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plainolddave

Rocket Fly-away Rail Guide V2

by plainolddave Jun 22, 2019
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Could you make a 29mm version of the rail guide?

Thanks

Comments deleted.

I have a quick question:
Can you make some small holes in the printed rail button part at the friction bearing surface that we could press small pins into? That way you could use the pins (out of stainless maybe) as the friction surface and significantly reduce the drag.

Just a thought.

Cheers!

Yep / happy to experiment. Help me understand - which orientation would the pins be? There's three surfaces on the rail that contact the guide - whats your thoughts on how to orient?

In a fully printed guide the sides of the button that are held against the opening of the channel are likely to see the most drag. I'll work on a picture in a day or two.

I tinkered with the file a little, I added built in rail buttons, eliminating the need to either print thingiverse rail buttons or buying them, as well as eliminating a nut and screw. I know that not having the metal support of a center screw might be an issue, but I made up some for that by making the rail button an oblong, to give more body for strength. I am attaching the solidworks and STL files.

Would you mind creating a 29mm version of your guide? I'm working on a 24mm RMS rocket and it would be great to try this out at that scale.

Thanks

Comments deleted.

Thanks for this - somewhat embarrassingly I've realised there's a design flaw in the original / I need to mirror the parts so they assemble correctly (sigh / my bad)

Let me fix and re-post including your updates - thanks again!

I could be wrong, but your system with A parts and B parts don't seem to work. Just making 4 A units worked fine for me. (although our launch isn't until Aug 1, so I won't know for certain until then.) Your assembly part with rods, nuts, etc just uses 4 copies of the A unit.

The main difference is on each end one of the parts has a slightly larger hole to create a loose fitting hinge (about 0.2mm additional clearance). The "B" parts are just a mirror image of the "A" parts. Reason for making the A/B versions is otherwise I was concerned that the assembly may slide apart - have added an image that hopefully explains.

All that said - more than happy to take your guidance as this is all a bit trial-and-error - its greatly appreciated!

Oh - I also updated the assembly with nuts and bolts etc (you're right - it was out of date)

I built a couple of the units, they look like they will work. What design changes did you make? I also made a version of the unit at 3.2 inch diameter, (about 81.3 mm) for a fellow rocket guy. I am attaching the STL and SW file. Sorry, it is in SW18.

Hi there - quick update / we launched a couple of F, G and H motors last weekend with good results from the rail guide (not-so-good results from the CTI Pro24 motors but that's another story).

One breakage occurred from the V2 rail guide on the second launch where the two screws grip the carbon fibre tube - looking at the design again its a bit of an obvious weak point that will need tinkering to redistribute the load imparted from friction of the buttons in the rail.

I also had a fin strike where I had placed the rail guide very close to the bottom of the rocket body - no harm other than chipped paint but might put it a little higher next time.

Overall its progress - printing with higher wall thickness (1.6mm in my case) seems to be a lot tougher - let me know how you go?

Getting a quick set of the 42mm parts printed on a resin printer. I will let you know how they go together after the launches this weekend in Eastern Oregon.

Pics after the weekend, but I don't have a rocket large enough yet. Working on that, but didn't make enough progress before this months launches. :-/

Hi - that’s interesting / the issue I’ve been grappling with is failure under dynamic tensile load.

How do you think the resin will cope? Reason I ask is I’ve tried both FDM and resin on another part (not a rail guide) and the resin cracked - for me FDM has been more forgiving in that the filaments seem to have a little bit of elasticity before they fail. My resin printed part ended up landing In a bunch of bits!

The resin I had was just Anycubic ‘dental green’ - you mind me asking what resin do you use?

I work for 3DSystems in product development. So I am using resins that are for industrial printers. It looks like TG15 (Tough Grey) should work.

I will let you know when I have settled on an OD for the low power rocket I'm currently working on. It should be in the neighborhood of 26mm, though I might just go 29mm to make it simple. I have the rail guides from Apogee that I want to test against. I had some issues at the launch event, but I think it could have been that the rails were dirty or dinged up from use.

I'll also take out my own rail next time. That way I can make sure it is in good shape.

I could have three clones and still not get everything that needs doing done... :-/