RE: Sherline Trailer Tongue Scales
I'm as puzzled as Larry is -- but I'm thinking about it.
For those of you who have observed a tongue weight change with the slide out -- what type of suspension do you have? Leaf spring or torsion tube?
Ron
RE: Brake controller with a Hensley
If you properly set up the MaxBake or the BrakeSmart, you do not need a "Boost" function. The MaxBrake sets a gain and lets yo have more or less trailer braking with the amount of brake line pressure.
One of our members who uses both a Hensley Arrow and a BrakeSmart seems to disagree with you.
In this post he states:
I say if you're not worried about installation....Go with the Brakesmart or Maxbrake. I personally prefer the Brakesmart of the two of those just 'cause of all the additional settings Brakesmart gives you to tweak it (initial braking, etc) that Maxbrake doesn't. Especially, if you are considering a Propride or Hensley hitch, that hitch works much better if you can dial in some initial braking.
(Underline added for emphasis)
Ron
RE: Brake controller with a Hensley
---I like the Prodigy because of the boost feature. The boost enables the TT brakes to lead the TV brakes and avoid the notorious bump.
I do not believe Brake smart or the Jordan have a boost function but I maybe wrong on that.---
The Jordan, when properly adjusted, has an inherent "boost" feature. Virtually all brake systems have a certain amount of "dead zone" through which the pedal travels before any significant braking force is applied. A properly adjusted Jordan will produce an increasing current as the pedal moves through the dead zone. This means the TT brakes will already be activated before TV braking begins.
The BrakeSmart can cause the TT brakes to lead the TV brakes, similar to the Prodigy/P3 "boost", via its "Initial Brake Constant" feature.
As far as I know, the MaxBrake does not provide any boost feature; which, IMO, means it is not a good candidate for use with a 4-bar-linkage hitch such as the Hensley Arrow or the Hensley Cub.
Ron
RE: Hensley Arrow or Equalizer Hitch?
OK, everyone here keeps referring to friction sway control as being reactive.
Please don't include me in that group. The point I've been trying to make is that, IMO, friction-based devices are pro-active because they try to make the TV and TT act as a single unit with no pivot point. Also IMO, the non-friction devices are reactive as regards TT swing because they do not try to prevent the TT from swinging. However, and probably more importantly, the non-friction devices are pro-active as regards the effect of lateral forces imposed on the TV because the effective point of application is moved forward.
--Friction is much more pro-active than it is reactive. You see, there are two types of friction...static and dynamic (dynamic friction being the reactive friction or sliding friction). Static friction forces are typically much higher than sliding friction forces.
I agree, except for the phrases, "much more" and "much higher". A typical static coefficient of friction for dry steel-on-steel is 0.7 whereas a typical "sliding" (kinetic) coefficient is 0.6. Typically, about a 15% reduction for kinetic versus static.
Ron
RE: Hensley Arrow or Equalizer Hitch?
FWIW, both the Arrow and ProPride do by design truly lock-out the rotational forces at the hitch ball.
It's true that the Hensley Arrow design does prevent the coupler from rotating relative to the ball. But, that does not mean the TT cannot rotate (yaw) relative to the TV. It just means the effective point of rotation is moved closer to the TV's rear axle -- typically about 20" behind the TV's rear axle depending on ball overhang. And, as the TT swings relative to the TV, the pivot point moves rearward and to the side. At a yaw angle of about 15 degrees, the 4-bar linkage pivot point is approximately at the location of the ball.
Unlike a friction-based device, the 4-bar linkage does not resist TT swing. The effectiveness of the 4-bar linkage is due to the TV/TT pivot point being moved closer to the rear axle. This means lateral forces imposed by the TT are acting over a shorter moment arm, and the steering torque on the TV is reduced.
The DC to the best of my knowledge does not {lock-out the rotational forces at the hitch ball}.
The DC utilizes longitudinal tension and compression forces in the WD bars to attempt to prevent the TT from swinging relative to the TV. I guess, if fairness to Mike Up's opinion, one could say the TV and TT are "locked" together up to a point at which the static friction forces are exceeded. But, if we use that definition of "lock", we would have to say that all friction-based controls lock the TV and TT together -- up to a point.
If there were no friction force between the DC's cam and bar (if the cam were replaced with a roller), there would still be some resistance to relative movement; but the resistance would be significantly reduced.
And if anybody doesn't believe me.............behind the school, at the swing set at 3:30 and we'll settle this ;).
By 3:30, I'll be too full of turkey to settle anything.
Ron
RE: Hensley Arrow or Equalizer Hitch?
---The matter of the fact is that the friction that the equalizer uses, is sliding friction that doesn't prevent the sway.
The Equal-i-zer utilizes both linear friction between bars and L-brackets and rotational friction between bar sockets and hitch head. The yaw-resisting torque resulting from friction at the socket/hitch contacts is probably more than twice as great as the torque generated by bar/L-bracket contact.
As for "sliding friction that doesn't prevent the sway" --
every friction-based sway control (including EQ and DC) utilizes static friction rather than "sliding" friction to attempt to keep the TV and TT "locked" in a straight line. These devices prevent relative yaw up to a point at which the yaw-producing torques exceed the static torque resistance of the sway control.
When the static resistance is exceeded, the friction forces transition from static to kinetic friction and the yaw-resisting torque will decrease by perhaps 15%. The sway control is still resisting sway -- just at a slightly reduced level.
The DC is locked, by a friction locking system, but doesn't use sliding friction to cotrol sway. It uses a locking system to prevent sway.
There is no "lock" -- there are only normal forces and friction forces acting between cam and bar. When the longitudinal force in the bar exceeds the longitudinal component of normal force plus static friction force, the bar will slide relative to the cam. Once relative movement begins, the sliding (kinetic) friction force is working to resist sway.
The way Reese states it, E-trailer states it, it's not a friction sway control.
The Reese literature contradicts itself. The promotional literature, perhaps written by marketing people, implies the DC does not use friction. The installation and operating instructions, probably written by technical people, clearly states that the DC utilizes metal-to-metal friction. In technical matters, I would go by what the technical people say.
Ron
RE: Brake Controller -Cheap vs. Expensive
The full effect of the boost lasts for 2 seconds and then reduces to 50% according to:
"Setting boost levels for the Prodigy". (Note: This link was working in January 09, but now seems to be inoperative)
QUOTE
---Boost level 1 generates about 13% of power set for the first 2 seconds and boost level 2 and 3 generate about 25% of power set for the first 2 seconds. All levels reduce by 50% after 2 seconds when the braking system is generating enough deceleration of its’ own accord.
UNQUOTE
Ron
Note: Moderator edit to fix link to Prodigy Manual.
On further edit:
Hi Barney. The above quote does not come from the Prodigy Instructions. The quoted material was found in:
Tekonsha Technical Bulletin 20020062 Setting Boost Levels which gave additional information about boost settings.
Unfortunately the Technical Bulletins no longer seem to be accessible.
A Happy Thanksgiving to everyone.
Ron
RE: Hensley Arrow or Equalizer Hitch?
Are you 100% sure about that? Not saying you're wrong, but it would seem that it would take more effort to get the cam out of the detent than it would to slide on a flat surface. I equate it to pushing a car out of a rut, it takes more energy to lift AND move the car at the same time, then once out of the rut it's much easier to push. I wouldn't think the additional weight on the cams with a flat surface would have more friction than overcoming the detent and the metal-on-metal friction. If that were the case then I would think they'd forgo the detents and just have you put more weight on the bars to get more friction. Also, more weight on the bars once out of the detent would seem to have a minimal effect due to the reduced leverage (Shorter distance from the cam to the head).
This photo provided by member John Barca shows a cam centered in a WD-bar detent.
http://i23.photobucket.com/albums/b378/JBarca/Hitch%20Setup/6inframeDCcloseup.jpg
This photo from John Barca shows the shapes of the detents for two different bar sets.
http://i23.photobucket.com/albums/b378/JBarca/Hitch%20Setup/1200and800lbbars.jpg
For most forward-driving conditions, the TV/TT articulation will be within +/- 10 degrees, and the cam will remain in contact with the sloped surface fore or aft of the center of the detent. The relative movement will be about 0.1" per degree of articulation.
As long as the contact point remains on the sloped surface, both the normal force and the friction force will affect the resistance to sway. And, the resistance would be different from that of a cam on a flat (horizontal) surface.
The friction force resists relative movement of cam and bar both when the cam is moving away from center and when the cam is moving toward center. The normal force resists movement when the cam is moving away from center and promotes movement when moving toward center. The promoting of movement gives rise to the "self-centering" effect.
Anyway, I haven't towed with a DC setup and I haven't seen or looked for anything that shows the force required to slide the bars, I'm just thinking about how it seems to work to be the most effective.For chain tension = 1000#, coefficient of friction = 0.7, and bar slope angle relative to horizontal = 30 degrees, the horizontal force between cam and bar will be about 2000# when the bar is moving away from center and about 20# when the bar is moving toward center of detent.
Ron
RE: 1000# comparison
---So my fairly safe estimate based on years of experience I go with about a 50% increase in rear axle load based on the weight applied to the ball. My "estimate" turned out to be something we both agree on, except you INCORRECTLY interpreted I was blaming the majority shifting of mass on suspension deflection.
I can only interpret what you did write rather than what you intended to write.
For the benefit of others who might have "INCORRECTLY interpreted" your two posts, it might be good to use some numbers to put things into perspective.
I think we agree that adding a load of 1000# on the ball might cause the load on the rear axle to increase by 1500#. Then, we also must consider how much load is added to the rear axle when "sagging the rear suspension causes weight to transfer from the front axle rearward."
Let's assume the TV's wheelbase is 130". Let's also assume the unhitched TV weighs 6000# with 3300# (55%) on the front axle and 2700# (45%) and the CG is 24" above the front axle and 58.5" aft of the front axle. And finally, let's assume the 1000# on the ball causes the front of the TV to lift 1" and the rear to drop 2".
For these assumptions and with a little trigonometry, we can show that the chassis angle will change by about 1.3 degrees and the CG will move rearward by about 0.54". This means the sagging suspension will cause about 25# to be added to the rear axle in addition to the estimated 1500# added by the lever effect.
So, if anyone was getting the impression that load transfer caused by "sagging the rear suspension" is significant -- it is not.
Ron
RE: 1000# comparison
1000 pound tongue weight is going to be approx 1500 pounds on the rear axle (without a WDH) partly because of the distance from the axle's centerline to the ball is a lever, and also because sagging the rear suspension causes weight to transfer from the front axle rearward.---so pushing down on the ball of the hitch is going to sag the truck rearward, which causes weight to be removed from the front axle.
Both of the above quotes are incorrect.
The sagging of the rear suspension does not cause weight to be removed from the front axle. Even if you had infinitely stiff rear springs and zero sag, the vertical load on the ball would still cause the load on the TV's front axle to be decreased.
For many TVs, placing 1000# on the ball will increase the load on the rear axle by about 1500# and decrease the load on the front axle by about 500#. These changes in load are not caused by the sagging of the rear suspension.
If the WD system causes the load on the TT's axles to increase by 250#, then the load on the TV's front axle will increase by about 500# and the net change will be about zero. The load on the rear axle will decrease by about 750# and the net change will be an increase of about 750# on the rear axle. These values, of course, depend on TV wheelbase, rear axle to ball distance, and ball to TT axles distance.
Ron
RE: Hensley Arrow or Equalizer Hitch?
---I was travelling at 45 MPH this summer, came around a curve, and a guy had stopped dead in the middle of the road to look at the scenery. I jammed both feet on the brake pedal as hard as I could, and pulled up just 2-3 feet from his bumper. If I had had my conventional nitch, I am sure the trailer would have jackknifed and casued a rollover. Other than scaring the heck out of me, no problem.
Why are you sure the TT would have jackknifed if you had been using a conventional hitch?
Ron
RE: Hensley Arrow or Equalizer Hitch?
The metal to metal friction is what keeps the spring arm locked into the cam, that's it. There is no sliding metal to metal friction force that controls sway as does the equalizer.Mike, every friction-based sway control uses friction to resist relative yaw between TV and TT. Some devices (e.g. Dual Cam and Equal-i-zer) produce more resistance than others (e.g. "fiction sway bar"). Every friction-based SC device will keep the TV and TT "locked" together until the force or torque acting on the device exceeds the amount of friction force which can be generated.
A common misconception is that friction force does not exist unless there is relative movememt (slippage) between the friction surfaces. This is not correct. In fact, for most materials, the static (non-sliding) coefficient is greater than the kinetic (sliding) coefficient. Every friction-based device attempts to control sway before it starts by trying to keep the TV and TT "locked" in a straight line. Of course, at some point, slippage must occur in order for the TV/TT to make a turn.
The Dual Cam uses both friction forces and non-friction forces to resist relative yawing between the TV and the TT. The friction force is generated between the cam and the WD bar and acts in a direction parallel to the sloped surface of the bar. The normal force (non-friction force) is generated between the cam and the WD bar and acts in a direction perpendicular to the sloped surface of the bar.
The friction force is proportional to: 1) the amount of force applied to the end of the bar via the lift chain and cam, 2) the slope angle of the bar, and 3) the coefficient of friction between cam and bar. The normal force is proportional to: 1) the amount of force applied to the end of the bar via the lift chain and cam, and 2) the slope angle of the bar.
The vertical component of the friction force plus the vertical component of the normal force is equal to the vertical load on the rear end of the WD bar and determines how much weight transfer will occur. The horizontal component of the friction force plus the horizontal component of the normal force determines how much yaw-resisting force is generated.
When the TT attempts to swing away from the centered position, the cam on each side of the A-frame will attempt to move away from the center of the inverted "V" formed by the sloping surfaces at the end of a bar. When the cam attempts to move away from the center of the V, the horizontal component of friction force and the horizontal component of normal force both act in the same direction to resist movement between cam and bar and, therefore, resist relative yaw.
When the TT attempts to swing back toward the centered position, the cam on each side of the A-frame will attempt to move toward the center of the V. When the cam attempts to move toward the center of the V, the horizontal component of friction force and the horizontal component of normal force act in different directions. The friction force, in this case, tends to prevent the cam from returning to the centered position. The normal force, in this case, tends to assist the cam in returning to the centered position.
Depending on coefficient of friction and the slope angle of the end of the WD bar, the "self-centering" effect of the normal force might exceed the "slip-resisting" effect of the friction force; and the forces on the cams would tend to recenter the TT.
With the Dual Cam, the force which acts to prevent the TT from swinging away from the centered position will always be greater than the force which acts to prevent the TT from returning to center. With the Equal-i-zer and with friction bars, the force which resists returning to center will be the same as the force which resists moving away from center.
At least, that's the way I see it.
Ron
RE: Height Sensing Brake Proportioning Valve
Ron, I have to disagree. The purpose of the W/D hitch is to transfer tongue weight to the front axle. Any weight moved forward reduces the rear squat.
Jim,
I fully agree that the purpose of the WD system is to decrease the load on the rear axle and increase the load on the front. I also fully agree that a decrease in rear axle load will decrease the rear end squat.
What is it that you disagree with?
Ron
RE: Height Sensing Brake Proportioning Valve
If the load on the rear springs increases, the rear end will "squat" and the proportioning valve will sense the amount of squat.
The WD system reduces the amount of load on the rear springs and, therefore, reduces the amount of squat. The proportioning valve still senses the actual amount of squat and, therefore, will respond to the actual amount of load on the rear axle.
The WD system will not negate the effect of the proportioning valve. If you add 1000# to the TV's rear axle as a result of cargo in the TV or if you add 1000# to the rear axle as a result of having a TT hooked up with WD applied, the proportioning valve cannot tell the difference. It simply responds to spring deflection.
However, if you use air bags or other means of increasing the effective spring stiffness, you will affect the action of the proportioning valve.
Ron
RE: Hensley Arrow or Equalizer Hitch?
The Dual Cam HP sway control systsem is not a friction based system as the others.
According to the REESE Dual Cam High Performance Sway Control Installation Instructions,
9. Do not use grease on cam and cam arms. A light coating vaseline may be used to reduce noise. The Dual Cam was designed to use metal-to-metal friction. Heavy greasing of the cam and cam arm surfaces will affect performance. If noise is offensive, a very light coating of lubricant, such as Vaseline, may be used. Tongue weights over 1,200 lbs., may require a light coating of lubricant to reduce friction and prevent excessive wear.
(Underline added for emphasis)
The Dual Cam generates friction force in a different way and at a greater magnitude than does a "friction bar".
Ron
RE: The effects of uncontrolled sway.
---A side not about trailer brakes. I had just topped a hill and had someone pass when it turned to two lanes. He cut in very short then put on the binders. I had to hit my brakes pretty hard and then the pedal went to the floor. Master cylinder failed. If it had not been for the boost feature of the Prodigy brake controller I probably would have rear ended the unit in front of me.
You were fortunate to have been using a deceleration-sensing controller instead of a pressure-sensing controller when your master cylinder failed.
Ron
RE: Expedition/SUV Wheelbase
---It seems that when the question of trailer length comes up, smart people quote “4 inches of tow vehicle wheelbase above a 110 inch minimum for each foot of trailer length over 20 feet.”
If by "smart", you mean "informed" -- I don't know of anyone who is informed as to the basis for the "rule of thumb". As far as I can tell, the "rule" is something which was published many years ago with no explanation of either the data on which it was based or the methodology which was used to derive the relationship.
---I am assuming that ‘rule of thumb’ is total trailer length so my 25’ 25011s is really 27’ from hitch to bumper.
Again, I think nobody knows if the relationship pertains to the total length or only the body length.
According to the relationship, a 130" WB 3/4 ton Suburban should not tow a TT longer than 25'. However, there seems to be large numbers of such vehicles towing TTs of 30' and longer without problems.
Ron
RE: The 10% min Tongue weight rule - Why?
---The same principle works with a trailer. If you put the load too far back in the trailer, the sideways force it generates when anything gives the trailer a little sideways push will overcome the tires' ability to hold the trailer stable. The result is sway.
I guess I don't understand your analogy.
If you have the center of gravity farther back (toward the axles), you will have more weight on the TT's tires.
If you have more weight on the tires, the tires will provide more resistance to lateral movement (sway) of the of the TT.
Ron
RE: Relationship Between Wheelbase and Max TT Length
Here is some info on what you are lookng for.
Length calculations
Hope this helps.
Dave
Dave,
Have you ever tried to contact RV Consumers Group to see if they can provide any background information and data to support their "formula"? I've sent two emails and received no response.
If we're going to continue to cite this "formula", it would be good to have some knowledge about the basis for it.
Ron
RE: The 10% min Tongue weight rule - Why?
And the more searching into this the more depth I myself understand into the other factors that are in the equation that can have as much effect as tongue wieght in controlling TT yaw. Actually if we could make the TT tongue longer would help all by itself. I'll try to find it again in the NHTSA file Ron G linked us to, but about ~ 18" to 2 foot of more tongue length can come out to about 5% less needed tongue weight to accomplish the same yaw damping.
John,
In the post mentioned previously, I derived a theoretical relationship for TW% which depended only on the tongue length (A-frame length) and the body length of the TT. The relationship assumed the mass of the TT was evenly distributed over its length.
The relationship is
TW% = 100/(1 + /)
where c = the length of the A-frame and L = the length of the TT body.
For some typical values of c and L, the relationship shows that a 2' increase in length of the A-frame will cause the optimum TW% to decrease by about 3-4 percentage points.
Ron
