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Think so? Even with a shouldered eye on a fully compressed split washer?
 
I use a jam nut and loctite. I have no reference on the use of a split washer, I'll leave that for others who have used them. Makes me nervous, but it might work ok.
 
Does anyone have vibration analysis data from HPR motors (I don't see the recovery stage being an issue)? Seems like most vibration would be in the axial direction as opposed to the lateral or torsional directions shown in the test. Also, the test appears to have the threaded rod fixed which would not be the case in a rocket recovery system scenario. I would think that the eye bolt would vibrate at the same frequency and in the same direction as the motor case yielding no relative motion between the components and no loss in the integrity of the joint. This said, the motor is not the only source of vibration, there would also be aerodynamic and sonic sources but again, we aren't talking NASA level sustained flight (the only sources I could find on this topic). This is all adding up to some desire to develop my own vibration detection system for further study. :cool2:

Not arguing here with anyone, just wanting to expand my knowledge and apply accordingly. Has anyone had a failure at this point in their systems that they can reasonably attribute to the vibrations that occur from motor thrust and non-powered flight? The hillbilly in me says to throw some loctite on it and be done but the engineer in me screams to analyze and understand :D
 
fyrfytr310 said:
Does anyone have vibration analysis data from HPR motors (I don't see the recovery stage being an issue)? Seems like most vibration would be in the axial direction as opposed to the lateral or torsional directions shown in the test. Also, the test appears to have the threaded rod fixed which would not be the case in a rocket recovery system scenario. I would think that the eye bolt would vibrate at the same frequency and in the same direction as the motor case yielding no relative motion between the components and no loss in the integrity of the joint. This said, the motor is not the only source of vibration, there would also be aerodynamic and sonic sources but again, we aren't talking NASA level sustained flight (the only sources I could find on this topic). This is all adding up to some desire to develop my own vibration detection system for further study. :cool2:

Not arguing here with anyone, just wanting to expand my knowledge and apply accordingly. Has anyone had a failure at this point in their systems that they can reasonably attribute to the vibrations that occur from motor thrust and non-powered flight? The hillbilly in me says to throw some loctite on it and be done but the engineer in me screams to analyze and understand :D
Click to expand...

Twice I have had split washers come loose in the exact application you show on both 54mm and 75mm hardware. I am no mechanical expert, but my guess is that tugging and more importantly the spinning come during the deployment and descent stage of the flight. Don't get me wrong, I haven't sworn off split ring lock washers. Yes, when flat they don't provide much help, but as they loosen there is definitely some mechanical "bite" to keep the associated washer from beginning to spin freely. I now just keep them away from high stress areas like the motor bulkhead as shown and use them on low-stress locations such as auxiliary (read: not undergoing deployment stresses) wing nuts on av-bay bulkheads and the like.
 
fyrfytr310 said:
Does anyone have vibration analysis data from HPR motors (I don't see the recovery stage being an issue)?
Click to expand...

The recovery phase is the issue. The off axial load of the chute opening could loosen it just enough, then the spinning will finish it off. Regardless, I do what successful people do. I don't think a TAP member would approve of a split washer in that application unless loctite was also applied.

Just trying to make sure you have a successful cert flight. :)
 
Binder Design said:
The recovery phase is the issue. The off axial load of the chute opening could loosen it just enough, then the spinning will finish it off. Regardless, I do what successful people do. I don't think a TAP member would approve of a split washer in that application unless loctite was also applied.

Just trying to make sure you have a successful cert flight. :)
Click to expand...

I hear ya and I sincerely appreciate the input and feedback!
 
Not much progress. Took advantage of some downtime at the in-law's to mark the fins for some sanding this week.

ImageUploadedByRocketry Forum1438552918.933434.jpg

Going to do rounded leading edge with tapered trailing edge. Will leave tips square.

Still need to make the epoxy decision so I can actually put things together. Leaning towards Aeropoxy but I can buy West locally. Part of me wants to try clay for the fillets too but I have never worked with it before so maybe not.
 
NO clay....you will screw up a great looking rocket.

Do them like so many others by thickening epoxy with something like West 206 to peanut butter consistency & pull them smooth with a tool of some sort.

See the sticky at top of page for index on how to or search forum..there are tons of threads on this.:wink:

See what shipping is on whatever you would order. Sometimes when I want epoxy "now" I also go to a West marine. Higher than web order, but by the time shipping is added, usually pretty close & no waiting.
 
fyrfytr310 said:
Lol. You guys crack me up. I've seen some builds using clay that turned out well but I think for this one I will stick with what I know.
Click to expand...

OK, sure, as CJ also knows, it can work. But much thicker and tougher to get the perfect concave shape. Also tends to be more brittle and prone to cracking. Go for the West, Aeropoxy, US Composites with appropriate fillers or if you do prefer a thicker putty consistency try RocketPoxy (that is as close to clay as I will go).
 
dixontj93060 said:
OK, sure, as CJ also knows, it can work. But much thicker and tougher to get the perfect concave shape. Also tends to be more brittle and prone to cracking. Go for the West, Aeropoxy, US Composites with appropriate fillers or if you do prefer a thicker putty consistency try RocketPoxy (that is as close to clay as I will go).
Click to expand...


And WAY harder to sand.

You have a great looking rocket...we just want you to keep it that way!
 
fyrfytr310 said:
Not much progress. Took advantage of some downtime at the in-law's to mark the fins for some sanding this week.

View attachment 269013

Going to do rounded leading edge with tapered trailing edge. Will leave tips square.

Still need to make the epoxy decision so I can actually put things together. Leaning towards Aeropoxy but I can buy West locally. Part of me wants to try clay for the fillets too but I have never worked with it before so maybe not.
Click to expand...

This is just me, so take it for what it is, but I no longer try to shape the leading and trailing edges of my fins. I remember when I always wanted to sand the edges to a get a knife edge, or make the rocket look real sleek etc. But I have succumb to the fact that I am not going for altitude, so I must resort to looking good... and nothing messes up the lines of a beautiful rocket than messing with that leading and trailing edge line and not getting just right. All my wood fins remain square, to preserve the nice lines, and they still fly and look great. One caveat here, is if you have the tools, and are great with wood, then by all means, manicure those claws!

Again, this just what I would do.
 
Can't add pictures when editing? Weird.

Anyway:

ImageUploadedByRocketry Forum1438652333.201847.jpg

Aft centering ring in position. I have opted for West 105/206. I wanted to get a good layer of epoxy on the underside of this ring. I created some epoxy dams with tape, that ultimately failed, to keep the epoxy in place and away from the fin slots.

ImageUploadedByRocketry Forum1438652499.816440.jpg

I'll be doing some sanding through the slots once dry but I'm ok with that. Tomorrow I will put the MMT in position and maybe get some fin work done.

Resting for the night:

ImageUploadedByRocketry Forum1438652631.560261.jpg
 
I got to sanding the fins today. As I stood in front of the belt sander I had to have some real talk with myself. In recognizing my limited skills in wood work, I decided to go for the plain Jane rounded edges instead of the rounded leading edge and tapered trailing. I know, I know. No guts, no glory.

ImageUploadedByRocketry Forum1438736814.272422.jpg

I decided to do the final finishing by hand so I would go too far with the belt.

I was right about needing to sand the epoxy from the CR. As such I, worked one slot until one fin would fit. The fins and matching slots were numbered and set aside for installation tomorrow.

ImageUploadedByRocketry Forum1438736977.905175.jpg

I then insert the MMT into the tail and secured with JB. I then mixed a batch of West reinforced with milled fiber and applied to the rear CR. I also injected some through a fin slot to pool around the MMT.

ImageUploadedByRocketry Forum1438736989.953826.jpg

Definitely overkill on the fin can epoxy so I am prepared to add weight to the nose if need be.
 
So what am missing here? The instructions say to mount the forward CR 1/4" from the end of the MMT. The instructions also imply and the diagram shows the forward fins butting up to the CR. But have a look:

ImageUploadedByRocketry Forum1438821411.714931.jpg

ImageUploadedByRocketry Forum1438821422.979394.jpg

ImageUploadedByRocketry Forum1438821440.964285.jpg

Where did I go wrong?
 
Move the ring down. I sometimes give a bit extra length on the MMT. Also, don't reference anything off of the slots in the shoulder of the cone. Those are oversized slots to make sure there is enough clearance during assembly.
 
Last edited:
fyrfytr310 said:
That was my plan ultimately but I just wanted to make sure I didn't already screw this thing up. Thanks!
Click to expand...

No problem. If I have a MMT already cut that is an inch or so over, I just throw it in there. MMT's are not super precise and always are cut long.
 
Forward CR set with West, milled fiber and silica. Resting for the evening. (I hope the fillet on the bottom side doesn't decide to run! I will probably be up checking on it for a while.)

ImageUploadedByRocketry Forum1438825987.879824.jpg

ImageUploadedByRocketry Forum1438826006.848055.jpg
 
Binder Design said:
Move the ring down. I sometimes give a bit extra length on the MMT. Also, don't reference anything off of the slots in the shoulder of the cone. Those are oversized slots to make sure there is enough clearance during assembly.
Click to expand...

fyrfytr310 said:
That was my plan ultimately but I just wanted to make sure I didn't already screw this thing up. Thanks!
Click to expand...

fyrfytr310 said:
Forward CR set with West, milled fiber and silica. Resting for the evening. (I hope the fillet on the bottom side doesn't decide to run! I will probably be up checking on it for a while.)

View attachment 269431

View attachment 269432
Click to expand...

Pretty awesome to have the kit maker at your side literally every step of the way on this build. It is looking like you are off to a great start.
 

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