flyaway rail guides

Discussion on ground control/GSE and recovery equipment. This includes launch pads, triggers, chutes, streamers etc. Includes other items such as simulation and other computer software, etc.

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OverTheTop
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Re: flyaway rail guides

Postby OverTheTop » Sat Sep 26, 2015 1:08 pm

Put them roughly around a piece of airframe and increase heat slowly? Use something elastic to pull them in as they soften?
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Re: flyaway rail guides

Postby SpaceManMat » Sat Sep 26, 2015 1:57 pm

It's ruined, you'll need another one. Send it to me I'll take care of it for you :wink:
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Re: flyaway rail guides

Postby Lister » Sat Sep 26, 2015 3:01 pm

SpaceManMat wrote:It's ruined, you'll need another one. Send it to me I'll take care of it for you :wink:

So thoughtful mat :lol:

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Re: flyaway rail guides

Postby natty » Sun Sep 27, 2015 8:33 am

OverTheTop wrote:Put them roughly around a piece of airframe and increase heat slowly? Use something elastic to pull them in as they soften?


Yeah, thats what I'm thinking of doing, but with the buttons not even close to lining up, I'm not sure it will be right. Anyway we'll see what AMW have to say.

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Re: flyaway rail guides

Postby natty » Mon Sep 28, 2015 10:57 pm

I got in touch with William from Mayhem rocketry and he's sending me out a new set.

He said that he's got new material that wont deform. Hopefully it will get here before our next launch!!
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Re: flyaway rail guides

Postby Happy Heyoka » Thu Feb 04, 2016 10:43 pm

So, I'll hijack this thread since it's for the 24mm MD rocket @Lister is building that I'm doing this for :wink:
(for more info on that see his thread in the scratch build forum)

Just finished printing and drilling of version 2 of my take on the fly-away guide... hasn't flown yet, and maybe never will, but it's been fun as a design project. It is done as symmetrical halves... print two out, flip one, and stick a rod down the hinges.

So I added some ribs to provide stiffness and hopefully head off any de-laminating of layers (which is a hassle with 3D printed stuff).

I moved the "horns" that hold the rubber band so that the rubber band doesn't go between hinges (because that’s just going to be a problem). Also slightly further apart compared to v1 so a little bit more spring.

I added some holes, because, you know, pretty. Didn't make it any lighter but it put on a few extra grams because of the ribs. This one (complete w/brass rod) is 47g.

I am still to run it through some 1010 rail - it will be interesting to see how much PLA (the plasting) will bind vs for example the regular rail buttons/lugs. It doesn't seem more "sticky" rubbing against aluminium.

The bit of brass rod in the photos would probably have a 90 degree bend in each end to keep the thing together.

End view showing half 1010 rail slide on each side:
https://goo.gl/photos/hpDhXa2HrFk47jnH9
note that while the holes through the hinges for the rod are printed, small holes are something that doesn't work so well with my printer and they have been drilled through with a loooong 2mm drill bit

Outside view
https://goo.gl/photos/JrEWX5E2b8AMAmvh6

Inside view, callipers for dimensions
https://goo.gl/photos/UWDxgyXhBqmX4pUr7
I have sanded some of the dags of plastic off the holes here, PLA is pretty "glassy" and can be quite sharp... may have to make some design alterations for fancy paint work...

Eventually I'll post an OpenSCAD project for this - it's meant to be "parametric" - that is you put in a body tube OD and get a rail guide to suit. Other rail sizes shouldn't be a problem (and doing a rod version will probably work too)... but as I said... this hasn't flown yet... we'll get there.
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Re: flyaway rail guides

Postby Lister » Fri Feb 05, 2016 10:25 am

It may just be my phone but I cant view the photo's.. sounds cool though. I wouldn't worry too much about it scratching paint as the 24mm MD rebuild will see it with a polished gel coat and no paint. I may have to run some revised sims with some extra launch weigh as the rocket is only 60grams without motor.. do you think we can eliminate more weight?

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Re: flyaway rail guides

Postby Lister » Fri Feb 05, 2016 1:44 pm

Any ideas on how we can reduce the weight of the guide?

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Try again with the pictures

Postby Happy Heyoka » Fri Feb 05, 2016 7:23 pm

OK, so I seem to have some minor plot loss going on with uploading images... try directly:
Attachments
20160204_221711_small.jpg
Opened View
20160204_221743_small.jpg
End on View
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Re: flyaway rail guides

Postby Happy Heyoka » Fri Feb 05, 2016 9:23 pm

Lister wrote: I may have to run some revised sims with some extra launch weigh as the rocket is only 60grams without motor.. do you think we can eliminate more weight?

I'm not even sure how you sim losing mass in flight - a staging event? Tricky with one motor across the event.

I can think of a few ways of losing some weight...

#1 Trim away some of the guide - maybe something like this:
cutout sides.jpg

(incidentally, I was thinking of doing this to reduce friction on the rail lug anyway)

#2 Chop the guide up into little pieces (say three) of say a 10mm slice along the one as it stands now. So that would bring it to roughly 3/10 of 47g would be say 8 - 14g. Then separate the pieces using just wooden skewers (say 0.5g per 100mm) - six for stiffness = 3g for a total of 11-17g
three pieces.jpg

maybe instead of the skewers you could glue them onto some body tube or something.

With the 3D printing I can make them stiff/strong, I can make them thin or I can make them light (choose any two)... but I'm open to new ideas on that :D
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Re: flyaway rail guides

Postby Happy Heyoka » Fri Feb 12, 2016 11:38 pm

Just for posterity - I cut up one of the prints and measured the pieces.

Code: Select all

straight hinge         1.6g   
sliced hinge           1.3g
                       ====
one side, both hinges  2.9g   x2 =  5.8g

half rail slide        6.9g   x2 = 13.8g

brass rod              2.3g


So reducing the size of the hinges will buy a couple or maybe 3g...

The rail slide has had me worried about friction anyway, so reducing it to maybe three sections each about a tenth of the current length buys us 9.6g (well worth doing) and hopefully scratches my itch about friction.

I printed out a 1mm thick version of the clamshell with hollow ribs and that reduced the overall weight by about 14g; it did however, make the thing a bit flimsy.

Will buy some nice skewers tomorrow and play with the segmented concept.
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Re: flyaway rail guides

Postby Lister » Sat Feb 13, 2016 8:53 am

It shouldnt matter if its a bit weak, it will be wrapped around an airframe which will give it a fair bit of support, and once it leaves the rail it wont have any real stress on it so it it should work at 1mm thick.

Also what about increasing the hole size or changing them to a triangular shape to eliminate material?

I think cutting it down and replacing the discarded sections with a thin airframe section could work.

What about printing out two identical guides, but changing the length to 20mm and having each section with its own hinge.. could have a few holes in the guide to allow skewers to be secure the two guides together? Sort of like a hinged ring with a rail guide on top and a small elastic band to open it..

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Re: flyaway rail guides

Postby OverTheTop » Sat Feb 13, 2016 2:33 pm

What about printing out two identical guides, but changing the length to 20mm and having each section with its own hinge

Just check that they don't try to twist around and bind in the slot. Having the two attached allows them to stabilise each other.
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Re: flyaway rail guides

Postby Happy Heyoka » Sat Feb 13, 2016 3:07 pm

OverTheTop wrote:Just check that they don't try to twist around and bind in the slot. Having the two attached allows them to stabilise each other.


I'm going to try columns made from three sets of three skewers (with printed spacers mid length) at 120 degrees apart around the tube so the thing wont wind up (torque) on itself.

I'm sure there's a "minimum" length for the "half lug" at which one side can slip past the other in the slot, have drawings from 8020 but eyeballing everything at the moment. Been meaning to order some 1010 for another project but many backburners running...

I have done some rubbing of PLA against aluminium and it seems pretty slippery.... so hopefully it will run freely if the thing stays straight. I haven't tried printing nylon but I know it's possible; that may be a option to try if the PLA isn't slippery enough.
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Re: flyaway rail guides

Postby OverTheTop » Sat Feb 13, 2016 4:54 pm

I like the skewer idea. Low-tech version of carbon fiber rods :D
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