Jacking up a gear

[n3437d]

There is probably a simple answer to this question- Having purchased a pair of "gear pads" to assist in jacking up a gear to change tire, brakes or what-ever, what is the correct method of using these pads. My first attempt almost resulted in a broken brake disc. As I was jacking up the gear with the tailwheel and other main choked to prevent roll, when the gear became "unweighteted" it kicked inward rather violently knocking the jack out.

What is the trick.

[N1478D]

Jack the leg up slowly and watch the tire. As the tire moves inward some, lower the jack and reposition to a vertical position, it probably started leaning as the tire moved inwards. You might have to reposition more than once.

[doug8082a]

I use a regular auto floor jack (the kind on 4 wheels with the long jack handle). The large round plate that would normally make contact with a car's chassis has been replaced with a plate that has a steel rod about 1" dia. and 3 or 4 inches long welded in the center. The steel rod sticks straight up and has a divot in top end in the center to receive the jack point on the jack pad. When you jack up the gear (slowly), the jack will roll slightly and allow you to keep it centered under the jack pad.

[GAHorn]

I'm not sure how your gearleg became so stressed so as to "kick", but normally you'd certainly want to make sure no tie-down ropes are attached anywhere on the airplane, as they can impart unusual loads when the airplane is jacked. Ordinarily jacking a gearleg puts no more strain on it than is already there. (Was your parking brake set? In fact, is your parking brake still operational? )

[N3243A]

I use a Hi-lift handyman jack on my gear leg jack pad. To compensate for the spring of the gear as you jack it up, I lean the whole Hi-lift jack about 10-15 degrees out from the plane. With the wheel fully off the ground, the jack returns to vertical due to the gear springing in. Jack it up slowly so that gear don't spring suddenly when your tire comes off the pavement.

Bruce

[GAHorn]

Ok. I get it now. I'd not experienced this problem before. You're jacking at a point well inboard of the wheel, which relieves the spring gear of it's load.
There were two Cessna jack pads. One (larger/wider one) fits very high up on the leg, and the smaller of the two fits farther down toward the wheel. The farther down the gear leg you place the pad the less relief occurs with the spring. Using the smaller pad, I took two 1/2" X 4" pieces of plywood and place it on the fwd or aft edge of the spring gear and within the channel of the pad. This lets me use the pad very low on the leg, and use a shorter jack. It also prevents the wheel from trying to move very much inboard as it lifts. (With a peice of cardboard taped inside the pad channel, it also prevents scratching the paint on the gearleg.)
Sometimes I just suffer from dumb luck.

[Harold Holiman]

George,

I got plenty of experience jacking mine recently while aligning my wheels. I must have jacked it at least 15 times trying various shims, replacing the wheels and rolling it on greased plates, measuring it, then jacking it again. About the third time I jacked one side using a Cessna type jack pad, I had just removed the axle. I heard some kind of groaning or creaking then all of a sudden, kablam, it fell off the jack and to the floor. After that each time I jacked each side, as soon as I slipped the wheel off, I stacked blocks under the end of the gear leg in case it decided to fall again. I dont know really why it decided to shift and fall that one time as it never even tried to shift or fall all the rest of the times I jacked it. However if it had, it couldn have fallen but about an inch till it would have been sitting on the blocks. I was curious as to if it was going to have any different ground handling chateristics since I aligned the wheels, but I really can't tell any difference, and I have landed on both grass and pavement since aligning it. It does look better though.

Harold
N92CP
Mbr #893

[N170BP]

Had my airplane fall of the jack using one of those gear
jack pad thingies. For that reason, I prefer the old method
(two pieces of lumber sandwiching the gear leg with big
C clamps). A friend also came up with a novel idea of cutting
a 4"x4" piece of lumber just the right length (with relief notches
cut on the upper end corners) so you can lift both main gear legs
using a floor jack with the lumber spanned across the gear track/width (the lumber edges pick up on the undersides of the gear leg ears). Harder to explain in writing than it really is.....

Bela P. Havasreti
'54 C-170B N170BP

[zero.one.victor]

I made a set of jack pads a few years ago for my 170. They don't fit down real close to the "ankle" of the gear leg. The first time I used them I was taken by surprise by the lunge toward the center of the airplane as the tire came off the ground. Now I know it's gonna happen so I compensate, as per above posts.
Pads that fit down right above the ankle of the gear leg would be the ticket. I've also seen ears that bolt to the axle bolts & turn in,used for tow bars,on both BirdDogs & 190/195's. Also on Density Dog's 180. They look like they would work well as jack points,with no lungeing.
Or a floor jack under the end of the gear leg maybe.

Eric

Eric, I don't think the tow-bar adaptors are designed to support the weight of the airplane. I hope everyone is jacking their airplanes INDOORS and not out on the ramp where wind can move the airplane around considerably while up on jacks. Also, the gear will certainly be in a different strain AFTER occupants/cargo are unloaded from taxiing into the tie-down spot. (Another reason to push/tow the airplane into a protected hangar before jacking,....so that the gear is not spread-out from loaded weight before jacking.) Another consideration is certainly the toe-in/toe-out which might pre-load the gear and have the legs ready to be "sprung" when the wt. comes off them.
To be honest, I hadn't exerienced this problem except very mildly in 35 years of fooling around with airplanes. It really makes me wonder about the various alignment problems and jacking techniques that folks might be experiencing.

[Dave Clark]

Eric

Those 195 tow lugs are not meant for jacking points, will probably bend if you try it on a 195 and I wouldn't advise jacking a 170 with them either.

[n1410d]

http://home.earthlink.net/~n6d4/170b.htm

[zero.one.victor]

Nice idea,IF you have a set of high-wing airplane jackstands laying around. Them bad boys are pretty spendy,I bet!
Whose website is that? I see that they reference "170B" but the airplane in the picture looks like a 172/175 taildragger.

Eric

[wa4jr]

I've also been jacking my plane up using the wing points, but with a long fixture made from 2x4 lumber and a standard automotive floor jack. The wooden fixture has a near horizontal piece covered in carpet that bears against the underside of the wind just outboard of the lift struts. No worry about the gear springing around and kicking the jack out, and the legs are free to for a good shake inspection. Yes, those wing jacks are expensive if you get the "made for airplane" version. If you go down to the salvage metal yard and get nice straight box tube sections, you can whip up a wing jack stand in an afternoon with a MIG welder and a good chop saw. Fit a standard long stroke bottle jack to the top and you have a jack system comparable to the $1000 jobs at a cost of under $100