After that lengthy tirade this morning, how about some news that’ll put a smile on your face?
Cameron Wade, one of two students whom BABloggers helped fly to a rocket launch, wrote a report about his trip on SpaceRef.com.
My favorite lines (besides him talking about his first plane ride and first time in the ocean) was about his experiment, which involved having bolts with nuts screwed on them to see if they would stay together during a launch:
The launch was great, but it was very fast. There were two testing rockets, then a Super Loki. It was worth getting up so early. We got our experiments back. I got to help bring the boxes back to the lab. Our bolts came apart. How do they hold the space station together?
I love hearing that! He saw the results, and immediately extrapolated to a new situation. When I read that I figured we have a new scientist in the making. And then he said this…
We want to try putting the bolts together another way to see if that will make them stay together better. Maybe we can send up that experiment next year.
… and I knew we already have a new scientist.
June 16th, 2006 at 1:55 pm
Yes, he’s learned the valuable lesson of retrospective experiment design. This is a technique I use all the time …:)
Well, you see, what we should have done was to have 5 nuts and bolts fastened normally; 5 fastened with normal washers in place; 5 fastened with spring washers; 5 fastened with spring washers and locking nuts; 5 fastened with “Nutlock” applied; and 5 more should have been Nylock nuts.
Nuts.
June 16th, 2006 at 1:55 pm
Hey, what happened to my smiley?
June 16th, 2006 at 2:19 pm
“How do they hold the space station together?” (scratches head) You know, that’s a darn good question!
June 16th, 2006 at 3:18 pm
He inspired me. A typical kid would have written something like:
Our bolts came apart. This is bullsh*t!
I should have stayed home and watched television.
June 16th, 2006 at 5:36 pm
And a kid from Kansas would have written something like:
The bolts came apart. Since there were no hands turing the bolts, it is evidence that God can work a wrench
June 16th, 2006 at 5:37 pm
That is very cool. It’s great to see kids’ minds expanding like that. It was worth the donation just to read that.
June 16th, 2006 at 5:40 pm
Bleah, sorry for 3 posts in a row, but I saw this:
Then we built our model rockets. We put in streams instead of the parachute.
and had to comment…
That’s how I build my model rockets too – much greater chance of recovery because they drop more-or-less straight down, slowed by the drag of the streamer rather than blowing all over the place on a parachute. Greater chance of recovery = less expensive model rocketry hobby.
So the kids learned two cool things
June 16th, 2006 at 9:51 pm
A rocket scientist in the making….
June 17th, 2006 at 9:28 am
“How do they hold the space station together?â€
Blake, it’s held together by international politics. There’s no other reason to carry on wasting money on it, after all!
On the other hand, if the bolts came undone as a result of the launch (all that vibration and acceleration), and the ISS was assembled in orbit, then there’s no problem. The individual ISS modules could be held together by rivets, which wouldn’t (I think) come undone during launch. So there you have it.
June 17th, 2006 at 11:07 am
I’m not sure that they did this with the space station
but I know for a fact that to keep bolts, screws, nuts, etc. from unscrewing on airplanes that they put a screw
too big for the hole and dip it in liquid nitrogen. The
bolt rapidly contracts to become small enough for the hole. They screws the ultra-cold screw in. The screw expands in the hole and it is nearly impossible to get the screw out again.
June 17th, 2006 at 11:16 am
Duck tape.
Lots and lots of duck tape.
June 17th, 2006 at 11:04 pm
FWIW, much of the F-16 is held together with industrial adhesives! Yep, it’s glued together!
June 18th, 2006 at 4:41 am
I’m particularly happy to see the so early result of the experiment. Prompt answers are always welcome. And the kicker is the youngster is quite obviously the right stuff. His future is assured. Let’s give him, and others, the best opportunity to shine, by providing the means and wherewithall, to mature. It’s a perfect reason to NOT cut back or delay or cancel those proposals that have been determined are necessary for the meaningful development of Space Exploration.
Now for my two bits worth on the vexing question of nuts and bolts. What about the threads of both being right AND left handed, ie., two spirals, with a special screwdriver that has the opposite function to normal, needing to pull and turn the screw to tighten, and push and turn to loosen. The function of the two threads is that there would now be only a fifty per cent chance of loosening naturally.
And any self respecting nut that thinks it can outwit that strategy will have another think coming. Confused? Any nut would be. But think about it.
So congratulations to all involved in the experiment, and to those who encouraged a worthwhile endeavour.
Ivan.
June 18th, 2006 at 7:09 am
Oh, really? I didn’t know that F-16’s were glued together. 747s are made that way though
June 19th, 2006 at 7:04 am
[...] Update, thanks to Phil. [...]
June 19th, 2006 at 8:50 am
icemith, I’m having trouble following what you said.
1. How does one screw have threads both right and left threaded? (I can think of one way, but I want what you had in mind.)
2. How do you reverse the action of the screw? More specifically, you put the bolt through the hole. How do you thread the nut on the end and then tighten away from the direction of travel? This I can’t figure out.
3. Left or right shouldn’t matter. Handedness makes sense when you have a rotation effect – that can drive the threads to back out. But vibration is not handed – straight vibration can cause both to simultaneously unwind. It is the stressing and relaxing of the metal that releases the inherent friction, which allows the bolt to back out. The bolt will automatically back out the correct direction.
What’s not clear from the experiment was whether the bolts and nuts were installed into something, or just threaded together. That will have an influence.
Besides installation torque, there are other things – patched fasteners, locking helicoils, locking nuts, chemical adhesives, lockwire. All depends on the design intent. Yes, rivets and welding can be used in some places.
June 20th, 2006 at 10:12 am
Irishman, maybe I was a bit exurberant in trying to think out loud, and express a vague concept.
First, I cannot see a problem in having a double (helical) screw thread. It would leave diamond-shaped ‘hills’ lined up on the bolt shaft, and also the hole inside the nut. But why? So there would be a choice of which nut to use, depending on the specific requirement. One locking strategy could be to use a spiral wire or spring to insert in the other spiral groove or thread space to lock it in. Another is to manipulate the thread design and shapes and angles that would offer the highest resistance to movement, however caused. That has probably been a requirement for a century or more though, but it has to be re-examined for every new material and every new age , and application.
Then a tool is needed to apply the nut etc, we are talking about a very specific tool, designed to be used specifically for these connectors.
As for the second question, it relates to these tools. It would require some sort of device to pull against the direction of the travel of the nut. Magnetic- probably not, but using spring pressure, relieving a certain resistance built into the nut thread, or even the bolt or both. I know we are talking about small objects here, but compared to nanotubes, this is rocket sized, if not rocket science.
I would like to see what others could make of these maybe impossible ideas, someone may solve the problems, as they usually do. I too wonder why it seems an advantage to have the twin helical threads, just an idea looking for an application. (Reminded of the story (myth?) of lasers- a concept that had no immediate use when first demonstrated.) Jeez it is hard trying to convey a concept with words only. I could draw things better, and I may try that for proof of concept on paper. Give me time. Cutting, or moulding those threads may also be problematic.
Ivan.
June 21st, 2006 at 8:50 am
1. Yes, if you spiral wrap the bolt in both directions you will have a pattern of “diamond shaped teeth” rather than a full thread. It would not be practical to do both the bolt and the nut. If you did, the teeth would slip through each others gaps and the bolt wouldn’t hold.
2. I think it would help to have an understanding of how bolts work. The bolt and nut are squeezing something between them. Engaging the nut and turning the bolt, the thread strecthes the bolt like a spring. The more you turn, the more you stretch, until you reach the yield strength of the bolt. Then it either permanently deforms (threads bend), or the bolt breaks.
The bolt is secured by the friction between the bolt and nut threads. That friction is a material property, and is effected by the materials used for each, and also whether lubricant is used. Yes, sometimes you want to use lubricant in your bolts. “But that reduces the locking friction!” That’s a drawback, but different designs have different needs.
So what happens if you double spiral your threads, so you could install it either left or right handed? You make your bolt useless. The whole grip of the bolt is accomplished by riding the threads against each other. Yes, you typically only engage about 3 or 4 threads between the bolt and nut, but you need to engage those whole threads. The gaps in the diamond teeth threads mean you have less surface area in contact, which means less friction. Oops. There is also the possibility of galling the metal, meaning the metal deforms and sticks together. Now your bolt may not come apart – ever. Makes it hard to replace.
Thread shape isn’t that variable. Some bolts have big threads, some smaller. That makes more threads per inch, but takes more turns to install. As for the thread profile, you have to be able to machine it with a precision cut, you don’t want too sharp of corners in the bottoms of the threads because those cause stress concentrations that can make the bolt break early. And you want to be able to cut the spiral inside and outside of holes. The beveled spiral cut is pretty optimized.
The key is to use permanent fasteners where possible (i.e. rivets, welding, making from one piece of metal, etc). Where you must use bolts, use secondary locking features. That means lockwire, or pins, or locking nuts and locking plates, or adhesives – any number of methods. Also, soft stow. If you don’t have to hard mount to the walls, pack in foam all the way around to dampen the vibrations.
3. I still can’t figure out how you can tighten the bolt to the nut while pulling the bolt away from the nut. First you have to get the bolt through the hole in the objects you’re bolting. Then you have to engage the nut. The nut has to go on after the bolt goes through the hole. How does the nut get onto the bolt if not threaded on from the end? Then you have to stretch the bolt to apply preload to the objects being bolted together. How do you stretch the bolt by pulling it away from the nut, and have the bolt squeeze in on the bolted objects? You are increasing the distance between the bolt head and nut and trying to squeeze the items in that zone. That does not make sense.
June 28th, 2006 at 10:57 am
OK Irishman, I’ll go away and think about what you said. But I think there is more than one way to skin a cat. ( To use an old expression that may not be political correct now!).
Words like leverage, pressure, friction, spring loading come to mind at the moment. Are there any machinists out there trying out this idea, and can it be optimised?
Ivan. ( PS, Maybe this should be considered elsewhere, as I think Phil would agree it is off-topic.)
June 29th, 2006 at 1:20 pm
Somebody needs to look at the hydraulic bolt tensioning industry and the hydraulic wrench industry. There’s a wealth of information on this topic. Better yet, Google “hydraulic bolt tensioning” or “hydraulic torque wrenches” or even hydraulic bolting. You’ll find everything you ever wanted to know about it.