Cam vs friction sway control

[azflycaster]

Originally Posted by Gen Disarray

Since I have a Reese weight distribution with friction sway control all ready (WD bars are straight); am I correct in thinking that in order to convert to a dual cam system I would just need the cam kit and new WD bars?

It depends on which arms you have. If you have these:

you should be able to. I have the ones that are level all the way and I can not. Mine look like this:

[Boondocker]

Hey Richard,

I have the same type WD arms as yours, that is what I was talking about replacing along with buying the cams. Are you saying I cannot convert to those arms with my present setup?

[azflycaster]

You should be able to keep the head and buy the rest.
I would get in contact with them before I bought anything.
Reese-Hitches.com > America's most recognized Hitch!
It looks like you could convert for around $300 + shipping.
$150 for new arms
$140 for the DC or $175 for the High Performance

Let me know how it works out, I might do the same next...

[jcanavera]

Originally Posted by azflycaster

It depends on which arms you have. If you have these:

you should be able to. I have the ones that are level all the way and I can not. Mine look like this:

I remember I had the straight arms and there were two predrilled holes at the end. There was a bolt on cam kit that allowed you to put the needed cams at the end of the bars. If the predrilled holes are not there, you will need to buy new bars.

Jack

[azflycaster]

Thanks for the tip. They should all have the holes. That is where the U-bolt is mounted to attach the chains.

[Beginner]

Thats right. You remove the U bolt holding the chain to the spring bar and bolt on the cam adapter using the holes the chain U bolt passed through.
That is what South Jersey RV did to my old straight spring bars.
Beginner

[2airishuman]

the proposed tv is sufficiently different from it's predicessor...

that it would seem useful to TOW some with the current/old hitch configuration before making changes...

IF the question really is "difference in performance"

yes the bars/chains can be changed out to include cams...

which btw really ARE another form of friction control.

in order for the cam design to function (not the same as performance) effectively

spring bar deflection is critical.

there are zillions of posts on 'bar rating' as related to older tow vehicles and suspension stiffness.

and this is a rare situation where those posts actually DO apply.

ideal spring bar rating may be 400lbs or 800lbs or something in between.

since the tv leaf springs have been in use so long it will take some trial/effort to match the correct bars...and a scale visit

given the specific tv/trailer\driver combo it is unlikely that a significant performance difference will result during travel with the correct springs bars...

choose the wrong bars and the performance will deteriorate.

cheers
2air'

[Chuck]

yep, mine are "bolt-on" cams, too.

[85MH325]

Originally Posted by 2airishuman

which btw really ARE another form of friction control.

cheers
2air'

Ok, Joe... I'm gonna split hairs with you on this one. Friction sway controls scrub off the lateral forces applied throught dissipated heat, much like standard brake shoes in drum brakes. The brake pad material in a friction sway control device is sacrificial, just like the lining on brake shoes. The dual-cam OTOH employs friction on the faces of the cams and bars to keep the bars centered over the cams, not to dissipate force through heat. That friction is applied or relieved through the amount of pressure kept on the spring bars (trunnion bars) by the chains and snap-up hooks.

The dual cam setup isn't a friction sway control device. The nomenclature with this stuff is confusing enough without us confusing folks.

Roger

[2airishuman]

Originally Posted by 85MH325

..I'm gonna split hairs with you on this one...The dual-cam OTOH employs friction on the faces of the cams and bars to keep the bars centered over the cams, not to dissipate force through heat. That friction is applied or relieved through the amount of pressure kept on the spring bars (trunnion bars) by the chains and snap-up hooks...

no hairs 2 split, we agree. and thanks for reinforcing the point by using friction TWICE in this description of cam-ology!

cheers
2air'

[85MH325]

So, then the HaHa is also merely a friction sway control?

C'mon Joe... this stuff is confusing enough without confusing folks on purpose.

Roger

[2airishuman]

Originally Posted by 85MH325

So, then the HaHa is also merely a friction sway control?...

what's a haha?

friction control is somewhat like a rusty 2 way kitchen door hinge that swings (sways) to and fro past the center position...

it 'might' stop near the center line IF the cook swinging the door is skilled enough...

a cam with tensioned spring bar is somewhat like that same rusty hinge, with a notch at the center point...

it takes more effort to initiate movement out of the notch but it has a better chance of stopping when it swings back through the notch...

either way the door will swing if the cook tries to leave...

a haha keeps the customers from getting TO the cook, since it locks the door.

how's that for a simple (plus i'm eating right now) analogy?

cheers
2air'

[85MH325]

A better analogy for the dual cam is the double sprung hinge in a bar door. It has resistance to opening either way, but when appropriate allows the door to swing to one side or to the other and then centers itself with continued resistance to opening either way.

a haha keeps the customers from getting TO the cook, since it locks the door.

using friction. But neither are friction sway control devices. Leave it alone... it doesn't belong in this thread.

Roger

[2airishuman]

leave what alone? you asked the question.

i maintain that IF difference in performance is the issue...

...it would seem useful to TOW some with the current/old hitch configuration before making changes...

given the specific tv/trailer\driver combo it is unlikely that a significant performance difference will result during travel with the correct springs bars...

regardless of e-i-zer 4-point friction control or add on friction bars or cam/tensioned devices or a friction tightened ball/cap...

none of these 'control sway' .

what they really do is attenuate the DRIVER RESPONSE to yaw forces or

delay driver awareness of wandering trailer movements (sway) from the bow wave.

the trailer STILL does sway, the ossilations can be seen clearly from behind or overhead.

EVEN when the driver declares "i didn't feel any sway" the movement is there.

with sufficient exposure/practice and stiff tires (more friction), proper loading, wheelbase and steady speed and NO steering correction...

the sway event passes.

the difficulty is learning how NOT to react (sort of like learning how not to reply) to the lateral sensation.

friction or cams assist, by reducing the driver's perceived NEED to correct (or over correct) with steering or braking.

and again the reference is ONLY related to passing turbulence from bow waves...

not other events like a blow out or off pavement or stuck brake or avoidance maneuver or mass contact event.

each of those other towing calamities can reveal the strengths or weaknesses of 'sway control' designs in different ways.

cheers
2air'

[dwightdi]

The Reese people tell you to "do not lubricate the cams". There is metal to metal contact and lots of pressure and friction between the cams and the cam followers, so if you do not lubricate the cams, the Reese Dual Cam is actually both a friction (energy disipating) and a self centering Hitch. Reese used to give you replacement cams if you wore them out but now they sell them to you. If you are running around with worn flat cams, you have only a friction hitch. You need to use Reese WD bars that are low enough rating so you give them a signifigant bend when transferring the proper amount of load to front wheels. If you use too stiff a bar, the cam follower will lose pressure on the cam when you go over a signifigant bump with your rear TV tires. You therefore will lose the twin cam effect. If you just have a frictional system like the frictional dampener, weight distribution is a separate function and is not dependent on the amount of weight being transfered or the rating of the bars. With Equalizer system you have the preload friction from the retaining J clamps as well as the friction from the base of the unit which is a function of the amount of weight being carried by the bars. You therefore would have higher frictional dampening when the TV rear wheels are going into a dip in the road. It is funny that Equilizer does not tell you to reduce the frictional preload on the bars in wet conditions as Reese does.

[85MH325]

Originally Posted by 2airishuman

what they really do is attenuate the DRIVER RESPONSE to yaw forces or

delay driver awareness of wandering trailer movements (sway) from the bow wave.

and again the reference is ONLY related to passing turbulence from bow waves...

2air'

Ok, Joe... now you've really gotten me confused. You've seen my mini moho. I get moved around in it exactly as you describe when I'm NOT towing by the bow waves of passing trucks on the interstate, particularly here in Iowa in 30-40 mph winds. You're telling me I'm experiencing sway? In a motorhome? NOT towing?

I don't think so. That bow-wave effect is normal, especially in any high-profile vehicle, and the trailer/tow vehicle combination experiencing some movement as a unit under those circumstances is normal, and that's NOT sway.

Your experience in with the inherent stability of an F350 four-door with a 34' tri-axle in tow can't be compared to the average trailer owner here. It's just not the same experience.

Roger

Roger

[2airishuman]

Originally Posted by 85MH325

I get moved around in it exactly as you describe when I'm NOT towing by the bow waves of passing trucks...You're telling me I'm experiencing sway? In a motorhome?...
That bow-wave effect is normal..

nope, i am not suggesting the moho 'sways' in response to bow waves but it can move around

it may wander or lean a bit depending on the force size, speed difference, ruts, associated cross winds and driver steering input...

again this all relates to how sway is defined and how drivers interpret the vehicle movements they experience.

1. when a passing bow wave makes contact with the trailer rear...

2. the trailer rear moves laterially away, pivoting slightly on the tires...

this happens to some degree with every bow wave and trailer given enough force.

because the trailer tires are NOT at the corners (but somewhere more central) the trailer pivots slightly...

in other words the trailer ROTATES with the front moving toward the wave source...

3. this rotational force pushes laterially on the tv rear end/drive axle...

basically this explains YAW; given my limited comprehension of this topic...

again this happens with virtually every trailer/tv combo

these movements can be measured and seen, even the small ones and ARE sway (as i view it)...

BUT the driver may not FEEL/EXPERIENCE them all.

and with enough exposure/practice the driver may reset his/her INTERNAL sensory inputs such that they "no longer feel" it...

more extreme examples (of adapting sensory interpretations) are pilots, gymnasts, ice skaters and others playing with lateral, rotational or g forces routinely.

anyway, as the trailer nose pushes laterally on the back of the tv...

4. the driver may 'correct' by steering left or right. ((lets ignore the brake pedal))

again steering response/direction is based on experience/learning, how quickly it all happens, attention and how MUCH lateral force the driver perceives.

5. the bow wave continues to pass as the entire trailer enters it, as does the tv...

so the rear lateral push changes to a full side push and then a rear lateral pull (or suction)....

so now the trailer pivots the other direction with the rear moving toward the wave...

6. again the trailer exerts yaw force on the tv but now in the opposite direction

7. again the driver may/may not react with steering

now the trailer/tv exits the bow wave with each lateral push repeated again in reverse order (i think)

depending on trailer/tv length and speed differential, mass, wheelbase and ALL of the other physical issues...

the bow wave impact/effect may occur in a fraction of, or several seconds...

my view of 'sway' or the yaw effect is that this happens EVERY TIME, and all that trailer wiggle IS sway.

((travel trailers are different than most vehicles, since trailers have 2 really long overhangs and centrally placed pivot/contact points and no direct steering axle))

ALL single point freely moving hitches (not the haha) allow this 'sway' to happen, but attempt to attenuate the forces or the sensation of the YAW forces...

so drivers don't 'feel' it and over react, before it passes on and away.

which brings us back to the moho...

with tires at the corners and NO articulation mid ship, the moho is pushed differently by the bow wave.

with steering at the front and NO midship articulation, the driver input usually will move the rig in parallel to the passing bow wave....

so while bow wave forces are 2b expected...

the movements of JOINTED 2 piece rigs and a one piece long vehicle are different. one is sway (always) and the other is not...

driver response may make things WORSE in either rig...

now i think your view of sway (defined in another thread) is more limited/specific....

along the lines of bigger movements, potentially uncontrolled movements and so on...

Originally Posted by 85MH325

.,,,Sway, OTOH, is an oscillation of the trailer (but not the tow vehicle) back and forth across the centerline of the tow vehicle/trailer axis that can't be controlled while driving at a constant speed without applying the trailer brakes or taking other extraordinary measures. Certainly wind loading can be a factor in initiating sway, but it isn't the cause, and it is possible to experience sway without losing control...

so our BASIC difficulty is that we do NOT define/view sway in the same terms...

make sense?

cheers
2air'

[85MH325]

Originally Posted by 2airishuman

now i think your view of sway (defined in another thread) is more limited/specific....

along the lines of bigger movements, potentially uncontrolled movements and so on...

so our BASIC difficulty is that we do NOT define/view sway in the same terms...

make sense?

cheers
2air'

The things you're defining as sway aren't sway, period. They can cause sway, but they're not in and of themselves sway. Here's where the definition of terms is so critical. Just as a friction sway control is NOT a sway bar, neither is being pushed by a side wind, or a truck's bow wave sway.

All of those may induce and the driver's response to sway may, as you've said, cause sway, once induced, to worsen; but those inputs are not sway in and of themselves, no matter how much you talk about them as sway.

Folks who have never had a sway episode may interpret those inputs as the onset of a sway episode, but in fact that isn't the case. Folks who have had a sway episode know exactly what the difference is between normal and routine steering input issues and a sway episode. I presume that since you're describing that routine input from road conditions as sway, that you've never actually been involved in a sway episode in your towing career?

The bow wave effect is NOT sway as evidenced that I can experience it in a vehicle that is not towing (e.g. my moho). That you typically don't feel it in your trailer towing rig is wonderful, but has nothing to do with sway control. That has more to do with the aerodynamics and inherent stability of the rig (tire pressures, loading, and your rig's inherent resistance to outside forces etc.).

Now, whether or not that phenomenon initiates a sway episode is a function of the inherent stablility or instability of the rig. THAT's what I've been trying to get across over all these posts in all these threads.

Sway is the repeated travelling of the trailer over the center axis of the trailer/tow vehicle that is uncontrollable through regular driver input.

This

YouTube clip

illustrates sway and its effect on a tow vehicle.

If that type of event is not what you're talking about when you describe it as "sway" then you're mis-interpreting what's happening to your rig.

Roger

[Boondocker]

quib·ble (kwĭb'əl)
intr.v., -bled, -bling, -bles.

1. To evade the truth or importance of an issue by raising trivial distinctions and objections.
2. To find fault or criticize for petty reasons; cavil.

n.

1. A petty distinction or an irrelevant objection.
2. Archaic. A pun.

[Probably diminutive of obsolete quib, equivocation, perhaps from Latin quibus, dative and ablative pl. of quī, who, what (from its frequent use in legal documents).]
quibbler quib'bler n.SYNONYMS quibble, carp, cavil, niggle, nitpick, pettifog. These verbs mean to raise petty or frivolous objections or complaints: quibbling about minor details; a critic who constantly carped; caviling about the price of coffee; an editor who niggled about commas; tried to stop nitpicking all the time; pettifogging about trivialities.

From: quibble: Definition, Synonyms and Much More from Answers.com

[2airishuman]

Originally Posted by 85MH325

The things you're defining as sway aren't sway, period...
Sway is...

again we agree here that a clear definition of terminology is useful...

but a basic dictionary doesn't contain YOUR definition of the s word.

the automotive and engineering references i've read don't include your definition of the s word either.

your working definition may be easy to understand but that doesn't make it absolute or remotely correct for that matter.

there are some godawfulpoorlywrittenwhydidiwastemoneyonthis rv books that get close to your definition...

but i'm not using them. my reading of rv specific popular books is jaded.

so lighten up on declaring what is what, period without solid references or a professional consensus...

sway: middle english from the low german swajen for 'be blown to and fro' and the dutch zwaaien, 'swing, walk toteringly'

sway: 1. move or cause to move slowly and rhythmically backward and forward or side to side 2. control or influence (a person or course of action)

and clearly i've NOT swayed you one iota!

i've tried to move the terminology toward using 'yaw' which seems to have a narrower spectrum of definitions...

yaw: to twist or oscillate about a vertical axis.

and because that is a closer description of what the trailer DOES to the tow vehicle.

also tried focusing on the "performance" concept since the performance difference (without including the driver) may be negligible...

those efforts has been ignored mostly in the replies. (thanks dwightdi)

so i'm NOT playing word games or trying to confuse...

exactly the opposite. PERIOD

Originally Posted by 85MH325

I presume...

it is often (always) a mistake to presume.

sadly i've been jack knifed and had other towing calamities while destroying a lot of stuff.

although i'm sure my accident career wouldn't qualify by some folks standards...

and i'd like to keep it that way.

Originally Posted by 85MH325

...since you're describing that routine input from road conditions as sway...

again my notes here are on 'bow wave' and yaw forces, not road conditions...

i provided a reasonable and fair reference at the BEGINNIG in post 2 here...

Understanding trailer sway

it is easy to understand, better written than my posts and connects directly to 'performance' issues for the dampening devices.

in another thread i linked scholarly, focused and published papers on these issues, that also include clear definitions of terminology...

wonder IF those were read? hmmm.....

so, it seems NOW that the thread is shifting to a more personal, directed, guttural tone.

that's too bad, but not to worry...

i am not easily swayed either

cheers
2air'