HappiJac 4150 Problem

Whatever is attached to the plate crimped inside the black tube is shot because the long threaded shaft threads are OK throughout the length and the jack can't hold in any position. It failed without warning, I can't be the only one ?

AnEv942 wrote:


Curious material the block is made of.
I assume this 'cube' swagged in top of inner (black) tube as in Kkellers14k pic. Hopefully Happijac works with you on this

There is a plastic guide (or dirt scraper or something) right at the top of the tube. The crimps are about two inches down, you can see them dented into the tube on all sides. Those are what's holding your camper up. Inside of mine (again many years ago) there was a brass or bronze ACME nut fastened to a square steel plate captured by the crimps.

BTW those Trojan saw horses are the Bee's Knees! I've put a whole unit of plywood on a set (maybe a bit over a ton?), they didn't even flinch.

RamTC wrote:
I suspect the threads are deteriorated due to moisture. This means that all my Happijacs are subject to failure at any time.

Moisture isn't a problem here in the Pacific NW/Seattle area. It never rains here.
I keep saying over and over... there's a reason I call them Crappijacks. I can't wait to run across a sale on a set of Rieco's.

Too bad Torklift doesn't make camper jacks..... I mean, heck, even their name would be fitting of a nice set of jacks--think about it--"Torklift Camper Jacks". Has a nice ring to it.....

RamTC wrote:
....

Update: It took all of 10 mins for me to disassemble the jack. The failure is as I suspected, the crimped in worm gear threaded assy block that is part of the lower tube has failed in a way that allows the long threaded shaft to slide through under load. I suspect the threads are deteriorated due to moisture. This means that all my Happijacs are subject to failure at any time. They were new in 2005 and oiled as suggested by HJ. I'll contact HJ to see if I can just send them in the lower tube and I'll pay for the repair.

Curious material the block is made of.
I assume this 'cube' swagged in top of inner (black) tube as in Kkellers14k pic. Hopefully Happijac works with you on this

A ball screw is a shaft with a thread profile that looks semi-circular, and the nut that runs on it has recirculating balls that fit in the groove on the shaft and mating groove in the nut. They are much lower friction than a standard threaded nut, and are used for high loads. An ACME is simply a threaded nut, though the ACME load bearing thread profile is used rather than UN or some other bolt or screw profile. ACME should be pretty much failure proof. It could be a stripped nut or shaft, that seems unlikely. If it held the load, but wouldn't turn, then you would suspect the drive with does have a pin through the gear and shaft. The ACME screw anchorage at the top of the jack could not have failed or you would see the screw itself poking out of the top of the jack. However the nut is fastened up inside the top of the lower tube, that could have come adrift and is simply walking down the inside without pushing the tube down (and the camper up). The nut is on a plate that is just crimped in place (or it was on mine of 16 years ago).

Happijak used to offer a repair service that was a pretty reasonably flat rate, don't know if that is still on - you would have to phone them and ask.

THe 4150 is ACME according to the HJ site, but what's the difference vs. Ball Screw ? Either way, my 4150 failed under load and the long threaded shaft looks clean, so the problem is in the female threaded section and where was the backup they advertise?

I thought the 4150 is a ball screw, not an ACME. A ball screw will retract (backwind) under load unless the brake stops it. If the brake mechanism is broken, then it will retract. An ACME screw won't, too much friction to back drive. The brake mechanism is underneath the bevel gear, you can't see it until everything's apart. The brake is released by the crank (or motor) turning backwards - maybe something is stuck and not letting it reset.

I reviewed those pics before posting, but thanks. It sure seems like the worm gear top assy has failed as I see nothing else that would allow the jack to retract itself back under load (without any shaft rotation). I'll take apart and see, but IMO this is a big time design failure.

Update: It took all of 10 mins for me to disassemble the jack. The failure is as I suspected, the crimped in worm gear threaded assy block that is part of the lower tube has failed in a way that allows the long threaded shaft to slide through under load. I suspect the threads are deteriorated due to moisture. This means that all my Happijacs are subject to failure at any time. They were new in 2005 and oiled as suggested by HJ. I'll contact HJ to see if I can just send them in the lower tube and I'll pay for the repair.

Yes, about the only thing it could be is the pin.

Happijack disassembly

I took all of mine apart, re-greased them and put them back together.

But, I don't think I have ever heard of the pin breaking before.

There are a couple posts about disassembly, Take it apart and see what is broke. Could be the pin that makes the gears go around. Easy fix if thats the problem.