F.S.
Posted -
Based on your description, I wonder if air shed off the front reached a turbulent state by the time it influenced the rear wheels. Turbulent flow generally requires less energy to penetrate.
That's a good question to ask FS.
This may not answer your question, and I may have said something of the sort earlier in me starting the topic.
I imagine you might recall the posting of these pictures 4 years ago, kind of old news. but old info reposted. must be new news.
FS,
The fog machine, before the wind tunnel. helped with seeing the air. and light strips placed all over the car, I think we used that tissue type paper, that's super thin and light, they use to make those diy small hot air ballons, or seen in bags or gift boxes, I just forget the dang name its called.
no movement or wind / air flow was seen to get too the rear wheels.
As mentioned. and im wondering if the way I am trying to explain it, if people are just not understand or getting it, or How I could word it differently. for everyone.
The air just didn't have enough speed or power on it, to reach the rear wheels. The only way it did, is when we turned it up, past the point we both felt was beyond what a pinewood derby car would ever see on a standard typical track.
that was wood worx, he used to be on here.
I just got to hope and I think we all need to hope, some people will get a professional machine or build a really good one, that will work right. I seen to many of ones that no way were working right.
Then we can get more info.
But I don't think I have this wrong. I THINK my track record over the years on the forum. I hope atleast it has been supported well by me and proven well.
I am not against fenders, I think they are cool and I enjoyed making a few of them and I will make more of them for fun.
Maybe this helps people, ill try saying it like this-
There is air flow there, it is so week. that it is so easy to hurt you if you don't find a shape and style that can allow you to use the air to aid and help you to go a tad faster. This is not about a full block of wood, im talking about fenders !
The air was so week, that it is not reaching the back of the car. with what I seen. and wood worx, he was the one that got his hands on the machine for us.
I was surprised by what we seen, me and buck both were. Could the range of what we felt the was seeing be wrong, sure, do I think its off, I would open the door of saying if it is off, its got to be just a tad off.
at 3 miles per hour, seen nothing !
at 5 to 6 miles per hour, almost nothing.
7 to 8 miles per hour, something, but not much.
10 to 12 miles per hour. the air is effecting the first 1 to 2 inches of the pinewood derby car. no air after that. its like it falls off or is just to week to move anything of the pieces we had there to see , when they moved and how they moved. that tissue type paper. nothing after that distance. could not see anything with the fog machine for the colored air. just seen.
14 to 16 miles per hour the air was getting to 3 to 4 inches of the pine wood derby car.
17 to 20 miles per hour. you are getting the full air flow, like you see in diagrams, that is if the diagram was of a pinewood derby car .
It is also in this 17 to 20 mile per hour, it will move the front wheels (no fenders on it), they will start to roll and slowly spin. the rears will not.
22 to 27 mile per hour, the same as before, but the rear wheels now, will also start to spin. you will see them move wiggle a bit and slowly make a turn and spin a little.
Please note, this was not all testing or how it was all done. we tried different things. car on a track, lifted the car up off it a tad so the wheels were free. to see if they would spin and when.
I bet me and buck put in alteast 8 hours of actual testing, not counting the changes or set ups.
Example of my very last comment.
the fog machine, ugh, it tooks us a bit to figure out, how far back it needed to be, to close, to much , to far away, not enough. and just trying to get a small tiny puff. ya know this took a bit of trial and error.
The same with the replica track section and the angle plate it was one. took time to get it up and get it right.
same with plastic and paper strips, and string, gosh I bet we spent 1 to 2 hours just figuring out a right way to get it on, and be light and what we felt was right and working to see air stream and movement, we tried tiny stickers, scotch tape, thin strips, electric tape. we ended up with that super light tissue type paper.
we had it so light and sensitive, the stuff would fall off, sometimes before we turned it on, we were really worried about not getting it close or right, we worked as a team, hard at it.
In my only few pictures I shared with you all here, That was day light, we used a opening in a garage door window to shoot the air / smoke out the back of the wind tunnel. It was well past 1am. / 2 am in the morning when we wrapped up. I think we started at 10am.
The end result was several failed attempts of fenders and the design and my most winning car design ever, for me, for the kids, others on here, local packs, other kids.
The design has done very well for the scouts who have used it. and I didn't build there car for them ! many of them was just by looking at pictures of my cars.
Sporty
