The photos were taken in a traditional Michigan basement. I took the photos with the aid of a sound trigger with an adjustable timing delay. It works on the same principle as the plug in wall clapper that turns stuff on and off when it hears a loud noise. The design I built is the same as this one you can buy and put together for around $20, it is a really great site with step by step photo instructions if you aren’t used to reading circuit diagrams
http://www.hiviz.com/kits/sk2-du.htm. So with spare parts I had laying around I built one to trigger my flash, for my Exomag optimistically moving at 330fps I calculated that it would take approximately 1/100th of a second for the arrow to reach the end of the bow. I mounted my Nikon D70 with 18-70mm lens on my tripod and set it approximately 24mm, manually focused it to where the piece of plywood was and then placed my Nikon SB26 on top of the camera, being careful not to slide it all the way onto the flash shoe mount as I wanted it to fire only from the sound trigger and not when I “pushed” the camera button. The flash I set to manually fire at low power, the lower the power settings I used seemed to freeze the action more as the more power the flash outputs you start to see more movement. The camera was set at f5.6, ISO 400 with a 5 second exposure time. I have a remote control for my camera that you can see in my right hand that I would use to fire off the camera, and then I had up to 5 seconds to get my shot off. This had to be done in as near total darkness as I could get, hence the dungeonlike basement setting at night. The goal is to only have what you are interested in be lit up by just the flash and no outside light as that would contribute to more blur. Each frame I took individually and to see my target I put some glow paint on it so it would show up with the lights out downrange and I would attempt to position myself on the same spot on the plywood to shoot. In order to get different shots of the arrow as it moves down the bow I would adjust the time delay on the photo trigger. This would have been admittedly easier with a second person, one to run the camera and one to run the crossbow, then you would not need the remote control to run the camera, but hey, it was fun being geeky. If anyone would like help on making their own high speed photos feel free to ask away.
Boo, with the question about where the string drives the arrow, have you tried multiple layers of serving over a small diameter say 20 strand string to get it to push at the center of the arrow? I wonder if this would give you the same accuracy as a larger number of strand string with a single layer of serving but with faster velocities? If you ignore the differences in what they sound like.
Reading through the rave reviews on your strings Boo, I decided that I would try my hand at making my own Flemish strings. So with reading online and a couple of ¼ lb spools of Dacron I got to work experimenting. I came up with a pretty decent looking 36 strand string by starting with individual strand lengths of 53.5 inches and starting my end loops 8.5 inches in from the ends of the strands. I then did a center serving in Halo. They look nice and are holding brace height, though it will be a while before I get a chance to actually shoot them. The weight I got for them was 17.3 grams without any silencers installed, if I could get my hands on a scale I could put to measure the amount of tension in the string to maintain brace height I could figure out what the resonant frequency of the string should be. How much are your strings weighing in at?
The slight S shape of the string is probably due to two things I am guessing, one most likely being the difference in weight/position of the silencers along the string and the second may be caused by harmonic oscillation due to the lack of stretch by the fast flight string. I want to repeat this again on a string without the silencers installed and see what it looks like. One of the things I have been wondering about the fleece buzz busters was the fact that they very rapidly stop and snap forward over the very short time and distance as they reach brace height, sort of like cracking a whip, which seems to explain why their ends get so frayed looking, might be quieter with them out, if I only had a sound meter. Ideally I wanted to be able to figure out what the main frequency of the noise the bows are putting out and try to come up with a way of further quieting it based on that, not quite sure how to do that at this time, but it would be nice to know.
Keep the questions coming, I have an idea bouncing in my head on how to make the drawn bowstring be self centering that I am working on but will post it when I get more time to polish it up a bit more.
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, yes i think Boo is going to have to take on these questions.
