Show All ItemsThese instructions demonstrate how to build an inexpensive simple Soap Box Derby Car. You should be able to build this car for about $50. Study this pictures and it will make your build easier. You may need to refer to these later if you have questions.Step 1: Exploded View RefrenceShow All ItemsRefer to these drawings if you have questions or need more clarification. It shows all the components that are in the assembly.« PreviousNext »View All Steps DownloadEdit ArticleHow to Make a Gravity Racer Two Methods:Design It Yourself, For FunBuy It For Official CompetitionCommunity Q&A A gravity racer, also called a hill trolley in Australia, is a motorless vehicle usually made of wood and used for competition racing. To steer it you have to use both feet and both hands at the same time. And of course you need a hill. The best hills are those that are not too steep and will let you ride for a long distance. Gather the needed materials. Cut the chassis plank to size.
This plank is the longest and will support the rear axle and seat at one end and the steering axle plank at the other end. The length will depend on your height. Cars are typically between 48 and 72 inches (120 to 200 cm) in length. The width will depend on the width of your bottom. Cars are typically 24 to 36 inches (60 to 100 cm) wide. Cut the axle planks to length.Drill a hole through the front end of the chassis and the middle of the front axle plank to make the pivot point for the steering plank. Fix the steering plank to the chassis plank Using the bolt. Attach the rear axle plank. Fix the axle bars to the axle planks.Drill a hole through the chassis behind the left and right sides of the steering plank, and slip the rope ends through. Attach to the steering plank near the left and right ends of the plank for maximum efficiency. Make the rope loop a comfortable length for the driver when he is seated. Slide the wheels onto the axles and secure them.
Have fun driving your gravity racer! Determine your racing division. The AASBD (All-American Soap Box Derby) organization has specific requirements and limitations that you and your gravity racer will need to meet. The Stock Division, designed for participants aged 7 to 13. The combined weight of car and driver may not exceed 200 pounds. The Super Stock Division is open to participants between the ages of 10 and 17, and the combined weight of car and driver not to exceed 240 pounds. The Masters Division is open to participants between the ages of 10 and 17. Car and driver may not exceed 255 pounds.All competition kits must be purchased through the AASBD. They are available online at here. The main thing is to align the axles because this will give you a lot more of stability. Be careful with the wheels, check that they are properly aligned. A hill trolley at speed can chuck you off and forever change your life. Wear a helmet, stay off busy streets and enjoy the experience.
By limiting the turn radius, you will minimize the chance of flipping your car. These are the most active places in America How to make a small bathroom feel bigger Key players in the Trump-Russia controversy Svechnikov gets SO winner in debut, Red Wings beat Senators AL champion Indians rally in 9th, win opener 8-5 at Texas Maple Leafs beat Sabres 4-2, close in on playoff spot Keuchel, Correa lead Astros over Mariners 3-0Perhaps the most influential topic in Bicycle Quarterly has been our research on the resistance of tires, first published in Vol 5, No. 1 (above). It is not a coincidence that 5 years after that issue was published, professional racers are adopting wider tires and lower pressures. How did all this come about? My research started after I read a big test of racing tires in the German magazine TOUR in late 2005 (below). As part of their testing, TOUR measured the rolling resistance on a steel drum in a lab setting. They found that the “fastest” tires had half the resistance as the slowest.
In real-life terms during a ten-kilometer time trial, the slowest tire (Continental Grand Prix 3000) would take 34 seconds longer than the fastest (a hand-made clincher with a cotton casing). TOUR noted this but did not critically evaluate the relevance of their results: 34 seconds in a short time trial is the difference between winning and 20th place. Most of us don’t spend much time at “time trial” speeds, where wind resistance predominates, so I did a quick calculation to see what this meant for real-world riders. I found that the differences were even more significant. Furthermore, TOUR tested only high-end racing tires. What about the wider tires most of us used? Were we giving up significant speed? We had to find out! The first thing to check was whether we could replicate TOUR’s results on real roads. We thought of a variety of tests, and concluded that a rolldown test had the most promise. Mark Vande Kamp suggested an old soapbox derby track that was perfect: It started steep and then gradually changed to a very gentle slope.
The first step was to get two sets of tires that TOUR had tested: The Deda Tre Giro d’Italia were the fastest in the test, and the Continental Ultra Gatorskins were among the slower tires. On a calm morning, we headed to the soapbox track. Each of us had mounted one of the sets of tires on our bikes. I rolled down the slope while Mark timed me. Then we switched wheels, so I could roll down with the second set of tires, on the same bike. We repeated this several times, and the results were clear: The Deda tires were significantly faster than the Continentals, just as TOUR had predicted. The next step was to gather all the tires we wanted to test. It was a long list, and we eventually pared it down to 18 tire models. (We later tested additional tires.) To make the testing session more time efficient, we borrowed as many wheels as we could find, so we did not have to mount tires between tests. Then we waited for a perfectly calm day. In Seattle, this usually happens when the weather changes.
During sunny days, the wind blows from the north, whereas it switches to the south on rainy days. In between, there are hours of perfect calm. From riding many randonneur brevets, we also knew that around sunrise, there was the greatest chance of no wind. Finally, a day came with a promising weather forecast. Long before dawn, we loaded up two Burley trailers stacked high with wheels, a floor pump, clipboards and everything else we needed. Then we started our testing. Mark rode up the hill. He held onto a stepladder on the start line, so he would smoothly roll down the hill without wobbling or having to clip into the pedals. He used the same position during each roll-down: hands on the hoods, elbows locked. (We later confirmed in the wind tunnel that this position can be maintained with great consistency.) Two timekeepers recorded Mark’s time in the lower section of the run. We ran each tire/pressure combination three times to see how consistent our data was. We also ran the same tires on different wheels to check whether the wheels influenced the results.
We tested and tested all morning. Different tires, the same tires in different widths, the same tires at different pressures. Clinchers, tubulars, racing tires, touring tires, new tires and well-worn tires with thin tread. We tested the same baseline tire three times during our test session – first, in the middle and last – to see whether conditions had changed. We were lucky: the morning was completely calm. It also was overcast, so temperatures did not change. (We later found that temperature greatly affects the rolling resistance of tires.) One morning was not enough to complete our testing, so we spent many more days on the test track. Sometimes we went out at 4:30 a.m. only to have a light wind spring up. All we could do was go home and hope for better luck next time. At the end, we had pages and pages of measurements that we formatted for analysis. During our analysis, we found some interesting results: One important question was still open: Did the results represent real differences in tire performance, or was there too much noise in the data?
After all, even slight changes in rider position, a tiny gust of wind, or other factors might influence the results. To check this, Mark, who has a Ph.D. with a Minor in Statistics, did a sophisticated statistical analysis. He found that our results were “statistically significant.” (Basically, he compared the data from the three runs of the same tire with the data from different tires. The variations between runs with the same tire were much smaller than the variations between different tires.) This means we really did measure differences in tire performance. (Many studies skip this step, but it’s crucially important.) Our research had profound implications: Like most research that calls into question long-held beliefs, our findings first met with much skepticism, but over the years, they have become widely accepted. We used our research to help Grand Bois design supple, wide tires that offer more comfort and better performance than most other tires. Switching to these new tires, my times in randonneur brevets decreased significantly.
(I had been riding some of the slower tires in our test!) In addition, I no longer had a hard time keeping up in pacelines. (In a paceline, the air resistance is significantly reduced by drafting, and most of the resistance you have to overcome is rolling resistance.) Today, even professional racers no longer worry about tire pressure. Their tires now are wider and run at lower pressures than those of most “weekend warriors.” And for the rest of us, this research has made it possible to build bikes with comfortable 42 mm tires that are as fast as racing bikes. There still are some questions about tires that remain to be answered: whether clinchers truly are faster than tubulars; at what point the advantages of wider tires turn into disadvantages (it is unlikely that a 100 mm-wide tire rolls faster than a 50 mm-wide one), and whether tire deflection due to pedaling causes additional resistance when running very low pressures (in our tests, the rider coasted). We have been doing more research, and will report on it in future issues of Bicycle Quarterly.