I get this question a bunch....

[nitroracer911]

People ask how fast my stadium truck goes and I say probably around 40 mph.

Then they ask... well to scale what would that be in a real car?

Since it's a 1/8th scale... does that mean multiply 40mph x 8 (320 mph)????

Or did I just make the most stupid assumption ever on this forum?

- a little help please :confused:

[Lost Racer]

First of all, most stadium trucks I've seen are 1/10th scale. I guess it just depends on the model? I don't have answer on how to find your speed per scale, but if you have a question don't think of it as being stupid(just uninformed :D ) As far as speed goes, it all pertains to your gearing and motor/engine.
Good luck

[ 07-17-2001: Message edited by: Lost Racer ]

[XXXER]

That is right, not about the stupid assumption, but "scale speed", it is 320 Mph. Because it is 1/8 scale, or, for every 1 unit of your car, multiply it by 8, and that is full scale.

so, you are right.

[ammoace]

Let me get this straight using the example above.
The "actual" speed of this truck is 40mph and the "scale" speed is 320mph? So that means my pan car is 1/10th scale and does an actual of 50mph making the scale speed 500mph?
Jerry

[HauntedMyst]

Yes. There is some odd variable in the equation that throws it off 20 mph or so but thats a safe easy way to put it.

[primuswoostinkinhoo]

the way i see it scale mph would work like this, u take a mile and divide it by the scale of your car?(1/8 divide how many ft in a mile by 8) then mesure that out and see how long it takes your car to do that and figure out mph see the way u are doing it u only scale down the car not the mile which isnt correct i may have made no sense cause its 1am but i tryed and being in alot of physics classes i hope im right

[losifreak2004]

What? that is the funniest thing I have ever heard!!!!! Next time, try getting some sleep!!!!!

A 1/10 car or truck is 10 times smaller than a full size car, hence 1/10. So for every one full size MPH, it is ten scale miles an hour, it is as simple as that.

[DerekB]

In actuality there is no such thing as "Scale Speed". If something goes 40mph is goes 40mph regardless of scale. Size and speed are two different things.

[nitroracer911]

well... think about this then.

If you were to measure of a quarter mile for a 1/8th scale car it would not be a quarter mile. It would be 1/8th of a quarter mile.

Then take a hopped up car (1/8th scale of course) and race it and time it in that "scaled quarter mile". Then take that time and compare it to a regular sized car racing a real quarter mile. Then you would find out that in reality... in the scaled world of 1/8th (or any other RC car) the small RC was really MOVING FAST.... I mean... REALLY FAST!!!

RIGHT!!!

[DerekB]

Measurements can be scaled. If you scale speed then you would have to scale time....get it there is no scale time. MPH is MPH no matter what scale! :eek: :p

[nitroracer911]

Oh My Gosh!!! My Brain Hurts!!!

[oso]

Derek is right,it has no sense to scale speed, 40mph are the same for a scale truck than for any other thing moving at 40mph. The idea of using scales is only to compare the scale model to the real car (if there is a real)

;) :rolleyes:

[ammoace]

See, that is why I was asking for someone to clear things up. But now I have to go tell everyone that my car isn't going just shy of Mach. :(
Jerry

[DerekB]

Sorry Jerry!

[wjj]

you can scale time just like you can scale distance and size, they are just math equations. you probly could go to any university and find a math professor who could give you the equations. i beleive its just scaling all three things down by 1/10.

[tapesorcdz]

HAHAHAHA...that's hella funny. Scaled speed is a stupid calculation. Doesn't make any sense. What goes 40mph is REALLY going 40mph...trust me. Scaling it like that does not work.

[combones]

If my car was ten times bigger, it would do 400 mph.
http://www.plauder-smilies.com/rough/jesse6.gif

[DerekB]

wjj, If you scale all three you are back to the right speed. Again no such thing as "scale speed". Your car does what it does. If I were 10 times bigger I would probably be 10 times slower.

Derek

[bubblejunky]

derekb. Just kidding with that remark silly. If my car was 10 times bigger, the battery would be the size of a redwood log with tremendous weight. But my car still will go 400 mph. :D
dcommerce=combones @ work ;)

[Josh00]

I think saying how fast a car Is going to scale is dumb...If your cars goes 50 thats what poeple wanna know not that your car is going 500 to scale... but i think the To scale thing is to say If your 1/10 car is going 50mph then a car 1/1 size is moving the same body units per second as the 1/10 car would be going 500mph - Josh

[Grant Tokumi]

Sorry, this one is too interesting, and misleading (in my opinion) too much to pass up. To answer the original question, you car is going a scale speed of 40 mph, so at 8th scale, that does mean the full scale speed of your model is indeed 40 x 8 = 320 mph. JerryL, your car is going just shy of mach, scale mach that is :).

There is such thing as scale speed. You see it in engineering all the time. Scale models to test real life things. I saw on discovery where the Army Corps of Engineers created a "scale model" of LA County and its flood control facilities to test storm events. Now if the conclusion stated above where "speed is speed no matter what scale" is correct, flood waters in the scale model going 1 mph would be going 1 mph in real life, and would be a catastrophic assumption to make. If its a 1/30 scale model, the 1 mph model flood waters would be going 30 mph in real life.

[BlackWolf]

The whole concept of scaling time has got me confused. Is it linear, or is there some variable in there that will make it change depending on scale?

[wjj]

gran tokumi, i thought there was such a thing as scale speed, i just relised that the special effects industry use that for their models. they also use scaled time by slowing down the cameras to make it realistic.

[Grant Tokumi]

Blackwolf,
I was thinking the exact same thing after I posted my response. I am confident that scale "speed" is a linear relationship. The time unit is just "seconds" or "hour". 10th scale car going 40 mph car is going 400 mph at full scale.

However, throw acceleration into the picture, and I'm not so sure "acceleration" is also linear. With the time unit being the suspect. Time unit in acceleration is "seconds squared" or "hour squared". I have a feeling your 10th scale rc car accelerating at 1 ft/sec^2 will not be accelerating at 10 ft/sec^2 at full scale.

[ammoace]

But all of this is only possible on the third Friday of the fifth month during a leap year on a cloudy day with a 5 knot cross wind at 1000ft above sea level when the moon is full and a butterfly flaps its wings in North Dakota.
:p :D :D :D :D :D :p

Jerry

[cck]

40 MPH in a 1/8th scale rc car is equal to 320 MPH in actual sized car. But we have to know, that our rc motor need to rotate at least 40000+ rpm in order to achieve that kind of speed. In fact in our actual life no car's engine can rotate at that kind of high rpm. Unless you want to break the world record by using the turbine engine. With special engineering and design. i.e super ultra high performance tires, suspensions, and much more. And some kinds of natural restriction.
Our world record of the car's speed was 700+ MPH.

[BlackWolf]

Grant T:

i think the variable is based on the cars speed relative to the speed of light.

[DerekB]

Time cannot be scaled! Your car is going 40 mph and that's it! When you scale LA County time is NOT scaled. Really think about it if you still dis agree. Time doesn't change. No matter what camera trick or model you make. If you technically want to scale every thing (including time) then it will come out to the same speed. 1/10-scale 1/10 time=1/10 the speed. Simple math says you can remove the 1/10 from each side of the equation leaving you with the same. No such thing as scale speed.

[Josh00]

I agree theres no scale speed... 40mph is 40mph wether your car is 18 inches long or 15 feet long.... I dont know if anyone saw what I wrote: "I think the To scale thing is to say If your 1/10 car is going 50mph then a car 1/1 size is moving the same body units per second as the 1/10 car would be going 500mph" I think that explains it pretty well...-Josh

[SteveP]

The concept of scale speed, at least with respect to RC cars, is one that was invented by the toy-grade cars makers. They want to make their 6 mph car sound impressive, so it's advertised as having a scale speed of 60 mph. The premise is, if all other things remain the same, the 1/10 toy car scaled up to full size would travel 10 times faster. The horrible flaw and deception in this concept is, NOTHING stays the same when you scale a car up or down that much. It's rediculous and illogical at best, and it shouldn't EVER be used. Do you think if you made a 110 mph Honda Civic ten times it's normal size, it would go 1100 mph?! Absolutely not. That's why you'll never see something like "700 mph R/C car" (scale speed in small type) on the cover of our magazines. We don't live in a 1/10-scale world, so it' foolih to talk about speeds or anything else in scale terms. If it goes, 40 mph, then just say it goes 40 mph.

Grant, even the example of the flood control isn't proper. You can't scale the properties of the water, surface friction, and the many other vairables that can't scale down with your model. It's valuable information to know where the water is going to flow in a flood situation, but using raw data derived from a scale model to determine drainage and flow rates would be the catastrophic mistake. It's impossible to make a direct translation based on scale.

Take the example of making a real car ten times larger. If you only double the size of the hole the car is punching through the air (forget going ten times larger), the aerodynamic resistance is cubed. If you only double the speed of the car, the power required to achieve that speed is cubed. The list goes on and on. There are so many factors that can't be directly scaled. Derek is correct. There is no such thing as scale speed - not in a literal or remotely accurate sense.

[ 07-21-2001: Message edited by: SteveP ]

[Grant Tokumi]

I can't believe I have to go against what Steve Pond has to say. :). hahaha. No, I take that back. I agree with your points Steve, all except the last one. I think there is such a thing as scaled speed.

Lets say you want to build a model of the city to observe bus/mass transit routes, or even traffic light timing, etc. You build a replica of the city with the roads and tracks. You also make little scale cars, buses and trains, etc. How fast should those cars/trains be moving in the model? The answer is to make it go at the "scale speed". If real train moves 30 mph and its a 1/3000 scale model, the model train should move at 30/3000 or 0.01 mph in the model which is around .17 inches a second. And if some kid comes over to your model with a little toy plane and goes over the city at around 3 ft in 1 second, you can tell him, "Hey boy you just flew over my city at Mach 8!! We have rules about that kind of thing!" Anyways thats my definition of scale speed. Those who state "there is no scale speed" might have a different interpretation of the definition of scale speed.

You bring up the point that its a wrong assumption to think you can scale up your rc car 10 times and expect it to go 10 times as fast when you pull the trigger. Absolutely, however, that point is apples and oranges with my point regarding scaled speed. When someone asks me "What is that in full scale speed?", I think of the above example. But if you interpret the question as: Take all the components of this car, scale them up 10 times, how fast would it go when you pull the trigger? Then the answer is totally different. Probably 0 mph. hahaha.

I also understand your point about the LA County models not being proper. Viscosity, frictions factors between water and concrete, etc, would all be different between models and real life. For the point of this discussion, I felt those points were irrelevent and unecessary to show the point that the guys 1/8th scale car going 40 mph would be 320 mph at full scale speed. However, I do want to say that engineers have ways of accounting for such discrepencies between models and real life. They can apply certain known factors to the model to get a closer idea of what happens in real life, and furthermore, engineers usually use models as a way to acquire those factors in the first place. Something is known in real life, lets say elevated water surface elevation at various flow rates due to a turn (super-elevation). They make a model recreating the scenario and note the discrepencies between the model and real life. If they can isolate the discrepencies to a single factor like viscosity (thickness of a liquid; alcohal vs maple syrup), look at what equations, factors, affect super-elevation and accurately acquire an adjusting factor, they can now start a new design with a model, apply those factors to the results, and have a better idea of how high the outer walls need to be in real life to keep the super elevated flows from breaching them.

Slow motion video is an example of "scaled time". 1 ft = 10 ft is analogous to 1 sec = 10 sec. Scaled time can't be replicated in real life like scaled length (scale models) can be, but time can be played back to display a scaled time with the help of video cameras. Derek is wrong! hahahaha.

To get 1:10 ft to 1:1 ft, you multiply by 10. To get 1:10 ft/sec to 1:1 ft/sec, you still multiply by 10, not 10/10. My point questioning scaling time was: To get 1:10 ft/sec^2 to 1:1 ft/sec^2 (acceleration/gravity), can you just multiply by 10? That doesn't sounds right for some reason and its the sec^2 part that makes me question it. But if its still not understood that you can multiply 1:10 ft/sec by 10 to get 1:1 ft/sec, then thats another issue. Either that or I'm not understanding your point on it, which might be why everyone around here is saying "no such thing as scaled speed" while I disagree and show good examples (in my opinion) of such a thing as scaled speed.

[Josh00]

::::CLap hands::::::
wow

[SteveP]

Grant - agreed. I think we're both in the same book, just on different pages. But I think were beating this thing to death. I'm simply trying to make the point that you don't multiply by the scale of the car for "scale" speed in the context of the original question. Yes, you can have "scale" speed in your model example. I'm focusing on the concept of discussing speeds of an RC car in "full-scale" terms.

[ 07-22-2001: Message edited by: SteveP ]

[Grant Tokumi]

Yes, beating to death is a good description of this discussion.

I'm simply trying to make the point that you don't multiply by the scale of the car for "scale" speed in the context of the original question.

This is where I don't understand. I'm also simply trying to say you absolutely can multiply by the scale of the car for "scale" speed in the context of the original question.

Oh well, hows that EMAXX? One piece of awesome engineering I think.

[SteveP]

Forget it....


Back to R/C stuff :D

[DerekB]

Sorry I had to get one last comment in. Time is Time, you can scale everything in the pretend city, but it's still only going .01mph (miles per HOUR) in scale smurf world it could be going 75mph.

I also sort of see your point with the film, but when you film in slow motion the tape is just fed at a higher frame rate. It's not slowing time it's just letting us look at 2-3 times our eyes normal frame rate. I saw an excellant show on the discover channel about frame of time in humans and other animals.

and think about if you scaled your RC car up to full scale just by mutiplying everything by the scale. A 1.2hp Novarossi would have a whooping 12hp. And that would be with one big 1-cylinder two-stroke. That thing ain't going 400mph.

[SteveP]

OK, I get the lat lick... :D

When you "scale" the car in your model city, you're scaling up everything along with it. The speed, length of a city block, etc. It's a true representation of how a real car would travel in relation to its environment when EVERYTHING is shrunk to 1/8 its actual size.

RC cars on the other hand, ARE in their real environment, so it's not accurate to suggest
You can just scale up the speed of an RC car and leave everything else the same.

Quite honestly, it's splitting hairs. Anyone who wants to suggest their car goes 320 miles an hour, I say go for it. Just be prepared for the ribbing.