Portable Pinball Lift
I've been mostly happy with my Redneck Pinball Dolly. The problem with the dolly is that it's heavy and huge and it doesn't do stairs. Often a simple hand truck is the way to go. But I'm still not willing to use my back to get the rear legs on and off a game. Here's a pinball lift idea I first saw on Pinside around 2017. My primary goal for this project was portability.
The lift is based on a 30", 5,000 lb. RV stabilizer jack. The advantages of using an RV-specific jack are that the jacks tend to have a long reach and are easy to use with a cordless drill.
DISCLAIMER: Strictly speaking, an RV stabilizer jack is for stabilizing, NOT jacking. The jack seems adequate for my purpose, but what do I know? I am not a mechanical engineer. I built this lift based on what "looked right" to me. If you're dumb enough to replicate my example, you're on your own. Notwithstanding, I wouldn't recommend leaving the lift unattended or using it around rambunctious kids or pets.
Orientation Note: I'm utilizing the jack upside down. When I use words like up and down or top and bottom, I'm referring to my orientation, not the jack's intended orientation.
Game Set Up
The front legs are bolted on and the lift cradle is placed under the rear bottom edge of the game.
The game is rotated onto the front legs and lift cardle.
The jack is centered under the lift cradle.
The game is jacked up and the rear legs are bolted on.
Done!
The above process is reversed for taking down a game. This system is way easy to use. The game is easily rotated on the lift cradle and the jack works great. Even my old low-voltage cordless drill had no problem lifting a game. Assuming the front legs are firmly bolted in place, the lifting process is reasonably stable. Note, however, that the back of the game follows a slight arc as it's raised and lowered. Expect some slippage between the front legs and the floor and/or between the jack foot and the floor and/or between the lift cradle and the game and/or between the lift cradle and the jack.
Some slippage may be expected.
The portable pinball lift consists of two parts - the lift cradle and the jack. The lift cradle acts something like a cam where the game is on the floor when rotated on end, but is off the floor when rotated toward horizontal. The cradle gives the jack space to operate. The cradle can't be too small because the jack won't work from its folded flat position. The jack requires a minimum starting height before it gains any mechanical advantage. The higher the starting height, the easier the jack will operate.
My cradle is 12" by 12" by 12" with a 12" radius. It's made from ½" plywood with plenty of bracing at the joining corners. I added a piece of aluminum angle that fits under the game kind of like a hand truck. I also added a pair of alignment blocks on the underside of the cradle for centering the cradle on the jack pad.
Lift cradle.
Lift cradle.
Lift cradle.
Note: There is a potential stability issue with the cradle where the game could roll back over top of the cradle as the game is rotated near horizontal. Actually, this 12" cradle seems pretty stable. I didn't recognize the issue until I attempted to build a larger 16" cradle (see below). Nevertheless, if I had to build this 12" cradle again I'd think about making the top of the cradle rectangular instead of square. Perhaps 12" by 14". Look under "Lift Cradle version 2.0" below for more analysis. In any event, when rotating a game, it's important to apply force only in the direction of rotation. Never push the game horizontally back toward the cradle.
I wasn't too happy with this jack as it came out of the box. It took an excessive amount of force to fold it flat because the inner scissor members didn't fit well into the outer members. I used a bench vice to slightly crush the inner members.
Crushing the inner scissor members to get the jack to fold flat.
That's better.
Don't forget to buy a cordless drill adapter.
I added a ½" plywood pad to the top of the jack. The tab extending from the far end of the pad helps balance the cradle in place when the cradle isn't snugged up against the bottom of a pinball machine. Another small alignment block centers the jack under the lifting edge of the cradle. In the interest of portability, I added a folding handle made from scraps of hardware.
Jack pad.
Folding carrying handle.
Below is a detail shot of the handle arrangement. The handle shafts are long machine screws. I cut a shallow slot in the pad and pressed the shafts into the slot. One end of each shaft is held by a small screw. The other end of each shaft is simply pinched between the pad and the jack itself.
Underside of jack pad.
Interlocked alignment blocks.
Interlocked alignment blocks.
The jack has a big round mounting bracket which I thought would make a good stable foot. I add a ¼" plywood pad to protect the floor.
Bottom jack pad.
It wasn't my intention to use the manual crank that came with the jack. But I also didn't want to lose it. I cut it down to a more manageable size. Then I drilled a pair of holes to store it in the lift cradle.
Cut down crank.
Crank stored in the lift cradle.
Crank stored in the lift cradle.
Lift Cradle version 2.0 (fail)
2020
16" and 12" lift cradles.
16" lift cradle.
16" lift cradle.
I was initially thinking about the lift cradle in terms of portability and its minimum possible dimensions. I think my original 12" cradle represents the smallest practical size. It could be a bit smaller, but then the jack would work much harder. What about bigger? Maximum cradle size would be limited to the length of a pinball machine's legs or about 22". But a 22" lift cradle would be bulky and huge and force the operator to do most of the work that the jack is intended to do. Would a 22" cradle even work? Or would the game pop back up on its end like a giant Weeble?
Instead I decided to build a 16" by 16" by 16" cradle. This time I used ¾ plywood and I rigged a circle jig for my router. This made for a smoother, more consistent cradle radius. Otherwise, the new cradle's construction was much like the old.
One problem with the larger cradle is that it's too front-heavy to balance itself on the jack pad. Not a big deal, but it would have required a bit more care when positioning the cradle and jack to take down a game. I added a small peg to the jack pad alignment block which engages a hole on the rear edge of the cradle. The peg prevents the cradle from tipping forward before it's snugged up under the game. For compatibility, I added a similar hole to the original small cradle.
Cradle balancing peg.
At first I didn't bother to recess the length of aluminum angle. But the exposed edge can be a potential hang up if not paying attention. So I went back and added a recess to both cradles.
Aluminum angle recess.
I finally got around to testing the 16" cradle on a game and it didn't go as well as I had hoped. There were some positives as compared to the 12" cradle. The game was easy to rotate. The jack's starting point was 4" higher so the jack worked even easier. The jack's vertical travel was reduced by 4" which reduced the arc-induced slippage effect. So in theory, bigger should have been better. The picture below illustrates the problem I ran into.
Most of the game's weight ended up on the front edge of the cradle which was directly over where the cradle contacted the floor (red arrow). Thus the front edge acted as a pivot point. Since there was little weight on the front legs and the game was still sloped back, the front legs had no traction on the floor and tended to want to slide back. Note how the back of the game is no longer in contact with the cradle. The front legs have already slid a bit and the game wants to pivot back over the front edge of the cradle. So I think the main problem here is that the larger cradle puts the floor contact point too close to the game's horizontal center of gravity. This is not a problem I had with my smaller 12" cradle.
The game wants to pivot back over top of the cradle's front edge.
My immediate solution was to add a strap as shown below. Interestingly, I had cut those big holes on a whim thinking they might be decretive or act as handholds or something. The strap is not something I had anticipated. But include the strap and the cradle works great. Nevertheless, I'm calling this a fail because the strap is an extra step in a system that was supposed to be simple and easy.
The strap solution.
I don't know when I'll get around to further experiments, but I have a few ideas. I might make the top of the cradle rectangular instead of square. Perhaps 16" by 18" or 16" by 20". The rectangular top would extend forward (see red line in the picture above) such that there would be no front edge pivot point directly above the cradle's contact point with the floor. And instead of cutting quarter circles I might cut quarter ellipses. Let's say 16" tall, but only 14" deep. Such would provide the same elevation, but put the contact point with the floor further from the game's horizontal center of gravity.
In fact, I have successfully incorporated these ideas into my Redneck Pinball Dolly version 2.0. This means that the 16" lift cradle has become somewhat redundant and I may not get back to it. Update: it went in the campfire.
