# Bow Engineering



## Keystone Killer (Sep 5, 2009)

I am a mechanical engineering student in my last year of school. As part of the criteria to graduate, i have to design AND build a project. The guidelines are pretty general. This is a two semester project. Right now i am in the design phase. I need a design, and it needs submitted and approved by mid december. I also work in a CNC machine shop. So i have access to some very nice equipment. 

I was hoping to design and build a riser at the least, and a full bow at the most (minus the limbs) 

At first, i didnt even consider it, thinking the school would never permit me to build a bow (weapon). Thats when i got the idea to just make a riser. I have ran it past the professor, he would like to know more about what i would do, and how i would design it. thats were im kind of stuck. I have had many classes on strength of materials, metallurgy, dynamics..etc. However, I cant actually determine how strong the forces i need to design for are, and where they are located. 

I have no intent to start making risers or bows, i just want to make a kickin school project that demonstrates my engineering and my ability in a shop. 

Anybody have any experience with this?
Feel free to PM me with suggestions or advice. 
Thanks.


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## Huaco (Jul 7, 2006)

I am a CSWA SolidWorks user. If you have any questions as far as that programs go, I may be able to help. SolidWorks has a program that ships with it called Cosmos Express. It will allow you to simulate the failure points and you can input all types of variables like safety factor and force.

As far as the riser, I know that most all risers will bend slightly during the draw cycle. I have no idea how much they bend but they do. 

If you need any help with the modeling I have SW on my laptop and I can do some modeling for you. YOU JUST HAVE TO DO THE DESIGN. (not gonna let ya cheat) HA... JK :wink:


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## Keystone Killer (Sep 5, 2009)

Huaco, thanks for the offer. I have not used cosmos, but i have heard of it. I do know Pro Engineer and Pro Mechanica, but I have determined that SW is a much more user friendly software program. Anything i do for this project would be SW and its partner programs.


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## BROX (Sep 29, 2005)

Do an AT name search for Rattler he's a mad scientist he probably has some ideas


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## Mig (Nov 26, 2008)

I tried to do the exact thing and I kept getting turned down. Stupid Bowling Green State University. I couldn't even make a sight or a complicated fall away rest!!!!!!! Because it related back to a weapon. I did make a spin cast fishing reel that worked when your turned the handle. I'm more of an inventor user because if you're a student at a school they let you download and use their programs. Right now I have inventor 2008 for 13 months. autodesk allows students to download and use almost all of their programs. some only for a month but others for a lot longer. I have also used fempro for stress analysis tests. Are you at a school that has all these programs in a computer lab?

I think inventor, solidworks, and catia are the best cad programs out there. Never really like Pro E.


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## Keystone Killer (Sep 5, 2009)

Well, like I said, its still a long shot. I have autodesk and solidworks on my own PC. The school has Pro E, SW, and fempro, but i have had no instruction in fempro. Im not a fan of Pro E myself.


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## Huaco (Jul 7, 2006)

Mig said:


> I tried to do the exact thing and I kept getting turned down. Stupid Bowling Green State University. I couldn't even make a sight or a complicated fall away rest!!!!!!! Because it related back to a weapon. I did make a spin cast fishing reel that worked when your turned the handle. I'm more of an inventor user because if you're a student at a school they let you download and use their programs. Right now I have inventor 2008 for 13 months. autodesk allows students to download and use almost all of their programs. some only for a month but others for a lot longer. I have also used fempro for stress analysis tests. Are you at a school that has all these programs in a computer lab?
> 
> I think inventor, solidworks, and catia are the best cad programs out there. Never really like Pro E.


I know of a little "trick" to fool the program so you can use them AS LONG AS YOU WANT... pm me if you want to know how.

Don't want to throw it out in the public.


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## Mig (Nov 26, 2008)

As I recall fempro was pretty easy. assign the parts the material. select the types of the forces and what part of the part is being forced in what direction. Then it'll give you a simulation and everything.


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## Keystone Killer (Sep 5, 2009)

yeah with this my biggest issue is measuring or obtaining accurate forces that would be exerted on the riser and or other mechanical parts.


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## Mig (Nov 26, 2008)

Ya my school pretty much hit the surface of all the programs. We had to teach ourselves for more in depth complicated features. There should be some type of tutorials you can find to help you.


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## Huaco (Jul 7, 2006)

pm sent...


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## madarchery (May 28, 2003)

Well not a rocket scientist. But for a starting point I think you will need to contact a limb manufacturer and get the load forces for a set of limbs. From there you should be able to determine the forces applied to the riser and go from there. With out the limb specs you have no idea of the preload stress and load ranges.

Not sure how else to go about it. Unless ya wanted to make a cool paper weight.


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## eltice (Jan 26, 2009)

*testing loads*

I have thought about this for a day and this is the best I can start with, I hope that you have access to a force sensor in you "mechanics of material lab" or somewhere else on campus, and associated data collection.

You could perform several measurements and build your estimate from there,
(But you would need a bow press)

One is to create a "test string" with a tension load sensor built in you could measure the preload tension (to calibrate you would need to have the bow in the press with no tension on the string) and with a drawboard for safety sake, you can measure the loaded string tension at full draw.

also you can measure the preload in the limbs, ie with string on ATA compared to no string ata and measure tillers and use trig to create a estimate of the deflection and then load a limb in a "pocket" fixture matching your design on the riser, this wouldn't account for th riser flex but you could estimate that.

I hope these thought help you get going in the right direction for your project

Feel free to pm me,

I have a BS in ME from Michigan Technological University


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## jim p (Oct 29, 2003)

Maybe I am not seeing the big picture. If you have a 70# pull bow, there would be 70# of force applied to the riser at the grip and 35# of force applied to the ends of the riser. Now the G forces created at the firing of the bow might be more complicated. By knowing the IBO speed of the bow and the mass of each component and the distance over which the components stop at the end of the shot you might be able to calculate the maximum G forces that the bow would see.

Good luck with the project. Once you get it worked out educate me some and tell me what you found.


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## madarchery (May 28, 2003)

Jim off topic here. But 70# does not take in the account the preload of the limbs. That is applied by the bow press and "held" by the string.

And I would guess even your 70# pull is determined by the size and shape of the cam. Thus actually loading a variable amount of energy.


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## Keystone Killer (Sep 5, 2009)

madarchery said:


> Jim off topic here. But 70# does not take in the account the preload of the limbs. That is applied by the bow press and "held" by the string.
> 
> And I would guess even your 70# pull is determined by the size and shape of the cam. Thus actually loading a variable amount of energy.


Its a bit more complicated than that. First off, the load isnt just split in 1/2. If the riser was a straight peice of aluminum with no bends and perpendictular limb connection, than that would be along the lines of what you said. But when the forces are not perp, you have to account for the angles, and take the cosine and sins of them to determine the forces. then again like another guy said, you have to know what the preload is. But thanks for all the input thus far. I appriciate it, ill keep you guys posted.


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## madarchery (May 28, 2003)

Your the engineer. I am just a thinker

Post up when you build.


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## jim p (Oct 29, 2003)

If you want to know the preload take a ratchet press and put a scale in line with it or take a scale and pull the string maybe an inch and then calculate the force at the limb tips based on your readings and the angle of the string. A bow is just a simple static system until you release the arrow, that's when interesting things happen.

While you are designing the bow, maybe you can tell me why a bow rated at 300 fps IBO can't use a 3 grain per pound arrow so that a person with a 26" draw can shoot the bow at 300 fps. I think that all the major forces occur in a bow as all the moving parts stop at the end of the shot and therefore a person should be able to shoot at IBO speed no matter what his draw length.


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## WI Moose (Feb 6, 2007)

I just read this and started brain storming on it. I am a civil engineer so I understand most of what you are trying to accomplish. Designing you own riser: you will have to a point load support (hand position/grip), then you will have to take into account the distance to the limb pockets and the deflection of he material over that distance, you will need to study the connection of the limbs to the bow, and finally all the forces generated at the limb pockets and throughout the system (riser)

At the pockets, you will have 3 forces. the downward/inward force of both a preloaded condition and final drawn bow condition, the rearward force of the bow being drawing and the momentomary force (rotationary). This will need to be calcuated for all three positions (at rest, drawing/drawn and shooting). You will need to analyze the system in its entirety to understand the riser design. 

So you will need to know what limbs your are going to use and connection they require to the riser. Then you will need to decide what stress you wish to design for and provide yourself with a safty factor. There are three different riser shapes that you will need research and decide which to use (straight, deflex and reflex). If this was my project, I don't know if I would try to attempt a compound bow due to the additional calculations that most likely be required due to the cams and their designs. I would look into designing a recurve and get radical with the design. My 2 cents.


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## PoppieWellie (Sep 16, 2009)

Mig said:


> I tried to do the exact thing and I kept getting turned down. Stupid Bowling Green State University. I couldn't even make a sight or a complicated fall away rest!!!!!!! Because it related back to a weapon. I did make a spin cast fishing reel that worked when your turned the handle. I'm more of an inventor user because if you're a student at a school they let you download and use their programs. Right now I have inventor 2008 for 13 months. autodesk allows students to download and use almost all of their programs. some only for a month but others for a lot longer. I have also used fempro for stress analysis tests. Are you at a school that has all these programs in a computer lab?
> 
> I think inventor, solidworks, and catia are the best cad programs out there. Never really like Pro E.


That ought to be banned as a school project as well! A weapon against them poor fish ?

Who is the professor in charge ? he ought to be losing his job over this!


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## Keystone Killer (Sep 5, 2009)

Hmm very helpful input. I never thought about a recurve, mainly b/c i know little or nothing about them. However after just reading a little on the internet, i have found that it could be a pretty cool idea, and minimize some headaches in calculations. I was also thinking, i could make the riser, buy some recurve limbs and leave the string off for at school and it will be no more harmful than a 6' peice of round stock.. lol. Im going to use that as a talking point when i present this proposal in greater detail next week to them. Any thoughts on stratigy to convince them?

A co worker today told me to contact some manufacturers directly.. I think i will, the worst i can get is: "no we cant help you" 

Still, everything is banking on getting the prof's on board with the idea.


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## bobbyh (Dec 22, 2008)

*youtube*

go to youtube and search for homemade compound bow, I believe there are two different videos, and one is all metal, limbs and all, the guy says he keeps it at 40 lb draw weight, but can can more out of it , pretty neat bow that works 
bobbyh


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## bobbyh (Dec 22, 2008)

*youtube*

go to youtube and search for homemade compound bow, I believe there are two different videos, and one is all metal, limbs and all, the guy says he keeps it at 40 lb draw weight, but can get more out of it , pretty neat bow that works 
bobbyh


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## Mig (Nov 26, 2008)

PoppieWellie said:


> That ought to be banned as a school project as well! A weapon against them poor fish ?
> 
> Who is the professor in charge ? he ought to be losing his job over this!


My professor is really cool. The Dean of the school does not allow it. This was a full semester project and nothing else. I guess they just don't allow any type of weapon to associated with the school. Otherwise the professor would be fired. 

There was a kid my freshman year, same dorm building as me, that had a loaded shotgun in his closet. He was part of the ROTC. The shotgun was loaded for a reason. He had a list of people down his hallway he was going to kill, and one day he posted a paper on each person's door with the day he would come and kill that them. He was arrested. That might be why they didn't allow weapon design. could be another reason though


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## Huaco (Jul 7, 2006)

Mig said:


> My professor is really cool. The Dean of the school does not allow it. This was a full semester project and nothing else. I guess they just don't allow any type of weapon to associated with the school. Otherwise the professor would be fired.
> 
> 
> There was a kid my freshman year, same dorm building as me, that had a loaded shotgun in his closet. He was part of the ROTC. The shotgun was loaded for a reason. He had a list of people down his hallway he was going to kill, and one day he posted a paper on each person's door with the day he would come and kill that them. He was arrested. That might be why they didn't allow weapon design. could be another reason though


 You didn't have any paper on your door did you? 

My uncle used to tell me stories of my college. I stayed in the same dorm hall he stayed in. They would go deer hunting (with the guns they kept in their rooms) gut 'em, bring 'em back and hang them in the open showers to bleed out and quarter out. HA! how times have changed. I bet you would get arrested now-days for having a cap gun on campus!


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## gr8brew (Feb 4, 2007)

Mig said:


> I tried to do the exact thing and I kept getting turned down. Stupid Bowling Green State University. I couldn't even make a sight or a complicated fall away rest!!!!!!! Because it related back to a weapon. I did make a spin cast fishing reel that worked when your turned the handle. I'm more of an inventor user because if you're a student at a school they let you download and use their programs. Right now I have inventor 2008 for 13 months. autodesk allows students to download and use almost all of their programs. some only for a month but others for a lot longer. I have also used fempro for stress analysis tests. Are you at a school that has all these programs in a computer lab?
> 
> I think inventor, solidworks, and catia are the best cad programs out there. Never really like Pro E.


Personally I would make some sort of movable sight. Something you could even use perhaps you might make some sort of ground breaking inovation who knows. I would avoid making something that is not complete or just a component. I would think it would be more impressive for your to prof if you demonstrate how you could make and use it. Perhaps you could make a video demonstration of you using it to shoot different yardages. I would almost bet your professor would bust a nut if you made a sight that incorporated the physics of arrow flight into a working piece of equiptment. Just my two cents.

Cheers
Good luck


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## Hoosieroutdoors (Jan 14, 2006)

1 little tidbit of info that may help, and you can check with BCY and Brownell bowstring companies. The majority of todays bows will generate up to 200 lbs of force, the 60-70 lbs limb ratings are only that,,what the limbs are rated for. Most all the bow manufacturers use T6 6061-6063 aluminum for their risers and cams, I would call 1 of the big bow companies and explain your project to them and ask to speak with 1 of their design engineers to get all the force specs so you have the right info to build on. Would hate to see you build something that could hurt you.


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## Keystone Killer (Sep 5, 2009)

Well Monday is the big day. Hoping for a 'YES"


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## Mig (Nov 26, 2008)

gr8brew said:


> Personally I would make some sort of movable sight. Something you could even use perhaps you might make some sort of ground breaking inovation who knows. I would avoid making something that is not complete or just a component. I would think it would be more impressive for your to prof if you demonstrate how you could make and use it. Perhaps you could make a video demonstration of you using it to shoot different yardages. I would almost bet your professor would bust a nut if you made a sight that incorporated the physics of arrow flight into a working piece of equiptment. Just my two cents.
> 
> Cheers
> Good luck


Thats a good idea. Too bad i already finished this class last spring.  I bet he still would have turned me down though. I was thinking of designing a slider sight that you can extend in and out like a dovetail sight... good idea???


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## PoppieWellie (Sep 16, 2009)

Mig said:


> My professor is really cool. The Dean of the school does not allow it. This was a full semester project and nothing else. I guess they just don't allow any type of weapon to associated with the school. Otherwise the professor would be fired.
> 
> There was a kid my freshman year, same dorm building as me, that had a loaded shotgun in his closet. He was part of the ROTC. The shotgun was loaded for a reason. He had a list of people down his hallway he was going to kill, and one day he posted a paper on each person's door with the day he would come and kill that them. He was arrested. That might be why they didn't allow weapon design. could be another reason though


Hmmm....

Does the campus allows plastic knife ? It is a deadly weapon too, you know!

When I was visiting Japan, in some part of that country, carrying a concealed plastic knife is considered 'ninja weaponry'. Go figure.


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## jim p (Oct 29, 2003)

What amuses me is that a plastic knife is a weapon and a 3500 pound car is not. I could be a weapon if I chose to so I try to stay away from any place where a weapon is not allowed.


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## AmishArcher (Feb 6, 2008)

could'nt you just make a metal birdhouse with a hinged roof??? Sounds much easier


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## BagginBigguns (Aug 17, 2004)

This project would be so excellent! I received a BSME back in 2000 and considered doing a bow design at the time. I ended up taking on the SAE Aero Design project instead.

If I was going to tackle this project, I would begin by determining the cam system that I wish to model. I would then write a spreadsheet or VBA program that allowed me to enter some general design parameters (bow dimensions, cam profile, limb spring constants, etc.) and evaluate the riser loads continuously through a full draw stroke. Then, based on those loads, I would perform an iterative FEA on the riser design to optimize (lowest mass) the design. I would also investigate the dynamic effects of releasing an arrow and the associated loads transmitted to the riser.

That's some fun stuff right there. It's pretty high level - especially in the statics analysis with understanding free-body-diagramming - but it would be a great experience, and perhaps even launch you into an awesome career.

Best of luck to you!

-John


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## BoonerToon (Feb 1, 2008)

i think this just might qualify as the most intelligent thread on AT. . . and it makes you sit and think about all the R&D that is done (and copied) in the archery industry . . .


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## s26286603 (Jul 13, 2008)

hahaha, this is great, here is the thing, im also a final year mechanical engineering student and i can tell you straight up, do a recurve bow. I have designed and built a recurve bow that is of olympic standard and is left hand right hand as well as it can change length ie 23 to 27 inch. The Search for bob koi on the net he is a proffessor who has come up with theorys for limb forces and so on. What he suggests, in a recurve bow, is that the bending moment in the limbs at full draw is basically the same as that as when the arrow leaves the string, so ie, the angle of the string is different therefore the increase in force, 4 times higher in the string. I used solid works and simexpert( ie patran with an awesome gui) my bow works and im doing vibration tests on it soon. to convince them to make a recurve is easier by saying that it is a olympic sport and that it incorporates all the thgings a project needs too.


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## Keystone Killer (Sep 5, 2009)

Wow, thanks for that info...Im still trying to convince them.


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## amishracing (Jan 16, 2008)

Huaco said:


> I am a CSWA SolidWorks user. If you have any questions as far as that programs go, I may be able to help. SolidWorks has a program that ships with it called Cosmos Express. It will allow you to simulate the failure points and you can input all types of variables like safety factor and force.
> 
> As far as the riser, I know that most all risers will bend slightly during the draw cycle. I have no idea how much they bend but they do.
> 
> If you need any help with the modeling I have SW on my laptop and I can do some modeling for you. YOU JUST HAVE TO DO THE DESIGN. (not gonna let ya cheat) HA... JK :wink:


if you could clamp a bows riser into a fixture or vice at one end or the other durring a draw cycle, you could use a dial indicator to see how much it flexes


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## iborlang (Nov 19, 2008)

*Recurve or Modern Long Bow*

I'm in agreement with everybody else on the recurve riser. Take a look at Tradtalk.com or Tradgang.com. Lots of posters are 'worfing' old compound bow risers into super solid, super stable, super shooting recurve bows. There's a niche market that could be filled with a nicely machined compact aluminum riser, say 14" or 16" long. The ILF limbs bolt on so easily, you just need a flat mounting surface, a locating pin, and a limb bolt. The stresses are pretty manageable as well. My dad built a riser out of Rutland Plywoods laminated hardwood plywood, it was really "dainty", but it was super light in the hand and a really nice shooter with 55# Hoyt recurve limbs. He put several hundred arrows through that bow until it started to show stress fractures at the arrow shelf, a problem that could be easily cured by using a high performance material like T6061 Aluminum.

I think the most important and sometimes most difficult thing to do as an engineer is to properly define your design problem. What do you want specifically, is there a market for it, and why would the consumer want to buy yours? There are hundreds of bows out there that are different for one reason or another so just make sure your riser design meets your requirments. Setting out to design the most awesomest bow ever is a pretty wide open problem and would be difficult to accomplish - I mean it has taken 40+ years of development and field testing for compound bows to reach the level of sophistication that we archers gladly take for granted.

Best of luck with your project!


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## Keystone Killer (Sep 5, 2009)

UPDATE:
The project is approved, design has begun! 
Ill be sure to keep this thread updated with whats going on. The project is due early May 2010, but the sooner i can get a design, the sooner i can machine it.

I have decided to go with the recurve riser. I think its easier to design for and I will have alot more confidence in the safety of it. I am going to buy 'an old recurve' and base my design for the limbs on it, unless i can find good cheap limbs or find a way to make it somewhat universal. 

Im very excited at this point, and cant wait to get things going in solid works!


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## Atchison (Apr 15, 2009)

Let me know if there is any specific testing you want to do on your final project, I'm an electrical engineer and my company is a sensor manufacturer, I may be able to help test load/force, strain, etc.....

Great project, wish I could have done something like that, but not too much electricity in it:tongue:


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## WI Moose (Feb 6, 2007)

Keystone Killer said:


> UPDATE:
> The project is approved, design has begun!
> Ill be sure to keep this thread updated with whats going on. The project is due early May 2010, but the sooner i can get a design, the sooner i can machine it.
> 
> ...


Nice, keep us posted on your progress. I look forward to seeing how this progresses. :thumbs_up


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## MR Pilsner (Apr 17, 2009)

*Don't purchase an old recurve just yet*

Have you acquired an old recurve yet?

I may have one to give you, maybe we could work out some sort of you pay shipping for free bow. Something or other. Or maybe it'll cost more to ship than for you to pick up an old one.

It is an old bear archery takedown, early 80's i think. It's what I used to shoot when I was a kid. 40 lb fiberglass limbs, steel or aluminum riser. I can't tell its painted. The limbs just kind of snap in, there are no bolts, they would be easy to drag around with you, measure, bend, break, testing of sorts, do what you want with em.

I don't shoot it anymore, haven't for years, it can still be strung and played with for your design project though. I could even throw in some of the old arrows. I have always been into the traditional type bows, no fancy wheels and sights for me. I have even built a couple of longbows from scratch, I understand the forces enough to build one, not necessarily enough to design and document. I just kind of shape a little hear and there until a bow emerges.

If you have questions regarding traditional bow limbs, recurves or longbow, try posting questions in the traditional sub forum as well here on AT. They are good bunch of knowledagble guys willing to help. A good number of them there also build from scratch, its where my first ideas were from.

I propose this idea as I am a structural engineer myself and have found some enjoyment from the engi-nerdi-ness of this thread relating to archery.

Shoot me a private message if you are interested, I'll respond and we can work something out from there.


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## daltongang (Jul 29, 2009)

Well, I just realised after reading all of this, that I am dumber than a bag of hammers!:tongue:


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## Keystone Killer (Sep 5, 2009)

daltongang said:


> Well, I just realised after reading all of this, that I am dumber than a bag of hammers!:tongue:


Nah, i dont think so. Id bet there are things you could talk about that would make me seem dumber than a box of rocks.


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## petrey10 (Oct 24, 2008)

my head hurts


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## Liviu (Oct 20, 2009)

Huaco said:


> I am a CSWA SolidWorks user. If you have any questions as far as that programs go, I may be able to help. SolidWorks has a program that ships with it called Cosmos Express. It will allow you to simulate the failure points and you can input all types of variables like safety factor and force.


Keystone,

Just one observation, Cosmos Express is just a basic FEA program, with basic loads and limited input. It's probably not powerful/sofisticated enough for what you are trying to achieve.
I really believe that you need the actual CosomsWorks in order to carry out the tasks that you set forth.

Just a glance at any bow riser (and to me they look like art), and one can see the sweeping curves, the "sexy" weight cut-outs, the sight window, all of these are complex surfaces that only CosmosWorks can deal with.

Best wishes,
Liviu


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## Huaco (Jul 7, 2006)

Yep... Liviu is probably correct about the limitations of Cosmos Express. It will analyze it, but probably not to the extent that you are looking for without stepping up to CosmosWorks. 
SolidWorks is "shipping" with all these programs now, but they are more or less "teaser" programs to get you to buy the full blown version of the supplimental program you are using.


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## Keystone Killer (Sep 5, 2009)

Funny you guys brought that up. I was just talking with a professor today who taught me Pro Engineer/Pro Mechanica. I was picking his brain about Cosmos, and its capabilities. He has limited experience with it, and has a book that he is going to lend to me. I would have access to Cosmos Works, but idk what the learning curve is. Any of you guys deal with CW? Its going to be challanging enough for me to get this thing dialed in with Solid works, dont want to get into somthing i cant figure out. 
Im making the riser happen no matter what. I just havent decided on whats feasable for testing and analyizing. I had a generous offer from a member who works with sensors and electronics. 

Just like to take time to thank those of you who have been PMing me with various ideas/tips/suggestions/references. Im getting a VAST amount of info. Havent got back to everyone just yet, but thanks, ill get there!


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## Liviu (Oct 20, 2009)

Huaco,
You hit the nail right in the head. All the "express" programs are teasers, I would say sort of _bait and switch(back)_ if I'm allowed the pun.

Keystone,
I have used and still using CW but very seldom and for simpler parts, e.g. structural beams, tubing, plates and such...
I do believe that the hardest part is to figure out the loads (areas, distribution and direction). Once you input these, the sofware takes over.

The more I think about it, I realize that maybe you can keep it simple.

Example:
Assuming that you pull 70# on the imaginary string, that means that your hand on the riser is pushing 70#.

Now a trick that I would try, is that when doing the actual modelling, to create a certain surface well defined where the hand touches the riser (of course it would be only the narrow portion between thumb and index finger).
This would help when you're doing the FEA, as the 70# force now will be distributed on that particular defined surface.

The end of the riser would have backward slanted surfaces, and there will be forces distributed on these two surfaces (I guess you should disconsider complex interfaces between the riser and the limbs, such as Mathews V-notch).
If you decompose these two forces, their vertical vectors would cancel each other (much like the concept behind parallel limb design), and the sum of the horizontal vectors would be equal to the hand pressure that I mentioned previously.
Of course this is pretty much statics.

Something else you might want to do, is to consider that the imaginary limbs are attached with bolts, and to calculate the size of the bolts/threaded holes based on the shear stress and longitudinal stress that develops (I guess you can think of the limb as a pry bar of a certain length on which you apply a certain force, in order to pull the bolt out from underneath its head). This type of calculation you can do without the help of CW.

If you have to go into dynamics and vibrations (depending on your curiculae), that's a different story, as I imagine that you would have to model the actual releasing of an arrow, or better yet a dry shot, and I don't know much about that. I wish I could.

Regards,
Liviu


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## Keystone Killer (Sep 5, 2009)

I need some help from the members:

I am starting to get the basic design of my riser. Nothing modeled in SW/PE yet, but I hope to begin ASAP. I need to get some basic geometry from a riser that accepts the universal limbs. Any body have the ability to get angles, dimensions? I had a user that offered to send me some data, but im unable to get in touch with him and I need to continue forward. Otherwise i have to buy one and check.... 
(poor college guy here)


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## bowhunterprime (Jan 28, 2009)

Would a Martin Jaguar Take Down riser work? If so then I have one and I could measure anything on it that you need to know. -Chris


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## jb12string (Sep 20, 2009)

Have you tried checking with any of the manufacturers?


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## Keystone Killer (Sep 5, 2009)

Bowhunterprime, it would probably suffice. From what i gather, most newer recurve risers are. I'll need as precise info as i can get. Do you have dial calipers?

jb12string I didnt check with them, not sure who to contact. thanks for the tip though,ill have to look into it. SC PA huh? Same here.


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## Bear Bow (Oct 9, 2008)

I would contact Bear Archery one of the longest lasting companies in the business. They may be interested in helping.

As a PE in civil engineering this is cool stuff. I design bridges and structures all the time. I have been tinkering with this idea of a bow but never done it. This has sparked my interest as well. Keep us posted.:thumbs_up


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## Liviu (Oct 20, 2009)

Keystone Killer said:


> I need some help from the members:
> 
> I am starting to get the basic design of my riser. Nothing modeled in SW/PE yet, but I hope to begin ASAP.


Hi,

I am currently designing a shooting machine with scrap parts off an old nibbling machine that we had laying around at work.

For this, I had to model my bow to see how it works (of course just in a 3D environment).

It is a Switchback lefthanded, and I modeled only the riser and the wooden grip in SolidWorks (2008). 
I measured it basically with a digital caliper, so it's pretty accurate.

One note, I have not removed the limbs so the pockets are just some sort of a mock-up.

If you want the model let me know.
Here is a picture of it:









A close-up with the camo texture removed.









And one of the shooting machine that I'm working on with the said riser in place:









Regards,
Liviu


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## GenesisAlpha (Jun 26, 2009)

Websters States,,

"weapon, any instrument or organ of offense or defense."

Firearms owners and Archers that hunt use their bows and guns to take game. 

We should not call the tools we use weapons. I do not use my bow in offense against a target, 3D or paper.

Wikiipedia needs to be updated it should read:

A weapon is any instrument or organ used in offense or defense that is used or acted upon by a human against another human with the intent to injure or take a human life.

Such weapons could be, Golf Clubs, Baseball Bats, Baseballs, Hockey Sticks, Pucks, City Bus, Imported or Domestic Motorized Vehicles, Hair Dryer and many other articles that could be used as a weapon.

Sorry for the rant....................

I hope the project is a success.:thumbs_up


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## Keystone Killer (Sep 5, 2009)

Bump, 
The project is ready to be started. Looking for help with Geometry of universal limb pockets and how to get this in solid works.


Its a full fledged project starting now, has to be ready to go for May 2010!


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## amcardon (Mar 17, 2009)

So May has come and gone; what happened with the project?


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## jlsug (Dec 15, 2006)

try this web sight, he built his own compound, do search for lientz bow


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