Keeping with the cautionary note of creeping up on the task, I managed to successfully record some 400psi, 350 fps shots. They all went well, but a few tweaks will be done before the velocity is bumped up.I won't be able to give full documentation until later tonight, but here are pics of the test setup.This is the overall setup.The .25 cal Disco-based gun is strapped into place. It shoots thru the birdhouse muffler. The metal rod above the gun barrel is an alignment bar for the hole thru the birdhouse. If the gun's barrel is parallel to that rod, the pellet should pass thru without hitting anything. Beyond the birdhouse is the chronograph with light bar above it, and then the bullet trap. For this exercise a 6x6x6 open-fronted cardboard box is filled with grocery bags, and placed in front of the normal trap, to catch the fired pellet. To the right side is the trusty laptop with the PC based o-scope program ready to go. It has 2 channels. One channel records the valve stem movement, and the other channel records the pellet/magnet movement past the sensor coils. Here is the pick-up for the valve stem movement. As Rube Goldbergish as it looks, it is about the 20th attempt at a reliable (ha ha) valve stem movement pickup. But, it does work! Sticking out of the window in the side of the air tube is a 1/4" steel rod that is threaded ontothe end of a special valve stem. It travels in unison with the valve stem as a single entity. Sticking out of the top of that valve stem bar is a short length of .050 hex key. The hex key pivots where the little set screw is visible, and the end of the hex key swings an arc across a portion of carbon track from a trim pot. The white bead on the end of the hex key is a teflon ring that helps the wiper maintain a proper pressure ont eh carbon throughout its swing of travel. There is about a 3 to 1 travel increase ratio of the wiper across the carbon track. A 1-1/2 volt battery and a resistors plus the carbon track, make a voltage divider circuit to provide a voltage to the o-scope that is proportional to the travel of the valve stem. There is a torsion spring wound around the hex key pivot point to remove any backlash from the setup. The voltage seems to track well with the movement, although I am sure there is some lag and overshoot at the extremes of travel. But again, it does work.This is the front end of the barrel with the 3 coils in place in grooves on the barrel. More grooves and coils will be added after the bugs from these are worked out. The 3 coils are wired in series and connected to the second channel on the o-scope. They work well, but the inter-connecting wiring of the coils needs to be done in a neater manner to reduce unwanted indications on the scope. But, it works, too. The patient is ready for the experiment to begin. REAL results tonight. Lloyd
Travis, That looks a whole lot better for capturing images than what I've been doing. Thanks you! I will give it a try.
the you tube video by MrTeslonian with a vacuum pump on the muzzle of a Texan? 2900 fps?
Quotethe you tube video by MrTeslonian with a vacuum pump on the muzzle of a Texan? 2900 fps?Any time the claimed energy output exceeds the energy input.... I have my doubts.... Bob
Yeah, but what about the mass of the air used to accelerate the bullet?.... Include that and the velocity goes wayyyyyyyy down....Bob
Darn, do i have to find a vacuum pump?
Quote from: lloyd-ss on January 08, 2019, 06:19:13 PMDarn, do i have to find a vacuum pump? I have and AC vacuum pump but that’s not going to be good enough but I’ll send it to you if you need it.
Quote from: oldpro on January 08, 2019, 08:14:49 PMQuote from: lloyd-ss on January 08, 2019, 06:19:13 PMDarn, do i have to find a vacuum pump? I have and AC vacuum pump but that’s not going to be good enough but I’ll send it to you if you need it.A 2 stage 7cfm vacuum pump should be more than adaquite it will pull a 20 ton A/C system down to 50 microns in about 2 hours.