7.5" Pershing 1A

My 4" scratchbuilt pershing 1A flew pretty well, and was a testbed for building a 7.5" version. I gave up after a year of trying to get a true pershing cone from PR, and finally settled for one of their 5:1 conicals from wildman. For $110 or so it was a very nice cone. I decided it would be better to have a large pershing with an incorrect nose cone than not have a pershing at all, and I wasn't motivated to build one from scratch. A 5:1 conical is the right length, just tapers too much for the first part. This build will be very simple, nothing fancy, just to show what you can do easily to get a nice looking rocket without having to do a bunch of scratch building. I'm using 7.5" upscaled vinyl from Mark at stickershock.

I'll attach my open rocket file showing dimensions and construction along with current weight estimates and flight simulations on 38/54mm motors. The current weight will be around 18 pounds to get the required CG. Currently the cone is around 5# and has 2.5# of balast and I'm estimating I will need around 10 oz more but am waiting for the booster parts to do final balancing.

With that much balast and as pointy a cone as it is, it wouldn't last long on landing, so I cut off the first 5", drilled it out to 3/8" and inserted a piece of 3/8" allthread with a nut and washer at the base after filling with lead. I then re-profiled the tip so that the landing force will be on the allthread. I then epoxied the allthread and tip back onto the nose cone and filled the remaining balast.

When the forward bulkhead is installed it will tighten onto the allthread and the allthread and washer/nut will take the brunt of the recovery strain instead of the bulkhead/cone joint.

I'm intending on using a zipperless construction where the two separate chutes for booster and cone section are in the forward section and the bottom has the coupler installed.

Here are a few photos of the cone construction so far.



Frank

Here I did the base of the cone od, and shown are some basswood detail strips and the open rocket file.





Pershing 1A open rocket file:View attachment pershing1a_big (1).ork

While I'm waiting for the booster parts and paint to dry on the cone, I thought I'd post a few pershing pictures that I haven't seen much on the web. One is a pershing 1A with what appears to be a pershing 2 cone section, another has a different pershing 1A scheme, and then a couple of a shorter version of the pershing 2 than we normally see in pictures or kitted with some strapping detail that I thought was interesting.



Frank

And a few more showing multiple short pershing 2's and a normal pershing 2 as you typically see, the second to last shows a 1A test that has a parabolic cone in place, and the final one another longer 1A and test scheme. Maybe these will get some folks to build some different pershing versions based on these....The parabolic version looks a lot like a trident I think and should be pretty easy to make if one were inclined.



Frank

This is going to be a large rocket. I shall enjoy following this!!

Very cool--thanks for posting. I've got a Rocksim I've worked on a bit on a big Pershing II, but have yet to start--as my ideas are a bit more ambitious than my abilities at this point. The NC question is one that's puzzled me...


Later!

--Coop

Here's the cone with the lower stripes and 31's....I'll hit it with some flat overcoat to get rid of the shine. It's next to my 4" version, the nose was "shortened" on the 4" when the chute didn't fully open and the hard farm sod took it's toll.



Frank

A few more interesting photos....

View attachment 113266

beautiful work!! they look fantastic!

burkefj said:

Here's the cone with the lower stripes and 31's....I'll hit it with some flat overcoat to get rid of the shine. It's next to my 4" version, the nose was "shortened" on the 4" when the chute didn't fully open and the hard farm sod took it's toll.

View attachment 113132

Frank

Click to expand...

Awesome nose cone. Can't wait to see more.

This is a great project. Totally subscribed.

Something looks awfully familiar on that nose LOL LOOKING GOOD!

with alk the pis you posted I should work up some more Pershing versions.

A great build, if I must say so myself ,and you know how I feel about Pershings !

I think the 7.5" conical nosecone is a splendid idea ,it definately works !

Keep up the nice work !

Paul t

Thanks for the encouragement and yes those decals should look familiar. For a straight conical I could have narrowed the stripes a bit to get equal spacing of white and black but I was too lazy. Also the horizontal stripe location was moved down too due to the different curve but not a big deal to me.

I think you are right, you could do many different schemes.

Finished my eBay but no matches to try it out..it will go up against the cone bulkhead and screw to the side..

Frank

I wish I could make those stripes fit EVERY possibility but there are just way to many things to consider!

Cant wait to see it in the air!

I got in the tubes from wildman and the fiberglass. Left the bottom tube 30" and cut the top to 11". I used my sabre saw to cut the fins out, 1/8" for the bottom and 3/32" for the top to save a bit of weight. I used my belt sander to clean them up and put an angle on the leading edges. I then cut some tube sections to act as the pivot plates to go over the fins, it's a bit easier than building a full pivot plate and will look the part. It's what I did on my 4" version.

I think I'm going to alter my zipperless construction to normal cone and body recovery since the cone shoulder fits the tube so well, and I'm going to make the top 11" and coupler held in by screws so if it gets a tear I can replace it easily. It will also work better with my altimeter bay. The top fins are slightly lower than scale which saved me another 8 ounces in nose weight...

Everything dry fit together. AUW so far empty is about 13 pounds and it's about a pound short of nose weight for a K-550. Altitude sims are from 1800 to 3000 feet on J-540's to K-550's..

I've got my two 60" chutes and nomex blankets and kevlar recovery straps ready to go. Altimiter bay is built and waiting for my missile works altimeter to get back(had a dead output transistor on primary)



Frank

Big, Bad and Beautiful. That Pershing 1A still has the coolest rocket paint scheme of all time.

Finally got back to this now that the competetive shooting season is almost over.....Everything is installed and reinforced on the inside, and av bay installed, just need to fillet the ouside of the fins and fill and sand/paint/decal and then double check the CG.

Frank

Cool upscale, looking forward to more.... and also to say huh, I've shot at your range before.... USPSA Area 1 in 2008.
Nice area, I checked out Tilamook air museum, and Evergreen too. A good friend worked on the blackbird at McMinnville.
Thread hijack over, looking forward to your build.
TimE

Frank ,

Glad to see this great build thread going again......I`m a happy man !!



Paul T

Finished the fillets. Just prep and paint work and final CG now.

Picture isn't great, but I've gotta get to work...The screws are holding the coupler to the bottom and the upper tube to the cone. I've had problems with PR cones fitting tubes well, so prefer a tube to coupler fit. If anything ever zippers or is damaged I can just remove the screws and replace the coupler or upper tube easily, they don't take anything but a vertical launch stress so don't need to be glued. The chutes will fit into the upper section behind the nose cone and the av bay is in the lower portion parallel to the motor tube. CG is a pain on rockets with no fins.

Frank


Frank

Here she is, all assembled, next to my 4" version I scratch built. I did a quick check of CG and it looks like I'll have to go with a J-570W as that will only require 5 more ounces of ballast, and approx 1500 feet. With a J-510 about 1800 feet.
Stickershock provided the nice markings. The color of the strips are more orange than my 4" version for some reason.

Frank

For the first time I did a ground ejection test. I wanted to make sure I could presurize the volume, not get blow around into the altimiter port, and not move the removable forward bulkhead(I want to be able to remove it to add weight later if I want). I did not say hold my beer and watch this, but I did find out what 2x the amount of black powder needed feels like.....I held onto the 10 pound cone, and had my kids hold a blanket behind the booster to catch it. It shoved the cone right out of my hands, and I was holding tight, the kids softly caught the booster and nothing was damaged. The inertia was enough to pull out the spare plug/wire for the ejection charge connection I wasn't using.....I added 16 oz of nose weight, and now it has 1.16 body diameter margin with a J-825, J-575, or J570, or J460 and 1.02 with a J-540, altitudes from 1100-1800'. I'd need to add another 9 or 10 ounces to use k-1100 for 3K feet. I probably need about 2 grams or 30 grains, was probably using about 60 grains, was thinking muzzleloading with 3F and not 4F...

Frank

Now that is a thing of absolute beauty......BRAVO !


Paul T

I had two very successful flights this weekend in Brothers, Oregon, and a big thanks to the John Lyngdal, Gary Goncher, Tim, the other Tim, and Robert for helping out, and loaning various components to get things going, and to all the OROC folks for putting on a great launch, and providing a great dinner, and to my wife, Sophie for helping out in the cold.

First flight was on a J-570 and was perfect, just a slight 5 degree angle caused by wind about 100 feet up, missileworks micro altimiter worked perfectly, 1300', no damage. Second flight was on a J-510, slightly more tail heavy, video will show a slight wiggle then it straightens out, again, perfect altimiter deployment with motor backup, 1700' and zero damage on landing. Very rewarding project and looked very good flying.

Video at: https://www.youtube.com/watch?v=9Hga7aVXZgg&list=UUmToWCQ4okdIYb848HJn_sQ

I didn't get the deployment, I was too busy trying to watch the ejection and track the nose and body.


I also got in two flights of my 4" Pershing 1A on G-75 metalstorms, a nice flight on my Performance hobbies 4" Nike Smoke with an I-285 Redline, and a flight on my scratch pershing 2 1/2 on an H-128, only mishap of the weekend was on the H-128 flight, I had drag separation right at apogee and it tumbled with only about 4' of the kevlar pulled out and the cone and body tumbling, and then the motor ejection fired and it landed nicely.

Frank

WOW!!! that looks fantastic! beautiful job!!

burkefj said:

Here she is, all assembled, next to my 4" version I scratch built. I did a quick check of CG and it looks like I'll have to go with a J-570W as that will only require 5 more ounces of ballast, and approx 1750 feet. With a K-1100 I'd need to add about 22 ounces. It's 16.2 pounds dry with adapter and chutes installed.
Stickershock provided the nice markings. The color of the strips are more orange than my 4" version for some reason.

Frank

Click to expand...

Frank, Nice looking model! You've got the touch both for ballistic models and profile R/C models.

Here's the first flight photo thanks to John Lyngdal! This is the J-570 flight

Those were some pretty impressive flights. You know, there were actually some really great flights flown this past weekend in spite of the lousy weather. We are Oregonians, aren't we?