Building a 6 ft replica of the Higgs Farm Square Rocket

eggtimer rocketry
Onebadhawk
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Don't forget to add the "Feet" they are not present in the mini kit!!! for visual look at the photos of Tom's rocket that is on the kit instructions!
 
DAllen said:
Wow. What a unique and impressive build. Very neat and clean techniques there.

I wonder if maybe you could have gotten away with not having the fiberglass tubes inside the rocket? That would have saved a bunch of weight for sure.

Anyways, thanks for taking the time to share this.

-Dave
Click to expand...

I thought about designing it without an inner fiberglass airframe but was uncertain if it would be strong enough. And I think it was easier this way, although pretty heavy. I had originally planned to use 1/8" plywood but it was too flimsy so I went with the 1/4" which added more weight.

beeblebrox said:
Don't forget to add the "Feet" they are not present in the mini kit!!! for visual look at the photos of Tom's rocket that is on the kit instructions!
Click to expand...

Mine has the feet. I didn't need to refer to the photo on the mini kit instructions, I took lots of photos of Tom's big rocket at MDRA last year when I was designing this.
 
I finally flew my Square Rocket yesterday, which has been standing in the corner of my dining room since I finished it 7 months ago. It went 1526 ft on a CTI K1200 White Thunder. Very stable, no problems. And to top it off, Tom Cohen also flew his huge original Higgs Farm Square Rocket on the same day!


32858519408_ed49fca1c1_o.jpg

Photo by J. Craig Klimczak
 
It's okay with me as long as it's okay with the RCO. I doubt that there has ever been a drag race between the A rack and the away cell.

Im pretty sure that I will win the drag race with Tom's rocket because it will take his big 98 mm motor a couple of seconds to get up to pressure. By the time he leaves the pad I'll probably already be 500 ft up. To make it fair the RCO should probably give him a head start.
 
Nathan said:
It's okay with me as long as it's okay with the RCO. I doubt that there has ever been a drag race between the A rack and the away cell.

Im pretty sure that I will win the drag race with Tom's rocket because it will take his big 98 mm motor a couple of seconds to get up to pressure. By the time he leaves the pad I'll probably already be 500 ft up. To make it fair the RCO should probably give him a head start.
Click to expand...


That would be beautiful. Ripple fire the 98,75, and 18 with a timing of best guess for ignition.

Try and setup a forced perspective photo where they're lined up at a similar scale :cool:
 
I will suggest that. Mine will be 54 mm though, not 75. I selected the 4 grain 54 mm K940 because it should give me a flight profile similar to Tom's big rocket on a M6400.

FYI, Tom says that this is his last M6400 Vmax and CTI doesn't make Vmax reloads anymore. The MDRA motor wizards have an EX motor in the works for him that they expect will have a similar thrust curve.
 
Oh gosh this has given me more encouragement to get it done! My plan was to use a E15-7 (its 24mm but I left out the motor hook). so 24mm, 54mm, and 98mm XD this will be great!
 
Nathan said:
FYI, Tom says that this is his last M6400 Vmax and CTI doesn't make Vmax reloads anymore. The MDRA motor wizards have an EX motor in the works for him that they expect will have a similar thrust curve.
Click to expand...
Try the Aerotech M6000 Super Thunder. Performance very close to Vmax.
 
My Square Rocket was badly damaged last weekend when I flew on a CTI 6 grain 54mm K820 Blue Streak at Battlepark. This was the 8th flight of the Square Rocket. Right after leaving the pad the motor over-pressurized and blew out the nozzle. The rocket cartwheeled, the altimeter fired, and the chute came out. But it was only about 100 feet up, not quite enough time for the chute to open so it crashed hard. The airframe appears to be okay and the nose is fine, but the fins received a lot of damage. The Aeropack retainer was also partially sheared off. I might be able to repair the fins but a bigger problem is that what's left of the motor casing is lodged in motor tube. There is not enough left of the casing to pull it out. I tried grabbing on to the jagged edges with pliers but it doesn't budge. I can't push it out from the top end because the threaded rod for the upper rail button goes through the airframe just forward of the motor tube. If I can figure out a way to got the casing out of the motor tube then I would still need to come up with another way to retain the motor.

At this point I don't think that I will attempt to repair it. The nose, which was a complex part to build, is undamaged. I may just build another Square Rocket and just reuse the nose. If I do build another one the changes I would make would be to give it a 75mm MMT and make it dual deploy.

50591583516_2d3f45819b_b.jpg


50590848118_401f2f2f92_b.jpg
 
Ah crap! :(

Sorry to see this result. This was a motor issue out the rear, not a burn through near top of case?
 
rfjustin said:
Ah crap! :(

Sorry to see this result. This was a motor issue out the rear, not a burn through near top of case?
Click to expand...

Correct, the forward closure didn't fail. I've seen plenty of forward closure failures and they always result in flames shooting out the forward end of the rocket. That didn't happen and the chute wasn't burned at all. The motor just blew out the nozzle with a loud bang, shearing off the end of the casing and taking a big chunk of the Aeropack retainer with it.

Does anybody know if CTI still has the policy of replacing a motor casing for free in the event of a CATO? I sent an email to AMW a few days ago about that but no reply. I'm going to need a new 6 grain 54mm case and rear closure.
 
Sickens me to see images like that.

Before you consign it to rubbish...

Could you fabricate a compression plug using a piece of solid rubber 'dowel' on a length of all thread? Double nut (or aircraft locknut) then washer then the rubber plug with an outside diameter just a bit smaller than the ID of the motor casing, followed by another washer and a nut that you could tighten down to compress the rubber plug such that it swells and lodges inside the motor casing? Leave the all thread long enough that you could attach something else to it that would allow you to pull on that axis?

Similar to an auto body slide hammer, but instead of threading into sheet metal bodywork, the rubber plug would be wedged into the motor casing...
 
David_Stack said:
Sickens me to see images like that.

Before you consign it to rubbish...

Could you fabricate a compression plug using a piece of solid rubber 'dowel' on a length of all thread? Double nut (or aircraft locknut) then washer then the rubber plug with an outside diameter just a bit smaller than the ID of the motor casing, followed by another washer and a nut that you could tighten down to compress the rubber plug such that it swells and lodges inside the motor casing? Leave the all thread long enough that you could attach something else to it that would allow you to pull on that axis?

Similar to an auto body slide hammer, but instead of threading into sheet metal bodywork, the rubber plug would be wedged into the motor casing...
Click to expand...

I was trying to think of something like that which I could use to get a grip on the casing from the inside. What you are describing sounds similar to the rubber freeze plugs that are used to winterize plumbing in swimming pools. I'm not sure it would grip the inside of the casing firmly enough though.

I haven't totally given up yet, I want to try to bang the casing out from the top. I'm going to try hammering it out with a piece of steel rebar. That should be narrow enough to get past the threaded rod above the motor tube.

If I can get the casing out I still have problems with the fins. One of the fin base parts is bent. I didn't know you could bend G10 fiberglass but this one is bent. I might be able to straighten it by sandwiching another piece of G10 on it.
 
I'd try something like a tapered pharmacist's spatula. Get it in between the casing & motor tube & work it around and maybe spray some kind of lubricant in that space. And I'd try slicing the motor case with something like a utility knife, awl, etc & prying up that area so you can get a good grip with a needle nose pliers. And when I'm trying to remove something I usually use my vise-grip needle nose.
 
Nathan said:
Correct, the forward closure didn't fail. I've seen plenty of forward closure failures and they always result in flames shooting out the forward end of the rocket. That didn't happen and the chute wasn't burned at all. The motor just blew out the nozzle with a loud bang, shearing off the end of the casing and taking a big chunk of the Aeropack retainer with it.

Does anybody know if CTI still has the policy of replacing a motor casing for free in the event of a CATO? I sent an email to AMW a few days ago about that but no reply. I'm going to need a new 6 grain 54mm case and rear closure.
Click to expand...

Fill out the warranty form and send it to AMW, we'll get you a new case and closure. My appologies for the failure.
 
I finally finished repairing my Square Rocket, although I will probably touch up the paint when it warms up enough in the spring. A chunk of the Aeropack retainer got blown off but after filing down the jagged edges there is still enough of it left to screw on the retainer cap and hold the motor securely. A couple of the fin parts are not exactly straight anymore so I should change the name to the Not Quite Square Rocket.
50966552508_95a2863c9a_c.jpg


50967255376_59c070d767_c.jpg
 

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