alcon
Post #1
To build a roll over jig (or rotisserie), I started by working out the best mounting points on the car. The front seemed fairly straightforward and I’d seen others using the two front chassis rails to bolt a frame to however the rear appeared a little more problematic. There isn’t any obvious mounting points and I wasn’t keen on drilling extra holes anywhere purely for this purpose. I considered using existing holes and mounting points on the rear chassis legs but this would have covered up sections of the boot floor, making the de-rusting and recoating process difficult. I had seen someone using the existing holes behind the bumper sides but this also involved the need for extra holes to be drilled through the body. In the end, I decided to use the three existing holes in the back panel which are behind the bumper.
The back panel is quite flimsy and I was concerned that it may bend under load. However I pressed ahead with this option and proceeded to measure up for some steelwork.
The critical size here is the dimension shown in the photo above with a red line. This turned out to be 75mm so I knew I needed some hefty box section to fill this gap without it being able to move around. I also discovered there is a very slight curve across this panel so I realised a single piece of box section wouldn’t work. I decided to bolt three sections of box to the three existing holes then weld a plate across the face of all three box sections. Even though the plate was going to be heavy duty, it would still be able to bend enough to take up the curved shape of the car panel. This would then give me a good surface at the correct height to weld the ‘pin’ to.
75mm x 40mm x 3mm steel box section
10mm thick flat bar
Once this was all welded up, I offered it up to the back panel and marked through the three holes which were then drilled out to 10mm. I could then pass an M10 bolt through from the inside of the box section and fix a large washer and nut on the back of the car panel to secure it.
Even after all of this, when I tried lifting the back end of the car up using the pin, the welded assembly made the back panel flex more than I had hoped. However, I realised than once the car was rolled through 90 degrees, the weight would be acting in a different direction and the flex would be eliminated. That was my theory anyway!
So back to the front, this was a lot more straightforward and felt rock solid as soon as it was all bolted to the shell. For this, I opted to utilise the two front chassis legs as there are already holes in the side walls which are convenient locations to pass bolts through.
I ordered up some 10mm thick steel plate for the two side mounts and cut these to shape so that the narrow end would slide inside the chassis legs.
I had to notch out some material on the nearside mount as it was fouling and preventing the assembly from sitting straight. The other side didn’t require any fettling. I realised at this point it would be impossible to get my fingers inside to hold a nut in place so had these tack welded on to make the installation easier.
The tube that would form the rotating axis point needed to be strong and I didn’t fancy relying purely on this being welded straight to the box section. So I cut up some 8mm plate and got it welded to the end of the tubes. I had 4 holes drilled in the plates to bolt it together however opted to just get it welded instead.
After some tarting up with POR15 it was ready to be bolted to the car.
So that the ‘pins’ had something to rotate on, I wanted to build a couple of stands. I thought about doing these in steel but that would have worked out more expensive and required even more welding. I knew they could be built from timber as I’d seen someone on YouTube doing something similar but I was concerned by their design not looking strong enough. So I designed my own.
The base would be 18mm thick plywood and the upright parts 145mm x 50mm C16 structural grade timber. After cutting everything to size, it was then glued and screwed together.
All the joints were caulked and two cut outs were created in the top to receive the pins. I also added some lengths of CLS timber to the bases to reduce the area that would be in contact with the floor. My thinking behind this was in case the floor was ever wet and plywood doesn’t always like sitting in puddles. However as it was exterior grade ply, this may have been overkill.
Primed and painted with two coats of satin black exterior timber paint.
They turned out to be quite heavy and awkward to move around so I knocked up a couple of handles to make life easier.
Back in the workshop, I had test lifted the back and front end on my own and both were relatively east to lift to a decent height. However, I discovered that when I lifted either the back or front end onto the timber stand, it was impossible to lift the other end by myself. So after enlisting the help from a couple of mates, we were able to lift both ends up and onto the stands. I had added some self adhesive felt into the two cut outs or saddles and this made turning of the two pins much easier and less jerky, especially since they had been coated in the POR 15.
This photo gives an idea of the height the car needed to be lifted from the dolly up and into the saddle.
Once it was up on the stands, it rolled over easily and all concerns regarding the flexing in the back mount were alleviated. As the car rotates through 90 degrees, the load axis still remains vertical therefore the back panel can no longer flex. By avoiding use of the rear chassis legs, the whole of the underside was now fully accessible. The strength of the timber stands turned out to be quite impressive and they don’t move at all. They may have been slightly over engineered but better safe than sorry!
The jig was designed to allow the shell to rotate through 90 degrees in either direction. I wasn’t wanting to roll it right over through 180 degrees as these cars are so top heavy when stripped, it would have been difficult to control the rolling over. To prevent it from rolling past the 90 degree mark, and to make sure the shell was secure when working on it, I made a stop from a piece of timber. This was simply a length of CLS cut to length and then bolted to the front of the shell. I used the convenient holes on the strut towers to bolt the timber to.
It’s worth mentioning that one of the critical dimensions to check is the distance from the centreline of the car to the widest part of the body. This will dictate how high the stands need to be. You also need to add a bit onto this to allow the body to clear the floor when rolled onto it’s side.
Total costs were:
Metalwork = 94
Woodwork = 48
Welding = 30
Nuts, bolts & washers = 14
TOTAL = 186
There’s no need to paint anything, I just decided that as I'll be seeing a lot of it, it was worth making it nice looking. I did look at buying a purpose built roll over jig but they’re over £400 by the time you include delivery. They also tend to be a ‘universal’ fit and so need a bit of extra work to make them fit your shell. I built this for half the cost and it works just fine for my needs.
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1999 GTi-6 (china blue)1999 Rallye (black)
Posted 3rd Mar 2021 at 18:51
