- This topic has 391 replies, 29 voices, and was last updated 12 years, 4 months ago by
Kevin Osler.
Kevin Osler.-
Posts
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Warren B. Musselman
As I recall we had 100% success with the exploding bolts on the Delta II project. We should use the same technology again.
smashburn
As I recall we had 100% success with the exploding bolts on the Delta II project. We should use the same technology again.
We didn’t actually use bolts on the Delta .. we connected the boosters using 2 pvc endcaps .. one inside the other .. and the charge inside them. That worked to secure and stabilize the boosters.
These are needed to secure 2 bulkheads together (flush). I’ll have some pics of the process soon.
Adrian
For the exploding bolts, I’d recommend Quest Q2G2 ignitors because we can run as many bolts in parallel off of one electrical output as we want.
For the booster, I could make up a couple of small plywood sleds that have the Ravens with Power Perches and batteries, and mail them to you guys for installation. The sleds could be installed anywhere that puts one edge within 2.5″ of the outside and that has some venting to ambient. No hatches or switch holes are required, and the last access to top off the batteries can be up to a couple of weeks before the launch. On each outboard we can either put an arming switch on each one at the back end of the airframe, or just wait to install/connect the outboard ignitors until the rocket is upright and recovery electronics are armed.
For the sustainer, I don’t know enough about the Tiltometer or the sustainer recovery plan yet to suggest a configuration. We’ll want a GPS also.
smashburn
I am unable to find my copy of Rocksim from several years ago, on CD, since I moved in Aug .. and so much stuff went into storage. I d/l’d a trial of the new version but it has timed out and I can’t afford to buy it now.
just sayin’ … 🙂
Also, I need some 38mm MMT’s .. 3 @ 12″ or so and 1 – 54mm @ 12″ or so. Anyone .. anyone ..
Any thoughts on adding motors to the 3rd stage .. a small blackjack or something like that for effect. We will already be separating the 3rd stage for recovery purposes .. so .. just thinkin’ out loud .. 😉
BEAR
Steve, I was going to get some nylon bolts, drill a hole in the hex head, then scribe the circumference 1 1/2″ down from the head on the outside, in the threads. I was thinking of placing powder and two redundant ignitors and then sealing the hole up with wires coming out. I was also going to drill holes the diameter of the bolts in two pieces of 3/4″ plywood, bolt them together and try the bolts out in my bar-b-que pit. What size bolts are you thinking of?
smashburn
Steve, I was going to get some nylon bolts, drill a hole in the hex head, then scribe the circumference 1 1/2″ down from the head on the outside, in the threads. I was thinking of placing powder and two redundant igniters and then sealing the hole up with wires coming out. I was also going to drill holes the diameter of the bolts in two pieces of 3/4″ plywood, bolt them together and try the bolts out in my bar-b-que pit. What size bolts are you thinking of?
Kevin hasn’t gotten back to me yet, but I’d think pretty big … 5/8 or so? needs to be something we can easily drill and get 2 igniters in … and would hold this big stuff together.
get some video of it if you can..
Thanks!
edward
I can give you a few tips on something similar to the bolts. I built a parachute reefing/ line cutter mechanism off of something that Tony A. posted.
http://tqc.yuku.com/reply/32555/2010-Balls-project#reply-32555
Post #27 is a picture of what I have.
It is 1/2″ OD aluminum, .062 wall, .375 ID. I threaded both ends for 1/8 NPT and drilled a hole perpendicular to cut the lines needed.
The very first one I built I sealed that sucker up tight. I drilled out my NPT plug, put and e-match in the bore and epoxied it up. I used copious amounts of teflon thread seal tape when installing it. The delrin piston that I was using had 3 o-rings on it to seal.
I used 2 grains 4FFFF in the e-match well and then 5 grains Reloader 25 on top of it. I then used a small patch of cotton ball on top and then the piston.
I tested it. Worked great – until I had to tear it down. The o-rings really didn’t slide, the grabbed the sides of the tube and rolled and tore and got chopped horribly. The piston was a single use item and had squished where the o-rings were from hitting the plug stop on the other side. It was also a pain to dig out the epoxy to re-pot the e-match.
The 2nd after I drilled out the e-match I just tied a knot in it and threaded it through with a dab of braces wax and seated it tight. I used just a little bit of thread seal tape. My piston DID NOT have any o-rings. It was 3/8″ diameter and slid easily in the tube. I again loaded 2 grains 4FFFF and 5 grains Reloader 25, put the cotton patch on and then the piston. The tie wrap was holding the piston tight against the cotton so there was no free room.
Tested it the 2nd time. Worked perfectly. Cleanup was a breeze this time. Drop the piston out, discard. Pull e-match out, discard and use a q-tip to clean up any wax. Worked exactly the same with 1/4 the prep effort.
I tested it 10 times, and 10 times it worked perfectly. You don’t need to seal everything up gas tight for devices like this to work. No need to epoxy seal the wires. Just run them through and use some wax/putty to get a seal.
If you are using 5/8″ diameter bolts I’m guessing you’ll have at least a 1/4″ diameter hole down the middle. I’d really advise then to tap that hole. Once you get your bolts prepped and loaded instead of an epoxy plug, run a piece of nylon all thread all the way through to seal it using a cotton patch to hold it. Turn around time will be consistent. You will have a much more consistent break and no worry of the epoxy strength being different bolt to bolt. And it will be easier to manufacture. Bore a hole out, ream to size, tap. Groove the outside, then finish drilling your lead holes through. No glue, no fuss, no mess and field re-packable in-case a lead wire breaks, loses continuity, etc. You don’t have to wait for epoxy to cure. You just have to dump it out, replace the e-match and then put the plug back in.
I don’t know how you are holding the plates together, but I’d get the strength of the material of nylon you are using and then figure the minimum area you need to hold them together, then add your factor of safety. From that you can calculate how deep your outside groove needs to be to leave that area in the form of a cylinder between the groove and the inner bore. Also, the groove should probably be a v-groove instead of a nice flat bottomed groove. That way it gives a place to break, though threads are the best stress concentration points around (essentially being one long helical groove)
Anyway, I’m rambling and will stop now.
Edward
BEAR
Thanks for the input Ed. For my prototype testing this weekend, I was not going to use epoxy at all. I was planning on drilling about a 1/4″ hole from the hex head end, drilling down about 2″ and tap it for about a 1/4″ with 1/4-20 thds. (This is to give greater surface area for the hot glue to adhere to. The groove on the outside is quick and dirty. I chuck the bolt up in my Jacobs chuck on my drill press and then use a thread file to file a groove into the spinning bolt. Once it is un-chucked, I check for thread damage and chase the threads. I will load 4F into the hole, and then insert the ignitor(s), (I may possibly reverse that procedure, depending on how assembly goes). On top of that I will place a ball of recovery wadding, and then seal the assembly with my hot glue gun. My experience has shown that things come apart when they get to move around. Then the damage starts. I believe this is true of ignitors also. Once the ignitors are in the bolt and covered with 4F, where they cannot move, and then the wadding on top of that to insure that there is no movement, I will check continuity. If good, then it gets sealed. Of course, before the bolts are installed in the rocket, the continuity is checked again. I am also believing I will have enough room for two ignitors for redundancy. My O.D. groove will be 3/4″ from the bottom of the bolt head so that it should come apart in the middle of the two 3/4″ plywood plates/bulkheads. My only concern might be debris jamming something, so the holes the bolts go through should be oversize. Experimentation should prove this out. (Great theory, now we get to prove it.)
Adrian
For the bolted interface, I would suggest to design it so that the airframe tube of each section is butted up against each other and the nylon bolts just preload that interface. That way, as long as the preload from the bolts isn’t exceeded, then the stiffness of the whole airframe will be about the same as if it were an uncut airframe. Stiffness is important because the last thing you want while the rocket is going up is any thrust or aero misalignment. Having the airframe tubes but against each other also will maximize the leverage that the bolts will provide when they resist bending. Are you guys thinking of using in the neighborhood of 8-12 bolts for each joint?
Bear, do you have Q2G2 ignitors for your bolt tests? I have a bunch.
BEAR
No, Adrian, I do not. I was preparing to order some. If you are coming to the launch Saturday, I would be happy to take some from you. Since we live probably about 70 to 80 miles apart, the only other way to get any is to mail some. I do have some Rocketflite ignitors that I made up, still a little pricey, but they work good and I may go through a bunch of ignitors in running a success/failure test.
This reminds me, any idea of how long I need the tails on the ignitors for the finished product, Steve? 12″
Steve, if you ran some half inch pins through the mating plates, it seems that it might reduce some of the strain that will be put on the bolts, which might help prevent failure. What do you think?
Warren B. Musselman
smashburn
Adrian
BEAR
edward- The forum ‘Archives 2012’ is closed to new topics and replies.