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Old 04-09-2009, 05:01 AM   #11 (permalink)
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I've seen trucks which can raise one of their rear axles when the load is small. This improves rolling resistance. I guess that wouldn't be just a small, easy mod to any truck, would it?

Also, the "wedge" on top of the cabin is partially empty inside. Can it be removed when not towing a trailer? It would significantly reduce frontal area. I've seen so many trucks without tailers on the highway and always thought whether the "wedge" could be somehow hinged to hang in the back, like a kammback, instead of plowing through the wind.

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Old 04-09-2009, 08:20 AM   #12 (permalink)
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Some ideas:

If you're ever running bobtail, some kind of collapsible fairing that would add some taper toward the rear would do good things for your aero control. But that would require some real investment to make it sturdy enough over such a large volume.

I agree that you can probably cover up the slots in the bumper. You can also go over the entire truck and probably cover a lot of those body panel separations with tape for less nooks and crannies for the wind to catch on. I know that over a chassis as big as your Prostar's there's quite a bit of chassis flex so you'll probably want to find a tape that has plenty of give, so it can move with the panels and not get pulled off.

Try covering the holes in your front wheels. I saw a quick and dirty version of that done on some big aluminum wheels in Diesel magazine; they measured a real improvement.

Time for coroplast! That big ol' chassis has a lot of big ugly gaps underneath for no reason - you can close off a lot of those and neither you nor anyone servicing the truck would ever notice.

Try fabbing up some panels - also from coroplast - to close up the gaps from cab to trailer, to make it more of one long, smoothish vehicle. If you're never pulling reefers, you don't need airflow to the front of the trailer, so block it off.
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Old 04-09-2009, 08:52 AM   #13 (permalink)
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Quote:
Originally Posted by Clev View Post
This is going to sound terrible, but what stops somebody from jacking up the rear wheels and running a couple thousand "miles" with them in the air? Wouldn't make much sense from the bonus perspective, but that one-time motorcycle prize is a tempting carrot.
Nice Idea in the pre-gps satillite tracking systems. The sat. dispatching system also keeps all my truck's diagnostics, too. Depending how close they want to micro-manage, they can check actual miles against dispatch miles if they wanted to. I'm sure if someone was to give them a reason, they might look. It is kind of easy to get lost in 1000+ trucks though. They take their mileage figures straight from the computer. Other drivers have said, "why not just add a couple of gallons (of diesel fuel) out of pocket over the quarter?" If they went strictly on actual fuel purchases, I guess that could be done. I'd "F" it up though. I'd put to much in and go from an 8 to 15 mpg. lol. They wouldn't catch that, would they?
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Old 04-09-2009, 01:39 PM   #14 (permalink)
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Clever, but I am guessing it would only work for a small set of miles. Wouldn't they know the overall miles from A to B? Then again, a carrot is a carrot.
CarloSW2
True, they'd probably want to track your miles for each job to make sure you're not using their truck for side work, but over a three month period, would they definitely be able to tell the difference between 31,000 miles and 31,900 miles?

31,000 @ 8.5 mpg = 8.5 mpg overall average
31,000 @ 8.5 mpg + 900 @ 50 mpg = 8.7 mpg overall average

I would think that even a big rig could average 50 mpg at the wheels if they were just spinning in the air. (Better yet, take them off and just spin the drums.)
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Old 04-09-2009, 01:48 PM   #15 (permalink)
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Quote:
Originally Posted by SmallFry View Post
Nice Idea in the pre-gps satillite tracking systems. The sat. dispatching system also keeps all my truck's diagnostics, too. Depending how close they want to micro-manage, they can check actual miles against dispatch miles if they wanted to. I'm sure if someone was to give them a reason, they might look. It is kind of easy to get lost in 1000+ trucks though. They take their mileage figures straight from the computer. Other drivers have said, "why not just add a couple of gallons (of diesel fuel) out of pocket over the quarter?" If they went strictly on actual fuel purchases, I guess that could be done. I'd "F" it up though. I'd put to much in and go from an 8 to 15 mpg. lol. They wouldn't catch that, would they?
Sorry, replied again before I saw this. I wonder if they compared his GPS miles to his dispatch miles, or for that matter, to his odometer miles. Not to take away his accomplishment, but like my calculations showed above, even 1,000 miles at 50 mpg is only worth about .2 mpg overall at the end of the quarter. He's either a master ecodriver (who should be made a trainer), or he's figured out a way around the system.

In any event, 1,100 trucks averaging 8.5 mpg instead of 6, at 120,000 miles per year each, saves the company over 6.4 million gallons of diesel a year. That's well worth giving away a few Harleys, even if someone cheats a bit to get it. (After all, he still needs to drive well to even be able to cheat the rest of the way.)
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Old 04-10-2009, 01:20 AM   #16 (permalink)
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Ok, I've been thinking while driving, and looking while I've been stopped. As luck would have it, I think the truck I have was slightly wrecked before I got it. Meaning, the blue bumper cover is not standard. Undamaged truck's blue bumper has a chrome plasic covering. Since this is missing, the main lower gap - that screams to be blocked, has empty bolt holes just waiting to be filled. With that one particular orafice, I can mount something there with bolts or zip ties. The others, I was thinking of trying to find some 70 mph, blue, duct tape (maybe masking tape doubled up as a last resort) to do some experiments. I'm pretty sure the gains would be minimal, but someone with more brain power than me please speculate on what to expect. Here's a rough half-azzed photoshop of what I'd like to do as a start.



Also, I thought of possibly getting a slick, chrome looking duct tape and covering the front wheel holes. I might buy a center/hub cap, but that would still leave exposed studs/lugs. I can also get chrome lug covers which are bound to be more aero than not, but am not sure how much.

I asked my immediate boss if he thought it would be ok if I did some experiments. He said I should suggest some chages to the man in charge of designing/spec-ing out the trucks they buy. I told him, "F" that! I'm going to tape them up and try to with the bike first, then I'll give my secrets - if they work.

Last edited by SmallFry; 04-10-2009 at 08:33 AM..
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Old 04-10-2009, 03:38 AM   #17 (permalink)
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SmallFry -

I bought a brand of "gun metal" grey duct tape that claims to not leave residue when you peel it off. You could put that on at your first stop, and take it off before you return. I would definitely go the zip tie route because of the easy peasy snip and remove.

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Old 04-10-2009, 04:47 AM   #18 (permalink)
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The Trucks here are often running Mudflaps in front of the front wheels, talked to a couple of drivers and they can see savings.
I'll try and get some photo's.
Also - as a suggestion, there are Propane over Diesel installations that reduce fuel consumption markedly.Obviously not something you could do, but maybe for your company to consider.

http://www.cofc.edu/~gourdink/roadtrain.jpg

Last edited by Nigel; 04-10-2009 at 04:55 AM.. Reason: googled for an image
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Old 04-10-2009, 02:25 PM   #19 (permalink)
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You run pretty hard if you are doing 35,000 per quarter. that's 2700 per week average. I am averaging about 2200 per week on my fleet @ about 5.9mpg.

Your mileage is IMPRESSIVE. I never averaged above 7.2 when I was running and that was many years ago on a 2001 engine with alot less epa bull****. What engine is your truck running? and are you willing to disclose what company you work for? I would really like a contact number for those wheel covers. I don't know the east coast very well, is it really flat? getting above 8 mpg is like a dream come true if it includes mountains.

As for adding extra miles with the wheels jacked up, it wouldn't work.
1) most companies track mileage pretty closely, and would notice an extra couple hundred added to a trip.
2) most companies figure your milage as: Fuel used / Loaded miles. Your loaded miles is fixed as a postal distance from the zip code of the shipper to the zip code of the consignee. so even if there is a detour and you have to add 50 driven miles, you still get credit for the same amount. And more directly, if you jack up the rear and add 50 miles, the ratio doesn't change except in that you used some extra fuel.

I wouldn't buy the lug covers. They stick out quite a bit more in my experience and while the surface is more aerodynamic, I don't think you will get much benefit with the extra mass/volume churning up the air.

If you really want the harley, you can cheat to get it. It's a lot easier to do since you are already so close.

lets say you are doing 8.3 mpg at 2700 miles per week. that is 314 gallons of fuel. now you know you need 9.3 to be sure of the harley so... 9.3 mpg for 2700 miles is 290 gallons. so each week you need to add 24 gallons.. or 5 a day (assuming weekends off). is ~$700 worth of personal fuel expense worth a $25k harley to you? I would say yes. If you can win without cheating you get a lot more respect though! but, honestly, in this economy... Take the freaking bike while you can get it. I know I can't offer bonuses like that.

The wheels that lift are called Drop axles or Tag axles and they are different than standard drive axles. The amount of weight your truck can pull has to do with the number of wheels (and the size of the tires) touching the ground. His truck can weigh 34k on the drive axles unless he has special supersingles on, but they looked normal. Adding a tag axle would allow him to weigh between 44k and 51k depending on where it is added, what kind of tire width, and state regs. This costs ~10k. Converting his rear axle to a drop axle would be quite a job, but since his rear axle does no actual driving its not undoable, just too expensive to be worth it unless he travels empty alot. (you can only weigh ~20k on a single axle, so it's only good for severly light loads).

Check your engine temps and Brake temps before you go adding any blocking material underneath the truck. Reduces airflow is great for MPG but overheating your brakes could mean death, and overheating your engine could mean loss of job.
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Old 04-10-2009, 09:28 PM   #20 (permalink)
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This is a really cool thread. Welcome to the forum.

One thing I'd have to wonder is what proportion of your resistance is rolling vs. aero. I assume rolling is much, much higher compared to a car. (Which presumably is why they are switching to the singles for more efficiency.) So what about tire pressure - does everyone automatically run at some "maximum" there?

Do you have any say in how tight your cab/trailer gap is? I have read that the smaller the gap, the better.

I sometimes see trucks from the same company traveling really close together on the freeway (less than a truck length apart). Presumably they're doing this to save fuel. In that case, the two drivers would have to agree to split the prize.

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