Improving Aerodynamics
11-27-2005, 10:49 PM
#32
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In aerodynamics, the TRAILING edge is much more important than the leading edge when it comes to drag.
Consider a teardrop. THE MOST aerodynamic shape. Notice how the "leading edge" is somewhat blunt, while the TRAILING edge is tapered to a razor's edge.
This is what you should try to replicate with your trailer-- and the truck, too. There are two ways to look at this: either with the truck/trailer as an assembly, or with each having its own aerodynamic signature.
Your rig will overall be more aerodynamic if you can follow these basic principles:
- minimize the gap between truck and trailer, making them closer to one rig rather than two separate pieces. (This is why NASCAR drafting works).
- Smooth the transition from truck to trailer. This is easier if they're closer together.
- A bullnose on the leading edge MAY help a little bit, but the TRAILING EDGE is where you should be investing your time and effort. If you can install AIRTABS along the trailing edge, you should. They are a great help.
Finally, your gearing overall is too high. The truck is being asked to carry a heavy load in a way that it's not optimized to do (low rpm). It's roughly the same is someone making you do pushups-- but with all your weight supported on only one finger of each hand. You're still doing a pushup, but it's a little tougher because you're exceeding the design parameters of your hands.
jmo
Consider a teardrop. THE MOST aerodynamic shape. Notice how the "leading edge" is somewhat blunt, while the TRAILING edge is tapered to a razor's edge.
This is what you should try to replicate with your trailer-- and the truck, too. There are two ways to look at this: either with the truck/trailer as an assembly, or with each having its own aerodynamic signature.
Your rig will overall be more aerodynamic if you can follow these basic principles:
- minimize the gap between truck and trailer, making them closer to one rig rather than two separate pieces. (This is why NASCAR drafting works).
- Smooth the transition from truck to trailer. This is easier if they're closer together.
- A bullnose on the leading edge MAY help a little bit, but the TRAILING EDGE is where you should be investing your time and effort. If you can install AIRTABS along the trailing edge, you should. They are a great help.
Finally, your gearing overall is too high. The truck is being asked to carry a heavy load in a way that it's not optimized to do (low rpm). It's roughly the same is someone making you do pushups-- but with all your weight supported on only one finger of each hand. You're still doing a pushup, but it's a little tougher because you're exceeding the design parameters of your hands.
jmo
11-27-2005, 11:16 PM
#33
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Well I don't think the brakes are dragging. I would think they would catch on fire or wear out after an hour.
I can't use the "airtabs" since the side of my trailer is not smooth. But it sounds like an interesting concept.
While axle alignment I suppose could be an issue, the trailer is brand new so I hope that isn't the case. And as I state below this is not an "always on" problem.
The reason why I am asking about the aerodynamics is because I can be going South with the truck really stuggling. I start heading East and the truck will pull great due to wind change.
FYI.: I did edit my original post with a picture along with request for those to stop telling me there is a problem with my truck...that is not what I was asking about.
I can't use the "airtabs" since the side of my trailer is not smooth. But it sounds like an interesting concept.
While axle alignment I suppose could be an issue, the trailer is brand new so I hope that isn't the case. And as I state below this is not an "always on" problem.
The reason why I am asking about the aerodynamics is because I can be going South with the truck really stuggling. I start heading East and the truck will pull great due to wind change.
FYI.: I did edit my original post with a picture along with request for those to stop telling me there is a problem with my truck...that is not what I was asking about.
11-28-2005, 03:29 PM
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Don't think Brakes are dragging.........and trailer is brand new...Hmm,,, well like I said -most axles (if not all are wrong from the factory) So while you are postulating all this please check and verify a few things.....other wise its a a long lengthy thread with nothing accomplished.
11-28-2005, 03:37 PM
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So I guess the axles magically straighten every once in a while for good pulling and the get off again and cause bad pulling? This sounds a little silly.
And as far as the brakes go, I have never seen any vehicle that the brakes will drag for more than a few miles without getting hot and breaking free. Or I would at least feel the difference at lower speeds. Or at least after several hours of driving. The problems only happens at high speeds depending on wind direction.
And as far as the brakes go, I have never seen any vehicle that the brakes will drag for more than a few miles without getting hot and breaking free. Or I would at least feel the difference at lower speeds. Or at least after several hours of driving. The problems only happens at high speeds depending on wind direction.
11-28-2005, 11:27 PM
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isitfast?????you have problems...I stated some observations and answers....there is no magic in axle alignment..if you do not understand what I said you do not need to come off puffy about it
most axles are strait across.....most light weight trailers have welded points so no adjustment would seem necessary......that's where the lie begins.........you want to know more?? if you know it all why are you asking questions??.........was just trying to help........I will shut up and go away and help the ones that need help as you dont need any
PS brakes can drag slot and not go up in smoke
most axles are strait across.....most light weight trailers have welded points so no adjustment would seem necessary......that's where the lie begins.........you want to know more?? if you know it all why are you asking questions??.........was just trying to help........I will shut up and go away and help the ones that need help as you dont need any
PS brakes can drag slot and not go up in smoke
11-29-2005, 02:30 AM
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Thumper: not trying to sound puffy. I was just trying to prove my point that this comes and goes. If the axles are welded where no alignment is (easily) adjusted then it seems that this would be a problem I would be having all the time. Please explain if I misunderstood...I am here to learn.
And if these brakes will last for hours of constant pressure; that is great news. If they are functioning properly I shouldn't have to replace them ever. But if they are hanging shouldn't I feel this at slow speeds? This rig will coast what seems like forever whenever I start to slow down.
And if these brakes will last for hours of constant pressure; that is great news. If they are functioning properly I shouldn't have to replace them ever. But if they are hanging shouldn't I feel this at slow speeds? This rig will coast what seems like forever whenever I start to slow down.
11-29-2005, 07:48 AM
#38
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Originally Posted by IsItFast
This rig will coast what seems like forever whenever I start to slow down.
You can't run oversized tires with a 3.73 rear end, pull a wind sail and run 80 miles per hour and expect 20mpg. That is just a fact of life. This is what we are trying to tell you.
Bob
11-29-2005, 01:50 PM
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Thanks Bob, but I wish everyone would listen to what I am asking. This is not a post about "how do I improve MPG's" or "do you think the mods are causing problems". No one can seem to understand that (or hear what I am asking). The truck had the same problems when it was bone stock a few months ago. I am not expecting miracles on a MPG's improvement at these speeds but just looking for ways to IMPROVE AERODYNAMICS. I have had only about 2-3 people out of these 3 pages of posts give an answer to THIS question.
11-29-2005, 02:55 PM
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Originally Posted by IsItFast
Thanks Bob, but I wish everyone would listen to what I am asking. This is not a post about "how do I improve MPG's" or "do you think the mods are causing problems". No one can seem to understand that (or hear what I am asking). The truck had the same problems when it was bone stock a few months ago. I am not expecting miracles on a MPG's improvement at these speeds but just looking for ways to IMPROVE AERODYNAMICS. I have had only about 2-3 people out of these 3 pages of posts give an answer to THIS question.
11-29-2005, 03:15 PM
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OK like I said I breezed over your post.....as far as brakes ,,----you need to apply your heat gauge to the drum (calibrated hand or instrument or jack up a wheel and spin it once all warmed up) and see what you get.
The axles are usually welded tabs that are slammed on at production speed where close is "good"....they are ezly cut off and placed where needed and re welded.
this is what I think I know and replaced where necessary
The axles are usually welded tabs that are slammed on at production speed where close is "good"....they are ezly cut off and placed where needed and re welded.
this is what I think I know and replaced where necessary
12-10-2005, 10:13 PM
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isitfast
thumper is correct i build many trailors over a years time and the easy way to check your axle is to run a string from the center of your hitch back to the bottom of your axle. at the bottom plate that bolts everything together there is a pin that sticks through the bottom plate. take your string and swing it in a arc from pin to pin. from the center of your hitch to the pins there should not be more than 1/8 inch difference. out side of that slow down to around 65 and i bet you see a big differece in the way it pulls.
mark
thumper is correct i build many trailors over a years time and the easy way to check your axle is to run a string from the center of your hitch back to the bottom of your axle. at the bottom plate that bolts everything together there is a pin that sticks through the bottom plate. take your string and swing it in a arc from pin to pin. from the center of your hitch to the pins there should not be more than 1/8 inch difference. out side of that slow down to around 65 and i bet you see a big differece in the way it pulls.
mark
12-10-2005, 10:40 PM
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The only thing I can see you doing to improve the aerodynamics or air flow is to buy a full size truck topper like the one seen here.
A wing will not help you as the air will still drop behind the truck cab and hit the front of the trailer. In driving a semi I have learned that air will pass over a space of no bigger than around 4 feet. In other words, if the gap is larger than 4 feet, the air will start to enter the gap and hit the front of the trailer. This explains why a fifth wheel will get better fuel mileage than a travel trailer.
A wing will not help you as the air will still drop behind the truck cab and hit the front of the trailer. In driving a semi I have learned that air will pass over a space of no bigger than around 4 feet. In other words, if the gap is larger than 4 feet, the air will start to enter the gap and hit the front of the trailer. This explains why a fifth wheel will get better fuel mileage than a travel trailer.
12-11-2005, 01:01 AM
#44
Top's Younger Twin
I'll ask this in reference to my first post...what are your trans temps?
Seeking better aerodynamics is one way to improve towing and mileage but so is checking other items.
A full canopy bed cover will help some. Adding a wing at the back of this will help.
A V-nose off the back of the trailer would help lots!
Of course its not easy to do that but it would improve the drag immensely.
There was a trailer company near me that made horse trailers with a big rear V and they put the tack room in the V. I pulled a couple of those trailers and I still wonder today why that design is not on RV trailers. Its not because of patents.
As Hohn touched on...theres a shape that works better then the norm.
Scotty
Seeking better aerodynamics is one way to improve towing and mileage but so is checking other items.
A full canopy bed cover will help some. Adding a wing at the back of this will help.
A V-nose off the back of the trailer would help lots!
Of course its not easy to do that but it would improve the drag immensely.
There was a trailer company near me that made horse trailers with a big rear V and they put the tack room in the V. I pulled a couple of those trailers and I still wonder today why that design is not on RV trailers. Its not because of patents.
As Hohn touched on...theres a shape that works better then the norm.
Scotty
12-11-2005, 06:58 AM
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I'm not sure what other tricks are out there for improving the aerodynamics of you rig but I have a trick I use with a strong headwind that may make you trip a bit easier, it's not a fix but it'll give you a quieter ride and a few MPG. Find a semi rolling along at a nice speed and stick to the rear bumper. Makes a huge difference with my 25' I'm sure it would help you out too. Good luck with all the suggestions and goodies your trying.