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PostPosted: Sat Sep 02, 2017 11:03 am 
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Location: Abingdon Oxfordshire
Nines, you are a total genius par excellence........... I just wish you were one of my tutors at Uni while I was struggling to get the hang of fluid transmission, valves and Boyles law* as it sort-of related to all this hydro and air pressure stuff............... I still don't understand the fluid part of hydrolastic - but I will do after your lessons. The mechanicals are simple - that why mechanical engineers are simpletons (that's what the Chemical Engineers call us!)!
*fluid transmission, it's not Boyles law but the principles are similar!

Niles....., why don't you write up a sort of uni thesis/dissertation about this subject. To be honest, you've made the HYDRO part of this thread so easy-readable in much the same way as Spider has made the LASTIC part of it the same


Last edited by Peter Laidler on Sat Sep 02, 2017 3:10 pm, edited 2 times in total.

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PostPosted: Sat Sep 02, 2017 11:40 am 
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nileseh wrote:
I'm not sure of the reason for the bypass, perhaps simply to let the fluid move unimpeded for small motions.



would it not be to help any air find its way up through the displacer and out the pipe when first filling them maybe?

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PostPosted: Sat Sep 02, 2017 5:24 pm 
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rich@minispares.com wrote:
nileseh wrote:
I'm not sure of the reason for the bypass, perhaps simply to let the fluid move unimpeded for small motions.



would it not be to help any air find its way up through the displacer and out the pipe when first filling them maybe?


Perhaps, but that would not explain the diameter difference. Also the hydrolastic service machine is intended to evacuate the system prior to filling it with fluid. The book says pull at least 27 inHg which is about 13.3 psi vacuum. 14.7 psi is full vacuum at sea level so that's pretty much all the air.

(I always think it's odd to speak of vacuum in terms of pounds per square inch. 14.7 psi is atmospheric pressure at sea level, so if all the air is out of a sealed vessel, there will be 14.7 psi force applied over its outer surface)


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PostPosted: Sun Sep 03, 2017 12:35 pm 
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NIles and Spider........ On the subject of valves and valving, in practice, anything that restricts the free flow of fluid during normal transmission (of the fluid) is a valve so on that basis, at it's simplest, if the valve mechanism inside a hydro unit has failed totally* you COULD easily have an external valve (and a restrictor is a valve by definition don't forget) in the fluid line. It was said, and I don't know how true it is/was, that comps cars had a specially made 'valve' in the form of a secondary restrictor in each of the specially made ADAPTOR, 21A-1524, This is the hex nut on the front bulkhead that allows the F to R hydro pipes to attach to the hydro unit hose and attach to the bulkhead. So, thinking on my feet and back to my physics teacher days this two way valve - equal both ways of course - is what is needed

*If the internal valve is rusted solid or has jammed in anything but the totally OPEN position, there could be a problem. But whether this internal valve is open/partially-open/closed can easily be established by timing the total evacuation of a filled dodgy unit against a known serviceable unit.

The idea of an external valve/restrictor SEEMS to be the perfect solution to Niles methodology. That of machining open the hydro units and ring clamping together. If the valve and diaphragms are OK....., all well and good, If the valve is knackered, just scrap the valve part and return the re-assembled unit(s) with a new modified ADAPTOR 21A 1524. And while we're there, incorporate a secondary (or main) evacuate/refill valve on the adaptor too!

It's a rainy Sunday morning and I'm deep in thought about this. And thinking that if I were a zillionaire, I'd get all those technically interested parties together at Niles workshop for a week. We'd have this cracked in a few days and the rest of the time we could all have a holiday!


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PostPosted: Sun Sep 03, 2017 1:11 pm 
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Peter - only a week? Oh for god's sake man, it would take us more than a week to get through a few boxes of beer,,,,,,,, :D

Niles - I tend to think in absolute pressures, where a 'vacuum' of 30 inches is 0 PSI and Air is at 14.7 PSI, so in the case of the Hydro Service Unit, when the system is evacuated, it's at 1.5 PSI absolute - give or take.

Peter, the restrictor you mention was most like used. I'm not aware of them, however, I am aware that the Comps Dept did get up to a few hidden things, to get around some of the various comp rules so quite likely borne from that.

In regards to your suggestion of external valving, that's something similar to what I tried a few years back. I fitted a T piece at the font displacer. On each side of that, non-return valves in opposing directions, so that flow in would go via one and the reverse flow would go out the other. On to these, I fitted Needle Valves, which are a 'throttable' valve, these were then plumped back together via a Tee and connected to the Pipe running to the rear. It was a little bulky.

With the Needle Valves, I was then able to adjust the Bump characteristics for the fronts, which was the rebound on the Rears, and independently adjust the rebound for the Front, (which was the Bump on the Rear). It was an experiment initially to restore the lost damping but then to play around with the tuning of the system. Interesting exercise, but as the front and rear were interconnected, it was difficult to arrive at that 'sweet spot'. Now I better see where the original damping restrictors are in the system, external valving, while will work, won't quite work the same and this was what I found. Not rubbish by any means, just different.

I'd suggest though, that a simple 'one size fits all' restrictor fitting, as you've suggested would be a very practical option here and it would all look 'right'.


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PostPosted: Sun Sep 03, 2017 6:26 pm 
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Ok then Spider, if Niles agrees we'll make it two weeks. In that time we'll have cracked the hydrolastic - less the hydro part conversion PLUS have the wet to dry (and vice-verca) swinging arm nonsense sorted out too Plus time for a few tinnies and....... and.......


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PostPosted: Sun Sep 03, 2017 8:38 pm 
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Looking at these photos of the unique modified Moulton Moke (auctioned in 2013) which was used for Hydrolastic suspension research by Alex Moulton has anyone any ideas as to what mods he was trying out?

"This Moke was one of the first produced (at Longbridge, where all UK Mokes were built) following the model's introduction in August 1964. The first owner was Morris Motors Limited of Cowley, Oxford. On 23rd August 1965 the vehicle was transferred to The Austin Motor Co Ltd, Longbridge, Birmingham. At the suggestion of Alec Issigonis, Alex Moulton (through Moulton Developments Ltd) acquired the Moke from BMC in January 1966 for the purposes of suspension research, and it was delivered to Bradford-on-Avon where work immediately commenced to fit Hydrolastic suspension. Subsequently it was used for several years as a test-bed for further Hydrolastic system development.
This is an extremely rare UK-specification Mini Moke dating from the first few weeks of production. The fitting of Hydrolastic suspension by the system's inventor makes this vehicle unique and, although it will require some restoration and re-commissioning, it is a very important piece of the historical jigsaw relating to BMC/BL/Rover Group's widespread use of Moulton's suspension systems."
https://www.bonhams.com/auctions/21274/lot/349/

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PostPosted: Sun Sep 03, 2017 8:54 pm 
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We had permanent external resisters in the ADO16 grass track racer back in the day............Smack pipe with hammer and close it up a bit....................


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PostPosted: Sun Sep 03, 2017 9:25 pm 
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I worked with Moultons Chief (?) Engineer, Joe Xxxxxxx at Warminster. I also found myself the owner of one of his early 60's Moulton bike. Seems that he was a bit of a one-trick-pony in that everything he did was opposite to the engineering rule of thumb - K.I.S.S.. Like Hydro suspension......, just try getting spare parts for one of his bikes! I could be wrong of course


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PostPosted: Mon Sep 04, 2017 10:22 am 
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my dad has a Moulton bike, one of the normal ones, not the really fancy ones

he discovered the flaw with the small wheels is that when you are 'giving it some' down a hill the front wheel starts to 'flap' as it goes faster and faster - in the end it will spit you off, as my old man found out.

he has never ridden it since :lol:

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