Dual Cam Setup

Ron Gratz wrote:

JBarca wrote:
Be back later after I get some more WD bar displacement distances when the hitch goes through a turn with and without the DC installed. We can then start putting estimates on the chain forces.

John, I'm not sure how you're planning to measure displacement distances.

A relatively simple way of getting a good estimate of WD bar load is to clamp a straightedge (e.g. 1/2" x1/2" angle iron) to the underside of the front end of a WD bar. A straight edge is indicated by the red line below.
The perpendicular distance (blue line) from the rear end of the straightedge to a point near the rear end of the deflected WD bar is directly proportional to the load applied to the WD bar.
A beam-type torque wrench uses the same principle.


You could use your hydraulic load cell to exert an upward force on the detent in the WD bar to calibrate the load-deflection curve for any given bar.

Ron

Ron,

Glad to see you found this thread. I was getting close to PM'ing you soon anyway. We can use your special talents on this one.

mrekim's frame failure brings up a number of topics about the Reese DC and snap up brackets and then his new camper frame that failed under such little use so quickly. His is the fastest/worst I have seen and he is not even fully loaded yet...

I have done some more "tests" in the yard today and will post shortly. Your question about spring bar deflection and what force that creates in the WD chain is at the heart of this recent discussion. I have not thought about using your straight edge concept. That for sure has me thinking and the curiosity may get high enough I'll repeat the tests from years ago.

Maybe you remember the post we both talked about spring bar deflection. I have searched now for over an hour and cannot find it...:( Yet you linked it in to a thread not that long ago... so maybe you have it book marked.

I know the dates... this thread What happens to a WD hitch in a turn brackets the time frame just before the WD bar deflection tests. We were talking about it. Just I cannot find the post a few days later. Maybe your memory or search ability is better from 6-15-2006 then mine.

Here are my pics from the testing.


I used the TT frame as a datum to measure the WD travel distance per force applied


And created this chart


Due to lack of any other data, I was going to use that as an estimate. I know there is a small level of error in it as once I start approaching the TW of the camper the WD shank starts to articulate. Using your method may help eliminate some of it. I now have a different camper and a lot more TW so I may be able to get a 1,200# bar actually to 1,200#.

If we can figure out the spring bar constant per amount of deflection this will help add better data to discussion.

I'm preparing my new findings of today. Will post soon.

Thanks

John