PsychoGenetiX Posted July 7, 2011 Share Posted July 7, 2011 Hey everyone, newbie here. I was wondering whether this is the forum I should go to. I have built a 6.5in long crossbow out of pure Technic pieces. I don't like normal LEGO pieces because they seem cumbersome and boring to me. That is why I have a large collection of pure Technic. It launches projectiles ranging from normal 2.5'' long, 2mm thick toothpicks to 4mm thick, 4in long sharpened bamboo skewers at least 48 mph fast and has the capacity to shoot an accurate 10m. As you can see it is built to be a weapon of sorts. It uses 3 rubber bands, one for firing the projectile and two to hold the trigger mechanism locked. It is simple. It has only one moving part, the trigger mechanism. The difference between firing toothpicks and skewers is like a pistol's caliber change: The crossbow itself has a barrel 5 inches long, and for toothpicks it has circle pegs inside, for skewers nothing, leaving the circle peg holes open wider to fit the added length. The projectile sits free-floating when loaded, between the barrel and stabbing a piece of duct-tape on the rubber band. Now for the question: The projectile tends to flip over in mid-air, which causes the range at which it can penetrate the target to be reduced to 5m away. My guess is it's because we're talking about toothpicks and skewers which are light and small, their weight causing them to flip over because of the air resistance. My question is, does anyone have an idea how to counteract that? will fletching them fix it, like a real crossbow bolt? Or do I need to find another kind of wood to use as a bolt?\ Here are a few pictures of the CURRENT version, but keep in mind that it is an active and constantly changing model, as there is always something to improve: Loaded: Link to comment Share on other sites More sharing options...
McJobless Posted July 7, 2011 Share Posted July 7, 2011 First of all, THAT'S f***ING EPIC. Seriously, I could never build anything to that level of awesomeness. Also, you did post this in the right topic. I'm going to assume your prediction about air resistance is correct, but since I'm not the Mythbusters, I can't answer for sure. What I'd say you need to do is maybe make more streamlined, metal "darts" which can actually fly through the air with ease. Anyway, when the other guys login, I'm sure they'll have an array of answers. And welcome to RRU! Link to comment Share on other sites More sharing options...
Cyrem Posted July 7, 2011 Share Posted July 7, 2011 Wow that is very cool to say the least. Great design and impressive statistics of the crossbow. As for your question, I don't know much about aerodynamics either. But I'm going to go ahead and take a guess. Perhaps the acceleration is too high for such a lightweight projectile and the forces of the air passing around it are too strong. I would say try a combination of some different weighted woods and longer rubber bands(for less acceleration). Perhaps even a longer barrel may help keep it's accuracy while it accelerates through the crossbow. Also welcome! Link to comment Share on other sites More sharing options...
Cirevam Posted July 7, 2011 Share Posted July 7, 2011 You need some sort of weight on the front of the projectile for it to be balanced correctly. Try a few wraps of electrician's tape or something that won't catch on the barrel. That aside, this is the coolest looking Lego weapon I've ever seen. Link to comment Share on other sites More sharing options...
PsychoGenetiX Posted July 7, 2011 Author Share Posted July 7, 2011 Wow, thanks guys! I'll look into what you said. The duct tape idea seems doable, I'll try that. Thanks alot. Link to comment Share on other sites More sharing options...
Lair Posted July 7, 2011 Share Posted July 7, 2011 Toothpicks are probably too light and get caught by air resistance. And This thing is really great. I'm visualizing it with wheels. It looks like something frome Drome Racers. Yes, this is Crossbow. He shoows stuff at you. Link to comment Share on other sites More sharing options...
joev14 Posted July 7, 2011 Share Posted July 7, 2011 Wow, thanks guys! I'll look into what you said. The duct tape idea seems doable, I'll try that. Thanks alot. Another good idea might be to get some different rubberbands, like those huge super thick packing bands that can stretch super far and come back super hard. Link to comment Share on other sites More sharing options...
PsychoGenetiX Posted July 7, 2011 Author Share Posted July 7, 2011 Another good idea might be to get some different rubberbands, like those huge super thick packing bands that can stretch super far and come back super hard. God I wish I could find a couple of those. I love them. Toothpicks are probably too light and get caught by air resistance. And This thing is really great. I'm visualizing it with wheels. It looks like something frome Drome Racers. Yes, this is Crossbow. He shoows stuff at you. Lol! Okay guys, continuing from Cirevam's direction I had a grand idea: Instead of adding weight at the front which would require thinking up a new projectile, I'll take one of the big skewers and shave thin the back 2.5 inches which would leave the front thicker and heavier than the rest. I could even add fletches like this. I'll come back to you guys on whether this works well. ...After several tests and reworkings, I found out this WORKS! Shaving the back end of a skewer bolt thinner than the front and adding medical tape fletches is the way to go. The bolt flies tip-first and smashes its tip against my window from 10m away. I actually found out it takes alot of power to smash a skewer's tip like that with your hand against a table. Link to comment Share on other sites More sharing options...
PsychoGenetiX Posted July 8, 2011 Author Share Posted July 8, 2011 Bumping with content: The new arrows work perfectly. Here it is stuck in a piece of cardboard I put on my window for testing. Here is one of them on the swiss pocket knife I use to make them. This is the range from which I fired the arrow in the first picture at the cardboard. It's stuck right there in that position. I had also redesigned the crossbow a bit to make it sturdier and make more room for the arrows. and heres a pic of the sights just for the sake of being cool: Thanks guys, you helped alot. Link to comment Share on other sites More sharing options...
Cyrem Posted July 8, 2011 Share Posted July 8, 2011 The projectiles look great shaved and with the wings. Well done. Awesome scope ;P Link to comment Share on other sites More sharing options...
Lair Posted July 8, 2011 Share Posted July 8, 2011 Excellent work. It seems you've got it now. Link to comment Share on other sites More sharing options...
Addictgamer Posted July 8, 2011 Share Posted July 8, 2011 Wow, looking great! I wish I could make one of those too... Link to comment Share on other sites More sharing options...
PsychoGenetiX Posted July 8, 2011 Author Share Posted July 8, 2011 I'm sorry, if I could only make instructions I would, but I'm currently trying, besides working on simplifying it, to turn it into a sort of bolt-action crossbow that doesn't require loading manually. I hope I can get that to work. Link to comment Share on other sites More sharing options...
Addictgamer Posted July 8, 2011 Share Posted July 8, 2011 The problem isn't instructions. The problem is I own barely any technique pieces. Link to comment Share on other sites More sharing options...
PsychoGenetiX Posted July 8, 2011 Author Share Posted July 8, 2011 The problem isn't instructions. The problem is I own barely any technique pieces. Oh. Heh. It took me quite alot of time to gather up this collection, I don't buy normal LEGO sets, only Technic. I even have pieces from the old bionicle bike things and the Technic star wars sets. Link to comment Share on other sites More sharing options...
McJobless Posted July 9, 2011 Share Posted July 9, 2011 You're f***ing dangerous now. Remind me never to piss you off. Link to comment Share on other sites More sharing options...
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