mk1-forum.net

A friendly international forum for people interested in the tuning & modification of classic BMC vehicles
It is currently Mon Dec 18, 2017 8:07 am

All times are UTC [ DST ]




Post new topic Reply to topic  [ 132 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6, 7, 8 ... 14  Next
Author Message
PostPosted: Fri Aug 11, 2017 7:31 pm 
Offline
User avatar

Joined: Sun Oct 07, 2012 8:28 pm
Posts: 115
Location: Lugano, Switzerland
Yesterday I recovered 4 units, it's mk3 cooper s, 21a2012, dated 1970.
The 2 rear units are badly reduced, I should try to clean them inside.

Image

Image

Image

Image


Top
 Profile  
 
PostPosted: Fri Aug 11, 2017 9:13 pm 
Offline
User avatar

Joined: Sat Jul 15, 2017 5:35 pm
Posts: 600
Location: Abingdon Oxfordshire
Lucky you! I would flush them out thoroughly until clean water runs out freely then dry them out until you need them or fill them with a silicon based fluid. I'd use silicon brake fluid as it's got all the non this that and the other properties you need to protect the rubber and the steel internal components. Plug the open hose ends with wood bungs or BSP blank-end fittings and store upright. Others might disagree of course but that's what the chemists suggest. As for the hose attachments then if they ain't broke - or leaking - why fix them? The hydraulic loadings they're subject too are nothing in the real world of industrial hydraulics. But if you do want to rep[ace it's an easy fix so long as it's not absolute authenticity you want


Top
 Profile  
 
PostPosted: Wed Aug 16, 2017 3:45 pm 
Offline

Joined: Thu Aug 03, 2017 9:15 pm
Posts: 26
Location: Eugene, Oregon USA
geroch:

Are all 4 displacers out of the same car, and are they all marked 21A2012? The literature I've seen shows 21A2012 front and 21A2014 rear. but I've only seen documentation up to the Mk2. Is it possible that Mk3 went to the same front and rear? If they are not marked with the number, 21A2012 has one silver band on the hose and 21A2014 has 2 silver bands.


Top
 Profile  
 
PostPosted: Wed Aug 16, 2017 3:54 pm 
Offline

Joined: Thu Jun 02, 2016 2:45 pm
Posts: 145
nileseh wrote:
geroch:

Are all 4 displacers out of the same car, and are they all marked 21A2012? The literature I've seen shows 21A2012 front and 21A2014 rear. but I've only seen documentation up to the Mk2. Is it possible that Mk3 went to the same front and rear? If they are not marked with the number, 21A2012 has one silver band on the hose and 21A2014 has 2 silver bands.


Niles, my displacer is on it's way...hope it works. I believe all Mk3 S's and early wet 1275GT's were all 2012 front 2014 rear. Early Mk2's were 1872/1874 and later Mk2's 2012/2014 but internally they are no different. I'm not yet convinced that front and rears differ in anything other than part no. but your work should decide this.
Tim


Top
 Profile  
 
PostPosted: Wed Aug 16, 2017 6:31 pm 
Offline
User avatar

Joined: Sat Jul 15, 2017 5:35 pm
Posts: 600
Location: Abingdon Oxfordshire
I'm pretty sure that in the next couple of years the remanufacture of, or attempts to fix the knackered internals of hydro displacers will flounder. It's not that I am a total defeatist but rather, a pragmatist and realist. Because it's not beyond the wit of man to design and develop a rubber cone suspension rubber bonded onto a x4-way bayonet fitting as per the current hydro units. Got me so far......? Then inbed or bond into the opposite end of the rubber cone a fitting the extends forwards (or downwards for the front susp.....) so you could use your current rods still sat into their cups while the rear (or top) of the new rubber cone is locked into the sub frame..

I wish I'd taken more notice during the production engineering phase at Uni!


Top
 Profile  
 
PostPosted: Wed Aug 16, 2017 7:17 pm 
Offline

Joined: Mon May 11, 2015 4:16 pm
Posts: 108
Location: Scotland
timell wrote:

I believe all Mk3 S's and early wet 1275GT's were all 2012 front 2014 rear. Early Mk2's were 1872/1874 and later Mk2's 2012/2014 but internally they are no different. I'm not yet convinced that front and rears differ in anything other than part no. but your work should decide this.
Tim


21A2010 was the part number for the front displacers on hydro 1275GTs. Also listed for uk police vehicles. The rear was the same as the mk3S. Whether harder or softer who knows?


Top
 Profile  
 
PostPosted: Thu Aug 17, 2017 3:52 am 
Offline

Joined: Thu Aug 03, 2017 9:15 pm
Posts: 26
Location: Eugene, Oregon USA
Hmmm.

The internals are the same for all the displacers I've opened. The differentiation seems to be the damping valve restriction. The dampening valve serves as the shock absorber in the unit. The spring rate is the same for all displacers (the rubber donut has the same part number on all) so the difference would appear to be a stiff shock or a softer shock. It makes sense to me, much like tuning shock absorber stiffness to the weight distribution of the car. I've not studied suspension systems, but I would expect a stiffer shock up front where all the weight is. Is that correct? 21A2010 is an interesting notion. We never saw the 1275GT here; was it a performance iteration? As used in a police vehicle I would expect a stiffer dampening.

I got the tracking number from timell; we'll see what that has to offer. If I can't get the original dampening data, perhaps I can just make up some dimensions to restrict the valve for a stiffer rate.

I thought we established a while ago that part number difference from early to later was a tooling issue, rather than a performance change. On the displacers I've opened there is a slight difference in the configuration of the stamped components. I think probably a tooling upgrade for manufacturing efficiency.

I'm not sure where Peter is going. I agree that any notion of a solution for the ages is probably not realistic. But I think we can get a few more years out of the inventory of 50 year old components. The rubber does not seem to have deteriorated as much as I would have expected, even in the displacers that have completely rotted interiors. The metal falls apart but the rubber bits clean up nicely and are quite supple for their age; considerably more supple than I at my age. I think Peter is suggesting that a solution is a unit with the form factor of the displacer with a rubber spring unit to be a drop in replacement. That would work, but that would be the "..lastic' portion losing the "hydro.." bit. We could also simply change to any of the many coil spring conversions available but what is the fun in that? I think this clamping ring will work, it has worked on the bench, I'll build it and find out if it stands up to the rigors of motoring. I'll work it as hard as I can short of "Italian Job" jumps. But it will be a while because I have to put the rest of the car together first.


Top
 Profile  
 
PostPosted: Thu Aug 17, 2017 10:19 am 
Offline
User avatar

Joined: Sat Jul 15, 2017 5:35 pm
Posts: 600
Location: Abingdon Oxfordshire
Nileseh, I thought that the hydro splitting and clamping idea was absolutely fantastic and a mechanical work of art. But, alas, financially beyond the scope of the average bloke with a knackered unit - or even someone like me with a reasonably sized engineering shop and facilities at his disposal. You're absolutely right about the direction I was thinking and you put it well....... A 'lastic unit....' without the 'hydra' part! A rubberised unit that would fit and lock into the space of the old HYDRAlastic unit AND use the existing sub frame, rods, cups etc etc.

You're right about the variations of hydro units. The rubber content mix was the same*. It was the valving/damping that differed between the units that made them different. And I often wonder whether the average road user or restorer would/could really tell the difference between them. Nope....., me neither!

*That's an easy test using simple lab facilities to undertake


Top
 Profile  
 
PostPosted: Thu Aug 17, 2017 9:05 pm 
Offline
User avatar

Joined: Sun Oct 07, 2012 8:28 pm
Posts: 115
Location: Lugano, Switzerland
This cooper s mk3 has all 4 factory-fitted 21A2012 units. I have the certainty of the 2 former owners. Even those I found on my cooper s mk2, 2 certainly are 21A2012, but I do not know if they are of the same car.


Top
 Profile  
 
PostPosted: Thu Aug 17, 2017 9:28 pm 
Offline
User avatar

Joined: Mon May 07, 2012 6:10 am
Posts: 2484
Location: Big Red, Australia
Don't take this as gospel, however, I seem to recall that the difference between the front & rear Hydro units (in sets) was only the internal damping between.

I think I have some info on this.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 132 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6, 7, 8 ... 14  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: nippycars, snoopy64 and 12 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group
Localized by Maël Soucaze © 2010 phpBB.fr