riley elwood asked "can you make a rubber band powered car out of 4 toothpicks 2 straws and 4 bottle caps". I was going to add it to my list to do later but I couldn't resist making it now. The video is virtually real time without any speeded up sections so the total build time was only about 15 minutes.
The back toothpick simply has a very short piece of toothpick glued to it so it forms a hook to hold the band as you turn the axle.
Measurements: How long is your straw? You need holes for the axles to go through and they need to be the same position on both straws or you car will not go straight. You need holes in both straws for the cross-members to go through and they need to be the same position on both straws or the car chassis will not be straight. Other than that you can put the holes anywhere you like on the straws. Probably as near to the end of the straw as you dare without weakening the straw. If you watch the video carefully you can see I am using a ruler that is marked in centimetres and it looks like I am probably marking the holes about one centimetre from the end and then the next hole about one centimeter from that.
Making the holes might be an issue. Melting the plastic is better than trying to drill it or push a sharp spike through but it can be done. Using a hot wire or soldering iron may be a safety problem but you get a stronger hole. In the straws it is important that the holes for the cross members are a tight fit and the holes for the axles are very loose. The holes in the wheels need to be a very tight fit.
"Does adding the clay make the car move further? If so, what is the science behind it?"
The answer was already explained in the video. The car was too light so the wheels lacked grip and slipped on the floor, spinning round without moving forwards. Adding the clay to the wheels made them heavier so they had more grip, stopping them slipping, so they could drive the car forwards.
The science is about friction.
2 drinking straws
4 bottle caps
rubber bands or loom bands
Modelling Clay for extra weight
Hot Glue Gun - If you get the relevant holes nice and tight you probably don't need hot glue but I always like to use it.
Soldering iron - At 03:45
I explain I am using my soldering iron to melt the holes. You could just use a sharp nail or a drill but using the soldering iron means there is no chance of the plastic splitting, you need a steady hand to do it.
Filmed using FujiFilm FinePix S4800
Edited using Serif MoviePlus Starter Edition
Snowman plays247 asked "What other types of materials can you use other than straws?". I have split the reply video over 4 episodes and placed it in it's own playlist. www.youtube.com/playlist
Connecting rubber bands youtu.be/EbYuhdwknbs
Connecting the band to the axle youtu.be/0wPYxloUFJQ
Making the CD wheels youtu.be/ZRrjBuWfmrM
CD Wheels with Cardboard Hubs youtu.be/Js1rtn2IGTE
Putting rubber tyres on CDs youtu.be/ZnuPnveCbxs
Here is a selection of related playlists
Rubber Band Power Cars www.youtube.com/playlist
Rubber Band Power playlist www.youtube.com/playlist
Brakes on Rubber Band Cars playlist www.youtube.com/playlist
Carrying Dropping Pushing Pulling Stopping playlist www.youtube.com/playlist
Rubber Band Wikipedia en.wikipedia.org/wiki/Rubber_band
Size 64 rubber band measure 3 1/2"x 1/4"x 1/32" or 89mm x 6mm
Other People's Rubber Band Cars www.youtube.com/playlist
My Channel page www.youtube.com/user/GrandadIsAnOldMan
Oldest videos www.youtube.com/user/GrandadIsAnOldMan/videos
Most Popular www.youtube.com/user/GrandadIsAnOldMan/videos
Newest videos www.youtube.com/user/GrandadIsAnOldMan/videos
I have thousands of videos on YouTube, to find one try my search guides youtu.be/ceBSOoOHcgw
My "GrandadsOtherChannel" channel is generally where I will host the videos that give extra detail or longer versions of the videos I post on my main channel www.youtube.com/channel/UC2mp_L8RoxMyw3ewwSecZ6Q
Merchandise - Check both of these links if you are interested as the prices will vary and the shipping charges will be different.