Happijac new vs old?
I have electric Happijacs, possibly 4600 (numbers are illegible) that are complaining. I could: 1) remove, clean and relube 2) replace the legs with 4220 or 4820 legs 3) replace the whole set...
Forum Discussion
OK, to finish this out:
I bought four new 4820 jacks. The new jacks work fine as a replacement for the 4500 and 4150 jacks. Motors fit on top, all the holes in the same place, etc. The new ones are about 3 inches longer than the old. They have zinc plated lower tubes and a dust scraper on the leg.
The literature and some magazine reports say they are much stronger, however the tube size and wall thickness are the same as the old, and they weigh the same (26 lbs). Therefore they cannot be much stronger or stiffer than the old ones if at all. The upper tube being a few inches longer will add a little but not much.
Mounting one on one side of the front, I tested the new alongside the old one still on the other side. There was no significant difference in current drawn by the motors, when both of them are activated they run about the same speed with the same sound. This strongly implies that the torque required is similar. Given that the old ones were ball screw and the new ones Acme screw, the old ones should be easier operating. But another difference is the new ones have a roller thrust washer while the old ones have a plain greased washer. The two primary sources of friction are the nut and the thrust washer contributing about equally. The old one with low friction ball screw but high friction thrust washer seem to behave about the same as the new one with high friction Acme screw and low friction roller thrust washer. That makes the new ones better in my opinion since the Acme screw is more robust and less affected by dirt. In addition, though I did not disassemble them to confirm, the new ones reportedly allow easy removal of the Acme nut for cleaning, greasing, or replacement while the old ball nuts are pretty much not serviceable.
So to summarize the new ones aren't stronger, don't operate much easier, but are probably longer lived and certainly more serviceable. They can be used as a replacement for the old without changing the motors or controller.
I bought four new 4820 jacks. The new jacks work fine as a replacement for the 4500 and 4150 jacks. Motors fit on top, all the holes in the same place, etc. The new ones are about 3 inches longer than the old. They have zinc plated lower tubes and a dust scraper on the leg.
The literature and some magazine reports say they are much stronger, however the tube size and wall thickness are the same as the old, and they weigh the same (26 lbs). Therefore they cannot be much stronger or stiffer than the old ones if at all. The upper tube being a few inches longer will add a little but not much.
Mounting one on one side of the front, I tested the new alongside the old one still on the other side. There was no significant difference in current drawn by the motors, when both of them are activated they run about the same speed with the same sound. This strongly implies that the torque required is similar. Given that the old ones were ball screw and the new ones Acme screw, the old ones should be easier operating. But another difference is the new ones have a roller thrust washer while the old ones have a plain greased washer. The two primary sources of friction are the nut and the thrust washer contributing about equally. The old one with low friction ball screw but high friction thrust washer seem to behave about the same as the new one with high friction Acme screw and low friction roller thrust washer. That makes the new ones better in my opinion since the Acme screw is more robust and less affected by dirt. In addition, though I did not disassemble them to confirm, the new ones reportedly allow easy removal of the Acme nut for cleaning, greasing, or replacement while the old ball nuts are pretty much not serviceable.
So to summarize the new ones aren't stronger, don't operate much easier, but are probably longer lived and certainly more serviceable. They can be used as a replacement for the old without changing the motors or controller.
