BlueBlazer
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I'm sorry I don't have answers to your questions, I didn't look too closely at the setup and it was dark out. Hopefully there are some pictures on the web somewhere.
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Why NOT tow with a shackle flip?
- Thread starter dremu
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Desert Rat
Fetch the comfy chair
I have a shackle flip and I'm going to tow with it on occasion. And I'm going swimming after dinner too...........without even waiting a half an hour. Everyone is making generalizations but it would seem to me that the performance of a truck towing with a shackle flip would all be dependent on the weight of the trailer, the spring rate of the rear springs, and the height of the lift making every situation different. But hey, I've been wrong once or twice before...
84_Chevy_K10
Banned
That is not a personal attack. A comment about someone's truck, regardless of how it is worded, is not a personal attack. Maybe you should read the rules that Steve put out last week.
It's actually fairly simple geometry and force vectors. Easiest way without getting into math and physics is just to imagine it at the extremes. Think about an arched spring. When it flattens, it the length from eye to eye grows longer. One eye is fixed, the other is on a shackle to allow for the change in length. If that shackle is tension, then it will be near vertical at static height, and tilt back as the spring compresses. Eventually, when the shackle lines up with the spring arch, the spring rate is HUGE since because the combined force vectors are pretty much just trying to stretch the shackle rather than rotate it, making it almost like an inverted arch. So the further the shackle rotates past vertical going back, the higher the spring rate gets, and the rate of increase also increases as it goes back, so (play loose with reality here) we can (sorta) say that it "approaches infinity" as the spring arch and shackle angle approach alignment.
On the other hand, also using force vectors and geometry/leverage, an arched spring with a compression shackle that goes past vertical is effectively converting some of the load force through leverage into an effort to flatten the spring and thereby reducing the spring rate. That's why people who work toward maximum "flex" with leaf springs strive to get the static shackle angle (typically) around 30* kicked back. This allows for maximum droop before the shackle aligns with the leaf arch (similar in effect and description to compression on a tension shackle) and also effectively reduces the often high spring rate of arched lift springs.
It's not really that simple, and obviously it can't go anywhere near infinity, doesn't deal with distortion and the push effects of the flattening spring, but close enough for light discussion.
On the other hand, also using force vectors and geometry/leverage, an arched spring with a compression shackle that goes past vertical is effectively converting some of the load force through leverage into an effort to flatten the spring and thereby reducing the spring rate. That's why people who work toward maximum "flex" with leaf springs strive to get the static shackle angle (typically) around 30* kicked back. This allows for maximum droop before the shackle aligns with the leaf arch (similar in effect and description to compression on a tension shackle) and also effectively reduces the often high spring rate of arched lift springs.
It's not really that simple, and obviously it can't go anywhere near infinity, doesn't deal with distortion and the push effects of the flattening spring, but close enough for light discussion.
Desert Rat
Fetch the comfy chair
84_Chevy_K10 said:
Right, it was a compliment. I'm sure most everyone here views the truck you described as the rig to end all rigs and the mall as the ultimate trail..... You should be a politician....
Ok, we can get into a discussion about the definition of personal attack, but that's going off topic. Or we can all treat each other with respect, even if we disagree, and keep it civil. And remember 2 things that will go a long way to keeping things from getting out of hand.
1) Tone has a lot to do with how things are perceived, so lets try to consider how we say things and keep it from coming across as hostile or sounding like a "put down".
2) Remember that the typed messages often come across as more terse or brutal than intended, so give each other a little slack.
Either that, or I can lock or delete the thread if this continues. You guys decide... Now, no more off topic, no more sniping at each other (from either side) and lets keep this on topic. This is my final word on the subject, the next will see this thread locked or deleted and warnings issued.
1) Tone has a lot to do with how things are perceived, so lets try to consider how we say things and keep it from coming across as hostile or sounding like a "put down".
2) Remember that the typed messages often come across as more terse or brutal than intended, so give each other a little slack.
Either that, or I can lock or delete the thread if this continues. You guys decide... Now, no more off topic, no more sniping at each other (from either side) and lets keep this on topic. This is my final word on the subject, the next will see this thread locked or deleted and warnings issued.
BlueBlazer
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Excellent description that I have stated before I agree with, it is simply the real world change when the shackle angle changes that is hard to say is drastic or almost non existant, IMO it would be hard to know without actually testing it in some sort of lab environmen since there are so many factors that go into this, rate of the spring pack, bushing design, spring length, dead area of spring at ubolts, even installation (torques and such) that it is hard to say I think that the change will be drastic.
Russ is my hero....
I seldom have the patience to type that much, but everytime YOU do, I have to believe that you raise the collective IQ of this site by a few points!!! Nicely done....I hope that people appreciate (and study) your responses on posts like this.......
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I seldom have the patience to type that much, but everytime YOU do, I have to believe that you raise the collective IQ of this site by a few points!!! Nicely done....I hope that people appreciate (and study) your responses on posts like this.......
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Looks like you got something on your nose there Greg... J/K of course.
Rene
J/K of course.Rene
Desert Rat
Fetch the comfy chair
Hey, at least he's backing another moderators play, gotta admire loyalty....
Pookster
1/2 ton status
I think timmy's being sarcastic.
That aside, here's my two cents about towing with a shackle flip:
Is it safe? It *CAN* be safe. Inherently, there is nothing wrong with a flip.
The effective spring rate is changed. Driving next to buildings, I can see the reflection of my truck in the window glass. I can visually see that the rear is very soft- softer than before.
It depends on what your towing- If you have something with a good amount of tongue weight, you could get pogo effects. I know I did. Add that with some bump steer, as the rear end went down, the bump steer would acutally change. As you hit bumps everything was so unsettled. That being said, my front springs were effectively stiffer than my rear.
Certain stretches of roads were smooth, no wind, and no problems. Other areas, were white nuckle driving experiences. After one time, towing for 6 hours, I was so stressed out,that I had to stop every hour or so to nap.
I finally fixed the problem by getting a weight distributing setup. it effectively limited my rear axle movement, by trying to make the trailer and my truck move as a singular unit. What a Difference in towing it was!!!!
No more white nuckle. Heck, the truck drove better towing than it did without the WD setup. I had virtually no bump steer, the truck tracked straight and true.
Anyways, This whole thread is screwy. Some people have issues towing, some people dont. Just like some people need to shim their axles after a shackle flip, and others dont. Some need to drop a t-case, others dont. If you want to tow with your k5, I strongly recommend a WD setup.
That aside, here's my two cents about towing with a shackle flip:
Is it safe? It *CAN* be safe. Inherently, there is nothing wrong with a flip.
The effective spring rate is changed. Driving next to buildings, I can see the reflection of my truck in the window glass. I can visually see that the rear is very soft- softer than before.
It depends on what your towing- If you have something with a good amount of tongue weight, you could get pogo effects. I know I did. Add that with some bump steer, as the rear end went down, the bump steer would acutally change. As you hit bumps everything was so unsettled. That being said, my front springs were effectively stiffer than my rear.
Certain stretches of roads were smooth, no wind, and no problems. Other areas, were white nuckle driving experiences. After one time, towing for 6 hours, I was so stressed out,that I had to stop every hour or so to nap.
I finally fixed the problem by getting a weight distributing setup. it effectively limited my rear axle movement, by trying to make the trailer and my truck move as a singular unit. What a Difference in towing it was!!!!
No more white nuckle. Heck, the truck drove better towing than it did without the WD setup. I had virtually no bump steer, the truck tracked straight and true.
Anyways, This whole thread is screwy. Some people have issues towing, some people dont. Just like some people need to shim their axles after a shackle flip, and others dont. Some need to drop a t-case, others dont. If you want to tow with your k5, I strongly recommend a WD setup.
84_Chevy_K10
Banned
BlueBlazer62 said:
It's agree with you except one point.
I personally don't care how much of a factor it is, for one big reason:
The effect of the shackle on the spring's travel is opposite from OE with a shackle flip. Basically, you've taken the factory engineered safety factor and reversed it. Regardless of any of the numbers, or by how much, you've still got the opposing effect from OE.
Raising the ride height of any vehicle that you're expecting to tow a load carries a lot of baggage along with it. We've only discussed spring rate into the picture thus far. We haven't even thought about the gearing effect of the larger tires you're going to install with that lift, the fact that those tires are heavier and produce more rolling resistance and take more power to turn, the fact that your COG is raised, and that it's harder to find taller tires with good load ratings than it is to find shorter ones. These are all factors that play into this no matter how you choose to achieve the raised ride height.
Just figure I'd throw a few more factors into the pot.
BlueBlazer
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Yep, my rig is lifted with a shackle flip and is roughly the same height as your new Dodge, so what would the difference be if in fact your rig does come with what is in effect a shackle flip? I do agree there are many factors besides the shackle setup that determines how a rig will tow.
Thanks Greg, but it's just a side effect of the fact that I have to type quite a few reports professionally where I am supporting my opinions and views to my clients, who are sometimes predisposed to disagree with me. And to Rene… 
Back on topic:
Given the details on materials and all, it's entirely possible to model it fairly exactly without physical testing, but it is far too much work to be useful to us. However, I disagree that you can't make reasonable assumptions to come to a decision about the behavior of tension shackles vs. compression shackles with arched springs.
It's a common engineering practice to eliminate as many "small" variables as possible in order to make reasonable predictions about very complex models. Even with simple geometry we can see that the effective spring rate climbs VERY dramatically as the shackle gets closer to lining up with the spring arch, and things like spring bushing deflection, spring angle, and dead area have very little effect on that. This rather dramatic geometric effect overshadows the much smaller effects of the other variables to the point that we can largely ignore them. If we wanted to know exactly what the spring rate was at a given load, or exactly what the shackle angle would be at a given load, or what load would achieve a certain spring rate, and so forth, then that would be an entirely different question where we might be forced to consider those things to get a reasonably accurate answer.
But it seems to me that the question here, based on the topic of the thread, is really one of relative effects of tension vs. compression shackle for the rear springs of the 1/2 to 1 ton pickups. While it's certainly possible to tow or haul with a shackle flip, I think it is clear that cargo and general weight/mass handling capacity will be degraded to some extent. How much depends on many other variables and becomes a much more complex problem. And that leads me back to why I'm so surprised at the use of compression shackles by the Dodge working class light trucks.
Back on topic:
Given the details on materials and all, it's entirely possible to model it fairly exactly without physical testing, but it is far too much work to be useful to us. However, I disagree that you can't make reasonable assumptions to come to a decision about the behavior of tension shackles vs. compression shackles with arched springs.
It's a common engineering practice to eliminate as many "small" variables as possible in order to make reasonable predictions about very complex models. Even with simple geometry we can see that the effective spring rate climbs VERY dramatically as the shackle gets closer to lining up with the spring arch, and things like spring bushing deflection, spring angle, and dead area have very little effect on that. This rather dramatic geometric effect overshadows the much smaller effects of the other variables to the point that we can largely ignore them. If we wanted to know exactly what the spring rate was at a given load, or exactly what the shackle angle would be at a given load, or what load would achieve a certain spring rate, and so forth, then that would be an entirely different question where we might be forced to consider those things to get a reasonably accurate answer.
But it seems to me that the question here, based on the topic of the thread, is really one of relative effects of tension vs. compression shackle for the rear springs of the 1/2 to 1 ton pickups. While it's certainly possible to tow or haul with a shackle flip, I think it is clear that cargo and general weight/mass handling capacity will be degraded to some extent. How much depends on many other variables and becomes a much more complex problem. And that leads me back to why I'm so surprised at the use of compression shackles by the Dodge working class light trucks.
BlueBlazer
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Maybe their lab testing showed it wasn't a problem? Of course, I work with engineers every day, and they make tons of mistakes, so anything is possible
84_Chevy_K10
Banned
The difference would be my new truck has twice as much power as your truck does, so I could distance myself from you so both of our dumb asses wouldn't operate such hack jobs on the same stretch of highway. 
BlueBlazer
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So your rig is a hack job now? By the way, I have a screaming 200 or so hp, so watchout
Z3PR
Banned
Okay, I pitch a thought for everyone too talk about. What about towing with a shorter truck vers something like a crew cab long bed truck ??? Opinions ?? I much reather tow with the longer truck myself.
[Edit by BadDog]
Paul, this is completely off the original topic and should probably start a different thread rather than take this one further OT.
[Edit by BadDog]
Paul, this is completely off the original topic and should probably start a different thread rather than take this one further OT.
84_Chevy_K10
Banned
BlueBlazer62 said:So your rig is a hack job now? By the way, I have a screaming 200 or so hp, so watchout
Oh man, I don't know if I can handle those kind of ponies.
tRustyK5 said:
Yep Damn near put my 75 on its lid at 75 mph from a little cargo trailer.
Good tow vehcile typically has Stiff rear suspension. The stiff suspension helps deal with the trailer tounge weights and weight shifts.
Typical shackle set up put the shackle in tension. As the shackle leans back it INCREASES the spring rate.
When you flip the shackle the spring looses effective spring rate and becomes MUCH softer. Now as the trailer tries to boss the tow rig it can get a weight transfer and upset the tow vehicle.
My solution was to increase the spring rate by adding two leafs. It helped tremendously with both on street maners and towing.
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