fyrfytr310's Level 3 - Polecat 10" Nike Smoke

[fyrfytr310]

I have flown this motor without grain bonding and had no issues. However, if AT is recommending this, then you should plan on doing it. When you get to the point of grain-bonding, let's talk. I do this on all my EX motors and we can set up in my shop to do it before the launch.

Sounds good.

 

[fyrfytr310]

I have a machinist friend who was kind enough to produce some charge wells for me. (pondman design)

 

[dixontj93060]

Oh those are nice lookin'!

 

[OverTheTop]

Coming along nicely!

I have just started using an o-ring groove around the top of the charge wells. Sometimes sticky stuff isn't, and it worries me that it might come loose and scatter before it is triggered.

I put in the BP and eMatch, then tamp in some wadding, then tape over with Kapton tape. In this latest idea I will do all that and finally stretch an o-ring over the tape and it will hold the tape into the groove.

 

[fyrfytr310]

Coming along nicely!

I have just started using an o-ring groove around the top of the charge wells. Sometimes sticky stuff isn't, and it worries me that it might come loose and scatter before it is triggered.

I put in the BP and eMatch, then tamp in some wadding, then tape over with Kapton tape. In this latest idea I will do all that and finally stretch an o-ring over the tape and it will hold the tape into the groove.

View attachment 304129

View attachment 304130

That's pretty slick. I like it.

 

[fyrfytr310]

Both Schurter switches replaced.

Access holes drilled so I can reach my screw switches.



Started my finishing process with a combination of sanding and bondo in the particularly bad places.

 

[dixontj93060]

I'll take those horrible Schurter switches!

 

[fyrfytr310]

I'll take those horrible Schurter switches!

Send me a PM with an address.

 

[fyrfytr310]

Charge wells installed.



I also did a little more surface prep and up sized the nose shear pins to 4-40 from 2-56.

 

[CORZERO]

The size of those bulkheads make those charge wells look like thimbles!

 

[fyrfytr310]

Well crap. Calculated loads for the main don't fit... Ground testing tomorrow will prove how conservative the equations are. Already contemplating alternative wells.

 

[fyrfytr310]

Didn't get to ground test charges today thanks to some unexpected familial challenges. I did however get to install the antizipper equipment on one harness, complete the recovery system between the upper and lower airframes and test fit everything. I also made the kerfs for the rail button standoffs. Finally, I purchased a möbius camera from Amazon and a shroud from AdditiveAerospace.

 

[NateLowrie]

Coming along nicely!

I have just started using an o-ring groove around the top of the charge wells. Sometimes sticky stuff isn't, and it worries me that it might come loose and scatter before it is triggered.

I put in the BP and eMatch, then tamp in some wadding, then tape over with Kapton tape. In this latest idea I will do all that and finally stretch an o-ring over the tape and it will hold the tape into the groove.

View attachment 304129

View attachment 304130

Very nice.

 

[ksaves2]

Well crap. Calculated loads for the main don't fit... Ground testing tomorrow will prove how conservative the equations are. Already contemplating alternative wells.

How much powder do you plan to use and how much will your charge wells hold? Kurt

 

[fyrfytr310]

How much powder do you plan to use and how much will your charge wells hold? Kurt

Calculations call for ~10g. Charge wells are maxed at 6g.

 

[OverTheTop]

My Nike Smoke 8.25" has wells that both hold up to 10g. Primary is 7g and secondary is 10g. Your chute bay length will likely be different to mine though.


Here is a pic of mine. These ones I made to take the threaded tops from soda bottles. For scale, the bulkhead is about 4.5" diameter.

 

[ksaves2]

Calculations call for ~10g. Charge wells are maxed at 6g.

Better get bigger wells then. That's quite a disparity. You could test with 6 but if it's wimpy at getting the laundry out you best move on and save the wells you had made for a smaller project. Kurt

 

[fyrfytr310]

Better get bigger wells then. That's quite a disparity. You could test with 6 but if it's wimpy at getting the laundry out you best move on and save the wells you had made for a smaller project. Kurt

That's my plan. If 6g doesn't discharge the laundry with authority, I'm moving up.

 

[ksaves2]

My Nike Smoke 8.25" has wells that both hold up to 10g. Primary is 7g and secondary is 10g. Your chute bay length will likely be different to mine though.

View attachment 304304
Here is a pic of mine. These ones I made to take the threaded tops from soda bottles. For scale, the bulkhead is about 4.5" diameter.

Holee Cow, You leave those twist tops on to constrain the powder and have it "blow through"? If so do you find you can use less powder than if you just taped in dog barf over the end?
Kurt

 

[OverTheTop]

Holee Cow, You leave those twist tops on to constrain the powder and have it "blow through"? If so do you find you can use less powder than if you just taped in dog barf over the end?

The tops of the caps are scored in a cross pattern to provide weak points for the gases to escape (the ematch goes in through a small hole in it also). The caps essentially peel open from the middle, with the thread staying put on the canister. Quantity calculations are as per normal. I never use dog barf. Mostly nomex blankets, but now tending towards deployment bags.

 

[RocketFeller]

I would test with your existing wells before you get bigger ones. In our upscale Dragonfly we use four grams with five for the backup.

It is a 12.625" x 36" compartment with six 4-40 shear pins.

 

[fyrfytr310]

I would test with your existing wells before you get bigger ones. In our upscale Dragonfly we use four grams with five for the backup.

It is a 12.625" x 36" compartment with six 4-40 shear pins.

My compartment has less empty volume, is using (4) 4-40 pins an and will contain both an 18' and a 9' rocketman chutes. Hopefully that all bodes well. I am hoping to test today.

 

[RocketFeller]

My compartment has less empty volume, is using (4) 4-40 pins an and will contain both an 18' and a 9' rocketman chutes. Hopefully that all bodes well. I am hoping to test today.

Ours has a single 16' Rocketman, a 36" square of thick Nomex, and a 39" square of thinner Nomex. For ground testing we approximated the harness/parachute with a piece of rope and an old pillowcase with a king size sheet inside.

 

[NateLowrie]

The tops of the caps are scored in a cross pattern to provide weak points for the gases to escape (the ematch goes in through a small hole in it also). The caps essentially peel open from the middle, with the thread staying put on the canister. Quantity calculations are as per normal. I never use dog barf. Mostly nomex blankets, but now tending towards deployment bags.

That is a really good idea I am going to have to try soon. Do you take the flexible gasket out of the cap or leave it in? Do you score on the bottom or the top? What's the burst pressure?

 

[OverTheTop]

That is a really good idea I am going to have to try soon. Do you take the flexible gasket out of the cap or leave it in? Do you score on the bottom or the top? What's the burst pressure?

I leave the gasket in place, just to keep the BP out of the threads, if it gets past the wadding. I score the top of the cap in a large cross, using a Dremel with a round burr, fairly deeply but not through. Have not tested burst pressure.

No downside to the system was noted on its only flight so far (L3 cert flight with N1100). There wasn't a lot of space left in the bay after packing. All chutes and harnesses came away from the flight with no damage.

 

[fyrfytr310]

Rail buttons and kerfs installed.









Ignore my hill-billy motor tube ground test sealing apparatus.

 

[ksaves2]

Ohhhhh, So that's what a kerf is! Thanks for posting the pictures. Kurt

 

[fyrfytr310]

Main ejection. Nose came off clean along with its independent chute. The main remained largely within the airframe but with gravity being in our favor and my ability to add a little more BP, I think we should be good. I'm consulting my adviser accordingly.

[video=youtube;A1yZa_Jnm9o]https://www.youtube.com/watch?v=A1yZa_Jnm9o[/video]

Drogue deployed perhaps a little too well... I now have some repair work to do on the nose.

[video=youtube;HL111qG_NWA]https://www.youtube.com/watch?v=HL111qG_NWA[/video]

 

[jonno]

Thats excellent, how do you make the nose come apart whils't testing like that on the ground?.

 

[fyrfytr310]

Thats excellent, how do you make the nose come apart whils't testing like that on the ground?.

Electrically ignited black powder charges. Search the forum for "dual-deployment" and you will learn more than you could ever want to know