Air cylinder speed

If you have a video camera and know how many FPS it does ...

Nick

Stroboscope. There was a discussion here about zenon flash tubes in some portable device used for this (General Radio?? - guessing here..)- cant remember its name, but it was semi-antique...maybe someone near you has one? (and can fill in the blanks in my fading memory...)

Andrew VK3BFA.

A strobe only works when something is moving in a repetitive manner, eg rotating. The stobe will freeze the motion and the frequency gives the speed. A one shot linear motion is more difficult. Just thought, if you take a long exposure photo by stobe light, you will freeze the piston rod at various times. From this you can work out the speed. A video camera does a similar job but the frame rate is less, 24fps here in UK.

John

That would be 29.97 FPS for an NTSC (US) camera.

Pete C.

I think that should be 25 FPS for PAL. 24 FPS is common for film.

Pete C.

Record the sound, and analyze it on your puter. You should see the start and stop clunks.

Use an oscilloscope or counter. You will need to rig up a switch at the start of the stroke and at the end of the stroke (at the 1/2 stroke point). Calculate speed from elapsed time between switched events. The switches can be mechanical, optical, Hall effect, etc. The switch closure will need to be "debounced" electrically in order to achieve a sharp, clean pulse at closure. You might borrow a pair of switches from a shooters chronograph. I made a pair once from tissue paper insulation between two thin sheets of aluminum foil. Anything piercing the 2 sheets gave a closure - it had to be debounced, of course.

Bob Swinney

Tom Gardner wrote in article ...

My shock absorber dynamometer uses two micro switches to trigger an electronic timer measure the two-inch stroke of its two-inch air cylinder to three decimals.

Using simple math, I can then figure out shock speed in inches-per-second. When it starts its stroke, a micro-switch starts the timer, and when it ends the stroke another micro switch shuts it off.

Both switches are normally closed, but a link from the shaft opens the switches at each end of the stroke.

When both switches are closed, the timer receives electricity and runs. When the cylinder is at either end of its stroke, one switch is open, and there is no current flow.

Later versions of my dyno actually use a $20 Robics (brand name) stopwatch which is wired to two "momentary-on", pushbutton switches - spaced exactly two-inches apart - that simply trigger the start/stop of the stopwatch as a roller passes over each one.

If I wanted to find a simple, inexpensive way to do what you're trying to do, I'd probably consider setting up a means of starting/stopping an electronic stop watch precisely.

milliseconds are not speed.

Read the post again. Oh...yea, 4" in 50-100 ms = speed!

And pie are not square, Iggy. So what's your point?

Bob Sw>> Is there an easy way to measure the speed of a 1" dia. x 4" stroke

Good suggestion Dave. Tom, all you need is a PC, a microphone, and a program such as WINSCOPE which is free.

Why? Are you going to use it in a no load condition? Things ought to change rapidly as you add friction. Either your speed controls don't close all the way or you need to lower the pressure if you want it to go slower.

Pete Stanaitis

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Tom Gardner wrote:

Or, if they're flow controls and not needle valves, they might be installed backwards. Question: You are metering out, rather than in, correct?

dennis in nca

This is at full load, which there isn't much mass that it's moving. I need to know how long the window is so as to time everything else from a min/max point of view. This window will dictate top speed of everything else.

Good!

Strobotac, made by General Radio. A modern version is available.

Most shooter's chronometers are now electro-optical.

Exactly!