Updates to our truck

[Star Dreamer]

Guess it has been too long since we posted an update on our truck bed build since the thread is locked and won't allow any more posts, so we started a new one.

 

We did a few finishing details like adding polished diamond plate to the top of the running boards and borrowed a detail from Roberts truck to fill in the space from the side fairing to the bed by cutting sown the old piece that went in front of the wheels:

 

:

 

Also added diamond plate to the top of the bumper:

 

 

And since our trailer sat pretty far behind the truck cab and we do not plan on getting a smart car for at least a few years till we retire, late last year, I built a temporary wind deflector to close up the gap and saw an improvement in our fuel mileage. So a few weeks ago we covered it to finish it off and it looks like a very large drom now. We may close off the back end and use it for storage but for now it just keeps the weather off the bicycles, spare tire and generator:

 

 

We also installed some aluminum wheels on the back axle. Now I just need to find some of the upper sleeper side fairings to go up and over the roof to finish that area off better and get the top of the bed sprayed with a non slip surface like Line x or similar.

[dascom]

Now that is sweet, nice looking. What did you use to make the wind break,

I sit way back too and would benefit the MPG by cutting that swirl down a bit.

[Chad Heiser]

Nice job.

[sclord2002]

Really looks good. What kind of mileage improvement did you get from the fairing ? Charlie

[RickW]

Love the wind break. I have considered building something similar. Because of the Jeep it is a long way from the truck to trailer. The bug fatalities on the trailer give a clue to how much air is being moved for a 2nd time by the trailer. So I always thought some kind of cover would keep the Jeep clean and deflect the air to improve mileage. I was thinking maybe something along the lines of the flatbed semi trailers that have a removable frame then covered with a tarp. That could provide the best of both worlds of both covered and open.

 

How much difference did the wind deflection make on your mileage?

[Jack Mayer]

On our setup with the taller cab of the 780 I do not have any significant bugs on the trailer. A few, but not much. And we do carry a smart, so we are a good bit back with the trailer. Closing the gap would be beneficial, but not something that would pay off.

 

For the average RV use of the truck I doubt that putting ANY sort of wind deflector on would be cost-justified based on fuel saved. There would have to be another reason to do it (hobby, protection of deck objects, etc). Doing it to improve mpg is never going to pay off for MOST truck projects in RV use.

 

Nothing wrong with doing it....just be realistic about the "benefit".

[Alie&Jim's Carrilite]

"Jack wrote:

"For the average RV use of the truck I doubt that putting ANY sort of wind deflector on would be cost-justified based on fuel saved. There would have to be another reason to do it (hobby, protection of deck objects, etc). Doing it to improve mpg is never going to pay off for MOST truck projects in RV use.

Nothing wrong with doing it....just be realistic about the "benefit".

But you didn't mention the "Cool" factor, its priceless!

[Star Dreamer]

Jack is right, if don't put the miles on or see a big improvement then it may not be worth it except for the "Cool" factor.

 

At highway speeds, which is what we drive alot, saw an improvement of 1 mpg which for us is about 12% better. Using a conservative 10% and based on the 15000 we drove last year and at $4 per gal. for fuel it would be about a $750 savings. At today's fuel prices it is about $500 savings. We have about $400 total into the cost which includes our free labor.

 

It is built out of 2x4's and OSB board and then covered with prepainted galvanized metal. It is all screwed together and we used ST/ST screws on the outside. Since it not a permanent item, it is not bolted to the deck but held in place with our stake pockets and ratchet straps inside to our deck Drings.

 

We will be at the ECR rally if want to check it out in person.

Dave

[Jack Mayer]

1 mpg is pretty impressive if it can all be attributed to that change. It is rare that any single change could give you 1 mpg. For that, it may be worth the change if it is not too expensive.

[Star Dreamer]

Well the driver did lose 20 pounds, so maybe that helped. The trip to the ECR rally in TN should give us a good comparison. Only thing is the fuel in the tanks are a 50/50 mix of #1 & #2 left over from winter, not sure if that will have an effect on mileage.

[porky69]

#2 can give you an increase of 10% in fuel mileage over #1. You would need to do a comparison when running straight #2 to be sure, but I don't doubt the deflector helps.

 

I can see the wind deflector benefitting substantially though, we have all seen the skirts that long haul truckers are putting on there trailers and I have heard that the manufacturers tout a 3-5% increase just off of the skirts. The return on investment number is inconsequential to most of us as we don't do the big miles. But a one time investment up front is quickly forgotten if you can save $5 everytime we fill up.

[ICPete]

Your truck looks great with that new "garage" covering; congratulations on a job well done!

[hdonlybob]

Love those details.....

Really sharpens up an already sharp truck !

Cheers,

Bob

[Dollytrolley]

In the 80's and 90's almost all of the major truck companies became very aware of the need to "update" trucks with areo-treatments as the fuel prices became a major cost of truck operations. One of the worlds best low-speed (5 to 200 mph) wind tunnels is located at the U of Washington, the tunnel is named the Kirsten tunnel built in 1938 and it is a national treasure (http://www.uwal.org).

 

I had many "aero-projects" (aircraft, not truck related) in the works during those years but I remember that huge amount of efforts were expended by various truck companies to obtain better aero-treatments for the future truck models. Two of the worlds best low-speed aerodynamists were professors and engineers that operated the Kirsten Tunnel and many of the shapes of our trucks today were born of the results of the Kirsten Tunnel testing.

 

Aerodynamic design has a bit of "art" and a lot of hard science mixed into a lot testing to refine a good design. Trucks present many hard choices to obtain a fair aero-design and I was amazed how huge the effort that was expended to obtain the gains that were applied to various trucks.

 

Aircraft aero-design can be a thankless job at times but the truck aero-design is a very demanding mix of very low-speed gains tempered with what it takes to make a profit in the real world of day to day truck operations.

 

The one interesting thing to ponder is that in dry-van trailer operations, notable gains in drag reductions are obtainable in "after-body-treatment" at the rear of the trailer ( recall that the "sharp" end of a B-747 is the tail-end....the "after body").

 

Notable van-trailer total drag reduction improvements were tested and varified that could match or exceed the gains made to the tractor aero-designs.

 

Once again truck and trailers must meet many day to day operational requirements so no ideal aero-design fits into the real world at this time but who knows what the future holds.

 

Happy travels

 

Dollytrolley

[4Girls&aMan]

Looks Great Dave!

 

Wish we could be at the ECR to see it in person.

 

Travel safely!

[dubldart]

Looks good, I always admire when someone can customize there own

[billr]

Very nice indeed!

[Star Dreamer]

Thanks Dubldart, 4girls&Alan, Bob & Pete. Pete, hoping you and the Mrs are still planning on being at the ECR.

 

Dollytrolly, no money for wind tunnel testing so all of it is seat of the pants redneck unscientific engineering!

 

Porky69 our next thought is to try some redneck testing of a modified trailer tail like you see on some of the big rigs but that will be a little harder as we have to keep the ramp door workable on the trailer.

Dave

[porky69]

Maybe these would work better with a ramp door setup. http://www.airtab.com/index.htm

 

They are relatively cheap at $2.75ea and are installed at 3 tabs per linear foot (4inches on center). From http://www.buyairtab.com/

[Star Dreamer]

We have seen the airtabs and know someone that put them on their trailer but they did not get any data from before the installation so not sure if it improved it any.

 

We did do a comparison from this years trip to the ECR vs. last year. Unfortunately I do not keep track of what kind of head winds we hit so comparison does not adjust for any weather related advantages. There was less rain last year!

 

All numbers are based on the readout on the truck, I usually get about .25 to .5 better MPG when I fill up and calculate manually.

2014:

4/3/14 = 7.45

4/7/14 = 7.57

4/12/14 = 7.79

4/20/14 = 7.99

 

4/10/15 = 7.77 (had mix of #1 & #2 fuel)

4/16/15 = 8.15

4/18/15 = 9.5

4/19/15 = 9.25

 

I still think head winds make a big difference and really reduce the MPG but I cannot remember if we hit any last year. We did take the same route this year..

 

The numbers show the addition to close up the gap helped and didn't hurt plus we will be use the area for additional storage until we decide to haul a smart car or something else of the bed.

 

Dave