Deserting Doctor Moulton
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Author:  mab01uk [ Fri Aug 11, 2017 9:13 pm ]
Post subject:  Deserting Doctor Moulton

AROnline Blog : Deserting Doctor Moulton
"At AROnline, it’s no secret that we are fans of the late Dr Alex Moulton’s suspension systems, whether it be the Hydrolastic installation on the BMC ADO16 1100/1300 series or the later Hydragas system used on the R6 Rover Metro of the 1990s.
However perhaps the least successful use of Dr Moulton’s suspension systems was on the original Mini. According to all the histories, Hydrolastic suspension was intended for the original ADO15, but because of the tight schedule stipulated by BMC chairman Sir Leonard Lord, a system of rubber cones was substituted instead. It did give the Mini the cachet of having independent suspension at a time when such a thing was a novelty confined to upmarket cars, but it was far from satisfactory.
The rubber cones made by Dunlop gave a bumpy ride over uneven surfaces, but also endowed the Mini with excellent roadholding so beloved of the teenage boy racers that had their first motoring experiences in the BMC baby. Hydrolastic made its debut in the Morris 1100 of August 1962 and it impressed all and sundry. It eventually appeared as standard on the Mini in October 1964 with a £20 price increase. Did it work on the Mini?"
More Here:- ... r-moulton/

Author:  mk1 [ Sat Aug 12, 2017 9:18 am ]
Post subject:  Re: Deserting Doctor Moulton

I have driven a few minis fitted with steel springs & none of them have been anywhere near as good as a Mini fitted with a decent set of rubber doughnuts.

Author:  Peter Laidler [ Sat Aug 12, 2017 10:02 am ]
Post subject:  Re: Deserting Doctor Moulton

I'd thought of springs when one of my new 7000miles ago hydro units started to slowly leak. Anyone else got any comments - good or bad? The weep is so small, about 3/4" per year so I just pump it up each spring after the winter hibernation. But liquid leaks NEVER improve with age!

Author:  Costafortune [ Sun Aug 13, 2017 11:48 am ]
Post subject:  Re: Deserting Doctor Moulton

A low mileage Hydrolastic Mini can be very good, more so with front dampers fitted.

Ultimately, Hydro and rubber cones were a dead end. By the early/mid seventies there were cars with steel suspension that had both superb handling and a very good ride, outclassing rubbish like the Allegro.

The Alfasud, VW Golf and Renault 5 are just three.

Author:  mk1 [ Mon Aug 14, 2017 9:09 am ]
Post subject:  Re: Deserting Doctor Moulton

As I understand it the problem with steel springs on a Mini is the space available. Springs can be neither progressive or as compliant as would be ideal.

Author:  Costafortune [ Tue Aug 15, 2017 5:59 pm ]
Post subject:  Re: Deserting Doctor Moulton

A Mini doesn't need steel springs though; I've never found the ride on cones to be that bad.

Author:  Peter Laidler [ Tue Aug 15, 2017 6:50 pm ]
Post subject:  Re: Deserting Doctor Moulton

It's not the actual RIDE on rubber cones that's bad, it's the sheer thought of the cost of converting to them that's bad. Sort of nightmare bad.

With modern spring manufacturing and especially the spring material technology had come on in absolute leaps and bounds since the 90's. I'm sure that there's a much simpler way of using springs and shock absorbers within the space occupied by the hydro or cones. I regularly use an industrial spring maker and while he doesn't know the mini well enough to offer an expert opinion he did say that helper springs would be an absolute doddle - after set-up costs!

Author:  Alex [ Thu Aug 17, 2017 8:01 am ]
Post subject:  Re: Deserting Doctor Moulton

I've been running red S-Racer coils on Betty for about seven years. The ride is certainly more compliant and smoother than normal, but possibly not quite up to Hydro standards. Handling is different, as the springs are linear instead of rising rate like rubber, and more akin to Hydro. Once the initial body roll is done, the grip is just as good as rubber. I'm running std KYB dampers as I want a nice ride, but a set of harder dampers and an anti-roll bar would improve the handling by removing the roll.
On the downside, you can't load the boot up and two people in the back will see tyres rubbing arches - and I run a high rideheight. The linear springing just isn't compatible with carrying weight in the back unless you really preload the spring with the Hi-Lo.

One of the front springs broke two days ago on the way to work, no idea why at this stage, but they have all lived a very hard life. I changed it for a cone yesterday (and had half-forgotten that the top arm has to come out as I've not had to do that in years) while awaiting a new one to arrive. Yes, I like them enough to leave them in and Mark is welcome to drive the car any time to verify the ride quality.

Author:  Spider [ Thu Aug 17, 2017 10:06 am ]
Post subject:  Re: Deserting Doctor Moulton

mk1 wrote:
As I understand it the problem with steel springs on a Mini is the space available. Springs can be neither progressive or as compliant as would be ideal.

A while back, long before steel springs were available for Minis, I spent around 3 months with a Spring Manufacturer's R&D Engineer looking at how we could do steel springs to replace the rubber cones. We started off trying to replicate the variable rate that the rubber and trumpet combination gives, then when it was quite apparent that couldn't be done (even trying it with two springs, one inside the other and 'bee-hive' shaped), we then tried to do a spring in a linear rate that had an appropriate rate and would fit inside the front subframe. At the end of the 3 months, Michael (the engineer) asked me "ever thought of using rubber?"

The bottom line is it cannot be done.

To get the rate where it needs to be, the wire size had to go up, but then with the space available, you can't get the travel needed. To get the travel needed, the wire size has to go down, but the rate falls well short.

The Mini has very high leverage ratios (4.5:1 in the front and 5:1 in the rear) from spring seat (knuckle joint) to Ball Joint. Have a look at all other cars that use coil springs, typically this ratio is around 1:1 to maybe as high as 1.2:1. This allows them to use a lighter rate spring, lower the wire size to get them to fit and work the way they do. Without totally re-engineering the subframes and suspension arms in a Mini, this is just never going to happen.

On the front of a Mini, the rubber cone has 9 mm preload and travels a further 32 mm (if your bump stops are good!!), so all up, with the rate of these, a minimum of 41 mm travel of the cone is needed. If springs are to take the place of these, then a further 3 mm per coil of the spring s needed to be sure not to get coil bind (and break as Alex's have ^), typically for most around, they have 2 coils, so an 6 mm is needed, or 47 mm spring travel.

More recently, I did some tests on some springs that are commercially available



It's quite clear that these springs don't come close to the job.

Fitting these, can expect results like this


Author:  Peter Laidler [ Thu Aug 17, 2017 10:26 am ]
Post subject:  Re: Deserting Doctor Moulton

Great, well written, non too technical, jargon free, easily understood and straight to the point. It amply describes the fact that while you COULD use them, mechanically springs are not the way to go. If I'd had you as one of my teachers while I was an apprentice I'd have found Uni a LOT simpler!

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