Crossbow Chronicles

[Tony Coiro 0]

So, I test fired the crossbow today. Some of the test results were impressive some were disheartening however all are fixable. The trigger worked great, maybe too well as you can see from the accidental dry-fire. It will be needing some more draw strength, I'd put it at maybe 35-45 pounds, certainly not enough. Effective range is only like 55 feet, so you might still be better off throwing rocks, however it's Christmas break for me so I'll have plenty of time to improve it. Here the vid, as always constructive critism appreciated, unconstructive critism appreciated if funny.

Tony "Danger Coiro

[Sam Salvati 76]

NICE! I would think it would fire better if the string was in contact with the arrow instead of being released then hitting the arrow then firing it. if the prongs that hold the string were likt two fingers holding the string with the arrow on the string in between.

Edited December 23, 2007 by Sam Salvati

[Tony Coiro 0]

NICE! I would think it would fire better if the string was in contact with the arrow instead of being released then hitting the arrow then firing it. if the prongs that hold the string were likt two fingers holding the string with the arrow on the string in between.

 

Thanks Sam! I was gonna do it like that, but I wanted to keep the trigger simple. The lever above the bolt makes the string have to line up in the notch of the arrow as well. However, I plan to almost double the power over the next few days, so more power should either prove my idea correct or just magnify any errors of design. I keep you guys posted.

Tony

[Geoff Keyes 525]

Try some pre-load on the bow. If you look at commercial crossbows, or even regular bows, the bow arms have a certain amount of load on them even with no pull on the string. You don't want the bow arms to "slap" or go slack at the end of the travel.

 

Just my .02

 

Geoff

[Tony Coiro 0]

Try some pre-load on the bow. If you look at commercial crossbows, or even regular bows, the bow arms have a certain amount of load on them even with no pull on the string. You don't want the bow arms to "slap" or go slack at the end of the travel.

 

Just my .02

 

Geoff

 

Yup, I've been wanting to fix that for awhile, I just couldn't resist a test fire, with the light draw strength, I wasn't worried about damage. Anyway, I'm just about to head down to the workshop, I post pictures if I make dramatic changes.

Tony

[Mike Lambiase 1]

Go to home depot and buy a 2" wide rift sawn board of red oak. make sure the grain runs parralell to the length of the bow, with as few run offs as you can get. Cut it to 4 foot.

 

Shape it like a long pyramid out to each limb tip, ending the taper around 1\2" wide, and glue drywall tape on the side that is going to be under tensile stress (the back of the bow) with some titebond III so it doesn't blow up.

round off the belly side a little bit (the side under compression) to avoid splintering the bow.

This bow will pull (depending on the stiffness of the oak available in your area) around 40-50 lbs and should cast a standard bow arrow a considerable distance.

 

The garden stakes that you are useing are not stiff enough for thier density. the limbs are too slow and clunky.

 

you need to increase your brace height to around 4 inches to load the limbs to give it the snap that it needs to launch the arrow with any speed.

 

the more speed you can move the string at (high draw weight-low limb mass), with the least arrow mass that you can get, the farther your arrow will go.

 

basic concepts for a quantum physicist...

 

Mike Lambiase

[Bill Hoffman 6]

Tony,

 

Before you test fire that cross bow again, can you say "SAFETY GLASSES"?

If a limb breaks, it's coming straight back to your face.

 

The exuberance of youth is a wonderful thing to see, but sometimes wisdom

is accentuated with scars. Don't stop having fun, but give a touch more

thought to the fragility of assorted body parts.

 

To one and all, "Merry Christmas".

 

Bill

[Tony Coiro 0]

Tony,

 

Before you test fire that cross bow again, can you say "SAFETY GLASSES"?

If a limb breaks, it's coming straight back to your face.

 

The exuberance of youth is a wonderful thing to see, but sometimes wisdom

is accentuated with scars. Don't stop having fun, but give a touch more

thought to the fragility of assorted body parts.

 

To one and all, "Merry Christmas".

 

Bill

 

I knew that was coming, but from the tests I did, I felt confident it wouldn't be a problem. However, I did "tastefully modify" the crossbow today, bringing it from the catergory of sane and logical to the proposterious and ridiculous. I knew I needed to up the power of the bow, but did not have more room for rods. So inspired by a model bi-plane we had lying around the basement and because it's been such a long time since my last engineering disaster, I built this. I plan to test it in full hockey gear (you might think I'm joking.....I'm not)

 

 

All the rods will be trimmed down to a uniform size and attached (still workin on figurin out how the hell I'm gonna do that one)

 

Space to load the bolt from the top or the side, also when the wood glue dries, I will be bolting all the joints together as well.

 

I might remove the wooden spacer or maybe I'll keep it there and shoot through it, just to show off.

 

I'm really lookin forward to shootin this. Should be a disaster. I'll keep you guys posted.

Tony "Danger" Coiro

Edited December 24, 2007 by Tony C

[Matt Gregory 6]

Tony,

 

Before you test fire that cross bow again, can you say "SAFETY GLASSES"?

If a limb breaks, it's coming straight back to your face.

 

The exuberance of youth is a wonderful thing to see, but sometimes wisdom

is accentuated with scars. Don't stop having fun, but give a touch more

thought to the fragility of assorted body parts.

 

To one and all, "Merry Christmas".

 

Bill

 

 

"You'll shoot your eye out, kid!"

 

 

Way to suck the fun out of it, Bill... next thing you know, you'll want us to put corks on the ends of our knives! :D

 

 

btw...how ya feelin', pal?

 

 

 

 

Great project, Tony - looks to be coming along great!

[Bill Hoffman 6]

Hey Matt,

 

No, don't want to take all the fun out of it. It's just

really hard to replace an eye. We've all taken chances

and gotten away with it, but sooner or later Murphy

will strike.

 

BTW, healing up nicely. Thanks for asking.

 

HAPPY NEW YEAR TO ALL!

 

Bill & Aline

[Sam Salvati 76]

WELL HOW'D IT GO?

 

#---------> O O

#--------> O O

O O O

#--------> #---------> O OOO O

O O O

O O

O O

Edited January 29, 2008 by Sam Salvati

[Tony Coiro 0]

WELL HOW'D IT GO?

 

#---------> O O

#--------> O O

O O O

#--------> #---------> O OOO O

O O O

O O

O O

 

 

Haha, nice picture Sam. The between school and Indiana winter, we haven't had the competition yet. Me and my friend are worried about losing our bolts under the snow. Soon though. I removed the double decker bow (it was really just an unnessesary complication, I guess that's what bored engineers do) and just reinforced the orginal, works like a charm. I also mounted a rachet draw system, really bumps up the intimidation factor.

Tony