Search found 151 matches
- Fri Jan 27, 2012 11:35 pm
- Forum: Car & Semi-Truck Construction
- Topic: How thin of a car is ok
- Replies: 33
- Views: 40647
Re: How thin of a car is ok
I made sure I had the right block with the proper grain pattern to minimize warping (heating the block in the oven probably didn't hurt either). I wonder if baking the block is a good thing, or risky thing. Good, if it helps the car preserve its intended unwarped dimensions for a year or more. Bad,...
- Fri Jan 27, 2012 8:33 am
- Forum: Car & Semi-Truck Photos
- Topic: Turtle Race
- Replies: 13
- Views: 15023
Re: Turtle Race
If wheel mods are allowed, it would be good to put most of the car's metal weight into a pair of the BSA wheels, just inside the tread. That would divert a third or so of the car's kinetic energy into the wheels' angular momentum, where it then sustains the slowed forward motion despite air drag. Th...
- Thu Jan 26, 2012 12:43 pm
- Forum: Car & Semi-Truck Construction
- Topic: Why the death wiggle on some runs and not on others?
- Replies: 8
- Views: 9084
Re: Why the death wiggle on some runs and not on others?
I wonder how to build a car that gets maximum wiggles, even on the ramp, and yet finishes.
That could be a fun variant on turtle cars.
That could be a fun variant on turtle cars.
- Thu Jan 26, 2012 9:30 am
- Forum: Car & Semi-Truck Construction
- Topic: How thin of a car is ok
- Replies: 33
- Views: 40647
Re: How thin of a car is ok
At low speed, wouldn't creating turbulance (like a golf ball surface) be better? Not that I or my 8 year old have the patience to dimple a pwd car. But I bet one of you would be up up the task :) No, the golf ball effect is really for 1 directional air flow, not effected by the ground but open air,...
- Thu Jan 26, 2012 8:28 am
- Forum: Do-It-Yourself
- Topic: Calculate car speed.
- Replies: 29
- Views: 48222
Re: Calculate car speed.
Two sensors placed a short distance apart could do the job and would be car length insensitive. Place such a system at the finish line and you get the finish speed. Place such a system at a point along the track where max speed is expected and you get an approximation of the max speed. On a typical...
- Wed Jan 25, 2012 12:58 pm
- Forum: General Coordinator Topics
- Topic: Why this Rule - Wheels directly across from each other
- Replies: 13
- Views: 14989
Re: Why this Rule - Wheels directly across from each other
I think it would be safer to stagger the front wheels than the back wheels, given that most of the weight is on the back. If your goal in staggering is to temporarily lift a wheel, then you are correct. However, I think that if you look at the energy equations, you find no value unless you are able...
- Wed Jan 25, 2012 1:41 am
- Forum: Car & Semi-Truck Construction
- Topic: How thin of a car is ok
- Replies: 33
- Views: 40647
Re: How thin of a car is ok
Making the front thinner and lighter means that the weighted back end then needs to be heavier and thicker, so air drag is increased by the thin front end. A thin or hollowed front end does help with moving the com rearward, which helps the total energy available. Does the changed com provide enoug...
- Wed Jan 25, 2012 12:09 am
- Forum: Car & Semi-Truck Construction
- Topic: How thin of a car is ok
- Replies: 33
- Views: 40647
Re: How thin of a car is ok
Now, since the weight of the front end plays a disproportionate role in the location of the CM, reducing the front end weight allows less extreme location of the CM of the added rear end mass, which, in turn, allows that rear end mass to be flattened out with its CM moved a bit forward. Thanks! So ...
- Wed Jan 25, 2012 12:03 am
- Forum: Car & Semi-Truck Construction
- Topic: How thin of a car is ok
- Replies: 33
- Views: 40647
Re: How thin of a car is ok
I definitely need a portable wind tunnel for my garage, but first I need another garage to hold a wind tunnel. I'm jealous too!! I tried to find some open-source wind tunnel sim software that was simple enough to understand, to run a 2-D car profile, or some spinning wheels. Didn't find anything I ...
- Tue Jan 24, 2012 8:22 am
- Forum: General Coordinator Topics
- Topic: Why this Rule - Wheels directly across from each other
- Replies: 13
- Views: 14989
Re: Why this Rule - Wheels directly across from each other
Our pack requires use of the pre-cut axle slots, and 4 wheels touching, and no camber. So I've not studied RR and other advanced designs. But now we're going on to the district race with looser rules, and there is no rule against building an entirely new car. District says 4 wheels touching the trac...
- Tue Jan 24, 2012 12:44 am
- Forum: Car & Semi-Truck Construction
- Topic: How thin of a car is ok
- Replies: 33
- Views: 40647
Re: How thin of a car is ok
Someone please remind me: What's the point of very thin car bodies, or hollowed-out bodies, other than for exotic looks? The thin front end does not help with air drag. Making the front thinner and lighter means that the weighted back end then needs to be heavier and thicker, so air drag is increase...
- Tue Jan 24, 2012 12:23 am
- Forum: Car & Semi-Truck Photos
- Topic: Angry Birds
- Replies: 4
- Views: 7216
Re: Angry Birds
how did you anchor the sheet into the base? Did you cut a groove... then anchor with... epoxy? Yes, groove, with a contact cement. In the ghost pirate ship, it was easy to cut an appropriate-width groove into the balsa wood superstructure with a coping saw, before gluing the balsa onto the pinewood...
- Sun Jan 22, 2012 7:01 pm
- Forum: Car & Semi-Truck Photos
- Topic: Angry Birds
- Replies: 4
- Views: 7216
Angry Birds
Angry Birds won our pack today in a field of 70 cars, and was also a crowd favorite for being so distinctive and easy to follow in a very crowded hall: http://i39.tinypic.com/besehe.jpg My son is a Wolf; this is our third year of competing. Last year, we played with using plastic sheets to decorate ...
- Wed Jan 18, 2012 10:06 pm
- Forum: Car & Semi-Truck Photos
- Topic: Inception Car
- Replies: 17
- Views: 14679
Re: Inception Car
That is so neat, on so many levels!!
- Fri Jan 13, 2012 11:39 pm
- Forum: Car & Semi-Truck Construction
- Topic: Micro Vibration & a little more.
- Replies: 12
- Views: 9199
Re: Micro Vibration & a little more.
But, what it seems you need is to dampen in the vertical and stay stiff in the horizontal. "Grandpa's" flex chassis cars were motivated by his desire to cut down on noisy clatter on rough wooden tracks. He reasoned that the energy from that noise must be getting subtracted from the car's ...