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Firebird

Youth Compound Bow

by Firebird Sep 9, 2014
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hi. How are you? what power has??????

how the cable will attached at the marked place? it's impossible to do!

Hi, I am sorry you are having trouble.
The area you have pointed to on the attached image is not where the cable attaches, it is attached on the other cone feature.
Please have a careful look at the diagrams and instructions for the correct cable and string placement.
Kind regards
Roger

Hi, can you post in the "Individual_riser_parts.zip" the parts that fit the limbs in the riser? Thanks, great job

First, congratulations for this creation, I'm on my way to make one. Regarding making, I have one question, though. I really would like to try scaling it up to fit an adult size (milled on aluminum), even without making certains areas thinner (as you said in a previous comment, to save weight). So, how much in % should I scale up in order to fit adult size, if possible? If so, the strings should be lenghtened at the same proportion?

The short answer is yes. whatever percent you scale the bow up by should be applied to everything, even the lengths of the strings.

But! I gotta say that this bow was drawn up around the proportions of my children. I did use my full size bow as inspiration but the proportions have not been scaled down equally. For one, the riser is shorter than it should be.
To give you an idea, my bow has a 31" draw length and the youth bow has a draw length around 25" this should work out to an 80% scale but the riser on my bow is 780mm from tip to tip so the youth bow riser should be (780*0.8=) 624mm, instead it is 540mm. The same applies to the limbs, the cams, the string lengths etc. I had to work all of the geometry out individually to fit my kids and it was not easy but it was a very rewarding challenge to work everything out.
It is also worthwhile to note that the width was not scaled down because the bow needed to fit off the shelf sights and rests.
It is a working system though so you should be able to scale the youth bow up proportionally. This is the easiest way to do it but the resulting bow will be heavy and not very powerful.

Okay so all of that said, the best way to scale the bow up would be to size the bow around your draw length. More info here: http://www.huntersfriend.com/compound-bow-fitting-draw-length-draw-weight-help-guide.html

If you want a ballpark to start with. The youth bow as it is now has an adjustable draw length from 24" to 25".
This is measured from the arrow rest (center point above the handle) to the nocking point on the string at full draw.
So lets say you have a draw length of 29", your bow will need to be 116% bigger or 1.16 times bigger (29/25=1.16)
If you then apply that same scale factor to everything else, including the strings, the geometry should scale up to fit you perfectly. The cam geometry should also scale up properly like that. Good luck and don't forget to post pics of the results.

I would like to thank you a lot for taking your time explaining in order I can have some good basis to start. I'll follow these tips as best as I can. Actually, I did some reading, and I casually found the page your linked in one of my readings (I guess this is a good sign, lol). I'll probably take more time doing a bit more research on materials I have available where I live. Today I thought making the riser in one piece of wood, reinforced with a cover of fiberglass (both materials I'm familiar with), and the limbs made of fiberglass with milled aluminum cams) using the scaled up version as a template. When I have something ready and working, I'll shoot a message. Archery seems to be a beautiful sport and practice, so I think it's worthwhile.

I think wood and fiberglass is a great combination, it will be light and strong. The 'bulky' layout of the riser for the youth bow will suit this method of construction well. I am please to hear the you are doing your research and yes, Archery is a fantastic past time and sport, learning all you can about it will help you build the best bow to fit you. If you are familiar with fiberglass you might even try making laminated fiberglass limbs! Please post pics as you go. I would love to see the cams in aluminium !!

Well, and that's the idea, regarding the limbs: laminate them! Let me abuse your goodwill one more time, before I begin: would you think that the most recent Tomb Raider compound bow by Silesti have potential to be functional? It have an appealing design, but as far as I read (and learned from you too), there are other intrincacies to consider other than purely the aesthetics.

Hi, I haven't really had a close look at the Tomb Raider bow but at first glance it looks to be a very accurate prop. There is something weird going on with the cables. I am not sure what that would do to the cam geometry so if it is a functional bow then I am not sure it is the most efficient design. Just my uninformed 50c, I would contact the creator to confirm. I hope you come right.

I've got everything printed. But having a hard time finding a diagram how to wire the cables. Appears you have the main cam and a smaller one looking like half moon (apologize for my lack of bow terms knowledge, none the less I can shoot :) ). Your drawings doesn't include the half moon one. Greatly appreciated.

It's no problem. The only thing I can suggest is that you carefully study the two drawings. You don't need to know more bow terminology than the names of the strings. There are three types of bow 'strings' used in this compound layout. There is the actual BOW STRING (the part that launches the arrow, this is shown as green in the two diagrams) which in this case is attached to the two CAM STRINGS (Blue) which are then attached to the two outer cams (you called this the main cam) on each of the cam wheels. The other string type is the CABLE (orange) There are two cables and they attach to the inboard cams (the smaller half moon shaped ones).If you look carefully at 'Stringing Diagram 2.jpg' you will see that the middle diagram entitled 'Cable layout' shows the attachment and routing of the two cables around the inboard cable cams. I hope this helps.
Please also note that each cam wheel is a sandwich of three cams, the two outer main cams and the half moon cam on the inside.
Please make sure you have printed and assembled them correctly.

Any reason the limbs cannot be 3d printed as suggested by one of your pictures? I am thinking using PETG for the limbs might be ok since the material is quite strong and flexible enough.

The strength of a 3D print varies greatly from machine to machine so as a general rule I don't want to endorse 3D printing the limbs.
Also PVC pipe is entirely suitable for the job and very cost effective when compared to the cost of filament.
But hey , if you wanna, then you gonna.
It will be interesting to see if nothing else. Post the results so we can all see.

Happen to have the cad files or do i need to make them myself?

Best you make them yourself.

da pra faze esse arco grande

First, thank you so much for this! Saved me a TON of time! I'm currently printing this at 1/4 scale for an action figure I'm working on, and will post pics when it's finished, but I wanted to comment to point out one thing. The only file that includes the top and bottom mounts for the limbs is the CNC plate. The .stl for the complete riser, and the folder of individual .stl's FOR the riser do not include the mounts. Not really an issue as I just went ahead and rescaled the whole CNC plate and used it that way. Just figured I would make you aware. Thanks again!

Очень хорошо!!! Дети в восторге!

Hi, did u know how long the strings must be ?

Have a look at the 4th image. The length of each string is listed there in inches and millimeters.

Did you design the sight as well?

I didn't. I found it on GrabCAD. I linked to it in the description, I think.
There are lots available there so if you don't find the link then a quick search should get you what you are looking for.

Could you design a recurve riser, I have no where near the talent with CAD software to do anything close to this.

I suppose I could.
What would you use as limbs, actual recurve limbs or PVC pipe?
If it's the former then I could copy the riser from my recurve bow when I get a gap. If you have something else in mind then PM me and I will see what I can come up with :)

i printed the riser in full scale in PLA plastic, cams in PETG with 100% infill ofc and it works :D.
so you dont need to use acrylic for riser and you dont need to use ABS for cams.
print and have fun thanks for the design ! love it!

That is good news! Enjoy
Please upload pics if you haven't already.

pics and video is up check it out :)

Instead of 3D printed riser, I decided to use PVC pipe for all main structural parts like you can see here:
http://www.thingiverse.com/thing:1755567
Shooting tests went well! Great cam design.

ArChery Cam Print All at Once - no assembly needed
by a3lex

could i 3D print this on my 200mm by 200mm by 250mm print bed on my printerbot in pla?

No, PLA is not strong enough.
As per the instructions, print the cams in ABS/Polycarb and machine the riser and limb pockets from Polycarb.

What orientation would the file with all the handle parts be and could you please post photos/ a video on the assembly

I am not sure what are asking with regards to the orientation. It is a large flat nested part. So I would think the orientation to mill would be self evident. You do have to mill the part from both side though so you need to be mark and dowel the work piece to the cutting bed accordingly.
I might post an assembly video at some point but I can't see that happening soon. I the mean time please have a look at the pages of instructions I have provided.

We need an STL of the core. People here use 3d printers, not cutters. Its a MakerBot site man.... lol

"Thingiverse is a website dedicated to the sharing of user-created digital design files
... 3D printers, laser cutters, milling machines and many other technologies can be used to physically create the files shared by the users on Thingiverse."

You couldnt print some of the pieces as they are too big and wouldnt hold up, so cut them.

is it possible to get all the parts a part and not in one stl file i cant fit them on my buld platform?

Hi Pridler, thanks for the feedback. Please have a look at the file 'Individual Riser parts.zip'
I don't however recommend printing the riser components. They are designed to be machined from acrylic.

can i scale it up to make it fit adult ?

I don't think so, the adult bow needs more strong Material neither PLA or ABS..

You are correct hackqiang. I wouldn't print this one in ABS or PLA.
My prototype is machined from acrylic which is was very strong. The second one I made in the same material and it snapped on the first draw because of a tiny stress raiser I hadn't sanded away.

@ mac969 The design could be scaled up, but I would then machine the riser from 6000 grade aluminium. To be honest, it will probably be easier and cheaper to just find a second hand adult bow on eBay. If you were to scale the design up you would have to thin out certain areas to save weight.

i printed the bow itself and found that the risers bend when you draw, which putts the cams out of line and derails the bow. would you be able to send me the ipt file so i can get measurements to make a brace? cheers

I can't send you an IPT file but you should be able to import the parasolid file into Inventor. . (in the files section, extension *.x_t) That should be all you need to made mods and trace off additional parts.

nice model. cams work really well

nice model. cams work really well

Thanks ethanbrown, I am glad you like it :)