69k1100 wrote:I always envisioned it being stamped or spun on a mandrel. You can design it without undercuts, so both the upper and lower could be stamped.
It might have been made from readily available pipe originally, or perhaps they did this a means to better control wall thickness.
The shape of the upper / lower Housing isn't indicative of the whole manufacturing cycle.
There wouldn't have been any undercuts, the rubber then compression moulded directly into the steel cone, and then finally crimped on the lower valve assembly using a large hydraulic pipe press (with custom profiled dies), I think I even eluded to this in a previous post, you can see the witness marks form the hydraulic press. If you want to re-use the Rubber spring, then yes, you would have to flare the crimp. and then bash it back on?
Once you remove the crimp, cut/burn/dissolve the rubber and then recasting the rubber, wouldn't it be far easier to to punch/spin some new upper housings?
Any why not contact Dunlop? Perhaps they know the original formulation, Or maybe it was patented and so you would be able to do a patent search.
A couple of years ago I did try contacting 'Dunlop Systems' via email to ask if they had any historic information or old photographs in their company archives, showing the factory manufacturing process and tooling used in the production of the Dunlop/Moulton Hydrolastic suspension units as used on cars of the BMC /British Leyland /Austin Morris range of cars, especially the BMC Mini's from 1964-1970 and does any of the original tooling or engineering development material or engineering detail drawings survive or was everything scrapped?
Sadly as expected there was no reply......
"The Dunlop Pneumatic Tyre Company opened its first factory in the Hillfields area of Coventry in 1890. In 1908, following the acquisition of the neighbouring Stevenson Wheel Company, the Coventry factory was renamed the Dunlop Rim & Wheel Company Limited. The company relocated to the Holbrook Lane site in Coventry in 1919, where over the years it developed its engineering contribution to both the automotive and aviation industries. In 1959, collaboration between the British Motor Corporation, Moulton Developments and Dunlop saw the launch of the Mini motor car (ADO15). This was fitted with Dunlop manufactured cone spring suspension which, due to its success, quickly resulted in Dunlop forming a Suspensions Division in Coventry. The partnership continued with the launch of the BMC 1100 (ADO16) in 1962, followed by the 1800 (ADO17), both of which were fitted with Hydrolastic suspension manufactured by the Dunlop Suspension Division. With the change to Leyland cars in the 1970s came a further development, with the introduction of hydragas suspension on the Allegro, Princess, Metro, Ambassador and MGF vehicles. In 1970, The Suspension Division enlarged to include the further development and manufacture of the Pneuride® & Flexolink® air suspension systems, initially having levelling valves, to serve the commercial and public service vehicle market. With the introduction of Electronically Controlled Air Suspension (ECAS) in 1990 for Range Rover, the company extended the Pneuride range to include the sports utility market.
During 2007 Dunlop Systems and Components was formed as a management buyout of the Dunlop Coventry suspension division factory from previous owners Trelleborg AB. In the spring of 2014, the company moved to an all new, purpose built factory at Prologis Park in Coventry so ending a 95-year history at nearby Holbrook Lane."
Dunlop Systems and Components
Phone: 02476 889900
Does anyone know of any films, photos of the Hydrolastic Unit manufacturing process or factory machinery in the UK or elsewhere?
Does anyone perhaps know someone who worked in the original production process or what happened to the tooling....almost certainly scrapped.
There must have been some impressive machines and processes to produce millions of those unique suspension units in such a wide variety of shapes and sizes but sadly there seems to be very little record of it today.....I believe Heritage (BMH) have all the technical drawings, etc.