Triggermortis
Well-Known Member
How was the speed of a round measured or calculated before the advent of the modern chronograph?
Pre- chronograph speed measurement
- Thread starter Triggermortis
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Stalker62
Well-Known Member
Newton was the first to publish a speed for sound (in 1686) and to show how he made his calculation. He used a small pendulum to measure the amount of time the echo took. This method was much more accurate than any 17th-century clock, but was cumbersome and finicky.
I do remember as a very young man on manoeuvres with my local "Dad's Army"...
Seeing an artillery piece on a hill some distance away. I saw the flash and then (what seemed an age later) heard the bang.
The comedy smoke was not available for me...
Fairly sure, this also is an old 'tried and tested' method of measuring the speed of sound.
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Swedish
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@Stalker1962 Specsavers? 
Swedish
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Stalker62
Well-Known Member
Heym SR20
Well-Known Member
Using a ballistic pendulum, or a ballistic sled And physics.
As part of my A level course we had an air rifle and length of model railway track with truck with a load of plasticine. Knowing the mass of the pellet and the truck, and coefficient of friction you fired pellet into truck and measured how far it went down the track. Then you did some maths.
Ballistic pendulums have much less friction and are more accurate.
Ballistic pendulum - Wikipedia
Triggermortis
Well-Known Member
Just how accurate is this method compared to a modern chrono’?
I suppose there must of been the risk of pilot error?
I suppose there must of been the risk of pilot error?
Friend of mine worked in the tank barrel and round development industry. He was part of team that developed a round that would do 2km in 1 second. And it was a massive round. Essentially an armour piercing rod contained in a sabot. Apparently the multiple spectacular failures and blow ups along the way where quite something
S
S
There was. I made one once and it worked to some extent. Being only 36" between the discs a bullet needed to be rather slow to get any accurate measurements of the offset. I shot 200 grain 38 Special loads and got into the rabbit hole of measuring the length of the slot in the second disc and comparing it to the speed at that circumference on the disc. I bought my first chronograph shortly thereafter, a (Tippico Time Meter) and one set of discs that I did the math on came within 30 fps. Since the whole (chronoed) speed was 640 fps this was a huge error. I gave up on it. I retrospect, I think the speed of the motor driving the discs was a barnyard guess so it might have worked better than I thought. Gad. That was such a long time ago..... ~Muir
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