Comments Please.

[Granddad Stinky]

I found this during my browsing activities. What do you think?

http://scriptasylum.com/rc_speed/scalespeed.html

[LongRat]

It gives no explanation why scale speed is false in the first place.  I'd like to see the equation behind the calculation.

[Backlash]

They are making a claim that "speed does not scale the same way that a car's physical scale does" but they provide no proof, reason or explanation to support their claim, or how they have made their calculations..

 

[Juggular]

The aim of the site seems to be "let's convert what feels fast in RC, to how it would FEEL in real life."  While I cannot comment on how one should feel about speed, I think it's mildly amusing.  

If a Grasshopper goes 10 mile/hour and it's 1/10th scale, that's 100 miles per hour (if you simply multiply the scale to speed).  That's too fast in real life, while RC Grasshopper is slow.  Instead of 100 mph, the calculator says 31 miles.  The ratio seems to be about 1 : 0.3.  That feels alright, but who's to say what ratio you should use? 

[IBIFTKH]

It would be interesting to know what factors they're taking into account when they're calculating their scale speeds.

I submitted a few values for 1/10th scale speeds and it seems to multiply the actual speed by 3 point something but doesn't offer any explanation. My inner nerd definitely wants to know their reasoning!

It all seems a bit abstract anyway. Is speed actually scale-able? What is scale? We think of a 1/10 scale model as being 1/10 of the size of a real vehicle. But each dimension - height, width and length are all reduced so as we're talking about a 3-dimensional model, the volume (and potentially, mass) of our model is surely 1/10 x 1/10 x 1/10 = 1/1000th scale??!!

Do volume or mass figure in their calculations? Should they?

I don't know, I think my brain just melted, but it would be interesting to know if there's any kind of recognised or agreed formula for this.

[Granddad Stinky]

..... and how do you scale wind resistance and acceleration due to the rate of gravity. (9.81m/s squared)?

[Wooders28]

Says 186mph for my DT03, which tbh, would be scary fast in a dune buggy!! 🤔😁

[Granddad Stinky]

3 minutes ago, Wooders28 said:

Says 186mph for my DT03, which tbh, would be scary fast in a dune buggy!! 🤔😁

There is no setting for throwing off a cliff! 😂🤣😂🤣

[MadInventor]

Sounds like cobblers to me. 

The circumference of a circle (wheel) is calculated by PI* diameter, so if you increase the diameter of the wheel by a factor of 10 you increase the distance travelled by a factor of 10. Therefore if you scaled up a 1/10 vehicle and rotated the axle at the same rpm as the 1/10 model, it would go 10 times as fast. You might need 1000 times the power to get the same rotational speed  due to the increase in volume of the materials but that's irrelevant, scale speed is scale speed.

186mph is not an unrealistic top speed for a full size electric vehicle, just ask Elon Musk

 

[Wooders28]

I don't think you could get a dune buggy to hit 590mph, no matter how many lipo's you strap to the bumper, (be fun to try though,but not as much as a 1:1 tamiya dump truck scale speed! 😂) and a 1/10 scale SR-71 hitting 270mph wouldn't expand an inch due to heat as the full scale travelling at mach 3.5 etc , but , for decades, before computer simulations (still may use them),they used scale models for wind tunnel tests and water tanks for boats.

I take the calculations with a pinch of salt, bit like the wife falling out with me because I said I'd buy one of every tamiya.....if we won the £150m euromillion roll over! 😂

 

[Wooders28]

Having a quick look at Pro fuel drag racing vs 1/10 RC Drag racing, now, the nhra haven't run 1/4 mile (1320ft) in pro fuel for nearly 10yrs, but I think the quickest 1000ft stands at 3.8@337 , this runs 1.1@126 over 132ft! 

 That calculation says 398 for full scale.

Do tamiya make a rail dragster for a speed run? 😎 @Jason1145 

[Supercoolnothing]

@Wooders28 Unfortunately Tamiya don't make a rail dragster (I'm sensing a potential winter project) but traxxas do offer a funny car that looks like it could be a bit of a giggle. 

[Saito2]

I have no idea if the math behind that calculator is right or not, but I kinda agree with it on some level. My stock Monster Beetle does about 15 mph. I've always felt that, even being as small as it is, there was no way it would be going 150 mph if it was full size.

[Wooders28]

4 hours ago, Supercoolnothing said:

traxxas do offer a funny car that looks like it could be a bit of a giggle. 

Have you seen the price of them!?🤥

[Jason1145]

3 hours ago, Wooders28 said:

Have you seen the price of them!?🤥

Traxxas of course they are dear! 

We'll never know the scale speeds calculations because no one ever does it thoroughly taking into account every variable, mainly weight. A 1/10 scale car might be dimensionally 1/10 but it sure weighs a lot less than the true 1/10 weight of an original vehicle.

If my Escort Cosworth 1/10 weighs 2KG I'm sure the 1:1 doesn't weigh 20KG ( that's equivalent to about one of my legs!)

[MadInventor]

6 hours ago, Jason1145 said:

Traxxas of course they are dear! 

We'll never know the scale speeds calculations because no one ever does it thoroughly taking into account every variable, mainly weight. A 1/10 scale car might be dimensionally 1/10 but it sure weighs a lot less than the true 1/10 weight of an original vehicle.

If my Escort Cosworth 1/10 weighs 2KG I'm sure the 1:1 doesn't weigh 20KG ( that's equivalent to about one of my legs!)

No, but you have to multiply weight by 10x10x10 because you are increasing each of the 3 dimensions by a factor of 10, so your 1/10 2kg escort at 1:1 would weigh 2000Kg, which is probably a little on the heavy side. By comparison my 1/10 scale skidder which is made of steel and aluminium weighs in at around 8kg, which is the equivalent of 8000kg for the full size thing, which is probably about right. The War Rig weighs the equivalent of about 200tons full size and has a theoretical top speed of 360Km/h, but scaling up the power of the motor gives about 3000hp 

[Jason1145]

27 minutes ago, MadInventor said:

No, but you have to multiply weight by 10x10x10 because you are increasing each of the 3 dimensions by a factor of 10, so your 1/10 2kg escort at 1:1 would weigh 2000Kg, which is probably a little on the heavy side. By comparison my 1/10 scale skidder which is made of steel and aluminium weighs in at around 8kg, which is the equivalent of 8000kg for the full size thing, which is probably about right. The War Rig weighs the equivalent of about 200tons full size and has a theoretical top speed of 360Km/h, but scaling up the power of the motor gives about 3000hp 

Haha every days a school day, me and maths never really got on well and that continues! Thanks for the lesson

[Prescient]

..

[Munchbox]

I guess the only option is to build a 1:1 Tamiya replica and see if it can hit 300mph or not.

The dt02/03 would be perfect for this with it's simple and rugged design. 

The ESC will be as big as a TV and the motor will be as big as a re****erator. I think the challenge will be finding a steering servo big enough, but maybe we can piggy back 800-900 regular servos instead of one big one. 

We can strap the driver's seat straight onto the gigantic 2s lipo battery in the middle. 

Who has room to paint the full size lexan body at home? We're going to need some massive decals for this thing too. Probably between 80-100 cans of paint.

I'll paint the lettering on the tires.

Seriously though I think speed scales normally regardless of what that site says. 

Now imagine a full size 1:1 Lunchbox going 360 mph.