Search found 149 matches

by Duane
Sat Jan 28, 2012 12:35 am
Forum: Car & Semi-Truck Construction
Topic: How thin of a car is ok
Replies: 33
Views: 5131

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,...
by Duane
Fri Jan 27, 2012 9:33 am
Forum: Car & Semi-Truck Photos
Topic: Turtle Race
Replies: 13
Views: 2999

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...
by Duane
Thu Jan 26, 2012 1:43 pm
Forum: Car & Semi-Truck Construction
Topic: Why the death wiggle on some runs and not on others?
Replies: 8
Views: 1842

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.
by Duane
Thu Jan 26, 2012 10:30 am
Forum: Car & Semi-Truck Construction
Topic: How thin of a car is ok
Replies: 33
Views: 5131

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,...
by Duane
Thu Jan 26, 2012 9:28 am
Forum: Electronics
Topic: Calculate car speed.
Replies: 29
Views: 11635

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...
by Duane
Wed Jan 25, 2012 1:58 pm
Forum: General Coordinator Topics
Topic: Why this Rule - Wheels directly across from each other
Replies: 13
Views: 2851

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...
by Duane
Wed Jan 25, 2012 2:41 am
Forum: Car & Semi-Truck Construction
Topic: How thin of a car is ok
Replies: 33
Views: 5131

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...
by Duane
Wed Jan 25, 2012 1:09 am
Forum: Car & Semi-Truck Construction
Topic: How thin of a car is ok
Replies: 33
Views: 5131

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 ...
by Duane
Wed Jan 25, 2012 1:03 am
Forum: Car & Semi-Truck Construction
Topic: How thin of a car is ok
Replies: 33
Views: 5131

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 ...
by Duane
Tue Jan 24, 2012 9:22 am
Forum: General Coordinator Topics
Topic: Why this Rule - Wheels directly across from each other
Replies: 13
Views: 2851

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...
by Duane
Tue Jan 24, 2012 1:44 am
Forum: Car & Semi-Truck Construction
Topic: How thin of a car is ok
Replies: 33
Views: 5131

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...
by Duane
Tue Jan 24, 2012 1:23 am
Forum: Car & Semi-Truck Photos
Topic: Angry Birds
Replies: 4
Views: 2127

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...
by Duane
Sun Jan 22, 2012 8:01 pm
Forum: Car & Semi-Truck Photos
Topic: Angry Birds
Replies: 4
Views: 2127

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 ...
by Duane
Wed Jan 18, 2012 11:06 pm
Forum: Car & Semi-Truck Photos
Topic: Inception Car
Replies: 17
Views: 2476

Re: Inception Car

That is so neat, on so many levels!!
by Duane
Sat Jan 14, 2012 12:39 am
Forum: Car & Semi-Truck Construction
Topic: Micro Vibration & a little more.
Replies: 12
Views: 1713

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 forward en...