Swappable launch lugs and rail buttons?

[WizardOfBoz]

I'm building (more accurately will build) the latest release of the Estes Nike Smoke. Because that kit's nosecone has a larger diameter than the BT, that kit includes launch lugs which are standoff. I think 1/4" rail, IIRC.

The standoffs are fairly cheaply made. Essentially just a shell that you are supposed to CA glue to the body. The pic below shows the installation. I would prefer to have removable lugs, allowing me to screw on stand-off rail buttons. In this way I could launch the thing from a 1/4 rod (which I have) or from a 10 series rail (which I plan to get but don't yet have). The standoff actually has advantages here, as one could (if the lugs were solid plastic) drill a hole (to allow a screw head to fit through) through the lug, and a smaller hole (allowing the screw threads to pass) through the standoff base.

For launch rails I think I can use the standoff rail guides from Apogee (shown), drilling a mounting hole through the center of the thing. There are also metal models (Acme Engineering aluminum conformal launch lugs) but the 1/4 inch rod design with offset that I want is conformal to a 38mm tube. With some sandpaper and a 3" OD PVC tube I could probably get the thing conformal to a 3" BT.

I would have thought that swappable launch lugs would be a common thing but I guess not.

This underscores the fact that I need a 3D printer....

 

[Pinetree]

Me personally, I would put the buttons on one side, and the lugs on the other.

 

[WizardOfBoz]

That would work, but ... I'm an engineer. I live to optimize...

 

[Art Upton]

I would not want anyone to fly a 3" rocket or larger on a launch rod anymore. Many RSOs would allow it.

My Orange Nike Smoke has railbuttons.com on it, and it works fine on the rail with no standoff needed.

 

[Pinetree]

I fly my DBRM from a 1/4" rod on a F15-4 without a problem.

 

[WizardOfBoz]

Art, Thanks for sharing insights from your experience. I have a 6' 1/4 rod that I could actually launch the thing using an F15, on the field next to my house. ~500 foot apogee. I am in the process of finalizing my design for a launch rail, but it's not complete. So there's an incentive for having the lug option. But if I need to make a choice it sounds like a rail button is the way to go.

 

[troj]

The reality is that the hobby has basically moved away from launch rods for anything larger than standard Estes-sized rockets. Thus, there's not really any demand for what you're asking for.

Are there still some folks using 1/4" and larger launch rods? Sure. Are they very much a minority at this point? Yep.

All that said, if I were trying to solve this "problem," I'd probably try to take a longish launch lug and put a hole through the "top" of it large enough for the screw head to fit through, then a hole through the bottom for the shaft of the screw, and countersink it. That way, you can put a screw through the lug and not have it interfere with the rod sliding through.

Obviously, you'll need to use a launch lug with a thick enough wall to allow that countersunk screw head to hold.

 

[techrat]

Go for the rail buttons. And make sure they are mounted securely.
If you absolutely MUST add a launch lug, tape it down with masking tape that goes completely around the body tube and then remove after the flight.

 

[WizardOfBoz]

Go for the rail buttons. And make sure they are mounted securely.
If you absolutely MUST add a launch lug, tape it down with masking tape that goes completely around the body tube and then remove after the flight.

Ah, brilliant. Thanks.

This brings up another issue. Rail buttons seem to come in two flavors. In one, the ID of the hole is sized for the barrel of the T-nut which protrudes from the body tube. In the other, the hole is sized for (essentially, what is) a wood screw and there is nothing protruding. I like the idea of the rocket having no protrusions (if I wanted to launch using a cage-guided system) but I want a machine screw and not a wood screw, so I use a t-nut, inserted into a piece of wood shaped to the body tube, with little or no protrusion. This is epoxied in. Then I use the second type of rail button (small hole) and a screw to fit the t-nut. The wood support is shaped and smoothed to avoid holding up any recovery stuff. Feel free to criticize or comment.

 

[troj]

Ah, brilliant. Thanks.

This brings up another issue. Rail buttons seem to come in two flavors. In one, the ID of the hole is sized for the barrel of the T-nut which protrudes from the body tube. In the other, the hole is sized for (essentially, what is) a wood screw and there is nothing protruding. I like the idea of the rocket having no protrusions (if I wanted to launch using a cage-guided system) but I want a machine screw and not a wood screw, so I use a t-nut, inserted into a piece of wood shaped to the body tube, with little or no protrusion. This is epoxied in. Then I use the second type of rail button (small hole) and a screw to fit the t-nut. The wood support is shaped and smoothed to avoid holding up any recovery stuff. Feel free to criticize or comment.

I'm done similar - I find the internal piece of wood helps providing a larger bearing surface for the rail button attachment, as well.

 

[David_Stack]

I want a machine screw and not a wood screw, so I use a t-nut, inserted into a piece of wood shaped to the body tube, with little or no protrusion. This is epoxied in. Then I use the second type of rail button (small hole) and a screw to fit the t-nut. The wood support is shaped and smoothed to avoid holding up any recovery stuff. Feel free to criticize or comment.

Inverted Pursuits Lab has picked up the formerly Lab Rat Rocketry line of products, among which are 3-D printed internal conformable rail button nuts. See https://inverted-pursuits-lab.squar...true&sa=false&sbp=false&q=false&category_id=9 for an example...

 

[les]

Here's what I did for some of my older rockets that had 1/4" lugs and wanted to switch to buttons. In all cases there were two lugs separated by a distance.
I got a 1/4" wooden dowel (depending on the play maybe even a slightly larger dowel) and drilled a hole through the top of the lug into the dowel, typically the midpoint of the lug length. The dowel then got tapped for a #6 screw. The button then uses a #6 screw with the button through the lug into the dowel. It does offset the button from the tube by the lug diameter, but I have not had any issues with that so far. And if I want to go back to the lug I can just unscrew the button and slide the dowel back out of the lug. And the dowel is more grab for the screw than just the thickness of the lug.

 

[WizardOfBoz]

Go for the rail buttons. And make sure they are mounted securely.
If you absolutely MUST add a launch lug, tape it down with masking tape that goes completely around the body tube and then remove after the flight.

I saw an ad for what I presume to be launch rail guides that you affix with rubber bands. It comes with 2 of each: plywood extension, rail button, and screw. With an assortment of rubber bands. Tho I think your idea of masking tape would be better.
https://www.erockets.biz/erockets-lug-to-rail-button-1-4-erx-9152/?setCurrencyId=1&sku=ERX 9152

 

[bjphoenix]

Our club usually sets up more rails than rods for MPR but we have plenty of rockets that launch on 1/4" rods with no problems. It was many years ago but my level 1 rocket launched at the same club used launch lugs.

To the OPs question- since the Nike Smoke requires a standoff I envisioned a couple of small wooden blocks that glue to the body tube, then you can screw a button into them. Or you could glue a launch lug to a piece of popsicle stick and screw it onto the same little wooden platform.

 

[Pinetree]

At our last launch, a guy was looking around the pads for something he'd lost..

Turned out, it was one of those things pictured above.

Apparently the rubber band had come off.

 

[Art Upton]

Here is my Orange 'Smoke with standard rail buttons and it does not need a standoff. If you wanted a bit more clearance on that nose, then you could add an extra Delrin washer to the bottom of the rail button if you were worried about scuffin' any paint on the nose. My Orange 'Smoke does not have any paint on the nose to chip off, the factory white is fine for me.

Also on my 4' rail that is being used, it fits into my Pad's "Chuck" just like a launch rod does. I also have Mini and Micro Rails and buttons for my newer Model Rockets as I just don't like launch lugs anymore except on throw away launches. I paint my models before the rail buttons go on.

You can see the screw in rod at the bottom of the rail that allows it to be put in the launch pad's "drill chuck". Those Chucks are about $8-12 on Amazon. I recommend rocket folks to get their own rail for launches in the local fields for anything but the smallest of rockets.



Flash Shadow of button on the yellow rocket in the traveling rack


Screw in rod from Lowe's screws into center hole on the 4' 1010 rail. [I have a 6 footer as well, plus the link to make 10' with both] but they mount into a much larger pad.


This "Small Pad" will hold the micro, mini, and 4 foot 1010 rail just fine in it's 'Drill Chuck" seen under the blast plate.

See Fred at "Fade To Black Rocket Works" , he will make you a small custom pad or one of his stock pads. He is a very good friend of mine and will be taking me to the JMRC launch on the 20th so I can fly my Enerjet Orange 'Smoke again !

 

[Capt. Eric]

I saw an ad for what I presume to be launch rail guides that you affix with rubber bands. It comes with 2 of each: plywood extension, rail button, and screw. With an assortment of rubber bands. Tho I think your idea of masking tape would be better.
https://www.erockets.biz/erockets-lug-to-rail-button-1-4-erx-9152/?setCurrencyId=1&sku=ERX 9152

View attachment 656059

I have a set of these and used them once. I did add a small washer or 2 to raise the button more clear of the lug, then CA the screw into the wood to hold it better. I also used a rubber band to secure it well by passing the band over the wood base, through the lug, followed by the wood base, around the lug, and back up the outside and over the base again. A thin strip of tape around the lug wouldn't hurt either, as long as everything is clear of the button and rail. It worked well, and with careful securing to the lug, it should work fine.

While I bought mine (I think I was at erockets at the time) it would be easy enough to make it yourself with a button and scrap of wood.

 

[dhurstell]

That would work, but ... I'm an engineer. I live to optimize...

What about something that uses the railbutton holes, and you just swap out a standoff rail w/ lugs?

(Forgive the bad model, i just whipped it up for this post, and im new to CAD)

 

[WizardOfBoz]

@dhurstell this is similar to what I was thinking. By connecting the two lugs you ensure alignment.
I'm thinking of something a little different. I'm going to have to figure out Fusion 360 I think...