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.
Edit:
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.
Thankyou for putting up the nice detailed drawings about the anti-roll bars.
Do you have the list of parts that gives names and LR part numbers to the items in the drawings?
Did you ever make the Mark 2 drawing of your revised mounting bracket?
And of course – have you any photos of the completed installation you can put up? (Perhaps amalgamate the two Anti-Roll bar articles? I don’t know the work involved.
Thanks.
The photos of the completed installation are on the Anti-roll Bar Fitted post; if you select “Suspension” from the navigation menu on the right, you will find that post more easily.
The photos show the slightly extended mounting brackets, which were modified to create a bolt fixing point with plenty of meat on it aft of the chassis’ fuel tank bracket, however, the fabricator made the extensions too shallow to allow this, so the fixing bolts all run through the original section of each bracket and the alteration was unnecessary. The photos show a cut out on the inboard vertical face of each bracket, which is all that is needed to clear the fuel tank bracket.
The exhaust routing had to be brought slightly inboard to prevent the exhaust fouling the rubber D-bush, but that was fairly simple.
I don’t have any part numbers as I do not have the optional parts catalogue, but any LR part supplier should be able to help.
Nice bit of info. Have you an update on how handling was changed?
I am considering this modification to our Dormobile. Would you mind measuring the diameter of the bar and the length of the bar arm? It will probably be easier for me in the USA to find a local version with the same dimensions than to get one shipped from the UK.
Hi James.
The handling wasn’t so much changed as “transformed”. 75% or more of the body roll was instantly eliminated, and the vehicle handles far better when loaded (including the rack) than it used to empty.
I did have concerns that the vehicle might be more prone to oversteer, especially in the wet, but so far have been able to push the vehicle a little harder than before without even once suffering oversteer or skid. It still handles like a barge, being a 109, but is so much better than before that it’s almost inconceivable going back. The mod only cost me about £200 for all of the materials, including the custom made chassis brackets, the new steering rod ends and the entire second hand bar and links, and was worth every penny. The front will be stiffened up by uprating the front parabolic springs with a third leaf, and that should really sharpen up the handling by reducing the front end dive into the corners and when braking.
Without knowing the steel specifications and whether or not the bar is solid (it might be a thick walled tube, though I doubt that), dimensions would be useless to you, and coil sprung models’ bars would be stiffer than these as they suffer more roll than leaf sprung models, so their rates would not be of much help either. Sorry, but All I can do is show how I ftted it – I just don’t have access to the more technical specifications.
Nick.
Hi there. Excellent series of articles, well done. I am finding them very useful comparing them to my partial rebuild/restoration of a 109 2a ambulance.
May I just enquire? what manual shows the anti-roll bars in this piece of the article? I can’t find any reference to the bars in the official workshop manual for the 2a or in the parts book. I’ve also looked in the official series 3 repair manual and nothing there either. Are the details in a special military edition?
Look forward to your reply, thank you.
Take care.
Kevan
Thanks, Kevan.
The drawings were obtained from a member of an internet forum and are specific to the 109 Ambulance. They would not be in the standard Workshop Manual or Parts Catalogue, but should show up in the Optional parts Catalogue and Ambulance Workshop/User Manual.
Small numbers of 109 ambulances were made for civil users, but the vast majority were for the MoD. I really don’t know whether or not the civilian ambulances had this equipment, though I would assume they did, but it was standard on MoD ambulances. That may limit the diagrams to MoD manuals, but I’m sure someone like Dunsfold Land Rover or PA Blanchard would be able to help with more information, diagrams and complete manual pages.
Nick.
Thank you Nick. It has certainly got one of the guys at Britpart puzzled 🙂 I enquired with them about the possibility of getting some new polybushes for my ARB. Poor guy thought I was making it up or something. It does make sense that the ARB’s would be specific to the ambulances. I think I may be able to get some universal bushes from Superflex. I just need to make sure of my measurements.
Once again, great site, well done.
Take care.
Kevan
I’ll try to take some basic measurements this afternoon.
Wow, cheers Nick, much appreciated. I’m just in the throes of sprucing all of the component parts up on mine. It’s amazing what a new coat of paint does 🙂
Sorry about the wait, Kevan, but I have been flat out at work and studying a bit at home for for my six-monthly emergency sim-checks at work, as well as trying to get the Lightweight running and rebuilding the RRC’s brakes…
The anti-roll bar’s diameter is 20mm. The lateral section of the bar is straight and it starts to bend 25mm after passing clear of the outboard face of each chassis rail, the centreline of the bar being 75mm clear of the chassis rail at the point where the vertical links connect (ie. the bends are less than 90 degrees). The distance between the centre of the D-bushes (axis of bar) and the vertical link connection is 220mm. The vertical links are connected with track rod ends, so the bar needs to be flattened to allow the securing nuts to seat correctly and needs to be drilled in a tapered fashion with the same dimensions and angle as the holes in the steering relay/box drop arms or the swivel housings’ steering arms. I have no idea of what grade steel is used in such a bar, but any of the ARB manufacturers should be able to supply such information about their own products – I imagine that the grade would be an industry standard and that different thicknesses are used for different stiffnesses. Since you now have the diameter of the original part, you would be able to have a bar made up that would have similar qualities as the original. Since this is an optional piece of equipment and is not safety critical, exact matching is unimportant.
The vertical links between the axle and the ARB are 230mm long and are simply threaded tubes with a damper eye on one end and a standard steering rod end on the other. If you can’t get a complete genuine ambulance system, then I’m pretty sure that a track rod or drag link cut down to that length with the eyes from a scrap damper welded to the plain end would be quite sufficient. The genuine links don’t have slits in the threaded section and don’t use clamps to grip the steering rod end – the rods can’t turn in service lie an un-clamped steering rod could, but a track rod would be strong enough to serve the purpose as long as you used tha clamps – otherwise the rod won’t grip the rod ends’ threads well enough and the rod could splay along those splits and the rod end could potentially be pulled out of the correct position; you’d need to clamp the modified rod in the same was as when used on a steering system just to make sure the threads were kept tight against the rod ends’ threads.
The bottom plates under the springs are just standard front axle plates, so you can get those from any scrap Series LR.