Aprilia NS 1692 lives again! But I need some help please

[davidwheeler]

...from which we can see that it would appear that Ben's ball valve has migrated from the bottom of the shock absorber rod tunnel (and so visible from underneath) to the bottom of the shock absorber rod itself.  My setup is somewhere between the two having a ball valve at the bottom of the rod and a filler for the bottom half of the suspension but otherwise first series bits.  There is no communication between the shock absorber and the bottom chamber which serves to lubricate the bottom sleeve only.

Now to the sad bit.  I have stripped my shock absorbers (only needed to make two special tools) and discovered them to be filled with woil.  This substance used to lubricate Lambda engines before the advent of uncracked heads and seemed to do little harm but left to rot in an Aprilia front suspension it has wreaked havoc.  Of the two pistons, one is severely corroded as is its tunnel  which is the inside of the kingpin and not clearly removable from the axle shaft (unlike a Lambda).  The other one is not so bad.  The non return shim/washer that sits on the piston has disintegrated on both sides, hence the total lack of damping that I had mistakenly attributed to oil leakage.  I have made new shims (amazing what can be done with a hole punch and a Swiss Army penknife) and restored damping to the better side but the corroded side is weak though I can improve it a bit I guess by using heavier oil. 

I think I need another axle!  HELPP!! Does anyone have one kicking around in the back of the shed?  Fortunately the new slidy bits I bought from Cavalllito in 1970 are still OK so wear in the kingpin sleeves does not matter.  The internals could be first or second as I am sure it is possible to retrofit Ben's ball valve (bottom left box on 1st series) into the second series lower bush (38-606A etc).  Incidentally, I am at a loss to understand what 38-604A doea for a living as it merely floats up and down on the shaft.

P.S.   I checked out my Lambda front suspension.  The shim is on the top of the holey piston not on the bottom as in the Aprilia so it works in the opposite direction!!

[ColinMarr]

David,

Ah now I understand – I thought you said your car was first series and when I posted all that guff about screwing on a hand operated pump to get oil through ball valves at the top of the tubes, it must have been confusing. And of course the 1937 Light Car article is irrelevant to you, but it’s still available should anyone else want it.

Interesting to see how S2 Aprilia front suspension is like the Aurelia with the ‘hardness/ride’ adjustment lever screw on the top, where the filler used to be. With my B20 the setting I used was first to close that lever down and then undo it by about ¾ turn.

I don’t much like the sound of ‘woil’! But pleased to see that you are getting it all sorted.

Anyway, nothing to do with Aprilia front suspension, but in response to an off-forum question, here below is a photo of my Flaminia Sport, which I referred to earlier. It was taken in 1970 by the late Roger Perry.

Colin

[davidwheeler]

Correction!!  I spent much of last night twisting my brain in topological knots and realised that the Aprilia shock absorber rod is fixed relative to the stub axle whereas the Lambda one is fixed relative to the chassis so both work to allow the wheel to drop freely but prevent it from bouncing up, thus gluing it to the road.  I just like to get things right!

Went for a long drive this morning, car feels much better even if it is a little soft on the offside fore.  I have now screwed up the rear shock absorbers and will see what that will do...

Incidentally, third gear seems to be staying in a bit better too.

[ben]

David
            Thanks for the S2 picture which I've not seen before.
            On the S1 you can't get the damper rod and piston out from the top. I suspect it is the same for the S2 but can't be sure from the pic. Perhaps you know by now!

[ben]

Just read the rest of your post. Clearly the S2 rod etc does come out through the top!

To correct my earlier suggestion, even on the S1 the ball valve is not visible, as I now realise the lower end of the damper rod tube is closed off with a brazed on disc which was not shown very clearly on my drawing. The S2 seems the same in this respect.

38-604A acts as a guide. It is clamped inside the pillar by a ridiculously slim threaded sleeve (38-73075A) and sits on a ledge formed inside the pillar which is incidentally the reason why the S1 damper rod etc wont come out through the top.

[davidwheeler]

But the rod does come out through the top.  The threaded sleeve is removed with a tool of 33mm external diameter with four equally spaced 5mm wide teeth on it and the piston then slides out easily.  I wonder what happened to the ball valve 38-73xxx shown in the bottom left of the series one drawings and that Ben saw from below??

Please can anyone lend me a piston rod that I can put in my offside suspension while I get mine rebuilt?  The nearside works well and gives me hope that a restored piston will fit well enough to save an axle change.

Incidentally, before I raid my local motor factors (and Alas! for LSUK) has anyone tried fitting telescopic dampers to the rear suspension and if so what?

[ben]

   OK I concede the rod comes out of the top for both S1 and S2 once that thin sleeve is unscrewed. See my previous post for conceding that the ball valve is not visible from below.

   Still not clear how much S2 you have in your S1 or vice versa.I have an S1 rod you could borrow but do you need the rod or just the piston? Is your rod clamped between the two springs at the top. I cant see these springs in the S2 picture.Do you have the automatic oiler?
   In fact what is your Ref No (on the plate) and/or Chassis No (on the edge of the bonnet opening).S2 (Tipo 438) Ref Nos start at 10355 and Ch Nos at20077 according to my data).
   

[ColinMarr]

David,

Things you might have missed:

Under this thread: 12 October 2008

I don’t think you can get access to these (the valves) without withdrawing the assembly upwards through the hole in the front wing, for which I think you do need special tools to undo the threaded sleeves down inside the top tube.


Under - Rear suspension: why? how? 7 February 2008

A common mod in the ‘60s was to replace the rear dampers with Koni type telescopic units. The bodge was to cut into the floor pan just ahead of the fuel tank and fit bent sheet-steel ‘towers’ - simply bolted to the floor - to take the top of the damper, with the lower eye on the trailing arm fitting. Purists would object! I wasn’t tempted – I needed the boot space.

Colin

[davidwheeler]

1/True, special tool described above.
2/I don't fancy cutting holes I think I'll look for some lever arm shockers.
3/Curious!!  Ben kindly sent me a shock absorber piston bit it is only 25mm diameter whereas my indisputably first series pattern one is 33mm(?32mm) diameter!

[ben]

I wonder if the bits I sent you are from an Appia. My storage system is a bit Haphazard!

[ben]

Ive just checked another damper piston which I believe to be Aprilia 1st series (but from a different axle) and it is the same as the one I sent you i.e. 24.9 mm.
                                   Ben.

[Tony Stephens]

From memory (and I last had an Aprilia gearbox to bits about 35 years ago) a cause of jumping out of third gear can be excess end play on the output shaft due to wear in the tail bearing which seems to have a hard life for some reason. Deal with it promptly or the dog engagement will be spoiled which makes it all much more difficult.

The other cause can be that the tail bearing is not secured in the gearbox casing properly. You used to be able to get what appeared at first sight to be an exact replacement, however the recess in the outer track was not wide enough for the little thrust pin and people did not notice, and left the bearing free to slip backwards with the same effect as in my first para. Grind the toe of the thrust pin carefully to fit (if you must!)

Anyway that's my verdict, with the usual caveats about failing brain etc.

[davidwheeler]

I have just taken out a damper piston and I find it to be 32.8mm so I think my axle is 1st/2nd series transition.  It may not be the original axle for the car as I rescued front and rear suspension from a near Bristol scrap yard in 1969, reputed to have come off a tourer but the rear was fully independent so that is unlikely.  Anyway, shortly after I stripped the cWP so fitted the fresh rear suspension and may have done the same for the front at some time.  The new bits I bought from Cavallitto in 1971 fitted it though.

[davidwheeler]

Colin Joy sold me a spare axle he had just acquired with a car so I fitted it last week.  What a struggle!  Two of the fixing bolts sheared off and it took me four days to drill them out and tap the holes (to M12x1.5)  It took me a day and several drills to realise that the sheared surface was work hardened but after I had ground them off and got some cobalt drills (heavy pressure and slow speed is the trick) working upside down in the pit I managed it.  Off course the holes had wandered off centre a bit but easing the holes in the axle to 13mm took care of that.  At least I could put the axle in the drilling machine.  I also, foolishly, tried to change the road springs as Colin had said he though there were some broken springs in the suspension.  Getting the bottom off is easy (I have a tool made for me 40 years ago which I put between the bottom of the pillar assembly and the floor and lower the car onto it) but locating the thread to put it back on took a couple of hours fiddling - and the spring and bearing surfaces were fine so I did not bother on the other side.  I did put in my new (in 1971 but not used since) top end bearing surfaces in, replaced a couple of piston retaining springs and renewed the washers that control flow through the pistons as these are invariably broken.  The result is an Aprilia that is once again an utter delight.  Hooray!(oorayoorayooray)