High power launch tower design review

I haven't designed a launch tower before, however seeing as i'm designing a rocket for supersonic I figured I'd go all out and get rid of the launch tower - as I'm sure it's been slowing me down in the past.

If anyone would care to take a look at my tower design and give feedback I'd be much obliged!

Design:
* Plates made from 12mm plywood, standard liteply from the hardware store.
* The angle in the middle for guiding the rocket is 25x19mm which is supposed to be 2mm thick but actually 1.65mm. Comes in 2M lengths. Planning to attach with countersunk screws on the flat sides. There is a 0.75mm radius on the corner which the rocket would sit against.
* The cylindrical tubes are 38mm PVC pipe, OD is 42.93mm. These come in 1.2M lengths here, which, if I wanted to use the full 2Metre length of angle extrusion would require a coupler. I'm hoping these will help square up the system and keep it rigid. These will be friction fitted.
* Holes on plates are for cheap 8mm rope at the top (WLL 84kg) to act as guy-wires, and the ones on the bottom plate for a couple of tent pegs, just to make sure it stays straight in boost with a smaller motor.

The tower is pictured as a 2M long tower, with my rocket which is 54mm, ~1334mm long in it. The smallest motor I would fly in the rocket simulates to "Minimum velocity for stable flight reached at: 923.74 mm". Given this, can I make my tower the same height as the PVC - 1200mm safely?

I've left a 1-2mm safety margin on the rocket fit to allow for tolerances in the extrusion, milling and body tube - how tight a fit should the rocket have with the tower? I'm guessing that bouncing around is bad, as is friction of any sort?

Any other ideas or suggestions?

Very neat design. Most I have seen are adjustable. Is this one?

no, its designed for a specific rocket, I wanted it to be as rigid as possible - It's not hard to make another set of plates on the mill

Still very nice. I like the unique design.

Here is how it looks at 1.5m, using 1.2m long PVC pipe.



With the highest power motor, this becomes stable in under 100mm, so it should be fine.

I threw 2 pieces in the mill to see how they would come out - looks like it will do the job. I need to get some more 12mm plywood to make the other 2, however i'll wait for the body tube i'm waiting for to arrive first so i can check the fits.

I used a dedicated tower for my altitude attempts back in the early 90's, here in 1992.View attachment 97192
The tower was steel tubes slipped over plugs bolted to the plywood base and top. I allow about 1/16" clearance between the rocket and guide tubes. BTW, from left are Pius Morazumi, AeroPac Prefect, Earl Cagle, Point 39 Productions, me installing igniter, and John Cato.

So I went to get the last parts for this, but the last piece of 1200x600x12 plywood was delaminating at one end I bought the aluminium angle and pipe at a different hardware store chain, so of course this one doesn't have the same stuff (40mm pipe instead of 38mm pipe.) So all i managed to get was the screws.

Hoping I can get to the other hardware store on Saturday so I can mill the last parts and put this together for a test.

I am still working on this. Should have it fully drilled out and assembled this weekend. I machined the final two plates last weekend, and also got the aluminium angle. Now the rocket is finished, I can test fit everything to make sure it will not bind. The cheap paint can i used for the rocket doesnt give a very hard finish - it's going to get scratched to hell with the launch, but thats fine by me



The rocket's build thread is over in scratch built, I think it should have been in high power oh well: https://www.rocketryforum.com/showthread.php?42327-A-little-54mm-airframe-rocket-for-fun

Launch tower is complete, and much more solid than I had hoped for. I think it looks really good with the rocket in it - there is a little bit of room for the rocket to move around but i'm hoping it wont cause any issues. It has maybe 1.5mm clearance on all sides, however with it's length it should still fire straight as it cant tilt on any sort of angle.

Here it is all set up in the back yard.

Greetings,
This is my first post since I joined. Anyways I wanted to say congrats on the tower it looks very nice! I am currently building an all steel high powered launch tower. Accutally just started today. I must say I envy your workshop! Also what software did you use to design that tower? SolidWorks???

Thanks!

Yes, it's done in SolidWorks. It's simple enough you could do it in pretty much anything though, even Illustrator would do.

For all my workshop, I still can't work with steel! I don't have a drop saw, and I don't have a welder (I have an oxy set, but no bottles!). A steel tower would be much nicer and give you a lot more options. Please post a thread with your ideas - I'd love to see them. There are not enough tower design threads out there!

Ok nice, I am just starting to learn how to use SolidWorks... I have 0 knowledge of the ware :/ I don't have a drop saw either, I just found a steelyard that had one and they charged $3.00 (U.S.) per cut. As far as the welding you can just look on CL or Google for some cheap welding services... thats what I did. I wish I had the money to buy a welding machine & drop saw! I also went to the steel yard and found most of the parts there... it wasn't to expensive at all! The trick is finding a place that will sell it in pieces (meaning they don't make you buy all of i)

As far as my tower goes as soon as I get it designed on SW I will post a thread for it. I am about 2+ days into building it. Just waiting to go and get some of the main pieces welded.
The specs are roughly 2ft x 2ft & 5ft tall all steel and adjustable for almost any rocket. My plan is too launch an all aluminum rocket soon

That ended up really nice. Great job.

Thanks, Unfortunately it was too windy to launch, as I have no tracking in that rocket. I have some design changes I'd like to make before next year when I'll be able to launch it again. I'm thinking rather than using ropes to use ratchet straps, as this would be a lot less fiddly than getting the ropes all tensioned evenly.

All in all, I'm pleased with the experiment even if I didn't get to launch. It has given me some ideas for building launch towers in the future.

I've revised the design of the tower, as the fins were capable of "interfacing" with the tower plates on launch if the rocket twisted too much. The new one this can't happen and i decided to go for nice smooth curves just to be different.





I'm in the middle of upgrading my CNC mill at the moment so I can't cut them just yet anyway. First launch of the year is in 5 weeks so there isnt too much rush. I'm planning to make the top and bottom plates out of some nice 17mm structure ply coversheets I got for free, with the others still being 12mm ply. The rope guywire system is still going to be used, however I might change it out for ratchet straps to allow it to be tensioned easier and more evenly.

I also made the holes for the PVC smaller, as the closer hardware store has 41.1mm diameter pipe which doesnt fit the holes as well as the slightly wider tube which it was designed for. I'm thinking of milling a couple of 17mm centring rings with screw holes in them to use above and below the plates to prevent any movement without the need for a super tight friction fit which makes assembly harder.

I had several requests for the designs last time, so attached is a PDF with two plates on a 1200x600 sheet. Feel free to replicate and modify as much as you wish for personal use.

I've built a number of low power competition towers. I'm curious how you intend to attach the interior aluminum angle iron pieces to your plywood frames.

Steve

I did it with self tapping, countersunk screws.

Version 3 of the tower was tested over the weekend. This used T extrusion aluminium, 2m long - with the flat of the T facing the rocket. We figured this would be less likely to bind. The tower worked a treat, with 3 launches out of the 38mm one, and the 54mm (as far as i'm aware... i wasnt around the launchsite much) not getting used.

On the 38mm, only the lower half has support plates, the upper half is free standing. The 54mm tower used the 4 plates spread out and two sections of 1M PVC in couplers.



Set of plates (2x38, 2x54) being milled.


Single break Blackhawk 38 being launched on a 38mm J


Always fun to see the chunks of dirt flying out.


My fiancée with her blackhawk38 in the tower.


Her Blackhawk 38 going on an I600 (she's only L1), 1/8th of a second after ignition.



The aftermath of a launch on the tower

Did the rockets sit all the way down on the ground?

The Mudd club's launch tower, since we use 80/20 1010 rail, has provisions for a rail stop, but the I1299 in Disappearing Act blew it out the bottom and it landed 15 feet away.

When in the 3" diameter configuration, an L2300 didn't bother the rail stop, though. hmm....

We used a small rock on each rocket just to lift it high enough the cap could easily be blown free. We were planning on putting a M5 hex headed bolt through with a nut on either side of the T to make it stick out more, but we didnt feel it was needed for the 38mm launches, and we did not get to the 54's due to time constraints.

In august the 54mm one will have 6 and 6gxl CTI's thrown at it, so we'll see how it holds up.

The rails require a wipe down with industrial "wet wipes" to clear the residue from it, but other than that it's very easy to setup and go.

This is a great design! Are you interested in selling a few of the cut plywood pieces?

I am specifically looking to make a tower for a 29mm rocket. How hard is it to modify your design?

Well, I could make some cut plywood pieces.. but it depends on how much you want to spend on postage - i'm in Australia. Much easier to take a PDF or DXF to a local laser cutter or even a hackerspace and get someone to mill or laser it for you.

The design for these was drawn as fast as possible to get it onto the mill. I drew the 54 and 38mm plates individually to be honest, it was less work. If you PM me with the maximum diameter rocket that is going into it (tip-tip glass makes things not fit!) I can draw up a new plate for you for that rocket

What was your final cost on the tower?

No idea sorry, however those aluminium extrusions are about $12 each here, probably more like $3-5 from a lowes or home depot in the USA. PVC pipe cost me $2 or 3 per length, the 38mm tower uses 3, the 54mm uses 6 and 3 joiners. Plywood didnt cost me anything (12mm/0.5") as they were coversheets (the top/bottom piece of wood on a pallet) from the local hardware store. Then all I needed was a bunch of cable ties and a rock

The CNC mill is mine, so no cost there.

Issus said:

The CNC mill is mine, so no cost there.

Click to expand...

No cost? Where can I get a free CNC machine?!

majordude said:

No cost? Where can I get a free CNC machine?!

Click to expand...

That is definitely not free.

patelldp said:

This is a great design! Are you interested in selling a few of the cut plywood pieces?

I am specifically looking to make a tower for a 29mm rocket. How hard is it to modify your design?

Click to expand...

I could be a go-between... as a cutter of things, and even in the same state as you! If Issus was comfortable with me cutting his drawing (this once, not putting it into production) we could do something. DXF shouldn't be a problem, I'd also be able to redraw from a sketch or dimensioned drawing in a PDF, whatever.

CNC machines definitely not free.

Nat Kinsey
UpscaleCNC

majordude said:

No cost? Where can I get a free CNC machine?!

Click to expand...

Machine isn't free, machining time is Very handy to have though, I use mine pretty much every saturday and sunday for something. Yesterday I made 4 washers out because I was too lazy to go to the store. CNC mills are certainly the ultimate tool for the lazy person - sit at computer, draw it all in CAD, do CAM, save over the network, remote desktop to CNC mills computer in the garage, set it up, start the job... by the time i get out there the parts are usually done.

Wingarcher said:

I could be a go-between... as a cutter of things, and even in the same state as you! If Issus was comfortable with me cutting his drawing (this once, not putting it into production) we could do something. DXF shouldn't be a problem, I'd also be able to redraw from a sketch or dimensioned drawing in a PDF, whatever.

CNC machines definitely not free.

Nat Kinsey
UpscaleCNC

Click to expand...

I have no problem with that. DXF, DWG, PDF, Solidworks 2012 drawing or model, Cut 2D.. pick your poison

If patelldb can tell me the OD of his rocket airframe, OD of any PVC sections he can get (I use 1M long, 38.9mm OD IIRC), and what sizes of T extrusions he can get I'd happily modify the design for him (or anyone else.) I'm very happy with how this tower works for something so easy to pack/transport the 3rd gen tower is very effective.

If anyone wanted to make these commercially, I wouldn't have a problem with receiving a small royalty haha.

To be honest, I really should redraw this using smart dimensions so you just change the size of the centre hole and everything will scale outwards from there, and leave the PVC holes independent... if patell wants one of these (or anyone else) I guess i'll do the mods then

DXF or Cut 2D.... I use VCarvePro, I think that can open a cut2d file? Not sure, the DXF will work for sure.

Nat