Venom speed meter

[mouses]

Does anybody rate them as a realistic method of measuring speed

http://www.venom-racing.com

Thanks

[traxxas-dude]

Well, it simply isnt very accurate. It requires the input of a Human, which naturally is prone to making mistakes, and taking measurements less accurate than say 12 satallites in orbit...(GPS).

It uses the measured rollout, specified by the user, and then calculates the speed by using the measurement, gear ratios, and spur gear speed in a formula to find the overall speed. This system doesnt take into consideration tire ballooning as well.

I would say pay the extra 40-50 bux and get a Garmin Extrex GPS system...

[ajg]

It works for me. And yes it is a realistic way of measuring (depending on the car you put it on, and were you put it).

And if your "prone to mistakes", then you should have someone else take measurments for you.

[AceCoolie]

It's much more accurate that GPS.

[DaFF]

Not to bash, but since you enter manually the o.d. of your car tire, your speed measured can only be as good as what you entered.

Say you measure 2.40" od and you tire od is in fact 2.45",

At 100 mph, your tire will spin roughly at 14 000 rpm.

So, that translate into 2 mph over your actual speed.

Believe me, the od of you tire WILL vary way more than 0.05" because:

1- As you have load on your tire, foam or rubber, the contact patch makes it very hard to guess what distance your car will do in one full turn.

2- As your tire wear, the numbers you are reading can be off. Foam does wear very fast indeed.

3- 14 000 rpm means more than 230 rotation per sec. How accurate is this system to count very high rpm ? It's only a magnet going insane in front of a detector. It has his limit and I am sure it's not 100% accurate at those rpm.

4- There is as well tire slip and with the kind of power some will have, there will be a lot of misreading speed problem with this system.

IMHO, there is nothing like a good radar gun.

Even the cheapest one have +/- 1 mph tolerance ... versus maybe +/- 4 mph with the venom.

Not saying the venom system is not good, just stating facts.

The venom is a good entry system to have an idea on how fast your car goes but is in no way as accurate has a radar gun.

BTW, I can not comment on the GPS, as I don't know exactly what is behind it and how accurate it can be on short distance, very high speed pass...

DFF

[mtrsprt]

Forget the Etrex, it's too big. Go with this one.
http://www.garmin.de/Photos/Geko201-db3.jpg

MUCH lighter,also include WASS technology, but WAAS should disabled for speed testing. WAAS is for pinpoint accuracy of location, not moving objects.

I have used both modes on my Geko, and both always show the same speed when I have it in my 1:1 vehicles.

[ajg]

At 100 mph, your tire will spin roughly at 14 000 rpm.

So, that translate into 2 mph over your actual speed.

DFF

Oh no!!! 2 mph off. And radar is +/- 1 mph, man that's a huge difference :rolleyes:

[DaFF]

As written, +/- 2 mph is only the tolerance pertaining to te measurement of the o.d. of the tire.

I evaluated the OVERALL tolerance of the venon speed system to +/-4 mph.

That's +/- 1 mph = 2 mph versus +/-4 mph = 8 mph difference between the two systems.

For me, the Venom is not an ACCURATE way of measuring speed.

Indeed a very good tool to have an idea of the speed of your vehicule.

There is no other tool that does it in this low price range and that's already pretty good, but we should keep it at that...

Note that you can get a basic handhelp radar gun for less than 150$.

DFF

[TMS]

Daff,
I was curious, will the change in the O.D. of your tires at speed affect the distance travelled by your car?

Excerpts from the installation guide of the Venom Speed meter.

INSTALLING THE UNIT.

STEP1- THE MAGNET. Mount the magnet, on a spinning component of the drive line, such as the spur-gear, drive-cup or drive-shaft.

STEP2- THE SENSOR. The sensor must be within 2-3 mm of the magnet when it rotates past and the magnet must pass directly in - line with the sensor.

SET-UP AND CALIBRATION.

STEP2- TAKE SET DISTANCE MEASUREMENT Put the car on the ground next to a ruler. With the magnet aligned with the sensor, roll the car forward until the magnet makes one complete revolution and is again aligned with the sensor. Take note of the distance travelled. This value will be input as the set distance.

I was also thinking that you might be able to test your speed with a reliable radar gun and change the values of the distance travelled to match.

Note: This is an abbreviated version of the instructions, to save space.

[DaFF]

Well, by measuring the lenght your car have traveled on a full revolution of your sensor, it is more accurate than measureing the o.d. of tires, but the change on your tire od STILL affect it.

There is still question about:

- the fact your measure will not be extremly precise ( maybe within 0.05" if that )
- the tire balloning factor
- the fact that at high speed the load on the car is not the same ( more load means more weight on the tire, thus affecting the distance traveled )
- the tire wear factor

In short, tire od variation is still not out of the equation, that's 100% sure.

And on top of this, as said, the fact that this system also have a tolerance on the number of full rotation measured by the sensor.

When you add all that, I still maintain that +/- 4 mph is a good figure of the speed accuracy of this system.

BTW, yes, use of a radar gun to adjust the measured speed of the venom system would help, but I don't know how you can do that in real life because I think the venom record your car instant speed or store your car top speed.

How do you know that when you hit the trigger on your radar gun you are hitting the top speed ? I guess use of a speed trap would be mandatory but it will still be a guess as if the venom recorded your car top speed INSIDE this speed trap.

DFF

[ajg]

- the fact that at high speed the load on the car is not the same ( more load means more weight on the tire, thus affecting the distance traveled )
- the tire wear factor

DFF

If the load affest the distance traveled, then it would affect the speed, so that means nothing.
And your tire won't wear during one 500ft. speed run, and when your tire does wear, you can change the distance of the magnet.

[DaFF]

I am saying that the downward load that apply to the car means change in circumference contact of the tire to the ground, which translate into less speed than what the venon system would read.

So, of course the load applied to the car change the MEASURED speed of the venon system.

If you want to have a system as accurate as possible, you would also need to change your stored distance of travel on the venom memory as your tire wear....

anyway, whatever you'll do or think, the venom IS affected by a number of variable when other speed measuring systems does not.

And that's a proven fact !

DFF

[rcbuddy]

Radar gun Acurate??? go here-->http://news.bbc.co.uk/2/hi/americas/3613715.stm

[RC Jack]

Don't forget....the tires will balloon up, especially on monster trucks, even more as RPM's & speed increases, making the speedometer virtually useless.

[zeldafreak1434]

here is a solution to all of this, if you are a really good driver, have someone drive a real car, and have the rc drive next to it like 10-15 feet away, then you can for sure know the speed of your car, unless the speedometer if off, lol.
-mike

[ajg]

Don't forget....the tires will balloon up, especially on monster trucks, even more as RPM's & speed increases, making the speedometer virtually useless.

And a touring car won't go through mud, must make it useless. :rolleyes: Just don't use it on monster trucks. I use foam tires, and they don't balloon up, even at 90+ mph.

[ThaFlash_LA]

here is a solution to all of this, if you are a really good driver, have someone drive a real car, and have the rc drive next to it like 10-15 feet away, then you can for sure know the speed of your car, unless the speedometer if off, lol.
-mike

Speedometer on my car shows about 2.5mph higher than real speed. To minimize heat affect on tires, just use some extremely hard compound tires...or polyurethane. I think speed trap is the most accurate way to go, radar guns are faulty (easiest speeding tickets to get out of), and the speed meters are screwed if your tires slip.

[DaFF]

If you do 4/5 high speed passes and have a radar gun, you can do a pretty accurate average speed...

DFF

[ThaFlash_LA]

That's assuming you can get 5 runs with equal conditions

[ParrottJ]

Sorry to bring up an old topic here but I have been looking for somthing to clock my speed and this is what I think. The venom on an off road truck will not give you an a true reading due to the excessive tire ballooning. But It would allow you to see if your tuning has made a increase or decrease in speed even if the #s are not true. If you use one the speeds can only be takin with a grain of salt. A radar gun is what would be used for the final say in how fast your car or truck really goes. HAHA hornets nest stired lol

[fdjizm]

i like the venom speed meter, if its true that its not too accurate, it still cant be so way off that ur not even in the ballpark, its is accurate in itself thought, example.. i richen my car up, record my top speed from the meter, leane my car and record the top speed for my meter, the meter is not going to be wrong against it self so to me its a great way of tuning my car and seeing what setting changed my speed, which is a great tool to have on a car.. so what if its maybe -/+ 5mph.. as long as your in the ballpark u know what your car is capable of...

[k_sw31]

In my opinion, getting a small gps like the Garmin gecko will be your best bet for the best accuracy.

It will record data including your highest top speed, as well as average speed, etc.

Handheld GPS's record speed to plus or minus .1 mph accuracy, making it for more accurate and reliable than the venom thing and cheap radar guns.