Thanks again to everyone who helped make today’s booth at the Robotics Expo a huge success again this year. Booth volunteers included Ben, Don, Mike, Michael, Brandon, Nick and Jared, with material support from Patrick, Sarah, Eric, Dave and Katlynn. [Apologies in advance if I missed anyone].
The subject is a potassium sodium tartrate (Rochelle salt) crystal mounted in a brass holder, with a copper contact wire for detecting the crystal's piezoelectric properties. From the perspective of the camera, this setup looks like this:
OMG’s innaugeral FirLumber Rally was a great success, with 17 cars competing. Official results will be posted shortly, but in summary, Dave’s electric cheater was the fastest, Eric’s elephant was the most creative, and Nate’s car was the least effort to build. Additionally, Dan’s kids’ cars were the fastest among the Squares.
Thanks to all who took part in our Trebuchet Contest! We had perfect weather and all involved had a great time. With nine people competing on six teams, we saw a wide variety of designs and lots of experimentation.
Each team fired three shots, which were analyzed for efficiency and for accuracy. The efficiency score is calculated as the length of the best shot divided by the mass of the counterweight – to discourage anyone from using small cars as counterweight and hurling the projectiles all the way to Dodge Street. The accuracy score is the standard deviation of the three shots. To combine these into a final score, each category was normalized to 5 points for the best team in that area, with proportionally fewer points going to every other team. As a result, the best possible score is ten points, which would only be awarded to a team winning both categories.
|Rank||Team||Efficiency (ft/lb)||Accuracy (St Dev)||Score|
|4th||Kyle and his Dad||7.9||18.3||4.0|
|6th||Don, Stephanie, and Sarah||6.2||31.2||3.2|
Ben, competing with a trebuchet constructed years before and “conveniently” fitting the contest requirements, had the longest throw of the day at 214 feet, but the use of a rather large counterweight dropped his efficiency to mid-pack, though not nearly low enough to offset his astonishing repeatability and accuracy.
Dave, winner of the “Least Effort Possible” award which nobody has bothered to create, gave a spectacular performance, particularly considering that his machine was constructed and tested in under fifteen minutes.
Eric nearly forfeited the contest after some mysterious last-minute bugs, but came back with a very solid 94-foot throw. Unfortunately, with two of his three shots launching backwards, his accuracy score reminded everyone to stand well to one side of a firing trebuchet.
Kyle and his Dad arrived with the only machine too large to be assembled indoors. Installing a competitive amount of counterweight earned them a respectable score, but before and after the contest, their 50-lb maximum capacity gave the neighbors something to think about.
Kevin competed with the only machine requiring three hands to safely load, and was also the only entrant to attempt self-amputation during testing. Despite this, the device proved acceptably reliable and fired many shots without incident.
Don, Stephanie, and Sarah may have earned the lowest score, but they were also the only team to compete with no prior testing. Their trebuchet was not completed until several minutes after the start of check-in and was immediately put to the test with none of the tinkering and tweaking afforded by the other teams.
Once again, a huge thanks to everyone who took part in this contest! We know it was the most difficult challenge we’ve yet conceived, and everyone who took part worked extremely hard to make the firing line yesterday. We promise the next event will carry wider appeal – more on that in the coming weeks.
- For Opening New Frontiers – Jay Hannah and Dave Knaack
- For Operational Excellence – Eric Kaplan
As stated at the meeting, the categories for these awards are entirely arbitrary and subject to change in future years; Also, we estimate that this prize is roughly 1 million times easier to win than a Nobel Prize, and the cash award has been scaled accordingly.
As for the award for Operational Excellence, this prize is awarded to Eric Kaplan for consistent attention to “things that need done”; He’s involved in everything from staffing booths to designing marketing material and furniture for the space. Furthermore, he successfully facilitated the Makery’s relocation to our new home.
Again, congratulations to all our 2013 winners.
This is your chance to build the best miniature siege engine in Omaha. Work by yourself or in a small group to make the best golf-ball*-throwing device you can imagine. We will then compete for range and accuracy to crown a champion. The contest will take place at the Makery on September 21st.
Although the competition is called “Trebuchet Contest,” your device does not need to look like something out of the middle ages. You can use any design, any materials, any construction techniques, and in fact any launch techniques you’d like. We want to keep things interesting, so the rules for this contest are very lenient:
The energy used to launch the projectile may come only from the gravitational potential energy of a mass falling no greater than 16 vertical inches. No explosives, precompressed springs, compressed gasses, batteries, or any other sources of energy. Gravity only. However, you can use all those things as intermediate steps if you’d like – if you use gravity to compress a spring, or use electronic timing to coordinate the firing, that’s just good Maker spirit. Just be prepared to prove that you’re not contributing any extra energy to the projectile.
Your siege engine requires a remote triggering mechanism. Mechanical, electronic, whatever. You need to be ten feet from the firing position during your shots, and away from the most likely misfire direction (for example, on a standard trebuchet you need to be off to the side, out of the plane of the arm). We want to keep things safe.
You cannot aerodynamically assist the projectile in any way. If you need wadding to seal the projectile in the barrel of your gravity-charged pneumatic cannon, that’s fine. If you want to use a sling which stays attached to the projectile instead of the trebuchet, well, you’re the one who thinks it’ll be competitive to throw more weight than anyone else. But whatever you do, the projectile has to take a ballistic trajectory once it leaves your machine.
We’re trying to keep things interesting and attract the widest range of designs by keeping the rules loose. Please don’t abuse this privilege – nobody wants to read a ten-page rule book covering every possible situation. Tech inspection is going to have a “spirit of the rules” philosophy, and you should keep that in mind while working on your design. If you have a creative idea or think you’ve found a loophole in the rules, please bring it up with Ben as soon as possible. Most likely it will be allowed, but if you show up on competition day with something ridiculous, having never discussed it with the organizers, you might find yourself disqualified. We promise flexibility and absolute discretion – if we allow your cunning plan, its secret will be safe, and we promise not to steal it for our own designs.
*Golf balls make ideal trebuchet projectiles. Unfortunately, they’re a bit dangerous and bouncy. To dramatically increase the chances of scoring each shot by ensuring we can actually find each projectile, we won’t be using golf balls. Competition projectiles will be approximately equal in size and exactly equal in mass to a golf ball. Projectiles will be supplied for scored shots, although you may test with anything you like.
Competitions and Scoring:
The exact equations used for scoring will be revealed the day of competition, to prevent any rules-lawyering and to allow us more time to perfect them.
You will be scored on your ability to efficiently throw the projectile as far as you can. The mass of your power weight will be taken into account, so if you decide to increase performance with extra weight, make sure you’re getting a proportional gain in range.
You will be scored on your ability to hit a predetermined target at a distance of your choosing. The main goal is accuracy, but your chosen range will also affect your score – a 10-foot miss from 100 feet isn’t as impressive as a 10-foot miss at 200 feet.
Mark your calendars, the Omaha Maker Group’s 3rd anniversary (birthday?) get-together is Tuesday, August 20th. As usual, doors open by 6pm. There’ll be food and beverages and even some awards.