I thought I post these images from the workshop manuals of how the 109 ambulance anti-roll bars are fitted. I’m only fitting the rear bar, and as mentioned have had to be a little creative because the main span of the bar normally passes through the area occupied by a 109′s rear fuel tank, where fitted (MoD 109s, including FFRs , GS models and ambulances, use twin front tanks and have no aft tank).
The solution was to swap the spring plates around so that their arms and the vertical links sit ahead of the axle instead of behind it, allowing the antiroll bar and its mountings to sit directly behind the bump stops, clearing the fuel tank and the axle on full spring compression.
I am having mounting brackets similar to those welded to ambulance chassis fabricated for bolting on to the rear chassis rails, just behind the bump stops. The brackets are to be made of 5mm steel plate to make them rigid, and as such I won’t need to it anti-crush tubes to the bolt holes I drill through the chassis – the bolts and nylock nuts will be nipped up but not over tightened.
In the end, the chassis brackets had to be fitted with a pair of captive nuts fot the D-bush clamps. These were just M10 nuts welded to the top side of the holes in the bottom face. To spread compression loads, steel trips were welded along the corners to sit against the corners of the chassis rails, preventing the captive nuts from crushing the underside of the chassis. The brackets thus stand off the chassis a little, and the bottom bolts do not go through the underside of the chassis at all, leaving the main rail bottom undrilled and at full strength.
The brackets were drilled with three holes per side to take three straight-through high tensile bolts. This triangular formation not only spreads the forces across a larger area and reduce the risk of a single bolt elongating its hole over time, but also eliminate the possibility of the bracket rocking around a single bolt and gradually causing wear or damage. The bracket dimensions are unchanged, though.