Ruggedized small club launch system

[SCE to AUX]

Thought I'd post some pics of a launch setup that I designed/built over the winter lull. Designed to be quick to set up, as close to "abuseproof" as possible (gets used by lots of kids at club launches and classes), and provide a "Real NASA Hardware" feel for the kids when they launch their rockets.

Runs on a pair of self-contained gel cells, with provision for external car battery clips if desired. Handles a rack of 5 "estes type" pads, and a separate camera tripod "HPR" type pad. HPR pad will be getting a relay box setup in the future.

Will fire up to 5 estes igniters at a time. Single motor 5-way drag races are no problem.

Whole thing is waterproof when closed up, and "almost" waterproof when operating (DVM and timer modules are not, most other controls industrial oiltight stuff). External connectors provided with "crud caps" to keep water/mud out when not in use.

Will get some pics of the 5-rod launchrack soon....

 

[SCE to AUX]

More Pics...

 

[Quixote]

Very interesting looking GSE, perfect for a small club or school based group. Would you have a wiring schematic, parts list, and estimated cost to construct? Where did you find the case and those external connectors? That system was beautifully executed, looking forward to your photos of the associated launch Pad!

 

[SCE to AUX]

Very interesting looking GSE, perfect for a small club or school based group. Would you have a wiring schematic, parts list, and estimated cost to construct? Where did you find the case and those external connectors? That system was beautifully executed, looking forward to your photos of the associated launch Pad!

Am working on drawing up a good schematic in digital form from all the "chicken scratches" I made while building it.

The case is a "Pelican" type waterproof equipment case of the type used by outdoor photographers, surveyors, etc. This particular one is a model 1500. I installed an accessory "panel frame" kit to accept the front panel, which I made from .125 thick aluminum sheet. Cost for the case and the panel frame was around $85 on eBay. The pair of batteries were purchased at Home Depot, sold as replacements for emergency lighting. About $25 for the pair, IIRC.

The connectors are milspec bayonet types I salvaged from a bunch of scrapped avionics gear a friend gave me. The mating "crud caps" were found at a surplus dealer.

Most of the rest of the parts came from my "junkbox", accumulated from years of building instrumentation and process control type stuff. Pieces of old projects, stuff scavenged from junked gear, etc. All the oiltight switches came from an old printing press control panel, and the 4 indicator lights came from a scrapped induction heater.

I haven't priced out what this thing would cost to build if I actually bought all the parts at full retail prices, but a figure over $1000 wouldn't surprise me. If you have never purchased industrial control equipment, or milspec electrical connectors, you would be shocked at some of the prices. A single pushbutton switch might cost $30, and that's without the actual electrical contacts, which you purchase separately in whatever configuration you want.

 

[Quixote]

Thanks for the details, I just might have to start searching for components to make something similar, our club GSE is long in the tooth, like built in 1974! Yours is a much more modern and sturdier looking unit. I will likely have some difficulty finding some of the equipment locally, wish we had something like Boeing Surplus in Kent Washington, but we have a few surplus shops here in Calgary that might be worth scouring. Plus I can check out our industrial electronics stores as well. I appreciate your feed back! Your comment on "Military Spec" is well taken.

 

[Conan4480]

Very nice setup. One question though. What are you using to charge the batteries?

 

[SCE to AUX]

Very nice setup. One question though. What are you using to charge the batteries?

There is a 3 pin connector on the rear panel (lower right in 3rd picture, first post) which allows me to connect a battery charger (I use a small gel-cell charger from a hobby shop) or a cable with battery clips for use with an external battery.

 

[RimfireJim]

Very nice, SCE to AUX. Any club should be proud to have such a well-crafted system. Including the operating procedures within the case is a nice touch. I also like to see a wiring diagram included, visible when the system is opened up for repair.

I like your comment about making a wiring diagram AFTER making the system - that happens way more often in industry than one might expect

A word to the wise for those who are going to start scrounging industrial control switches: As SCE to AUX says, the "operator" (the part you see and touch) and the contacts are separate, so you can find, and make, all kinds of combinations of operators and contacts to get the action you want (momentary, on-off, off-on-momentary on, etc.) and the circuits you want (SPST, SPDT, DPDT, etc.). But operators and contacts aren't necessarily interchangeable between brands. They come in various sizes, too, the two most common being those that require a 22mm hole and those that use a 30mm hole.

One choice for multiconductor connectors is AMP CPC (circular plastic connector), available from Mouser, Digikey, etc. They come in 4, 9, 15, ? contacts. I believe the design is based on the more rugged metal military circular connector. The product line includes "crud" caps, keying pins, male and female styles, panel mount, in-line, . . . so you can make up just about any combination you need to keep things from being connected incorrectly. They all have threaded collars and built-in strain reliefs. The best way to attach the contacts to the wires is with a special crimper, but you can make do with pliers in a pinch (no pun intended), especially if you solder for extra reliability.

 

[powderburner]

Cost for the case and the panel frame was around $85 on eBay. The...batteries were...About $25 for the pair, IIRC.
The connectors ---The mating "crud caps" ---the oiltight switches ---the 4 indicator lights ---A single pushbutton switch might cost $30

I'm sure you are correct on the ridiculous prices for MIL-SPEC hardware (I work at a place with some amazingly-priced components) but it would probably be possible to come up with some near-equivalent substitutes, at least for some of it?

What I wish someone would do is to buy these parts in enough bulk to offer us a "kit" where we could still save some bucks over ordering by ourselves and buying in onesies and twosies. I would hope that there would be some savings in buying some component maybe 50 at a time instead of singly. A kit would also save paying a $5 or $10 shipping charge for each separate part, from five to ten separate supply houses. Maybe it's not worth it for one of our vendors to mess with stocking a DIY kit, but it would sure be nice. Design it so someone can hook up to a $20 lawnmower battery purchased locally, and keep it simple.

A "standardized" launcher and controller would also make it possible for each of us to post qstns about glitches or failures, and get some expert feedback from someone else already familiar with the system (without having to start with figuring out new circuit designs every time). And when you invite someone from another club to bring their gear you could have some confidence that their hardware would be compatible with yours.

One of the biggest advantages, I think, would be having a complete package of electrical components to point to for new clubs, school groups, etc, who might be looking for an economical launcher system. They often have some volunteers who can give some time for assembly if the club cannot afford a pricier turn-key system. And I know a lot of groups go "ugh" and quit immediately when you tell them they have to order one part from here, two from there, one more part from somewhere else, etc.

SCE, that thing looks really nice! Are you going to tell us what all those buttons do?

 

[SCE to AUX]

SCE, that thing looks really nice! Are you going to tell us what all those buttons do?

You can actually read the operating instructions if you enlarge the final picture.

A quick rundown:

Silver keyswitch (upper left corner)--Main Power switch. When turned on, it applies power to the system. Key is removable only in OFF position.

Yellow button--System Arm. When pressed, it latches in an internal relay, enabling the firing circuit.

Red button--Abort switch. Will drop out the latching arm relay, halt and reset the countdown timer (if running), and disable the firing circuitry.

Digital Voltmeter (lower left)--Reads current battery voltage.

Sonalert--Audible beeper for continuity test.

Timer module--Used for automatic launch at the end of a countdown. Adjustable from 0.01 to 99.99 seconds duration. Can also be used as a "stopwatch" to time things like duration contests, etc.

Grey button--Circuit Check. Press to test igniter circuit continuity.

Red guarded toggle switches (6)--Pad Select switches.

Rotary selector switch (center of panel)--Mode Select. Selects between countdown (launch by internal timer) or manual (launch when button is pressed) mode.

Green button--Launch Button. Launches selected pads when pressed (manual mode), or starts countdown timer (countdown mode).

Indicator lights:

Green--Power ON
Yellow--System Armed
White--Continuity OK
Red--Firing

 

[RimfireJim]

Powderburner,

That sounds like a good idea, and there's no reason it couldn't work, but I'm guessing it's wishful thinking:

1. The cost savings from going to qty 1 to qty 50 isn't great. I checked out a few components like switches and connectors on mouser.com and it looks like a 10-25% reduction (not counting savings on shipping due to combined orders). That's not much to cover someone's time (unless it's volunteered), carrying cost and risk. One couldn't justify it as a business without a markup. But, yeah, maybe as a hobbyist-to-hobbyists service.

2. Are there really enough people who would be satisfied with the same design? Maybe so, but I have a suspicion that there are those who want simple-as-possible, those who want some bells, those who want some whistles in addition to bells, some who want a relay launcher, some who want multi-pad capability, built-in batteries, separate batteries, etc., etc., etc.
Reminds me of fire trucks: there is no practical reason that a few different models could handle all the needs of every fire department in the country at some (substantial?) cost savings due to standardization, but the custom fire apparatus business continues (after years of tradition unimpeded by progress, as the saying in the industry goes) because fire chiefs can and do order custom rigs, justified by their special "needs". (And the tax-paying public pays for it.) There are, I'll admit, some companies that have carved out a niche by offering standard, stock models, which are popular with the more budget-conscious departments. So, maybe that's the equivalent of the budget-conscious hobbyist who would be happy with a standard launcher. Doesn't Pratt Hobbies offer something along those lines? (I'd look it up, but their website is tagged as "malicious" by my IT department filter - hmmm.)

 

[SCE to AUX]

Pratt Hobbies has their "Go Box" single pad controller, as well as a line of hybrid-oriented GSE. Here's their "sixpack" club launch box:

I have to say that for $150, one would hope that they could at least get all the launch buttons in a straight row! And the idea of using standard AC extension cords between the controller and the pads may be a cost-saver, but it is also an electrical code violation.

I make a living building custom one-off and prototype electronic gear. If somebody wants a custom launch controller, let me know. But once you get away from the simple, single pad "personal" launch controller, there are just too many variables for a single "standard" solution that would please everyone.

How many pads? HPR, LPR or both?
Relay or direct system?
Wired or wireless connection to pads?
Self-contained or external batteries?
How many bells and whistles? Timers, voltmeters, lots of indicator lights?
Special packaging? Waterproof, rackmount, etc.?
Cost/size/weight constraints?
Interface to existing equipment needed?

Anything of this nature should start with a detailed analysis of needs/wants and a formal proposal before anything gets built.

 

[davel]

Those 'circular' connectors are much cheaper in plastic, and they work almost as well as the militarized versions.
https://www.action-electronics.com/ampcpc.htm

 

[Bazookadale]

And the idea of using standard AC extension cords between the controller and the pads may be a cost-saver, but it is also an electrical code violation.

Just wondering, since 2 clubs I fly with use AC cords what code are we violating?Is it a safety issue?

 

[SCE to AUX]

The actual code being violated is NFPA 70, better known as the National Electrical Code (NEC). The exact code citation I would have to look up (don't have my NEC handy at the moment), but the crux of it has to do with use of connectors which are ubiquitous for 120V AC service for a low voltage DC application. Theoretically, it would be possible (at a launch site that has AC power available, anyway) to accidentally cross-connect the launch system wiring with the AC power system. This would create a serious shock hazard at the pads/controller. If nothing else, it would be a violation of Article 110.3(b), which prohibits the use of electrical equipment in a manner inconsistent with its "listing and labeling" requirements. Unless the cord and receptacles are labeled by the manufacturer for use at low voltage (and they aren't), such use is technically a NEC violation.

As a practical matter, probably not a serious hazard unless your launch site also has AC receptacles available near the pads or LCO table. But I certainly wouldn't sell such a system commercially like Pratt is doing. Eventually, somebody is going to do something stupid, get hurt (or worse), and the manufacturer is going to get dragged into court with a pretty solid case against them.

 

[jadebox]

Did I miss something? Where's the SCE switch?

-- Roger

 

[SCE to AUX]

The SCE is external.

The rear panel "Ext. 12V Pwr." connector gets used to power a video receiver when I fly my camera rocket.

 

[jadebox]

The rear panel "Ext. 12V Pwr." connector gets used to power a video receiver when I fly my camera rocket.

Wow ... that probably requires a really long extension cord! [Edit: Oh, "video receiver." I was picturing you powering the onboard camera with it.]

Seriously, that's a very nice launch controller. It's definitely something to be proud of.

-- Roger

 

[RimfireJim]

Those 'circular' connectors are much cheaper in plastic, and they work almost as well as the militarized versions.
https://www.action-electronics.com/ampcpc.htm

Uh, yeah - see my post #8 above

 

[JRThro]

I make a living building custom one-off and prototype electronic gear. If somebody wants a custom launch controller, let me know. But once you get away from the simple, single pad "personal" launch controller, there are just too many variables for a single "standard" solution that would please everyone.

How many pads? HPR, LPR or both?
Relay or direct system?
Wired or wireless connection to pads?
Self-contained or external batteries?
How many bells and whistles? Timers, voltmeters, lots of indicator lights?
Special packaging? Waterproof, rackmount, etc.?
Cost/size/weight constraints?
Interface to existing equipment needed?

Anything of this nature should start with a detailed analysis of needs/wants and a formal proposal before anything gets built.

Even something pretty simple and built into a plastic toolbox would turn out to be fairly expensive if you built it as a one-off, don't you think?

Say something like this:

* 4-pad, up to G motors
* direct wired, no relay
* typically launch 1 pad at a time, but allow simultaneous launch of 2, 3, or 4 pads as well
* self-contained 12V batteries, but allow external connection if need be
* continuity check pushbutton and light
* arming switch with removable key; system is disarmed if key is removed
* buzzer and light when armed
* launch pushbutton
* mount in plastic Plano-type toolbox, to be carried by hand
* no timers, no wireless, no voltmeters, no interface to any other equipment
* wiring to pads should plug in to controller or otherwise be removable, and end in flat-faced stainless micro-clips at the pad end.

 

[RimfireJim]

Even something pretty simple and built into a plastic toolbox would turn out to be fairly expensive if you built it as a one-off, don't you think?

Say something like this:

* 4-pad, up to G motors
* direct wired, no relay
* typically launch 1 pad at a time, but allow simultaneous launch of 2, 3, or 4 pads as well
* self-contained 12V batteries, but allow external connection if need be
* continuity check pushbutton and light
* arming switch with removable key; system is disarmed if key is removed
* buzzer and light when armed
* launch pushbutton
* mount in plastic Plano-type toolbox, to be carried by hand
* no timers, no wireless, no voltmeters, no interface to any other equipment
* wiring to pads should plug in to controller or otherwise be removable, and end in flat-faced stainless micro-clips at the pad end.

So, that would be one SPST key switch, two SPST pushbutton momentary switches, four SPST maintained toggle (?) switches, two lights, one buzzer, five connectors, batteries, and a case. And a fuse holder or circuit breaker. Plus charger for batteries? I'm going to ballpark it at $300 for those materials alone at commercial prices, NOT industrial grade but not cheap crap either, i.e., something I would feel OK about selling to a customer. Price could easily be 50%+ higher for industrial grade components. Add labor at technician rates for anything but a bag of parts. It's pretty timing consuming building these kinds of things (especially the first one!): laying out and drilling holes, mounting components, wiring everything up neatly, labeling, testing.

I'm going to guess this is out of range for most individual users, but it could make sense for a club if they don't have someone who likes to scrounge for parts and build electrical gadgets.

 

[SCE to AUX]

Jim pretty much nailed it, but forgot all the cables (and wire isn't cheap nowadays). G motors require a 30' minimum standoff distance, so you will need a minimum of 120' of cable for 4 pads.

Unless you had a large number of advance sales, there isn't going to be much of a price break available on decent grade parts. Not many individual flyers would pay $150+ for a single pad launch controller kit, which is about where you would need to price it to sell in small quantities and still turn a profit. This is assuming the use of high quality commercial (not milspec) components. No crappy Chinese switches or questionable shortcuts like using AC receptacles for cable connectors.

You might be able to sell a few multipad kits or finished controllers to well-funded clubs or school rocketry programs, but how many of them are in the market for a launch system, but don't have someone involved who can scrounge parts locally for a better price?

 

[JRThro]

That's more than I expected, but not outrageously more.

So yeah, having SCE to AUX or another individual design, build, and check out these things as one-offs would be prohibitively expensive.

 

[RimfireJim]

Jim pretty much nailed it, but forgot all the cables (and wire isn't cheap nowadays). G motors require a 30' minimum standoff distance, so you will need a minimum of 120' of cable for 4 pads.

Dang! You caught me That's why I'd never come up with more than a "ballpark" w/o doing a more thorough costing. And having better specs. 16 ga. 2-conductor cable can run anywhere from $.25/ft to well over $1/ft. You want 14 ga.? Add $$

 

[powderburner]

I'm sure you guys are correct on these price estimates, and that you really don't want to try to go "cheap" on components that you would be selling to the public. It just seems a shame that this is such an expensive undertaking, because prices like the ones mentioned are what keep lots of small clubs from buying this stuff.

Schools cannot spend much more money on launch equipment than a $20 starter special on sale for 40% off. Heck, schools around here can't even afford normal supplies like zerox paper and kleenex, they have the students bring it at the start of the year to stock up.

SCE, I still would like to see that schematic-

 

[Chrisn]

$300? Are you kidding me, maybe $100 with good components, and thats in a weaker currency than yours!

 

[JRThro]

$300? Are you kidding me, maybe $100 with good components, and thats in a weaker currency than yours!

Chris, can you price the components in $NZ and see what you come up with?

 

[Chrisn]

Going off the components listed by RimFireJim, minus battery's and a box, I get $57NZD. Components here are also way more expensive than what you have available in the US

 

[SCE to AUX]

Going off the components listed by RimFireJim, minus battery's and a box, I get $57NZD. Components here are also way more expensive than what you have available in the US

What components are you looking at to get such low prices? Generic far-east import parts from hobbyist suppliers, or brand-name commercial grade stuff?

 

[Chrisn]

An AU/NZ electronics dealer, looked at 2 different ones and they are about the same price and quality, you cant be that fussy, also looking through the digi key catalouge, not that much difference in cost.