Lifting gantry.

[Park_monkey]

hello all.
I have a chain block and tackle, and want to build a couple of a frames with a crossbar to enable me to use it. It's only a 500kg hoist and I plan on using it to lift engines out of cars but also I would like to be able to put it on the back of my recovery truck so I can lift the back end of a car up to drive another underneath, enabling me to put two cars on my truck. The reason for this is I race bangers and hire them out so regularly have two on my truck and one on a trailer.
What spec steel would I need to use? I would like it height and width adjustable, I was thinking around 75mm box for the main uprights, with slightly smaller inserts that I can slide in and out to make it taller or shorter. It won't need casters when on the truck but it would be useful if I could put some on to move it around on the floor. Will box section be ok for the crossbar to will I need I beam?
Any advice on steel sizes greatly appreciated, it won't be carrying any massive weight so the lighter the better.
Thanks
Dale

 

[Kent]

Lifting gear needs testing if its for commercial use and certifying not sure about personal use. Design specifics will be a big factor on which materials

 

[stormin]

When you say lifting a car up so you can get another underneath, what is supporting the car during transport? Do you still intend the A frame to support the load or are you lowering the top car back down onto the lower one? If you really intend the A frame to take the dynamic load it's going to need some serious strength to take the cornering and bump induced loads. In fact the A frame will likely end up so heavy you need lifting gear to get it on and off the truck. It's probably best to construct two separate frames one for each job.

 

[Park_monkey]

During transport the top car will be strapped down to the other one. It won't be supported by the lift.