Happijac slow leg

Mine are the same way. Apparently the motors do not produce enough torque to remain constant speed devices. Varying drags of the gears, leg friction, and jack loads cause the motors to run at different speeds. I just keep an eye on the front two jacks to see that they are about at equal extension and adjust as necessary. Then I adjust the rear jacks before continuing the raising or lowering process. I accept it as part of the jacking procedure.

LeRoy

Situation normal. Motor speed is a function of applied voltage and mechanical load. Voltage will be the same at all motors, since the relays are simply on/off. Load will be different depending on weight and friction. Until manufacturers incorporate voltage control and position feedback, manual compensation will be needed.

They are also affected by the length of the wire feeding them which actual changes the voltage slightly.

I’ve considered trying some “tuning” by adding an extra power wire to get better current to the slowest one, and adding lengths of wire to the fastest ones to weaken them a little.

burningman wrote:
I’ve considered trying some “tuning” by adding an extra power wire to get better current to the slowest one, and adding lengths of wire to the fastest ones to weaken them a little.

My fast one is the farthest from the motherboard.

I will just live with it.

A quick solution that comes to mind is to put potentiometers (speed controllers) on all of them and cut voltage down of the 3 fastest one until all run at the same speed. Im not sure if lower voltage will harm the motor

Grease it.....

The potentiometers might work to tune it in, but you’ll need pots that can handle a bunch of current.
The fastest one being furthest from the board isn’t too significant because that’s only a few extra feet, I was thinking of running my fastest one through a coiled-up loop of wire long enough to have a noticeable effect.

If anyone is bored enough to try it, it would be interesting to swap places with faster and slower jacks and see if it’s the wiring or the jack.

Everyone who responded scores 10/10. I had a similar problem and jumped to buy a new motor. That was a mistake. The best operational fix is to be patient, run the front at little-run the back a little and tweak when necessary. Unfortunately the jack causing me the most grief had nothing to do with the motor; the bearings are NFG. The bearings on this jack are seized (4150 model) others are in poor shape. I learned a lot from this forum and can confirm that these jacks need to be dismantled every 2-3 years for cleaning and regreasing. I dismantled my set and am looking for bearings from a local shop because Happijac isn't so happy when it comes to details about the components. New jacks are $2070 online and $3000 from retailer. The bearings must be less expensive.

clean all wire connections ,especially the quick connects

My Atwoods have always worked that way. Always a rear one, but not always the same side. A liittle annoying, but doesn’t seem to hurt anything for almost 13 years.