Bed toolbox as partial tonneau cover

[ijames]

Hi, first post from a newbie here but I had an idea and wondered if anyone had ever tried it. I've been reading posts here for a bit and learning quite a bit, mostly on pickup trucks since I have one; thank you all for the great site. Looking at the benefits of even a 1/3 length partial tonneau cover on a pickup truck I was curious if anyone had tried moving a bed toolbox to the rear, against the tailgate, and checked the FE? Sure, it cuts cargo access but if it got even 5% better mileage at 65-70 mph it would be essentially free money for a lot of people for very little effort, and the box could be shifted back to the front when needed. Could even fab a wedge top in the spirit of aerohead's early 1/2 tonneau cover for that last bit of gain.

[Frank Lee]

That's an interesting idea, well worth a try and easy for someone with instrumentation to test.

[ijames]

Thanks, Frank. I have the pickup but no instrumentation and no toolbox :-). Just seemed so obvious that either it's been tried lots and times and just doesn't work but everyone knows that and doesn't talk about it, or it slipped through the cracks and no one with the instrumentation has tried it. I'm hoping someone on here can do a quick test or point to previous data. No, I haven't filed the patent application for the aero toolbox top but I do have a terrible name for it - the Milebox :-). I'm incapable of good names, it seems.

[cRiPpLe_rOoStEr]

Haven't still seen anybody trying this, probably due to the cargo access issue you pointed out, but it might worth a try.

[botsapper]

...there are some tailgate & sliding systems.

Delta Roller Box Sliding Truck Tool Box

http://www.pickupspecialties.com/too..._tool_box.html

http://www.pickupspecialties.com/too...ox_toolbox.htm

... some discontinued.

[ijames]

Thanks for the links. No mention on any of the three about aerodynamics or effects on FE. I had thought about a sliding rail system but figured it would be too complex and costly. If it made a significant difference in FE I'd assume they would be bragging about it, so maybe that's evidence that the effect is in the noise. Oh, both full size units (the sliding rail so it can be anywhere from front of bed to tailgate) and the swinging box (so it pivots out of the way for full bed access) are flagged as discontinued by the manufacturers; only the fifth wheel shaped box is still for sale.

[aerohead]

Back in 1981 Ford told an American Plywood Association associate that as little as 19-inches of plywood,ahead of the gate would show at the gas pump.
You'll like the 1/3rd length.
I'll find the GM tonneau cover patent.It has a drag beakdown for any percentage length.

[aerohead]

On the Cd 0.525 1982 Chevy C-10 tested by GM,a 33.33% of box length partial tonneau cover was good for a 0.03 drag reduction,or 5.6%.
We can only say that for this particular pickup,this length of cover yields this much drag reduction.
SAFETY NOTE: moving any significant weight behind the axle affects the polar moment of inertia of the truck as well as front/rear weight bias on the tires.
Be careful!

[ijames]

Yes, the two more subtle downsides to moving a toolbox to the rear that I thought of (beyond limiting cargo access) was the increased polar moment and the fact that everything in the box is probably going to get shaken up a bit more. I'm still curious if anyone with the instrumentation and a box would be willing to do the test.

I bought the wood and it's all cut up, to make a 44% cover for my 2005 GMC 2500HD extended cab short bed (77" bed, 36" cover minus about 2" of overlap with the tailgate top). Barring rain I should get it on in a couple of days. I log all fuel so I'll know in a couple of tanks even with my local mix of driving, without having to wait for another highway trip, what the gain is. From your Cd list I think my truck should be in the .45ish or slightly better range as is, so my gain won't be as good as that C10. Oh, someone had mentioned that the S10 beds are slightly tapered these days, I found out mine is too. It is about 3" narrower at the gate compared to the front.

[aerohead]

Originally Posted by ijames

Yes, the two more subtle downsides to moving a toolbox to the rear that I thought of (beyond limiting cargo access) was the increased polar moment and the fact that everything in the box is probably going to get shaken up a bit more. I'm still curious if anyone with the instrumentation and a box would be willing to do the test.

I bought the wood and it's all cut up, to make a 44% cover for my 2005 GMC 2500HD extended cab short bed (77" bed, 36" cover minus about 2" of overlap with the tailgate top). Barring rain I should get it on in a couple of days. I log all fuel so I'll know in a couple of tanks even with my local mix of driving, without having to wait for another highway trip, what the gain is. From your Cd list I think my truck should be in the .45ish or slightly better range as is, so my gain won't be as good as that C10. Oh, someone had mentioned that the S10 beds are slightly tapered these days, I found out mine is too. It is about 3" narrower at the gate compared to the front.

I don't have anything for your truck.
The 2009 Sierra XFE and Silverado are rated at Cd 0.412.
The 2nd-gen S-10/Sonoma is Cd 0.42.
The Escalade EXT/Avalanche are Cd 0.363,due in part to their factory tonneau covers