Identifying Hydro Units

[Pete]

In that case, surely if you put a 1/16" restrictor anywhere in line in the system you will have hydro units that behave line S ones.

M

That and the thicker rubber spring (hence shallow top?) . It still looks to me like there was no such thing as an S displacer until those later colour banded units (except green band and single orange?)

[Austin Costin]

But if the rubber units have the same part no maybe its down to its position, not thickness.

[Jack of all trades]

The restrict or in the line wouldn't work as then it would restrict both ways, the valve in the displacers renders the bleed hole useless once opened. The thing to do back in the day for race cars was put valves in the interconnect lines. Put two guys in the boot, pump to the max close the Alves and pump again to the max. That's how they ended up with rock hard suspension and on the out lap the driver would open the valves so the scrutineer would find a stiff but working suspension system. Got this right from the horses mouth and he wasn't bothered with what type of displacers was used at all, as long as it was up to the job!

[Spider]

That's right Paul though just to confuse matters some of the units also had that part number, which was stamped into the casing.

The Part nos. Stamped on the steel part of the casings were never the same nor related to that moulded in to the rubber.

I wonder also if Australian cars were sent the package of up rated units as standard as the landscape was harsher, maybe a standard unit was in fact the same as a UK cooper S?

Sadly, no.

<EDIT: Here's the UK list of at what cars they changed over from early to late, but in particular, what the factory says about interchanging early and late parts;-



>

<2nd EDIT: Here's the Aust Car No Change Over points and the types of displacer's fitted;-



>

<3rd EDIT:- Here's a Blue banded Cooper S Bag, not that the rubber is set down lower from the top, like the Deluxe and other 'ordinary' Bags;-



I have another - later - Cooper S Hydro Bag in the workshop on which the Rubber is set closer to the top.

As I mentioned earlier, the difference as far as how far down the rubber is place from the top of the bag, seems to relate to early vs late Hydro Bags.

In Pete's opening post, there is a photo of a late (MKIII) Cooper S Bag which is set closer to the Top >

[Pete]

So it looks like coloured bands and stamped part numbers look to be the only quick way to tell an uprated unit which were fitted to Ss from around early '66 and a pre '66 S units (ie fitted as standard at the factory) didn't actually exist.

Re the stamped part number being different to the 21A1477 moulded into the rubber, the exception is seen if you look at the second photo in my initial post you can see 21A1477 stamped into the side of the casing. Dated '66.

[Nevsmini]

If any help here is a photo of my blue bands for my 67 Radford HB

[Tim Harber]

Really enjoying this thread as I have spent many interesting hours playing with these units.

We have re-hosed about 200 units now but I still don't have all the answers , especially about the difference between standard and S . I got as far as getting Alex Moultons phone number to ask him about it but was sadly too late. We did supply him (through his nephew) some units some years back

Don't have enough time to elaborate at present

In the mean while , a pic of a standard one I cut in half years ago as I could never get my head around the more techy illustrations. Cut an S one in half at the weekend

Will report back at some stage

[Spider]

One thing I must say about the Hydrolastic System - it was extraordinarily well engineered and manufactured. OK, that was two things.

That it was last fitted to Minis back in 1971 in the UK and at the end of 1972 here in Aust and that these units are still on the road and working so well today is amazing for a car that was at the lowest end of the market (in terms of price).

I have a 10 page article "as told" by Alex Moulton (and printed in September 1962) on the design and development of this scheme. I'll get that up here soon.

Trivia question;- When was the first prototype Hydrolastic system fitted and trialled on a car?

[Rubber Sprung]

I think hydrolastic was first tested on a Alvis TA350 in about 1954 .

[Austin Costin]

Great picture Tim, looking forward to seeing the S one sectioned.

[Tim Harber]

Just quickly before I pack up and go and play at Brands

Aussies have it easy . Our climate does for most units

Top:



Bottom: (we mended this)



We have gradually improved what we can do and also been playing with an Aeroquip type hose that will fit inside the old hose but will restrict the flow as its smaller bore. Need to have a spare hydro car handy that we can test it on....

[Pete]

So as yet no evidence of the mythical early "Cooper S " displacer, I still suspect that those displacers fitted pretty much across the range in the parts lists were all the same spec whether fitted to Coopers Ss, Elf or others .A displacer sold on EBay yesterday described as Cooper S' for £200 but was a 21A1477 ;stamped into the casing ) fitted to all sorts so there seems to be a fair bit of confusion out there.

[mk1]

I am staggered that there hasn't been more definitive comment on this subject. I can only assume that there is one of two possible conclusions to draw.

1) No one knows if early (64 - 66) Hydro units fitted to Cooper S's were the same as Standard ones.

or

2) Those folks who do know are keeping quiet, because they don't want everyone to know this is the case.

If anyone who knows anything can shed any more light on this subject, I for one would be very interested to read what you have to contribute.


Mark F

[cooper1969]

Hello all,
my first post here and I have been following this very interesting post.
Reading the mini and cooper special tuning booklet it states that the early (red band) c-21a 1819 is a hard competition unit, which leads me to believe that standard fitment for the early cooper `s` to be the stiff yellow band c- 21a1705, it also states "only the cooper `s` is fitted with these hard units as standard" which doe`s suggest the normal rated 21a 1477 (Front ) and 21a1703 (rear) early displacers were never fitted to the `s` models. I did try to upload a scan of the said page but it said file to big ,I hope this may be of some help. John

[abri]

Surely there must be some people who have stripped down unmolested S'es and taken note of the part numbers stamped into them.

I have one restored CKD (in South Africa) '67 S that has orange band displacers on it...whether these came from the factory I can't say for sure. I have been told by someone who worked at BMC/Leyland here at Blackheath that they used standard displacers on the S but fitted a little reducer in the pipe to make it stiffer. My other car, same age, has unmolested suspension but I've never had it apart and can't see any coloured paint or part numbers on its displacers.

[cooper1969]

I have one restored CKD (in South Africa) '67 S that has orange band displacers on it

2 orange band displacers (21A1811) are listed as late stiff units, which I think sounds possible for a 67`s`

[Austin Costin]

OK, so no one really knows.

SO do we know the difference's between the banded units, as in what makes them different from one another ?

One would guess that it would be a orifice/valve difference, does anyone know for sure ?

Tim Harbour is going to have a saw arm by the time this thread is over

[Spider]

OK, so no one really knows.

Ah, dttttttt,,,, hold on there,,,,,,,,

there's only 24 hours in a day,,,,,,,,,

[InimiaD]

Further to this topic on S bags I managed to find some stamped numbers on all 4 of my S ??? units.
I've had a look in the tech section on the home page to try and decipher all the numbers.
The stamped numbers / letters are poorly done, but the last 3 "marks" look to be D68 on 2 units and D70 on the other 2.
Did they date stamp the units or are these in house codes for valve sizes.?

I had to use a magnifying glass to read the numbers, but there appear to be gaps between numbers where the A should / could have been.

[Nevsmini]

Yes they are date stamped as well. Mine were stamped 67 at the end and the car is a 67.