Launch Tower Project - A Build Thread of sorts

Objective:


Background
As I was building my L3 rocket, I quickly realized that it would be way too big and too heavy to fly off a regular 1010 rail. Fortunately, my good friend and L3 TAP David Holloway was kind enough to loan me his tower for me to use at the launches he wouldn't be able to attend. A few weeks before our first scheduled launch of the year, I picked up the tower from him down in Salem. As he showed me how it all goes together, I noticed that I could easily build something like it myself without too much difficulty. When it came time to set up at the launch site, I quickly discovered its strength and ease of use. So as if I didn't before, now I REALLY wanted to build my own tower!

David sent me the entire list of suppliers he used to help me get going on mine. His design by the way, is a complete duplicate of Fred Azinger's. It involves a rail supported by a tower that is attached to a hand truck/dolly for ease of transport and rocket loading. (More on this later.) So I'll be using a design inspired by David, that he learned from Fred...funny how these things happen, eh?

Materials
My tower will consist of the following:

• 2 x 5' sections of aluminum trusses, normally used for lights and lighting equipment at rock concerts.
• 2 x 6' sections of black anodized 1010 rail.
• Generic hand truck from Home Depot or Lowe's.
• Hose clamps to attach tower to hand truck.
• Piece of sheet metal for use as a blast plate.
• Generic cargo straps to secure tower in place.
• Generic corkscrew-style ground stakes to attach straps to.

Easy, right? A few answers to questions you may have already:

• Using 2 sections of truss (instead of one 10' section) because, as David pointed out, this will give me a set of pre-drilled holes in the center section to bolt the rail to. Why destroy drill bits if I don't have to...
• Using 2 sections of 6' rail instead of one 12' rail to save on shipping. The folks at TECO explained to me that UPS won't ship a box that long, and it would have to come via ground freight. This would require shipping charges of $150 or more...yikes. (Although that's what David wanted to do!) This will mean simply having to bolt the 2 sections of rail together. We'll worry more about that when the time comes.
• The trusses are 12" wide meaning I'll need to find a hand truck that is also close to 12" wide. No big deal.

Construction
Also pretty easy. The 2 trusses are attached together using the supplied pins and clips. The rail is attached to the tower using common nuts/bolts/washers through the pre-drilled holes along the length of the trusses. The whole tower then attaches to the hand truck using ordinary hose clamps. That way, I can remove them for ease of storage and hauling of the tower. The straps simply hook on to the center section of the trusses and anchor into the ground. (See photo at top of post.)

When loading a rocket, the hand truck wheels serve as a pivot point. This also makes the tower even easier to transport!

Been ordering materials these past few days. Trusses should be here early next week and 1010 rail sections should arrive in about another week. Might even do a bit of "hand truck shopping" this weekend.

That is nifty. Great idea. I would have never thought to mount it to a dolly.

cwbullet said:

That is nifty. Great idea. I would have never thought to mount it to a dolly.

Click to expand...

Thanks...but I wish I could take credit for the design! :wink:

I like it!
Simple, cheap and an elegant solution.
Looks like you will need to stake the dolly/base also. (I didn't see any in the photo.)

Airobert said:

I like it!
Simple, cheap and an elegant solution.
Looks like you will need to stake the dolly/base also. (I didn't see any in the photo.)

Click to expand...

Thank you! Again, can't call the design my own but that's exactly why I liked it too.

Regarding the dolly - actually, it's attached to the tower using 2 sets of hose clamps (3 on each side). If you look closely, you can see them in the photo.

The only question I have is about the two forward straps. Do you have any issues with fin clearance with those? Do you have to attach them to the rear of the truss to clear the fins?

Handeman said:

The only question I have is about the two forward straps. Do you have any issues with fin clearance with those? Do you have to attach them to the rear of the truss to clear the fins?

Click to expand...

You're right, you do need to be careful with the 2 forward straps and fin clearance. They are attached to the side of the truss in a way that they won't interfere. If you flew a rocket off this type of design with really big fins (I haven't yet) then it could be a problem.

UPS Quantum View tells me that trusses should be here on Tuesday.

UPS delivered 2 triangle-shaped boxes today! Wonder what those could be...


Ready for action.

Quick question - where did you buy the trusses, and what do they cost ?

AndyC said:

Quick question - where did you buy the trusses, and what do they cost ?

Click to expand...

www.cheaplights.com
These are 4.92' x 12" triangle trusses, $168 each I think.

Anyone having troubles posting photos... I'm trying to upload pictures of the rail and hand truck but I can't seem to embed them in my post.

AlnessW said:

Anyone having troubles posting photos... I'm trying to upload pictures of the rail and hand truck but I can't seem to embed them in my post.

Click to expand...

Yes. I'm having the same issue and have seen it on most recent posts with photos.

lets's see if pic will load


WOW this is really screwy....2 load weird and other looks like a pasted urrl when it's just an attachment? Ya got me wondering .

All 3 are attachments... 2 are hidden and 3rd loads full size without clicking on it. Anyone figure this out?

OK, glad I'm not the only one! Normally when I use BB code to imbed an image, it looks like this (without spaces in between brackets):


Now the forum wants to do this when posting an image, which simply appears as a hyperlink when posted:

Photos seem to be working again. So, back to business...

Purchased 2 x 6' of black anodized 1010 rail from TECO Pneumatic who then ordered it from 80/20, Inc.


Rails.


Got a hand truck from Home Depot that has the correct width to be attached to the tower via hose clamps.

This has got me thinking. I love building rockets, but another idea has been drifting around in my head. I want to build a launch rail, etc, that has pipes instead of a blast deflector, so that the flames can be redirected first sideways, then up parallel to the rail/rocket. Think if what skids would looks like!! Also, I think that this system would make skids safer to fly in the sage.
What ya think Wilson?
The more launch systems that the club has access to, the better yes?

Salvage-1 said:

This has got me thinking. I love building rockets, but another idea has been drifting around in my head. I want to build a launch rail, etc, that has pipes instead of a blast deflector, so that the flames can be redirected first sideways, then up parallel to the rail/rocket. Think if what skids would looks like!! Also, I think that this system would make skids safer to fly in the sage.
What ya think Wilson?
The more launch systems that the club has access to, the better yes?

Click to expand...

That is a great idea if it works,

Salvage-1 said:

This has got me thinking. I love building rockets, but another idea has been drifting around in my head. I want to build a launch rail, etc, that has pipes instead of a blast deflector, so that the flames can be redirected first sideways, then up parallel to the rail/rocket. Think if what skids would looks like!! Also, I think that this system would make skids safer to fly in the sage.
What ya think Wilson?

Click to expand...

Cool idea! Do you mean like a system of pipes to direct exhaust sideways? Sounds like something NASA might do!

Salvage-1 said:

The more launch systems that the club has access to, the better yes?

Click to expand...

Most definitely, but this tower sure ain't for club use...

Handeman said:

The only question I have is about the two forward straps. Do you have any issues with fin clearance with those? Do you have to attach them to the rear of the truss to clear the fins?

Click to expand...

AlnessW said:

You're right, you do need to be careful with the 2 forward straps and fin clearance. They are attached to the side of the truss in a way that they won't interfere. If you flew a rocket off this type of design with really big fins (I haven't yet) then it could be a problem.

Click to expand...

One solution (see attached) is to make your strut supports rigid. In the case of my tower, I welded (brazed?) both a right-handed and left-handed nut (3/8") to a 10' piece of 1/2" EMT conduit and then 'robbed' the ends from some 3/8" turnbuckles (to allow, at least, a little adjustability). This way, you can anchor these struts opposite from the rocket and it would be near impossible for any interference (this would pretty much require anchoring the base (your hand truck) in this case.) Also, your anchor points at ground level would need to be 'de-mountable' (carabiners, etc) such that the tower can be lowered for loading and final launch prep. (The carabiners would need tweaking such that there is no slack once anchored). The struts break down and carry very well inside the tower.

A few additional observations:

1) I would locate your rail such that the bottom edge is no lower than where you want the bottom of the rocket to be -- there's no need to pay for rail (i.e. below the rocket) that you'll never use. (You can see an example in the picture).

2) You might consider taking off from the top of the two rear tower tubes and providing a little diagonal strut to the top of the rail - as a little additional strength and rigidity (again, look at the picture). In my case, this was some 1/2" dia / 0.030" wall (+-) stainless steel tubing (McMaster-Carr) that I crushed the ends flat for drilling a hole for mounting. In my case (10' rail assembly) it may not be as important as in your case (12' rail) - especially with Level 3 vehicles. This creates a triangle structure - which is your strongest structural shape - very rigid.

3) While many feel that a single angled blast deflector is OK, I generally feel that an 'inverted V' is better, as that neutralizes any lateral force from the motor exhaust. Anchored solidly, the launcher can handle it - but it's clear that "NO lateral force is better any *any* lateral force" -- look at how NASA does it.

4) I added two 'binding posts' (see Radio Shack, etc) at the bottom to tie in igniters and, from that, extended with a simple extension cord (to normal 2 pole wall plugs at the controller) -- see close-up picture.

-- john.

Salvage-1 said:

This has got me thinking. I love building rockets, but another idea has been drifting around in my head. I want to build a launch rail, etc, that has pipes instead of a blast deflector, so that the flames can be redirected first sideways, then up parallel to the rail/rocket. Think if what skids would looks like!! Also, I think that this system would make skids safer to fly in the sage.
What ya think Wilson?
The more launch systems that the club has access to, the better yes?

Click to expand...

I had one of my rails set up with a 90* bend 3" exhaust pipe. Best part is it would blow a smoke ring

jcato said:

A few additional observations:

1) I would locate your rail such that the bottom edge is no lower than where you want the bottom of the rocket to be -- there's no need to pay for rail (i.e. below the rocket) that you'll never use. (You can see an example in the picture).

2) You might consider taking off from the top of the two rear tower tubes and providing a little diagonal strut to the top of the rail - as a little additional strength and rigidity (again, look at the picture). In my case, this was some 1/2" dia / 0.030" wall (+-) stainless steel tubing (McMaster-Carr) that I crushed the ends flat for drilling a hole for mounting. In my case (10' rail assembly) it may not be as important as in your case (12' rail) - especially with Level 3 vehicles. This creates a triangle structure - which is your strongest structural shape - very rigid.

3) While many feel that a single angled blast deflector is OK, I generally feel that an 'inverted V' is better, as that neutralizes any lateral force from the motor exhaust. Anchored solidly, the launcher can handle it - but it's clear that "NO lateral force is better any *any* lateral force" -- look at how NASA does it.

4) I added two 'binding posts' (see Radio Shack, etc) at the bottom to tie in igniters and, from that, extended with a simple extension cord (to normal 2 pole wall plugs at the controller) -- see close-up picture.

-- john.

Click to expand...

That's a neat design! In response to your ideas:

1. Actually I hadn't even thought of that. I could place the rail stop at the very end of the rail which could get me an extra 12" or so of what-normally-would-be-unused rail.
2. Couldn't hurt, but like you mention I'm using a longer rail.
3. Is that gray spider-looking thing your blast deflector?
4. That's nifty. My launch system (as well as our club's system) just uses regular clip leads.

AlnessW said:

That's a neat design! In response to your ideas:

1 - Actually I hadn't even thought of that. I could place the rail stop at the very end of the rail which could get me an extra 12" or so of what-normally-would-be-unused rail.

Click to expand...

If you'll look at the close up picture, you can see the 'stop' I put in place - just a 3" piece of 1/8"x1" stainless bar stock bolted right across the bottom of the rail - which the CNC lugs on the vehicle simply rest on (my rail assembly is a solid 3/4" square spine with 2 - 1"x1"x1/8" angles bolted one each side - legs outstanding - making the total rail width 2 3/4"). With that, however, there isn't even a (literal) inch of the rail wasted (as far as guidance).

2 - Couldn't hurt, but like you mention I'm using a longer rail.

Click to expand...

That's my point, Wilson -- from my seat, you need it more than I do: you've got a 12' rail attached to a 10' tower. If you shift up the rail to, say, 24" off the ground, now you have 4 feet of rail unsupported right at the point where the vehicle is fixing to become a 'free body in space'. If there were to be any flexing, this would be the worst time to have it. A Level 3 bird on that (not entirely rigid) rail would make the decision a rather easy one - especially considering it's rather easy to fabricate and install. I'd say come off the two back tower verticals up to about a foot down from the tip of the rail, there's no need to go all the way to the very top.

3 - Is that gray spider-looking thing your blast deflector?

Click to expand...

No, it's just a little stainless tripod thing I found at the junkyard -- and I figured it'd make a decent stand for some low power stuff. It just got placed in the picture on a lark (These photos were to submit to the airport commission when we were planning a Boy Scouts 'Aviation Camporee' here several years ago).

I have a launcher based on a drafting stool base that has a 12" square 'table' with a 6" square opening in the middle that uses the 'inverted V' deflector - and my plans are to adapt that to this launcher (it is removable from the drafting stool base, so fitting to this tower would be rather trivial). The tower has only seen two or three launches - and I've simply placed a flat piece of stainless directly on the ground under the vehicle as an interim solution.

4 - That's nifty. My launch system (as well as our club's system) just uses regular clip leads.

Click to expand...

Yeah, it works rather well -- the binding posts makes ignition wiring rather robust -- just strip off maybe an inch or two of insulation during prep -- then, just open the binding post, wrap the bare leads and twist down tight -- which also helps from throwing the igniter off who knows where (to start a grass fire when it lands). Every time, the igniter is 'tied' to the tower and is hanging right there post-liftoff.

One additional benefit is that these binding posts make 'shorting' the igniter during final prep a breeze -- I've fabricated a short piece of wire with banana plugs on each end (and a 'Remove Before Flight' flag on it). These plugs fit in the central jack on the binding post and don't even interfere with igniter wireup - since the igniter leads go *around* the post. So, almost from the very instant a shorted igniter is 'un-shorted' (to connect in to the ignition circuit), it is shorted again - literally just a few seconds of unshorted leads. When everything is prepped and ready to go, just pull the shorting jumper out and walk away. (An even better approach would be to keep a 12" alligator jumper on the leads above the tag ends that go to the binding post and only remove that once the leads are cinched down on the binding posts and the shorting jumper is installed - but then might as well leave the alligator jumper in place the whole time. The 'banana jumper' is clearly optional in this scenario.)

-- john.

jcato said:

If you'll look at the close up picture, you can see the 'stop' I put in place - just a 3" piece of 1/8"x1" stainless bar stock bolted right across the bottom of the rail - which the CNC lugs on the vehicle simply rest on (my rail assembly is a solid 3/4" square spine with 2 - 1"x1"x1/8" angles bolted one each side - legs outstanding - making the total rail width 2 3/4"). With that, however, there isn't even a (literal) inch of the rail wasted (as far as guidance).

Click to expand...

Gotcha - thanks for the advice!

That's my point, Wilson -- from my seat, you need it more than I do: you've got a 12' rail attached to a 10' tower. If you shift up the rail to, say, 24" off the ground, now you have 4 feet of rail unsupported right at the point where the vehicle is fixing to become a 'free body in space'. If there were to be any flexing, this would be the worst time to have it. A Level 3 bird on that (not entirely rigid) rail would make the decision a rather easy one - especially considering it's rather easy to fabricate and install. I'd say come off the two back tower verticals up to about a foot down from the tip of the rail, there's no need to go all the way to the very top.

Click to expand...

Oh, I see what you mean now. Indeed, in the event I do end up having a long length of unsupported rail at the top of the tower then reinforcing that section sounds smart. You never know...

No, it's just a little stainless tripod thing I found at the junkyard -- and I figured it'd make a decent stand for some low power stuff. It just got placed in the picture on a lark (These photos were to submit to the airport commission when we were planning a Boy Scouts 'Aviation Camporee' here several years ago).

Click to expand...

I think that would make for a fine low power pad! Practically with a built-in blast deflector no less.

Yeah, it works rather well -- the binding posts makes ignition wiring rather robust -- just strip off maybe an inch or two of insulation during prep -- then, just open the binding post, wrap the bare leads and twist down tight -- which also helps from throwing the igniter off who knows where (to start a grass fire when it lands). Every time, the igniter is 'tied' to the tower and is hanging right there post-liftoff.

Click to expand...

Cool! Fortunately few of our local launch sites pose a dry grass nearby the pad hazard, but certainly a good precaution keeping igniters from going flying.

me said:

That's my point, Wilson -- from my seat, you need it more than I do: you've got a 12' rail attached to a 10' tower. If you shift up the rail to, say, 24" off the ground, now you have 4 feet of rail unsupported right at the point where the vehicle is fixing to become a 'free body in space'. If there were to be any flexing, this would be the worst time to have it.

Click to expand...

AlnessW said:

Oh, I see what you mean now. Indeed, in the event I do end up having a long length of unsupported rail at the top of the tower then reinforcing that section sounds smart. You never know...

Click to expand...

Wilson, take a look at this video - particularly the close-up pad camera at about 1:30 (pay particular attention to the rail after the rocket leaves it)...

https://www.youtube.com/watch?v=0bOtwuWYSlI

(This looks like about a 4" rocket on a 38 or 54mm motor - a mid-range Level 2 bird)

That, I think, 'tells the tale'.

-- john.

jcato said:

Wilson, take a look at this video - particularly the close-up pad camera at about 1:30 (pay particular attention to the rail after the rocket leaves it)...

https://www.youtube.com/watch?v=0bOtwuWYSlI

(This looks like about a 4" rocket on a 38 or 54mm motor - a mid-range Level 2 bird)

That, I think, 'tells the tale'.

-- john.

Click to expand...

Thanks for the video. Wow, talk about rod whip!

jcato said:

Wilson, take a look at this video - particularly the close-up pad camera at about 1:30 (pay particular attention to the rail after the rocket leaves it)...

https://www.youtube.com/watch?v=0bOtwuWYSlI

(This looks like about a 4" rocket on a 38 or 54mm motor - a mid-range Level 2 bird)

That, I think, 'tells the tale'.

-- john.

Click to expand...

That's not the rail bending. That's the attachment point at the bottom bending.

Most pads I've seen are rather poorly attached to the rail; better ones hook onto the rail in multiple places along its length.

CarVac said:

That's not the rail bending. That's the attachment point at the bottom bending.

Most pads I've seen are rather poorly attached to the rail; better ones hook onto the rail in multiple places along its length.

Click to expand...

Your observation has merit, CarVac - as I've seen some rather questionable engineering on the range over the years. But, consider this:

A launch rod / rail is, basically, a cantilever beam - just oriented vertically instead of horizontally, like most beams would be. The structural formula for deflection of a cantilever beam (with a perpendicular force right at the unsupported end) is:

F L^3
-----
3 E I

where:
F = force acting at the tip (choose your unit - lbs, kg, etc)
L = length of beam (again, choose your unit - in, ft, meters)
E = Modulus of Elasticity, (consistent unit to above -- generally psi)
(for aluminum (6105-T5), this is 10,200,000 psi)
I = (Area) Moment of Inertia (generally, in^4)

(see the first example at:
https://en.wikipedia.org/wiki/Deflection_(engineering) )

(for completeness...)
'E' can be thought of as 'resistance to deflection' - for comparison;
Steel = 29,000,000 (i.e. 3 x as stiff as aluminum)
Titanium=16,500,000,
... and is, basically, the stress that would stretch a 1 sq.in. rod to
twice it's original length (it would fail in tension long before that)

It isn't massively important that we 'run some numbers' on this deflection equation -- just LOOK at it to garner some understanding of what's happening. A few points:

1. Since 'E' and 'I' are both in the denominator,
   the larger they are, the smaller the deflection will be.
   This is linear, too -- double 'E' or 'I' and the deflection
   will be halved.
   One generally can't change 'E' - it's an inherent property of the material.
   
   'I' is geometric, so that can be controlled by the arrangement of
   how and where one puts the material (in the cross-section)
   e.g. the 1515 rail (Ix=0.2524 in^4) is almost 6 times as stiff as
   the 1010 rail (Ix=0.0442 in^4) - 5.71x, actually.
   (Since it only weighs 2.63 times as much (1.3433/0.5097lb/ft) it's twice
   as efficient, too - pound for pound).
   (see 80/20 tech lit)
   
   
2. Notice that the length 'L' is cubed (raised to the third power).
   That is significant - double the length, and the deflection
   goes up by a factor of 8.
   i.e. the deflection at 2 feet is 8 times what it is at 1 foot
   and the deflection at 4 feet is 8 times that for 2 feet
   (or 64 times what it is at 1 foot)

I've went back and studied that launch footage several times - including the slo-mo at the end - and it is clear that the rail is progressively flexing consistent with the math above. To be sure, while some rather inadequate anchorage at the bottom can contribute to the flex, one must understand that, even *without* flexing at the anchorage, the above equation shows a cantilever beam will experience significant flex at the tip - with perfectly rigid anchorage (this rail looks about 12 feet long - which (L^3) means the tip would flex over 1700 times (12^3) as much as the point 1 foot up from the base would). Any flexing of the anchorage only ADDS to this.

If Wilson's rail projects 4 feet above his tower (as we've been talking), that (unsupported) tip would flex 64 times as much as one that would project only 1 foot above the tower - given the same loading. Anchored for 8 feet along the tower (excellent) would come pretty close to a perfectly rigid anchorage - but it won't change what happens to the portion of the rail above that anchorage.

But, I agree with you that, flying some of these vehicles off of rails anchored inadequately as they are (far too often) is rather foolish. Spend all that money on those fancy rails and then negate their benefits by 'slopping around' with how it's anchored. Not very smart.

-- john.

Put the tower together today after waiting on rail joiners to arrive from McMaster-Carr:


"Double slide-in t-nuts" from McMaster used to join the 2 sections of 1010 rail together. $7 shipping for $8 worth of parts...great. :eyeroll:


Simply a metal place with 2 tapped holes in it, and a pair of (hex key) machine screws.


A plate goes inside 3 of the rail channels (the 3 I'm not using) with a few washers on the outside to form a "sandwich."


Now that the rail is ready, on to bolting the trusses together. Each truss comes with a set of hardware to attach them together - a system of torpedo-esque connectors, pegs, and cotterpins. Note that only 2 of the 3 sides of the truss get the pegs and cotterpins.


And then the second truss gets stacked on top. Again, notice that one of the sides does not have pegs/pins. We'll get to that one later.


1/4"-20 machine screws used for bolting the rail to the tower. The Phillips heads have been "modified" slightly on the bench grinder so that they will slide nicely down the rail.


Now you see it coming together. The machine screw is slid down the (back) channel of the rail, then through the factory-drilled hole in the truss. Washers provide adequate space between the truss and the rail, and another nut/washer tightened on the back side of the screw holds everything in place.


Back to the center section. We now use these holes as the center attachment point for the rail.


And now the forward end of the rail.


The whole tower assembly is then attached to the hand truck using common hose clamps. (These are removed for transport and hauling.)

(More below.)

I am sooo gonna clone your clone.

The stand-off consists of an ordinary bolt (also modified to fit the rail on the bench grinder), washer, and nut.


And now for the finished product! Can't wait to use this and "get it dirty."