So how do ya know....

[wave man]

... if your ride/hitch etc is just too rough when you're towing your trailer..? Things that I should be on the lookout for from your personal experience or something you've heard from another.

[uncle_bob]

Hi

When the trailer separates from the TV, that's too rough.

More to the point, if it's rough enough to bother you - slow down.

How do you measure roughness? Is it a peak to peak displacement in inches? Is it an RMS acceleration? What measurement bandwidth should we use? How do we calibrate your instruments vs what somebody else has? Very few people are set up to actually do a numeric measure of what's going on.

Saying something like "when it gets pretty rough, that's to far" really does not say much that is useful. It still comes back to what I'd call rough vs what you would call rough. Hop in a car or plane with a pro driver or pilot. What he calls "exciting" likely will have you reaching for the barf bag.

Road condition / design is a big variable. What feels fine on one road may feel really crazy on another similar road. Taking that out of the process .... not easy at all. Again, it's a try it and see sort of thing. If it feels nutty, slow down.

Best case in a "couple feet high off" the ground 4x4 truck with mushy springs and junk factory shocks may be at some level. The same level might be totally wrong in a low to the ground SUV with much better suspension. What you are running matters in all this.

I realize this isn't very useful. I would suggest it goes back to the other thread on the same basic topic. You need to get out and do some driving. If you feel you need to, take some lessons. There are a variety of driving schools out there. It's something you can experience. There really isn't a way to quantify it exactly. Start out slow and careful. Work up from there.

For others not following along with the series of threads. The previous thread on adjusting hitches might be worth taking a look at.

Bob

[DoubleR]

What part of Houston are you in? I’m in Kingwood and wouldn’t mind spending some time discussing some of your questions. We drove to Minnesota in July to pick up our 2014 FC 25FB Twin, a lifelong dream of mine. Always willing to help and i’m retired so during the week works for me.

[PKI]

Maybe -- If stuff ends up on the floor, it's too rough. If it's uncomfortable for you, it's too rough. If rivets are failing, it's too rough. This is like lots of things in life. It's OK if you are happy and not good enough if you believe it to be a problem .... because you have to fix it with effort, restraint, or cash. If you don't believe it is problem, dealing with the issue will be painful. And if it is a problem and you don't deal with it, the same.

Good luck with the investigation. Travel safe. Pat

[ROBERT CROSS]

Loose interior Rivets....heads on the floor.

Bob

[GM Airstream]

If you don't know rough... then you shouldn't be pulling anything... acceleration, RMS, and all the rest... wow.. really cutting a fine line... as to what is acceptable and not... ouch...

I just go with what the bottom half feels... and try to smooth it out... by going slower or faster.. depending on the width of the canyon I'm jumping... go figure

I usually wait till the other half starts saying something.. as that too is a good indicator.. because they can't sleep... while going down the road... or seeing the words on the pages.. in the book they are reading...

So no need for anything fancy... and its a automatic alarm... that doesn't require batteries or (well....) has variable volume and alerts... 'high maintenance' scientific understanding... or unknown limits... they let you know similar to getting lost... don't need a GPS to tell me that either... are we having fun yet... usually works for the reset button...

Now what were we talking about here ? Oh ya trailer hitch failure due to sever vertical movement.. hmmm...

[rmkrum]

My casual definition of the "slow the heck down, it's too rough!" point was when I could see the front of the Camry I was towing on a dolly pop up in the rear windows of the '79 GMC van we were towing it with...

The ride, we discovered later, had BENT the 2" cross tube on the class 4 hitch on the van....

Yup. a little too rough.

[Air4563]

If you are on the road in Louisiana or Wisconsin it is too rough.

[uncle_bob]

Originally Posted by Air4563

If you are on the road in Louisiana or Wisconsin it is too rough.

Hi

I'd add most of Pennsylvania and Indiana to that list ....

Bob

[Minno]

We put an Air Safe hitch on our set up. Heavy as heck (like 95lb) , and not cheap, but works like a charm to uncouple the truck ride from the trailer ride. No more open doors in the trailer, etc. and feels much better in the truck. Worth the money, in our book.
There's a few roads in Minnesota you can add to that list...

Kay

[Bigventure]

What I think is going on is your spring bars are to heavy a weight for what your transferring. When your hitched up you should be able to step up on the hitch and when you jump up and down the hitch should flex up and down. If it doesn’t then the spring bars are to heavy. Also towing with real heavy duty truck will not allow any flex and it will translate into the trailer getting beat to death.

[m.hony]

Sometimes there is nothing you can do to your rig.
Sometimes the roads are just that bad.
If your rig rides good on a good road...
If your rig goes bump, bump, bump on an old road with concrete expansion joints that has been neat to death by heavy truck traffic...
A 1/2 ton truck towing a 30' with a full fresh water tank generally tows very smoothly, but there are those certain bad roads.

[uncle_bob]

Hi

It's not always bumps that go "thump" that are the issue. Pavement (at least around here) gets beat up a number of ways. Fast dips and rises are not at all uncommon. You don't see them, but you do notice them with a trailer. Just as your trailer responds to them, so do large trucks. The result is more beating of the pavement and more dips and rises in the road. Let this go on for a few ... errr ... decades ... (welcome to Pennsylvania ...) and you are bouncing along for hours.

Like it or not, with a 10,000 LB trailer and 1200 LB on the hitch, you *will* transfer energy from trailer to TV. With an 8,000 LB TV you will transfer energy back to the trailer. That back and forth is enough to feel under the right conditions. Would you expect to notice a half ton of sand dropping into the back of the truck? Of course you would notice it !!! Same thing with the trailer rocking a bit.

On top of this is the question of "how many axles?". Tipping a trailer back and forth on one axle is pretty easy. Add a second axle and it gets a little bit harder. Toss in a third and it is harder still. Space out the axles and it gets tough. We like space inside the trailer, devoting that space to wheel wells is not popular. We make trailers longer and that does not help things.

For a real snoozer, ask Mr Google about calculating second and third moments of inertia ... time for a nap ( simple answer = keep all the weight at the axles). That stuff gets into this whole process pretty quickly.

Lots of fun !!!

Bob

[GM Airstream]

Well if you look at the TV and TLR as being one long beam.. so to speak.. i.e if you had the TLR welded to the ball... I think you will see more bumping...

But... that is not the way the towing is set up... The TV is pretty much the same as if you were driving it alone... the trailer becomes its own with the wheels being the back end.. so to speak of the vehicle... only the hitch with the equalizer bars removes the weight from the trailer..and places it on the TV...

So basically the TV articulates with its normal wheels... but the eq then adds the fwd wt of the trailer to its wheels... from their the TLR articulates from the ball.. and the rear wheels become the moment point...

So if you say that the trailer adds to the bumps.. it does but not to a large extent...

I know that airstream and reese had a add where they took the rear wheels off a front wheel drive car and showed it going down the road.. the equalizer bars kept the rear of the TV up... but what they didn't show you was that the eq bars were welded to the arms... to keep the vheicle from bowing in the middle at the hitch point... otherwise it would go oblong down the road

Now I am not saying that you can't over hitch the trailer and have it tranfer the moment to the TV.. but if its set up correctly.. you should get action on the ball and the larger wt transfer just to the rear wheels /suspension of the TV...

That is the way I was told it should be...

but... their is no relief for the forward and backward loading that goes on when the TV and TLR go through a pot hole...

First you get acceleration as the TV goes in... pulling the TLR with it...Then when the TV starts up out of the hole... it slows down...requiring more power... and you will get a reduction in speed

The TLR then absorbs the acceleration and energy frin the TV going into the whole.. and provides it back to the TV when it climbs out of the hole..

when the TLR goes into the hole... (behind the TV) ... it again gains energy and speed...pushes the TV ...
when it comes out of the hole... it requires more energy and so it pulls on the TV for it...slowing it down

Thus we have a longitud'al motion going on as well as the vertical one from the wheels going in and out of the hole...

it then seems to amplifie the forward/reverse moment... Thus a acceleration and then a reduction in speed going into and out of the hole...

So is it vertical movement or horz movement that the pax feel in the TV... and relates it to jumping down the road.. ???

Some thought about this ?

[uncle_bob]

Originally Posted by GM Airstream

Well if you look at the TV and TLR as being one long beam.. so to speak.. i.e if you had the TLR welded to the ball... I think you will see more bumping...

But... that is not the way the towing is set up... The TV is pretty much the same as if you were driving it alone... the trailer becomes its own with the wheels being the back end.. so to speak of the vehicle... only the hitch with the equalizer bars removes the weight from the trailer..and places it on the TV...

So basically the TV articulates with its normal wheels... but the eq then adds the fwd wt of the trailer to its wheels... from their the TLR articulates from the ball.. and the rear wheels become the moment point...

So if you say that the trailer adds to the bumps.. it does but not to a large extent...

I know that airstream and reese had a add where they took the rear wheels off a front wheel drive car and showed it going down the road.. the equalizer bars kept the rear of the TV up... but what they didn't show you was that the eq bars were welded to the arms... to keep the vheicle from bowing in the middle at the hitch point... otherwise it would go oblong down the road

Now I am not saying that you can't over hitch the trailer and have it tranfer the moment to the TV.. but if its set up correctly.. you should get action on the ball and the larger wt transfer just to the rear wheels /suspension of the TV...

That is the way I was told it should be...

but... their is no relief for the forward and backward loading that goes on when the TV and TLR go through a pot hole...

First you get acceleration as the TV goes in... pulling the TLR with it...Then when the TV starts up out of the hole... it slows down...requiring more power... and you will get a reduction in speed

The TLR then absorbs the acceleration and energy frin the TV going into the whole.. and provides it back to the TV when it climbs out of the hole..

when the TLR goes into the hole... (behind the TV) ... it again gains energy and speed...pushes the TV ...
when it comes out of the hole... it requires more energy and so it pulls on the TV for it...slowing it down

Thus we have a longitud'al motion going on as well as the vertical one from the wheels going in and out of the hole...

it then seems to amplifie the forward/reverse moment... Thus a acceleration and then a reduction in speed going into and out of the hole...

So is it vertical movement or horz movement that the pax feel in the TV... and relates it to jumping down the road.. ???

Some thought about this ?

Hi

What you have is a "coupled resonator system". The TV has it's tendency to "resonate" (pitch) as it goes over a series of bumps. The trailer also has it's own tendency to do the same thing. Each has properties in multiple directions.

The coupling is via the hitch. You can just let it hinge (as with a conventional ball or you can do something more exotic. You can add damping at the connection. By stiffening the connection, you can transfer weight and "tune" some of the resonances a bit.

If you happen to come up with a "high Q" ( large amplification) resonance things get rough quick. That's rare with modern shocks. The gotcha is that the coupled combo will show you the resonances from both elements *and* peak things a bit. That's why it seems so weird.

If you happen to speak French and need to take a nap, the papers on all this go *way* back.

Bob