My homemade cycle lift table

sketchy (dirtbikes, ok)
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[tkent02]

Also I don't think anybody has an issue with the strength of the upper or lower boxes; it is the struts and attachements between.

Exactly, and once it starts, it will shift diagonally as there is nothing to slow it down. Slap some plywood across each pair of struts, then it can't shift.

[posplayr]

I agree with Pos. I tried this with 4 legs like you did, and found there to be too much sag involved, which, in my case, lead to a certain amount of binding. I knew if I added middle legs, it would help the whole thing maintain geometry, but at that point, I had honed in on another concept. That one involved the table also being the ramp. Front legs became solid, and devised two sets of rear legs: a shorter, solid pair, and a longer, hinged pair, that, when dropped down once lifted, get locked to the shorter, sold-mounted pair. Works like a charm and I no longer have to worry if the whole things gonna come down on liftoff.

Did you ever post pictures?

[posplayr]

Screwed with 4 inch deck screws, construction wood glue, and 2X4s in the corners where the lock joins in..all screwed and glued. Its not gonna twist, roll, drop, sag, fall or anything else. If I wasn't 100% sure of that, there sure as hell wouldnt be mine or anyone elses bike on it!!!

The weakest link is the 6" or so of the end of each strut (on the jack side). Because the back (away from jack) is cantilevered it is putting the front strut under tension (pivoting about your lock which is in compression) . So if that end grain split the bolts would pull right through and the thing will come right own. That is why I recommended a side plate to prevent that from happening.


Also I don't think anybody has an issue with the strength of the upper or lower boxes; it is the struts and attachments between. Note that your upper and lower boxes are not parallel.

[tkent02]

It looks weak against diagonal shifting.

[chuck hahn]

The plywood also acts as gussets by the way...no twists.

[chuck hahn]

Screwed with 4 inch deck screws, construction wood glue, and 2X4s in the corners where the lock joins in..all screwed and glued. Its not gonna twist, roll, drop, sag, fall or anything else. If I wasn't 100% sure of that, there sure as hell wouldnt be mine or anyone elses bike on it!!!

[tkent02]

What do you have to brace it from shifting diagonally?
I see no triangles.

[chuck hahn]

2XR frame both top and bottom, 2 stringer evenly spaced and 3/4 plywood and I gotta worry about sag???? Yeah right.

I agree with Pos. I tried this with 4 legs like you did, and found there to be too much sag involved, which, in my case, lead to a certain amount of binding. I knew if I added middle legs, it would help the whole thing maintain geometry, but at that point, I had honed in on another concept. That one involved the table also being the ramp. Front legs became solid, and devised two sets of rear legs: a shorter, solid pair, and a longer, hinged pair, that, when dropped down once lifted, get locked to the shorter, sold-mounted pair. Works like a charm and I no longer have to worry if the whole things gonna come down on liftoff.

[chuck hahn]

Its actually pretty solid with the weight on it. I need a stiffer jacking plate at the bottom though. It 3/4 plywood right now. I am thinking to keep my eye out for a sheet of steel. The plywood bows slightly as the jack forces the plate and the table way from each other. It actually sits level once the jack is let down so the lock is in place. Has had Matts 79 1000 on it for 2 days now and nothing wrong.

[posplayr]

Doing an eye ball statics analysis it looks like the lift has most of the load cantileavered out well beyond the support of that weight( e.g. 500 lbs down at the center stand with only a minimum 50 lbs or so on the front wheel). The struts away from the jack is probably neutral with essentially no load. You could probably just take it out. The primary support is coming from the stop and the jack. The strut closest to the jack would appear to be in elongation. The jack is trying to stretch it. I think thAt strut closest to the jack is most susceptible and could easily bring the whole thing down.

Is the bolts are being pulled by the jack then the strut end grain could split and the bolts would escape letting the whole thing drop. To make this substantially stronger I would make so metal reinforcing plates that capture the bolts and prevent the strut from splitting. A simple 1/8" plate with holes for deck screws to go into the strut would make a big difference.

I have not studied these lifts much but I would assume the lift would want to come closer to where the load is and definitely support from I between the struts. That way both struts have similar loads and be more balanced.


EDIT:
OK I did a little further study and came to the conclusion that while this configuration is not quite as stable as it could be, it does have some excellent potential for making a very stable and cheap motorcycle lift.

After looking at the harbor freight lift it appears that the primary issue is to get sufficient lift (29") out of a hydraulic bottle jack. You do this with reverse leverage so that the short stroke of the bottle jack can be used to get much longer lift. The typical 2 1/2 tone floor jack performs this function pretty well and that is a big plus and opens the door for a nice lift for very little cost while also leaving the floor jack available for other uses.

So in looking back at Chuck's design, it is cantilevered but that is really what makes it weak and with a little effort it could be made quite a bit more solid/stable.

Stepping back and looking at the lift, it is pretty easy to see that the struts are each emulating the same motion that the Jacks are has. The jack uses a lever arm to get the full lift 29" from a short bottle jack. See the inset for a floor jack from HF for less than $100 that has a full 29" lift. With a 13" resting double 2"x6" (with platform)stack height you can get the bike up to 42" if you wish.

One of the issues with Chucks is that it is lifting at one end and sagging at the other so the struts are not maintaining the upper and lower boxes in parallel. By adding a third strut the whole thing cant get nearly as much out of parallel and it even strengthens the lift further. It is going to be more critical to se straight boards and cut all struts to same length and drill the bolt holes in the same place.

Next I would put the adjustable stop at the opposite end to the jack so that when resting on the stop there is not a cantilever but rather a balance of load with the 500 lbs of center stand in the middle.




Conceptually this would make the whole structure much more stable but I think I would go another step although it would require some more lumber. The 6 struts with the stop on opposite ends of the lift will create a much stronger lift in the length wise direction, but laterally it could still use some reinforcement. One way at least would be to double up on upper and lower boxes in order to support the bolts on both ends. This will stop a lot of the side ways motion due to bolt flex. If you bump up the struts to 2"x6" it will also make the lift laterally much stiffer. Bear in mind you will need to be more precise in the construction but it probably is just going to take a little more care. For example in order to space the 2"x6" so that the structs will move but drop into the double box section you will need to shim other fixed 2"x6" spacers. Anything will work depending upon how much twist your 2"x6" have.






This should cost $75-$100 depending upon what you have laying around assuming you already have the jack. With the upgrades I suspect that you could put a full dresser Harley up on the rack. The struts will not be quite as far apart if you want to maintain the platform width the same, but it will hide the struts as they are not outboard of the platform and help avoid getting anything pinched.

[chuck hahn]

Like I said Jeepster..I am not ready to roll over and play dead just yet!!!

Glad yrer hanging in ther Chuck

[chuck hahn]

If nothing else, I am not satisfied with "just getting by". Last 3 years in reality have been VERY VERY stressful for me. I tried what seemed like a promising spot in Texas and it wasn't what I was led to believe..so switch it up and try something else.

Thing is that life is like boxing. The boxer can have the very best training and the top of the sport corner men etc etc. BUT if the boxer doesn't rise of the stool at the bell the game is over, and I refuse to capitulate under any circumstances...ever.