Posted by JamesB on Saturday, January 22, 2011 @ 12:00 PM:
At least yearly, we have to raise my RF5B for a retraction test; sometimes more often for other servicing. Per the factory manual, I made a "trestle." We lift the tail of the glider, slide the trestle under the skids, then lower the tail.
Yet, as we age, lifting the tail of the glider over our shoulders has become much less entertaining to my A&P and myself. So, in recent years, I've been looking for a solution that involves a lift.
Recently, Harbor Freight Tools put a motorcycle/ATV lift on sale. Model 2792 has a 1500-pound capacity. Although it uses hydraulics for lifting, once the vehicle is lifted, you push metal cogs in place and release the pressure on the hydraulic cylinder so the cogs hold the weight. At about $80 USD for a new lift, I felt this lift was worth a chance. Note that the long handle is just used for moving the lift. Pumping the hydraulic bottle is done with a food pedal.
Using scrap wood, I made an adapter to go between the two pads on the lift and the skids on the glider. The pieces are glued & screwed for strength.
I'm now able to lift the glider by myself, pushing on the hydraulic cylinder's foot pedal with my hand. I assume that this approach would work with other lifts that have adequate lifting capacity, but only you can determine what's right for your situation.
Notes:
1. Steve Beaver previously showed a lift made from two scissor jacks. If I could weld or could have a friend do it, I think I'd prefer his design. It would be cheaper, have multiple contact points on each skid and allow you to vary the lift front and rear.
2. I have to be under the glider wing to operate the hydraulics. You would need to decide how dangerous you feel that is for your situation(s). It is an understatement to suggest that I make sure the landing gear is down and locked before lowering the aircraft. A second line of defense is that lowering should be done slowly. I'd hope I'd see problems as they developed rather than as a sudden event. A third line of defense is that in it's most lowered position, the glider is still well above the room I'd need. But nothing's perfect.
3. The pressure release valve on this hydraulic pump is a plunger rather than a screw. It takes a very light pressure to lower slowly. A screw type valve would be better for my application.
4. I suppose it would be possible to use the lift to raise the airplane, then slide the trestle underneath, then lower the airplane onto the trestle. That might be appropriate if you thought it would be resting on the skids for a particularly long time.
5. For purposes of the photo, the lift is shown more forward. The actual lifting position is further to the rear of the skids.
Posted by jb92563 on Monday, January 24, 2011 @ 11:35 AM:
Looks like a good way to do it, with the motorcycle jack for good stability.
I use an engine hoist secured to the engine, although a sling at the firewall might be better.
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Posted by JamesB on Saturday, February 5, 2011 @ 02:45 PM:
Update on the lift --
We are doing the annual on the RF5B and did the first full test of the lift.
It was easy for me to raise the airplane. Going up was no problem.
But I had a hard time lowering the airplane gently. According to the directions, if you push the lowering lever down all the way (to release pressure in the hydraulic cylinder), it is supposed to lower slowly.
Not so. It does so smoothly, but it still comes down at a faster rate than I'd like. If I try to apply very little pressure to the lowering lever, it still comes down quickly. Releasing the lever causes a sudden stop...then you repeat. It comes down ok -- but not smoothly/slowly/gently.
I am going to check around the Seattle area to see if there is a shop that repairs hydraulic cylinders that can introduce a fix -- maybe even a simple screw that I can open slightly rather than this lever design.
So, the basic principle is good. I just have concerns about this specific lift without modification. Will share what I find.
