~Loop Quantum Crapien~

[Scott Evil]

The ambiance has been a little chilly lately (-16 today) for cutting fins out so being the little problem solving monkey that I am, I went after some other issues.

This rocket is designed for the ability to install a 50+ inch motor. The design also uses direct drogue harness attachment to the motor hardware instead of other methods. (see rocksim).

Just an eyebolt on the forward closure of my CTI 75mm 6 grain motor hardware (biggest I have, gotta make it work) makes harness attachment kind of a PITA when it's 12" down a 4" tube right?

 

[Scott Evil]

After looking for quite a while, I finally found some knarly a$$ hardware a guy could do some damage with.

I bought two and then separated them with extreme prejudice (but didn't heat 'em up and turn 'em blue in the process).

One I'll use for the motor attachment, two I'll use for the av-bay and the forth for the nosecone.

 

[Scott Evil]

For the motor mount attachment I welded a nut to a 12" hunk of 3/8" threaded rod and secured the clevis/framis with couple hard washers and a nylock keeper.

This spins like it's on bearings! Weeeeeeeeeeeee!

I fancied it up a little with some red 3/8" ID poly to cover the rod and used a wingnut as a locknut for demonstration purposes (I might use a nylock to help me sleep better).

These parts are kinda heavy and expensive but they negate the need for D-rings on sewn Kevlar endloops.

Pros? Cons?

 

[dixontj93060]

Uh, what can I say... KNARLY.:headbang:

 

[Scott Evil]

Uh, what can I say... KNARLY.:headbang:

Thanks Tim, ...:headbang:

 

[blackjack2564]

Pros? Con?

Well ....

I see a snagging point for your recovery harness. If it drops around the the rod and shackle, when the apogee fires, it will pull out the shock cord with a vengeance. It is quite possible it could wrap around, get caught on or tangle on your extended fitting, preventing a nice even stretch of the cord. I have seen this cause loss of L-3 attempt.

Looking at your file it shows 2 tubes for the fincan. Looking at the picture I see one.
Are they already coupled together?
Or is another one go on top? If not seems awful close to av-bay.
Bulk plate on top of your rig to keep harness from dropping around it?

If you have this issue addressed . OK then. If not, what then?

A simple resolution is to just bolt on your shackle right to the top of the motor.
When prepping for flight, before the motor goes in, drop the recovery line through the motor mount out the rear of rocket.
Attach to bolt on top of motor outside of fincan & install motor with shock cord already attached. This is how I do it and several others I've seen.

Leaves all the space clean for shock cord & nothing to tangle on.

My 2 cents.

 

[dixontj93060]

Yes, for sure. But knarly is not perfect. Knarly is, well KNARLY. Life's a beach. Surf's up dude!

Pros? Con?

Well ....

I see a snagging point for your recovery harness. If it drops around the the rod and shackle, when the apogee fires, it will pull out the shock cord with a vengeance. It is quite possible it could wrap around, get caught on or tangle on your extended fitting, preventing a nice even stretch of the cord. I have seen this cause loss of L-3 attempt.

Looking at your file it shows 2 tubes for the fincan. Looking at the picture I see one.
Are they already coupled together?
Or is another one go on top? If not seems awful close to av-bay.
Bulk plate on top of your rig to keep harness from dropping around it?

If you have this issue addressed . OK then. If not, what then?

A simple resolution is to just bolt on your shackle right to the top of the motor.
When prepping for flight, before the motor goes in, drop the recovery line through the motor mount out the rear of rocket.
Attach to bolt on top of motor outside of fincan & install motor with shock cord already attached. This is how I do it and several others I've seen.

Leaves all the space clean for shock cord & nothing to tangle on.

My 2 cents.

 

[sodmeister]

Scott ,how are you cutting the fin slots in the BlueTube ,I`m nearing that point very soon on my AIM-9 Sidewinder.Tools ,I have plenty of tools,just wondering if you use jigs and a router.I`m cutting 1/4" wide slots 15" long x 4

Paul T

 

[ClayD]

what keept the whole thing from un-threading from the motor?

 

[blackjack2564]

what keept the whole thing from un-threading from the motor?

Lock washer or nylon lock nut or Loctite on threads.

 

[Scott Evil]

Pros? Con?

Well ....

I see a snagging point for your recovery harness. If it drops around the the rod and shackle, when the apogee fires, it will pull out the shock cord with a vengeance. It is quite possible it could wrap around, get caught on or tangle on your extended fitting, preventing a nice even stretch of the cord. I have seen this cause loss of L-3 attempt.

Looking at your file it shows 2 tubes for the fincan. Looking at the picture I see one.
Are they already coupled together?
Or is another one go on top? If not seems awful close to av-bay.
Bulk plate on top of your rig to keep harness from dropping around it?

If you have this issue addressed . OK then. If not, what then?

A simple resolution is to just bolt on your shackle right to the top of the motor.
When prepping for flight, before the motor goes in, drop the recovery line through the motor mount out the rear of rocket.
Attach to bolt on top of motor outside of fincan & install motor with shock cord already attached. This is how I do it and several others I've seen.

Leaves all the space clean for shock cord & nothing to tangle on.

My 2 cents.

Thanks Jim, your :2: is always welcome.

The idea was to to keep from having to that but as you point out, the way I have it is snag city. An easy fix. I'll go with plan "A" and pop the shackle right on top of the forward closure.

Attached was just photos of the raw motor mount tube and hardware. Picture a 7.5" zipperless fin can but with a centering ring instead of a bulkhead on top.

Sorry, the 2D on the RockSim is a little busy. Scooting parts around with the components menu helps identify what is what.

 

[blackjack2564]

Why not just cut the MM down to 3ft. & glue a 1in flat strap Kevlar Y-harness to both sides of the MM through a notched top CR and between the fins ala Wildman style.
3ft is plenty for any length motor, unless you need longer because of the dual fins.

Keep your idea and connect the top of the motor to the recovery harness with a 6ft tail. [ or whatever size you deem needed]

Now you got the best of both, redundancy and no way anything is getting lost.

This done in many extreme projects. Not necessarily just wildman style but also when eyebolts are used on the top CR too.

It's done a lot where folks want to be sure they don't lose a motor case due to retention failure.
Especially big heavy motors.

Or a ballistic main event that would otherwise cause the motor to come out due to the horrific shock load of a high speed chute opening.

I always tie my motor to the recovery harness on anything 75mm & up.

Why? Because 2x I have yanked the motor out the back, but was lucky enough to find it. [before someone turned me on to tying the front of motor to recovery]

Anyhow just a thought. Glad to see you making some progress!

 

[Scott Evil]

Scott ,how are you cutting the fin slots in the BlueTube ,I`m nearing that point very soon on my AIM-9 Sidewinder.Tools ,I have plenty of tools,just wondering if you use jigs and a router.I`m cutting 1/4" wide slots 15" long x 4

Paul T

I'm not sure yet Paul.

A router + jig is probably the cleanest cut but I'm not good enough with it yet to try it on a $90 tube.

I'll probably use my jigsaw or dremmel. I used a dremmel with a nice thin diamond cutting wheel to cut the lengths and that turned out pretty much error free.

 

[sodmeister]

I'm not sure yet Paul.

A router + jig is probably the cleanest cut but I'm not good enough with it yet to try it on a $90 tube.

I'll probably use my jigsaw or dremmel. I used a dremmel with a nice thin diamond cutting wheel to cut the lengths and that turned out pretty much error free.

Thanks for your input Scott.Perhaps I`ll have to do a little experimentation on spare B-tube.I was thinking 1/4" solid carbide down spiral cutter and a jig ,but as you said ,don`t want to waste too much tube $$$$
I`ll post results.

Cheers

Paul

 

[gdiscenza]

Paul,

You might want to take a look at a compound spiral bit, designed for routing clean edges on both sides of a piece of plywood. The lower half of the cutting surface is an up-spiral, and the upper half is a down-spiral. the effect is that the center of the material is slightly compressed during cutting, reducing chip-out on both faces. For any thicker layered material, it is the bit I would reach for first. You can buy them online from Woodcraft.

G.D.

 

[sodmeister]

Paul,

You might want to take a look at a compound spiral bit, designed for routing clean edges on both sides of a piece of plywood. The lower half of the cutting surface is an up-spiral, and the upper half is a down-spiral. the effect is that the center of the material is slightly compressed during cutting, reducing chip-out on both faces. For any thicker layered material, it is the bit I would reach for first. You can buy them online from Woodcraft.

G.D.

Indeed ,great bits ,but pretty "mucho dinero".Seems most come in 3/8 & 1/2 diam. ,but even 1/4" are not cheap.

I have an Onsrud 1/2" dbl.comp. bit I bought years ago online ,cost me almost a hundred bucks !

Think I`ll have to try the down spiral on this one ,or at least try it out.I have used it for slotting Phenolic before with good results ,but I may have to re-learn the process I used.

Paul

 

[Scott Evil]

Why not just cut the MM down to 3ft. & glue a 1in flat strap Kevlar Y-harness to both sides of the MM through a notched top CR and between the fins ala Wildman style.
3ft is plenty for any length motor, unless you need longer because of the dual fins.

Keep your idea and connect the top of the motor to the recovery harness with a 6ft tail. [ or whatever size you deem needed]

Now you got the best of both, redundancy and no way anything is getting lost.

This done in many extreme projects. Not necessarily just wildman style but also when eyebolts are used on the top CR too.

It's done a lot where folks want to be sure they don't lose a motor case due to retention failure.
Especially big heavy motors.

Or a ballistic main event that would otherwise cause the motor to come out due to the horrific shock load of a high speed chute opening.

I always tie my motor to the recovery harness on anything 75mm & up.

Why? Because 2x I have yanked the motor out the back, but was lucky enough to find it. [before someone turned me on to tying the front of motor to recovery]

Anyhow just a thought. Glad to see you making some progress!

Sorry, it took a bit to run this through my head.

I'd say my av-bay bulkheads may be more likely to fail structurally under a mondo shock load but they don't have several pounds of APCP packed inside to break them before they get to do their job.

The primary shock load are intended to focus on the forward closure of the motor hardware to keep the fin can attached to rest of the rocket. If this fails via cato or other event, there could be a fairly heavy fin can doing the free fall thing.

So tentatively, I'll go with what I have but add some redundancy like you suggested. I'll pop some split foam pipe insulation around my long swivel invention to keep the Kevlar from looping inside the unused MMT and also add a Wildman style loop through the centering rings and epoxied up the distance of the MMT through the top (CR1).

With the threaded yolk style swivel still right out in the open at the top of the motor mount, I can secure both the sewn Kevlar loop and the MMT loop at a much closer tension point if that matters much more than just convenience of assembly.

Thoughts?

 

[sodmeister]

Just a note on the slotting of BlueTube.I made a 3 sided box ,24" long and 3" wide and 2 1/2 tall to hold the tube in.I routed a 1/4" slot down the center ,starting 1" from the bottom and running 16" long (for my purposes)I double stick tape some 120 grit sandpaper on the sides to help grip the tube ,and ran it dwon my router table/table saw using a 1/4" down cut spiral carbide bit.It worked out quite well ,just a single edge razor blade to clean up the slot ridges and a few swipes of 180 SP and Bob`s your uncle !!

I used 1/4" Baltic Birch for the bottom and 3/4 BB for the sides.Just had to make sure all was square and 90°.I ran the jig against my Biesemeyer table saw fence.

Paul T

 

[Scott Evil]

After months of R &($) D...

FINALLY...


Some viable fins!

 

[sodmeister]

Scott ,I presume the router bit you now used made things go smooth.Could you tell me what bit you ended up purchasing ,as I will be in the market for one soon.

Fins look great BTW ,and yes R&D can indeed be quite costly (probably less than my mortgage )

Cheers

Paul

 

[Scott Evil]

Paul, I picked up one these https://www.mcmaster.com/#31615a22/=b44zbi
for cutting the CR's with a Jasper Jig

and two of these https://www.mcmaster.com/#35505a61/=b45188 for trimming the fins out.

Basically what I did was rough cut the G-10 so it was about an 1/8" larger on all sides. clamped it to the original birch fins and just went after it with the router.

I did find that the little end knob on the bit liked to burn into the wood and cause little divots if your not careful. No flaws you can see at arms length but not 100% perfect either. ( < 0.5mm deep, some type of filler should get it nice and pretty)

Turning the router speed down to about 60% or so seemed to help that quite a bit.

The flush cut bit got pretty tired and slow on the last fin but probably still has some life left for thinner material.

 

[sodmeister]

Sounds good Scott ,thanks for the info.I also do the same for ply fins ,rough cut then place on a master fin template and run it on the router table using a bit with a bearing.

Great project BTW !

regards

Paul

 

[dlb]

Lock washer or nylon lock nut or Loctite on threads.

Exactly, less weight, more room and no tangles, KISS!

 

[Scott Evil]

Exactly, less weight, more room and no tangles, KISS!

I've put quite a bit of thought in this set-up and am still thinking through all the fault modes. The more opinions the better.

 

[Scott Evil]

I wanted to re-do some of the bulkheads and centering rings in G-10 but was not satisfied with my current tooling. So I picked up a for reals Jasper Jig. Well, it didn't fit my cheapie router so I made my own using the Jasper as a template. (this "Watering Hole" post got me kicking myself in gear https://www.rocketryforum.com/showthread.php?t=19497 )

Some re-posted photos if you don't feel like double linking into TRF.

 

[Scott Evil]

My apologies for the dis-continuity and gaps in time on this thread. It is what it is.

Rocket is designed to fly up to six grain + 98mm but only having 75mm 6 grain hardware on hand, here's what I came up with to keep the recovery materials from getting stuffed and snagged down the motor mount.

I hawged a disc out of aluminum instead using foam or something to barricade the recovery materials from getting looped around the threaded rod extension I put on the forward closure.

The third pic represents some redundant harnessing. If the motor blows the forward closure, there's still some Kevlar to keep the rocket more or less as ONE object falling from the sky.

 

[patelldp]

My apologies for the dis-continuity and gaps in time on this thread. It is what it is.

Rocket is designed to fly up to six grain + 98mm but only having 75mm 6 grain hardware on hand, here's what I came up with to keep the recovery materials from getting stuffed and snagged down the motor mount.

I hawged a disc out of aluminum instead using foam or something to barricade the recovery materials from getting looped around the threaded rod extension I put on the forward closure.

The third pic represents some redundant harnessing. If the motor blows the forward closure, there's still some Kevlar to keep the rocket more or less as ONE object falling from the sky.

I understand your concern...but holy cow man! That is overkill, not to mention a lot of weight in the rear of the rocket. I've never seen someone prepare for the motor to blow a forward closure before.

I have a Competitor 5 kit that I recently flew on a 76-6000 load, and all I do is quick-link the shock cord to the top of the motor. The eyebolt in the case is locked in by a nut and lock washer so it doesn't rotate. On the flight previously mentioned, the rocket had spun so many times that the cord went from 30' long to just under 10'. The eyebolt didn't budge.

In the grand scheme of things, it appears that you have prepared for the worst. If I were you, I would rely on the Aeropack retainer to hold the motor, and then attach your kevlar to the motor mount via a pair of forged eyebolts, or the way that PML and Wildman kits glue the cord to the motor tube.

 

[Scott Evil]

I've been stewing on getting the ends of 7 1/2" Blue Tube nice and flush so all the body sections fit nice and cool style.

No joy with guaranteeing perpendicular on some knarly bandsaws in my neighborhood.

What I did was cut a length of banding steel (like the stuff you use to secure boxes down to a pallet) and then hawg an 8" hose clamp around it.

This theoretically makes for a nice surface to sand down to.....Theoretically...I have yet to stack up the tubing after all the the power sanding, we'll see if they all fit later...

S.E.

 

[Scott Evil]

I've never seen someone prepare for the motor to blow a forward closure before.

You Have Now... :roll:

 

[Scott Evil]

I understand your concern...but holy cow man! That is overkill, not to mention a lot of weight in the rear of the rocket. I've never seen someone prepare for the motor to blow a forward closure before.

I have a Competitor 5 kit that I recently flew on a 76-6000 load, and all I do is quick-link the shock cord to the top of the motor. The eyebolt in the case is locked in by a nut and lock washer so it doesn't rotate. On the flight previously mentioned, the rocket had spun so many times that the cord went from 30' long to just under 10'. The eyebolt didn't budge.

In the grand scheme of things, it appears that you have prepared for the worst. If I were you, I would rely on the Aeropack retainer to hold the motor, and then attach your kevlar to the motor mount via a pair of forged eyebolts, or the way that PML and Wildman kits glue the cord to the motor tube.

Actually Dan, I think I'm doing exactly what I think you're recommending in the last paragraph.

1) I have an Aeropack retainer to capture the motor hardware on the back end..

2) The recovery harness attaches directly to the forward closure of the motor hardware. My version looks exotic but is essentially just an imitation of bigger motor hardware.

3) There's an extra "WildMan" loop of Kevlar as a back-up to keep the fin section attached regardless of a motor failure.

I know that trashing the forward closure on motor hardware hardly ever happens, ...but...