View Single Post
Old 01-16-2013, 07:56 PM   #12 (permalink)
aerohead
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 16,267
Thanks: 24,392
Thanked 7,360 Times in 4,760 Posts
antics

Quote:
Originally Posted by Tesla View Post
What do you mean about "pressure ridge airborne antics"?
Is that to do with varying vortexes and pressures causing oscilations and unwanted flap?

Some sort of flexable/deformable gap filler would be ideal as long as it didn't flap around in the wind.

I have started thinking about ideas for the "ever elussive" inflatable gap filler/boattail idea, just read through some old discussions on the topic:
http://ecomodder.com/forum/showthrea...ack-22480.html

Seems the biggest hurdles are:
Inflation & deployment system.
Maintaining appropriate shape.
Minimising oscilations.
Fabric durability.
Simple attachment & removal for utility.

Would shade cloth be a suitable external skin "aero wise" as it is a fairly course weave?
From what I have read all indications are it should be fine as I have seen many comments suggesting that in reality we are actually moving turbulant air all the time so finer details of skin surface are irrelevant, the basic form is what is important.

*I'm thinking if one were to make the outer skin out of this type of material, it is cheap, strong & durable and is often used on the front of trailers as a stone deflector to minimise paint damage.
*Then use a lighter weight material internally to create a grid pattern lengthwise so individual inflation tubes could be inserted, visually looking into it like a case of wine, 12 individual bottles each in its own compartment.
*The inflation tubes could just be a suitable length and cross section of plastic tube sealed at one end and inflation tube attached to the other end.
*All tubes connected to one inflation manifold, where you can have one way valve, inflate/deflate etc.
*Use a duct from the front stagnation point, highest pressure on vehicle is there I imagine, supplementary blower if required. I could probably duct 2-3" flexitube without increasing frontal area on my car.
*Mount on vehicle side with a solid frame of appropriate design and angle to begin boattail shape.
*Trailer rotates around shape deforming as required, maybe a slip sheet of thick plastic attached flat on trailer face to protect trailer finish.
* Have one larger cell (or multiple) in the centre with a large rubber balloon attached to the manifold, this would remain deflated in normal operation, but when the trailer was turned hard the pressure from the compressed cells would inflate it temporarily until vehicle was in straight line again.
*It is a relativly low pressure set up < 3 psi most likely, aim to use commonly available materials to keep cost, but moreso inevitable maintenance down, one way valves can easily be made with ping pong ball, rubber O-ring and PVC pipe fittings, the pump/fan would be a negative, best avoided if possible.
*HD zippers, like on tents or larger luggage bags, could be incorporated for easy attachment and removal etc.

That's today's idea, see what else comes along.
A couple years ago,returning from a Bonneville trip with the trailer,she went airborne a number of times near Vail,Colorado on I-70 when I hit pressure ridges caused by winter freezing.
In a curve,the trailer would come completely off the ground and swing away due to centrifugal force.Bizzare!
--------------------------------------------------------------------------
*As to inflatables,If you're really serious,I recommend you look into the aerospace fabrics used with outdoor inflatable advertising.They'll be something like a Hypalon-coated fabric which can endure arctic temps while remaining supple.
You'll also need to invest in,lease,rent,or borrow a commercial sewing machine as used for automotive,marine,and aircraft upholstery.You need the double walking-foot and ability to plow through heavy material without snapping the needle off.
With these fabrics I don't think you'll need internal bracing structures.
--------------------------------------------------------------------------
The envelope can be secured with VELCRO.
--------------------------------------------------------------------------
I've used a 12-VDC ventilation fan from a VW Westfalia Campmobile for inflation.Just providing inflation tension,it doesn't use enough Watts to affect mpg appreciably.They'll run day and night no problem.
--------------------------------------------------------------------------
I recommend that you build a mockup and begin testing.As reality intrudes and things get ripped apart it will evolve into a lasting design.
There are so many dynamics involved with a articulating trailer that you've just got to jump in and see how it goes.
I've had many failures on my path,but as my project sits right now,I could take her around the world without event.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
The Following 2 Users Say Thank You to aerohead For This Useful Post:
BamZipPow (01-18-2013), Tesla (01-19-2013)