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-   -   Single person RV-12 jack system (http://www.vansairforce.com/community/showthread.php?t=171501)

JimMac 05-13-2019 10:31 PM

Single person RV-12 jack system
 
Here is my solution to jacking up my RV-12 when I have no help. I made two identical stands like this. (See photo below). The pad on top was not yet permanently tacked down when this photo was taken. The horizontal 4x4 is 25 inches from the ground and 26 inches wide. Here is the procedure: Place one stand under the belly between the steps. Jack up the stand with the small hydraulic jack until the base of the stand is high enough to slide the two loose 4x4’s under the stand bases. Release the jack pressure.
Since the main landing gear is still on the ground, the plane is stable roll-wise, so there will be no tendency for the plane to roll off to the side of the single jacking point as the stand is being raised off the ground. The top of the hydraulic jack fits into a 1 inch hole in the center of the vertical 4x4 to keep the jack from slipping out of place.
Now place the second stand into its proper jacking position under the bulkhead near the wing trailing edge. Jack it up until it is high enough to place the two loose 4x4’s under the base feet of the stand. Release the haudraulic jack pressure. The wheels will clear the ground by about 2 inches.
The front jack stand is supporting the plane stable enough in roll that there it will not roll to the side off of the single jacking point.
This seems to work well for me. I welcome any critiques on the design.

I could have used a 2x4 instead of the 4x4 on top of the stand to make it a little lighter.



JBPILOT 05-14-2019 07:32 AM

Curious - - - - -
 
Was your main purpose to be able to change tires etc. ?

John-G 05-14-2019 07:42 AM

Jim-

Nice job! I like the stand design a lot!

Only thing I would consider adding is a couple of pins that would prevent the stand from sliding off the 4x4 bases should there be a side load from some unexpected source.

tomkk 05-14-2019 08:48 AM

Looks like it would work great. I've just never had occasion to jack up both sides at the same time.

DHeal 05-14-2019 09:35 AM

Should work great but I have taken a more minimalistic approach. One HF hydraulic wing jack stand at the appropriate tiedown point to change each main gear tire, check landing gear bolts' torque, etc. When I need to work on the nose wheel I use a floor-mounted hard point or weight to pull down on the tail tiedown point to temporarily lift the nosewheel off the ground. Works for me. I have a pair of heavy-duty fuselage stands but have never found the need to use them.

DaleB 05-14-2019 02:36 PM

Sure, but that does not satisfy the desire (need?) to have all three wheels off the ground and wings off for the condition inspection. I suppose it's not an actual requirement, but it sure does make things easier and quicker to be able to get at everything at the same time.

JimMac 05-14-2019 05:52 PM

OK, everyone has made some good points. I’ll try to explain what led me to this solution. I needed to do a complete brake and wheel bearing job so I wanted both wheels off the ground while I did all this work, including replacing brake fluid and testing the whole system for leaks and proper brake pad movement.
1. Cost was a consideration with me. These stands were inexpensive to make. Rather than use 4x4’s I could have made the whole stand out of 2x4’s and doubled them wherever I thought they needed to be beefier - like the vertical legs. That would have lessened the cost a bit. Also, the Harbor Freight jacks are inexpensive. And you might could get by with only one.
2. I had tried the “Weights pulling down the tail” method using concrete blocks on a mechanics crawler, but I found it difficult to manage it alone. It’s easier to just slide the stand between the foot steps and jack it up.
3. Earlier I had tried to make a cheap hydraulic lift for lifting under the wing tie downs.
(A) I never came up with a good design that precluded the tie down ring from slipping off the jack.
(B) I just didn’t like the idea of that much weight pushing down on the aluminum threads that the rings were screwed into. Maybe I’m just being silly about that.
4. When both stands are in place holding the plane off the ground, there is a lot of downward force on those loose 4x4’s under the feet of the stand. It’s difficult to even kick them out from under the stands. However, a couple of 1/2 inch dowels in each one that protrudes about 1/4 or 1/2 inch and that mate with holes on the underside of the stand bases would make it more secure. I have no concern about the wind blowing the plane sideways since I’m in a hangar.

I appreciate everyone’s comments. I just wanted to throw this out there as “Yet Another Jack Idea” to be critiqued. I have found this design to be convenient and easy for one person to manage.


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