MGF Spring conversion

[Rob Bell]

Firstly, a disclaimer - I don't have anything to do with this particular project, but rather wished I did!

I am mentioning it here as it may be of interest to many as it is being proposed as an alternative to hydragas - particularly where a unit has failed, and the car is then under threat of being scrapped.

Developed by a couple of chaps named Clive Berry and Dan White, they've put together a coil conversion for the MGF, which is currently undergoing road testing in prototype form, but Clive reckons that they are on the verge of production.

I've not got much in the way of details at the moment, having first heard of it in relation to a planned show-case at Dreadnought garages and then Clive's subsequent posting on the MGF BBS. But how it is described, as a complete bolt-on conversion with spring units and dampers included, is a very exciting proposition. Spring and damper rates have been engineered to mimic the original equipment suspension so as to avoid any structural issues (i.e. those upper rear damper mounts!). As a bolt on system, it apparently requires no cutting, welding or modification - and this makes it rather attractive, and potentially cheap (even DIY-able) to fit as compared to attempted to retrofit TF suspension with its altered suspension geometry and suspension pick up points.

They are obviously pretty keen to gauge the level of interest in the product, in order to commit to production.

I am actually quite a big fan of hydragas - I've even had the opportunity to chat to the "Big Man", Alex Moulton, about it in the past, but I think that with the loss of production of Dunlop hydragas spheres, the long-term spares availability outlook is not great - although I am sure that folks like Malcolm Gammons will work hard to arrange limited production re-runs. But I don't anticipate bargain prices!

With that in mind, and also half an eye on motorsport applications, I am very interested in this conversion as both a long-term solution to MGF salvation from the scrap heap - both in preserving otherwise standard cars, and also in modified fast road/motorsport applications.

I'll try and find out more, but I post this here as a way of nudging these chaps forward and gauging interest within the whole MGF community.

[adrianclifford]

Rob, there was a Dover White hybrid 1.6i MGF (BU51HXK) for sale on E Bay late 2007 that had a factory fitted coil suspension set-up. I put pictures of it (along with it's TF nose) in FasTForward 8 page 5, I wonder where it is now ?

[Rob Bell]

I remember that too Adrian. A very interesting car - and having spoken to Al Phillips, I believe it was the designers intention to permit retro-fitting of TF suspension to the MGF. It's been done of course, but isn't that straightforward. I presume that this factory car left with TF suspension?

[Andrew Regens]

I for one would be very interested in a coil set up, just because it's getting harder to source rear spheres.

[adrianclifford]

I remember that too Adrian. A very interesting car - and having spoken to Al Phillips, I believe it was the designers intention to permit retro-fitting of TF suspension to the MGF. It's been done of course, but isn't that straightforward. I presume that this factory car left with TF suspension?

According to the sales blurb that came with the car, yes, it left the factory that way. It was also believed to be the first car to have the TF nose.

[colintf]

I think that car was up for sale again recently on Pistonheads?

[colintf]

......http://www.pistonheads.com/sales/1217971.htm

[Kasper]

Sounds interesting Rob,

I'm absolutely a fan of hydragas: it is doing well, it results in a smooth drive and finally it puts the MGF out of the main stream engineering mind set. So it must be said I prefer hydragas. But......we all know the story about the spheres.

Although I would do all I can to keep the original system on our F, I think it sounds like the only feasible way to convert without swapping the whole car.
Buying springs, dampers, new sub frames including various alterations ending up with a TF set up sounds like a long jump.

I do hope it will take a long while before I have to be a customer for such a conversion kit.

[adrianclifford]

Kasper, I have a friend of Fabio's who's F is stuck in a Rome garage with a rear hydragas sphere blown, Try getting a new unit for an F !!, Trophy ones are available but unfortunately standard F ones are not. I have had to get a second hand unit posted to him.

[Jimmie]

I am very interested in the prospect of fitting coil sprung suspension to my F.

I had began looking at the work required to fit TF suspension, but this may be a better solution that won't feature the TF's slight inherent understeer.

Eagerly await further details.

[MGFAUS]

This is not as difficult to do as you'd think. I converted my 1998 MG-F vvc to coil over shock springs two years ago. Initially I got hold of a kit from Taiwan which fitted like you'd expect anything from Taiwan to fit. The finished article looked more like a Landrover on high lift springs. This kit went back to Taiwan on my next trip however before doing so I took it down to my local sports suspension place and asked a simple question, can you make me something like this?
The result was that we now have coil overs using Bilstein Shocks fitted using the original shock absorber mounting points front and rear. The set up works well but you must remember to beef up the rear mounts as these are not strong enough. The front ones are ok though. Have now done around 12,000km on this set up and most of that running has been 50% in outback Australia and the other 50% in coastal country regions as I only use the F for holiday touring. I like the way the car handles although it does pitch front to rear a bit but I believe the TF is like this. Not a cheap thing to do but it keeps the car on the road, gives great handling and allows the suspension to be tuned and the ride height to be adjusted. Best of all I've said goodbye to the hydragas units which while not a bad system in theory the quality of the units was at best suspect and to my mind the BIGGEST drawback in this country is that if you lose a hydragas unit outside of the major cities it matters not if you've got a spare because no one outside of Sydney, Brisbane, Melbourne etc has got the ability to regas your system so no mater what your car is coming home on a truck. Not a cheap option when its nothing to be three thousand km from the nearest hydragas place like we were when we went to the Gulf of Carpentaria two years ago.

Murray Arundell
Brisbane Australia

[Rob Bell]

That's really interesting Murray - do you have pictures of the coil overs used?

I don't have a good feel for the failure rate in the UK of the rear spheres, but it can't be a coincidence that the majority of failures (curiously it always appears to the the right rear) occur in hotter countries such as Australia and the mediteranian countries of Europe.

Pitch, particularly in the longitudinal plane of the vehicle, is what Hydragas characteristically limits so well - and gives us MGF owners the fantastic ride we take for granted Conventional systems that have been well developed (cue the 85LE MGTF) contain this almost as well - but how much further ahead could hydragas have been had its development been continued?

[bgunn]

Austin Memories website

This is the site I mentioned yesterday about Hydragas development. A fascinating story about what can be achieved with Hydragas. If only this happened at the point the MGF was being conceived - rather than those few years later. For one, Kevlar diaphragms would probably be more durable over time than the reinforced rubber in the production units...

[Rob Bell]

I wish we could get these made!

[Rob Bell]

Minki-II Hydragas Development.

There now followed an intense amount of hydragas development, with the valuable assistance of Phil Turner, who was in charge of the chassis for MGF and MG TF, to prove whether the dynamics could be improved to current day standards.

Just like current Mini, hydragas had suffered from no real development for years, and was beginning to show its age. BMW had a poor perception of hydragas, mainly through their perception of Rover 100, which for them seemed biased towards ride rather than handling. As the interface to BMW on Chassis Concepts, it was my job to show whether hydragas could compare favorably with conventional spring / damper systems. This was done using measurements of ‘vertical dynamics’, ie measuring the stiffness and damping versus frequency for the complete vertical control system.

Alex Moulton organized many meetings at Dunlop, Coventry, where we all got together to discuss our findings, and decide on the next course of action. Dunlop measured the systems on their electro-hydraulic test rigs, BMW supplied samples of their current 3-series front suspension struts for comparison, we provided Rover 200 front struts, and through Alex we got new prototype hydragas parts made.

From these results we found that the BMW struts were not as good as they claimed, with much more frequency dependence of the out of phase damping component than they expected, whilst the hydragas units had insufficient low speed damping.


So from the technical data from the rig testing, a number of changes to the hydragas unit were made, which turned out to give dramatic improvements:-

1) Kevlar diaphragm. This gave a large increase in hydraulic bulk stiffness (ie, stopped it ‘ballooning’ under pressure) as well as a massive reduction in flexural stiffness (ie less hysteresis under suspension movement)

2) Disc type damper valve. This replaced the old fashioned petal valves, and resulted in better damper control

3) Damper pack decoupler. With the greater diaphragm effectiveness, and the better damper pack, there was now too much high frequency damping. A conventional system uses rubber mounts at the end of the damper to give some high frequency small amplitude isolation. There now needed to be a similar feature in the hydragas unit. This was achieved by internally mounting the damper pack via rubber ‘O’ rings, with a carefully controlled pre-load.

4) Larger bore front to rear interconnection pipes, to allow greater peak flow requirements, but with a blow-off valve, to control low frequency vehicle pitch.

5) As with Minki-I, a good large bore pipe was required from displacer to front gas egg, as this has to cope with full suspension flow requirements.

6) Adjustable gas sphere pressures, system pressures, damper pack shimming and displacer pushrod lengths all allowed ‘system tuning’.


Many permutations were tested, both on rig-test and on the Minki-II vehicle. By this stage, we had got to a good stage of vehicle development, and needed to make a more extensive appraisal of the vehicle.

With BMW’s assistance, we took Minki-II down to the BMW test track at Miramas, southern France, and then on to Munich. In Miramas, we inadvertently got caught up with Reitzle and his first line assessing all the new BMW products, as they do each year with a string of armed guards on motorbikes. Fortunately, they soon realized that we were ‘the mad Englishmen’, and waved us out of their way.

Next, it was up to Munich, skirting around Switzerland. Being able to cruise at 100mph on the autobahns, without using full throttle, and still being able to speak easily was a unique experience in a Mini, as was the surprised looks on the Porsche drivers!

We drove the Minki-II into the BMW engineering Fiz building, where it was kitted out with a radio communication system. Then off to the local BMW test track with the BMW chassis engineers, for some handling assessments and violent lane-change manoeuvres. Most of the BMW engineers admitted it was hard for them to assess such a vehicle, as they were so tuned into BMW brand values and sizes of vehicles, and ‘Mini-ness’ was something alien to them!

Next day, we went on the autobahns out towards the Czech border, and used some of the quiet local roads there to make assessments. However, all the German roads are so smooth and well maintained compared to UK roads, and generally built with constant radius bends. They were in for a shock with the UK roads!

Next stage was to assess Minki-II, and a number of other Minis, back in the UK. A number of the BMW engineers joined us for a trip to Wales. Here, the Minis were even more in their environment, with the roller-coaster roads twisting and winding all the way. The BMW chassis development engineer rather disparagingly dismissed them as ‘Mickey Mouse roads’, but then started to understand why the cars were as they were. (He subsequently brought his family across for a holiday in Wales, as did other BMW engineers!).

I think it’s fair to say that the general conclusion of all of this vehicle assessment work was that the Minki-II was a more ‘grown-up’ Mini, in every sense of the word. There was more space inside the car, the driving position was more accommodating and comfortable, the car had much better performance and refinement, the ride was much more accomplished, mainly because it had got rid of those sudden vertical jolts of the standard Mini. The car was able to steer and handle without drama at higher speeds than a standard Mini, and yet overall still having a very clear ‘immediacy of response’ that characterizes Mini driving.


Eventually a decision had to be made as to whether the new Mini was going to use hydragas or conventional suspension. The BMW chassis guys were appreciative of the developments we had made, but gently allowed us to come to the realization that the durability proving and productionisation of the new hydragas developments would take it beyond the timescale of the vehicle programme.

The Minki-II vehicle then earned a well-deserved rest, going on display in the Heritage Museum at Gaydon, and the hydragas developments we had made looked for a new potential application.

[bgunn]

Makes you think, doesn't it? There's so much development still in that system - it's naturally more accomplished than a coil/damper arrangement, yet due to perceived complexity has always suffered from politics along the way. Thanks to the tenacity of Alex Moulton, Alec Issigonis and the BMC>MG Rover engineers who took the concept further (the affectionately named 'Hydragassers') - we did get something rather unique for our cars..

[Rob Bell]

And I guess if we asked Alex Moulton to under take a development for our cars, the production numbers would be so small as to make it prohibitively expensive.

Still, might be worth asking him anyway???

[MGFAUS]

I've got no photos here at the moment, but the car will be up on the hoist tomorrow as its being prepared for a trip to Perth and back (around 9000km or so) so will slip across to the workshop and take some and post them here. Will also see if I can get a shot of the upper rear mounting point strengthening bracket. Its very important that these are used as we found that the existing mounting point is not strong enough and could fail. The front ones however appear to be fine.

BTW on a completely different topic has anyone experienced a vibration from the rear of the car when accelerating in top gear? I have had this for some time and suspect that the CV joints are the culprits. It usually happens at the 100kph mark, yet if I accelerate hard in third and take the motor all the way to the red-line its a smooth as silk......

Regards,

Murray Arundell
Brisbane Australia

[Reckless Rat]

try having the rear wheels balanced. I had the same problem & it sorted it.

[Rob Bell]

Look forward to the pictures, and hope that a wheel balance sorts the vibration problem