Latest build: Trident T172-18 kit

[Joshua F Thomas]

Completed my Rocketarium Trident T172-18 kit. This kit is either a license or clone of the ARG kit of the same name, I'm not sure what the lineage is here. The kit is a replica of the Enerjet 2250/2260 sounding rockets, circa 1972-1976. It is a 18mm three-motor cluster.

The kit is pretty easy to assemble, and the fin alignment is made easier by the fact that they glue into the space between the engine mount tubes. Titebond II was used throughout this kit as the speeds and forces are not extreme. I used gap-filler CA in a few places just to smooth some things out. The hardest part of this entire build is ensuring that the engine tubes are glued together tightly enough that they can fit inside the diameter of the forward cluster bulkhead, necessary to make everything fit inside the BT-60 upper tubes. Very sparing use of glue is the way to go, and since you have three points of attachment, it's quite secure.

The paint colors here are the same as proposed on the kit, and what the Enerjet used. I have gone beyond the kit by basing the markings off the original Enerjet model, including the silver accents, which are not part of the kit. The decals were also printed by me, from a very handy plans.rocketshoppe.com source.

The upper tube [black] is a payload pay. The nosecone had no retention to the payload tube, and I worried a little about it coming off during flight or recovery, so I have tied a piece of kevlar cord to the attachment point on the nose cone and glued the other end to the interior of the payload bay. Purely there "just in case". The kit comes with an 18" plastic chute. I elected to use a 15" thin-mil nylon chute and a Top Flight chute protector.

81cm long, dry mass 170g. I worked up a detailed OpenRocket sim based on actual measured masses of each piece. Altitudes based on engine choice:

3x A8-3: 133 ft
3x B6-4: 403 ft
3x C6-7: 1033 ft
3x D16-8 [Quest]: 1442 ft

 

[Donnager]

Nice job. I'm finishing up a 29mm Rocketarium Trident. Just a little more paint to go. Probably won't get to fly until fall, though.

Let us know how it performs.

 

[Joshua F Thomas]

Nice job. I'm finishing up a 29mm Rocketarium Trident. Just a little more paint to go. Probably won't get to fly until fall, though.

Let us know how it performs.

Oof, that's the big one. What engines and expected altitude?

 

[GlenP]

I like their 13mm version, that would be a good fit for my small local flying field.

I wonder if you could make a booster, for black powder motors, in like a single 24mm to light that 18mm cluster as a sustainer. Might be marginal for max lift off weight.

 

[Donnager]

Oof, that's the big one. What engines and expected altitude?

Don't know, exactly. I've added significant epoxy fillets and an all thread retainer, and mine will be carrying an altimeter, so mine will be a little heavier than the advertised 24-25 oz.

Rocketarium says triple G40's will be in the 3200' range.

My sims, which still need a little work--
F-67's-1500ish--This is the motor I was kind of looking forward to.
G80's-4200ish
G138's-5200
H115's-LOL-maybe 5400
G138/H115 are very close to mach.
I suspect the high power motors might be just a little much.

Of course, my sims (which seem a little optimistic) still need a little work. The weights are not final as I haven't weighed the finished product, yet.

 

[Joshua F Thomas]

Don't know, exactly. I've added significant epoxy fillets and an all thread retainer, and mine will be carrying an altimeter, so mine will be a little heavier than the advertised 24-25 oz.

Rocketarium says triple G40's will be in the 3200' range.

My sims, which still need a little work--
F-67's-1500ish--This is the motor I was kind of looking forward to.
G80's-4200ish
G138's-5200
H115's-LOL-maybe 5400
G138/H115 are very close to mach.
I suspect the high power motors might be just a little much.

Of course, my sims (which seem a little optimistic) still need a little work. The weights are not final as I haven't weighed the finished product, yet.

Did you do any papering or extra strengthening on it, in case you want to do the near-mach flights?

Also how do you get the retainers on there? On the -18 there's no room for them, does the -29 have enough space between tubes to add them? Would be interested in seeing a pic.

 

[kuririn]

Also how do you get the retainers on there? On the -18 there's no room for them, does the -29 have enough space between tubes to add them? Would be interested in seeing a pic.

An all thread retainer is a threaded rod in the center of the tubes. The engines are typically secured by a washer and wing nut. Here's an example on the back of a 3X24mm Enerjet clone:

How does the Trident kit handle engine retention?
Love the finish on your build.

 

[Joshua F Thomas]

Oh, that's clever.... I wonder if I can still add that to my own rocket. I'll have to see if I can fit a threaded rod between the tubes with enough glue to hold it in place.

The Trident T172-18 kit does not use any engine retention. You need to use friction fitting. I can't speak for the larger size kits.

 

[Joshua F Thomas]

So that was an A+ idea for the threaded retainer, thanks for sharing that. I was able to determine a #6 machine screw would fit just right, but annoyingly the hardware store had no #6 threaded rods. So I just used a dremel to cut the head off a 2" #6 machine screw. Boom.

Put it in place with a generous amount of CA and let it set for an hour. Also CA'd together two washers of increasing size and a wing nut, so less likely to lose one of them. The result works great!

 

[kuririn]

Glad you like it.
I like to use epoxy, preferably JB Weld since it's in the nozzle area.
Looking forward to your flight report.

 

[Joshua F Thomas]

Glad you like it.
I like to use epoxy, preferably JB Weld since it's in the nozzle area.
Looking forward to your flight report.

Me too! Possibly a Sunday launch. Trying to get the family to come out.

 

[Donnager]

Did you do any papering or extra strengthening on it, in case you want to do the near-mach flights?

Also how do you get the retainers on there? On the -18 there's no room for them, does the -29 have enough space between tubes to add them? Would be interested in seeing a pic.

No fin papering. I normally use wood hardener, a few coats. On this one, I have a pretty nice Hysol epoxy fillet situation. I am a little leery of the transonic stuff so I was just giving numbers there. Mine will probably stay in the high F or low G range.

 

[Jeff Curtis]

I flew my Trident T172-18 on 3 B6-4s. Only 2 lit but I still got a fairly stable flight. I just wrapped masking tape round the 3 engines and the motor mount tubes and the motors were still there when I recovered it.

 

[Joshua F Thomas]

I flew my Trident T172-18 on 3 B6-4s. Only 2 lit but I still got a fairly stable flight. I just wrapped masking tape round the 3 engines and the motor mount tubes and the motors were still there when I recovered it.

I wanted to try on B6-4s but it appears I'm one short. I'm going to try later today with A8-3s - it will be a low flight but I won't have to worry about losing it. Will be good test of cluster launch.

 

[Joshua F Thomas]

The Trident flew successfully on 3x A8-3s, barely over 100 ft up. Nearly hit me on the return after deploying chute. On the plus side, I validated I am able to successfully ignite three motors together.

 

[Dee55]

Very nice rocket.. I would love to see that in flight.