# 3D-Printed Rambone w/ Bigger Forks (for wider bands)?



## calinb (Apr 4, 2015)

The middle photo is my 2nd 3D-printed Rambone (printed in nylon like all my other homemade slingshots so far). I printed it in two pieces, because the Rambone doesn't have a large flat surface to adhere to the printer bed (necessary for nearly every home FFF/FDM 3D printing material except maybe PLA), but I moved the split that bisected the forks in my first print to the plane of the front face of the forks. The front part is now a totally ergonomic and aesthetic piece and does not support the forks. The Plastite screws holes moved a bit too.

In Bill Hays' video review of the Rambone, he said he would have preferred wider fork prongs to attach bands without the bands extending so far off the sides. On the other hand, I watched Joerg Sprave's "Instruction Manual" video for the Rambone and it's clear that Joerg intended for bands to hang over the sides. He even demonstrated how to spread medium to narrow width double band set bands apart to get flat band overhang.

I don't know which is best, but I'm exploring fatter forks to enable the no tie, no tools band attachment method (http://slingshotforum.com/topic/14592-the-ott-no-tie-no-tools-band-attachment-method/). This method should help with the Rambone hand slap, which Bill Hays also mentioned as a negative of the Rambone.

Lacking a solid model for the Rambone, I managed to hack the mesh model. With increasing width comes ugliness, I think, but fat fork prongs should work. Slot width for each fork style is shown in the CAD screenshot.


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## SlingshotBill (May 29, 2014)

That sounds like a Neat test I wonder if it will weaken the design because Sprave puts like 300 pounds of pull on the regular one . My rambone has gone through many sets of bands and I shoot the 1.29in TBG(which it came with) better than 3/4in .030 latex or 1/2 lentex with marbles and 3/8 steel.


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## calinb (Apr 4, 2015)

SlingshotBill, I think my 3D printed nylon Rambone would hold 300 lbs, but maybe not if I cut out the slots for tubes. It might not make it to 300, if I slot the forks for tie-FBs either, but a wider prong should help gain back a little strength. I have a bunch of 25 lb. bags of lead shot. Guess I'll just have to test it someday.

My 3D printed Rambone will never be as strong as the commercial glass filled nylon and polycarbonate models but it is strong enough. Hmm--maybe once I upgrade the hot end in my 3D printer so it can handle 300 F temps for printing polycarbonate, I'll be able to match them. Polycarbonate reportedly prints without layer to layer bonding weakness, like PLA, but it is much, much stronger than PLA and very impact resistant too. It is also reportedly a very challenging material to print!


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## calinb (Apr 4, 2015)

My big question for a slotted tie-less Rambone is how much space is needed in front of the slot to reduce or eliminate hand slap? Does it even matter? Leaving space in front of the slot/band means less material is available behind the band to support the pull of the band. See my post in this thread:

http://slingshotforum.com/topic/14592-the-ott-no-tie-no-tools-band-attachment-method/page-4#entry529422


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## SlingshotBill (May 29, 2014)

I got a earlier model so i think its the same material your using and its my was my first ott so it can take a lot of fork hits.


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## calinb (Apr 4, 2015)

I think your Rambone is injection molded glass filled nylon. It's a very strong plastic and impact resistant--comparable to the newer polycarbonate option. Glocks and other "plastic" handguns are made with injection molded nylon frames.

I noticed both Rambones are still available on Sprave's European webstore. For a slingshot, it really comes down to which finish do you prefer--the glossy polycarbonate or the flatter finish nylon and whether you prefer the excellent solvent resistance of nylon (just about nothing attacks nylon--only some strong acids). However, you can't paint nylon, but you can dye it with Rit clothing dye in most cases.

My 3D printed nylon isn't as strong as injection molded nylon, because it doesn't have the glass in it. Also, even though I print my nylon plenty hot, it still suffers a little from "grain weakness" between the printed layers. Optimally printed nylon actually requires temps that lie above the limit of many 3D printers so I think the nylon filament vendors tend to understate the temperatures required to print their products. I can easily print up to 270 F, which I've found to be hot enough in my destructive testing.



SlingshotBill said:


> I got a earlier model so i think its the same material your using and its my was my first ott so it can take a lot of fork hits.


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## calinb (Apr 4, 2015)

I just installed a set of Trumark black bands on the Rambone and shot it in TTF configuration. The pull is too heavy for me to shoot well (I can't pull much past my cheek). I uploaded a photo of it and some of my other 3D printed nylon slingshots here:

http://slingshotforum.com/gallery/album/1972-3d-printed-nylon-slingshots/

Originally I got the black tubes to shoot 2oz and 4oz lead fishing weights on pull lines over tree limb for pruning with a survival saw. I never needed them (even to shoot over 50' up). They are heavy tubes for a beginning shooter like me!


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## BAT (Feb 26, 2015)

Great work!! I like the 3D printing world, are you modeling in Solid works? do you have pictures of the print progress? or pictures of a cutout of the model? I understand that you cannot make a solid model, so you need to make cavities, like a honey comb, to give strength to the final piece.

Cheers!!!


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## calinb (Apr 4, 2015)

BAT, I made a solid model of Bill Hays' Boy Scout. You can check out my thread about it and photo album:

http://slingshotforum.com/gallery/album/1972-3d-printed-nylon-slingshots/

http://slingshotforum.com/topic/42458-my-scouting-family-of-3d-printed-boy-scouts/#entry527280

I wish I had Soldworks! I'm using Geomagic (formerly Alibre) but the bugs become irritating as a design grows. For 3D printing, I'd consider Design Spark Mechanical, because it is free (as in beer--that is, it's free to use), but it can't import and export anything but mesh models. Design Spark does seem to be reliable (it's based on Spaceclaim), but I prefer a sketch history based CAD tool. Maybe you are familiar with CAD tools and have your own favorites.

For the Rambone, I just downloaded the mesh model (.stl file) that Joeg Sprave kindly provides. There's a link here:

http://simple-shot.com/build-your-own-rambone/

However, for FFF/FDM desktop hobby printers, the Rambone mesh really needs to be split into two prints, so I hacked the mesh file using netfabb, Wings3D, and Blender.

The honeycomb core is created by the 3D printing slicer software (I used Kisslicer for my slingshots). A large solid 3D printed part doesn't work any better than an injection molded part without cavities. The plastic is too thick and it shrinks too much when it cools--especially when printing nylon!

I'll try to post some screen shots of the Rambone CAD and maybe get some photos from the build next time.


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