Graphite Launch Rod ?

I'm getting back into the hobby after a ~20 year absence, so forgive me if this is a dumb question or has been discussed already...

I'm putting together a launch system for Mid-Power (up to G motors) rockets using a 1/4" launch rod. I was wondering if there is any reason not to use a 1/4" graphite tube for the rod (I'm thinking two 3' sections). It seems like it would be stiffer than steel, lightweight, and can be made to break down for transportability. Any thoughts ?

Do you think it would be stiffer? I'm thinking it would be flexible and springy, but maybe I'm thinking of a different kind of rod. If you want something proven to be stiffer than 1/4" steel rod, try a rail.

Swany said:

I'm getting back into the hobby after a ~20 year absence, so forgive me if this is a dumb question or has been discussed already...

I'm putting together a launch system for Mid-Power (up to G motors) rockets using a 1/4" launch rod. I was wondering if there is any reason not to use a 1/4" graphite tube for the rod (I'm thinking two 3' sections). It seems like it would be stiffer than steel, lightweight, and can be made to break down for transportability. Any thoughts ?

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It could be stiffer than steel, but probably would not be as stiff as an aluminum rail, and would be a lot more expensive, and I don't think it would be easy to join (2) 3' lengths without a discontinuity.

The standard 1010 rails is 1" square profile and in 6' lengths is ~$20-$25. You can get it in 3' lengths as well and as long a 145" or even 290" mill run lengths. And rails are easy to join however most folks use 6' or 8' lengths. This is what most folks use. You can also get 10 mm, 15 mm, 20 mm and 25 mm metric rails from other sources. All should be stiffer than a 1/4" carbon rod.



The middle drawing is the standard solid extrusion and the right drawing is the lightweight hollow extrusion.

Bob

I would also recommend a rail, but a graphite tube, like an arrow shaft should probably be stiffer then a steel rod. Most tubes are stiffer then a solid rod. If you have some and want to use them, I think they might work quite well. I would question the cost if you had to go out and buy them. I don't know what they cost, but I suspect more then stainless steel rod would cost.

The other thing to consider is where you will be launching the G size rockets at. If you are going to club meets, you might find it difficult to get a 1/4" rod since many clubs use rails and only have 1/8" and 3/16" rods for LPR. At our club, we have 10 small rail pads, 5 larger rail pads, a trailer launcher, and to sawhorse pads with 5 rods each for LPR. There are only to old pads that can use rods. We only put them out because some of the TARC teams and a few old rockets still show up with 1/4" launch lugs. Most of the members with 1/4" lugs on their rockets add rail button to the other side a few years ago.

TARC requires at a minimum a 1/4" x 6' rod however they now provide 6' 1010 rail as well because a 1/4" steel rod is often not stiff enough for TARC rockets.

Bob

Someone tested a 1/4" graphite rod at last weekend's LUNAR launch. Apparently it worked fine for his rocket.

I generally bring my own pad(1/4") to the club launches, mainly because my rod is longer.
Rex

Rex R said:

I generally bring my own pad(1/4") to the club launches, mainly because my rod is longer.
Rex

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Braggin' again I see?? LOL

Later! OL JR

Thanks for the helpful replies (for the most part !). The reason I am looking at a 1/4" launch rod is that I already have a pad that will accept 1/4" rods and a few rockets with 1/4" lugs. Ultimately I'll probably switch over to rail buttons, but am looking for some instant gratification ! I can get a 6' graphite tube for around $15.00 (although shipping will probably triple the price), but after looking at the specs, it will be about the same stiffness as a steel rod so I'll probably just go that route for now.

Rex R said:

I generally bring my own pad(1/4") to the club launches, mainly because my rod is longer.
Rex

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Sure, it's longer, but is it stiffer?

Those with dirty minds who are looking at this thread like this:




You can go ahead and leave.

woosh has 48" rods in 1/4" dia. my launch rod (ss) is about 65". I prefer the added length for my big daddy, intercepter e, and other 24mm powered birds. is it stiffer than a rail, no. I have however seen slo-mo videos of birds launching from 1010 rails...the notion of there being no rail whip is a myth.
Rex

bobkrech said:

It could be stiffer than steel, but probably would not be as stiff as an aluminum rail, and would be a lot more expensive, and I don't think it would be easy to join (2) 3' lengths without a discontinuity.

The standard 1010 rails is 1" square profile and in 6' lengths is ~$20-$25. You can get it in 3' lengths as well and as long a 145" or even 290" mill run lengths. And rails are easy to join however most folks use 6' or 8' lengths. This is what most folks use. You can also get 10 mm, 15 mm, 20 mm and 25 mm metric rails from other sources. All should be stiffer than a 1/4" carbon rod.

The middle drawing is the standard solid extrusion and the right drawing is the lightweight hollow extrusion.

Bob

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This post reminds me that I have a lot of questions about rails, and this one nearly addresses one of them: how are they joined? I assume it's a rod in the center hole, but I don't know what size rod that requires. And is that how they're often mounted - a rod coming out the bottom and held by something? [Edit] I have seen plans for a launch pad using a drill chuck to hold any size rod, and wonder if that might work to mount a rail. [End edit] I think I read this was so somewhere, but now I can't find the source. I'd like to build a rail (I've seen the PVC one in the Apogee newsletter, but I think I want to figure out if I can make one that will tilt), so I've been reading what I can find. I'm starting to reach a size of rocket where launch lugs look less and less desirable.

Get an 8 foot rail. You never have to deal with that issue.

As for mounting it? A 1/4*20 hex bolt head ground down slightly will slide perfectly into the channel. Check John Coker's site. he shows how to build an epic 8020 pad.

blackbrandt said:

Get an 8 foot rail. You never have to deal with that issue.

As for mounting it? A 1/4*20 hex bolt head ground down slightly will slide perfectly into the channel. Check John Coker's site. he shows how to build an epic 8020 pad.

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Or you buy purpose made nuts which work even better. They are not expensive.

lcorinth said:

This post reminds me that I have a lot of questions about rails, and this one nearly addresses one of them: how are they joined? I assume it's a rod in the center hole, but I don't know what size rod that requires. And is that how they're often mounted - a rod coming out the bottom and held by something? [Edit] I have seen plans for a launch pad using a drill chuck to hold any size rod, and wonder if that might work to mount a rail. [End edit] I think I read this was so somewhere, but now I can't find the source. I'd like to build a rail (I've seen the PVC one in the Apogee newsletter, but I think I want to figure out if I can make one that will tilt), so I've been reading what I can find. I'm starting to reach a size of rocket where launch lugs look less and less desirable.

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We use 8' 1010 rails on our pads at BattlePark. The pads are built from 1010 and 1030 stock with a steel blast plate that is used as a stiffener. Two pins hold the rail vertical, but if you pull the upper pin out, the rail tilts back and down for loading. They are very stable and we launch up to 20 lb rockets from them. The pads go out into the field in the fall and stay there until our season ends in the spring because they are not exactly portable. The pads are about 7 years old now. The steel blast plates are starting to show some rust, but they are probably good for another 5 years or more. Here's a few pics.

Handeman said:

We use 8' 1010 rails on our pads at BattlePark. The pads are built from 1010 and 1030 stock with a steel blast plate that is used as a stiffener. Two pins hold the rail vertical, but if you pull the upper pin out, the rail tilts back and down for loading. They are very stable and we launch up to 20 lb rockets from them. The pads go out into the field in the fall and stay there until our season ends in the spring because they are not exactly portable. The pads are about 7 years old now. The steel blast plates are starting to show some rust, but they are probably good for another 5 years or more. Here's a few pics.

View attachment 252546 View attachment 252541 View attachment 252545 View attachment 252544 View attachment 252542

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Nice. Is that entirely made with 80/20 rails? I assume they sell connectors and brackets.

I've checked out the John Coker launch base. It's nice, but I think it's beyond my skills and needs at the moment - I'm not sure how I'd cut that square steel tubing, or what I'd use do attach it all together (though sometimes you see that these things are easier than they seem when you actually build them). All I have at my disposal for cutting is a hack saw.

I'm only thinking of building a rail for something up to about a G motor. I'm thinking six feet - maybe 8, to allow those lower initial thrust rockets to fly straight. I'm just in the initial thoughts and planning stage at the moment. Thank goodness for TRF - I don't know where I'd be rocketwise if I had to figure everything out on my own!

lcorinth said:

Nice. Is that entirely made with 80/20 rails? I assume they sell connectors and brackets.

I've checked out the John Coker launch base. It's nice, but I think it's beyond my skills and needs at the moment - I'm not sure how I'd cut that square steel tubing, or what I'd use do attach it all together (though sometimes you see that these things are easier than they seem when you actually build them). All I have at my disposal for cutting is a hack saw.

I'm only thinking of building a rail for something up to about a G motor. I'm thinking six feet - maybe 8, to allow those lower initial thrust rockets to fly straight. I'm just in the initial thoughts and planning stage at the moment. Thank goodness for TRF - I don't know where I'd be rocketwise if I had to figure everything out on my own!

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Yes, except for the blast deflector plates and the two pins, everything is made from the 1010 or 1030 rail. The screws, brackets, etc. are all available for and designed to be used with the rails.

6 ft is fine, 8 is better, but 6 is also easier to store and transport.