Venom Speed Meter Installed.

[kwong2001]

Okay, this's how the speed meter works. You have a small magnet and a sensor that's connected to the VSM. What you do is you put the magnet somewhere on a rotating mass like the driveshaft or spur gear. The little unit must be within 1-3mm from the magnet. It counts the rotations through the magnet.

You measure the length it takes to go one revolution with the magnet. Then the VSM translates that into MPH when you're driving.

You have to be kinda creative in installation though. I CA'd the magnet onto the driveshaft and secured it with electrical tape.

Oh yeah, forgive me for the dirty car, my motto is "don't clean it, drive it!"

The last picture shows the carbon fiber that was taken off to clear the magnet.

 

[Paintbug]

i picked one up but havent had time to install it on the savage. so whats the top speed??

 

[kwong2001]

Just installed it tonight. Finished about an hour ago from this post.

I dunno when i'll get a chance to test the speed since it's been wet outside for the past week or two. Whenever it's dry, i'll be testing.

 

[wdavidhicks]

Duct tape?? It looks like electrical tape.... :egad:

If your vehicle is a 2-speed I wouldn't put it on the spur gear.

That looks pretty slick, Kevin. So to calibrate it do you just hit a button and then roll your car over a known distance and then hit another button?

 

[kwong2001]

lol...meant to say electrical tape...it's been changed

To calibrate it, you use a ruler and measure how far it takes for the car to move the magnet one rotation. Then you program that into the VSM.

for example, my car goes 3 inches for every revolution the magnet (which is attached to the driveshaft) goes. So I enter 3 inches into the VSM.

As for the spur gear, I couldn't put it on there if I wanted to since there wasn't any room. But the instructions does show a RTR ntc3 with with magnet on the spur gear. So I guess somehow they made it work.

 

[wdavidhicks]

I would think the longer the distance you could measure off to count rotations, the more accurate it would be.

Is your only calibration option to enter a distance for one rotation of the magnet? I'd roll it ten feet and divide that distance by the number of rotations. Do they allow decimal precision for the distance entry?

If you program in three inches and it's actually only 2-7/8" that means you could get a reading of 60mph when it's actually going only 57-1/2mph.

 

[kwong2001]

Well it goes in incriments of .1 inch.

It's not fully accurate, but it's pretty accurate.

 

[wdavidhicks]

Roll it ten feet and count the rotations. You might find you have 41 magnet revolutions in ten feet. 120 inches / 41 revs = 2.927 inches per rev. If you round down to 2.9 your speedometer reading will be fractionally on the low side of the calibration but you'll be able to say you were going at LEAST as fast as the speedometer indicates.

I'm lookin' at the Maxx right now trying to figure out where I'd put one of those!

 

[kwong2001]

Originally posted by wdavidhicks
I'm lookin' at the Maxx right now trying to figure out where I'd put one of those!

I think especially with monster trucks, you have to get really creative on installation. Probably even going as far as fabricating a bracket of some kind to install it properly.

 

[wdavidhicks]

I'm thinkin' the top of that sheetmetal skid plate would make a fine mount.

 

[kwong2001]

I honestly don't know about having it down below. If you're only gonna use it for top speed runs, then that'd be fine, but any off-roading could seriously damage the unit.

off topic: my starter box's polarities were fuckin backwards! How long has that been going like that? No wonder I was having trouble starting my engines. Had a feeling it was doing that but hadn't investigated it until today!

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I did a brief run in the wet just now.

Two different readings that could be right. One was 35mph, the other was 47 mph.

Keep in mind that I only had about 200ft to do the run and it was wet and I had foams with absolutely no traction. I'm sure once it's dry i'll be able to break 50mph pretty easy.

 

[kwong2001]

54mph...it's official

I didn't have enough room to run it up...it was still accelerating when I had to get on the brakes.

It becomes a lot to handle once it gets past around 50mph. It's like a bullet.

 

[dougc]

Originally posted by kwong2001
54mph...it's official

I didn't have enough room to run it up...it was still accelerating when I had to get on the brakes.

It becomes a lot to handle once it gets past around 50mph. It's like a bullet.

It is sort of sad when you really find out how fast your car goes... I think it is becasue everyone always thinks it goes faster.

 

[nitrohead]

Kwong- That's all? Find a larger area to run it in so it can top out. I was expecting 60 mph out of your ntc-3 you got a novarossi 12 in her. Of course you can always stuff the new novarossi big block 15 in there for your high speed runs.:classic:

 

[kwong2001]

Well I've been trying to think of some good places to run. I need at least 500 ft. to even have a chance at top speed. And it has to be ultra smooth with nothin on the road. No manhole covers or reflectors...nothing.

It's really a lot of requirements. So i'm thinking I need to find a neighborhood that's currently being built with a freshly paved road.

Oh yeah, and it has to be dry, I did the 54mph run when it was still a little wet out.

I think my ntc3 could probably hit about 60mph with the gearing right now. And I might be able to squeeze a few more mph with gearing more to top end.

 

[militarymaxx]

Very cool accessory ! I think if I were going to attach it to a drive shaft, I would look into heatshrink. Most good heatshrink will reduce it's size by 50% when heated. Getting it over one of the shaft's ends and still be small enough to secure the magnet might be difficult. To get more data on your high speed runs, try mounting it to something different. Maybe a wheel ? Compare the new configuration data with what you already have. It would be interesting to see how close the numbers are. Anyways, very nice job man. Good tool to have when making those changes, whether it be a big change like a tuned pipe, or those subtle ones like carb tweaking.

 

[Paintbug]

i mounted mine in the front drive cup on the tranny in my savage.

 

[Razor]

hmm if i sill ran my .21 racer 2 with 23/37 gearing id buy one just to prove to you people my car does 75mph.

 

[nitrohead]

Venom Speed Meter

Kwong - 54 mph is pretty good on a wet surface. What percentage nitro are you burning? How important is this speed run to you? Because if you are serious why don't you bump up the nitro content in your fuel and go for it.:yes:

 

[kwong2001]

I was running 20%. I got 30% but I don't wanna use it on a $250 engine since it'll wear it out faster. Rebuilds for my engine are in the $150 range...not worth it.