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Jacking - Tail Ballast

DanH

DanH

Legacy Member
Mentor
Annual time soon. About 650 hours now, so this year I want to take a hard look at the gear clamp blocks and supporting structure. Caught a Harbor Freight sale this summer, and made up a new set of wing jacks. They insert into welded steel cups bolted to the tiedown point; can't slip.

Need to ready a tail ballast weight. I figure at least twice the weight necessary to balance with longerons level, but probably not the typical big drum of concrete on wheels. Anybody have a figure?

Unassembled.jpg


Jackstands%20800w.gif


Jacking%20RV-8%20800w.jpg
 
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This setup will pick up the nose on my 10-----many times more force needed than balancing you plane.
 
Nice setup Mike!

Maybe 2? It seems so "Cheap$$$" that adding a second one for safety would be cheap, easy and safer.
 
Guess

I had to use 200lbs on my C45 (6000lbs EW) and I would GUESS you would need about 20% of that amount. In my case, the weight went on top of the H stab.

Carry on!
Mark
 
About 40 pounds to do the same thing, jacked from the same points, on my RV-7. Technically a bit less, but the balance margin gets a little thin.
 
Dan, did you thread the top "ring" (3" pipe?) that the bolts go through?

~Marc

DanH said:
Annual time soon. About 650 hours now, so this year I want to take a hard look at the gear clamp blocks and supporting structure. Caught a Harbor Freight sale this summer, and made up a new set of wing jacks. They insert into welded steel cups bolted to the tiedown point; can't slip.

Need to ready a tail ballast weight. I figure at least twice the weight necessary to balance with longerons level, but probably not the typical big drum of concrete on wheels. Anybody have a figure?

Click to expand...
 
Lars said:
About 40 pounds to do the same thing, jacked from the same points, on my RV-7. Technically a bit less, but the balance margin gets a little thin.
Click to expand...

Ralph Inkster said:
I put 3 cases of oil (75lbs) on the Horizontal if jacking a RV8 or Rocket while level (tail wheel on a stand)
Click to expand...

Excellent info, thanks guys. I use an accessorized tripod engine stand as an adjustable tail prop. Planning to strap the wheel to the cup, add a plywood platform in the base, and load the platform as necessary.

Stand.jpg


Plummit said:
Dan, did you thread the top "ring" (3" pipe?) that the bolts go through?
Click to expand...

You got it. Screw the bolt into the collar until the tip touches the jack, then tighten the nut to clamp the leg to the collar.
 
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I use a cement septic tank lid on my 6A..... but a Red Head in the floor might be more elegant.

I would use machine bolt in the Red Head. And take another bolt and cut off about a 1/2 inch of thread, cut a screwdriver slot in it and screw it into the Red Head till it's flush with the cement.

As far as a second one for safety........ A properly sized and installed (not hard to do) Red Head will lift the entire aircraft.

A jack stand (wooden brace) under the firewall if lifting a TD would give me piece of mind. I would do the same with my 6A if I were removing the nose gear from the mount.
 
Ralph Inkster said:
Do you have a way to lock the castors under the tail (engine) stand? I like to stabilize all three ground lift points.
Click to expand...

No locks on the casters, but the idea of placing a Red Head in the floor is attractive. Put the tailwheel in the stand, tie the tailwheel spring to a ring in the floor, and that baby ain't goin' nowhere ;)
 
DanH said:
No locks on the casters, but the idea of placing a Red Head in the floor is attractive. Put the tailwheel in the stand, tie the tailwheel spring to a ring in the floor, and that baby ain't goin' nowhere ;)
Click to expand...

Dan,
I happen to know someone who just happens to have some!!;) And they work great. I'm sure he'd share.
 
SmilingJack said:
Nice setup Mike!

Maybe 2? It seems so "Cheap$$$" that adding a second one for safety would be cheap, easy and safer.
Click to expand...

Mike, you really should get a better anchor in the floor than that if you're taking your nose wheel assy off. Quite a lot at risk, and that type of anchor isn't the best in concrete, and of course the quality of the concrete will have a lot to do with the strength as well.

Please use at least two of them and/or use a better anchor. Short wedge anchors are better but then you have the stud sticking out of the floor when you're not using it. :eek:
 
I needed to lift the nose of my Cherokee to replace the strut seals. A wooden pallet, a strap and some buckets of water did the trick. Certainly not as elegant as some other methods but got the job done.
 
DanH said:
the idea of placing a Red Head in the floor is attractive. Put the tailwheel in the stand, tie the tailwheel spring to a ring in the floor, and that baby ain't goin' nowhere ;)
Click to expand...

Exactly; I just screw one of the Van's Forged Tiedown Rings into the Red Head. Nothing sticks up out of the floor when I'm not using it.

Cheers, David
RV-6A A&P
 
Quick follow-up...had a note from one of my engineer friends, who quite correctly pointed out a possible failure mode to the simple jack frames you see in the first post.

If enough force is applied perpendicular to the top, it could potentially bend the base arms while sliding the collar up the jack casing. It is very much like folding an umbrella. There many ways to eliminate the possibility, examples being....

1. Turn the collar into a strong clamp.
2. Add a clamped collar above the existing collar.
3. Tighten the collar bolts so they bite into the jack casing.
4. Add a tension member between the base and the collar

Although the calculated side force to collapse the jack appears to be significant, I'll probably add a tension member to be sure, perhaps just a length of aircraft cable with some nicopress eyes. A strap, rod, or a length of all-thread would also work.
 
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DanH said:
Quick follow-up...had a note from one of my engineer friends, who quite correctly pointed out a possible failure mode to the simple jack frames you see in the first post.

If enough force is applied perpendicular to the top, it could potentially bend the base arms while sliding the collar up the jack casing. It is very much like folding an umbrella. There many ways to eliminate the possibility, examples being....

1. Turn the collar into a strong clamp.
2. Add a clamped collar above the existing collar.
3. Tighten the collar bolts so they bite into the jack casing.
4. Add a tension member between the base and the collar

Although the calculated side force to collapse the jack appears to be significant, I'll probably add a tension member to be sure, perhaps just a length of aircraft cable with some nicopress eyes. A strap, rod, or a length of all-thread would also work.
Click to expand...

I was concerned about that myself. I got a couple of HF u-joint sockets, 1/2" square drive by what ever size slipped over the top of the jack rod. Squared off a couple of socket head cap screws so they fit in the square drive end of the sockets. Run the screws into the tie-down points with a couple of washers under the screw head so the sockets don't bear on the aluminum skin. Sockets on top of jack rods. Raise jacks. Engage SHC screws. Now I have a jack point that can't support a moment. From the "picture is worth a thousand words" department, I'm going to my hangar shortly, I'll photo document if anyone is interested.

Edit: see photo below. The jack is pretty much the same as yours, Dan. Swivel socket is 1" 12 point, happens to fit the top of the jack rod perfectly. Crudely squared-off 3/8" SHCS also visible. Socket has enough range of motion that it's not bound up if I jack up one wing with tailwheel on the ground (thus no bending moment). If one was concerned about the square drive end of the socket slipping off the bolt it would be easy enough to fab something deeper.

Note also the black shaft collar around the jack rod, in this case 25mm, the actual diameter of the rod. I tighten those if the plane is going to on the jacks for more than a few minutes, in case the jack decides to leak.

i-3HFTDfC-XL.jpg
 
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I'm using channel steel for my jack base. If it fails in that mode, I'll have other, bigger issues to deal with. Very nice Lars, I especially like the locking collar around the jack shaft.

~Marc
 
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Added a tension strap, so the collar can't slide up the jack case.

Jackstand%20Tension%20Strap%20800w.jpg


Seems to work fine. I didn't shove the airplane around real hard (no matter what you've heard, I'm not insane), but it felt quite stable, and I was climbing in and out all day.
 
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Perfect - and light weight too.

DanH said:
Added a tension strap, so the collar can't slide up the jack case.

Seems to work fine. I didn't shove the airplane around real hard (no matter what you've heard, I'm not insane), but it felt quite stable, and I was climbing in and out all day. Red socket is steel; bolts to the tiedown point with a 3/8-16 x 1-1/2 long.
]
Click to expand...

Perfect !!
 
Granted, I have an A model, but here's what I did:

FP25032012A00055.jpg


It's basically just some concrete blocks on a four wheel dolly. I did add a piece of 3/4" plywood to be able to put an eyebolt in the center. The nice thing is that I can roll it anywhere in the hanger. Although I will have to admit, I'm lazy and it usually just stays under the tail all the time.
 
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