Problem to solve

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I am building this motorcycle lift.  the problem I am having is keep the platforms from pitching or see sawing forwards and backwards, left and right as I lift the bike off the ground.  the platforms will rise with the use of a scissor jack. one under each platform facing parallel to the lift frame on the bottom.  as you crank the rear scissor jack and raise it there will be a drive shaft that is connected from that rear scissor jack to the front scissor jack.  as you raise the rear jack it turns the shaft which cranks the front scissor jack allowing both platforms to raise at the same time and rate.   the bike will be lifted nice and level as it sits on the platforms.  At least that's the theory.  i haven't welded up the angle iron posts to the front platform because I want to figure out how to keep the platforms from rocking forward or backward, right and left.  Any help or ideas would be welcomed.  I am attaching a couple pic's to show you the basic layout.thanks Attached Images
Reply:I'd think with a jack at each end it wouldn't tip front to back.  Depending upon the kind of jack it probably wouldn't slide front to back either.  Guide rails on the front and back would help with sliding if that is a problem (see below).Tipping left or right might be more of a problem.  If you're going to be using it at the same height each time then you can put swing-down legs at each corner, raise the platform/bike, swing the legs down, then lower the platform onto the legs.  If you want different heights you could make them telescoping with pins.If you want to get fancier you could put fixed vertical guide rails at the front and back near the corners.  "X"-brace them so they cannot move toward one another.  Then attach guides to the platforms riding on the outside edges of the rails so if it tips left to right it would attempt to squeeze the rails togather.  Rig up an eccentric cam on each guide and you can then lock the platform to the rails to work on the bike.Hope this helps.
Reply:The type of jack i am using is a scissor jack.  it is the only jack i know that when compressed is not very high.  the drawback of a scissor jack is that the top of the jack that supports the weight of the vehicle is only about 2" square.  not a lot of surface area to mount to.  On the guide rails would you recommend still using wheels or just have something that guides along the rail that is metal?  I went the wheel approach because i thought metal on metal would cause too much of a drag and bind up.  thanks for the help and I am open to all opinions and suggestions.Last edited by ranger28; 03-30-2005 at 07:57 AM.
Reply:If you extend the jack can you then push the top forward or backward (parallel to the jack screw)?  That's what could cause the platform to slide front to back.  Looking at the pictures in more detail it looks like you are using guide rails at the front and back.  That should prevent this sliding.Wheels or rollers are good, for the reasons you state.  The only question is their orientation.  It looks like they're pointing out from the front and back edge of the platform into the guide rails.  Not sure that will help with side to side tipping.  If the platform tips the wheels will then just bind in the guides.  Maybe consider turning the wheels and guides 90 degrees towards the middle.  That should keep the platform from rolling by the wheels pressing into the guide rails.  Then you could also put an eccentric cam above or below the wheels or on the inside of the rails that will lock the platform in place.Good luck
Reply:http://www.afabonline.com/table_lift_plans.htmshows enough photos you should be able to work it out, but the plans might be worth the money as well.