The future of Hydrolastic suspension

General Chat with an emphasis on BMC Minis & Other iconic cars of the 1960's. Includes information on MK1 Action days.
Post Reply
User avatar
Peter Laidler
Posts: 5745
Joined: Sat Jul 15, 2017 5:35 pm
Location: Abingdon Oxfordshire

Re: The future of Hydrolastic suspension

Post by Peter Laidler »

EXACTLY Seamist...... the rubber casing acts as a shock absorber! See my para 2(d). Pulling teeth or what?
Seamist Green 1100
Posts: 45
Joined: Fri Dec 09, 2016 7:25 am

Re: The future of Hydrolastic suspension

Post by Seamist Green 1100 »

Peter Laidler wrote:EXACTLY Seamist...... the rubber casing acts as a shock absorber! See my para 2(d). Pulling teeth or what?
The rubber spring is a rubber spring.
It is not a rubber casing, it is not a damper, it is a spring. It is pre-loaded and holds energy.
It is the part that carries the load and deflects to absorb bumps.
abs
Posts: 190
Joined: Sun Jan 10, 2016 12:39 pm
Location: Cornwall

Re: The future of Hydrolastic suspension

Post by abs »

I am now confident I made the right decision when I converted to dry :0 :)

It will be easy to convert back using all the original parts I have stored when you good fellows finally sort the units out, meanwhile I can confidently take my car on a trip through europe knowing the hydro won`t let me down.

Keep up the good work chaps :)
User avatar
Peter Laidler
Posts: 5745
Joined: Sat Jul 15, 2017 5:35 pm
Location: Abingdon Oxfordshire

Re: The future of Hydrolastic suspension

Post by Peter Laidler »

Just make sure that your old displacers are well looked after, inside and out Abs. I would suggest filling the insides with a silicon based fluid, pump them up and down as best you can so that the fluid gets everywhere and either leave them like that, hoses upwards or just drain off the fluid and plug the hose with a bit of wood. I think that matter was discussed earlier sometime. Just my view of course ans always open to other ideas. Made from unobtanium and they ain't makin' no more.

I was going to write up a simple 5th form physics class experiment for you Seamist, on the basis that one pic describes 1000 words. Using two balloons (the displacers), a length of plastic pipe with a water filling facility (the interconnecting pipe) two 3" dia 6" lengths of plastic sewer pipe (the steel hydro outer casings) to house the balloons and two short lengths of broom handle (the struts) and a water tap but I don't think you've quite grasped the combined hydro and elastic principle fully. Another day perhaps
Dearg1275
Posts: 1497
Joined: Mon May 11, 2015 4:16 pm
Location: Scotland

Re: The future of Hydrolastic suspension

Post by Dearg1275 »

I have followed this thread with great interest and increasing understanding but can't help thinking that opinions are pulling in different directions, where as there is an element of enlightenment in what each of you is saying.

Let us take a displacer and see what we have on offer.

1. A lower chamber of variable volume containing an incompressible liquid.
2. Above this a valve that restricts the velocity of transfer to the other displacer
3. Topped off with an incompressible solid that is able to deform and recover.

Now consider the events taking place in this system when the suspension trumpet compresses it when encountering a raised road obstacle. These events are very rapid but do have a duration.

The pressure in the lower chamber is raised rapidly and fluid starts to discharge through the valve. The valve's lumen regulates the rate of discharge. As there is a raised pressure below the incompressible rubber "Spring" ( for such is it called in the workshop manual) and atmospheric pressure above it, it deforms upwards in proportion to the pressure below. As the pressure reduces in the chamber below the rubber spring recovers moving back towards its rest position.

It would seem to me that there are effectively two systems acting together much as you have with the dry suspension. The rubber spring is an active element but actuated via the incompressible liquid. The valving of the liquid not only allows the front to back ride height adjustment but also modifies the way the rubber Spring deformed. Rapid deformation to start with, but diminishing as fluid escapes the lower chamber and pressure reduces. The recovery of the rubber spring will drive it down into the lower chamber until the pressures in front and back displacers are equal. This suggests it has an active part to play in the transfer of fluid to the other displacer.

Clearly the dynamics of this are complex but the deformation of the rubber will be proportional to the pressure applied through the fluid element of the system.

Shoot me down if this is all a load of hogwash but that's how I read it.

D
User avatar
Glacier white
Posts: 72
Joined: Thu Oct 26, 2017 8:02 am

Re: The future of Hydrolastic suspension

Post by Glacier white »

I pretty much agree with Dearg1275.
You can see below the description of the system in the factory workshop manual, and a figure from a well known article in the Automobile engineer magazine in 1962 that presented the system to the public, from the late Alex Moulton himself.
You do not have the required permissions to view the files attached to this post.
User avatar
mk1
Site Admin
Posts: 19777
Joined: Thu Jun 24, 2010 11:30 am
Location: York-ish
Contact:

Re: The future of Hydrolastic suspension

Post by mk1 »

The paper written by Alex Moulton has been submitted to the MK1 site by Kelley Mascher, you can read a copy here.

http://mk1-performance-conversions.co.u ... _paper.pdf

I will be adding this to the technical section of the main site shortly.

M
User avatar
Glacier white
Posts: 72
Joined: Thu Oct 26, 2017 8:02 am

Re: The future of Hydrolastic suspension

Post by Glacier white »

This is excellent Mark, thank you very much!
It also contains the reply to many questions asked by Niles.
User avatar
Peter Laidler
Posts: 5745
Joined: Sat Jul 15, 2017 5:35 pm
Location: Abingdon Oxfordshire

Re: The future of Hydrolastic suspension

Post by Peter Laidler »

I take all of this on board and disagree with the mechanics and fuzzy logic of some of the opinions but we're missing the point....... It's not about what it is, or how it worked yesterday or what Sir Alex had for breakfast. What our efforts are aimed at is TOMORROW! The clue is in the title of the thread. The FUTURE of hydro suspension. That is, what we can do in the future with what we've got left today - 40 years after they stopped making the units. We're aiming at FIXING yesterdays stuff today for heavens sake. We can't fix a) popped/leaking rubbers/diaphragms because we ain't got no more. We can't fix b) rusted out casings because they're bonded to the rubber. We can't fix c) defective internal valves because we ain't got any. But I say we CAN fix c) if we look at using external valving. And restriction is just another word for valving.

Let's stick to The FUTURE of hydro suspension.. And one day there will be a repair. But you ain't going to do it by re-inventing the hydrolastic wheel - interesting though it might be! Just my take on things.
User avatar
winabbey
Posts: 601
Joined: Thu Apr 18, 2013 1:45 am
Location: Melbourne, Australia

Re: The future of Hydrolastic suspension

Post by winabbey »

Below is a description of the operation of the hydrolastic suspension used on a number of BMC vehicles, including some Mini models.

It appeared in a Shell Australia Technical Bulletin in mid-1970 and was authored by BLMC Australia's General Service Manager, Norm Prescott. I spent more than 30 years of my career with Shell Australia so have a fond liking for the publication.

Click on the image to enlarge it, and click again to enlarge further.
Shell Technical Bulletin Vol 7 No 10 May_June 1970 p6_7 low res.jpg
Shell Technical Bulletin Vol 7 No 10 May_June 1970 p8 low res.jpg
You do not have the required permissions to view the files attached to this post.
Post Reply