Vaseline does work; lots of us (including me) have used it.
My primary reason for moving away from it initially is that it liquifies at such a low temperature, causing it to get everywhere you don't necessarily want it.
-Kevin
Vaseline does work; lots of us (including me) have used it.
My primary reason for moving away from it initially is that it liquifies at such a low temperature, causing it to get everywhere you don't necessarily want it.
-Kevin
At my local auto parts place they sell tubes of synthetic brake grease, I forget the exact name, that have caught my attention. Would that work well, or should something more specific to o-rings?
Exactly why I would not use vaseline. It is an inferior product for the application we are discussing. It's not engineered for high temp applications-- loses it's stiffnesss/viscosity even at high ambient temperatures. This can result in it going where it's not supposed to be, etc.
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I'd be curious how well vaseline actually works and what the ratio of motor failures occur when comparing types of lubricant that were used. Not sure that there's much statistical data out there though..
Again, saving a few nickels using an inferior lubricant in a rocket motor seems the poster child for penny-wise and dollar foolish.
I disagree. I think you are assuming the grease on the o-rings have some purpose and function during motor burn. I believe that is incorrect. From what I understand from the manufacturers instructions, the purpose of the grease is to preserve the integrity of the the o-rings during assembly of the motor. Once it is assembled, the grease has no function. The thermal properties of the grease are irrelevant.
I would also be interested in the ratio of failures for various kinds of lubricants, but I never heard of any failures that were ever attributed to the lubricant. It would be hard to filter out all the assembly errors, faulty parts, and other causes.
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Hande, all due respect but your logic is flawed and you mistakenly assumed something I wasn't assuming.
Three years of service repairing/maintaining missile launcher and Tank Hydraulic systems-- I've a bit of experience regarding O rings and their lubricant needs.
Actually, once assembled the function of lubricant continues to have two VERY important factors in a motor.
1) keeps the O'ring lubricated and elastic so it doesn't bind under pressure fluctuations. That way it continues to provide a seal.
2) Lubricant should stay where it's meant and not go into errant places like delay grains etc.
I've read as well as been informed by knowledgeable people that lubricant on a delay grain or in the delay spacer void will cause motor ejection failure...hmm runny, melted vaseline--not good
I will check with the VERY knowledgeable MDRA members at Red Glare VI regarding CATO's and mis use/mis application of lubricants..I'm betting that either have played a critical role in a number of motor failures.
I did some research and compared the physical properties/specifications of hi temp lubricants vs vaseline. I'll continue to use the right material for the job.
And if I happen to misplaced or exhaust mine at a launch I'll ask one of the 40 or 50 friendly people who use the right lubricant for a dab.
I appreciate the experience and technical knowledge you have. I have also had a lot of experience with o-rings and seals in various systems. I completely agree about the lubrication and use of o-rings in hydraulic/pneumatic systems. It is very critical that the correct materials and lubes be used and in the correct amounts.
I still must disagree with your position on lubricants in solid rocket motors. I think you are applying the wrong engineering to the use of o-rings in solid rocket motors and how they work in a rocket motor, which is very different then in a hydraulic/pnuematic system and any other place where an o-ring has to provide a seal against moving parts.
I think you are applying the wrong assumption in thinking it's a SOLID system. O-Rings have little or no place in solid only system. A rocket motor becomes a FLUID system once the rocket is ignited, a pressurized fluid system. In many ways similar to a pneumatics system, but with appreciably differences.
Regarding moving parts, there are plenty of 'o' rings in fluid systems that are not located at moving parts, these o rings are will move (thousanths of an inch) and mold to mating surfaces under pressurization differentials.
Handeman, I'm a bit miffed that you keep assuming I'm wrong or projecting that I'm making flawed assumptions. Thats usuallly my wife's job--I've been known to be very wrong I do hope I see you at Red Glare IV or LDRS, we could drag race our Thugs or even something larger on a K or L.
I'm mildly surprised that there are several in this thread that champion vaseline as suitable replacement for an engineered highly superior lubricant that costs slightly more money. Especially in the volatile, fault susceptible rocket motor.
My vested interest in this thread is not to be right or wrong but rather I really feel newcomers and readers seeking solutions are ill-served by the recommendation of vaseline as a rocket motor lubricant.
Ok. I will make 3 x 3 grain J motors. One I lube the rings with Dow 111, one with vaseline, and One I do not. I will fly them then take pictures. I will do this at Red Glare for all of you to see.
My hypothesis is the grease will do nothing but allow me to reuse the Orings on the bulkhead(the nozzles are 80% shot due to more heat). The one I do not grease probably will have a little more heat on the Orings since the grease is not there to take the heat for the 2.5 sec burn.
Ben
I use vaseline becasue that's what Ed LaCroix said I should use. I tend to trust the designer of the motor I'm using.
Now most of my reloads to date have been plugged, E6 loads, but I've used the vaseline on everything up to H's to lubiricate the lining before inserting it in the casing.
YMMV.
kj
I keep hearing about how hard it is to clean cases, but I'm beginning to wonder if the lubricant on the liner is burning/oxidizing or some how causing the problems with the casings picking up all the hard to clean debris. I've only flown a dozen or so HPR loads, H to K but mostly I loads. I've never lubed the liners and I've never had one that was hard to get out or left hard to clean debris in the casing. Maybe the problems aren't all that common, I'm 0 for 12 on HPR and probably 0 for 50 on the hobbyline loads.
I'm not assuming you are wrong, I just disagree with your assumptions. I could be wrong with my assumptions. I'm also not saying that some lubricants aren't a lot better then vaseline in most locations that o-rings are used. In fact I would never use vaseline on most o-rings I've ever used. I just feel that when used in rocket motors, that vaseline is an acceptable and viable lubricant and does not contribute to motors failures in any significant way. I think in some ways we look at the lubricant the way a lot of us overbuild our rockets. Granted that motors can fail in so many ways, but most of them are easily attributed to assembly error (including how it was lubed), grain voids, or part failures. I've just never heard of a case where the lubricant was the cause of a failure.
I suspect on this subject we might have to agree to disagree. But it sure was interesting discussing it with you. Thanks...
I'm planning on being at LDRS (slot 18) and I would love to drag the Thugs! Any patricular motor class or is it "run what ya brung"? I've got my Rocketry 201 I just flew on a K and J for my L2 cert. That might make a good drag too. Maybe we can get together one night in NY and talk motor lubricants over a couple of adult lubricants!
Ben, thanks for the consideration regarding the testing. I'd just rather watch you burn loads of AP at Red Glare 6 with motors loaded the way you normally do them.
It basically comes down to products that are made for the job at hand and products that are made for other purposes that will work. Most rocket builders are GREAT at using products other than what they are made for. Personally, I am going to find some of the Slick 50. If I get in a pinch and need something quick, I am glad to know I CAN use vasoline with good success. Never know when you may forget to get out to buy more grease.
Not being smart enough to stay out of this one....
Sounds like there are a few different problem here that everyone is trying to solve with one answer.
Problem 1) O-ring lube - goal lubricate the o-ring, don't mess anything else up.
Almost any of the lubricants mentioned here will lubricate the o-ring, at the risk of being flamed out of existence, the requirements for the o-rings on rockets isn't very severe, the pressures are not that high (in o-ring terms) and the installation is pretty benign. As a bunch of people said, the o-ring lubricaition isn't to help it seal but help it slip into place, a dirty case or cut ring wont provide a good seal with or without grease. The main problem people seem to have is getting grease on the delay. I'm swearing off Vaseline because it does transfer, plus I cant get tape to stick worth a darn after I use Vaseline.
Problem 2) Sticking threads - Goal- finger tight on, same fingers used to remove it. Easy to clean.
I don't know about you but the threads take most of the time cleaning. the gunk in there never really seems to go away, chasing a thread with a toothpick gets kind of boring after a while. I have used a product called Breakfree CLP from a gun store, less gunk good results, again I think this is a case where less is more. I'm wondering if it acts like mold release (see Problem 3).
Problem 3) Sticking liners. Goal- have the liner slide out after launching even when we (never happens right?) forget to clean them after a launch.
I have been greasing those suckers up, 29mm and 38mm, with cases that have been used for 40 plus launches. I think that greasing up the liner is, wait for it, a mistake. Im planing to do an experiment on my cases in the future, yes I will take a hit for the team. At work we use high temperature mold releases to protect anodized aluminum tools from oxidization from epoxy curing agents and to keep parts from sticking. The 'good stuff' actually bonds onto the tool, don't think wax but think a bonded layer. I'm planning to use a product called Freekote 44 https://tds.us.henkel.com//NA/UT/HNAUTTDS.nsf/web/058AA7D048724E028525715C001BD5A6/$File/FREK44-NC-EN.pdf that is good to temperatures well above 400 F, it is actually advertised to 400C!! but I haven't ever used it that high. It should prevent the liners from sticking, be good for MANY launches, and doesn't transfer.
For cleaning threads--a stiff nylon toothbrush dipped in your solvent of choice should help.
I'd imagine vaseline will do more harm than good to the O rings.
Not to mention (oopsy, I guess I did) it melts in the Texas heat. Nothing like finding a big ole slick in your range box....
That's a valid suggestion Ben, but since I don't fly research, using snap ring cases would severely limit my choice of loads when you consider the assortment the vendors in my area carry.
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