Restoring an old car? Or performing major bodywork? Either way, a spit for your car can make things a helluva lot easier. But there are also some downsides and major traps in using a spit - so let’s take a look at the whole topic.
What they are
A spit, sometimes called a rotisserie, is a metal frame designed to support your car’s body from each end, holding it up in the air. Most designs comprise two large end assemblies joined by a long stabilising bar that passes under the car just above the floor.
As its name suggests, a spit allows the car to be rotated, so letting you work on the underside of the car. To illustrate this, if you need to grind the underside of the floor clean of paint, or massage-out some dents, having direct access to the bottom of the floor will make the work much easier to do.
Spits can be home-made or purchased new. Occasionally, second-hand home-made items also appear on eBay.
All spits have a means of supporting the car and a pivot axis around which the car can be turned. The car can normally be locked at any point in rotation.
The most elaborate spit incorporates two hydraulic jacks, one at each end. In addition, threaded rods are provided that allow the car attachment arms to be wound up or down. (Once the car’s weight is correctly on the spit, these threads are locked and the hydraulic rams do the lifting work.)
The reason for this apparent complexity needs a bit of explanation.
The arms of the spit attach to the car, normally at the points where the bumpers bolt on. However, because bumper height varies from car to car (and sometimes even from the front to the back of the one car), the threaded rods are used to adjust the height of the attachment arms to match the car.
These threaded rods have another, very significant function. If you imagine the axis on which the car is to rotate, and place an equal amount of the car’s mass above and below that axis, the car will be able to be spun by hand. If there is more mass above the axis than below, the car will want to topple over – to always turn upside down. The threaded rods, together with an external jack (eg a trolley jack) can be used to position the car closer to, or further from, the pivot axis. This allows you to match the pivot axis to the distribution of mass in the car.
With this type of spit, once the car is on it, the screw threads must be adjusted so that the distance between the car attachment points and the pivot axis is the same at each end. (Again, when making this adjustment, you’ll need to use a separate jack to take the weight off the threads, or alternatively, jack the car with the inbuilt jacks and then lower it onto some supports.) If you don’t perform this vital step, which is not mentioned in some instructions, the car will be hard to turn and may even break its mountings or damage the spit itself.
(On spits without screw thread adjustment, the car must be manually jacked to exactly the correct height for attachment.)
With the car attached to the spit and set up correctly, the hydraulic jacks can then be used to raise the car to a height sufficient to allow it to be rotated without hitting anything on the ground. Each jack must be operated simultaneously – again, you don’t want to bend your brackets or the spit.
If you buy a spit without hydraulic lifts or screw thread adjustment (some homemade designs), it’s likely that:
1) The car will need to be manually lifted a long way (eg 1.2 metres or more) before it can be attached to the spit at a position appropriate to the rotational axis and sufficiently high to let it rotate.
2) You will need to climb a small step ladder to do some of the work on the car (eg to work on the upper panels)
There is a lot of balderdash talked about the capacity of different spits. The one I bought purports to have a 1000kg rating but is safe (IMHO) at only about half that. In all cases, before being placed on the spit, the car should be made as light as possible (no engine or gearbox, and preferably no interior, no doors, no glass, no suspension or wheels).
There are two areas of major weakness in a spit.
The first is that the forces acting on the pivot points are very large because typically, the car is positioned 400mm or more from each one. (Any closer and you can’t work on that end of the car.) Any bending in the mounting brackets puts great leverage on the pivots and their supports.
Secondly, the strongest attachment points to the car are normally the original bumper attachment holes. But getting sufficiently strong brackets to these holes can be problematic – there is often not much space. And remember, you are lifting the car from these points…and also remember, the brackets need to be as laterally strong as they are vertically, to cater for turning the car on its side.
In all cases, you will need to make your own high-strength, custom brackets – and so have welding facilities and the tools to cut heavy steel. Make sure when mounting these brackets that you use high tensile nuts and bolts with large diameter washers or load-spreading plates.
Setting the Car Up
I bought a fully-featured spit from Ozmestore on Australian eBay. It cost, including delivery from Adelaide to Canberra, was about AUD$1200. The packing crate and its contents had a mass of 250kg.
Lacking any decent instructions, I initially made a number of errors in set-up. (These I have covered above.)
The successful process was as follows:
Step 1: I made brackets to connect the spit arms to the car’s front and rear bumper bracket holes. After initially making some brackets that proved insufficiently strong (I wasn’t happy how they deflected under the loads), I used thick steel angle.
Step 2: I then drilled one extra hole in each spit arm to allow each bracket to be held to the spit by two 10mm bolts, not just the one the original design provided.
Step 3: I then rotated the spit threaded rods to set the arm height to match the bumper mounting points, then bolted the spit arms to the car using brackets and high tensile 10mm nuts, bolts and washers.
Step 4: An external jack was then used to take the weight off the screw threads, allowing them to be adjusted so that the distance between the mounting points and the rotating axis was the same each end.
Step 5: The spit’s hydraulic jacks were then used to evenly lift the car, with its rotational stability then assessed. In my case, the car was still clearly a lot heavier under the rotational axis than above it – it was hard to turn past about 20 degrees. This meant I needed to then…
Step 6: Lower the hydraulic jacks, use an external jack to lift car and then use the screw threads to locate the mounting points closer to rotational axis.
Step 7: The hydraulic jacks were then lifted and stability again assessed.
I needed to do the last few steps a few times until the car was easy to rotate to 90 degrees.
If you are working alone, by the time you make the brackets, assemble the spit and then set the car up on the device, you’re looking at a full day of work – perhaps more.
· If the car is hard to turn and the centre of gravity height adjustment is correct, it may be because you have one end of the car mounted further from the rotational axis than the other end of the car – and this will bend your brackets when you attempt to rotate the car!
· Car bodies are often heavier than you first think – and so the mounting brackets need to be as strong as you can make them.
· Watch very carefully for signs of overload – bending of brackets, cracking of welds, deflections that are visible to the naked eye. Don’t forget that as you turn the car, some of the forces acting on the spit and the brackets change in direction and magnitude.
· To put this in context, I think that a spit is much more dangerous than ramps or jack-stands. Furthermore, I wouldn’t get under a car supported just on a spit.
So with the substantial cost and the fiddliness – not to mention hard work – in setting up, is having a spit worth it? The answer is ‘yes’.
If you are working on a car body, it simply makes it so much easier to be able to set you own convenient working height and direction, and rotate the car to match that. For example, I cannot gas fusion weld upside-down, and I especially cannot fusion weld upside-down when working with 1mm thick material! But with the spit, you don’t have to. The welds can always be beneath your hand.
I have also found when panel beating, when making measurements (eg to assess engine swap possibilities) , when removing fuel lines and altering brake lines, that the spit is invaluable.
I expect it to also prove its worth when installing a new fuel system (pump and lines) and new brake lines. Painting the vehicle’s underside should also be vastly easier with the spit.
Finally, the spit I purchased is on large castors and so the car can also be easily moved around the workshop.
Treat the equipment with the care and respect it deserves (that’s your car’s body up there in the air!), make strong mounting brackets, and set the car up on the spit very carefully, and you too will find it eases your path to working on a car.
The spit was purchased at normal retail price.