Ayush Chauhan
Well-Known Member
Alright guys, This is the final design for the rocket. I am also attaching the .ork file just if anyone is curious to see the changes or see the design itself in detail!
Need HELP with making a rocket!
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I was ninjad by about a half dozen posts, including your pictures of the parts for the layout. The layout I'm showing below is almost the same as wheat you've got above; the only key difference is the separation plane.
So, the parachute is in the upper portion, and is pulled out by the shock chord that's attached to the lower part, have I got it? That's called "head end deployment" or HED, and it's a valid approach. But it's usually considered second best to having the parachute in the lower part, to be pushed out by the ejection charge. Push the 'chute out, don't pull it, when you can; when you can't, HED is OK. But this time, I believe you can push the 'chute out by simply placing it below the separation plane. That is to say, place the separation plane between the parachute and the ebay. Other than that, you've pretty much got a typical configuration.
OK, young paduan, here's a typical setup. This is not the only way, but this is a good way.
At least one ebay bulkhead should be removable, as you noted. It's a nice thing for convenience to have both ends removable, and that turns out to be just as easy. The most common method is to run one or two threaded rods the full length of the ebay, and use wing nuts with lock washers and/or locktite to hold everything together. Then set the whole rocket up like this:
* Sometimes, people will pin the lower ebay to booster tube joint, but with shear pins, i.e. something designed to break under sufficient load. That keeps the joint together on the way up while still allowing the ejection charge to push it apart. In a rocket this size, I think that would be unusual and unnecessary.
Final note, sometimes there actually isn't any ebay tube, and the electronics are mounted in the space of one long coupler. If you go that way, yo need a way to assure you've got ventilation, which can be done by adding a band of body tube at the middle of the coupler. That band sits between the upper an lower tubes, and you put your vent holes through there. It's called a switch band, because it's also where you mount externally accessible switches for electronic payloads that need any. You don't have to do it that way; use a section of tube it it's convenient.
So, the parachute is in the upper portion, and is pulled out by the shock chord that's attached to the lower part, have I got it? That's called "head end deployment" or HED, and it's a valid approach. But it's usually considered second best to having the parachute in the lower part, to be pushed out by the ejection charge. Push the 'chute out, don't pull it, when you can; when you can't, HED is OK. But this time, I believe you can push the 'chute out by simply placing it below the separation plane. That is to say, place the separation plane between the parachute and the ebay. Other than that, you've pretty much got a typical configuration.
OK, young paduan, here's a typical setup. This is not the only way, but this is a good way.
At least one ebay bulkhead should be removable, as you noted. It's a nice thing for convenience to have both ends removable, and that turns out to be just as easy. The most common method is to run one or two threaded rods the full length of the ebay, and use wing nuts with lock washers and/or locktite to hold everything together. Then set the whole rocket up like this:
- Detachable joints use screws or removable plastic rivets.
- The nose cone to upper tube may be removable or fixed, as you prefer.
- The upper tube need not be any longer than is needed to connect the upper ebay coupler to the nose cone shoulder.
- The upper ebay coupler to upper tube joint is removable.
- The upper ebay coupler to ebay tube joint is fixed.
- The lower ebay coupler to ebay tube joint is fixed.
- Separation occurs at the dashed line.
- The lower ebay coupler to booster tube is a removable*.
* Sometimes, people will pin the lower ebay to booster tube joint, but with shear pins, i.e. something designed to break under sufficient load. That keeps the joint together on the way up while still allowing the ejection charge to push it apart. In a rocket this size, I think that would be unusual and unnecessary.
Final note, sometimes there actually isn't any ebay tube, and the electronics are mounted in the space of one long coupler. If you go that way, yo need a way to assure you've got ventilation, which can be done by adding a band of body tube at the middle of the coupler. That band sits between the upper an lower tubes, and you put your vent holes through there. It's called a switch band, because it's also where you mount externally accessible switches for electronic payloads that need any. You don't have to do it that way; use a section of tube it it's convenient.
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Ayush Chauhan
Well-Known Member
What is a coupler's ID and the OD?
Can you please tell me the reason? Cuz after this I will start working on a high altitude rocket! And just for the sake of knowledge and my own curiosity XD
So I just simply don't attach it? What if the rocket turns into a different direction (might happen since it's my first try) and when it does the ebay might pop out of the rocket and the fact that it will be firmly fit into the rocket which might not be safe either.
waltr
Well-Known Member
Looks much better and should work. Just re-think things through before gluing. Also fit parts and check on how you get things apart and back together.
Did forget you are in the UK. Sorry for the US link.
Looks like the kit designer intended the Baffle to also couple the lower and middle tubes together.
If the 5cm long couplers are glued at one end then these can work. Just insert the glued end 1cm to allow 4cm for the 'loose' end into the next tube. Re-check the instructions to see how they planned this to work.
Did forget you are in the UK. Sorry for the US link.
Looks like the kit designer intended the Baffle to also couple the lower and middle tubes together.
If the 5cm long couplers are glued at one end then these can work. Just insert the glued end 1cm to allow 4cm for the 'loose' end into the next tube. Re-check the instructions to see how they planned this to work.
Ayush Chauhan
Well-Known Member
It's alright bro
Yes! Exactly my point. But I will buy a 8cm coupler to go in it.
I need two couplers so the parachute is joined to the lower and upper part of the rocket.
Look it up at the manufacturer's web site, or measure it.
If the rocket goes up without a vent in the booster tube, that tube holds ground level air pressure until separation. As the surrounding air pressure goes down, that internal pressure can be enough to cause separation before the ejection charge. But you've got to get quite high to worry about that.
It needs to stick together under light loads, and pop apart when the ejection charge goes off. Just like the nose cone on the little low power kit you built and flew after we all urged you to back in January. You did that, right? Oh, you didn't? Well, here we are.
You need to ensure that it's a snug fit, doesn't wiggle around, doesn't fall out of you hold the rocket (with the motor installed) by the payload tube, but also isn't really tight or difficult to pull apart. It's something you gain a feel for after you've built a few rockets and had several flights, including a few failures, so you know what feels wrong as well as what feels right.
(Many of us advised you to build and fly at least one low end, low power, low price rocket to learn on. We were not just trying to make you spend more money and time, and this is the sort of thing we wanted you to learn before going big.)
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rcktnut
Well-Known Member
My suggestion: Got to go now more to come later will explain later.
Ayush Chauhan
Well-Known Member
Measure what? I don't even know what that means in the first place.
So what do I do if it's too lose? Adding a sticky material might make it very difficult to come off.
If it's super tight then I can always sand it using a sand paper.
I like a challenge man. Making a small rocket isn't fun or exiting I want the thrill and the challenge, and I know with sufficient knowledge I can get this rocket to fly like butter. I understand that to do something big you need to start small and I think an E class motor is very small compared to what is ahead.
Titan II
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ID=Inside diameter
OD=Outside diameter
A challenge would have been to start at the building and increase your skills in a logical manner rather than haphazardly reinventing the wheel as you go.
As far as what to do when a fit is too loose, add a single wrap of tape to very slightly increase the outside diameter of the inner tube/nose cone.
rcktnut
Well-Known Member
By doing it this way the only other thing you will need is a solid coupler bulkhead, you will not need a longer coupler. Everything else is glued together. The little outer BT lets call it a sleeve will reinforce the separation point. Pin the nosecone for access to your altimeter. This is a better option for chute deployment also. Just a suggestion do what you think is best.
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That was the point. E may not have enough power to lift at reasonable speeds is probably what the poster was referring to.
Ayush Chauhan
Well-Known Member
I think this is the plan I am looking for. Very thanks for the idea. I will just go with this. This cuts the hassle of me getting a bigger coupler.
Masking tape. I know someone who did it with cellophane tape (scotch tape), which melted in the very short time that it should take to pop the nose off, and succeeded in gluing the nose cone to the tube.
No, I believe he was referring to the fact that BP E engines have a bad habit of blowing up.
That's a very good point.
Ayush Chauhan
Well-Known Member
Got it. Masking tape it is. But I am going with this new plan that @rcktnut suggested in #307
So that way I will not have to buy a bigger coupler since at that point I will also have the external coupler (not sure what the exact term is) and an internal coupler.
External coupler looks like this:
Any external piece like that is usually called a sleeve. "External coupler" is quite descriptive. You're using a sleeve as an external coupler.
If you've got wiggly joints, whatever ultimately is going to hold them together - permanent, removable, or a flight separation joint - you should definitely firm them up by building thickness (generally with masking tape). If it's wobbly before you screw it together, it'll probably still be a little wobbly after. Wobbly is bad.
If you've got wiggly joints, whatever ultimately is going to hold them together - permanent, removable, or a flight separation joint - you should definitely firm them up by building thickness (generally with masking tape). If it's wobbly before you screw it together, it'll probably still be a little wobbly after. Wobbly is bad.
Ayush Chauhan
Well-Known Member
OK got it! I still have no idea how tight it has to be. Cuz you said it should be tight enough so it should be able to sustain the weight of the body tube. But what if I shake it up and down and it comes off? Does that mean it's lose?
rcktnut
Well-Known Member
It should separate if you shake it. Just pick it up by the nosecone/ebay section. If it doesn't separate your good to go.
Glad you like my suggestion. With half the coupler and half of the sleeve at the separation point you will have a good connection. The standard is you want at least the same length of coupler as the dia. of your body tube holding your separation point together. With the coupler and sleeve combined together that will do the trick. Also I would apply some thin CA (super glue) to the upper part of your BT/ebay were the nosecone goes and where your pins/rivets go through. This will reinforce that area. Don't soak it, I squeeze some out of the bottle and use the tip to spread it out. Just a thin film is all you need. Let it totally dry though before you insert the nosecone, or you will have a big problem.
Ayush Chauhan
Well-Known Member
OHH! I see what you have done. But instead of CA(super glue) I have some normal PVA glue. That I used to assemble the motor mount. I not sure if I will be able to get super glue. Is PVA glue and super glue the same thing or am I getting it wrong?
And also after adding the layer of glue and letting it dry. Should I also add pins after? that go into one end of the body tube and pierce into the nosecone?
It just occurred to me that you might not know what we mean when we refer to rivets. We're talking about plastic inserts that have some sort of button on top.
It's not always a mushroom head on top, but something like that. When the top is pushed down (or in, or whatever) the bottom spreads like a metal riven, but it can be removed to be used again when you pull the hear up.
That picture is from digikey.com. They're also available at Apogee Components, but I don't suppose you want to pay shipping from Colorado. One can also usually find them ad auto parts stores and hardware stores.
CA glues come in at least three thicknesses, referred to as thick, medium, and thin. Good old Krazy Glue is medium. There are brands of thick, sometimes called gel, in many hardware stores and other places that medium can be found. Thin, on the other hand, flows like water, or maybe even more freely. It will soak into the fibers of wood products, including paper and cardboard. Once it sets there it makes the region much harder and stronger (not the same thing, and it gives you both).
If the best you can do is coat an area with PVA then I guess that's probably better than nothing, but @rcktnut will certainly have an opinion on that, and probably a much better informed one than mine. But it's the thin CA that you really want.
Also, be careful with this stuff. It flows at least as freely as water, it can go seconds or minutes without encountering some substance that initiates its curing, and then cure in a fraction of a second.
It's not always a mushroom head on top, but something like that. When the top is pushed down (or in, or whatever) the bottom spreads like a metal riven, but it can be removed to be used again when you pull the hear up.
That picture is from digikey.com. They're also available at Apogee Components, but I don't suppose you want to pay shipping from Colorado. One can also usually find them ad auto parts stores and hardware stores.
White glue and yellow wood glues are polyvinylacrylate (PVA). Superglue is cyanoacrylate (CA). Not at all the same thing.
CA glues come in at least three thicknesses, referred to as thick, medium, and thin. Good old Krazy Glue is medium. There are brands of thick, sometimes called gel, in many hardware stores and other places that medium can be found. Thin, on the other hand, flows like water, or maybe even more freely. It will soak into the fibers of wood products, including paper and cardboard. Once it sets there it makes the region much harder and stronger (not the same thing, and it gives you both).
If the best you can do is coat an area with PVA then I guess that's probably better than nothing, but @rcktnut will certainly have an opinion on that, and probably a much better informed one than mine. But it's the thin CA that you really want.
Also, be careful with this stuff. It flows at least as freely as water, it can go seconds or minutes without encountering some substance that initiates its curing, and then cure in a fraction of a second.
Yes, that's the point. The reason for the CA is to make the cardboard tube more durable at the hole where the rivet goes through. You are not gluing the nose cone in.
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Ayush Chauhan
Well-Known Member
you guessed that right. When you said "screws" to insert in the body tube and the nose cone I was thinking about using this:
but a way smaller version of it. And put 4 of these in parallel to each other.
But with the one you suggested there is 1 problem.
How will I put the other end of the revert? when the body tube will be closed? Am I supposed to glue the bottom end of it on the inside and then slap the screws on from the outside? Am I on the right track?
I am pretty sure my school will have these. Since I go to an engineering school.
First, screws are OK, it's just that the removable rivets can be very handy.
There is no "other end" to these. They go in something like this:
Later you can pop the head back up, remove the rivets, remove the nose cone to do what you have to do, then put it all back together and reuse the rivets. They wear out after - I don't know - two or three or five or thirty uses, and they're very cheap.
There is no "other end" to these. They go in something like this:
Later you can pop the head back up, remove the rivets, remove the nose cone to do what you have to do, then put it all back together and reuse the rivets. They wear out after - I don't know - two or three or five or thirty uses, and they're very cheap.
Ayush Chauhan
Well-Known Member
OHHH so that's how it works!! Got it. I will see if I have these rivets at my school.
What do I do if I don't have any at school? can I just use a plain ordinary screw?
rcktnut
Well-Known Member
I have plenty of those rivets here that I will never use. If you can't find any I will mail you some in an envelope free of course. They are black but the heads can be lightly sanded and painted. One of them will be plenty to hold your nosecone on. Wizard Rockets has thin CA as should most any store, hardware etc. in your area. Thin CA really makes a difference to the strength of a cardboard tube especially when penetrating it with a rivet.
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Here in the States, I've never seen thin CA hardware store. I can only get it at hobby shops.
waltr
Well-Known Member
I suggested "Sheet Metal Screws". these look like this and even a UK hardware store should have them.
Soaking some Thin CA glue into the cardboard tube where screws or rivets go is a good idea. I do this and it works well.
Soaking some Thin CA glue into the cardboard tube where screws or rivets go is a good idea. I do this and it works well.
Ayush Chauhan
Well-Known Member
I will see if I have any in school in Monday first. And let you know. Very thanks for you offer and support. I will let you know if I need any.
Ayush Chauhan
Well-Known Member
Yea I was thinking of doing the same thing too... But I will explore rivets and play around with them and see how that goes. And then ultimately I have this as my backup option anyways so nothing to worry about here really.
Ayush Chauhan
Well-Known Member
This is the electronics bay that I designed for the Arcas Rocket.I want to double check with the size of vent holes.
I made 2 vent holes directly above the altimeter that have a diameter of 5mm.
I made a slot so I can toggle the on/off switch of the altimeter without taking the whole ebay out. I know that this slot will also act as a vent hole. So should I remove one of the holes above the altimeter? Or I can keep all 3 holes and get away with it?
The slot has the following dimensions:
