rcreweread Posted February 22, 2020 Report Share Posted February 22, 2020 Hi all - my understanding is that Stevsons standard rebuild spec is now to a 15% uprate but obviously you can specify higher. In the past Derek Stevson explained to me that they were the only company with access to the genuine OE main seals from Armstrong ( don't ask me howcome or why because I don't know) and that they find a large number of units with knackered bits inside ie cranks??etc, so often it isn't just a case of changing oil and O rings. He also explained that the current cork seals for the top casing cover are quite thick and "give" over time after they have been initially assembled, and this causes leaks which are easily eliminated by retightening the 6 screws which hold the top cover on - not ideal I know but worth knowing before condemning a leaky unit outright - no association with them other than as a customer Cheers Rich Quote Link to post Share on other sites
super6al Posted February 23, 2020 Report Share Posted February 23, 2020 Out of interest, has anyone on here totally dismantled a unit? I would like to see what seals (other than the valve O rings) are inside. I couldn't see anything on the pistons & judging by the metallic suspension in the oil I guessed they are a tolerance fit but there must be something for the shaft. The drawings I've seen aren't very clear on this. Regarding the cork gasket I carefully peeled the top off with a thin blade & resealed using original gasket & thin layer of Hylomar. Quote Link to post Share on other sites
DanTR6 Posted February 23, 2020 Author Report Share Posted February 23, 2020 1 hour ago, super6al said: Out of interest, has anyone on here totally dismantled a unit? I would like to see what seals (other than the valve O rings) are inside. I couldn't see anything on the pistons & judging by the metallic suspension in the oil I guessed they are a tolerance fit but there must be something for the shaft. The drawings I've seen aren't very clear on this. Regarding the cork gasket I carefully peeled the top off with a thin blade & resealed using original gasket & thin layer of Hylomar. One of the links further up shows the main shaft pressed out, one of the descriptions says they use a Dowty washer to stop leaks which sounds like a very good idea https://en.m.wikipedia.org/wiki/Bonded_seal Quote Link to post Share on other sites
astontr6 Posted February 23, 2020 Report Share Posted February 23, 2020 11 hours ago, rcreweread said: Hi all - my understanding is that Stevsons standard rebuild spec is now to a 15% uprate but obviously you can specify higher. In the past Derek Stevson explained to me that they were the only company with access to the genuine OE main seals from Armstrong ( don't ask me howcome or why because I don't know) and that they find a large number of units with knackered bits inside ie cranks??etc, so often it isn't just a case of changing oil and O rings. He also explained that the current cork seals for the top casing cover are quite thick and "give" over time after they have been initially assembled, and this causes leaks which are easily eliminated by retightening the 6 screws which hold the top cover on - not ideal I know but worth knowing before condemning a leaky unit outright - no association with them other than as a customer Cheers Rich Hi Rich, A bit of a correction here! The original top gasket was made by Coopers Mechanical Joints Ltd using a special paper based Oil Resistant Armstrong material using steel tooling i.e. punch and die system, to cut out the gasket. The material was not cork? Armstrong manufactured a whole range of gasket materials as well as flooring materials. Companies like Caterpillar, International Harvester all used Armstrong gasket materials and Coopers made their gaskets, here in the UK. I know this as they were accounts of mine. Cork in my view would not be the correct material to use because of torque loss on the screws? Bruce. Quote Link to post Share on other sites
super6al Posted February 23, 2020 Report Share Posted February 23, 2020 Hi Dan I should have read the links first! The Gerards garage link is where I read about the oil lubrication the shaft. The other link is interesting, at least it confirms my thinking about the piston seals (or lack of) & shaft seal. As I said when I flushed the arms out there were fine metallic particles suspended in the oil, obviously this indicates wear. To what extent this affects the damping I can't say as I haven't got a new one to compare against. I did a crude check after reassembly by attaching a weight to each damper arm & timing how long it took to travel its arc in both directions. At least both dampers R/L were in the same ballpark & the car drives fine. I've a feeling 20wt fork oil might be slight heavier than what was originally in there so this could compensate for wear. The gasket material as Bruce states is more like compressed paper than cork & if your careful can be reused. Alan Quote Link to post Share on other sites
DanTR6 Posted February 23, 2020 Author Report Share Posted February 23, 2020 so does anyone know where you can buy the main shaft seals and rear cover plate? the guide shows drilling it out, dont want to do that if I cant find any replacements anywhere. Will try and save the gaskets but the seals look to be shot. Quote Link to post Share on other sites
rcreweread Posted February 24, 2020 Report Share Posted February 24, 2020 22 hours ago, astontr6 said: Hi Rich, A bit of a correction here! The original top gasket was made by Coopers Mechanical Joints Ltd using a special paper based Oil Resistant Armstrong material using steel tooling i.e. punch and die system, to cut out the gasket. The material was not cork? Armstrong manufactured a whole range of gasket materials as well as flooring materials. Companies like Caterpillar, International Harvester all used Armstrong gasket materials and Coopers made their gaskets, here in the UK. I know this as they were accounts of mine. Cork in my view would not be the correct material to use because of torque loss on the screws? Bruce. Bruce - I was referring to the current seals which Stevsons are using at the moment which appear to be of a cork type material - certainly I found a number of reconditioned units I had done showing signs of seepage around the cover, and was able to tighten the screws quite a lot which has cured the problem. Dan(?) - you could try Stevsons for the seals - I'm sure they used to sell them separately from their stand at various shows - here's a link if you haven't already got one: http://www.stevsonmotors.co.uk/Stevson Motors - Homepage.html Hope this helps cheers Rich Quote Link to post Share on other sites
DanTR6 Posted February 24, 2020 Author Report Share Posted February 24, 2020 interesting chat with Stevsons this morning. The 15% uprate is via shims on the spring, and he said what ever i do, do not use fork oil as its too thin. They use a 624 oil which he can supply along with the seals. The gasket is cork so I will see how easily I can get my old ones off. Quote Link to post Share on other sites
ed_h Posted February 24, 2020 Report Share Posted February 24, 2020 (edited) "Fork" oil isn't very specific, and it comes in a range of viscosities. Its probably better to refer to it as hydraulic oil. There are (at least on mine) two springs in the valve assembly. "Jounce" stiffness is set by shims under the large copper colored spring, while "rebound" stiffness is changed by adjusting the nut that captures the smaller spring. Cork gaskets are easy to make. The material is easily available. Ed Edited February 24, 2020 by ed_h Quote Link to post Share on other sites
super6al Posted February 24, 2020 Report Share Posted February 24, 2020 These are mine just after they were cleaned. The one on the left (RHS of the car) I believe is original. It has a grey gasket material. The other has been replaced at some point along with the TA. Using a modern oil resistant paper gasket would negate the need to re tighten cork gaskets. I bow to Stevson expertise but the advice about not using fork oil seems a bit vague as it depends on what type & viscosity of fork (or any other oil for that matter) is used. Fork (suspension) oils can range from near water viscosity upwards. The link to Stevson damper section from the home page doesn't seem to work, the only 624 oil I can find is a Mobil gear & bearing oil? This will work in the LA but actually has a lower viscosity than SAE20 fork oil, nearer SAE10, however adjusting the spring valve will compensate for this. I learned a couple of things today (too much snow & idle time!) one is SAE cannot be strictly used when selecting fork oil viscosity. For example I used Silkolene SF20wt but Silkolene RSF15wt is actually thicker! Also what is equally important as viscosity is the VI (Viscosity Index) which is a measure of the temperature range oil will keep its viscosity. The higher the VI figure the longer oil will maintain its viscosity at a higher working temperature. Using Silkolene as an example RSF15wt has a higher viscosity & a higher VI than SF20wt (& also the Mobil oil). I'm not sure what temperature our LA will get up to as they work but VI will be a factor if they get hot. For example a motorcycle rear shock will work much harder than its fronts so will require a higher VI than the front forks. I would be interested to hear what make the 624 oil is to compare. Alan Quote Link to post Share on other sites
super6al Posted February 24, 2020 Report Share Posted February 24, 2020 Sorry for any duplication - I was compiling my reply & Ed beat me too it about the viscosity comment. Quote Link to post Share on other sites
DanTR6 Posted February 28, 2020 Author Report Share Posted February 28, 2020 So i have my kit of bits from Stevensons and he has been very helpful on the phone, but I have two different bodies and 2 different types of valve, one being the later valve with no upper o-ring. My issue on the leaking damper is that there was no bottom o-ring on the valve and the body is flat like the picture attached. It just had a washer behind the nut. Anyone have any idea if this version is meant to have a rear washer on the valve as the rear washer provided is too big and just makes the nut sit proud and will affect the damping. It wasn't leaking from the bottom valve but from the main seal, once I got the new seals I could see why, the correct seals have several lips like a normal oil seal and the one in there was just a plane rubber seal with no lips at all so probably wasn't doing a good job of sealing anything. Quote Link to post Share on other sites
DanTR6 Posted February 28, 2020 Author Report Share Posted February 28, 2020 Picture of it tightened up with o-ring on, doesn't look right to me Quote Link to post Share on other sites
Waldi Posted February 28, 2020 Report Share Posted February 28, 2020 An O-ring should sit in a pocket (chamber?). If not, you cannot tighten the bolt. I would use a (red) fibre washer as often used on carburettors, or a soft copper or aluminium washer. Waldi Quote Link to post Share on other sites
RobH Posted February 28, 2020 Report Share Posted February 28, 2020 If you look at the second link I posted above Dan, (the Morris Minor damper) there is a picture of the bottom valve which shows it has no large O ring and that the seal is made with a copper washer. Perhaps yours is the same? What was on there when you dismantled it? Quote Link to post Share on other sites
DanTR6 Posted February 28, 2020 Author Report Share Posted February 28, 2020 49 minutes ago, RobH said: If you look at the second link I posted above Dan, (the Morris Minor damper) there is a picture of the bottom valve which shows it has no large O ring and that the seal is made with a copper washer. Perhaps yours is the same? What was on there when you dismantled it? Rob, the one in the moris link is a later type valve that doesnt have the o-ring part way down, just an o-ring at the bottom. One of my dampers is like this and the body has a conical grove for the o-ring to seat, although no copper washer. The damper im having problems with is different, two o-ring groves and no grove in the body as per the pictures attached, just a washer Quote Link to post Share on other sites
DanTR6 Posted February 28, 2020 Author Report Share Posted February 28, 2020 1 hour ago, Waldi said: An O-ring should sit in a pocket (chamber?). If not, you cannot tighten the bolt. I would use a (red) fibre washer as often used on carburettors, or a soft copper or aluminium washer. Waldi there doesnt seem to be a recess in the body for it although the valve has a grove, it might be that the valve isnt original to the body. When I took it apart it was just the washer. My main concern is that if the wash isnt meant to be there its not loading the valve correctly as it relies on the amount of preload to set the bump damping rate. Most of the bodies ive seen have this grove Quote Link to post Share on other sites
Waldi Posted February 28, 2020 Report Share Posted February 28, 2020 Dan, it is hard to see from a picture, but could it be that a thinner O-ring would fit ok? I’m not familiar with the specifics of these dampers. Waldi Quote Link to post Share on other sites
super6al Posted February 28, 2020 Report Share Posted February 28, 2020 Is it possible the 2 valves have been swapped? The Minor type body should have a copper washer against a flat face & the 2 O ring type valve should have a recess on the body. The other possibility is as you suggest & it has the wrong valve for that type of body. Alan Quote Link to post Share on other sites
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