Nike Hercules Two-Stage by rharshberger

[rharshberger]

This probably should be in the Scale section since its pretty much a sport scale Nike Herc.

May 14, 2017

As some of you know I have been talking about doing a version of the Nike Hercules which is one of my favorite missles of all. Thanks to a very generous member of the rocketry community I was able to get my hands on a set of very detailed drawings of the Nike Herc. The model I am planning/building is to be somewhere between sport scale and scale. The finished model will stand between 43" and 45" tall when stacked in flight configuration, the sustainers major diameter is to be the 3.00" T300 airframe tubing from Balsa Machining Service. Fins will be a composite of thin plywood cores with balsa skins to shape. Overall I am trying to keep this rocket fairly light. The sustainer will have single 29mm motor and the Av-Bays for Altimeters and Timers. The booster will be powered by four (Yes you read correctly 4x 29mm motors), it will also contain a Av-Bay for an altimeter and recovery. Obviously on a build such as this there will be some slight deviations from the original, the main one for this build will be in the inter-stage couple area.

So here are the first pictures of the building process, the nose cone is a 3.00" version of the PNC-80K from Balsa Machining Service, first step was to modify the nose cone to get the proper length and eventually profile. To do that I am cutting the tip off at the point that a piece of BT-60 can be used as an inner tube and a BNC-60V2 nosecone can be used, after matching/blending the ogive of the 3.00" NC on the smaller nose cone the shape and length will be almost perfectly to scale (this step will take some serious work).

 

[rharshberger]

May 14, 2017

And a couple of more pics of the roughed in nose cone and a scrap of BT-60 inserted. The BMS nose cones are the same ones sold by Mercury Engineering and Apogee, they are not the same as the Estes 3" used on the Big Daddy, Leviathan and Scion, the BMS cone has a slightly longer ratio and is about a inch or two longer. One nice thing about the BMS cone is it seems to have very uniform walls, all measurements were right about .05" thick, the plastic was easy to mark with a mechanical pencil and to score with a Xacto knife. After making 3 or 4 passes with the Xacto knife the groove was deep enough that my Zona razor saw easily followed the scribe marks and finished the cuts. I also cut off the base of the NC shoulder as part of the NC will serve as a Av-bay, and part most likely for more nose weight than I want to put in it.

 

[rharshberger]

May 24, 2017

Kinda got stalled on this one for a bit, changed the nose cone plan. Now I am going to turn a solid basswood cone for it on my wood lathe, its a pretty simple process since OpenRocket was able to print me a perfect matching pattern to base the cone from.

 

[rharshberger]

Back at it today and honestly this part in one of the two most dreaded parts on a Nike Hercules for me, for most people its the inter-stage adapter, for me because it was necessary to turn the nose cone to a specific profile it was the Nose Cone. The nose cones current weight is 17.4 ozs/ 493.4 grams, its 17.5" long including the 3" long shoulder. Pictures will be in reverse order from finished to start.

 

[rharshberger]

May 29,2017

More pictures...

 

[rharshberger]

May 29, 2017

and some more pictures...



For those not aware the squiggly lines are to let me know when the flats have been totally turned away.

 

[rharshberger]

May 31, 2017

Worked on the sustainer guts, which is to say mostly the section dealing with the sustainers inter-stage coupler and the timer electronics bay, everything is extremely tight. I also started hollowing out the nose cone removing about 60 grams of basswood but still more to go as the nose cone will be needed for an av-bay.

First up was laminating a couple of centering rings, the stepped one in the left photo (bottom) is the top of the interstage coupler, the middle is the same one clamped for gluing, and the right photo is the CR for where the transistion meets the main sustainer airframe. It was necessary to cut most of the CR's as they are oddball sizeds, like inside a BT-70 coupler to 29mm heavy motor mount tubing, and the step for the transition to inter-stage coupler (brown coupler in later pictures) so there is a slight shoulder to act as a thrust bearing surface. The upper transition CR is laminated from a stock BT300 (think Leviathan airframe) to BT52H tubing thats .125" ply and a .25" balsa version I cut and beveled the edges to make for a solid joint between transition shroud and the upper airframe.

 

[rharshberger]

May 31, 2017

On to the inter-stage coupler and transtion thrust structure.

The left photo is the coupler with the upper CR installed and the coupler doubler installed, its pretty stiff which is what I was wanting.

The middle photo is the ISC with the lower CR and airstart wiring raceway installed (but the tubing is not yet epoxied permanently).

Right photo is the transition structure with the stringers for stiffening the motor tube, this was an area of concern due to the small diameter of the motor tube vs the weight of the upper sustainer section. My concern was that under full thrust (if I dare say MaxQ) that the motor tube would buckle, shouldn't happen now. Also in the picture is the transition's shroud rolled from a piece of poster board, and rounded off on the nose cone, and the Missleworks PET2+ timer intended to do airstart and if necessary seperation charge firing duties.

 

[rharshberger]

May 31, 2017

Left photo is the complete transition and ISC with the t-nuts for mounting the timer, batteries will have to go on the other side of the coupler. This is turning out to be my most complicated build yet mainly because things have to be kept as light as possible yet strong, and everything is compact. The holes in the stringers will help with routing the battery wiring after I add some tubing to ease passing wires from one side of the bay to the other.

Right photo is the complete sustainer mocked up minus fins, the main airframe only has about a 3" diameter x 4" length of open space for the parachute to go. I can however if necessary cut some of the nose cones shoulder off to gain additional space. The transition shroud is not the poster board one mentioned earlier, it was a trial one made from plain printer paper.

 

[rharshberger]

June 2, 2017

Today was working on the Booster section. Mostly it involved about 2 hours cutting CR's and Bulkheads, most parts x4.

The left and center pics are two different angles of the same parts. The booster is constructed of 4 outer tubes with the motor mounts and then sections are cut away to allow the central payload tube to be inserted (actually it will be done as I go, and it will be documented). The motor tubes are BT-52HF (foil lined BT-52 heavy wall) from Balsa Machining Service, the outer tubes are T-204 (2.024 OD, simulating the M5E1 Nike motors) each 17" long (which is not scale in either dimension, at best this model wil be sport scale) the longer than scale booster motor tubes was required to make sure I could fit anything up to a CTI 4G or a AT 29/240 just in case it needs the extra oomph and the extra .4" diameter per tube was to ensure enough parachute bay room for the av-bay and the parachute.

The right photo is the assembled parts, on the left is the bulkhead that fits just above the motors forward closure and on top of which the parachute bay will sit (it would be easy enough to do away with the electronics in this section all together by porting the bulkhead into the bottom of the parachute bay, and I probably will do it as a back up motor ejection).

The center section of the right photo is the top bulkheads for the M5E1 motor tubes, after they are indexed and installed the top 8" of each T204 will have about 1/3 the diameter (to match a 3" diameter airframe nested in the middle) of each tube removed, and the bulkheads will sit flush with the top of the parachute bay. The motor mounts are shown on the right side of the picture, they are offset to index as close to the center of the cluster of M5E1 tubes as possible to try and mitigate a failure to ignite of one motor if possible. Currently I hope be able to boost on a cluster of 4x G53J (or similar CTI Skids) or even depending on weight of the finished rocket something with lower thrusts nearer to 5:1 Thrust to Weight ratio (depending on wind of course and other factors).

Overall I am aiming for a finished weight in the 6lb range....

 

[rharshberger]

June 3, 2017

M5E1 motor assemblies somewhat ready for assembly. Pictured below are the major components of the booster section, the interstage section is an animal all its own.

Left Photo: M5E1 assemblies almost ready to be joined in the 4 tube arrangement, as soon as the glue dries from the bulkheads and the 2/3 moon bulkheads I will finish cutting away the coupler on top to allow the tubes to nest around the recovery bay. Lots of lines on the tubes to assist will alignment so far its looking good for all three motors to be parallel

Center Left and Center Right Photos: Recovery bay from the top and the side, the bottom bulkhead is doubled since the lite ply (not my usual Baltic Birch) felt kind of flimsy, now its solid. The short kevlar recovery harness mounts are installed as well (on both sustainer and booster sections).

Right photo is various parts.

 

[rharshberger]

June 3, 2017

Made a lot more progress on the Booster section than I envisioned today.

Left Photo: Booster tube separators positioned on the first tube.

Center Photo: added filler strips to fill gap between booster tubes, the actual missle did not have fillers and you could see daylight between the booster motor casings. The reason for the filler strips is to add just a bit more stiffness to the tubes, which are plenty strong already and to match the upper and lower sections of the booster tubes. With the central parachute bay installed the upper 8" will need filler strips anyways so the who booster gets them.

Right Photo: Is actually a trial fit before filler strips were added, but this picture will also serve as the documentation of the first booster tube and parachute bay being mated together.

 

[rharshberger]

June 3, 2017

And continuing with the Booster assembly.

Left Photo: opposite end of previous posts photo

Center Photo: both booster tubes are actually installed. The filler strips on the parachute bay serve two purposes, first the strips act to keep the booster tubes from wanting to spread on the cut out sections, two they assist with make sure everything lines up correctly.

Right Photo: 3 of the 4 booster tubes installed, the coupler serves the function of making sure the parachute bay remains round during assembly.

 

[rharshberger]

June 3, 2017

And a few more...

Left Photo: another view of the three installed booster tubes.

Center Photo: all 4 booster tubes installed, somehow I managed to get a tiny bit of twist in the whole stack, but not enough to worry about since its less than 1/32" (when laid flat on desk the booster assembly actually will rock back and forth just every so slightly).

Right Photo: a view from the business end, eventually the motor tubes will get Estes 29mm retainers most likely after painting. Everything lined up rather well. The X's on the wood parts are for indexing purposes, each of the rings are handmade and when I cut the motor tube hole its enough imperfect that simply flipping a ring over would induce a cant to the motor tube, so each pair has an X on it to tell me which sides are "UP", same for the center star piece (it also serves on that piece to make sure they are all indexed to the same clock position).

So far I have maybe 20 hours in build time on this project. And I have no doubts about its ability to handle the planned flight profile as it stands. Currently the booster weights 10.85 ozs (307.6 grams), I usually take measurements on my scale in grams even though I prefer Imperial measurements for most everything.

 

[rharshberger]

June 4, 2017

Today's little project is the top of the booster details which is basically the flared section at the top of each M5E1 booster tube. It turned out to be easier than I have originally envisioned it once I figured out how to keep the very thin balsa from breaking as I put it around a curved surface WITHOUT wetting the balsa.

First up is the shaping part, basically its just an angled section and a narrow flat band above the angle. So using 1/16" balsa, I made the jig using my long Easy Touch sander (HobbyTown USA for like $12), two mini-clamps (Home Depot $ 0.37 ea), and my short Easy Touch sander, the bevel was very easy to make. Then on to the rest of the process.

 

[rharshberger]

June 4, 2017

Next up..

Next up was separating the beveled section from the sheet, and my old balsa stripper came in handy for this, a ruler was used to back up the edge of the balsa where the blade exits to prevent splitting the balsa near the end of the cut. The Scotch cellophane tape turned out to be my secret weapon for the rest of the project, since it sticks to the balsa and plywood but not too strongly.

 

[rharshberger]

June 4, 2017

And the results of this section...


Left Photo: Scotch tape applied to face of beveled part, Titebond II on back of part (very thinly spread). Without the Scotch tape the balsa strips would break as they were applied to the tube.

Center photo: Starting at one end of the detail strip, I carefully pressed it into place and using my other hand pressed the strip down all the way around the tube being careful to maintain tension on the tape. Once the strip was pressed down and using one hand to press each end down, I adjusted the strip up or down as needed with the other hand, then folded over the tape on the top which acted as a very light duty clamp, I continued holding the ends until the glue set enough to hold itself.

Right photo: finished result after tape was removed from a couple of the early trials.

 

[rharshberger]

June 5, 2017

Onto the 4 into 1 transition, the part I have dreaded the most, and now it seems needlessly. The 4 into 1 is actually pretty easy, its nothing more than a conical transition with X minor diamter x Y length x Z major diameter, the tricky part is the lobed shape lower section. The trick was to find out what the larger diameter section of the transition would be if it were round, enter a strip of paper and some tape. Tape one end of the strip to somewhere on the lobed base plate and then carefully wrap it all the way around the funky shaped piece using tape as needed to hold it in snug. Then after it meets the starting end, trim and remove from base plate, measure and ta da! you now have the major diameter of the lower section of the cone (in this case it was 15.78" circumference around the base plate, making a truncated cone with a length of 3.42" x minor diameter of 3.94" x major diameter of 5.02").

Left: view of bottom of ISC and Av-Bay for booster, if need be I can shorten the coupler down to a mere inch and still have space for the electronics.

Center: view of top of ISC lobed plate.

Right: stage coupler for sustainer installed on top of plate. (Edit: notice that ISC coupler is doubled via outer sleeving of piece of BMS T70H for additional strength).

 

[rharshberger]

June 5, 2017

Additional work on ISC....

Left: stiffeners cut and ready to install, upper shroud CR is installed as well.

Center: Stiffeners installed, wished I had two more of those little Dewalt clamps.

Right: For some reason I forgot to take pictures of the shrouds laid out after cutting, the ones shown in this picture are actually plain paper ones cut to test whether or not they will fit correctly. The final shrouds will be cut from .015" poster board then treated with CA. OpenRocket was used to generate the paper shroud templates.

 

[rharshberger]

June 5, 2017

More work on the ISC....

Evidently there is an Angry Bear in the server and its making uploading photos a P.I.T.A! (from original post on my clubs forum page)


Left: completed structure of the ISC, there are four .25" vent holes in the sustainer coupler to prevent a vacuum from forming and not allowing the sustainer to drag separate (yes this is one of those times when drag separation is a good thing). Still some final fitting to do for the sustainer to easily slip out of the coupler, but its pretty easy to pull them appart now.

Center: Lower and larger shroud glued on the top only.

Right: Both shrouds installed and CA treated to harden, the lower shrouds major diameter was glued with CA, and whadda ya' know, it makes the shape of the Nike Hercules 4 into 1 almost entirely by itself! Still need to cut the two trapezoidal holes on each side and add the crease details on the other two (or I may just forget about the crease details).

 

[rharshberger]

June 5, 2017

An now the pre-finished stack with my lovely (and wild assistant, aka my 2 year old daughter Luci)...

The finished rocket will stand almost right at 50.5" tall, and as configured in the picture weights 36 ozs (1029.4 grams). The nose cone will be losing some additional wood as soon a I can order a carving gouge to open up the hole for the nose altimeter bay.

Next steps are fins and the little fiddly bits related to electronics and av-bays (x3), the sustainer transition will also be receiving a layer of fiberglass so I can make some removeable hatches for the timer and battery bays).

 

[rharshberger]

June 6, 2017

Started the booster fins today, didn't take but a couple of hours to get as far as I did before realizing I had no 1/8" balsa (enough of 3/32, 3/16, 1/4").


Left: 1/8" Baltic Birch Cores cut, and starting to add basswood diamonds on ends. Due to the fin tab the larger diamonds are mortised onto the fin.

Center: Core with both diamond profiles fitted and lightening holes added.

Right: All four fins skeletons done, the diamonds are made of basswood since its harder than balsa which the fins will be built up with. The fins are to be solid, not sheeted so lots of sanding to profile, the basswood will be protected with a couple of layers of masking tape and then the balsa will be sanded to match the profiles of the the diamonds, any sanding on the tape will not change the profile of the diamond.

 

[rharshberger]

June 6, 2017

Booster fins some more...


Left: the stack of fins with 1/4" balsa overlay on the cores.

Center: Fins with 1/16" balsa on top of 1/4" balsa, it was necessary as the mid-line diamond tips are about 1/32" proud of the 1/4" balsa and creates a wider flat spot than I want once profiled. The fin in the center of the picture nearer the bottom has been partially profiled then the thinner balsa was added. Tomorrow bodes lots of sanding. The leading and trailing edges will be built up the same only with all balsa. Fins should be both strong and light weight, self-adhesive label paper will be used over the balsa and sealed with CA, at that point the fins can be installed on the booster and that will be one section almost completed.

Right: One side of fin profiled, showing how much of the 1/16" balsa is removed.

 

[rharshberger]

June 7, 2017

Booster fins finished...

Left: Leading and Trailing edge buildups done, now the hard work starts.

Center: Profiling completed, and slight imperfections/gaps filled with CA. Profile sanding was accomplished using a 8" disc sander and narrow belt sander for major material removal, final removal was done by hand using a Great Planes Easy-Touch sanding bar 12" length. The fins are almost too pretty to paper but that means more work filling balsa, yuck!.

Right: Fins papered and ready to install on rocket. Each fin averages 35.15 grams (1.24 oz each, and all four together weigh 4.96 ozs) pretty lightweight, yet strong to me.

 

[rharshberger]

June 8, 2017

Evidently I missed a step somewhere along the line and the Rocket Elves stuck fins on the Booster...

Left: rail side of booster, thank goodness this side will not be photographed very often, as the upper rail-button mount looks out of place, the bottom one kind of blends into to the boosters lower wrap. Rail-buttons are 1010 size.

Center: different view of booster. Honestly the fins turned out great IMO, and very strong and no flex. Big hole visible inside cutout on 4 into 1 transition is one of four anti-vacuum holes for sustainer drag separation, I may end up plugging the holes and using a separation charge, depends on how the test flights go.

Right: yet another view, the shear pin hole is visible just above the static port (just below transition and between the booster motor tubes, in valley on right side).

Current weight of booster w/o, chute, Eggtimer Quark, battery, and harness 22.5 ozs.

 

[rharshberger]

June 8, 2017

4 down 12 to go, Sustainer fins that is..

Left and Center: Forward Canards laminated from 1/32" plywood and 1/16" balsa.

Right: Fins partially profiled, due to the size of the fins this may be all the more profiling they get, other than some smoothing.



Edit: I don't like the profiling I did on these fins but they will work, this isnt a true scale project and at the time I was recovering from surgery so they will be used as is.

 

[rharshberger]

June 9, 2017

This was a response to a comment by FlyFalcons a TRF member who is also a member of my local club.

Thanks Ryan. The build is actually pretty enjoyable, and the technical challenges of getting all the electronics into their respective locations and wired is presenting some interesting challenges.

 

[rharshberger]

June 9, 2017

Main sustainer fin skeletons...

Left: Skeletons cut and ready for prepping for shaping. The fins on this scale Nike Herc taper from 1/8" to 1/2" at rear of airframe, then back to 1/8" at rear of fin, the chord edge of fin is a 1/8" from just behind canards to the rear of main fins. 93 grams weight for all four cores.

Center: Basswood stringers applied to bottom edge to assist with tapering the fins, the core will act as the harder material to keep balsa removal under control. There is a diagonal stringer not shown in these pictures that runs from the tip to the edge of the airframe on the root edge (in the left photo a diagonal line is in the same location.

Right: balsa skins laminated to cores and ready for sanding down tomorrow (hopefully). The triangular section at the rear of each fin will receive a posterboard/Cardstock skin treated with CA.

This rocket will not be ready by June Swoosh, however I may bring it as a conversation piece.

After the fins I so wish I had a laser cutter.

 

[rharshberger]

June 10, 2017

No further work today, and probably not much for the next week until June Swoosh is over.

 

[rharshberger]

June 24, 2017

Back in the saddle again....

Work on the sustainer fins went much faster after the acquisition of a new tool. The Master Airscrew Razor Plane makes balsa removal a snap, its not much good for basswood but thats ok. The razor plane I picked up at Kennewick HobbyTown USA (it was the last one, but they do usually have them in stock).

Left: All twelve fins are profiled

Center: another view of the main sustainer fins after profiles have been planed and finish sanded.

Right: Main sustainer fins with cardstock skins on rear of fins (1 each side). Also in the photo are the tools used to do the majority of the profiling, the blue tool is the razor plane. The razor plane while made of plastic worked very well after giving it the standard woodworkers tune-up of flattening the sole.

Next step will be fiberglassing the transition that covers the timer av-bay and making the access covers for the timer bay.