Well I think our time will be most well spent on the parachute release designs and on creating the procedures. I am not sure where either team is in terms of completion, but either way it is something we must get done.
Well I think our time will be most well spent on the parachute release designs and on creating the procedures. I am not sure where either team is in terms of completion, but either way it is something we must get done.
Rocketeers,
Please keep in mind that we have also FOUR events coming up in the next three weeks or so:
1) Presentation to Henniker Rotary + launching a rocket - May 17th
2) Presentation to Goffstown Rotary
3) Day trip to the University of New Hampshire/ Space Grant Consortium event - We're setting up a display table and we are one of the official presenters!
4) Presentation at the McAuliffe Planetarium on Friday, June 3 (6:45 PM) - They're serving pizza. Yummy!
And of course getting the parachute release mechanism is our big priority. The ARLISS launch is drawing very near.
I'm sorry I didn't respond on the board. I had to Mr. Kibler by email, but I should have posted here as well. From Friday through Sunday I was away on a camping trip. I can meet anytime on Thursday other than I need to be at a Boy Scout meeting at 7 P.M. By then I should be able to mount the wheel backwards and test Mr. Kibler's idea.
Hi all,
Sorry you didn't hear from me, I was in Quebec with my French class! it was really cool to be surrounded by French speaking people and the culture. I will have a finished procedure for the meeting this Sunday.
Emily
Hi all again-
There wasn't much conversation this weekend and I felt there should definitely been more after Mr. Kibler's and my post. What do you all think about it? We are at a crucial point and need to continue strong until the trip is over. As Mr. Kibler says, "work needs to get done outside of practice as well. Sorry to have to bring this up but it is very important we continue to talk and work on ideas (mostly parachute designs)
Justin- Are you free Thursday? I would like to work on your design with you if that is okay. Run it through some simple tests.
Thanks again,
-Jake-
Jake,
Indeed, we have very little time left and a key component of the project has yet to be completed. If you do work with Justin this Thursday, please keep me updated on any new changes, etc. that are made. In addition, please keep in touch via the forum and/or e-mail with any design updates. I haven't heard much on this subject in a while.
If you guys get a chance, take a look at the May/June 2011 issue of Sport Rocketry magazine (the publication of the National Association of Rocketry). They finally printed my article about the MAWD telemetry thing. I mentioned your project (or rather, your project from two years ago, when I wrote the article) in it, so Mark and Dr. Allen are mentioned by name.
No Andrew I am not out there, but I am in here.
So what is the exact status of the parachute release mechanisms? Like what are your current models like?
MAWD telemetry? Would that be explaining how the MAWD figures out the altitude or something else.
One thing I would like to know is whether or not the design team will be meeting this Thursday? I suppose not due to the conversation so far on the forum, but there are other ways we can communicate.
The upcoming presentation,
1) Presentation to Henniker Rotary + launching a rocket - May 17th
I just need a reminder on how the presentation is proceeding. I remember vaguely Justin being tasked with maybe writing a rough draft of the presentation, but I might be completely wrong on that assumption. All I know for sure, is that we are indeed working on it next practice. I just need clarification on this matter.
Jake was not able to meet today, so I just went ahead and tested my parachute release mechanism anyway. Here are the results with ten tests for each configuration:
With the block with no tension:
Success: 60%
Fail: 40%
With the block with tension:
Success: 100%
Fail: 0%
Without the block without tension:
Success: 100%
Fail: 0%
Without the block with tension:
Success: 100%
Fail: 0%
In short my design worked much better without the block than with it. I know that we need the block to protect the electronics but what if instead of having a block, what if we just sheilded the electronics. The GPS Input/Output antennae could be outside of the sheild so that it would still work. Another note is that when the rod did not come out it was because it was getting stuck on the block. I do not know if the new rod which Mr. Kibler is making me will help the problem, so it might be a good idea to test both designs at the meeting to see.
Dylan - I was not assigned to work on the rough draft, but if it needs to be done I will take a look at it. Is there a pre-existing presentation that you would like to use or did you want an all new presentation.
I thought we were using the same presentation that we used for the Bedford Rotary.
Mr. Kibler - were you able to make the new rod for my design. I just need to know if it will be read for the meeting for testing.
Jake was not able to meet today, so I just went ahead and tested my parachute release mechanism anyway. Here are the results with ten tests for each configuration:
With the block with no tension:
Success: 60%
Fail: 40%
With the block with tension:
Success: 100%
Fail: 0%
Without the block without tension:
Success: 100%
Fail: 0%
Without the block without tension:
Success: 100%
Fail: 0%
In short my design worked much better without the block than with it. I know that we need the block to protect the electronics but what if instead of having a block, what if we just sheilded the electronics. The GPS Input/Output antennae could be outside of the sheild so that it would still work. Another note is that when the rod did not come out it was because it was getting stuck on the block. I do not know if the new rod which Mr. Kibler is making me will help the problem, so it might be a good idea to test both designs at the meeting to see.
Dylan - I was not assigned to work on the rough draft, but if it needs to be done I will take a look at it. Is there a pre-existing presentation that you would like to use or did you want an all new presentation.
I thought we were using the same presentation that we used for the Bedford Rotary.
Mr. Kibler - were you able to make the new rod for my design. I just need to know if it will be read for the meeting for testing.
Justin
Justin,
Good work on the parachute release mechanism. That's excellent that you did experiments with different variables (changes).
1) How many times did you do each experiement with each change? More than once or twice?
2) What did you use that added tension??
The tension seems to be an important variable and I would like to see you run the experiments again at practice on Sunday, especially "with tension." You will, of course, be working on the mechanism.
Choose one other person to work with you until it is completed and fully operational. From here on you are the "Parachute Release Mechanism Lead." The word "Lead" is a NASA term for the person in charge of that part of the project, 'the boss" (without being bossy, of course.) You've earned the title, and so the parachute release mechanism is your (and your assistant's) responsbility from here on. Let's be 100% sure that it works in Nevada. Let's works out all the kinks before it goes into the rocket. Well done.
Yes, I do have the bolts we talked about at last practice. In fact I have a few different bolts we can try out.
When the rod slides out of the two slots on the wheels it raises up. How could we adjust things to make the rod slide out flatter and straighter? Or do you think we should adjust it at all? Does it work really, really well right now? I wonder if the stress forces on the parachute "shroud lines" (strings) will cause the bilt to move back and forth as the rover descends... what do you think? Once we decide on the ideal angle for the two slots, I'll take the rover's wheels to a machine shop in Concord and have them cut to precision.
I got an e-mail from ARLISS today and we have the name of the person responsible for launching the rocket. Apparently we have an inch more space than we thought in the payload bay. We may need it.
1. For each of the different experiments I did ten tests.
2. To simulate tension I simply hung my prototype. My prototype is much lighter than the actual robot. I assumed on a windy day the tension would be close enough to do preliminary testing of the new idea.
I think the person who would be best to be my assistant would be Jake, because he lives nearby and if we need to do additional work, it would be easier to work together. He also did a lot of work on the parachute and understand a lot about it. That is, if it is okay with Jake.
I think in order to make the desision of wheter or not we should implement my idea depends on more testing with the new bolts. These tests might lead to design changes.
It is great that we have one more inch of space. That payload bay was looking pretty full. I think that in one meeting we should actually pack the ASP-BOT into the tube with a six foot parachute just to see if it realistically fits.
Justin- I would be delighted to work with you on your design! I'm still a little confused on what the "block" is though. What is it's purpose and why do we need it (or do we)? What were the reasons for the 60% and 40%? Maybe knowing that will help us prevent from future problems.
Mr. Kibler- I'm glad to hear that you are headed to a machine shop to have a precision cut! However, I think it would be wise to not go quite yet because we may find someway to make a more efficient cut than a straight line (??).
OK, I understand the 'tension' part now. Here are three very important questions to consider:
1) Will there be tension on the parachute AFTER the rover lands (what if there's no wind that day which is entirely possible?)
2) If there's no tension on the parachute after the rover lands are we at least 95% that the bolt will disengage from the wheels? I would like to run at least 25 trials without tension on Sunday and then calculate the percentage. *95% is the minimum accepted standard in science for statistical certainty (*Correct me if I'm wrong PJ or Sylvie or Dr. Allen or anyone else.)
3) How can we ensure that it disengages if there's no tension.
2) If there's no tension on the parachute after the rover lands are we at least 95% that the bolt will disengage from the wheels? I would like to run at least 25 trials without tension on Sunday and then calculate the percentage. *95% is the minimum accepted standard in science for statistical certainty (*Correct me if I'm wrong PJ or Sylvie or Dr. Allen or anyone else.)
"Statistical certainty" is an oxymoron. I'd instead say something like "95% confidence is the typical standard used in science".
There's not really any good way to say what you mean here - the idea is sound, but it's just not something our day-to-day language handles very well. However, I would avoid words like "certainty" when dealing with science. It implies "we can never be wrong about this", and that's just not how science works.
Is it really sometimes calm enough at Black Rock that a parachute on the rover sitting on the ground won't be inflated? I wonder if you could try just taking it out on a moderately windy day and see if that's enough to pull out the pin.
It's good to see that at least most of your tests were successful though. You know that you listed without block without parachute twice in the post. Did you mean without block with tension?
Thanks for bringing that to my attention. I did indeed mean to say without block with tension.
Mr.Kibler- I believe that currently the largest problem with the parachute release mechanism is that there might not be tension on the bar. I have come up with a design that might work to solve that.
The block underneath the pole would be spring loaded so that there would always be the tension that we need. This would also help keep the rod in place as it would always be pushing the rod toward the point of the V made by the two opposite grooves.
I built a prototype of my idea posted above. It turns out that with a spring, when it is compacted it is to large for the area that we have to work with. I experimented with some different things and it seemed that rubber bands worked the best. When I test the prototype the rod actually flies out and lands about a foot away from the test area. I tested ten times with no "wind tension" and it worked 100%. Attachment not found.
I will bring this to the meeting tommorow as well as the block to test both.
It's good to see that at least most of your tests were successful though. You know that you listed without block without parachute twice in the post. Did you mean without block with tension?
See ya all tomorrow at practice,
Obie
Obie,
You must keep in mind that "most of the time" isn't suitable to launch. That being said, the progress that we've all made with the parachute release mechanism has come along quite a bit since the last meeting. I'm eager to see a demonstration of the designs at tomorrow's practice!
"Statistical certainty" is an oxymoron. I'd instead say something like "95% confidence is the typical standard used in science".
There's not really any good way to say what you mean here - the idea is sound, but it's just not something our day-to-day language handles very well. However, I would avoid words like "certainty" when dealing with science. It implies "we can never be wrong about this", and that's just not how science works.
Is it really sometimes calm enough at Black Rock that a parachute on the rover sitting on the ground won't be inflated? I wonder if you could try just taking it out on a moderately windy day and see if that's enough to pull out the pin.
Yes, "statistical certainty" was probably a misnomer. Maybe I should have said 'a virtual statistical certainty.' But then, those clever enough to understand the subtle difference between the two probably understood what I meant by 'statistical certainty.' We had a good discussion about this point at practice today, and the meaning of three sigma, six sigma, etc. Thanks for pointing this out. You can never be certain of anything but you can have a high degree of confidence about some things. (unfortunately weather isn't one of those things.)
Sylvie! What an excellent article in this issue of 'Sport Rocketry' magazine. I saw the front cover and I said, "Hey! Somebody is using a MAWD for the same thing we are!" Then I opened the cover and saw your mug... on multiple pages. What a pleasant surprise (and thanks for mentioning the team.) It's a fine article. Well done. Will we see a sequel? If you join us at the ARLISS launch on June 16-18, you could bring your rocket AND your MAWD, then do a follow-up article. The 'New Yorker' beckons you.
Hi all- Mr. Kibler wanted me to inform everyone that the meeting on thursday has been postponed and that the rotary club is very sorry for it. In other words DO NOT GO TO THE MEETING!
Can you give me an update on how the 3-panel "science fair display"
you're making is coming along? I'd like to see it at our next practice
since we need it for our next presentation and since UNH just e-mailed
to ask about it.
Also, I'd like you to write a program subroutine to make the wheels
rotate *slowly* several times, right after it lands. I think this will
give the rover a better chance of "shaking" the parachute bolt loose
from the wheel. Please post the program change to the forum with an
explanation; I'll download it and try it out.
Chase, I'm sill intrigued by your idea and I WOULD like to see it in
action at our next practice. How feasible is it to attahc it to one of
the wheels and run it using the wheel's servomotor output signal?
Thanks for the updates. A month from today we're in Nevada ~ !!!
I like the idea of slowing the rover down during its initial movement after it lands. I agree that it will give the rover a greater chance of "shaking" the bolt/ attachment loose from the wheel, which is the goal.
I like the idea of using a single eyebolt attachment instead one long bolt through both wheels because the one eyebolt approach 'proved' to be effective (6 times out of 6) on the kitchen floor. The "bolt through both wheels" idea hasn't been precitable in releasing the bolt, though it does hold on to the rover better, and with stress forces better distributed.
This begs the question, "Is it better use one eyebolt on one wheel (with greater stress force on the bolt)? Or is it better to use the "bolt through both wheels" idea, distribute the stress forces, and risk having the bolt stick in the wheels against the platform (= burned up servo motors, etc.) These are the questions our young engineers must ask and answer.
ARLISS ROCKETEERS, what are your thoughts? Sylvie and PJ, what do you think?We have one more practice left to figure this out before we pack for Nevada. ONE MORE PRACTICE ~ !
This afternoon Jake and I got together to do some testing for the new bolt idea. It seems that without any tension on the bolt it works 100%. The bad thing is that when we put tension on the bolt it worked far less effectively. Many of the times the bot just kept running around in circles around the weight we had it attached to to simulate the wind. We even stopped the bot, with the groove pointed down, but with the weight pulling at it, the bolt wouldn't slip down. The picture shows that. This might not be an accurate test though because, if the ASP was turning around the tension point would it not eventually be in line with the wind. I was wondering if to do a better test I could pick up a parachute from Mr. Kibler and use a large fan or a leafblower at a distance to more accurately portray the wind in Black Rock. Any thoughts?
Pros:
1. It works fine when there is no wind. The eyebolt easily slips from the groove.
2. It is straight forward.
Cons:
1. When we try to simulate wind by attaching the string from the eyebolt to a weight, it works only 70% of the time. This could be that the weight always holds it down in a central position while the bot circles it. Real wind would blow from just one direction. So, this we could test differently It is straight forward.
2. When we held the wheel at the angle it would be coming out of the parachute and jerked it, the screws came out of the wheel holding the survo. If this happened in flight, you would have everything freefalling.
Solution: We would have to figure out a way to better support the wheel otherwise this would be very risky.
Option 2: Bar going across with wheels in the beginning going opposite directions, with rubber bands pushing up. The bar going across is also inside a grooved block.
Pros:
1. It spreads the weight across both wheels, and even has more support given by the wood block.
2. In 20 tests simulating wind and 20 tests simulating no wind, it worked perfectly every time.
Cons:
1. With the short wave transmitter in place, there is no longer room for this design.
Solution: We could move the short wave transmitter which has already been decided is not feasible. An alternative might be to build a small platform over the shortwave transmitter and put this block on. This is untested…
Option 3: Use the bar with a curved groove around the wheel so that the block could be on the edge where there is still room to fit the block and not in the way of components.
No pros and cons since we haven’t tested it.
Any thoughts?
I will be working on this all day as it will count as my school work, so please call me at 715-4522 if you have ANY input!!!!
Also, I will be calling Parallax to see exactly how much force the parallax continuous rotation servo motor axel can withstand, and how much side to side torque...
I tried calling, but they won't be open for a couple of hours. I will call back then. Just wanted you to know I was following up on this as well, as knowing what the design constraints of the servo motor itself are would make option 1 either viable or not.
Okay, the news is not good. I called Parallax, and asked them how much weight their servo axle could hold. The answer is 42 ounces. This is the maximum it can hold that they can guarantee won't snap... 42 ounces is 2.62 pounds. Our bot weighs more than that, and with the added force of the parachute opening, it does not look good. Even the weight over two wheels is a little questionable given the above constraints of the servo itself. This seems to be a major design consideration. What do you all think? At this point, I'm thinking we would have to use some kind of block to either hold the rod or attach the parachute so as not to put so much strain on the wheels. I'm working on this... Yes, I know the time is short!!! I'm working as much as I can until I can come up with a solution that better ensures axles not breaking and everything crashing to earth. Obviously, this is new information...
This is the maximum it can hold that they can guarantee won't snap... 42 ounces is 2.62 pounds.
Our bot weighs more than that, and with the added force of the parachute opening, it does not look good. What do you all think?
But we've had the full weight of the rover suspended from a parachute and it didn't snap. How could that be if the "maximum weight it can hold is 42 ounces?" The rover must weight at least three pounds.
I'm working as much as I can until I can come up with a solution that better ensures axles not breaking and everything crashing to earth.
That's good to hear ~ ! :thumb:
You said the bolt or eyebolt doesn't cvome out of the slot smoothly. How smooth is the slot? Does it have rough edges? If you want to stop over with your Mom or dad we can use the router to made smooth, wider slots. I think that may be part of the answer.
Can you get the "single bolt through two wheels" to work without jamming? What about Chase's pulley apparatus?
The fundamental question we have to answer is, "Will the slot hold the bolt until the rover gets to the ground?" Will the bolt fall out and will the rover fall to Earth? That's even more important than having the rover land and drop the parachute bolt.
Can you arrange to come into the school and work on it here with Jake?
I bet you are getting tired of hearing from me today! Since, I can't figure out how we could possibly continue with the one wheel stress given above, I redesigned the bar going across. Since there was no room for my original tested prototype on the real bot, I am going to use the edge of the platform that we have available. I have mocked a quick prototype of the following. On to the back edge, I will screw in a c-shaped metal piece that opens up to the back of the bot. I also changed my grooves so that they are spirals for about 5 inches. The weight then would be distributed over the wheels and the metal bar that is attached to the main body, thus better supporting the bot. When the spirals turn, the bar comes out. Because it is C shaped with the wall of the C, all the electronics will be completed shielded from the bar. I hope you can kind of picture what I'm talking about. In one hour, I will go get a few basic parts, to build a working prototype. Wish me luck! This might be it! Jake/Mr. Kibler, anyone else available this afternoon to get your thoughts on the actual prototype. I could also bring what I have to the school.
You must have posted when I did. We still have to consider that the force when the parchute opens will be a big jolt, which would be more than the 3 1/2 pounds. Let me know when you wanted me to come by the school?
Comments
Rocketeers,
Please keep in mind that we have also FOUR events coming up in the next three weeks or so:
1) Presentation to Henniker Rotary + launching a rocket - May 17th
2) Presentation to Goffstown Rotary
3) Day trip to the University of New Hampshire/ Space Grant Consortium event - We're setting up a display table and we are one of the official presenters!
4) Presentation at the McAuliffe Planetarium on Friday, June 3 (6:45 PM) - They're serving pizza. Yummy!
And of course getting the parachute release mechanism is our big priority. The ARLISS launch is drawing very near.
Mr. Kibler
:cool:
I'm sorry I didn't respond on the board. I had to Mr. Kibler by email, but I should have posted here as well. From Friday through Sunday I was away on a camping trip. I can meet anytime on Thursday other than I need to be at a Boy Scout meeting at 7 P.M. By then I should be able to mount the wheel backwards and test Mr. Kibler's idea.
Justin
Sorry you didn't hear from me, I was in Quebec with my French class! it was really cool to be surrounded by French speaking people and the culture. I will have a finished procedure for the meeting this Sunday.
Emily
Jake,
Indeed, we have very little time left and a key component of the project has yet to be completed. If you do work with Justin this Thursday, please keep me updated on any new changes, etc. that are made. In addition, please keep in touch via the forum and/or e-mail with any design updates. I haven't heard much on this subject in a while.
Is anyone else out there? Obie?
Thanks,
Andrew
So what is the exact status of the parachute release mechanisms? Like what are your current models like?
MAWD telemetry? Would that be explaining how the MAWD figures out the altitude or something else.
That's all for now,
Obie
The upcoming presentation,
I just need a reminder on how the presentation is proceeding. I remember vaguely Justin being tasked with maybe writing a rough draft of the presentation, but I might be completely wrong on that assumption. All I know for sure, is that we are indeed working on it next practice. I just need clarification on this matter.
Jake was not able to meet today, so I just went ahead and tested my parachute release mechanism anyway. Here are the results with ten tests for each configuration:
With the block with no tension:
Success: 60%
Fail: 40%
With the block with tension:
Success: 100%
Fail: 0%
Without the block without tension:
Success: 100%
Fail: 0%
Without the block with tension:
Success: 100%
Fail: 0%
In short my design worked much better without the block than with it. I know that we need the block to protect the electronics but what if instead of having a block, what if we just sheilded the electronics. The GPS Input/Output antennae could be outside of the sheild so that it would still work. Another note is that when the rod did not come out it was because it was getting stuck on the block. I do not know if the new rod which Mr. Kibler is making me will help the problem, so it might be a good idea to test both designs at the meeting to see.
Dylan - I was not assigned to work on the rough draft, but if it needs to be done I will take a look at it. Is there a pre-existing presentation that you would like to use or did you want an all new presentation.
I thought we were using the same presentation that we used for the Bedford Rotary.
Mr. Kibler - were you able to make the new rod for my design. I just need to know if it will be read for the meeting for testing.
Justin
Justin,
Good work on the parachute release mechanism. That's excellent that you did experiments with different variables (changes).
1) How many times did you do each experiement with each change? More than once or twice?
2) What did you use that added tension??
The tension seems to be an important variable and I would like to see you run the experiments again at practice on Sunday, especially "with tension." You will, of course, be working on the mechanism.
Choose one other person to work with you until it is completed and fully operational. From here on you are the "Parachute Release Mechanism Lead." The word "Lead" is a NASA term for the person in charge of that part of the project, 'the boss" (without being bossy, of course.) You've earned the title, and so the parachute release mechanism is your (and your assistant's) responsbility from here on. Let's be 100% sure that it works in Nevada. Let's works out all the kinks before it goes into the rocket. Well done.
Yes, I do have the bolts we talked about at last practice. In fact I have a few different bolts we can try out.
When the rod slides out of the two slots on the wheels it raises up. How could we adjust things to make the rod slide out flatter and straighter? Or do you think we should adjust it at all? Does it work really, really well right now? I wonder if the stress forces on the parachute "shroud lines" (strings) will cause the bilt to move back and forth as the rover descends... what do you think? Once we decide on the ideal angle for the two slots, I'll take the rover's wheels to a machine shop in Concord and have them cut to precision.
I got an e-mail from ARLISS today and we have the name of the person responsible for launching the rocket. Apparently we have an inch more space than we thought in the payload bay. We may need it.
Good work Justin!
:cool:
1. For each of the different experiments I did ten tests.
2. To simulate tension I simply hung my prototype. My prototype is much lighter than the actual robot. I assumed on a windy day the tension would be close enough to do preliminary testing of the new idea.
I think the person who would be best to be my assistant would be Jake, because he lives nearby and if we need to do additional work, it would be easier to work together. He also did a lot of work on the parachute and understand a lot about it. That is, if it is okay with Jake.
I think in order to make the desision of wheter or not we should implement my idea depends on more testing with the new bolts. These tests might lead to design changes.
It is great that we have one more inch of space. That payload bay was looking pretty full. I think that in one meeting we should actually pack the ASP-BOT into the tube with a six foot parachute just to see if it realistically fits.
Justin
Mr. Kibler- I'm glad to hear that you are headed to a machine shop to have a precision cut! However, I think it would be wise to not go quite yet because we may find someway to make a more efficient cut than a straight line (??).
Thanks again,
-Jake-
OK, I understand the 'tension' part now. Here are three very important questions to consider:
1) Will there be tension on the parachute AFTER the rover lands (what if there's no wind that day which is entirely possible?)
2) If there's no tension on the parachute after the rover lands are we at least 95% that the bolt will disengage from the wheels? I would like to run at least 25 trials without tension on Sunday and then calculate the percentage. *95% is the minimum accepted standard in science for statistical certainty (*Correct me if I'm wrong PJ or Sylvie or Dr. Allen or anyone else.)
3) How can we ensure that it disengages if there's no tension.
Keep up the good work,
Mr. Kibler
:cool:
"Statistical certainty" is an oxymoron. I'd instead say something like "95% confidence is the typical standard used in science".
There's not really any good way to say what you mean here - the idea is sound, but it's just not something our day-to-day language handles very well. However, I would avoid words like "certainty" when dealing with science. It implies "we can never be wrong about this", and that's just not how science works.
Is it really sometimes calm enough at Black Rock that a parachute on the rover sitting on the ground won't be inflated? I wonder if you could try just taking it out on a moderately windy day and see if that's enough to pull out the pin.
See ya all tomorrow at practice,
Obie
Thanks for bringing that to my attention. I did indeed mean to say without block with tension.
Mr.Kibler- I believe that currently the largest problem with the parachute release mechanism is that there might not be tension on the bar. I have come up with a design that might work to solve that.
The block underneath the pole would be spring loaded so that there would always be the tension that we need. This would also help keep the rod in place as it would always be pushing the rod toward the point of the V made by the two opposite grooves.
Justin
I built a prototype of my idea posted above. It turns out that with a spring, when it is compacted it is to large for the area that we have to work with. I experimented with some different things and it seemed that rubber bands worked the best. When I test the prototype the rod actually flies out and lands about a foot away from the test area. I tested ten times with no "wind tension" and it worked 100%.
Attachment not found.
I will bring this to the meeting tommorow as well as the block to test both.
Justin
Obie,
You must keep in mind that "most of the time" isn't suitable to launch. That being said, the progress that we've all made with the parachute release mechanism has come along quite a bit since the last meeting. I'm eager to see a demonstration of the designs at tomorrow's practice!
Andrew
Yes, "statistical certainty" was probably a misnomer. Maybe I should have said 'a virtual statistical certainty.' But then, those clever enough to understand the subtle difference between the two probably understood what I meant by 'statistical certainty.' We had a good discussion about this point at practice today, and the meaning of three sigma, six sigma, etc. Thanks for pointing this out. You can never be certain of anything but you can have a high degree of confidence about some things. (unfortunately weather isn't one of those things.)
Sylvie! What an excellent article in this issue of 'Sport Rocketry' magazine. I saw the front cover and I said, "Hey! Somebody is using a MAWD for the same thing we are!" Then I opened the cover and saw your mug... on multiple pages. What a pleasant surprise (and thanks for mentioning the team.) It's a fine article. Well done. Will we see a sequel? If you join us at the ARLISS launch on June 16-18, you could bring your rocket AND your MAWD, then do a follow-up article. The 'New Yorker' beckons you.
Mark
:cool:
Thanks again,
-Jake-
Can you give me an update on how the 3-panel "science fair display"
you're making is coming along? I'd like to see it at our next practice
since we need it for our next presentation and since UNH just e-mailed
to ask about it.
Also, I'd like you to write a program subroutine to make the wheels
rotate *slowly* several times, right after it lands. I think this will
give the rover a better chance of "shaking" the parachute bolt loose
from the wheel. Please post the program change to the forum with an
explanation; I'll download it and try it out.
Chase, I'm sill intrigued by your idea and I WOULD like to see it in
action at our next practice. How feasible is it to attahc it to one of
the wheels and run it using the wheel's servomotor output signal?
Thanks for the updates. A month from today we're in Nevada ~ !!!
Mr. Kibler
:cool:
I like the idea of slowing the rover down during its initial movement after it lands. I agree that it will give the rover a greater chance of "shaking" the bolt/ attachment loose from the wheel, which is the goal.
I like the idea of using a single eyebolt attachment instead one long bolt through both wheels because the one eyebolt approach 'proved' to be effective (6 times out of 6) on the kitchen floor. The "bolt through both wheels" idea hasn't been precitable in releasing the bolt, though it does hold on to the rover better, and with stress forces better distributed.
This begs the question, "Is it better use one eyebolt on one wheel (with greater stress force on the bolt)? Or is it better to use the "bolt through both wheels" idea, distribute the stress forces, and risk having the bolt stick in the wheels against the platform (= burned up servo motors, etc.) These are the questions our young engineers must ask and answer.
ARLISS ROCKETEERS, what are your thoughts? Sylvie and PJ, what do you think?We have one more practice left to figure this out before we pack for Nevada. ONE MORE PRACTICE ~ !
Mark
This afternoon Jake and I got together to do some testing for the new bolt idea. It seems that without any tension on the bolt it works 100%. The bad thing is that when we put tension on the bolt it worked far less effectively. Many of the times the bot just kept running around in circles around the weight we had it attached to to simulate the wind. We even stopped the bot, with the groove pointed down, but with the weight pulling at it, the bolt wouldn't slip down. The picture shows that. This might not be an accurate test though because, if the ASP was turning around the tension point would it not eventually be in line with the wind. I was wondering if to do a better test I could pick up a parachute from Mr. Kibler and use a large fan or a leafblower at a distance to more accurately portray the wind in Black Rock. Any thoughts?
Justin
These are our options, and where we think we are:
Option 1: Eyebolt.
Pros:
1. It works fine when there is no wind. The eyebolt easily slips from the groove.
2. It is straight forward.
Cons:
1. When we try to simulate wind by attaching the string from the eyebolt to a weight, it works only 70% of the time. This could be that the weight always holds it down in a central position while the bot circles it. Real wind would blow from just one direction. So, this we could test differently It is straight forward.
2. When we held the wheel at the angle it would be coming out of the parachute and jerked it, the screws came out of the wheel holding the survo. If this happened in flight, you would have everything freefalling.
Solution: We would have to figure out a way to better support the wheel otherwise this would be very risky.
Option 2: Bar going across with wheels in the beginning going opposite directions, with rubber bands pushing up. The bar going across is also inside a grooved block.
Pros:
1. It spreads the weight across both wheels, and even has more support given by the wood block.
2. In 20 tests simulating wind and 20 tests simulating no wind, it worked perfectly every time.
Cons:
1. With the short wave transmitter in place, there is no longer room for this design.
Solution: We could move the short wave transmitter which has already been decided is not feasible. An alternative might be to build a small platform over the shortwave transmitter and put this block on. This is untested…
Option 3: Use the bar with a curved groove around the wheel so that the block could be on the edge where there is still room to fit the block and not in the way of components.
No pros and cons since we haven’t tested it.
Any thoughts?
I will be working on this all day as it will count as my school work, so please call me at 715-4522 if you have ANY input!!!!
Justin
I tried calling, but they won't be open for a couple of hours. I will call back then. Just wanted you to know I was following up on this as well, as knowing what the design constraints of the servo motor itself are would make option 1 either viable or not.
Justin
Okay, the news is not good. I called Parallax, and asked them how much weight their servo axle could hold. The answer is 42 ounces. This is the maximum it can hold that they can guarantee won't snap... 42 ounces is 2.62 pounds. Our bot weighs more than that, and with the added force of the parachute opening, it does not look good. Even the weight over two wheels is a little questionable given the above constraints of the servo itself. This seems to be a major design consideration. What do you all think? At this point, I'm thinking we would have to use some kind of block to either hold the rod or attach the parachute so as not to put so much strain on the wheels. I'm working on this... Yes, I know the time is short!!! I'm working as much as I can until I can come up with a solution that better ensures axles not breaking and everything crashing to earth. Obviously, this is new information...
Justin
But we've had the full weight of the rover suspended from a parachute and it didn't snap. How could that be if the "maximum weight it can hold is 42 ounces?" The rover must weight at least three pounds.
That's good to hear ~ ! :thumb:
You said the bolt or eyebolt doesn't cvome out of the slot smoothly. How smooth is the slot? Does it have rough edges? If you want to stop over with your Mom or dad we can use the router to made smooth, wider slots. I think that may be part of the answer.
Can you get the "single bolt through two wheels" to work without jamming? What about Chase's pulley apparatus?
The fundamental question we have to answer is, "Will the slot hold the bolt until the rover gets to the ground?" Will the bolt fall out and will the rover fall to Earth? That's even more important than having the rover land and drop the parachute bolt.
Can you arrange to come into the school and work on it here with Jake?
Mr. Kibler
:cool:
I bet you are getting tired of hearing from me today! Since, I can't figure out how we could possibly continue with the one wheel stress given above, I redesigned the bar going across. Since there was no room for my original tested prototype on the real bot, I am going to use the edge of the platform that we have available. I have mocked a quick prototype of the following. On to the back edge, I will screw in a c-shaped metal piece that opens up to the back of the bot. I also changed my grooves so that they are spirals for about 5 inches. The weight then would be distributed over the wheels and the metal bar that is attached to the main body, thus better supporting the bot. When the spirals turn, the bar comes out. Because it is C shaped with the wall of the C, all the electronics will be completed shielded from the bar. I hope you can kind of picture what I'm talking about. In one hour, I will go get a few basic parts, to build a working prototype. Wish me luck! This might be it! Jake/Mr. Kibler, anyone else available this afternoon to get your thoughts on the actual prototype. I could also bring what I have to the school.
Justin
You must have posted when I did. We still have to consider that the force when the parchute opens will be a big jolt, which would be more than the 3 1/2 pounds. Let me know when you wanted me to come by the school?