Tube Coupler Hack

[brockrwood]

I needed a tube coupler to join two Quest 35mm tubes together to make a Frankenrocket out of two old rockets that had both been damaged (a Bright Hawk and a Big Rage).

I had no tube coupler of the proper diameter. I did have a tube coupler for a standard Estes BT-55 tube. The coupler is just a hair too small to join two Quest 35mm tubes.

A strip of Kraft paper and some Titebond III to the rescue. I just cut out a strip of Kraft paper to the right dimensions. I kept test fitting and cutting off a small strip, and test fitting it, until I got just the fit I wanted.

Then I smeared a nice film of Titebond III on the strip of Kraft paper and rolled the BT-55 coupler up in it as snugly as I could.

Voilà! Quest 35mm tube coupler!

It’s amazing what you can do with paper and glue.

 

[lakeroadster]

Genius

 

[brockrwood]

Genius

Well, I don’t know if it is genius, but I am proud of my little accomplishments in becoming a better model rocket modeler. I also really enjoy it when I apply a little “Yankee ingenuity” to a problem and it actually works. Plus, if a little trick I figured out helps one other rocketeer solve a problem, I am glad to post it to TRF. My ego gets stroked a little bit and another rocketeer gets a useful skill to use. Win-win.

Some of the folks here in TRF are master modelers (@lakeroadster and @milehigh come to mind off the top of my head) and I am in awe of the beautiful model rockets they create. Maybe one day my skills be at that level. But even if I don’t hit that level of expertise, trying to get there is a lot of fun.

 

[brockrwood]

Well, the hacked tube coupler works! Yay! Need to glue it in.

Need to lengthen the shock cord. Need to add a recovery device. Once those tasks are completed, Frankenrocket will be ready to test.

 

[Scott_650]

Are the strap-on Gnomes powered?

 

[neil_w]

It’s amazing what you can do with paper and glue.

Paper and wood (especially easy-to-work woods like balsa and, to a lesser extent, basswood) are an incredibly enjoyable and rewarding medium to work with.

The technique of adding layers of paper is always a go-to technique to enlarge something. I've used normal copy paper wrapped around the outside of 1/8" lite ply centering rings to tighten them up, or added a wrap of paper around a body tube to correct a loose centering ring that needs to slip over it. Just so easy to work with.

Plastic and 3D printing all have their place, but for me the joy of building rockets is paper and wood.

 

[brockrwood]

Are the strap-on Gnomes powered?

They sure are. I am going to put 13mm engines in them. I have some A10-PT’s, yhe plugged engines for rocket cars, to use in the boosters.

The boosters are really just for show - to provide more smoke and flame at liftoff. The problem I have is the ejection charges. What do I do with the ejection charges when the nose cones for the Gnomes are glued shut?

So I decided to use the plugged engines with no ejection charge. I have several packs of those.

My initial thought was to use 1/4A or 1/2A mini engines in the Gnome boosters. But those engines have ejection charges. So I drilled little holes in the top part of the Gnomes to let the ejection charge gasses escape. I was still worried about the Gnome boosters exploding because of the ejection charges, so I bought a few packs of the A10-PT plugged engines.

The problem with A10’s is that they are pretty powerful engines. Each booster is offset ny an inch from the center, main engine. If one booster does not light and the other one does, then there will be off-center thrust.

Maybe a C6 as the center engine would overwhelm the off-center thrust of an A10? I don’t know.

Any initial launch of the Frankenrocket will be a “heads-up” launch away from any potential bystsnders.









I used some translucent heatshrink tubing I had in my electronics parts bin to hold the engine hooks for the Gnomes in place.

 

[Back_at_it]

I found something similar when building my Quest Superbird. I wanted a real coupler and didn't want to use the crap plastic piece that Quest supplies.

Found that a single sheet of notebook paper wrapped around an Estes BT55 tube made a perfect Quest coupler.

 

[brockrwood]

I found something similar when building my Quest Superbird. I wanted a real coupler and didn't want to use the crap plastic piece that Quest supplies.

Found that a single sheet of notebook paper wrapped around an Estes BT55 tube made a perfect Quest coupler.

View attachment 520457

I didn’t think of using a piece of BT-55 TUBE as the coupler! I have lots of spare BT-55 tubes laying around. Thanks for the great idea! That will be done on the next Quest 35mm rocket hack.

This is a lower weight solution, too. The BT-55 tube coupler takes several wraps of paper to make it fit. It is a fairly heavy coupler when it is done. The BT-55 tube segment used as a coupler only requires one wrap of paper and less glue. It is lighter.

This is one of the things I love about TRF: The “why didn’t I think of that?” tips I get from other rocketeers.

 

[milehigh]

Hi, Brock,
I had just the same issue with a 35mm Quest tube.
I found that a BT-55 fits nicely inside the 35mm. By cutting some short pieces of the tubing, I was able to use them to thicken the BT-55 centering rings. There might be a pic of the process back in my 2021 binge-built that covers the motor mounts. It was done to add a 24mm motor mount for the booster stage of the "Cherokee-Icarus". The airframe tube was a 35mm from the Icarus kit.

 

[milehigh]

Here is the link to the blog post mentioned above:
https://castlerocketeer.blogspot.com/2021/10/binge-build-motley-mix-of-motor-mounts.html

 

[brockrwood]

Here is the link to the blog post mentioned above:
https://castlerocketeer.blogspot.com/2021/10/binge-build-motley-mix-of-motor-mounts.html

Thank you!

 

[LithosphereRocketry]

They sure are. I am going to put 13mm engines in them. I have some A10-PT’s, yhe plugged engines for rocket cars, to use in the boosters.

The boosters are really just for show - to provide more smoke and flame at liftoff. The problem I have is the ejection charges. What do I do with the ejection charges when the nose cones for the Gnomes are glued shut?

So I decided to use the plugged engines with no ejection charge. I have several packs of those.

My initial thought was to use 1/4A or 1/2A mini engines in the Gnome boosters. But those engines have ejection charges. So I drilled little holes in the top part of the Gnomes to let the ejection charge gasses escape. I was still worried about the Gnome boosters exploding because of the ejection charges, so I bought a few packs of the A10-PT plugged engines.

The problem with A10’s is that they are pretty powerful engines. Each booster is offset ny an inch from the center, main engine. If one booster does not light and the other one does, then there will be off-center thrust.

Maybe a C6 as the center engine would overwhelm the off-center thrust of an A10? I don’t know.

Any initial launch of the Frankenrocket will be a “heads-up” launch away from any potential bystsnders.

View attachment 520454





View attachment 520456

I used some translucent heatshrink tubing I had in my electronics parts bin to hold the engine hooks for the Gnomes in place.

From what I've seen, the offcenter thrust is nowhere near as bad for stability as you'd think. I have a strap-on booster rocket with about a 2" offcenter distance (E9 center, B6 outboards), and with one booster firing it stays more or less vertical. That's probably helped by the fact that there's asymmetric drag as well as the failed booster dropped away, but still.

 

[brockrwood]

From what I've seen, the offcenter thrust is nowhere near as bad for stability as you'd think. I have a strap-on booster rocket with about a 2" offcenter distance (E9 center, B6 outboards), and with one booster firing it stays more or less vertical. That's probably helped by the fact that there's asymmetric drag as well as the failed booster dropped away, but still.

Thanks! That was sort of my thought, too. These booster engines are not super far from the center line. They are not engine pods mounted on the tips of fins or anything.

I guess my other issue (not addresed yet), is what happens if both booster engines light but the center engine does not? My hope would be that the two A10’s would not have enough oomph to get the rocket off the pad. If so, no big deal other than two wasted A10-PT’s.

But if they just hoist the rocket, say, 50 feet into the air, then cease thrusting, down it comes, no parachute, crash.

I need to finish installing the shock cord and parachute, and then install engines. Then I need to weigh this monstrosity on the postal scale to see just how heaviy it will be when all prepped on the launch pad.

 

[neil_w]

I guess my other issue (not addresed yet), is what happens if both booster engines light but the center engine does not? My hope would be that the two A10’s would not have enough oomph to get the rocket off the pad. If so, no big deal other than two wasted A10-PT’s.

No need to guess or hope when you can simulate.

 

[brockrwood]

No need to guess or hope when you can simulate.

But OpenRocket no likey strap on boosters, correct?

 

[neil_w]

But OpenRocket no likey strap on boosters, correct?

15.03 no likey, new beta likey just fine.

 

[brockrwood]

15.03 no likey, new beta likey just fine.

Time to download! Thanks!

 

[PDawg]

Nicely done! I Shimmed a BT-55 nose cone in a Quest rocket using a small piece of BT-55 body tube as a shim. Hacks are a way of life. I wish Quest had normal sizes,

 

[Paul Howard]

Paper and wood (especially easy-to-work woods like balsa and, to a lesser extent, basswood) are an incredibly enjoyable and rewarding medium to work with.

The technique of adding layers of paper is always a go-to technique to enlarge something. I've used normal copy paper wrapped around the outside of 1/8" lite ply centering rings to tighten them up, or added a wrap of paper around a body tube to correct a loose centering ring that needs to slip over it. Just so easy to work with.

Plastic and 3D printing all have their place, but for me the joy of building rockets is paper and wood.

Yeah! Agreed!!!

 

[brockrwood]

Hi, Brock,
I had just the same issue with a 35mm Quest tube.
I found that a BT-55 fits nicely inside the 35mm. By cutting some short pieces of the tubing, I was able to use them to thicken the BT-55 centering rings. There might be a pic of the process back in my 2021 binge-built that covers the motor mounts. It was done to add a 24mm motor mount for the booster stage of the "Cherokee-Icarus". The airframe tube was a 35mm from the Icarus kit.

Look at that fit! An @Pem Tech BT-55 tube slips right inside the Quest 35mm tube. Tube coupler for Quest 35mm rocket! As @Back_at_it said, maybe it needs one layer of paper to make it a snug fit. No sweat. You guys are the best.

 

[brockrwood]

Nicely done! I Shimmed a BT-55 nose cone in a Quest rocket using a small piece of BT-55 body tube as a shim. Hacks are a way of life. I wish Quest had normal sizes,

I feel your pain. I have lots of kits from Estes and from Quest and from other manufacturers. The Estes body tube sizes are the de facto standard because of Estes’ historical and current substantial position in the LPR marketplace.

But there are lots of kits from Quest and other manufacturers that I think would make cool kit bashes with my Estes kits.

If I could get really skilled at making custom transitions between body tube sizes, all of my angst about kit bashing together Estes and non-Estes kits would go away.

Maybe it is time to bite the bullet and buy a 3-D printer? Besides all of the other fun stuff I could do with a 3-D printer, it seems to me that I could just print a perfect, plastic transition for any two body tube sizes whenever I need to.

 

[neil_w]

I feel your pain. I have lots of kits from Estes and from Quest and from other manufacturers. The Estes body tube sizes are the de facto standard because of Estes’ historical and current substantial position in the LPR marketplace.

But there are lots of kits from Quest and other manufacturers that I think would make cool kit bashes with my Estes kits.

If I could get really skilled at making custom transitions between body tube sizes, all of my angst about kit bashing together Estes and non-Estes kits would go away.

Maybe it is time to bite the bullet and buy a 3-D printer? Besides all of the other fun stuff I could do with a 3-D printer, it seems to me that I could just print a perfect, plastic transition for any two body tube sizes whenever I need to.

Paper transitions are easy. Just practice. The cardstock to practice with costs basically nothing.

 

[PDawg]

If I could get really skilled at making custom transitions between body tube sizes, all of my angst about kit bashing together Estes and non-Estes kits would go away.

I did this transition with a Quest 29mm tube to a BT50 for my Sub-Minimum F powered rocket. I used a 29mm to BT-50 centering ring (ASP Rocketry) and several layers of glue smoothed over with my thumb. I'm currently doing a BT55 to BT50 transition the same way for my next Puck Futin Rocket. Sadly all I got back from this Rocket was the nose cone but no complaints, someone here did a Rocksim for me and showed 2,800 feet.

 

[brockrwood]

I weighed this rocket with the parachute and shock cord installed: 117 grams! This mutant is heavy!

An Estes C6-5 center engine weighs 25.8 grams at liftoff.
An A10-PT weighs 7.4 grams at liftoff. There are two of them: 14.8 grams.

Total weight at liftoff: 157.6 grams. Call it 157 grams.

An Estes C6-5 has a maximum liftoff weight (per the Estes engine chart) of 113 grams.

This bird is too heavy for the single C6-5 center engine. At least one of the A10-PT's must light at liftoff!

Sheesh!

To get this bird safely off the pad I need a liftoff thrust equivalent to at least a single Estes C11.

So, when I launch it, I must cross my fingers that the center C6-5, and at least one of the A10-PT's, light. Without the extra power from at least one booster A10, the bird should not be able to get aloft. Or not very far aloft.

Hmm. What if the center C6-5 does not light but the two A10-PT's do light? The rocketreviews.com "combine motors" calculator says that I get average thrust of 4.7 newtons and total impulse of 4 newton-seconds (60 percent of a B engine). The initial peak thrust is about 25 newtons. Yes, the 25 newtons of initial thrust will likely get the bird off the pad. But the thrust ends at .85 seconds with only 4.7 newtons of average thrust. Just what I fear will happen will happen: The bird will get off the pad, soar 50 to 75 feet into the air, and then crash back to earth.

In fact, this rocket might be safer with just the C6-5 lighting. I don't think it will even get off the pad if only the C6-5 lights.

I need to create an OpenRocket simulation of these various scenarios to see just how bad the problem is.

Shoot. I should have upgraded the center engine mount to a 24mm mount when I built this thing. If I had done that, I could put a really powerful engine in the center and this problem would go away. No way to fix that now: That engine mount is glued in really well.

 

[brockrwood]

I did this transition with a Quest 29mm tube to a BT50 for my Sub-Minimum F powered rocket. I used a 29mm to BT-50 centering ring (ASP Rocketry) and several layers of glue smoothed over with my thumb. I'm currently doing a BT55 to BT50 transition the same way for my next Puck Futin Rocket. Sadly all I got back from this Rocket was the nose cone but no complaints, someone here did a Rocksim for me and showed 2,800 feet.

I like it!

 

[tsmith1315]

Paper transitions are easy. Just practice. The cardstock to practice with costs basically nothing.

This.

@brockrwood, go to payloadbay.com, print a few and glue them up with white glue.

Send me a PM if you want to try something a little different.

 

[BABAR]

I weighed this rocket with the parachute and shock cord installed: 117 grams! This mutant is heavy!

An Estes C6-5 center engine weighs 25.8 grams at liftoff.
An A10-PT weighs 7.4 grams at liftoff. There are two of them: 14.8 grams.

Total weight at liftoff: 157.6 grams. Call it 157 grams.

An Estes C6-5 has a maximum liftoff weight (per the Estes engine chart) of 113 grams.

This bird is too heavy for the single C6-5 center engine. At least one of the A10-PT's must light at liftoff!

Sheesh!

To get this bird safely off the pad I need a liftoff thrust equivalent to at least a single Estes C11.

So, when I launch it, I must cross my fingers that the center C6-5, and at least one of the A10-PT's, light. Without the extra power from at least one booster A10, the bird should not be able to get aloft. Or not very far aloft.

Hmm. What if the center C6-5 does not light but the two A10-PT's do light? The rocketreviews.com "combine motors" calculator says that I get average thrust of 4.7 newtons and total impulse of 4 newton-seconds (60 percent of a B engine). The initial peak thrust is about 25 newtons. Yes, the 25 newtons of initial thrust will likely get the bird off the pad. But the thrust ends at .85 seconds with only 4.7 newtons of average thrust. Just what I fear will happen will happen: The bird will get off the pad, soar 50 to 75 feet into the air, and then crash back to earth.

In fact, this rocket might be safer with just the C6-5 lighting. I don't think it will even get off the pad if only the C6-5 lights.

I need to create an OpenRocket simulation of these various scenarios to see just how bad the problem is.

Shoot. I should have upgraded the center engine mount to a 24mm mount when I built this thing. If I had done that, I could put a really powerful engine in the center and this problem would go away. No way to fix that now: That engine mount is glued in really well.

c5-3 should handle it easily

Your off center A10s are less an alignment problem (they aren’t that far off) but they won’t get the bird up to stable speed by the time it leaves the rod if central main doesn’t light.

There are good and bad sides to this.

Hopefully they are too weak to clear the rod or rail, so rocket settles back on pad.

If it does clear the pad, it will likely flop over on ground and land shark a few feet.

Good thing is, if main motor (which is your only recovery system initiator) doesn’t light, the A10 alone shouldn’t go very high, which since it would come in ballistic Is good.

As for couplers, toilet paper and paper towel tubes can often be cut to size to fit anything under their initial diameter. Sometime I will double them for strength.

Straight trails!

 

[brockrwood]

c5-3 should handle it easily

The C5-3 looks like the way to go for the center engine! Thanks!

(The two stores local to me that carry model rocket stuff do not carry the C5-3. Looks like I will have to order C5-3’s directly from Penrose.)

How can a C impulse engine in an 18mm case have a maximum liftoff weight of 227 grams? Is the nozzle special? Is the way the hole is drilled into the propellant special?

The C5-3 “Super C” has a maximum liftoff weight that is over 100 grams higher than a C6-5. How can this be?

 

[RocketTree]

The C5 has higher liftoff thrust, but then a lower maintained thrust for the rest of the burn.


C5


C6