ishi78 Posted September 22, 2005 Share Posted September 22, 2005 In fact the problem around birke's first question is not the re-arming of the blue part, but the re-arming of the nut : when the string has left the nut, there is neither a protruding element nor a spiral spring on the nut to make it turn clockwise. For the second item, I suppose that it may be a reinforcement of the nut in the area where it is most stressed. I agree with this part of the design. Nevertheless, I think that your design is too complicated for the purpose even with a high draw strength bow. You should preferably refer to the mecanism of my Barnett crossbow which has been sketched by Jihaif in this post : http://webarcherie.com/forum/index.php?showtopic=5592 I can testify that this mechanism is able to hold a 175lbs bow :bhaoui..: Quote Link to comment Share on other sites More sharing options...
Jihaif Posted September 22, 2005 Share Posted September 22, 2005 (edited) Very nice design Rapsod! Answering to Birke, I think rearming is done automatically by the action of the "spiral spring". When nut rotates clockwise by action of the crossbow string, the dark blue piece, tumbler, locks on the nut and the trigger to. So, according to Birke about the part of drawing he shows by the circle, I've modified the original drawing to adapt to my cinematic point of vue. May be I'm wrong? The spiral spring must be fited to reset the tumbler in the dark blue position. Adding the "nut finger" will make easier rotation of nut by string pushing. Edited September 22, 2005 by Jihaif Quote Link to comment Share on other sites More sharing options...
Jihaif Posted September 22, 2005 Share Posted September 22, 2005 You draw faster Ishi! I was drawing while you wrote. Quote Link to comment Share on other sites More sharing options...
ishi78 Posted September 22, 2005 Share Posted September 22, 2005 Gotcha !!!! In fact we are three typing together :bhaoui..: Quote Link to comment Share on other sites More sharing options...
Jihaif Posted September 22, 2005 Share Posted September 22, 2005 Yeah but I hope we are free typing to! Quote Link to comment Share on other sites More sharing options...
ishi78 Posted September 22, 2005 Share Posted September 22, 2005 Oh, you didn't know that I'm paid for each line of post, that's the reason why... So sorry, but my typing is not free Quote Link to comment Share on other sites More sharing options...
Jihaif Posted September 22, 2005 Share Posted September 22, 2005 GEEEERY! Come on! I've a lot of questions for you foutre ass! Quote Link to comment Share on other sites More sharing options...
rapsod Posted September 23, 2005 Author Share Posted September 23, 2005 Well, Ishi78 said everything. There is mising part in this design and it is stoper (little black circle) that stops a blue part. :107: Why? Because spiral sping can turn nut in wrong direction!!! In Jihaif desing there is no need for that because nut finger do that function. How to return nut? With finger. There is enough friction between wood and nut to stop nut as it pases the flat surface of crossbow. If there is not enough friction than a piece of skin is put between wood and nut. The nut finger is not good because it can make big bang when it hit wood and lieve deep mark. What if surface of crossbow is made of cow bones? Nut finger could break it. Who say 175 libres? How about 500 libres (over 250 kg or prcisely spiking 2500 N)? Real siege crossbow for head cuting. What program do you use for drawing. I use corel draw 12. Quote Link to comment Share on other sites More sharing options...
JMG Posted September 23, 2005 Share Posted September 23, 2005 Jihaif is using the wonderful free software given by microsoft, I said : PAINT :29: Quote Link to comment Share on other sites More sharing options...
Robin 60 Posted September 23, 2005 Share Posted September 23, 2005 foutre ass! Quote Link to comment Share on other sites More sharing options...
Jihaif Posted September 23, 2005 Share Posted September 23, 2005 Answering to Birke, I think rearming is done automatically by the action of the "spiral spring". Sorry Rapsod. The idea I wanted to develop was: "Answering to Birke, I think LOCKING is done automatically by the action of the "spiral spring". So, I drew a new mortise in the nut in this way. I drew "the nut finger" only to facilitate rearming. I agree with you for damages made by the hit of this nut finger on the wood of the tip. Are you sure to keap a constant friction strength of the nut for stopping his rotation after a lot of shots? Quote Link to comment Share on other sites More sharing options...
rapsod Posted September 24, 2005 Author Share Posted September 24, 2005 (edited) No. That is problem. Maybe make a nut as yo-yo with spiral spring (like in clock) in center. I forgot name of site but it was like 19......./crossbows/crossbows.htm. In that site nut is fix with simple binding. Maybe that binding act as return spring for nut. I try to draw it today and post it later. I try to use Gimp for drawing (it is free) but I needed something that do vector grapfic. Than is much easier to project stuff. So I get pirat version of Corel and it is 10 times better than autocad2005. :pirate: Rapsod :demonban: Yeah baby,can I play with madness!!! Edited September 24, 2005 by rapsod Quote Link to comment Share on other sites More sharing options...
Jihaif Posted September 24, 2005 Share Posted September 24, 2005 A real spiral spring like clock-making will be the best solution you're right but I don't know if we can find this kind of spring easily and strong enough for a crossbow use? An other solution can be solved by making springs with piano strings. For nut feedback, I propose to you this draw: Quote Link to comment Share on other sites More sharing options...
Jihaif Posted September 24, 2005 Share Posted September 24, 2005 (edited) I'm expecting "Inventor", a specific soft for mechanical studies from the same editor than "Autocad". But i'ts a complex one and learning will be......hard and long. :( :( :( I don't know "Gimp"... Edited September 24, 2005 by Jihaif Quote Link to comment Share on other sites More sharing options...
ishi78 Posted September 24, 2005 Share Posted September 24, 2005 Don't worry Jihaif, no CAD software will ever replace the nice look of your "Paint" drawings. Although I may be responsible for this idea at the beginning, I'm now a little mixed up with your spring'd nut : if the nut is set back after string release by this spring (whatever the choice), the string will have to jump over the nut at full draw. So I think that you'd better optimize your first design with a "finger" reduced to its minimal dimension : not protruding from the nut ouside diameter, making a kind of U notch in the nut, so it will be the string itself which should replace the nut in its armed position. Quote Link to comment Share on other sites More sharing options...
Jihaif Posted September 25, 2005 Share Posted September 25, 2005 (edited) the string will have to jump over the nut at full draw. So I think that you'd better optimize your first design with a "finger" reduced to its minimal dimension : not protruding from the nut ouside diameter, making a kind of U notch in the nut, so it will be the string itself which should replace the nut in its armed position. Well done Ishi: i'ts THE idea! :29: I've drawn a new design following your concept. But if Rapsod want keep the original design, I've "redrawn" the nut spiral spring. Edited September 25, 2005 by Jihaif Quote Link to comment Share on other sites More sharing options...
Robin 60 Posted September 25, 2005 Share Posted September 25, 2005 :24: :24: :24: :29: :29: Quote Link to comment Share on other sites More sharing options...
rapsod Posted September 25, 2005 Author Share Posted September 25, 2005 Ok. The nut spring of this type is very good idea!!! Eather idea for "blue part" spring is very good. I don't think that stop pin is good idea for the same reason the previous finger nut is not good. I will make "bang" when it hit it. Nut will be made of plastic probably so the stop pin could break nut. I don't know. Is there probability that nut turn more than 90*? I don't know!!!!!!!!!!!!!!!!! :05: Rapsod Quote Link to comment Share on other sites More sharing options...
Robin 60 Posted September 25, 2005 Share Posted September 25, 2005 I had an idea : Quote Link to comment Share on other sites More sharing options...
rapsod Posted September 25, 2005 Author Share Posted September 25, 2005 I have idea. AUTOBLOCKING NUT WITHOUT BANG!!! The idea is very simple. The main problem now is mass of nut. If mass is too big it will block. If mass is small tre bien!!! Quote Link to comment Share on other sites More sharing options...
rapsod Posted September 25, 2005 Author Share Posted September 25, 2005 When I finished previous picture I realise that maybe is good to use leaf spring to slow down nut. So you use autoblocking nut with this spring and voila you have a very silent crossbow. Maybe. :bhaoui..: Quote Link to comment Share on other sites More sharing options...
rapsod Posted September 25, 2005 Author Share Posted September 25, 2005 The last picture is recicled so it is not shown autoblocking nut. In this picture is front view of nut. It have this shape because it is easier to make it on lathe (machine for making round cross section and much more). Quote Link to comment Share on other sites More sharing options...
Jihaif Posted September 25, 2005 Share Posted September 25, 2005 Nice work Rapsod! :29: :29: :29: Y're back to the first idea: displace the nut center versus the wood hole one. Your spring break is well done. Tell us the next chapter of this project. Quote Link to comment Share on other sites More sharing options...
ishi78 Posted September 25, 2005 Share Posted September 25, 2005 Hello jolly brain stormers ! :37: Its a pleasure to see your brain steaming that way ! But let me ask a question : why do you want a spring on the nut ? I don't feel there is need for one and I don't remember having seen any on the drawings and pictures I saw up to now. :100: If you feel there is a need to brake the nut rotation, I can assure it is useless, mainly because the nut is very light so it has a very small inertia momentum and it will stop as soon as the rope has left the slot. On the other side, if you have a spring that reset the nut in the armed position, once again you will need the rope to jump over it. :bhaoui..: Quote Link to comment Share on other sites More sharing options...
Robin 60 Posted September 26, 2005 Share Posted September 26, 2005 and... what do you think about my idea ? Quote Link to comment Share on other sites More sharing options...
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