Happijac failed while driving down the interstate!

stevenal wrote:

stevenal wrote:

Upon further thought on the subject, I believe there is a design flaw here. It's not clear in the picture, but the threads don't stop at the collar, they extend to the hidden top of the rod. The inside of the collar is cylindrical, un-threaded. The joining pin then crosses a gap from collar to shaft so that the force on the pin is a bending moment. In my experience, roll pins are used where they are subject only to shear forces such as the pin located a bit higher in the photo. I'll be inspecting my other 4500 once the camper is off the truck again.

While you're in there, why not fill the hidden section of threads with JB weld so there is no gap for the roll pin to span? I know it's a patch but ought to take the bending moment out.

It is quite a coincidence, isn't it. I made my report at www.nhtsa.gov. Had to use "unknown" from the drop down, since Happijac is one of the choices. Then explained in the text field the make and model. Maybe two similar reports might get their attention?

Thanks, Jim, for posting my pics. The tech at HJ said it was due to over retracting. We really haven't been doing that, and are making sure we don't do it in future. When we get back home from our eight week hiatus!, We will be inspecting all pins again and replace if necessary. I'll make sure my husband reads all of your comments, so thanks everyone for your help. Stevenal, I can't believe it happened to you also! I believe it's a poor design and frankly, shoddy construction. The one thing that gives me piece of mind is that the tech said the jacks won't fail when the camper is off truck and on the jacks.

stevenal wrote:

bigfootford wrote:

I agree...



I have always worried about something going wrong with the jack controllers... ATwood, Happijac etc. and one jack or more begins to descend or try to go up.... Hammering at the pin...
So I installed a 50 amp switch by the back door so I can shut off the 12vdc to the controller when not in use.

I have heard of a remote wireless controller being activated without the remote. Both jacks on the passenger side went down. The camper was tilted bad. No damage to the Bigfoot camper was found...

Jim

Good point. In my case, the remote is wired and the connection point is inside a locked compartment.

Lucky for me, I chased the 10ga DC+ wire to the fuse that protects the controller. It is located at the rear of the camper under the sink.... So I ran wires from there to the switch and spliced into the + lead going to the controller.
The Bfoot has a separate fuse panel for several items located under the sink. The other fuses are in the converter distribution panel.

Any of you can add a switch. Your fuse for the controller should be located somewhere. You can splice in there and run the wires. Or you can remove the DC+ wire on the controller and run wires for the switch from there, to the switch and back. 8 ga wire would be best.
Figure that the jacks will pull about 35 amps when lifting the camper.

Jim

bigfootford wrote:

I agree...

OP, were the jack or jacks binding/ struggling/clicking when trying to raise the camper prior to failure?

I have always worried about something going wrong with the jack controllers... ATwood, Happijac etc. and one jack or more begins to descend or try to go up.... Hammering at the pin...
So I installed a 50 amp switch by the back door so I can shut off the 12vdc to the controller when not in use.

I have heard of a remote wireless controller being activated without the remote. Both jacks on the passenger side went down. The camper was tilted bad. No damage to the Bigfoot camper was found...

Jim

Good point. In my case, the remote is wired and the connection point is inside a locked compartment.

KKELLER14K wrote:
It looks to me like the pin was compressed from over tightening....WOW!! First time I have seen this....the pics are awesome...it really tells a story.

That's pretty much what Happijac told me when I reported my failure. Over-retraction could cause this, and they say I should stop retracting two inches short. But the motor has a clutch to prevent over-retraction, I avoid working the clutch, the instructions call for retracting completely once loaded, and the thing rattles terribly at two inches. I remain convinced this is a poor design, and intend to make a report to the NHTSA.

KKELLER14K wrote:
It looks to me like the pin was compressed from over tightening....WOW!! First time I have seen this....the pics are awesome...it really tells a story.

I agree...

OP, were the jack or jacks binding/ struggling/clicking when trying to raise the camper prior to failure?

I have always worried about something going wrong with the jack controllers... ATwood, Happijac etc. and one jack or more begins to descend or try to go up.... Hammering at the pin...
So I installed a 50 amp switch by the back door so I can shut off the 12vdc to the controller when not in use.

I have heard of a remote wireless controller being activated without the remote. Both jacks on the passenger side went down. The camper was tilted bad. No damage to the Bigfoot camper was found...

Jim

It looks to me like the pin was compressed from over tightening....WOW!! First time I have seen this....the pics are awesome...it really tells a story.

Here's the pictures from the OP'er...

Roll pin is destroyed!





Jim

stevenal wrote:

Upon further thought on the subject, I believe there is a design flaw here. It's not clear in the picture, but the threads don't stop at the collar, they extend to the hidden top of the rod. The inside of the collar is cylindrical, un-threaded. The joining pin then crosses a gap from collar to shaft so that the force on the pin is a bending moment. In my experience, roll pins are used where they are subject only to shear forces such as the pin located a bit higher in the photo. I'll be inspecting my other 4500 once the camper is off the truck again.