Forum Discussion

Bendder's avatar
Bendder
Explorer
Sep 04, 2014

PullRite TT hitch questions Update Installed Pic's

New to the forum and I have questions about the Pull Rite travel trailer hitches I have a complete hitch set up that I got for $75 and am wondering about some of the forces involved. I am by no means an engineer and don`t have the math skills to figure this one out. I have included a crude diagram of all the distances and forces that I know. What I would like to know is the downward force at the pin by the diff and also the forces on the bearing rollers? any help would be appreciated

Thanks
Mark

[img][/img]

16 Replies

  • Thanks all for your reply's and yes I realize I got a great steal of a price. I have been cruising the internet adds for some time looking for one of these. I traveled 1000km return to go get thisso even including $180 of gas it's still a great deal. The last prices I saw for one were about $1800 CDN Looking forward to getting itall up under the truck. I think I will relocate my truck spare to under the TT along with the TT spare (I hate the Spare way out back on the bumper) Truck onlu gets usd to pull the TT and boat anyway. I`ll take my chances the odd time I do something else with the truck (not often)

    Ron, thanks for the equasion for the forces. I had not thought about the forexerted by the WD bars down on the hitch ball but yes that would be true. From what I have read in the owners manual for the hitch (yes I did get everything the owner had from the time of purchase even a sales broshure) I will need to adjust the WD bars untill there is just a slight force on the lower bearings. I`ll need to take some time to set everything up but I don't mind. I will try to document everything for all to read. I am looking forward to a trip to the scale also to see any differences that will result.

    I`ll keep you all posted
  • Bendder wrote:
    ---What I would like to know is the downward force at the pin by the diff and also the forces on the bearing rollers? any help would be appreciated
    Mark, welcome to Open Roads Forum.

    You can get a good estimate of the downward force at the pin by using the following leverage equation:

    Force * (61.5" + D) = TW * D or Force = TW * D / (61.5 + D)

    where 61.5" = distance from pin to ball per your diagram,
    D = distance, in inches, from ball to midpoint between TT's axles, and
    TW = tongue weight.

    The above equation assumes there is no significant vertical force exerted on the roller bearings.
    It is my understanding that the WD bars should be adjusted to minimize this force.

    For your information, this thread contains a wide-ranging discussion of the PullRite hitch (and a lot of other stuff).

    This web page by ORF member, Steve Rankin, shows his installation process.

    BTW, you did a great job on the PullRite diagram -- except the downward force on the ball (which you show as 1000#) is equal to the TW plus the downward pull exerted by the two lift chains minus the amount of load transferred to the TT's axles.
    For your example the downward force on the ball might be approximately 1000+2000-200 = 2800#. (The 200# depends on "D" in the above equation.)
    The upward force exerted on the hitch head via the front ends of the WD bars would be 2000#.
    The net force exerted on the hitch head, and transmitted to the pin, would be about 800#, if we ignore the weight of the drawbar which extends from hitch head to the pivot pin.

    Ron
  • You got yourself a steal and what is considered by many to be the best hitch money can buy.

    If our member Ron Gratz comes by, I am sure he can give you the numbers you are looking for. In the meantime, you might want to give a good look at this thread by him that is stuck at the top of the forum. Some of the questions you asked may be answered in that threads first post.
    Barney
  • Great hitch and you got a super price! Don't worry about force on rollers if they are in good shape. I had a full size Bronco with the Pull Rite back in the late '80s, pulled a 26' StarCraft TT from FL to AK 18K never a problem. You will (with practice) get into sites easier and amaze others because they really work. No sway at all even on my short wheel base because the pivot point is about at the rear axle, just like a fifth wheel. You will answer lots of questions from people about your funny hitch. Enjoy...BTW they were well over a grand in the late '80's. :) :)
  • My friend had one when he towed a race car with his Ford and also had a Lance camper in the bed at times. The torsion bars also hold the trailer straight to the hitch and the pivot is just behind the rear axles.

    I can't help you with the forces. Not sure if anyone but pullrite can answer that.