Rail Buttons for a G-impulse rocket

madcow rocketry
SilicdyneTRF
The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
K

KzJ

New Member
Joined
Aug 11, 2023
Messages
4
Reaction score
2
Location
New Zealand
I'm looking at making my own rocket that I'd power with an Aerotech G125, G80 (harder to get for me), or G72. I've got this model of approximately what the rocket would look like. The rail inserts (or buttons) are scaled to match a 20x20mm aluminium track I can purchase. Given these proportions would these be of a suitable size that would not cause too much drag or torque? Thanks.rocketMockup4.pngrocketMockupTop.pngrocketMockup2.pngrocketMockup.pngrocketMockup.pngrocketMockup2.pngrocketMockupTop.pngrocketMockup4.png
 
It might be ok. A 1010 rail may be better suited for that rocket size. Unless your club only has that 2020, or if you can get a better deal on a 2020 over a 1010. A lot of people will use 1010 or 1515. 2020 would be for a very heavy rocket I believe. I'm not sure most clubs would even use 2020 regularly.

Here's a link to an older thread on here. I would just read that thread and not post or open it(its been dormant for some time), and someone will chime in over here. I'm personally at the point im building(again) a 1010 rail for testing around my local area for all my composite motor rockets. From the Big Daddy up to my Mega Der Red Max. And then the club will have a 1010 rail foe launches.

https://www.rocketryforum.com/threads/when-to-consider-15-15-rail-vs-10-10.168233/
 
1010 buttons are common and the rails are used by most (if not all) rocketry clubs. Only if your rocket is more than 100 pounds would you need a 2020 rail. And I doubt you're flying a 100 pound rocket on a G80. The motor would just fizzle and the rocket wouldn't even budge.
 
Thanks for the link @86mustang408w

All they had in the olden days before I left were Black Sky Rail Guides and I used to bring my ProRail to launches so I had a Rail to use.

I had no Idea there were rail guide sizes until recently and I had to ask before my first AARG launch if I needed to bring a rail :)

All my rockets have BSR Rail Guides which fit the 1010 rails.

Anyhow, good stuff and thanks again !

-- kjh
 
20x20mm is smaller than 1010 rail, which is 1 inch by 1 inch. Those buttons still look really large on that what appears to be 29mm minimum diameter rocket. I am working on buttons for MakerBeamXL rail, which is 15x15mm. Buttons are pretty small. They may be used with some BT-55/56-sized stuff and up to BT-80 if it's not too powerful. Will probably go to 1010 size and use the club rails for 3 inch and more powerful 2.5/BT-80H rockets.

My 29mm MD and some BT-55/56 rockets will use a tower. 38mm MD rockets will use a bigger, taller tower. For the motors you're talking about and what appears to be an MD airframe, I'd look into a tower. It doesn't need to be very long to allow those motors to get the rocket up to a safe speed to be released.
 
Last edited:
I'd either go 1010 or consider fly-away rail guides if that's really a MD bird
 
1691989858493.pngthis is essentially the rail I would be using. The 20x20 is in mm, not 10ths of an inch, as @SolarYellow mentioned. The rail buttons that I modeled have essentially the same cross section as the negative space in the rail in the image here.
 
KzJ said:
View attachment 598072this is essentially the rail I would be using. The 20x20 is in mm, not 10ths of an inch, as @SolarYellow mentioned. The rail buttons that I modeled have essentially the same cross section as the negative space in the rail in the image here.
Click to expand...
One thing to note is the mini buttons from rail-buttons.com won't work with that rail -- they're designed for 80/20 Series 20 rail, which has a smaller gap (only a little over 5 mm vs the 6.2 on this rail). That's fine as long a you're making your own buttons, not so good if someone else would like to launch off your rail.
 
JoePfeiffer said:
One thing to note is the mini buttons from rail-buttons.com won't work with that rail -- they're designed for 80/20 Series 20 rail, which has a smaller gap (only a little over 5 mm vs the 6.2 on this rail). That's fine as long a you're making your own buttons, not so good if someone else would like to launch off your rail.
Click to expand...

Drawing here:
https://8020.net/20-2020.html
 
Wow, this does get confusing.
All that said, in the original 3D model of the rocket, the rail guides looked enormous compared to the rocket, like using 1/4" launch lugs on an Estes mosquito.
 
Rail guides don't typically fill all of the negative space in the rail. Try slimming them down, so that they solidly engage with the slot without being too big.

A 20mm rail should be pretty much perfectly suited for a midpower rocket like this.
 
Good point. I downloaded the 8020 catalog and looked at the differences between the dimensions of the 1010 rail and the 1010 rail guides they sell, after the latter were discussed here a short time ago as working really well for rail buttons. Used that as a reference point and starting guideline. Tightening things up a little for the MBXL 15x15mm rail, but not much.

Also, the whole idea behind my MBXL guides is aero. They are going to be as aero as I can figure out how to make them without doing CFD or other silliness. I'm kind of surprised how many really non-aero rail guides/buttons this hobby puts up with just because they are really easy to fabricate. Try with and without them in your sim software.
 
tfish said:
the 20x20mm is "mini rail buttons

https://rail-buttons.com/ocart3/index.php?route=product/category&path=65_61

I've flown up to I motors on mini buttons.

I use the micro buttons for Estes rockets..

Tony
Click to expand...
Thanks Tony !

My 200 gram, glassed BT-55 scale Vulcanite is ready to fly a Blue Raven in DD Mode except for rail buttons.

EDIT: oops 0.438 came from OR measured with calipers at 0.375 inch OD ...

But I just couldn't bring myself to install 0.438 0.375 inch 1010 buttons on a 1.325 inch diameter rocket:

LPV-34-1010-rail-button-20230815_040135-crop.png

The Black Blobs between the ruler and the rocket are standard 1010 buttons.

I've done some research based on your post and I've decided to go with mini rail buttons from railbuttons.com along with an 80/20 20mm rail which I can temporarily attach to my BSR ProPad.

I feel much better about 0.249 inch rail buttons but I really need to think about a tower one of these days.

Thanks again Tony !

-- kjh
 
Last edited:
kjhambrick said:
Thanks Tony !

My 200 gram, glassed BT-55 scale Vulcanite is ready to fly a Blue Raven in DD Mode except for rail buttons.

EDIT: oops 0.438 came from OR measured with calipers at 0.375 inch OD ...

But I just couldn't bring myself to install 0.438 0.375 inch 1010 buttons on a 1.325 inch diameter rocket:

View attachment 598244

The Black Blobs between the ruler and the rocket are standard 1010 buttons.

I've done some research based on your post and I've decided to go with mini rail buttons from railbuttons.com along with an 80/20 20mm rail which I can temporarily attach to my BSR ProPad.

I feel much better about 0.249 inch rail buttons but I really need to think about a tower one of these days.

Thanks again Tony !

-- kjh
Click to expand...
Might be helpful..

https://www.rocketryforum.com/threads/i-blew-it-rail-for-rail-button-selection.162391/#post-2061486
Tony
 
If you're worried about drag, consider a fly-away option. You could build a "cage" that splits in half after the rocket leaves the rail (via spring release), and then you don't have any launch lug or rail guide on the rocket itself. This is common in high altitude attempts. On Youtube, there's a Xyla Foxlin video about her rocket "spite" that uses this method and she gives the fly-away cage a few minutes of screen time.
 
techrat said:
If you're worried about drag, consider a fly-away option. You could build a "cage" that splits in half after the rocket leaves the rail (via spring release), and then you don't have any launch lug or rail guide on the rocket itself. This is common in high altitude attempts. On Youtube, there's a Xyla Foxlin video about her rocket "spite" that uses this method and she gives the fly-away cage a few minutes of screen time.
Click to expand...

I dunno. The more I use the FARGs, the less I like them. They have more friction than mounted buttons, and weird things can happen when they release, like knocking the rocket off-course. For altitude attempts, you need a clean rail departure and low drag, ie a tower.
 
Buckeye said:
I dunno. The more I use the FARGs, the less I like them. They have more friction than mounted buttons, and weird things can happen when they release, like knocking the rocket off-course. For altitude attempts, you need a clean rail departure and low drag, ie a tower.
Click to expand...

I think they also have to have more friction than a regular tubular launch lug. How do they fly away if there isn't tension on them? That tension leads to drag on the rod.

I've also been thinking about playing with piston launchers for small sport rockets. A little fiddlier, but if you get it dialed in, you can get good, straight launches with reasonably a ground equipment setup that is much cheaper and simpler to build than even a small tower - and no launch lug. I hate everything about launch lugs. They add weight and drag, and making them suck as little as reasonably possible with fillets and painting adds a disproportional amount of build time. They even interfere with finishing the fins well. They just suck all around.
 
SolarYellow said:
Also, the whole idea behind my MBXL guides is aero. They are going to be as aero as I can figure out how to make them without doing CFD or other silliness.
Click to expand...

Nothing silly about using CFD. It is the perfect tool for multiple design iterations and to accurately measure/visualize the differences in drag. Can you really attribute the differences in drag between a hollow lug, round button, or launch shoe (RASAero term) from noisy flight tests? I doubt it.
 
I've not flown a FARG but I bought one to try with a 200 gram rocket.

I decided to not use it because of the friction drag in my 1010 rail when I tried sliding it along the rail.

And also because the rocket has to lift the mass of the FARG gadget from liftoff to release and I'm not convinced there will be a net gain using a FARG over the aero drag for mini or micro rail guides.

YMMV ... I've got no real data, just my gut feelings ...

-- kjh

EDIT: I just realized I am repeating myself ... I was referring to the 200 gram rocket in post #14 above ... it sucks getting old ... :)

My mini buttons are on the way and based on @tfish's posts, she should be good for anything from a D-Motor thru an I200 ...
 
Buckeye said:
Nothing silly about using CFD. It is the perfect tool for multiple design iterations and to accurately measure/visualize the differences in drag. Can you really attribute the differences in drag between a hollow lug, round button, or launch shoe (RASAero term) from noisy flight tests? I doubt it.
Click to expand...

In principle, no, there is nothing silly about using CFD. But I don't have a package and don't know how to use any of the software anyway. On the other hand, I've been doing aerodynamic stuff as a hobby my whole life and can reasonably apply the proven principles and guidelines that are in established and respected literature to the problem of a rail guide quite effectively. I'm quite sure I can generate something that would be far better than a round button that way. Frankly, if it's done with sufficient attention to detail that I can't just look at it and know what I'd want to change, that's good enough to make me happy on this project. What kind of surprises me is that the field seems to be more or less wide open to innovate something better in this area when I'm this late to the party.
 
SolarYellow said:
In principle, no, there is nothing silly about using CFD. But I don't have a package and don't know how to use any of the software anyway. On the other hand, I've been doing aerodynamic stuff as a hobby my whole life and can reasonably apply the proven principles and guidelines that are in established and respected literature to the problem of a rail guide quite effectively. I'm quite sure I can generate something that would be far better than a round button that way. Frankly, if it's done with sufficient attention to detail that I can't just look at it and know what I'd want to change, that's good enough to make me happy on this project. What kind of surprises me is that the field seems to be more or less wide open to innovate something better in this area when I'm this late to the party.
Click to expand...

You may find these interesting:

https://www.apogeerockets.com/Build.../Rail_Buttons/Standard_Airfoiled_Rail_Buttons
https://www.apogeerockets.com/downloads/PDFs/launch-lug-drag.pdf
 
SolarYellow said:
In principle, no, there is nothing silly about using CFD. But I don't have a package and don't know how to use any of the software anyway. On the other hand, I've been doing aerodynamic stuff as a hobby my whole life and can reasonably apply the proven principles and guidelines that are in established and respected literature to the problem of a rail guide quite effectively. I'm quite sure I can generate something that would be far better than a round button that way. Frankly, if it's done with sufficient attention to detail that I can't just look at it and know what I'd want to change, that's good enough to make me happy on this project. What kind of surprises me is that the field seems to be more or less wide open to innovate something better in this area when I'm this late to the party.
Click to expand...
Apogee's Tim Van Milligan published a NARCON Paper in 2017 with data about launch lug, rail button and rail guide drag.

Drag of Launch Lugs, Rail Buttons, and Launch Guides

I have scanned the paper but have not read it ...

-- kjh

EDIT: dooh ! @Buckeye is quicker than I !
 
I have a set of metal, teardrop-shaped 1010 rail buttons made by "SC Precision". The teardrop shape is supposed to reduce drag somewhat. Haven't used these in any of my builds yet, but perhaps over the winter as I have a "build pile" to keep me busy during the cold, dark months I am trapped in the house.
 
Buckeye said:
You may find these interesting:

https://www.apogeerockets.com/Build.../Rail_Buttons/Standard_Airfoiled_Rail_Buttons
https://www.apogeerockets.com/downloads/PDFs/launch-lug-drag.pdf
Click to expand...

I have read that paper and am aware of those products. As Apogee notes, you can make big improvements just by putting a round on the upper corner. What about rounding all three edges? What about using a more-aero "airfoil" section?

1010 rail buttons are much bigger than they need to be for my rockets. With a resin printer, I can make an even more aerodynamic shape that is smaller to work with the MBXL rail I have. I have not seen any aero buttons for MBXL rails.
 
kjhambrick said:
Thanks for the link @86mustang408w

All they had in the olden days before I left were Black Sky Rail Guides and I used to bring my ProRail to launches so I had a Rail to use.

I had no Idea there were rail guide sizes until recently and I had to ask before my first AARG launch if I needed to bring a rail :)

All my rockets have BSR Rail Guides which fit the 1010 rails.

Anyhow, good stuff and thanks again !

-- kjh
Click to expand...
No problem. Sorry It took so long to respond my phone doesn't give me notifications...lol..
 
kjhambrick said:
no worries, @86mustang408w !

This is supposed to be for fun and education :)

-- kjh
Click to expand...
Yes, lol!! Got my rail buttons on SBB. It was hard with this build the way I did it to get them lined up but this will work. Its hard with the camera to get a good view that doesn't look odd, lol.
 

Attachments

  • 20230822_100131.jpg
    20230822_100131.jpg
    1.2 MB · Views: 0
  • 20230822_100425.jpg
    20230822_100425.jpg
    1.1 MB · Views: 0

Similar threads

B
Misumi 15mm rail vs Makerbeam 10mm rail
Replies
0
Views
169
BMcD
B
duodenumnums
1.6" diameter--rail buttons or not?
2
Replies
43
Views
3K
duodenumnums
duodenumnums
K
Spock's Johnson Rides a Twenty Eight Year Old I357T and Lives !
Replies
0
Views
264
kjhambrick
K
Last Ox
Velocity off the Rail - NRXS Data
Replies
2
Views
628
kjhambrick
K
burkefj
Wolverine 2.6x upscale R/C rocket glider
Replies
14
Views
680
burkefj
burkefj

Latest posts

Back
Top