My homemade cycle lift table

[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.

[Road Rash]

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]

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

[tkent02]

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

[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!!!

[chuck hahn]

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

[tkent02]

It looks weak against diagonal shifting.

[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.

[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?

[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.

[ptexotik]

sketchy (dirtbikes, ok)
next

[almarconi]

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.

While your analysis is interesting, I doubt it is relevant here. This is Chuck we are talking about. I doubt he gives a sh#$ about whether you like the design of his motorcycle lift or not. If he is comfortable using it then more power to him.

[rustybronco]

The plans I've seen for home made motorcycle lifts had the floor jack slid further under the table.

http://motorcycleliftplans.weebly.com/index.html

http://www.afabonline.com/table_lift_plans.htm

http://www.millerwelds.com/resources/communities/mboard/attachment.php?attachmentid=1225&d=1174412234

[tkent02]

While your analysis is interesting, I doubt it is relevant here. This is Chuck we are talking about.

If it starts to fail he can just stick his hard head under there. That will save it.

[chuck hahn]

True Dale but I mismeasured how far the jack had to go under and had already glued and screwed the first front cross member in...so it has to be what it is.

The original scenario was gonna be 2= 2X6s married together about 12 inches in from the front plate..thus allowing the jack to lift further back and also have the force displaced along some of the decking. Much the same principle as weight is spread across the decking and joists in house building...so much joist spacing + the thickness of the deck will support X amount of weight per square foot..blah blah.

But overall we have max of 500LBS spread across a 8X2 deck made of 2X6s with 3/4 plywood. 3 cross members in the table top also, so I feel I am way over the spread as far as how much actual weight it will support. Do you think so Dale?