Roundtable Transcript: Build Events (November 25, 2017)

Okay, we're going to go ahead and kick off our third roundtable of the season, this night for Build Events! At this time I'll invite all of our panelists to introduce themselves.
JohnRichardsim
Hi! My name is Neil Mehta AKA NeilMehta. I'm the head captain of RC Murphy JHS's Science Olympiad team, and am excited to be discussing build events this evening!
NeilMehta
Hi, I'm JasperKota. I've done the following builds: Wright Stuff, Helicopters and Mousetrap Vehicle. This is my third year competing and my first year in Division C.
JasperKota
If you have a question about an event, message it to anyone with the + next to name by typing "/msg [user] [message]"
JohnRichardsim
Hi, I'm Markus Williams AKA markuswso17. Science Olympiad has been a part of my entire life, and I mainly work with build events since I hate studying. Sadly I have graduated from High School and can no longer compete, but I try to stick with scio as much as possible.
markuswso17
Hi! I graduated in 2015 after competing in SciOly for 7 lovely years. Last year, I founded PUSO and tonight I'm excited to be discussing general SciOly topics.
fanjiatian
Hi everyone! My name is Kevin Hao and I competed on Boca Raton Community High School for 3 years, 2 of which I was on the A team and competed at nationals. I competed in a large number of events and specialized in build events Electric Vehicle, Robot Arm, Air Trajectory, Scrambler, and Hovercraft. I am the president and founder of science olympiad at the University of Florida and we will be hosting a regional this year. I am also supervising mission possible at Florida regionals and states and remote sensing at Princeton.
windu34
Hey everyone, I'm adi1008. I've competed in Division C since tenth grade and currently do Hovercraft
adi1008
Reminder: If you have a question about an event, message it to anyone with the + next to name by typing "/msg [user] [message]"
JohnRichardsim
As always, I'd like to include this disclaimer: responses to any questions about rules shouldn't be treated as official opinions or clarifications and event supervisors may have differing opinions
JohnRichardsim
magic asks: "how do you determine which fans to get for hovercraft"
JohnRichardsim
For lift fans, the main goal is to get a fan with as high static pressure as you can. The force you need to support is the weight of the hovercraft (let's assume ~30 Newtons), and the area is the size of your hovercraft (assume ~0.14 m^2). If everything's working perfectly, you'd need about 30/0.14 ~ 215 Pa of pressure to support that weight
adi1008
Reminder: If you have a question about an event, message it to anyone with the + next to name by typing "/msg [user] [message]"
JohnRichardsim
For lift fans, you need to determine the amount of static pressure you need to generate underneath the skirt/plenum and get a fan that exceeds this calculation with a safety factor (generates more static pressure than is needed to compensate for losses). For propulsion fans, the optimal diameter and pitch depend on the motor rpm you will be running.
windu34
In real life, usually multiplying that number by a factor of 2-3 is good to be on the safe side, so you'd be looking for a fan with a static pressure of around ~600 Pa (going even higher just helps more) for lift.
adi1008
However since these calculations are unlikely to be super helpful, I would suggest looking for stock propellors online on amazon/ebay or another source. I purchased a DC brushed motor and a collet shaft that allowed me to attach the propellor to the motor and 3D printed a housing for the motor that included a duct. I know of others who have had success with computer fans supporting the full load so that is also another route you can take.
windu34
antoine_ego asks: "What type of back fans do you recommend for high thrust?"
JohnRichardsim
Fans with high CFM will generally generate the most thrust. Fans of this nature include certain computer fans, ducted fans, and r/c plane propellers. I would recommend a ducted fan if possible because it will allow you to keep a lower CG (center of gravity) and will generally be lighter. I made my own housing for my rear thrust fan, but I am sure there is stuff available online too.
windu34
Quantitatively, you want the product of the exit mass flow rate and the exit velocity of the air be as high as possible^ Ducted fans can be quite powerful, but controlling them consistently is usually difficult.
adi1008
antoine_ego asks: "What do you recommend to increase accuracy in mousetrap?"
JohnRichardsim
A sturdy chassis is crucial as is a method to adjust the device to travel in a straight path. The braking system is also important and you want a way to decelerate to reduce skid when your wingnut tightens up (or however your braking system might work). Definitely use a scope to aim, and have a reliable and repeatable attachment mechanism. Reducing and slip in the wheels will improve accuracy. Look for tires with a durometer rating between 30-50A ideally and make sure they do not wobble (ie rotate in a single plane when the axle is spun).
windu34
Ten asks: "Mission Possible, would using a voice recorder that uses a battery for the end task count against you for the one battery bonus?"
JohnRichardsim
Yes. One way I can think of getting around this is using an arduino mp3 shield and recording your voice using your phone, save the file to an SD card, and use the arduino to play the sound file through speakers (which must also be powered by the single battery).
windu34
enmu asks: "How does taping the threaded rod to fit the bearing affect the movement of the mousetrap, if it does?"
JohnRichardsim
I would imagine if it's not evenly taped, could cause the bearing to be slightly tilted and your wheels to wobble.
JasperKota
Since that is not a solid fit and there will be some amount of wiggle/play, it will decrease your accuracy. To what extent depends on how uniformly you applied the tape and how much room it has to move. While not the best solution, if you use thin painters/masking tape and wrap it tightly so that the threaded rod fits snugly and use cyanoacrylate to attach it permanently, I think that would yield pretty decent results.
windu34
raxu asks: "At my team there is a "Kit" problem where my teammates have little motivation beyond buying a kit. Any recommendation about how to motivate the team, and where to start building outside the kit?"
JohnRichardsim
Quite honestly, it takes plenty of motivation to get students to just buy the kit itself. Due to this, it can certainly seem like it's impossible to get up further. A common strategy to avoid this, however, is to set dates with "checks". This system, used in multiple teams, involves setting deadlines that leave plenty of time before the competition itself to assemble the kits, and not be left assembling them late at night before the competition. A good period is 2-3 weeks before the competition, just make sure to be firm with deadlines, and things should change in no time!
NeilMehta
Adding on to that, building on to the kit should really be after lots of testing is done (I am assuming you speak of heli). But for any kit, learn how it was put together (in the case of heli, Dave responds to emails and has great instructions) and then maybe tweak things that could better optimize scores.
Raleway_
As far as starting without the kit, I would recommend looking on google images and youtube for examples of devices. I started using 3D printing supplies and carbon fiber materials because my coach had those materials readily available, but it’s hard to define exactly where to start as far as using new materials. Just use whatever is available to you (wood, metal parts, 3d printing, etc) and use other peoples device designs for inspiration.
windu34
A kit is a great starting point but be wary that many teams may be using the same kit as you.
JasperKota
caesar asks: For Mousetrap Vehicle, "What material do you recommend for wheels?"
JohnRichardsim
I would try using small Banebot wheels since they have really good traction. With this though, try reducing the weight of the wheels as much as possible by possibly drilling holes in the wheels or stuff like that.
markuswso17
This depends on what you want to spend. I really like Banebot wheels which are made of some sort of silicon/rubber material (wish I knew more about that). If you have a low budget, soft balloons can work decently well, but I would definitely recommend actual wheels such as banebots over balloons.
windu34
jon asks: "For hovercraft, how do you deal with the levelness of the track at slow speeds?"
JohnRichardsim
I keep a level with me and try and adjust my thrust fan accordingly. Usually, using any math/calibration stuff for unlevel tracks hasn't been consistent for me so I end up having to improvise/experiment during the 8 minute device testing itself.
adi1008
My partner and I used the time of our first run and created a linear regression based off of our data we collected that gave us new settings (New resistance on our rheostat) that would usually get us pretty close to the target time. As for testing and gathering data, use levels and do your best. Your device should not have too big of a problem with static friction since the velocities this year are higher than last year.
windu34
KevinHao asks: "Mousetrap - Should I make the steering on the vehicle fixed or changeable?"
JohnRichardsim
Changeable. You need to be able to make very fine adjustments and the way you adjust steering doesn’t have to actually be a legitimate steering system such as EV last year. I used string a zipties in 2016 EV to literally bend the frame and adjust it to go straight before competition and practice. While this is definitely not a precise or quantitative method, it worked relatively well and is very light which is beneficial this year.
windu34
KevinHao asks: "Mousetrap - What's a better way to line up the vehicle other than a scope?"
JohnRichardsim
Since lasers are not allowed, there is no better way.
windu34
magic asks: "How many penny rolls is good for hovercraft at this point in the year?"
JohnRichardsim
All of them. Always aim for the absolute best. I can’t really speculate as to how many rolls you would need to medal at a given competition due to the TS.
windu34
You always go for the best- never settle for less :)
Raleway_
caeser asks: "How does the team mitigate the number of "things breaking before competition because of travel"?"
JohnRichardsim
This is very different between two main types of builds: most builds with a sturdy wooden frame (mission, roller coaster) are safer to carry. The problem comes in when you have events like Wright Stuff or Helicopters.
NeilMehta
If you're looking to transport something pretty fragile like wright stuff and helicopters I always put it it in the seat next to me, never in the storage area of the bus.
JasperKota
In addition, always keep duplicates! We like to keep about 3 models just in case, although 2 should be enough.
NeilMehta
As for my events (EV, Robot, non-balsa): design things for travel and build sturdy devices. If you have to, make cases. I built a case for Robot Arm and EV out of wood and always packed it tight with foam/packing materials.
windu34
Also find a good sized box (BJ's has free cardboard boxes!) and plastic grocery bags works well as cushioning (again for planes and helicopters).
JasperKota
Just line the interior for fragile builds, and then put that box in a box that also is a tight fit with bubble wrap lining and then duct tape it to a seat or something.
Raleway_
Be very very gentle, and remember that it can often be better to use softer materials, such as cotton balls to line the box.
NeilMehta
HelicoptersNJ2017NeverForget asks: "Which mousetrap reversing mechanism is the most optimal: the backwinding method or the double mousetrap method?"
JohnRichardsim
It’s hard for me to say since I haven’t built either, but intuitively, I think that the double mousetrap method would be superior because it would allow for you to change directions pretty quickly and the distance that the vehicle has to traverse is not very long. However, I would encourage experimenting with both if possible.
windu34
Ten asks: "Would using 2 pulleys chained together by a timing belt or something similar be allowed for a Mission Possible pulley system and would it count towards the mechanical advantage?"
JohnRichardsim
I think the answer here is no, but it’s hard for me to determine what exactly you are asking. A timing belt would not really work here, the pulleys are being operated by string and the lengths are changing. If you are referring to transferring the rotational motion of the pulley using a belt and the MA is being applied, then yes I feel a timing belt should be legal and score points for that task.
windu34
raxu asks: "Can you go over how to operate super glue? So far we superglued paper towel onto a table and a finger."
JohnRichardsim
Superglue is a MESS! The trick however, is that a little bit goes a long, long way. I'll be honest, I was in the same scenario as you a few days ago. In the case that a CA superglue gets stuck to your skin, nail polish remover (Contains acetone) should be enough to get it off. To avoid the scenario, try to use a glue with a thin tip, and stick to heavier glues over clear liquid glues. For something such as wood glue, the tips are a bit heavier, so it is useful to use something like a brush to apply, or a toothpick if the area of application is smaller.
NeilMehta
Seeing as I have super glue on my finger right now actually, not sure if I'm qualified but... make sure you have an old table cloth or something covering your work area so you don't ruin your tables and also have some kind of place to put whatever you’re using to apply the glue with, like a piece of paper or something. I recommend not to apply directly from the bottle because in many cases it causes you to put too much.
JasperKota
Just use a nice dropper and be careful :)
Raleway_
Abhyan asks: "For hovercraft, how do you recommend we make design modifications for the increased weight requirement? The new battery requirements and 9V max seem to limit us and our team is having difficulties with the build."
JohnRichardsim
For lift, your skirt design is very important. My design was able to support up to 4 to 5 kg even on a relatively discharged NIMH 7.2 Volt pack. Lift should definitely be achievable using a 7.2 NIMH pack and a blower fan (Mine was meant for 12VDC pumping mattresses and worked very well). As for propulsion, I agree that is going to be a challenge to get consistency from NIMH, but the speed should be achievable since its only 15 seconds with a smaller increase in distance. So basically, if you aren’t able to support the weight, look into a new skirt design.
windu34
Times New Roman asks: "What materials would you suggest for Thermo build this year"
JohnRichardsim
An example list of common insulator materials can be found on this wikipedia page: https://en.wikipedia.org/wiki/R-value_(insulation)#Example_values
JohnRichardsim
Note that some of those materials in the list are prohibited in the rules (see 3.a.)
JohnRichardsim
From what I've heard, it's hard to design the best device based on theoretical calculations alone; you have to do a lot of device testing using different materials to get the best device you can.
JohnRichardsim
Macgyver asks: "Do you guys have tips for someone who's building Mission Possible for the first time?"
JohnRichardsim
The most common error I've seen with mission is that people tend to dive in headfirst and work on multiple components at once. Mission possible is a difficult event mainly because of the many variables associated with all of the different part, so it is essential to make sure one part works before moving onto the next. In addition, keep it simple!
NeilMehta
TL;DR: prioritize reliability over potential points
NeilMehta
Reliability and neatness are extremely important. Make sure your device is neat and all the moving parts and mechanisms are reliable and sturdy.
windu34
caeser asks: "How important is researching about the device you're building? Should you allocate an hour? A few hours to a week?"
JohnRichardsim
This is extremely important. Many people think builders are just a bunch of apes hammering and gluing stuff together, but good builders thoroughly research their designs and understand all the theory.
windu34
tldr, sufficiently long till you really understand and can thoroughly defend your design to a judge
windu34
Especially for events like mission - theory is key!
NeilMehta
It's really important to research things before starting to build. You might find better options after starting to build, but can't change it because you've already built it.
JasperKota
^^
windu34
caeser asks: "When making a design and blueprint, should I get in-scale engineering paper? Or measure as I go?"
JohnRichardsim
I always designed my builds in CAD software (either Autodesk or Solidworks, but whatever you have works too). If just making sketches, making it to-scale isn’t super important.
windu34
Reminder: if you want to ensure that your build event question gets answered, please send it to Person by typing "/msg Person [message]" before 9 PM Eastern or 6 PM Pacific
JohnRichardsim
With something like helicopters or wright stuff it may be easier to make design to scale.
JasperKota
question from caeser: "When building, what are the standard supplies?"
NeilMehta
This varies heavily from event to event - but the most common universal components are glues and woods. For glue, events like Heli or Wright Stuff favor CA glues, as they use the least weight; however, for larger scale events (i.e. Mission), a regular wood glue works fine.
NeilMehta
The main types of wood used are balsa (lightweight) and basswood (stronger but heavier).
NeilMehta
For attaching different woods in larger scale events like mission, use screws and brackets.
windu34
It depends a lot on the type of build you're doing, but basic tools like xacto knives, razor blades, wire cutters pliers, drills always come in handy.
JasperKota
It is the builder's job to decide what is the most efficient for their device (for example, in WS, the main body will be built out of balsa, but hooks and struts can be made of heavier materials).
NeilMehta
Events like Battery Buggy, Mission Possible, etc. will also involve a lot of electrical components.
Unome
Different tools are optimal for different events, research your event.
JasperKota
MattChina asks: "For Hovercraft, do you know if we are allowed to use NiMH batteries?"
JohnRichardsim
Yes: backed up by the updated Battery policy: https://www.soinc.org/sites/default/files/uploaded_files/Science_Olympiad_Battery_Policy10_18_17.pdf
Unome
NIMH is allowed. LiPO and Lead-acid is not.
windu34
enmu asks: "So if my parts don't arrive on time (carbon fiber, banebots/hubs, bearings) what would be good, cheap alternatives for the frame/wheels/bearings that i would be able to buy at the store (ex. home depot)?"
JohnRichardsim
Mentioned earlier by Windu, CD's with balloons with traction is a decent alternative for wheels.
JasperKota
You could try to use kit parts such as Tetrix or Vex parts to throw something together for competition if you have that available. If not, try to emulate kit materials and use bass wood, threaded rods with bushings, etc
windu34
Ten asks: "Very new to the event--any tips for designing chemical components and obtaining chemicals for Mission Possible?"
JohnRichardsim
2017-11-25 18:03:03] * JohnRichardsim set the topic to We are no longer accepting new questions || Disclaimer: responses to any questions about rules shouldn't be treated as official opinions or clarifications and event supervisors may have differing opinions
2017-11-25 18:03:03] * JohnRichardsim set the topic to We are no longer accepting new questions || Disclaimer: responses to any questions about rules shouldn't be treated as official opinions or clarifications and event supervisors may have differing opinions
Try talking to your chemistry teacher at school for chemicals.
windu34
Some useful chemicals, like the pellets in cold packs, are available off the shelf too.
DarkSabre
Ten asks: "Another one about Mission Possible, any idea on how to flip a coin consistently?"
JohnRichardsim
For speed of reaction think about particulate size or concentration or agitation.
DarkSabre
Coin flip: I recall seeing a post on the forums about how one could place it on the top of the end of a rotating beam, and move the beam 135 degrees, so the coin falls off upside down.
Unome
(maybe that previous question was from Ten? Sorry, we're having slight technical difficulties.)
JohnRichardsim
Find a way to place the penny consistently by using a physical object to line it up (don’t try to use a marker or pencil). With the flipping mechanism, if it’s an arm that hits the penny, make sure it has a wide contact point to the penny so equal force is place on the penny each time. Minimize any play in the moving component.
windu34
Okay, THIS one is from bmd234: "What do you think the best way to space out build events are? (How long for research, how long for your first prototype, etc.)"
JohnRichardsim
So this depends on what your timeline is, but I’ll give an example. Say you are preparing for MIT from scratch (January 20th) starting on October 1st, I would take about 2 weeks to design everything on paper and understand all the concepts, take another week to CAD everything in some software, obtain all the parts you need in that following week so now you’re at November 1st. Then I would take 2 weeks to build your device, 2 weeks to troubleshoot (basically gathering data, but realizing mistakes in your build structure/quality and fixing/compensating for them so that any new data you would take would be consistent), and then spend the remaining time gathering data/testing and fine tuning. I always approached my builds from the prospective that the only thing that mattered was nationals so my timeline was very different. I would accept being completely unprepared for early invitationals and would throw together a backup build in about a week or two before competition to take to them while I continued to design or CAD my actual design. Of course this leads to poor results early on, but it can lead to fantastic results later on so it really depends on your end goal with your device.
windu34
Well, that concludes our roundtable tonight. If we were unable to answer your question during this session, feel free to ask on the forums at https://scioly.org/forums/
JohnRichardsim
Thank you all for coming and thanks to all of our panelists for the night. Stay tuned for an announcement for the Study Event Roundtable!
JohnRichardsim