ProPride 3p hitch

93Cobra2771 wrote:

Huntindog wrote:


Google the Hensley "bump" for lots of reading on this.

Basically if one has to suddenly hit the brakes while initiating a turn, the 4 link sees this as a sway event and will not allow the pivot between the TV and TT to occur. Something HAS to give. Sometimes it is the receiver.

YMMV

I had just such an emergency situation (hard braking while in a curve at approximately 40mph). I can say that nothing gave in my case I successfully navigated the curve while dodging an idiot cutting in front of me. Trucked/TT braked without any hint of the TT coming around on me.

The Hensely bump is totally unrelated and can occur when TV slows down faster than the TT. The linkage will swing to one side or the other and "bump" when it reaches the end of the travel. It can easily be remedied by making sure brakes are set up on the TT to "lead" the TV. Most commonly, it occurs on TV with engine brakes (diesels), or newer TVs with good tow/haul modes (I can initiate it on my 2011 F150 in tow haul mode in the right conditions).

One of the members here, (burbman?) had his receiver destroyed at a very low speed. Probably less than 15 MPH.
He was almost home. Was making a left turn into his neighborhood. As he accelerated from a stop while turning, he had to suddenly hit the brakes...Yes the TV stopped faster than the TT.. And TT brakes do not lead the TVs. That is a popular thought as they can be set up to brake more aggressively than the TVs, but they take the signal from the TV...Not the other way around.

Glad you made it thru your incident OK.

Huntindog wrote:


Google the Hensley "bump" for lots of reading on this.

Basically if one has to suddenly hit the brakes while initiating a turn, the 4 link sees this as a sway event and will not allow the pivot between the TV and TT to occur. Something HAS to give. Sometimes it is the receiver.

YMMV

I had just such an emergency situation (hard braking while in a curve at approximately 40mph). I can say that nothing gave in my case I successfully navigated the curve while dodging an idiot cutting in front of me. Trucked/TT braked without any hint of the TT coming around on me.

The Hensely bump is totally unrelated and can occur when TV slows down faster than the TT. The linkage will swing to one side or the other and "bump" when it reaches the end of the travel. It can easily be remedied by making sure brakes are set up on the TT to "lead" the TV. Most commonly, it occurs on TV with engine brakes (diesels), or newer TVs with good tow/haul modes (I can initiate it on my 2011 F150 in tow haul mode in the right conditions).

I remember years ago when the Hensley website compared the feeling of towing with their hitch to driving a box truck. The side winds would still be there and felt, but no sway as the box truck would just move over a little as a unit.. And the Hensley would react the same as sway would be impossible.
I remember thinking at the time what tremendous force that would put on the receiver. Think about the connection between the cab and the box of the box truck. A solid frame, many times stronger than any receiver hitch.

Then I saw some pictures of receivers destroyed when using one.

Google the Hensley "bump" for lots of reading on this.

Basically if one has to suddenly hit the brakes while initiating a turn, the 4 link sees this as a sway event and will not allow the pivot between the TV and TT to occur. Something HAS to give. Sometimes it is the receiver.

Bottom line is that there seems to be drawbacks with all types of sway control.
Myself, I would rather put my $$$$ into a VERY capable TV, and not need so much sway control than a unforgiving design that can break recievers.

YMMV

stripit wrote:
If the side forces with a conventional hitch are less, why do folks have to make steering corrections to a tow vehicle when towing a trailer with a conventional hitch and do not need to make them when towing with a ProPride 3P or Hensley Arrow?

Aren't the forces that cause the steering correction coming from side forces on the trailer and transferred through the receiver?

I didn't say anything about side forces on the trailer.
I was talking about yaw-axis torque applied to the receiver.

To answer your first question --
The lateral force applied to the ball of a conventional hitch on a Suburban acts at a distance of about 65" behind the rear axle.
The steering torque (in lb-inches) on the TV would be about 65 times the lateral force.

With a four-bar-linkage hitch, the lateral force acting on the ball is "projected" forward to a point about 22" behind the Suburban's rear axle.
The steering torque would be about 22 times the force.

If the lateral force is the same for the two cases, the steering torque with the conventional hitch would be about three times as great as for the 4-bar hitch.

Ron

Ron Gratz wrote:

Ridgerunner29 wrote:
Ron, I understand your thoughts on this. Has anyone actually measured the horizontal forces applied to the receiver during a sway situation with a Propride or Hensley hitch? Have any engineers performed any sort of engineering analysis of the expected forces during a sway event with one of these two hitches.

I'm not aware of any published data or engineering analyses of force and/or torque on a receiver during a sway event -- and, I've done a lot of looking.

Ron

If the side forces with a conventional hitch are less, why do folks have to make steering corrections to a tow vehicle when towing a trailer with a conventional hitch and do not need to make them when towing with a ProPride 3P or Hensley Arrow?

Aren't the forces that cause the steering correction coming from side forces on the trailer and transferred through the receiver?

chracatoa wrote:
I wonder if the friction is overcome how far you are of a jackknife situation.

The friction force does not disappear -- it only is diminished.

As long as there is no relative yaw velocity between TV and TT, there is no "slipping" of the friction surfaces and a state of static friction exists.

If there is relative yaw motion, there is slip and the friction transitions from static to kinetic.

The force due to kinetic friction is about 80% of that due to static.

Ron

Congrats on the purchase - we love towing with the HA and I think you'll find the same results with the PP.

Ridgerunner29 wrote:
Ron, I understand your thoughts on this. Has anyone actually measured the horizontal forces applied to the receiver during a sway situation with a Propride or Hensley hitch? Have any engineers performed any sort of engineering analysis of the expected forces during a sway event with one of these two hitches.

I'm not aware of any published data or engineering analyses of force and/or torque on a receiver during a sway event -- and, I've done a lot of looking.

Ron

Ron Gratz wrote:

chracatoa wrote:
How about the sway bars (sometimes integrated on the WD system). Wouldn't those cause lateral forces as well for regular hitches?

Integrated WD/sway bars don't cause lateral force, but they do produce a yaw-axis torque.
However, the amount of torque is limited by the amount of friction which can be generated.

If a "conventional" hitch were able to generate as much torque as can be generated by a four-bar-linkage, the "conventional" would generate as much "sway control" as the four-bar.

Ron

I wonder if the friction is overcome how far you are of a jackknife situation.

Anyway, interesting discussion! It'd be nice to have some numbers but I'm too lazy to do the math.

chracatoa wrote:
How about the sway bars (sometimes integrated on the WD system). Wouldn't those cause lateral forces as well for regular hitches?

Integrated WD/sway bars don't cause lateral force, but they do produce a yaw-axis torque.
However, the amount of torque is limited by the amount of friction which can be generated.

If a "conventional" hitch were able to generate as much torque as can be generated by a four-bar-linkage, the "conventional" would generate as much "sway control" as the four-bar.

Ron