Yet another idea.

[TT-01 Mamba]

So my rocket or jet powered cars are not allowed and my spring powered car thread has been spammed by notwalkinblind.
But i've found out that you need powerful motors and high RPMs to stand a chance.
Someone said that you need about 5-10 hp.
So for power and speed can you use twin lehner 3080-5turn motors?


3080 Series
Specifications
weight - 1.800gr
shaft - 10 mm
watt - 10000
volts - 6 - 60


5 turn - 1177 RPM's per volt
6 turn - 981 RPM's per volt
7 turn - 841 RPM's per volt
8 turn - 736 RPM's per volt
9 turn - 654 RPM's per volt
10 turn - 589 RPM's per volt
11 turn - 535 RPM's per volt
12 turn - 490 RPM's per volt
13 turn - 453 RPM's per volt
14 turn - 420 RPM's per volt
15 turn - 393 RPM's per volt


Unfortunately these are expensive at $740 a throw. not to mention the beastly speed controllers and lipos needed. But put two of those in a dragster and you might be going somewhere.

Can anyone tell me if this would work?

[ajlovering12345]

These motors are 15HP so you wouldnt need 2. One will be a bit too powerfull. B4Maz has the best idea with the motor driving the rear wheels directly, you cant get a more efficient drive train.

Cheers

[Mod Man]

Yes, that would be more than enough power. My car is 4.5hp and is overpowered (for a 90 ounce car). There is such a thing as too much power for a given application. Generally speaking, it is difficult to put too much power in an RC car sue to space constraints, though.

I would say that a decent power system that would be competitive (motor, ESC, and lipo pack) would be in the $800 range (maybe $1000 at most). That $800 to $1000 would buy 4 to 5 hp.

I am also looking into a slipper clutch for my car to ease the explosive hit if power. :D

Matt

[TT-01 Mamba]

Ok thanks for the reply. I thought you guys were looking for insane power and speed then gear it way down like every 250rpm you go a mile an hour or something like that.
So if people are using about 5hp and are getting 150mph, is the only thing stopping people going faster the money?

[Mod Man]

Aerodynamics, distance to get the car to wind out, and radio range.

The biggest issue seems to be aerodynamics. That is a huge challenge.

Matt

[TT-01 Mamba]

Ahh so if people can get the aerodynamics right they can go as fast as they want?
For distance you could use an oval track which would solve radio range as well.

So why don't people use the design of something that goes in a straight line, has a limited amount of track and needs good accelleration. Like a dragster? but make the wheels alot thinner to reduce drag

[Mod Man]

You are really thinking well!

Yes, dragsters have much potential. One problem is that a typical dragster is setup for 1.5 second runs. The power system is not meant to handle 5 seconds. I know that sounds strange, but it is something to consider.

Dragsters have very small frontal area. So, they are good for high speed in that respect. However, they are not meant for long distances. They are designed for 132 feet. Getting the aerodynamics right for a 1/2 mile run is another story. However, you are on the right track.

Basically, pump 3 to 4hp into a car and do ALOT of aero testing and ratio testing you will break 100 if you are willing to do the testing neccessary. :)

Matt

[trailranger]

Why not run my secret prototype.

The principle would be to design a bolink legend chassis that could seat 20cells in a row. At the end would be the trailing arm like on a bike that houses the motor pod( similar to bolink pod design) Instead of having two rear tires, there would be one centerly mounted tire (3" ~ 4" dia). A 8mm wide belt would connect the wheel axle to the motor.

The front setup would be the same as bolink, but the tires would be replaced with larger O-Ring tires. The steering knuckle would be aerodynamicly smoothed. The bodly would be designed to only cover the ladder frame chassis, not the wheels. The body should be wedged shaped for downforce but also come to a pointed tail to provide a "TearDrop" shape.
A vertical leaxn rear stablizer could be used, and small lexan vertical frontal stablizers could be made into the wheel knuckles....(IE frontal rudders)

In the end would be a 35" long legend like chassis that only has 3 wheels, and should provide the most stable accelleration and best aerodynamics besides another "long shot" chassis design with the wheels enclosed.

NASA did high speed rail testing with with steel glides, so maybe the front wheels could be replaced with piano wire glides.

(Long story why I'm not building it, in short I have cancer)

[ajlovering12345]

There are a few basic principles that you need to stick to when designing a high speed RC car.

1. Frontal area as low as possible

2. Long chasis for stability and moves the CofG forward to help flipping

3. Weight or downforce required to stop wheelspin at high frontal loads

4. Needs to accelerate fast as you cant see the car from 1/2 mile away. 1/4 mile is just about the limit. Also the radio gear range is about 1/4 mile.

5. This means the car has a good power to weight ratio.

This year and maybe next we will see fast accelerating cars and top speeds of maybe 170 mph at most but we have started something now and there will be people looking at solving the sight and radio range problem as this is the limiting factor for top speed.

If you can solve these problems with in car cameras and 5 mile radio ranges you can see top speeds of 250-300mph.

These cars are going to need budgets in the tens of thousands of dollars so sponsorship will be a factor. Maybe universities can take on the project.

[Mod Man]

To be honest, any speed beyond 90mph is truely fast. 100 is impressive to say the least. 110 is a feat that requires ALOT of testing and correct component matching. 120 is amazing!

I honestly think we are fast approaching the limits of this hobby with the constraints mentioned (distance being one major constraint).

It is incredible to see a small "Toy" blow by at 100+mph. I have never gotten used to it, though I have run mine many dozens of times.

I would not be surprised to see 150 to 160 mph achieved by someone this year. However, that really seems to be the limit considering the constraints we are working with.

Matt

[ajlovering12345]

If you want to see how fast you have to make your car go visit the drag the local drag strip and stand at the finish line. When you see a drag car blast by at 170 you can get some idea of what is needed to get an RC car to that speed.

I raced a normal 1/8th car against a 900cc motor bike and blew it away up to 60mph but then it was like hitting a brick wall. You need to maintain that acceleration for 11 seconds. Building the car is one thing you then have to learn how to controll the power and lay it down smoothly. I might try turning the servo speed down to 3% so the power doesnt spin the wheels.

Cheers

[TT-01 Mamba]

Ok thanks for all of your replies.
So for a chassis which has slightly longer running time than a dragster yet goes high speeds, use a Formula 1 racing car. You make a hybrid of a Formula 1 racing car and a dragster?
To make the steering aerodynamic and not just tubes of titanium house them inside upside down wings.
But if you are going 170mph you might want to consider a parachute to slow the thing down.

[fasterthanspeed]

But at this scale, a small gust of wind can and will pull it sideways.

[TT-01 Mamba]

I got another idea lol.

The world land speed record is something like mach9

They did this with a rocket car inside a tube of helium. Helium is lighter than air so is easier to push throught. Would this help go a couple mph faster?

[fasterthanspeed]

Where are we gonna get a 1/4 mile of helium?

[TT-01 Mamba]

I dunno lol.
IT was the military who went something like mach9 in a tube of helium 3 miles long. The rigg was run on tracks and incinerated the tube behind it.

I think it might be mach 3 with a tube of helium 9 miles long I'm not sure lol.

[Mod Man]

It was mach9. I believe it was something on the order of 6000+ mph. :D

Matt

[ajlovering12345]

It was to test a ballistic missle slamming into a hardened bunker, there was a discovery channel special on it.

Helium tube wouldnt work for me as I need oxygen for my engines but it would help the electric boys.

Why not go to switzeland and ask CERN if you can borrow their particle acceleration tube. Its a tube 3 ft dia and runs in a circle 5 miles diameter. It containes one of the purest vaccumes in the world. That should help with the aerodynamic drag!

I dont know if LiPO cells will stand 0 pressure though.... Maybe not... Next idea!

Cheers

[ajlovering12345]

Ok if your looking into weird idea here's another one.

We are currently moving at 65,600 Miles per hour around the sun and the planet is spinning at 1,125 miles per hr so at some point the land is traveling at around 68,000 miles per hr. All you have to do is figure out how to stop yourself moving relative to the sun and Bingo!!


Oh wait that means you will start to fall towards the sun at an alarming rate. Not good Modman already has problems with motors overheating

LOL....

[TT-01 Mamba]

If you can't use helium use hydrogen, that would provide good fuel for your truck :)

During my summer holidays i might be making a rc drag car out of aluminium tubing and carbon fibre. Anyone want to buy it and put a massive engine/motor in it and smash 160mph? It will be about 1 meter long and can hold 24 lipo and two massive motors :D
But this might all be wishful thinking.

[trailranger]

I got another idea lol.

The world land speed record is something like mach9

They did this with a rocket car inside a tube of helium. Helium is lighter than air so is easier to push throught. Would this help go a couple mph faster?

And no wheels....just steel glides

[TT-01 Mamba]

Yeah, At first they used something else but they melted with all of the friction.

[NotWalkinBlind]

TT-01 Mambo, I didn't spam your "really strong springs" thread, you little weasel... I see you gave it up... I guess it wasn't such a good or usable idea, huh?

:D

Okay, now with the helium tube. First of all, no one here could afford a long tube of helium... second of all it would be almost impossible to drive through it... thirdly, the organizers wouldn't permit it unless everyone was permitted to use it.

What's next... you wanna suggest that someone who runs their electric car on the moon would probably go faster? :D :D :D

Think about it, dude... this forum isn't for wild, far out ideas that no one can afford or make work (like the "really strong springs" kicking in at the last 20-50 meters).

But if you think it is, by all means, keep thinking up impossible stuff.

[balang_479]

i think on board camera driving is the key to record breaking.... some people have the money to put into this, so power, and probably aerodymanics are not such much of a problem but you cant buy radio range or physical eye sight...

Buying a long distance radio and mounting a on board camera like ajlovering said could be break through... although it would mean, the richest person wins. But if people are looking to expand the limits i think this is the way to go too.

[Mod Man]

What I love about this hobby is the fact that it is so early in the game. I think we have just scratched the surface of this hobby from a power and aerodynamincs standpoint. But, again, distance and line of sight are big issues.

I just got my car totally finished (every detail). According to my Eagle Tree, the car accellerates at over 2.5 Gs. I bring this up because it is important that we focuss, not only on top speed, but getting up to speed as well. We need to put more than just a passing emphasis on accelleration. Also, I have found that I can get onto the throttle about 2 to 3 seconds sooner running a steering gyro than without.

Anyway, not trying to hijack or sidetrack this thread. I just wanted to illustrate some other things to think about. :)

Matt

[trailranger]

http://a229.ac-images.myspacecdn.com/images01/1/l_f3fc0e0fee1313371a0dfd7f368acee4.jpg

The car never left prototype, but the idea was to use Lipo cells in with 7.4V pack in the front, 14.8 in the middle and 22.2 volt in the rear. The car would be at 39.5" long when finally built with the main body having an average width of 2 3/4" wide and 4" tall. Add in the out rigger wheels and those average 1/4" x 3 1/2" each. The 3mm graphite plate and steering knuckles for the outriggers would add some too.

The car has a rear trailing arm motor pod with twin shocks.

For motor, what ever would get me my 300MPH at 44.4 volts with my massive 3.5" tall by 2" wide tire. Gearing is going to be limited so I opted to use belts that have been teflon coated. I can find machined derlin gears easily so I thought I would have an motor shaft to bellt pully adpator made. And also an adaptor for the 1/4" Axle. The rear wheel would be custom made of aluminum with the axle clamp built into it. (Think a drill collet with a 23mm hex nut to bind down on the axle from both sides of the wheel.

Another feature for the motor pod would be that the axle bearings would be mounted on offeset hub plates like on pan cars with the one exception. the rear of the motor pod is cut open to slide the whole axle, hubs, bearings, pully, and tire into the pod in one shot.

The motor would also slide into place the same way, notice through clamp on motor plate(Novak 4300 sits inside for mach up)


The front wheels would be 6mm wide at the center but milled to 3 mill at the outer edge. I was going to use Nylon for wheels with a 1mm grove in the middle of the rolling edge. The front wheels are completely exposed, so i wanted them thin. Between the wheel and steering kuckle would be a sheet of lexan that extends rearward past the wheels. This will help with directional steering at high speeds.

For the body, well I would like to use lexan. The rear of the car needs a teardrop cowling to bring that air back together. The front will have a slight bullet shape point to it, but the main body will be plain with little curves to maxize the sloped areas for downforce.

Steering will be done with a mini servo and in a setup similar to my Xray T2 which is long ways. There wil be no turnbuckles..just piano wires with a 2-56 thread solderd on the inside of the car. It need to be thin for less drag on the outriggers.

[Mod Man]

Wow.

All I can say is wow. :)

Very cool.

Matt

[TT-01 Mamba]

Man that thing is sweet, You could use it as a drag racer as well. Will the aluminium have any grip? or are you going to use aluminium wheels with rubber tyres?

One general question, With high speed do people use suspension? Because if you hit a large stone without suspension wouldn't the back wheel just fly up and the whole car cartwheel?

[NotWalkinBlind]

You don't have to worry about that... all the top builders put a really strong spring across in front like a cowcatcher on a locomotive... if it comes in contact with a large stone, there's this big BOING noise and the stone flies out of the way.

[Mod Man]

Geeze,

Why are you so rude to this kid? Give him a break. He asked a legit question.

Some cars have suspension and some don't. It is possible that a car can nose over like you mentioned. That is a good observation.

Matt

[PeterV]

NotWalkin, maybe you think you're just having fun with TT-01 but it really seems like you're riding the kid. Enough.

[trailranger]

For the rear wheel it will be an aluminum rim with foam(magneta most likely) to total 3.5" or 4" testing will determin if extra foam is better because of the growth factor or worse due to blowouts.

The front outriggers will have the same pan car suspension for front wheels except that I will use really stiff springs( diff thruster springs from a TC3 or the motor hold down clamp spring also from tc3) Also the outriggers will flex some with the downforce acting like a spring in its self. I may use vibration absorbing matt to deaden the road noise on the out riggers.

The rear motor pod is on a trailing arm pivot(think dirt bike) with dual shocks. I plan on having 5mm of droop and 10mm of compression stroke. Even though the car will bottom out at 7mm stroke it will prevent the dreaded highspeed shock blow out.

I should mention that my frontal area will be less than 0.003m^2 so it should require a lot less power than any of the cars including 1/10 scale dragsters. I my biggest frontal area is the wheel. Everything else just stacks neatly infront of to prevent excess frontal area.

My orignal concept came from wanting to create the most inline car and use outrunner motors for a hub motor. The outrunners looked good but lacked the KV. I then thought of using sevral smaller outrunners with the KV needed to reach my rpm goal. Creating indiviual trailing arms for each of the 4 smaller motors would be more complex than a wwII panzer tank and the torsion suspension for each of the running wheels for the tracks.

[TT-01 Mamba]

Thanks everyone,
Tailranger, i was slightly bored in a physics lesson today so got out my calculator, Just to get that 4inch tyre to go 100mph it will have to spin 8447rpm. Won't the centrifugel force make the tyre explode or just fly off?
also will a lexan body compress when running in high speed and ruin the aerodynamics? wouldn't it be better to use carbonfibre to reduce drag?#

PS I won't be on much this weekend because i got exams tommorow, monday or tuesday.

[balang_479]

It looks amazing.... really original. i hope it runs at the WFRCCC (sP)..

i think TT-01 has a good suggestion... I think lexan is fine but for the back... the nose and the point where the body curves could be made out of carbonfiber and then the rest back in lexan....

I think you should try and run a 1/8 on-road foam at the back, the cars often reach 80mph down the straight and im sure they can withstand alot more, like 150mph...

[trailranger]

Well I know that the high rpm will play a roll in tire growth but here is my reasoning:

Magenta foam, unlike Pink,it is a little more dense on cell structure.

Tires I thought to avoid due to cell structure: PINK, WHITE!!!!, GREY, Platnium.

Tires that I though would withstand the rpm.. Magenta, Orange, Purple!!!, BLACK!!!! BLUE!!! and Doubles of BLUE and Black..


Since foam tires are glue the entire under side, chance of blow outs would be rare. Chance of major chunkng on edges..very possible.

Rubber 1/5 scale tires have made it into the 140mph range and those are just glued beads.

Foam 3.5" drag tires regularly withstand high acceleartions with speeds nearing 100mph. My tires will at most have 15mm thick foam on the 70mm rims.

[trailranger]

The main fusalage will be lexan. The front piece will be leaxan or shaped foam with bondo over it. The whole body closely mounts to the chassis and I even planned on haveing a backer plate behind the downforce generating part of the rear chassis. The rear cowling would either be lexan or shaped foam with bondo over it.