Question for those who use an eyebolt screwed into their forward closures. Have you found a means to assure the eyebolt doesn't back out? I'm looking at about a 12 minute descent, so with heat & thermal expansion I'm not sure threadlock and a locknut will hold. As an aside I usually attach to a ubolt on a separate bulkplate and I can do that here, but it'll take up more room....
Eyebolt backing out?
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I’ve never had one that was locked with a jam nut come loose. However, if you’re truly concerned an easy thing to do is use some Rockset which is a heatproof thread lock compound used to mount muzzle devices on firearms. To remove it you soak it in water. Heat will not loosen it like it does most common threadlocker compounds.
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Here is a forged eye nut..kept from unscrewing via a kevlar loop..through the bulk plate..tied together via a zip tie.
or set screw tapped into the FC...
Tony
or set screw tapped into the FC...
Tony
rharshberger
Well-Known Member
Another option would be to drill the bolt and put a cotter pin above the nut so that even if it backs of some it can't get all the way off.
Edit: I totally misread the OP, the OP is referring to the motors forward closure not a bulkhead.
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You’ll have no problem. Good luck!Hey Steve, thanks for your reply. A buddy offered up some Rockset for another aspect of the project, sounds like the way to go. Just thinking 12 minutes is long time
JerryO
If you're really worried, drill a tiny hole through the bolt and stick a cotter pin through it. If the bolt starts to back out, it will stop dead in its tracks when it hits the pin.
AHansom
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I use the ubolts and nuts off of cable clamps. Much more compact than a standard ubolt. A spinning rocket wont unscrew it... A violent recovery wont open it up.
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Ubolt won't work on a forward bulkhead.
I suggested to Jerry to try Rocksett, since it is used on gas blocks on AR-15 barrels. It gets heat shock and vibe there, and lasts. So it might be good here as well. Just note it isn't intended for gap filling like one might use epoxy! The eyebolt would need to be screwed down solidly.
Alternative suggestion - put a strap through the eye of the bolt, anchored down with two small bolts on the bulkhead. So if it comes loose, it can't rotate. Consider it a variation of wiring the bolt.
I don't think you want to drill these bolts. They are fairly tough - or you shouldn't be using it (you are using a forged bolt, right?). You'd need a carbide bit and a drillpress. Then the hole would have a weak spot.
The purpose of the hole is to put a wire through and prevent rotation. But normally that is done through the head of a bolt, which should not be under much load. Every part of an eyebolt is under load. Adding a hole is not a great idea. Also note, it already has a hole, just larger... You can use that to wire it - wire or strap like I suggested above.
Gerald
PS - Forgot to add - Given the large difference in the coefficient of thermal expansion between steel and aluminum, Rocksett might not work. I've not tested it for this application. Usually it is used with steel and steel, or steel and titanium.
https://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html
I suggested to Jerry to try Rocksett, since it is used on gas blocks on AR-15 barrels. It gets heat shock and vibe there, and lasts. So it might be good here as well. Just note it isn't intended for gap filling like one might use epoxy! The eyebolt would need to be screwed down solidly.
Alternative suggestion - put a strap through the eye of the bolt, anchored down with two small bolts on the bulkhead. So if it comes loose, it can't rotate. Consider it a variation of wiring the bolt.
I don't think you want to drill these bolts. They are fairly tough - or you shouldn't be using it (you are using a forged bolt, right?). You'd need a carbide bit and a drillpress. Then the hole would have a weak spot.
The purpose of the hole is to put a wire through and prevent rotation. But normally that is done through the head of a bolt, which should not be under much load. Every part of an eyebolt is under load. Adding a hole is not a great idea. Also note, it already has a hole, just larger... You can use that to wire it - wire or strap like I suggested above.
Gerald
PS - Forgot to add - Given the large difference in the coefficient of thermal expansion between steel and aluminum, Rocksett might not work. I've not tested it for this application. Usually it is used with steel and steel, or steel and titanium.
https://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html
I cannot imagine a jam nut with a backup jam nut coming loose.
Though, if you are really concerned. I would suggest either wedge lock washers or adhesive washers to lock your jam nuts to the forward closure. Neither of these will fail, not a chance. There is just not enough inertia to unscrew it. I have a hard time believing properly applied jam nuts would unscrew but I guess it is possible.
https://www.mcmaster.com/lock-washers/wedge-lock-washers/
Adhesive washers can be easily made from 3M VHB tape and either a hole punch or something as simple as a utility knife.
The adhesive washer will go between the binding nut and the mating surface of the forward closure. Effectively bonding them together so that they cannot unthread from each other. A jam nut could then be added above that but honestly, I really don't see it as being necessary.
Though, if you are really concerned. I would suggest either wedge lock washers or adhesive washers to lock your jam nuts to the forward closure. Neither of these will fail, not a chance. There is just not enough inertia to unscrew it. I have a hard time believing properly applied jam nuts would unscrew but I guess it is possible.
https://www.mcmaster.com/lock-washers/wedge-lock-washers/
Adhesive washers can be easily made from 3M VHB tape and either a hole punch or something as simple as a utility knife.
The adhesive washer will go between the binding nut and the mating surface of the forward closure. Effectively bonding them together so that they cannot unthread from each other. A jam nut could then be added above that but honestly, I really don't see it as being necessary.
Thread locker like Loctite.
Loctite softens with heat. That’s why I suggested Rocksett.
Ok. I have never had one back out with Loctite.
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VHB tape - an acrylic foam tape - is considered good for applications up to around 40C. It isn't the right product for the job IMHO. It will have melted by 160C. Even the low end of the recommended temperature range is not low enough for high altitude usage if that is of interest. The torque loadings listed are pretty low as well. It probably works fine for low altitude low and mid power use, perhaps even for low end of high power at least some of the time, but I'd not stick it on an O motor!
Eyebolts come loose for multiple reasons. One of the big ones is the high coefficient of thermal expansion of the aluminum bulkhead, and the relatively low coefficient of thermal expansion of the eyebolt. You might have put it on tight, but heat up that bulkhead and it is no longer tight.
You might be able to come up with a way of staking the eyebolt. That is another way to make a semi-permanent installation.
Gerald
Eyebolts come loose for multiple reasons. One of the big ones is the high coefficient of thermal expansion of the aluminum bulkhead, and the relatively low coefficient of thermal expansion of the eyebolt. You might have put it on tight, but heat up that bulkhead and it is no longer tight.
You might be able to come up with a way of staking the eyebolt. That is another way to make a semi-permanent installation.
Gerald
I’ve never had one back out without loctite.
The jam nut is really sufficient. A wavy washer or spring washer would absorb the tiny dimensional changes due to heat expansion. Rocksett wouldn’t loosen due to heat but is probably not necessary.
Rocksett is a compound made for attaching suppressors to firearms. A common problem with suppressors is loosening, due to heat and vibration and loctite fails under that circumstance. Rocksett will withstand temperatures far in excess of what a rocket bulkhead experiences. Rocket motors have very short heating period, followed by a long cooling period, even if they’re descending for 12 minutes.
https://www.flexbar.com/products/rocksett
Another option is to have some sort of anchor point off to the side and use a safety wire.
H_Rocket
Death by Powerpoint
This is probably out of far left field, but could you fabricate an aluminum attachment point an MIG weld it to the forward closure?
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Already a best practice for this. Using a torque wrench, torque the nut to 75% of the yield strength of the bolt of the either the bolt or what you are threading into. Then use the castellated nut for backup. Red Loctite is probably good enough, it is commonly used on internal combustion engines (along with the aforementioned torque spec), but if you are anxious the below arangement will not backout.
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Joe Rocket 97
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a little jb weld used as a thread locker is more than sufficient
Drill and tap the side of the forward closure about 1/4" from the end with a #6-32 tap. Use this for a brass tip dog point set screw that essentially cross-pins whatever fastener you choose to thread into the forward closure.
Very easy modification. No adhesives required. Impervious to supposed differentials in material expansion. Not permanent.
TBH, I think I am going to mod my FWD closures like this now that I think of it. I believe a properly torqued jam nut with a split lock washer or a belleville washer to take up the expansion is more than sufficient. But, as single point failures are what they are. The addition of a set screw to cross-pin the main attachment is an easy second level.
Thread adhesives have their place. I firmly believe that this is not their correct application and a mechanical means is far more appropriate.
Very easy modification. No adhesives required. Impervious to supposed differentials in material expansion. Not permanent.
TBH, I think I am going to mod my FWD closures like this now that I think of it. I believe a properly torqued jam nut with a split lock washer or a belleville washer to take up the expansion is more than sufficient. But, as single point failures are what they are. The addition of a set screw to cross-pin the main attachment is an easy second level.
Thread adhesives have their place. I firmly believe that this is not their correct application and a mechanical means is far more appropriate.
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I've used Fixit 2 part epoxy clay.
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I've been assuming the forward closure that was being discussed was the motor's forward bulkhead. A plywood mount is much easier to deal with.
kramer714
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To drill the hole in the eyebolt,
Make a simple drill jig from a coupler nut. Drill a small hole in one of the flats all the way through. Screw this onto the eye bolt as drill jig. It is really hard to drill the male screw without something like this, plus makes it easy to clamp in place for drilling.
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