1515 rail questions

The Rocketry Forum

Help Support The Rocketry Forum:

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

ckjohnson

Well-Known Member
Joined
Oct 19, 2013
Messages
307
Reaction score
0
Hey everyone,

I'm getting ready to build a 1515 rail launch pad. I need a large rail for my L3, and our club needs a nice sized rail, so I'm doing it. I have a few questions about the rail though:

1. The different types of 1515 rail are 1515, 1515 light, and 1515 ultra-light. I'm trying to figure out if I need the 1515, or if the 1515 ultra-light would work. Does anyone have experience with the different types?

2. I'm deciding on whether to build a 6' rail or an 8' rail. My Hyperloc 1600 will have PLENTY of velocity leaving an 8' rail, and will have enough velocity leaving a 6' rail. There's not really a disadvantage to a longer rail as far as rocket performance, correct? The reason I am considering a 6' over an 8' is for ease of transportation. Any comments?

I'm going to build it using square steel tubing for the legs and frame. The rail will pivot down to horizontal for mounting the rocket, then stand up and bolt into the upright position for launch.
 
The difference is; how much it weighs and how much of it has been hollowed out.
https://www.ebay.com/itm/like/330941682009?lpid=82
As you can see in the corners there is a hollow.
Others are solid.
It is sold under a few brand names: 80/20 being one of them.

JD

Thanks JD, I understand the difference between the rails (some being hollowed out, etc...). It looks like they're all going to be fine for big rockets. I just wanted to make sure the ultra-light version wouldn't whip with a large rocket.

I've actually come up with a solution on it. I'm using this: https://ecx.images-amazon.com/images/I/51rN8WbXMIL._SL1000_.jpg

Now, I'm just trying to decide how long. 8' will be a pain to transport, but will give the rocket more stability at departure. 6' would be easier to transport.
 
I would go with 8', no question. If 10' is available, I would use that if this is going to be a club pad.

You said you were building it, but it sounded like it would be a club pad available to anyone else that needs that size pad. Since you can't really predict what rockets would want to use it, I suggest making it as long and solid as possible. The rail will handle almost anything you can put buttons on. The limiting factor is going to be the pad base and how solid the rail is mounted to the base. A poor base and mount may limit the pad to 30 lbs and L motors while a very solid base and mount may allow 100 lbs and N motors.
 
The two clubs I fly with have 1515 rails that are 8-feet long, minimum. For ease of transport, both are cut in half and have coupling hardware on the three sides that aren't used for the launch. It's a small nuisance to assemble and align but we've never had a failure from an operation standpoint.

As Handeman says, the base and the connection to the base is very critical. As you start laying out your ideas, share them here; you'll get plenty of feedback.
 
I would go with 8', no question. If 10' is available, I would use that if this is going to be a club pad.

You said you were building it, but it sounded like it would be a club pad available to anyone else that needs that size pad. Since you can't really predict what rockets would want to use it, I suggest making it as long and solid as possible. The rail will handle almost anything you can put buttons on. The limiting factor is going to be the pad base and how solid the rail is mounted to the base. A poor base and mount may limit the pad to 30 lbs and L motors while a very solid base and mount may allow 100 lbs and N motors.

10' is available but shipping to you is $$$$ unless you go pick it up. Kurt
 
Thanks JD, I understand the difference between the rails (some being hollowed out, etc...). It looks like they're all going to be fine for big rockets. I just wanted to make sure the ultra-light version wouldn't whip with a large rocket.

I've actually come up with a solution on it. I'm using this: https://ecx.images-amazon.com/images/I/51rN8WbXMIL._SL1000_.jpg

Now, I'm just trying to decide how long. 8' will be a pain to transport, but will give the rocket more stability at departure. 6' would be easier to transport.


Go find the technical specs and compare the Moment of Inertia values ('Ix' and 'Iy' - for the 'x' and 'y' axes respectively). Double the 'I' value and you double the stiffness (I'd compare the degree of 'I' per rail weight (or rail cost) to find what would be the most efficient).

Additionally, you might also want to read over this post:

https://www.rocketryforum.com/showt...t-A-Build-Thread-of-sorts&p=725808#post725808

... and you'll see just how much the (unsupported) length effects 'rail whip' -- it goes up with the cube of the length, which is significant. Frankly, anchoring the rail right at the base with no additional stiffening (back struts, etc) is rather minimalist engineering (that's a nice way of saying 'poor engineering') -- you could do better than that (even a simple tie-back directly opposite the 'live slot' (say 2/3 the way up) down to the ground would do wonders for the rail rigidity).

As for length -- get two 6' lengths and some couplers - then you have plenty of length for the slower vehicles that need it (provided you get that supplemental strut support in place).

As for how much 'I' you need -- that's where the hobby needs to mount a little research effort to establish how much force (at the upper tip) a rocket of 'x' pounds exerts -- then you'd have something that would permit a *rational* design.

-- john.
 
My intention is to use square steel tubing to build the base. The rail will bolt on in 3 - 4 places over an 18" section. I'll post photos of the build.
 
I'm getting ready to build a 1515 rail launch pad. I need a large rail for my L3, and our club needs a nice sized rail, so I'm doing it.

It should be 10 ft for a club.

You don't know what will be flying off it in the future.
Not all L-3 capable rockets fly high thrust motors.

If just for yourself, you can get away with minimum for safety.

Does your club have a trailer? Once you get the rail there....should be no problem. Do NOT cut that rail in half, if at all possible.

I have flown off the light weight, it is very stiff. Can't tell difference between it, & solid

Edit: largest rocket I have flown off a 10ft is 6in diameter.....12ft tall.....65lbs.
 
Last edited:
It all depends on how you set it up, but you have to figure on "losing" some of your length to your stand off from the blast plate and mounting. We have a 10 ft. 1515 rail, with a 4 ft ext. if needed. A longer single piece is best, but the length you choose is dependent on your transport capability. With the joining plates, I see no problem at all with several pieces if need be. We have the handle lock pivot plus the blast plate tilts up to the rail which leaves the net rail length (10 ft.) at 8 ft. You can launch some pretty big rockets off a 10ft. rail though.

DSC_0495.jpg
 
Before our club (METRA) had any rails of any size I bought two 6' sections of the 80/20 and the coupler hardware.
I was going to take them apart but, they are still joined to this day.
It's stored in the clubs trailer so no need to take it apart any more.


JD
 
Here's some pics of our club's 1010 rails, but we have 1515 rails built with the same design. These have been incredibly durable and are very stable.

The rail pivots on the bottom pin and is held in place with the upper pin. Pull the upper pin and lay the rail back onto the rear post to load the rocket. The base is T shaped and the blast deflector is part of the structure. The center piece in the base is a 1030, the rest are all 1010 pieces.

Admittedly, these do not get transported much. The rails are stored inside, but the bases are stacked outside the sea container all summer. Every thing gets piled in a pickup and hauled a 1/4 mile across the field to the launch site in the fall, sit in the field all winter and get hauled back in the spring. This pad was built in 2008 so it's been outside for 6 years. The launch rails get a good cleaning each fall before going out to the field. WD40 and a green meanie is all it takes.

IMG_1289.jpg

IMG_1290.jpg

IMG_1292.jpg

IMG_1293.jpg

IMG_1294.jpg
 
Those are nice rails Handeman.

I just received my 8' section of 1515 today. I'm going to mount it to a Jawstand, and use stakes / sandbags to weight the stand down.
 
The 1515 rail that I have is actually two 8' sections - each section is attached to a 10' piece of triangle tower.

The tower sections are secured together and the rail is line up and then fastening plates hold it tightly together. Once mounted tot he base I can (and have) comfortably launched 75 pound rockets from it.

Since it comes apart I can load it in the back of my Dakota pick up and head to the field.

The big tower is one piece of 1515 mounted to rohn tower and the other is uni-strut fastened to 20' of rohn tower.
the little rail is 10' of 1010 rail and a small base - good for rockets up to 20 pounds
 
I bought two 6 foot rails, tapped them and ran a threaded rod into them to make it a 12 foot rail that can be taken apart. It is mounted on a Jawstand with leg extensions to make it more stablenew launch pad 001.jpg new launch pad 006.jpg
 
Back
Top