"Faster Buddy, Faster!" Build Thread

This will be my first post on these forums so I will start with a brief introduction. My name is Brian Schwartz. I am a mechanical engineer and work designing automation machinery. I also have experience in machining (cnc and manual including 2 years in the guitar industry), welding, electronics and, software development. My primary hobby is combat robotics, I build killer robots ranging from 1 pound to 340 pounds. I also run the Chicago Robotic Combat Association and put on an annual competition at the iHobby Expo. As a general rule I over do everything and I build things to be rock solid.

As to my experience in rocketry, as a kid my brothers and I build lots of Estes and scratch built rockets and eventually my father started flying high power. We traveled with him to a number of local launches but then he fell out of the hobby for a while and so did we. A few years ago my father started building again and has gotten my daughter involved with a number of Estes kits and a mid power US Rockets Banshee. After our recent trip to LDRS 33 at which I purchased my daughter a Sirius Eradicator and I joked about getting my level one cert with it, my father gave me a stratologger for my birthday with the comment "Now you have to build something". I got a copy of RockSim and got started

True to my nature I immediately moved away from building a kit. Looking for a challenge I wondered if it's possible to build a single rocket that would span all three certification ranged (large I to a small M) but the additional requirements of a level 3 made this unrealistic. So I decided to build a bullet proof rocket that would fly on anything from an H to a full K or small L. What I have come up with will hopefully be my level one and level two rocket. The specs are as follows:

Length: 65.5"
Diameter: 2" transitioning to 3"
Airframe: PML pre-glassed phenolic
Nose: Fiberglass 5:1 Von Karman
Fins: 3/32" G10 Nose, 1/8" G10 tail
Motor retention: Aero Pack 3" to 54mm Tail Cone retainer & 38mm adapter
Avionics: Perfectflite StratoLogger + Missleworks RRC2, and an Eggfinder GPS each with their own 120mAh 7.4V lipo battery and Featherweight magnetic switch
Recovery: Fruity Chutes TARC 16" drogue, Fruity Chutes Iris 30" main with a Tender Decender
Lugs: 1010 rail
Weight: Estimated 4.5 pounds without motor depending on quantity of epoxy, paint, and recovery lines
CG: 33.1" from nose without motor calculated by Solidworks
CP: 49" Rocksim, 45.5" Barrowman
Planned Motors: Everything from an H242T to a K1050W

Here are some pictures of the solid models:


Front View


Back View


Section View (Shown with an I600R)


Nose Avionics


Avionics Bay Section


Open Avionics Bay

Your design looks sweet. CAD software right? I really need to get into that program. I'll watch your build.

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Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

Welcome (in a big way) to rocketry! Cannot comment in killer robots, which sounds cool, but I think you will find rocketry a fun and fulfilling hobby.

Welcome to the forum!

Sweet looking design

I'm not quite understanding this section of the design...



It looks like all the recovery is forward of the av-bay and control electronics, then you have a couple more bulkhead areas? Pistons? Or is that a camera bay aft of the nosecone?

Wow! This is awesome!

dixontj93060 said:

I'm not quite understanding this section of the design...

View attachment 181728

It looks like all the recovery is forward of the av-bay and control electronics, then you have a couple more bulkhead areas? Pistons? Or is that a camera bay aft of the nosecone?

Click to expand...

I will be covering that in another thread actually. I'll try to post about it tonight.

I have posted a description of my recovery setup in a new thread as promised here: Ejection Coupler Concept - Potential New Product.

I am making progress on this design and trying to finalize some things. I have decided to separate the development and prototyping of my ejection coupler concept from this rocket build. I'm now trying to decide between a more standard single end deployment with a tender decender or a typical two joint ejection on either side of the av-bay which will force me to add 2 more inches to the rocket.

Also I was originally planning to use PML pre-glassed phenolic tube but this has some issues with the thicker wall with my motor retainer and it is actually more expensive than Proline profusion tubing. This rocket is simulating to 1800 ft/s, for these speed which tubing is stronger? Which tube weighs more?

This project sounds great, welcome to the forum and back to the hobby. I'm looking forward to seeing how this turns out!

I think I've finally completed the design for this build. The specs are pretty much the same, gained 1/2" in length, removed the redundant battery and switch in the av bay, those components shouldn't fail, went to an ogive instead of the Von Karman. The biggest change, which I already mentioned is I decide not to use this as a test bed for my ejection coupler concept, I will test that on the ground in a separate setup. I am attaching full scale pdfs of the project including a section view. Shown with an Aerotech I600R.

View attachment Warp Test #1.PDF
View attachment isometric view.PDF
View attachment section view.PDF

Started ordering parts for this build. I have ordered the avionics components, nose cone, and motor retainer and adapter. I have a request in to PML for a scrap piece of pre-glassed tube to see if I can successfully machine the slots and holes on my milling machine, I'm concerned the spindle rpm is to slow for fiberglass. If not I will probably have them route the slots, or I may go overboard and make an indexing fixture for the 5ft x 10ft 4-axis CNC wood router I have access to...

So a lot has happened in the nearly four weeks since my last update. The design has evolved a little further, so much for being complete.

1) I added a little more length, the rocket can now accept a CTI 6GXL case, and I gained some length because my 5:1 Ogive is more like 5.6:1.
2) I made the rear fins slightly taller since open rocket didn't agree with Rocksim and RASAero that it would be stable at liftoff with a L265 installed.
3) The most major change though is the addition of a protrusion near the nose and another sled to accept a 808 #16 camera. The camera will be rotated 90 deg and pitched down at an angle that allows it to see horizontally and all the way to the body tube at the same time, should make for an awesome view.
4) I decided to go with filament wound fiberglass from Wildman instead of the PML glassed phenolic. The additional weight isn't bad and the added strength is worth it.
5) My 3 year old daughter has requested that I change the name to "Faster Buddy, Faster!" For anyone here with young daughters, this is a line from the movie Frozen, and something she says when she wants me to scratch her back faster. It's also an arguably appropriate name for a rocket the I plan of taking from a Level 1 cert on a CTI I236BS to eventually a CTI K1440 and beyond. I have added a poll to see what everyone thinks.

I have also purchased all of the component and received all but the fruity chutes, airframe, motor hardware, and Proline epoxy. The bulk of this will arrive tomorrow from Wildman and I will post pictures. I have also ordered my L1 and L2 motors, a CTI I236BS and a CTI J295C. I will post pictures of everything tomorrow.

I have also put together the artwork for laser cutting all of the plywood and fiberglass of this project, unfortunately the large CNC wood router I was planning to use isn't fully set up yet and waiting for it would mean risking not being ready for Midwest Power.

Lastly, I signed up for Tripoli.

I should be able to start slotting and drilling the tubes on Wednesday and I will be doing the laser work next Sunday. Early next week I will be able to start assembly.

Howdy there and welcome. My brother also builds and competes with combat robots. I really like your design and I'm working on learning how to use CAD software myself. I look forward to seeing how you build this and learning some things myself.

I said go with "Faster, Buddy, Faster!" The kids would dig it!


Later!

--Coop

Updates:

1) After the pole and some thought the name of the rocket has changed to "Faster Buddy, Faster!".

2) I have received all of the components for this build except the fruity chutes:




3) I began making parts! Luckily my ex-boss gives me free access to his production level equipment. I attempted to laser the bulk of the plywood and fiberglass pieces, but the edges charred to much on the ply and the laser wouldn't cut the thicker, yellower plywood. I have decided to make all of the rest of the pieces on the CNC router this weekend.
Masterwood 4-Axis 5ftx10ft CNC wood router. 18000 rpm 10HP spindle, 14 tool changer.
Epilogue Legend 36EXT laser. 36" x 24" 120 watt
Forms for laying camera hood on upper body tube cut on the cnc router.

4) I finished the fixtures for machining my tubes on the mill at work. This will allow me to get to 6 sides of the rocket for my 3 fin design, and I can add more pin holes to allow 8 sided machining for 4 fin designs. I'm planning on starting the tubes tomorrow.

Airframe tube in fixture rings
Fixture rings.

5) I finished the artwork file for the decal.

I plan to start gluing parts together Saturday if all goes well.

WOW! This looks like an awesome project, talk about getting into the hobby in a big way. I cant wait to see this finished and i cant wait to see some of your future projects.

Welcome

Started making tube parts today, one of the toughest parts of all this is not getting oil from the metal working machines on the tube. I washed my hands dozens of tubes and wiped down each piece of equipment with denatured alcohol before using it. Unfortunately I cut some pieces out of the wrong tube and ended up short for my last piece. Had to order another 2ft from Wildman.
Cutting Tubes on the horizontal band saw, this think cuts amazingly straight and accurate. All the lengths were scribed with a height gauge on a granite table.
Milling the tubes square and to length
Drilling holes
Todays finished parts. The longer tube is the mid tube between the motor section and av-bay. The coupler and one of the rings will make the av-bay. The remaining 2 rings have a lead on one end and are for the ejection bulk plates to sit against.

Tomorrow I plan to cut the fin slots in my motor tube possibly drill some couplers.

So it's been a week and a lot of progress has been made, though admittedly Midwest Power is coming up very quickly and this may not get paint and graphics before my first flights. I have learned a lot this week, particularly that even after a proper dry fit run through nothing goes as smoothly once the epoxy is mixed and the clock is ticking. I had two late stressful nights in part thanks to my lack of epoxy experience and part due to working in my kitchen away from my tools.

The first night I had multiple issues, the first because I panicked and couldn't get the threaded inserts into my motor tube bulkhead very well, also my parts are a tight fit dry, and the epoxy or something swelled the wood enough to make getting things lined up difficult, eventually it was ok. I also tried gluing in a u-bolt but after realizing I couldn't tighten the nuts by hand I ran down the stairs with the epoxied parts looking desperately for a wrench.

The second night I tried to JB Weld my retainer and nose cone tip in place. I was concerned about my mix ratio because I was doing it by eye and after 1+ hours of the JB weld not thickening up I again panicked, pulled the pieces apart and cleaned them off with denatured alcohol. In the morning I called my dad and explained to him about how I hate epoxy while he laughed at me on the other end.

I machined the rest of my parts except for my fin can tube, which I just started the fixture for today. The photo shows my nose tube set up in the mill


I also cnc cut all of my fins (plus spares) and my centering rings and bulkheads.


I glued the coupler into my nose cone, the photo shows the coupler screwed into the nose tube so it will be glues to the proper depth. The screw holes are very tight clearance.


The camera shroud form was test fitted to the nose tube.


I completely assembled the av-bay structure, I will start wiring this weekend. The av-bay has a rear cap and front ring that are glued in and a threaded spacers and long screws instead of threaded rods. This allows me to screw the sled cap in an not mess with fitting it over threaded rods an trying to get the nuts on nice.


There will be more in the next post but I have reached the attachment limit.

Lots more assembly, including the motor end coupler in it's tube, the motor retainer, tail centering rings.

First up, the JB-welded (the second time) motors retainer


Dry fitting my centering rings and fins. The fins are through mounted in both the outer tube and the motor tube, The centering rings are also slotted and act as a built in fin alignment jig.


Glued the nose cone tip in and the lead shot nose weight.


The centering ring are all glued nicely.


My dad helped me make a prototype camera shroud to fit over my 808 camera


I fully assembed the 54mm section of the rocket to get a better feel for everything

So about a week and a half since the last update and a lot has happened.

I completed the tail section. I epoxied the rail button thread inserts and fin can tube onto the lower section. We then wrapped the tube with a piece of mylar and cast a cylinder of high temp epoxy filled with phenolic and micro balloons, I then turned the tail section on a lathe to create a transition. I also sanded chamfers on to all 9 fins using an aluminum angle plate I made. Next we installed the tail fins with proline epoxy which due to the slotted centering rings went remarkably well.



...

I also completed the upper section. My dad made a camera shroud with 5 layers of 6 oz glass and we glassed it into the upper tube. I then build the centering ring / camera carrier for the upper section as well as the camera sled. I installed the centering ring assembly and the nose fins with a little bit of difficulty since it seems the 15 min epoxy I had really wanted to be 4 minute epoxy. Once those components where installed I was able to mount the camera parts to the sled and test fit it. I turned the camera 90 degrees and the wide angle catches the tube in the bottom 5% of the frame and a little above horizontal at the top. Should give an awesome view.



...

I assembled and tested the GPS sled and and fit it to the nose. There is a front plywood ring that supports the front of the board and it is epoxied to the nose cap.



I assembled the avionics bay components which before wiring fit nicely into the bay, now with wires I have to do a little work to make the installation easier.



Finally I drilled the shear pin holes, and test assembled what I could. Still need to do recover, and test my charges. After Midwest Power I will add fillets to all of my fins and then paint before launching this on the larger motors that will push it to it's limits for speed and altitude at Thunderstruck the K1440 and the L265.

So not everything went as planned at Midwest Power. Early on in the design I told my father I wanted to build my rocket to handle hard landings under a just a drogue or even, if possible, no deploymentat all. I was given the opportunity to test this. It seems the ejection charges were undersized or didn't burn fully. Four pops can be heard on the video and the stratologger records it's events as well as pressure pulses from the secondary charges. The rocket was recovered with only minor shovel damage, it will fly again after minimal repairs.

Max Altitude approx 1930ft, Min Altitude -4.5ft, approx 350 ft/s accent, 270 ft/s decent.


[video=youtube_share;RNFYuEVrQjU]https://youtu.be/RNFYuEVrQjU[/video]

My stratologger data plot is below. Is it normal for an altimeter to see pressure pulses from ejection charges? It's possible the the cap didn't seal perfectly on the drogue side, but on the main side the cap is epoxied in quite thoroughly and the only opening would be the shear pin holes, with pins in them.

Video of the flight, still trying to find the source of the wobble, even with the measured CG I should have 3+ calibers of stability.

[video=youtube_share;nI69kdfqb9E]https://youtu.be/nI69kdfqb9E[/video]

Ravenex said:

Video of the flight, still trying to find the source of the wobble, even with the measured CG I should have 3+ calibers of stability.

[video=youtube_share;nI69kdfqb9E]https://youtu.be/nI69kdfqb9E[/video]

Click to expand...

Possibly it was over stable. I have observed long rockets do what I call a "Tail Dance" due to stability in excess of two calibers. I try to keep the margin as close to 1 as I can for rockets operating at or below Mach. Just my observation.

Sailorbill said:

Possibly it was over stable. I have observed long rockets do what I call a "Tail Dance" due to stability in excess of two calibers. I try to keep the margin as close to 1 as I can for rockets operating at or below Mach. Just my observation.

Click to expand...

The rocket in the video was unstable at low velocity due to non-zero angle of attack crosswind instability.

While the zero angle of attack stability calculation in a simulation predicts you have several calibers of stability margin, once you push the launch button, the non-zero angle of attack stability of your rocket is the only one that counts. The effect of crosswinds on reducing the stability of a long thin rocket is not understood by many hobbyists. The late Bob Dahlquist and Dr. Robert Galejs of MIT Lincoln Labs and former CMASS member, each authored well-written articles on the correction of Barrowman stability margins to predict the actual in-flight stability margins. The 3 links below include the original articles and an Apogee Newsletter summary.

https://www.apogeerockets.com/Wind_Caused_Instability

https://www.argoshpr.ch/joomla1/articles/pdf/sentinel39-galejs.pdf

https://www.apogeerockets.com/downloads/Newsletter239.pdf

Bob

Regarding the deployment issues. I had something with one of my rockets which sounded similar to yours - the charge sounded like a "phut" instead of a "crack". That turned out to be caused by not sealing it well enough. Several more layers of tape made all the difference. The smaller upper tube may also not be helping you since the force applied to shear the pins is proportional to the area of the tube cross section. Were you able to ground test in full flight configuration?

Yea, looks like coning to me - https://www.rocketreviews.com/coning.html

As for the deployment, what size charges did you use and how where they packed? also, did you ground test them?

I was unfamiliar with this mode of instability, I would bet the rather small fins and the fact that the fins are near a transition could have caused this. My question then is how will this instability mode be effected by larger motors which would reduce my stability margin. It seem that since this condition is caused by the fins needing a high angle of attack to do the job that more speed of the rail may not help, is that correct? Some of the motors I planned to fly this on will get it off the rail faster, but my ultimate plan was to fly an L265 which won't actually get of the pad any quicker despite high top speed and altitude.

As to the ejection issue, the charge space in my rocket is approximately 2" dia x 1.2" long. This gives a piston area of 3.142 in^2 and a volume of 3.77 in^3. I used three 3/32" ABS rods for the shear pins which has a shear strength of 3000 psi or 62 pounds to shear all 3 pins. This equated to just under 20 psi needed to shear the pins. Using the equation found here https://www.info-central.org/?article=303 I calculated that I would need .038 grams of black powder, from the information found here https://www.alaska.net/~aleckson/rockets/smokless.html this would suggest I only need 0.013 grams of the smokeless powder we were using. I did ground testing with .025 grams and the shear pins sheared but the rocket separated weakly. We then increased the charge to 0.35 grams and the rocket separated about 4-5ft. For the actual flight the charge was increased to nearly .05 grams. Another thought that occurs to me, is that these spaces aren't vented and the main charges can be heard to go off very close to each other and even combined they didn't do anything, not even shear the pins, not sure how that happened.