Front landing gear/stabilier jacks ???

Billy · June 23, 2020

For those with front, hydraulic landing gear mounted at angles away from vertical, have you had hydraulic leaks yet from bad seals? How long after delivery did they start leaking?

I was with a salesman recently who Googled these leaking jacks and told me his indications seemed to indicate that on average, one or both front jacks start leaking around two-year intervals.

What seems to me to be the sad part is, the seals failing prematurely should be reasonably predictable if you think about it.

As the trailer rises or falls, the fixed angle away from vertical would require the feet of the jack to move further outboard as the trailer rises and further inboard as it lowers. But how can the feet move with perhaps 4,000 pounds or more on each jack? Do the feet move? Does this eventually bend the rod?

I’m not a Hydraulics System Design Engineer, so can someone educate me on how the feet can move? The hydraulic cylinder remains mounted securely to the frame at, let’s say, six degrees. If the feet do not move, how then can the rod not apply an unequal side load against one point on the seal? It could perhaps be enough to not only ruin the seal prematurely, but it may even be enough to bend the rod.

A bent rod may even be the cause of the jack not retracting normally. Just enough bend to act sort of like it’s just “sticking” may not be detectable to the human eyes.

If the rod is bent, would it not be pretty much a waste of money not to replace the rod with a straight one when the seals are replaced? It seems likely to me that the cylinder would need a good inspection and it may even need to be honed, if they do that. Heck, why not just buy a new jack?

Has anyone had leaking hydraulic jacks a second time after replacing seals in the same jack once before?

I have asked factory Reps about this. All I have ever been told is they are mounted at a slight outboard angle to be slightly more stable in windy conditions. Well, okay. I suppose the math may show that on paper. I honestly don’t know. However, with only the front two jacks being angled outboard, is it really going to make a significant difference in the real world? The other two on each side, middle and rear, are mounted in the vertical. I’m thinking few people leave their trailer very long without deploying all stabilizer jacks.

I’m just thinking of taking what should be an extremely reliable system and shortening the life expectancy of critical parts for no off-setting real gain. I’ve read many forums and failure of hydraulic seals is already more common than it should be, IMHO, and it seems the front two jacks are more likely to be the first ones to leak. After all, this is not new technology.

Are we being sold a bill of goods on this set-up?

Kirk W · June 23, 2020

Would you mind sharing what RV manufacturer is going to this configuration? What the salesman told you sounds like typical sales BS to me.

Edited June 23, 2020 by Kirk W

rickeieio · June 23, 2020

To take this a bit further, even if the legs are mounted at "0" degrees relative to the frame, if the ground isn't perfectly level, the same forces would be generated while getting the camper to "level".

Using some sort of blocks to take up most of the distance from the ground to the jack lessens this bending force, but doesn't eliminate it.

Billy · June 24, 2020

Off the top of my head Kirk, the Grand Design Momentum "M" class toy haulers (specifically the 395M) now come with the front pair of jacks mounted at a 6 degree outboard angle. If I remember correctly, the same is true on the Voltage 4115 with hydraulic jacks. There are others. I just forget exactly which ones and I don't want to get them wrong so I won't mention them by names.

Sure, with these jacks, you'll never get away from having some side loading in many situations. However, doesn't mounting them at an angle ensure you will always have the wear and bending force on them trying to move the rod out of alignment with the center axis of the cylinder while the rod is under load and is in motion? Certainly there will always be wind loading. But you aren't moving the trailer up and down all the time in the wind.

It just seems starting out with this error built in is ensuring you'll be behind the proverbial "8-ball" every time you drop the trailer. Certainly, using blocks to reduce the necessary stroke would help minimize the out-of-alignment damage. Very good point Rick.

But I really don't know since this is not my field of expertise. That's why I ask the questions.

Billy

Edited June 24, 2020 by Billy

Kirk W · June 24, 2020

31 minutes ago, Billy said:

Off the top of my head Kirk, the Grand Design Momentum "M" class toy haulers (specifically the 395M) now come with the front pair of jacks mounted at a 6 degree outboard angle. If I remember correctly, the same is true on the Voltage 4115 with hydraulic jacks. There are others. I just forget exactly which ones and I don't want to get them wrong so I won't mention them by names.

I believe that Grand Design is using Lippert Components (LCI) frames and jacks, which probably means that Lippert is the one doing the design. There are a lot of RV builders who use their products as I am pretty sure that they are the largest supplier of RV frames. While I am not an engineer, one would think that Lippert employees some of them and that such loading was considered?

Dutch_12078 · June 24, 2020

Designing hydraulic cylinders for side loading is pretty standard in the industry. One of the most common methods of increasing side load support is the use of "stop tubes" that prevent the piston from bottoming out in the cylinder when fully extended.

Second Chance · June 24, 2020

3 hours ago, Kirk W said:

I believe that Grand Design is using Lippert Components (LCI) frames and jacks, which probably means that Lippert is the one doing the design. There are a lot of RV builders who use their products as I am pretty sure that they are the largest supplier of RV frames. While I am not an engineer, one would think that Lippert employees some of them and that such loading was considered?

Kirk is correct - Grand Design utilizes Lippert chassis and hydraulic systems. As with most manufacturers, though, GD specs the frames and Lippert builds them to spec. All of GD's Solitude line with hydraulic landing gear and stabilizers come with the front landing gear angled slightly outward. I put an 18" piece of pressure treated 2 x 12 sideways under the front pads so they can slip a little if needed... they never have that I've been able to discern. I've also not read of any front landing gear failures or leakage on the Solitudes on the two GD forums, either. I have, however, read of a couple of leaky cylinders on the back four that came from the factory that way.

Rob

Danandfreda · June 25, 2020

This is the same thing I thought about the hydraulic jacks our 2011 mobile suites,they are all angled I try to use blocks to keep them as short as possible. I don’t think it’s the rods bending as much as putting a lot more pressure on one side of the seal.