"Wedge" Cap for pick up trucks

[slowmover]

A bump, just because we were talking about this cap over on Dodge Cummins Diesel Forum

" . . In the spring I'm going to make a couple of aluminum "shields" to bridge the gap between the "hoop" and the cab. Just to follow the contour of the cab and close the gap. Rivet to the "hoop", 1" clearance to the cap so it doesn't rub with frame/body flex."

Summer is here in three weeks, even for Yankees.

.

[freebeard]

So far as fabrication the only tools used that alot of people wouldn't have is a chop saw, mig welder, sheet metal brake and metal shear.

No English Wheel, like Ron Covell uses, in that list.

Take a look at these:
Polymetal
MAX-metal HD

Aluminum skinned plastic. Available in 3 and 6mm thickness. The regular Max-Metal can be had one-sided and Max-Metal HD has thicker skins. I hear dirt track racers use it for their wings.

I've experimented with samples of PolyMetal, rolling and braking and shearing it. I suspect it would work on an English Wheel.

--------

Nice project overall. If you do a next generation, you could put tail-fins on it with a dead-level top edge and have an oval or removable crossbar at the tips to make a complete rectangular rack.

+1 vote for a dropped tailgate extension, but it would need a diffuser underneath. Half your drag is in the wheelwells. I think the aerocap should start at the top of the windshield.

[slowmover]

Woke up your thread, Bob, in reference to a new aero cap build and questions over resistance to crosswinds. Any comment with a few years of driving done in re your build??

Aero cap versus crosswinds.

Ross

[brucey]

This is awesome, I'm sad I missed it the first time through here.

[rdefayette]

Originally Posted by slowmover

Woke up your thread, Bob, in reference to a new aero cap build and questions over resistance to crosswinds. Any comment with a few years of driving done in re your build??

Aero cap versus crosswinds.

Ross

Good day Ross! How ya been?
well after driving with the "aero cap" installed mileage has stayed right around 19.7 mpg week in-week out. (same as it was right after the installation) 95% secondary roads, max speed limit of 55 mph on 50% of the commute, 35-45 mph for the remainder of the commute.
Anyway back to the topic at hand. I haven't really noticed any detrimental affects with regards to crosswind handleing. IMO the increased "sail" area is offset by the smoother airflow across the back of the truck by covering the "turbulance trap" (aka. truck bed). I have noticed that when towing no matter what type of trailer is being dragged around now there "seems" to be alot less turbulance induced buffeting compared to no cap. Might have (probably) has something to do with how the air comes off the back of the truck.

[slowmover]

Thanks, Bob, for the reply.

I've been slow to do much with truck and/or travel trailer due to very long days in oilfield, but am heartened by what you report in re truck aero effects on trailer (better, on the combined rig). While there is the approach that would use the tow vehicle to present a "spoiler" to channel wind over the travel trailer, my reading and hunch has been that treating each vehicle separately is the better approach (for me) as the miles under tow are dwarfed by solo miles. The gap between the two and the width discrepancy are large, in most instances, of tow vehicle and travel trailer (read: trailer with large frontal area).

Whether such effects can be quantified is one thing, but I'll rely on others when it would appear that the trailed vehicle is having a slightly easier time . . thus, perhaps, having less effect on the tow vehicle as "seen" at the steering wheel (where the ideal is least effect at the rear axle; this more a matter of proper lash-up)). If this is sort of chopping the peaks off a graphed up/down series of inputs, then the aero work on the tow vehicle is a success (as I see it). Others are welcome to think on "confirmation bias", et. al. with my comments; so be it. I do not discount good reports of small vortex generators at the tail end of 53' box vans as being fanciful, either. Grist for the mill.

I am firmly of the opinion -- as a truck driver -- that a driver in command of a vehicle even somewhat more impervious to winds is more likely to be able to exert fine motor skills effectively throughout the day to attend to drivetrain use smoothly.. Graduated responses, not gross. Timing, duration, pressure, etc. A rested man is better than one who is tiring a bit faster as things go along, etc.

If such is the case, then the heavy-duty simplicity and utility of your bed cover mitigates more fastidious attempts at "best". The crosswind-handling problem is ever-present with a pickup and my experience with a standard cab-height topper exaggerates (seemingly increases) the length of the vehicle. I am quite aware of forces fore and aft versus the "central" push experienced by a car. The force redoubles over the length of the vehicle, IOW, with the sail area increase of a standard bed topper.

A high average mpg (yours is slightly better than mine, now, with a more challenging vehicle spec and climate, perhaps even terrain, congratulations!!) coupled to possible better towing behavior is genuine "win".

The variety of approaches here, and the long-term reports, make reading this forum always fruitful for ones thinking.

As always, I take time along the way to read your posts on TDR and CF even if I don't post much.

Best

.

[rdefayette]

Originally Posted by slowmover

Thanks, Bob, for the reply.

I've been slow to do much with truck and/or travel trailer due to very long days in oilfield, but am heartened by what you report in re truck aero effects on trailer (better, on the combined rig). While there is the approach that would use the tow vehicle to present a "spoiler" to channel wind over the travel trailer, my reading and hunch has been that treating each vehicle separately is the better approach (for me) as the miles under tow are dwarfed by solo miles. The gap between the two and the width discrepancy are large, in most instances, of tow vehicle and travel trailer (read: trailer with large frontal area).

Whether such effects can be quantified is one thing, but I'll rely on others when it would appear that the trailed vehicle is having a slightly easier time . . thus, perhaps, having less effect on the tow vehicle as "seen" at the steering wheel (where the ideal is least effect at the rear axle; this more a matter of proper lash-up)). If this is sort of chopping the peaks off a graphed up/down series of inputs, then the aero work on the tow vehicle is a success (as I see it). Others are welcome to think on "confirmation bias", et. al. with my comments; so be it. I do not discount good reports of small vortex generators at the tail end of 53' box vans as being fanciful, either. Grist for the mill.

I am firmly of the opinion -- as a truck driver -- that a driver in command of a vehicle even somewhat more impervious to winds is more likely to be able to exert fine motor skills effectively throughout the day to attend to drivetrain use smoothly.. Graduated responses, not gross. Timing, duration, pressure, etc. A rested man is better than one who is tiring a bit faster as things go along, etc.

If such is the case, then the heavy-duty simplicity and utility of your bed cover mitigates more fastidious attempts at "best". The crosswind-handling problem is ever-present with a pickup and my experience with a standard cab-height topper exaggerates (seemingly increases) the length of the vehicle. I am quite aware of forces fore and aft versus the "central" push experienced by a car. The force redoubles over the length of the vehicle, IOW, with the sail area increase of a standard bed topper.

A high average mpg (yours is slightly better than mine, now, with a more challenging vehicle spec and climate, perhaps even terrain, congratulations!!) coupled to possible better towing behavior is genuine "win".

The variety of approaches here, and the long-term reports, make reading this forum always fruitful for ones thinking.

As always, I take time along the way to read your posts on TDR and CF even if I don't post much.

Best

.

Ross,
There's one point you bring up that I very rarely take into consideration as it's SOP for me is topography. If you ever get a chance to look at a topographical map of South Central PA. you'll see what I mean. (Specifically between Gettysburg and Carlisle, my locale). I'm on the Eastern side of the Appalacian foothills and there are no straight flat roads. I's love to be able to get out in the "flats" for an extended period someday just to get a handle on what I could really do under conditions that closer to "ideal" when not on curvey (sp) hilly roads. All things considered for the conditions (and 15+ years at this in numerous vehicles) I think I've pretty much maxed out what to expect. Although I keep trying for more/better. After all......The thrill is in the hunt/chase! The end result is just the reward for the work required. (anti-climax) Just like chasing down hard to find parts for a restoration. Bob

[Big Dave]

rdefayette:

Many people here use plastic materials and I even used plywood and rubber matting on a aerocap, but metal bespeaks quality,workmanship and durability.

If you do a Gen II, I have some suggestions.

1. Make it out of aluminum. In hilly country weight matters. Here on the frozen steppes of Indiana, the terrain is super-flat and weight matters little, but you are never on level grade, I suspect. The "grade/load" of the road load equation is your enemy, particularly in light of the speed-limiting terrain. The racer's problem (getting that last 20 pounds of weight off) is certainly true, particularly in that a pickup driver doesn't know what kinds ogf load he'll have top carry tomorrow.

2. Don't try to hit the top rail of your tailgate. that seems to be the intuitive goal but the well-tested "template" says crossing the tailgate about 8 inches above the top of the tailgate will give you better aerodynamic effect and gain you some cargo space in the bed.

3. Crosswinds will not much affect your driving, but BE SURE to fasten it securely to the bed. Bolts good. C-Clamps unreliable. Ask me how I know. I thought my flat tonneau was down securely with six C-Clamps but a March gust got a grip and I wound up chasing the tonneau cover fifty yards into a muddy cornfield. Make sure your hinges and latches are teenager-proof.

4. Keep your fingers out of the English wheel.

[bmack2]

Hey Bob,

Ive been mulling over designs for quite some time now.

As a student I am trying to keep it fairly affordable yet durable at the same time. Your design has finally made me decide on how to make the frame and what to cover it with. I was on the same track as you as I prefer to work with metal over wood. However, I was going to make the main support near the cab out of 2X4s and the frame out of 1/2 inch emt. I am curious what you used for the hinges on yours? I was originally going to make a soft tonneau cover that folded in and have the bottoms hinge upwards but I like your idea of having the whole structure lift up as it does. Thanks so much for your post I am glad I finally found it after all of my searching!

Just remembered you mentioned you had additional pictures, if there is any chance you could send them to me that would be awesome.

[rdefayette]

Originally Posted by bmack2

Hey Bob,

Ive been mulling over designs for quite some time now.

As a student I am trying to keep it fairly affordable yet durable at the same time. Your design has finally made me decide on how to make the frame and what to cover it with. I was on the same track as you as I prefer to work with metal over wood. However, I was going to make the main support near the cab out of 2X4s and the frame out of 1/2 inch emt. I am curious what you used for the hinges on yours? I was originally going to make a soft tonneau cover that folded in and have the bottoms hinge upwards but I like your idea of having the whole structure lift up as it does. Thanks so much for your post I am glad I finally found it after all of my searching!

Just remembered you mentioned you had additional pictures, if there is any chance you could send them to me that would be awesome.

Hopefully this link will work. https://flic.kr/s/aHsjQexiT3
I used weld on plate/ball bearing hinges from Grainger. I drilled and tapped them for a set screw so the pin wouldn't come out. They really don't have to support a lot of weight as the (my) top hinged section only weighs about 85-90 lbs. The front section will have to be relatively stout as the forces imposed on it are pretty high with the top open. To remove the top all I need to do is knock out 2 hinge pins and disconnect the struts.