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Launch Model Rocket Using This XL Rocket Launcher?


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#1 DLuders

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Posted 27 March 2010 - 09:01 PM

Several years ago, I designed a 100% Lego flying model rocket that uses Estes C6-5 or C6-7 black powder model rocket motors ( http://mocpages.com/moc.php/104238 ).  Yes, it really can fly but it has no parachute and I have to collect all of the pieces after it smashes into the earth (i.e., a "Bucket Recovery" method)   :tongue:  .   It's still intact in my basement.  To launch the smallest one pictured off of a remote-controlled Lego vehicle, I've been wanting to create a MOC similar to this 8-wheel, Power Functions XL-scale #6950 "Mobile Rocket Transport" ( http://mocpages.com/moc.php/90309 ).   :thumbup:

My question is, do you think there's a way of launching my Lego rocket off of the XL-scale Mobile Rocket Transport?  The trick is to develop enough TORQUE to lift my rocket upwards from a horizontal to a vertical position.  The tilting mechanism would have to work SLOWLY, and then move the butt of the rocket outwards off the end of the truck (so that the hot flame doesn't melt the Lego pieces!).  Do you think that it is POSSIBLE to DRIVE a model rocket around and actually LAUNCH IT using remote-control?  I would have to use a short, metal launch rod to guide the rocket upwards for the first 3 feet.  Lego Linear Actuators don't have anough range of movement to do the job (although I could use these Lego-compatible jumbo Linear Actuators with a 4" stroke available from http://store.firgell...-actuators.html ).  Any suggestions?  (Blakbird, I know you flew rockets at Mansfield like I did, so your insight would be appreciated).  

(P.S.  I know that the National Association of Rocketry has a code whereby rockets shall not be tilted more than 30 degrees from vertical, so I would test-launch my rocket on my own huge field just in case it launched prematurely like a Cruise Missile)....   :hmpf:

#2 Blakbird

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Posted 28 March 2010 - 05:05 AM

It would certainly be possible to launch an all LEGO rocket.  I've though about it for many years.  The first problem is that unglued LEGO has a hard time standing up to the thrust forces, so you either need to make it all in compression or build it of Technic.  Next problem is density.  LEGO is pretty heavy compared with what we typically use for rockets, at least when you build it strong enough to survive.

As for a mobile launcher, that shouldn't be too hard.  BP motors will ignite with only 6V, so the 9V available from a PF system should be enough.  I'd just clip the wires coming from the IR receiver and attach them to the igniter.  When you use the controller, you'll short the circuit and fire the rocket.

Next problem for a mobile launcher is heat.  If the exhaust plume hits your launcher, it will be destroyed.  ABS can't stand up to that heat.  You'd need a blast deflector of some kind.

A parachute is possible with enough space.  If you make it that big, it's going to be heavy.  But that's when my favorite motto comes in:
"Just add more power"
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#3 DLuders

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Posted 28 March 2010 - 01:53 PM

Thanks for the feedback, Blakbird.  You may have misunderstood -- the smallest of my three rockets shown on  http://mocpages.com/moc.php/104238  REALLY FLIES and it has proved itself in at least three ~300'-high flights.  The 100%-Lego rocket (using no glue) has withstood the compressive forces and and is aerodynamically stable.  There isn't any room for a parachute but after a "bucket recovery" I just snap the pieces back together for another flight (but my NAR club frowns upon it).  The four white slopes (acting as "fins") do get a little carbon and scorching on them so if they get to "grody" I can just replace them.

I appreciate your guidance on how to activate the igniter.  My main challenge now is to have a POWERFUL tilt-up launcher that has enough torque to lift the rocket up from a horizontal to a vertical position.  Do you know of any official Technic set that has instructions that I could mimic?  I know that there are Technic cranes, fire trucks, etc. -- whcih one could best be adapted to tilt a rocket?

The back end of the trailer can be built with some of those Lego-compatible custom ALUMINUM LIFTARMS available from a Florida USA Bricklink Store named "Inaminate Reason" ( http://www.bricklink...mp;itemStatus=U ).  The aluminum won't melt like the Lego ABS plastic would, and can be cleaned up with a White Vinegar bath just like any other launch rail.    :sweet:

By the way, I'm impressed by your yellow High-Power rocket.  Did you fly it at FITS in Mansfield, at Brothers or at XPRS at Black Rock?  I only got to HPR Level 2 certification....

#4 Ras_Al_Ghul

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Posted 29 March 2010 - 02:04 AM

While reading this topic, I can't help but think you could (if you have the parts) mod CP5670's annihilator to work.
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#5 Blakbird

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Posted 29 March 2010 - 02:16 AM

View PostRas_Al_Ghul, on Mar 28 2010, 07:04 PM, said:

While reading this topic, I can't help but think you could (if you have the parts) mod CP5670's annihilator to work.
Possibly.  I've built it, and the Annihilator can't lift much, nor can any Technic creation due to the torsional limitations of plastic axles.  The model uses counterweights to make it possible.  I'd recommend doing the same thing with the rocket, or at least mounting the rocket so it rotates at it's CG.  In order to do this, it would have to hand off the back of the launcher.
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#6 CP5670

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Posted 30 March 2010 - 01:31 AM

That might make an interesting mod project for that model. :grin: You would have to get the rockets down to a much smaller size and weight for it to work though.

Quote

To launch the smallest one pictured off of a remote-controlled Lego vehicle, I've been wanting to create a MOC similar to this 8-wheel, Power Functions XL-scale #6950 "Mobile Rocket Transport" ( http://mocpages.com/moc.php/90309  ). default_thumbup.gif

Someone had made an even larger version of 6950 at Brickfair last year. I don't think it was functional but it looked magnificent.

Edited by CP5670, 30 March 2010 - 01:31 AM.


#7 allanp

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Posted 01 April 2010 - 07:22 PM

Well if you want a very slow movement have you thought about using long gear racks, similar to the mechanism used to lift the container on the back of the 8479 barcode truck, but much beefier obviously. This method would be much more efficient than LAs and you could have a much longer reach.

Edited by allanp, 01 April 2010 - 07:26 PM.

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#8 DLuders

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Posted 03 April 2010 - 04:53 PM

Well, I just won a custom aluminum SPUR GEAR KIT from Inanimate Reason ( http://www.bricklink...InanimateReason  and http://inanimatereason.com/shop/  )  , so I'm going to use it for MAXIMUM TORQUE to lift the rocket+launch tower up off of its trailer:   :cry_happy:

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Edited by dluders, 03 April 2010 - 04:59 PM.


#9 Techydude

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Posted 03 April 2010 - 09:21 PM

View Postdluders, on Apr 3 2010, 08:53 AM, said:

Well, I just won a custom aluminum SPUR GEAR KIT from Inanimate Reason ( http://www.bricklink...InanimateReason  and http://inanimatereason.com/shop/  )  , so I'm going to use it for MAXIMUM TORQUE to lift the rocket+launch tower up off of its trailer:   :cry_happy:

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Apparently you can increase the gear ratio on that very spur gear kit from Inanimate Reason to 10:1 with the addition of a couple of small gears, for about 30 bucks.  You can also increase it to 25:1 for about 60 bucks.  Or combine both add-on kits and get 50:1 for about 90 bucks.  I believe that both these add-on kits are available on special order only from Inanimate Reason.   I hear they also have a simple linear actuator that have 4, 6, 9, and 12 inch travel, for relatively cheap, since it doesn't come with a motor.  You can use an XL motor to drive it and gear the plastic Lego gears to any ratio you want since there is no backwards torque transmitted beyond this linear actuator's metal worm gears.  I think this guy Bob Shaw will do custom anything for a decent price.  Just contact him through his site.

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#10 allanp

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Posted 04 April 2010 - 11:30 AM

Awwww come on, that's just cheating  :laugh:  :grin:
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#11 DLuders

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Posted 04 April 2010 - 03:51 PM

View Postallanp, on Apr 4 2010, 04:30 AM, said:

Awwww come on, that's just cheating  :laugh:  :grin:
Yeah, I know -- the use of custom Technic-compatible stuff is "cheating".  However, from the discussion above, one already can see that the use of normal Lego bricks made of ABS plastic WON'T WORK for a rocket launcher because the heat of the exhaust gases will melt everything.  Also, there isn't enough TORQUE available from regular Lego parts -- the plastic will crack from being overstressed.

I have a 100%-Lego rocket that has flown 3 times.  My question to you is this -- is it better to ABANDON the project to build a launch tower off of a Lego vehicle, or PURSUE the project and have a HYBRID plastic/aluminum deal?  I thought the whole idea was to "Build Well" -- you know, the JOY OF BUILDING.  TLG has a motto something like, "Joy of Building, Pride in Creation".  Who gets bonus brownie-points for building 100%-Lego items anyway?  I'm not in some sort of contest.  Nobody else has built something like this (as far as I can tell), so I'm going to build it.

#12 Jetro

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Posted 05 April 2010 - 01:52 PM

So how about launching it using other means? We had some great fun with a plastic bottle half full of water and a manual pump for the bike....

#13 allanp

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Posted 05 April 2010 - 02:17 PM

View Postdluders, on Apr 4 2010, 03:51 PM, said:

Yeah, I know -- the use of custom Technic-compatible stuff is "cheating".  However, from the discussion above, one already can see that the use of normal Lego bricks made of ABS plastic WON'T WORK for a rocket launcher because the heat of the exhaust gases will melt everything.  Also, there isn't enough TORQUE available from regular Lego parts -- the plastic will crack from being overstressed.

I have a 100%-Lego rocket that has flown 3 times.  My question to you is this -- is it better to ABANDON the project to build a launch tower off of a Lego vehicle, or PURSUE the project and have a HYBRID plastic/aluminum deal?  I thought the whole idea was to "Build Well" -- you know, the JOY OF BUILDING.  TLG has a motto something like, "Joy of Building, Pride in Creation".  Who gets bonus brownie-points for building 100%-Lego items anyway?  I'm not in some sort of contest.  Nobody else has built something like this (as far as I can tell), so I'm going to build it.

Oh by all means pursue it. I personally would not if it meant using non-lego parts but that's just my own choice.  :classic:
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#14 roamingstudio

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Posted 07 April 2010 - 04:46 PM

If you want to keep as much Lego as possible look out for Mindsensors and HiTechnic stuff - as well as the new Tetrix elements. They are compatible with NXT designs but do allow aluminium elements which can be integrated into normal Lego models. Not quite the true Lego route - but probably acceptable since they are all Lego registered / sanctioned.



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