[Land-speed] Polar Moment or KTM vs the Salt

[NT788 at comcast.net]

I sometimes poke a pin in the bottom(cg) of a scale shape and blow air at it. On dusty ground might work also. Jack

-------------- Original message -------------- 
From: "Ed Weldon" <23.weldon at comcast.net> 

> Knowledge, time and money (KTM). Sprinkle enough of it on your LSR project 
> including a measure to overcome demon randomness and you'll accomplish a 
> reasonable goal. 
> 
> 
> 
> OK, Mayf pretty well outlines the big engineering problem that we all 
> instinctively know requires NASA (or at least Ford Motor Co.) levels of KTM 
> to solve. I think most of us prefer a simpler approach that provides useful 
> rules of thumb rather than a lot of heavy math. Greg Myers' anecdote about 
> the Wright brothers describes the way a lot of us operate. Singular 
> datapoints, experiences such as Kieth and Tom describe count for a lot, too. 
> Simple experiments like the swimming pool test Neil suggested. (Only a 
> Southland guy would suggest that this time of year) (Or are we maybe 
> suggstion a new Speedweek event for the motel swimming pools?) 
> 
> 
> 
> Personally I like my idea of conning someone else into doing the work to 
> their own as well as our benefit. But if that fails? ...build a scale 
> moving surface wind tunnel. Will 1:25 scale produce useful results? There 
> are lots of cheap plastic car models in that scale. Or maybe larger scale? 
> (uh-oh!! KTM again....) 
> 
> 
> 
> OK, let's see...here's things to go find: 
> 
> 1. 6" belt sander and some kind of variable speed motor to run it. 
> 
> 2. an electric leaf blower 
> 
> 3. A nice little linear bearing stage to mount the body on and transmit 
> aero forces to a spring scale with minimum friction drag 
> 
> 4. A way to accurately measure RPM's of the sander rollers and 5. below 
> (smells like "M"; more on that later) 
> 
> 5. Tiny can motors like the model train guys use in their locomotives to 
> turn the car wheels to match the belt travel speed. 
> 
> 6. K (knowledge) relative to building a small wind tunnel and application 
> of the scaling factors. 
> 
> 7. some kind of smoke generator? 
> 
> 8. Lots of cheap plywood 
> 
> 9. what else? 
> 
> 
> 
> Ed Weldon 
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