HOW CAN I FIGURE OUT TOP SPEED????

[bullfrog]

Hey guys how can i figure out the top speed of my car??? i know place 2 lines like 10 feet apart but what do i do next?? thanks allot ( BTW im doing this for my canned heat)....lol

[Smitty]

OK I think I know this one. :)
((3600/t)*d)/5280
t = time it took your vehicle to go from point a to point b
d = distance from point a to point b in your case 10 feet.
3600/t = the number of times the distance will accure in a hour,
*d to get the total distance the car will travle in a hour, feet per hour,
and divide by 5280 to get mph.
I hope I've helped :) :) :)

[Smitty]

oh yea, for top speed make sure that you are goin full bore when you hit point a, until you hit point b, to get your top speed.

[bullfrog]

ummm and in english that means ........????? lol thanks but is there a easier way? :confused:

[WhoKnowsWho]

That is the easiest way man! The time it goes the 10 feet is the t value, so do 3600 divided by the time. And then multiple that number by 10. And then that final number, divide by 5280. And that will be your MPH.

[RCFUN2]

Bullfrog, in what part of CA do you live? My hobby shop in camarillo has a radar gun.

[bullfrog]

i live in vallejo :( hye but NOW I GET IT !i just needed to have it with a K.I.S.S. ( keep it simple stupid)

[ 06-06-2001: Message edited by: bullfrog ]

[QUAKE&SHAKE]

I did this with my truck. I lowered the gearing so I wanted to find how fast it went with an 11 tooth clutchbell 16% nitro.
I suggest making the distance between the lines farter apart than 10 feet. Reason is you would have to start & stop the watch too fast if the lines are that close.
My lines were 25 feet apart. I got going full speed and timed like 8 runs

AVG time .495 second
distance 25 feet
25' / .495 sec= 50.50 ft/sec
50.50 x 3600 (seconds per hour)=181,800 ft/hour
181,800' / 5280' (ft in a mile)=34.43 mph.
The easiest way would be to go run take the times you get and post them here. One of us could then do the math for you. I would gladly help. :)
Make sure to give the distance you used too.

[bullfrog]

well im doing it on my cannedheat so if it were 25 feet apart i would be there all day....lol

[Throtl Hapie]

You may want to make a bigger space than 10 feet. At the cars top speed, you'd probably need to have super fast reflexes to workt he stop watch. Do something like 50 or 100 feet.

[PeterV]

How about this: we'll put up a "Top Speed Generator" on the site! Just punch in your car's time through a 50 foot speed trap, hit "enter", and poof--your car's speed is calculated instantly. I'll get right on it.

[Throtl Hapie]

YEY! Thanks, man! :)

[k-thib]

You can figure how fast your car goes by using the easy rc6 program. It tells your car's top speed. You have to know your motor's rpm's. I dont know how acurate it is. The website is http://www.easy-rc.com

[GT burner]

how about this idea Peterv. Instead of imputing the time which may be a little inacurate from human reflex error, a program where you input gear teeth numbers, tranny ratio, tire size, tire growth rate, and engine rpm. This could also work for electric if you know close to what the rpm is. SteveP showcased his knowhow of this stuff in the latest nitro mag. I think its a good idea. To me its way more attractive than actually measuring. What does everyone think? This calculator would be a great addition to the rcca website!!

[bullfrog]

yea PETER that would be cool!

[PeterV]

You're worried that someone might mis-time their car through a speed trap, but you're confident they can accurately gauge tire growth? And as for RPM--how do you know what the motor or engine actually turns under load--especially if you've geared the car to the moon, which will actually slow it down in the real world despite its mathematic speed advantage? Although useful for estimating/predicting top speed, a formula as you describe will not measure actual top speed--only a speed trap will.

As for timing errors in a speed trap, they would be insignificant. Think about it: if your reaction time makes you start the watch .05 seconds after the car enters the speed trap, then you will also be about .05 seconds late in stopping the watch when the car leaves the trap, so in the end, reaction time cancels itself out!

We can include generators for both formulas--a top speed predictor, and a top speed indicator. It'll be fun to "test" different setups with the predictor, but I think everyone will agree: only the speed trap buys you bragging rights!

[QUAKE&SHAKE]

Top Speed Generator would be nice.
My Quake tires increase in size VERY MUCH at top speed. No way of measuring dia. while its going 34mph :)
I think if you time yourself (or someone else) and all those times are consistant then the speed will be as accurate as can be without radar. My times were from .48-.51 I let my wife time and she got .51 so I think its very close.
Isnt this how they use to do on highways. You ever see those white strips going across the road. Werent those for speed traps :)

With using engine rpm, tire growth, gearing and those other things you leave out the drag caused by say someone using bushings not bearings, proper gear mesh, engines tuned properly, surface running on.

TOP SPEED GENERATOR!!

[new2nitro]

somewhere i saw a site that had you put in gear numbers, engine hp, and a bunch of math stuff, you sumbitted it and it figured out your top speed, it said it wasnt exact due to traction an d aerodynamics and stuff like that.

[Jo_bomb17]

[ 06-07-2001: Message edited by: Rustler Hustler ]

[Jo_bomb17]

I dont know how well this would work but, u could have someone drive a car along side of it, and record the speed off the speedomitor!It might be a bit off, but it will give u a basic idea!This is much easier than that formula if you cant figure it out!

[ 06-07-2001: Message edited by: Rustler Hustler ]

[QUAKE&SHAKE]

yeah that works Obi112 :)

using the first one though where you input the tire dia,rpm,gearing. With my tires 6.7" I get 30.08mph
I input 7.5" (guessing what tire dia would be at full speed) and got 33.68.

COOL :)

[broken_parts]

hey Q&S how did u get the gear ratio?
THanks

[QUAKE&SHAKE]

On my quake I have an 11 tooth clutchbell 51 tooth spur gear
take 51 divide it by 11 = 4.6363
then
In the front & rear diffs are ring gear with 50 teeth and a pinion gear with 10 teeth
take 50 divide it by 10 = 5

Now take first ratio 4.6363 and multiply by second ratio 5.

4.6363 x 5 = 23.18

Stock gearing has 14 tooth bell giving an 18.21 ratio
If you dont have a Quake your gearing will be different

(spur gear divided by clutchbell)
times
(ring gear divided by pinion gear)

[ 06-07-2001: Message edited by: QUAKE&SHAKE ]

[broken_parts]

umm i have a e-pede and srt, how would i figure that out?

[Obi112]

JavaScript Speed Calculators (http://www.goodnet.com/~jrmsn/JavaMath.html)

[QUAKE&SHAKE]

I dont know the gear reduction of the pede sorry. You need the gear reduction of the pedes trans and then multiply that by the number you get from dividing your spur gear by the pinion gear.

[broken_parts]

what do u mean by gear redutcion? :confused:

[QUAKE&SHAKE]

The gears inside of the transmission make up what is the gear reduction

I GOT IT

MY sources tell me that the transmission gearing is 2.72 on the E-pede and stock spur is 87 and stock pinion is 18

SO 87 divide by 18 = 4.8333
now take 2.72 times 4.8333 = 13.146
There you go :)

If you have different spur or pinion your ratio will not be the same.

[broken_parts]

thanks very much, but u know whats easier? just use the e-z rc to do that :)
thanks

[servant]

"...but I may be too worried about imminent death to actually hit the stopwatch at the right moment."

LOL :D LOL :D

Hey that javascrip calculator gives a simplifed formula:

mph = .6818*(tracklength/seconds)

it is just the same formula stated earlier, with some of the calculations already done.

And, yes, that would be awesome to have that same calculator on RCCA's page, only make sure that the min. seconds is able to go lower than .5! -serv :)

[TPXslugger13]

loki instead of doing it with chageable laenths just go ten feet and multiply it by 5 or goo 100 and divide by 2....Duh isnt that simple enough???
Or are you just that bad at math? (No offence)

[OvalQueen]

To test the speed of your RC

Measure off a 100ft speed trap.
Then get your rig up too full speed.
Start a stopwatch when it enters the trap and stop it when it exits.
Once you have the time divide 68.18 by the time you ran.

Example, if your rig ran 1.36 sec. then divide 68.18 by that number.
68.18/1.36 = 50.132 or 50mph. :D

[gubbs3]

Easiest way is to go out and find a police speed radar and drive your car by that. I tried it on my bike and got up to 24 mph. However, if you happen to find one on the freeway, leave it allow. Plus don't touch them because they have alarms...don't ask.

[E-MAXX]

This is the easiest way, Buy a bike speedo and attach it on you rc car or truck. Accurate speeds with a little added weight, going to try it right now!

[loki]

Hey TPXslugger...not so good at math when calculator nearby *urgh*. My point was more along the lines of "wouldn't it be handier if...". After all, if we wanted to do post-calculator calculations, why have something online at all? ;)

Loki

[loki]

Hey Bull_Frog, have you tried it yet? Are you gonna post a speed on your CH? Hm, maybe I should go check your other thread...

PeterV, it'd definately be cool to have a speed calculator on the site. It'd be even better if you could have a drop-down list that allows you to select incremental lengths for your speed trap (10', 20', etc.) for those of us with limited space (or canned heats, as the case may be)

But until that happens, I think keeping the formula Smitty posted in mind is pretty dang easy. I mean, c'mon. You measure out a speed trap. You grab a stopwatch and time your RC as it goes through the trap. You do a *basic* multiplication/long division calculation. You get a reasonably accurate top speed number. *simple*. Calculating gear ratios, tire growth, engine RPM's, etc? If you still wanna do it that way, re-read PeterV's follow-up post ;)

This is how I'm gonna try it next time: A friend's got a Vespa w/a sidecar, so Ima gonna jump in the sidecar with the stopwatch and radio, we'll run both the Vespa and the RC10GT up to speed, and blow through a 500ft speed trap a few times (down at a *huge* flat parking lot.) Should be amusing. I'm thinking the longer trap'll make for a more accurate time, but I may be too worried about imminent death to actually hit the stopwatch at the right moment :D :D

Loki

[bullfrog]

yep just got it yesterday its the silver pt cruiser. it clocked in ata whopping 3.0690 mph!!! lol ( mumbles " i gotta lotta work to do ) lol :D