sepp's second aerocap

[sepp]

hello, as some may remember i already have a thread here about the first aerocap i made for my pickup truck.here: http://ecomodder.com/forum/showthrea...ocap-6889.html
and after lots of thinking and observing i decided to start building a second improved version. my first cap works well though it has some drawbacks, mainly its heavy weight, no rear visibility and has to be dismounted if you want to load things taller than the tailgate.

my new cap is meanth to eliminate those problems, it will be open-able, be verry light and hinder rear visibilty as few as possible.

here is the new model i made in sketchup:
i use that model to measure all the parts i will need to build, i could print out proper plans but i know how relative the value of such plans are. especially when you are building with scrap wood without any standard sizes. so i use it as a base to help me, but the more the construction advances, the more i get away from the plans.

here is the base i made:
entirely made of scrap wood that i "saved" from a roof-builder company that gives their scrap away as heating wood. a reason why i now started making this new cap is that i bought a second hand bandsaw wich allows me to cut out with ease any shape or form. for my previous cap i had cut out all the round parts with a table saw, what a nightmare...

here it is on its host :
you can see the opening part of the cap opened, about 3/4th of the top opens, i left the remaining 1/4th solid with the structure to give the whole a minimal structural solidity.
as opposed to my first cap, this one doesn't go down all the way, but ends above the tail, and even slightly further back. this is partly for "looks" and also because i suspected that my old cap may have had a to steep downward end-curve wich could have caused the airflow to separate prematurely.

and here is the latest development:

added sideway and upper support beams, and you can start seeing what will be the most crazy and "WTF??" feature about this cap, there are two flaps inside the opening part of the cap (show in opened posistion) that will open and close electrically. when opened these "should" give me a 80% rear visibility. they look verry low, and initially i wanted to make 3 flaps, but i tested and with these two i can more than enough. it's the best (and coolest ) i could come up with, as transparent plexiglass wouldn't let you see through at such an angle.

i have no real idea yet of how to make the opening mechanism for the flaps, it has to be simple and cheap. any suggestions are welcome. i had in mind using a small 12 v motor i have and making a wooden mechanism that would pull or push to open or close the flaps with a button probably placed on the gear stick.

and finally suggestions are welcome about what would be the best way to cover the cap, im gonna paint the wooden structure with a product to protect the wood and render it watertight. and then i was thinking of covering it with aluminium sheets. the top and sides would be no problem, but the problem is the corner where the top goes over into the sides, that place is bent in 2 dimensions. and only a bodyworker can bend such parts.
i bought 3 aluminium sheets of each 3 sqaure meters at €10 each, but i made a big mistake by taking too thin ones (0.8 mm) wich basically reacts like paper. i also think i will put plexi windows to the side on the passenger side only, so i can see to the sides aswell.

[SVOboy]

Looking good so far!

[wwkayaker]

Not sure if I can explain this idea well enough but I will try. Put the motor at the top portion of the hinged part. Run a wooden rod down the center and attached to one side of the gear on the motor. The rod would be attached to the flaps and allowed to push the flaps open. This would require it to be attached by some type of hinge to allow for angle change. I am not sure how to control the motor. Hope this helps.

[Christ]

Whatever you decide to do for opening of the rear, as a safety feature, wire it in w/ the reverse lights.

Personally, I'd use a linear actuator, but that's just me, and a motor would be just as easy and probably lighter.

[wwkayaker]

Great idea! Wiring to the reverse lights would be easy to disconnect as well.

[sepp]

the thing is that i would prefer being able to open them at any time, even on the highway. as im somewhat of a slow-driver i need to watch my back more oftenly than my front. and it would help in confusing situations.
also when connected to the reverse lights you could let the system open, but it would stay open as you need a switched signal to close it back again if using a dc motor.
my idea for now would be to use my small motor, make some reductions for it with wooden gears or pulleys because its not powerfull enough to directly open or close the flaps. and then make it rotate some kind of wheel with a rod or shaft attacked to it (like steam locomotives had) that would push and pull. but with a stop to it so the wheel can only make half a turn. and then with a switch you could invert the current and make it open and close. but that would still require to turn off the switch as soon as the flaps are in place, otheriwse the engine keeps trying to push.

[stevet47]

Originally Posted by sepp

the thing is that i would prefer being able to open them at any time, even on the highway. as im somewhat of a slow-driver i need to watch my back more oftenly than my front. and it would help in confusing situations.
also when connected to the reverse lights you could let the system open, but it would stay open as you need a switched signal to close it back again if using a dc motor.
my idea for now would be to use my small motor, make some reductions for it with wooden gears or pulleys because its not powerfull enough to directly open or close the flaps. and then make it rotate some kind of wheel with a rod or shaft attacked to it (like steam locomotives had) that would push and pull. but with a stop to it so the wheel can only make half a turn. and then with a switch you could invert the current and make it open and close. but that would still require to turn off the switch as soon as the flaps are in place, otheriwse the engine keeps trying to push.

Just use a momentary switch.

But I think an actuator would by far be the best solution.

[aerohead]

Without a English Wheel to create these complex compound surfaces in sheetmetal,I used composites for these areas.I've used polyester resin and fiberglass wet layups over polyisocyanurate foam from the building center,and also got away with open-cell styrofoam,by first coating it after shaping,with a coating of regular white glue and letting that dry completely.---------- Also,a cedar-strip- canoe construction technique can be used to create the curves,also covered with a layer of fiberglass reinforced polyester or epoxy.--------------------------------- With respect to the louvers,I ended up putting a passenger side plexi-glass window for side vision,and a "step" on the back-sloping section with a short,full-width vertical plex window for rear vision.Not as sexy as the louvers,but simple and very good vision.------- Commercial exhaust fans often have often have what is called a gravity-damper,which has a beautiful mechanism you could copy,which would allow the two louvers to operate together.A simple tension spring might keep them from "dancing" while closed and going down the road.---------- A push/pull cable,air-ram,hydraulic-ram,12-volt electric solenoid from a door or Radio-controlled electric toy car,etc.,or,high-torque gear motor from a children's 24-VDC riding electric toy car might provide the means to actuate the louvers.------------- Your first cap was a sweetheart,will be fun to see #2 going down the road.

[Big Dave]

The shape looks to be excellent.

Reinforce the hinge structure. It is a high stress area.

The lid may be heavy and an electric linear actuator may be the ticket.

Leave yourself a hard point or two for one or two lipstick CCTV cameras.

[lunarhighway]

as a safety feature, wire it in w/ the reverse lights.

wire it with the breaks!, instant airbreak ala veyron and its always a good idea to have a look at how fast the truck behind you is going before standing on the breaks (not that that's very hypermiler like but still)

for actuators perhaps a powered window motor and some pulleys could work? i assume some of these motors might already have witches build in to detect the end of the windows travel... although the operations speed and strength might not be enough for what you need