold then there was traction issues.

The only thing stopping these cars from going faster is air resistance/drag. Aerodynamics is the key!

 

[Sloclone100]

I believe we are already there. An example like Raz's dual motor car, which has the ability to output in the ballpark of 20-30 horsepower.
The result was either breaking driveshafts, differentials, or if those would hold then there was traction issues.

The only thing stopping these cars from going faster is air resistance/drag. Aerodynamics is the key!

Very good point. My main message [not accomplished] is that a typical 540 size motor, even running Lipos, had limitations. But these design problems changed with the invention of the brushless motor, and lipo batteries. Of course, the car needs to be at least 1/8 scale to handle the power of 20 sized motors, with some pushing 10 horsepower with a single motor. But, slap on a couple of electric-powered fan jets and it will look cool but no way perform like a standard inboard electric motor - single or double. The first thing that one must be aware of is how a standard "jet" engine works. Air is taken in the front of the engine and its blades (contained in a housing) is pulled through to create thrust at a higher velocity. This is a standard definition of a 'jet'. A jet engine is defined by heating the air inside the engine using combustible fuel, which increases the heat of the air being pulled through the engine, creating a much more powerful exhaust. Aircraft engineers refer to this as "Suck, squeeze, bang, blow". (O.K. stop laughing) The engine sucks in air, squeezes it, mixes it with fuel 'bang' and blows it out the rear 'blow'. It may be possible, in theory, to build a smaller scale jet engine, but it would require a large number of batteries to power a compressor to feed a sufficient amount of air to the intake and then heat up the air need for the thrust that exits the rear. I believe there are no current designs, due mostly to the number of batteries needed. And due to the absence of fuel-heated air, these engines can be thought of as 'two-stage ducted air units". Also, fuel heated air produces about 50 times the power of battery heated air jets.

You're still not in the 'probable' category yet. Either design would have to deal with superheated air (1000 degrees), and the possibility of having much heat near very combustible batteries. There are some companies that are trying to design an (electric and combustion-powered engine) which uses ducted fans, but these are some years away from flight. Lastly, there is a type of design in the works that uses plasma to heat the air. Although some advancement has been made in this type of design, it still would be very expensive and may only work in the confines of space.
So, to scale down any of these designs may be possible but certainly not practical, not using current technology. Plus, most of these designs are focused on real scale airplanes, to reduce greenhouse gas. So the first breakthrough for alternate, nonfuel jet engines for much smaller R/C vehicles and planes may still be a far reach.

I used to work at a company that designed components for civil and military use. If any of my data is found to be dated, please let me know. -Dave

 

[jkflow]

This should count as RC, using a remote

 

[Sloclone100]

This should count as RC, using a remote

This is a full sized go-kart. I've seen a couple of these engines, like XICOY X45 Micro Turbine. As I said, the technology is getting better, but for now, it's impractical for R/C sized vehicles. Nice video though!

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