accuracy of vsm

[NooP]

has any one bothered to try to see how accurate these things are? I am a bit skeptical to how accurate they are. I have been looking around the web for a radar gun and I have seen them as cheap as 90 shipped to well over a 1000. Again, an 80 radar gun can be argued at not being accurate aswell, but atleast you can use it on different vehicle. If most of you are like me, you have more than one rc vehicle and I'm sure you would like to be able to test the speeds of all of them. Getting one for all your cars could start to be pricey.

So has anyone put a vsm up to a radar gun to see how accurate they are?

--NooP

 

[El Pirata]

One would think the small size of a radio controlled car/truck would not really be that accurate unless you are getting one of the top of the line radar guns.

 

[NooP]

why not? What does the size of the car have to do with accuracy?

--NooP

 

[Bill Hoskinson]

The VSM is very accurate, however they are only as accurate as the person using it.

They have to be calculated for the vehicle it is being used on. What you have to do is install the magnet in a diff cup, or drive line. You have to push your car or truck far enough for the magnet to make one revolution, and measure how far the car or truck moved.

That distance is your calibration factor # that you enter into the VSM to calibrate it.

Now, where you get into problems.... Is with tire growth. On Monster Trucks like the T Maxx, the tires may be 6" tall when you measure the distance it travels, but at 38mph, they may grow to 7".

This will throw your calculation factor, and your MPH readings off.

I have one on my MGT, and I use Pro Line Grey extra firm inserts in Ofna Ho Bao Tires. They don't grow more than 1/4" at 40mph.

I had a buddy of mine drive past the house the other day in his truck, and set the cruise at 35mph. Once he passed my truck, I pulled out on the road and tried to run him down. Within 200ft, I had to hit the brakes to keep from going up under his truck.

The VSM showed 41 mph on that particular run, so I would say its pretty accurate if you calibrate it propperly.