Alright, so my interest in FIRST started with my interest in remote-controlled cars. (I’m working right now on building the longest, but that’s another thread.)
I picked up a copy of Radio Control Car Action, and on the back page they issued a challenge. Build the world’s fastest R/C car. For the rules (IIRC–I’ll make sure later that I’m not missing anything), anything goes, as long as it’s under two feet long, have some sort of 3D cockpit (something that it looks like a driver could sit in if it were full-size) uses driven wheels for propulsion (sorry, rocket guys), and has an FM radio with a fail-safe. (I’m pretty sure they’d live with an IFI system, even if it wasn’t the best way of doing it.)
It’ll be sometime after 6/1/05 out at Irwindale Speedway.
Now, with all of us fielding robots with four-speed eight-motor shift-on-the-fly gearboxes, you just KNOW that a couple of FIRST teams could whip up a mind-blowing car. The electric world record is 111 mph on 24 cells and a two-turn brushless motor.
yes, thats not sclaed speed. its actual speed… a 10:1 rc car scaled at 60mph is pretty slow i think… not sure this is correct, but around 6mph??
that would be slow.
some rc cars go 70 outta the box…
how hard would it be to control 111mph rc car? i wouldnt even want to try it.
actually, i would, but id probably destroy it…
and rc cars at toys r us and whatever that come out at holidays are definitly NOT fast. get a nitro car… wish i had one…
No, I’ve never had the chance to get my hands on any. Nor do I know how such a conversion would be done–but I would imagine that a motorcycle drag racer would have something to say about this.
Well, that’s the advantage of doing it at Irwindale: they keep that sucker clean!
And yes, that’s straight-up, just-like-you-drove-it-in-your-car 111 mph.
Personally, I don’t think it’d be that hard for FIRST teams to adapt to speed. I mean, we build for torque, since that’s what’s required to move a hundred-pound mobile goal. Change the gearing up, and while it won’t be able to push much, it’ll scream like anything.
Although the charges against the Nikko cars and the like would make for an interesting challenge…world’s fastest Nikko, anyone?
Yes that speed record is actual speed. This hobby is very expensive first off! Today many rc cars are very complex and yet simple pieces of fun! Some RC cars have 3 speed trannies and very small high powered engines.
I would not attempt to use the Mini Innovation First contoller (EDUBot). First off this would be very heavy! Second their is no need to use one! Third if your car crashed at 50 MPH is would no longer exist.
My RC truck (tmaxx) costs $400 bucks for the truck. Not to mention the batteries and chargers another $40. You also need other support equipment.
The fuel alone cost $23 a gallon. Imagine paying that much for it at the pump! yikes!
If you need anything just let me know.
Here is my truck. It goes 40 MPH out of the box. www.traxxas.com
Not enough torque. Need I say more? Actually, I shouldn’t jump to such a conclusion. You never said what size wheels you were using. But assiming you wanted to go 112 mph, you would need a wheel approximately 2" in diameter on the 19670 rpm drill shaft. Now, at stall the wheel would only be able to exert approximately 7.9 lbs of force on the ground. As motor speed goes up, torque goes down. So, I reckon moving at 112 mph (near 19670 rpm), you will have very little torque, certainly not enough to counter the air resistence.
Aside from that, I am fully willing to help with this project in any way possible if anyone will be working on it in the southern california area. While I’ve been fading from the hobby in recent years, I do have many years experience with RC cars and have 9 cars , both nitro and electric and have cutsom built frames before. This sounds like a fun challenge and I’m certainly willing to work with anyone who wishes to enter.
Hmmmm, My last car, (Kyosho Inferno Kani II) was pretty darn quick (~50mph with the OZ 2.5hp engine) but it was actually an off road car with a high stance and only a single speed. IF you wanted a really fast car, here is what one would have to do.
1.First, ditch the IFI control system, it is too big, too short of a range, and not useful for an RC car. Get a PCM radio that can cut your throttle if it gets out of range so you don’t kill the person 3 blocks down the street from you when it goes by in a blur.
4.Take the Automatic 3 speed from the Kyosho Mad Force http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXCGR3&P=0
and send it into a small custom high speed gearbox driving the front or rear wheels, such that the gearing uses the motors on the top end.
5.Tune in the steering servo for extremely dull steering input so that a tiny movement at 100mph doesn’t launch it 30ft off course.
6.Add in a well supported body with some downforce so it doesn’t take off like a jet.
If you can do all that, my guess is it will be pretty fast!!!
Matt you make it sound so easy. It will be quite difficult to make all those components work together but it can indeed be done. As for the horsepower of that engine, I’ve read sever articles claiming that the way manufacturers come up with that rating is different between each company and it is not a uniform system of measurement/testing. Your 6 step plan would make a pretty fast car. How fast? I don’t know. One thing is that nitro engines can not run at WOT for too long or they’ll break the con rod or sieze or blow a gasket or whatnot, not to mention possibly overheat. But it might be possible for just getting to top speed and back down really quick. It would depend on the gearing. Also, the speed and power you can get on them depends largely on several factors such as air temperature and humidity, fuel composition, etc. You would need some really good tires and a body and components because of the forces involved with such high speeds.
Even with all the challenges, I would like to try this.
What does everyone think of a dragster style car with just a really fast electric motor with a pinion, an axle with a spur and wheels, a _______ load of batteries?
Or would a pan car type car be better or would a sedan?
Well, there is a really simple explanation to why you are almost definitley wrong in your reasoning. Unless the drill is much less efficient in (input/output and output/weight), then a direct drive configuration is probably precisely what you are looking for. If a motor, batteries, and chasis can go at 111 mph, then a motor with an output/weight ratio anywhere near the ones used in the 111 mph car would, in at least some configuration, be able to travel at 111 mph also. Using your calculations, we see that to achieve this with just a drill motor and a wheel, we need to actually use larger wheels and therefore less force at the wheel because that is using the free speed which is no where near the peak power output (and therefore a very bad output/weight ratio). Using the formula for drag in a non-compressing fluid:
D=(1/2)CDArV2
we see that the drag force of such a car (assuming it is a sphere with radius 10cm)
= (1/2)(0.5)3.14(0.1 m)2(1.2 kg/m3)*(49.6m/s)^2 = 23.2 N or ~5lb.
The drill at max power is at ~10k rpm therefore requiring about 4" wheels and outputting about 7.9/(2*2) = ~2 lb. (divided by 4 because double size wheels and half stall torque). @#@#@#@#, maybe I should have made those calculations before starting to write this :). Seriously though, I think this result shows that is reasonable to have the drill motor going at 111 mph on direct drive, especially because of the highly overestimate drag (a sphere the size of a basketball?).
I somewhat screwed that up didn’t I? :o Of course you can never get more power out of a motor and gearbox than you can out of just the motor itself. But what I was thinking is that the drill motor wouldn’t have enough power to reach those kinds of speeds. But perhaps it is indeed possible. The RC motors spin at more like 28,000 rpm but the drill motor I believe has more torque.
Anywhoo, we can sit here and engineer this all day but I think untill one of us gets off our chair and starts making it we’ll never know if its possible.
/me rummages through old RC parts
EDIT: /me kicks self for selling carbon fiber pan car chassis I once had.
Haha! Yes! That’s the real engineer attitude! I wonder what sorta power source you can use that can give you such a high power/weight ratio (not energy/weight, lithium would suck in this case). Considering it runs for only a few seconds, maybe even capacitors?
It will be quite difficult to make all those components work together but it can indeed be done. As for the horsepower of that engine, I’ve read sever articles claiming that the way manufacturers come up with that rating is different between each company and it is not a uniform system of measurement/testing. Your 6 step plan would make a pretty fast car. How fast? I don’t know. One thing is that nitro engines can not run at WOT for too long or they’ll break the con rod or sieze or blow a gasket or whatnot, not to mention possibly overheat. But it might be possible for just getting to top speed and back down really quick. It would depend on the gearing. Also, the speed and power you can get on them depends largely on several factors such as air temperature and humidity, fuel composition, etc. You would need some really good tires and a body and components because of the forces involved with such high speeds.