Gravity Vehicle C

[HanDHun]

http://www.youtube.com/watch?v=EVkRHTIW ... e=youtu.be

heres a video i made to show the difference between a brachistochrone curve and a normal ramp. Hope this is enlightening.

Which ramp turned out to produce the higher exit velocity? I noticed there was a separation when both clips were played at the same time.
Also, the two ramps were of different material, would that affect the vehicle speed?

[HanDHun]

a suggestion as far as reducing recoil for the string method for breaking, its kind of tedious but it works well so far (only tested a few times though). if you put a spool on each axel and put spokes on the end of one, you can attach a two dowels connected to each other by a hinge to the chassis near the end with the spokes. the spokes wil slap one of the dowels while going forward but if it tries to go back ward it will be stopped. when i used it it had absolutely no recoil, but when it goes different distances it may have some but it would be limited. i hope this helps if more clarification is needed i can post a picture.

Looking at the picture, it does seem like that's incredibly tedious... How do you keep the masking tape strong enough to keep the two dowels from separating from each other without entangling the spokes?

[sk17]

You shave some wood of the side with a knife to make them flat then put 3 or 4 strips of tape on the flat end then warp tape around each individual segment that part probably took me only like 10 min

[sj]

Its of average mass not super-light not super-massive but the interesting thing is the speed of the car is not constant it takes about 4.5 seconds to go to 10 meters so im thinking it may not be quite as astounding as it may have initially seemed, though in my opinion the most remarkable thing was the accuracy to the point.

[illusionist]

Where have you guys been getting your bearings, and how much do they cost? I found a few online, but they all cost about $5-6 per bearing...

[Littleboy]

Inside bike pedals there are bearings. Most have good bearings. You can probably get some used pedals from a bike shop for little to no cost. They don't need them anymore so you can get tons of them for cheap. Each pedal probably has around 10-15.

How does the time increase by that much for only 2.5 meters? Is it super fast in the beggining but gets incredibly slow towards the end to the point it barely moves?

[sj]

We spent $10 per bearing from McMaster Carr, but I believe the model we bought has been discontinued.

Well for us I think the problem was actually that the floor in his basement may have started to slope upwards around the 8 meter mark or so which may have impacted our time. Another thing that may have happend is that the kid who timed our run may have stopeed the watch earlier than he should have. Or it might be a combination of these two factors. I can post more definitive time results once we run our vehicle on a more valid surface like out gym floor.

[fishman100]

Where have you guys been getting your bearings, and how much do they cost? I found a few online, but they all cost about $5-6 per bearing...

I bought my bearings at Sports Authority; they were from BSB and the package included 16, I think. Got it for ~$25.

[chalker]

Another thing that may have happend is that the kid who timed our run may have stopeed the watch earlier than he should have.

Keep in mind that typical human reaction time is in the tenths of a second range, which is why the rules insist on 3 independent timers being used for each run. I've seen a lot of good suggestions about trying to replicate flooring and such during practice runs, but haven't seen anyone discuss the human timer aspect of it, which can also have a big impact.

[illusionist]

Each pedal probably has around 10-15.

...what?