Sahil Segal from India asked:
What should be the perfect gear ratio for the buggy that could provide torque and speed?
Answer:We learned to need a useful seat position and an average rotating speed of ca. 1/sec (at the pedal). So our students taked a seat at an health club and detect their average rotating speed by best performance and under big stress. Then they were reading the "Rules and Penelitries" of NASA and started the following process of calculations. One student used this theme for his A-level exam.
Steps to make the dimensions for the gears:
This screenshot is from our real "Winning Run" this year. The GPS-calculated lines are in the yellow field. You see the speed, absolute altitude and acceleration. The real gauged G´s by 3D-G-Sensoric are in the blue field. So we can understand the kinematic and stability.
What should be the perfect gear ratio for the buggy that could provide torque and speed?
Answer:We learned to need a useful seat position and an average rotating speed of ca. 1/sec (at the pedal). So our students taked a seat at an health club and detect their average rotating speed by best performance and under big stress. Then they were reading the "Rules and Penelitries" of NASA and started the following process of calculations. One student used this theme for his A-level exam.
Kinematic of the german Moonbuggy 2009 (exam by Thommy)
Steps to make the dimensions for the gears:
> use anytime the dual unit system (US- and SI-units), so you will locate mistakes ASAP
- calculate the length of the course with the best time and you see your average speed to take a winning team,
- Calculate: How many turns of your wheels you need to finish the lengh of the course.
- Now you must calculate the turns with the average speed into: average turns per second of your wheels
- Now calculate the ratio beetween the average speed of your pedal with the average speed you need on your wheel.
- This ratio is the base of your Moonbuggy.
- But: the Moonbuggy will not drive a constant speed, so you must see the performance beetween the obstacles.
- Your Buggy will stop 14 times at an obstacle, beetween the obstacles it must be faster to equal the average course speed
(it is like a rocket: calculated course ./. actual course = difference to correct the main engines and directions)
- So your gears must work on a tolerance (+/-): slow powerful / and fast
- Now you must calculate with a lot of accelerations (+ - G, m/s² or ft/s²)
- testing, testing, testing and anytime again! (this is good for the health of the team)
The calculations with the different accelerations needs our attention every year. See the attached telemetry analysis of our Moonbuggy. These are all datas from our "winning team-run" in April 10, 2010. This is a self written software for our Moonbuggy (after using a self made RC-telemetry on the Moonbuggy). It analyze the GPS-datas and a 3D-G-sensor and sending it by radiopackages from the Moonbuggy to a Mission Control Center (1 packet per two seconds).
- calculate the length of the course with the best time and you see your average speed to take a winning team,
- Calculate: How many turns of your wheels you need to finish the lengh of the course.
- Now you must calculate the turns with the average speed into: average turns per second of your wheels
- Now calculate the ratio beetween the average speed of your pedal with the average speed you need on your wheel.
- This ratio is the base of your Moonbuggy.
- But: the Moonbuggy will not drive a constant speed, so you must see the performance beetween the obstacles.
- Your Buggy will stop 14 times at an obstacle, beetween the obstacles it must be faster to equal the average course speed
(it is like a rocket: calculated course ./. actual course = difference to correct the main engines and directions)
- So your gears must work on a tolerance (+/-): slow powerful / and fast
- Now you must calculate with a lot of accelerations (+ - G, m/s² or ft/s²)
- testing, testing, testing and anytime again! (this is good for the health of the team)
The calculations with the different accelerations needs our attention every year. See the attached telemetry analysis of our Moonbuggy. These are all datas from our "winning team-run" in April 10, 2010. This is a self written software for our Moonbuggy (after using a self made RC-telemetry on the Moonbuggy). It analyze the GPS-datas and a 3D-G-sensor and sending it by radiopackages from the Moonbuggy to a Mission Control Center (1 packet per two seconds).
This screenshot is from our real "Winning Run" this year. The GPS-calculated lines are in the yellow field. You see the speed, absolute altitude and acceleration. The real gauged G´s by 3D-G-Sensoric are in the blue field. So we can understand the kinematic and stability.
technical facts of the winning run in 2010, by Team Germany #7:
- average speed: 7,8 mph (12,48 km/h)
- max. speed: 15 mph (24,08 km/h)
- max. acceleration: +8,15 ft/s² and -10,12 ft/s² (-3m/s² / +11m/s²)
- max. torque at the power axis: 255 lbf ft (245,4 Nm)
- total power: 115,6 kW
technical design and calculations for 2010, by Team Germany #7:
Our Moonbuggy has + and -7 speeds around the average maximum speed. The main gears are two 14-speed "Rohloff Speedhub 500", see at http://www.rohloff.de/. There are two more gears inside of the pedals, "Schlumpf Highspeed-drive" from http://www.schlumpf.ch/. The differential gear (reductor) is totally salf made. See at the archive.
by Ralf Heckel,
supervisor for multinational Moonbuggy Teams
International Space Education Institute
- average speed: 7,8 mph (12,48 km/h)
- max. speed: 15 mph (24,08 km/h)
- max. acceleration: +8,15 ft/s² and -10,12 ft/s² (-3m/s² / +11m/s²)
- max. torque at the power axis: 255 lbf ft (245,4 Nm)
- total power: 115,6 kW
technical design and calculations for 2010, by Team Germany #7:
by Ralf Heckel,
supervisor for multinational Moonbuggy Teams
International Space Education Institute
