Going for a spin

I had always thought a hoist was the only option for working under a car - until I saw a "vehicle rotisserie" recently in a car mag'. This just made things look too easy so I had to have one. I assumed it would cost quite a bit so I went out and bought the steel, threaded rod, a few large steel washers and a nylon cutting board - as the component parts.

On a couple of mornings where I woke up early, I just thought about how to build it and the results are as you see in the pic's below. First problem was how to make an "adjustable centre of gravity" mechanism. It is no good just bolting the body to a spinning axle - as I am going to first remove a heap of floor metal and then add a heap of box tube for the new chassis. This means the car body would "pendulum" over on its roof as the floor got lighter, and then the opposite would happen as the chassis went in. All this making it much harder rotate by hand when it was out-of-balance at any particular progress point.

So first the adjustable "centre of rotation" sleeves were built...

Basically, this involves welding the round pipe (which is to be the rotisserie "axle") to a metal sleeve that can run up and down outside some box-tube steel. See the picture below.

Notice that i've welded some decent nuts to the sleeve so that when I spin the threaded-rod the sleeve moves along. The threaded rod can only spin (can't slide) as i've welded decent washers to each end. Skate-board wheels make a great handle and as you can see I gave the handles plenty of leverage (length).
Additionally, I cut up a nylon cutting board and inserted slabs of it into the sleeve so that they run smoothly run up and down the tube. No metal on metal grinding here!
The sleeves get about 800mm travel via the threaded rod - plenty to adjust the centre of gravity of the car shell as I remove and add metal (weight) as I work on it.

There are in fact 4 pieces of nylon at each end of the sleeve separated by plywood "spacers".

Next I needed to make the frame that supports the sleeves. There is an "A" frame at each end, trolley wheels so I can move it all around and a length of box-tube to tie each "A" frame together. See below....

The sleeve axle is simply supported in the "A" frame by a custom made "cup". The cup being another piece of 2" pipe, but cut in half lengthways and opened up slightly for a snug fit. I've G-clamped the sleeve axle to the "A" frame cup in the photo above.

I figured the easiest way to put the shell onto the rotisserie was to jack the shell up to what looked like the right height - and then weld it on. See the photo below. I'm sure WorkSafe would have just loved my temporary stands, but the whole thing was actually very stable.

Now this is a very important bit. As I am going to cut out heaps of the floor, sills, torque-boxes, do frame-rail repairs, etc, etc - I can't just bolt or weld the body shell to the sleeves at each bumper - as the body shell will sag and bend in the middle when I try and spin it. I have to build a rigid "space frame" inside the car and weld it to the body-shell at multiple points. The space frame has to be rigid thru a full 360 degree rotation so multiple diagonal struts need to be included.

The first bits I did are seen below - diagonals from the top of the rear sleeve, passing down to each inner sill and incorporating bolts to firmly connect to the rear shock mounts mid-way. There are no instructions for this. I just made it up as I went along. Hopefully some "common sense" crept in at times. The wooden "jigs" you see below are holding the first of the next set of diagonals - coming from the bottom of the sleeve up to the roof.
Also - note that I had to cut out large parts of the rusty floor first - to be able to get to the points on the sills where I had to weld to the space-frame.

OK - here (below) is the rear sleeve all welded up. Note that the body shell is still sitting on its stands - and my little helper just has to be a part of the action.

Time now to run diagonals up to the front sleeve - see below. These are quite long pieces so I used 2mm wall tube for these to reduce anticipated flex.

Here is a closer shot of the diagonals reaching the front sleeve - see below.
You can see the sleeve axle is just sitting in its "A" frame cup.
For the record, tube dimensions are......
All tube is 50mm square box section.
"A" frame and sleeves are 3mm wall thickness.
Space frame is 1.6mm wall - except for upper longer lengths running to front sleeve which are 2mm wall thickness.

Here you can see that i've removed the stands and the shell now spins. Note the angle it went to - it must be heavier on one side (or I didn't weld it exctly in the middle). I actually suspect there is more frame rust (less metal) in the side that sits higher - hence the lean. This shot also shows the "captains wheel" I welded on to the sleeve axle to make it easy to spin the body.

And below is the first time I rolled it out to spin it. However, a design flaw was evident in that the space-frame struts sticking out under the sills hit on the box tube connecting the front and rear "A" frames. Bummer, more work!

So I modified (shortened) them as seen below. Now it spins 360 degrees for easy access to the whole shell. The adjustable sleeves are fantastic. I can shift the centre of balance to be neutral so that it's balanced and spins easily - or I can shift it off neutral to make the shell "pendulum" to an upright or upside down position. I was going to incorporate a locking mechanism to hold the body shell in certain positions - but i've found a simple chock does a great job.

Here (below) is a detail shot of the rear of the rotisserie - nice and structurally sound. No flex is apparent anywhere in a full rotation.

And below is the final incarnation. I lifted the axle "cups" up 2" and had to modify a rear "A" frame brace to clear the body shell tail-lights during rotation. Notice that the trolley wheels are in groups of 2 and pivot in the middle (see the centre bolt for each pair?). This means all wheels carry the same weight even when rolling and the floor is uneven. I figured that if these wheels were solidly welded to the "A" frames then i'd risk a trolley wheel collapsing if it temprarily took too much weight running over a bump.


Now that I can get to all parts of the body I can finally move from the preparation phase to actually restoring & enhancing the car..... but that's for another set of posts......