D-Special Sphere rebuild

[Buttercup]

at this point i offer an apology to pottsy, i have steered your inquiry a little off topic. . . Bob, post some pics of your rig or i'll be in the doghouse!

Cheers
chris

OK OK......






Accumulator tool (2 views) clamps with 6 x 8mm grub screws around rim.
I grip the other part in my 4 jaw in the lathe. the centre in the tool is held by the lathe tail stock to keep it straight while flogging the short arm. with a big hammer.

The Gas tool, accepts (almost ) all sphere types including accumulators. Head has minimum volume to reduce gas wastage. I have multiple different plug tools to operate original, slotted, smooth round (plug cap has 3 x 3mm grub screws to grip plug) etc. The rig can be mounted inverted to use gravity to locate the O-ring in spheres where O-ring movement is a problem.
It can top up with out wasting gas, as well as recharge from flat.

The Sphere tool .... again hold top in lathe 4 jaw, tool clamps on rim of sphere body, flog short arm....

Any further questions?

I did design a "Super Universal" sphere work centre, with tools attached (so you don't need a lathe as a holder), precharge check and gas rig all built in...... never got it built yet.... but should. If I make.... say 6 units at .... say $1000 each.... any takers ? (not including gas bottle or reg).

 

[pottsy]

Noce work Bob. My mind is working along the same sort of lines. Will do some drawings and post them for comment.

I've just been for a walk up to the local steel supplier and ordered some material.

Now to relax a bit! There are hills!

Cheers, and thanks, Pottsy

PS, Chris, don't stress. When these things stray in topic it's all still interesting.

 

[Hotrodelectric]

Were welded spheres ever original on a Dee?

I'd have to check, but possibly on very late ('74-'75) cars. They were already in use on the CX and GS.

 

[michaelr]

Who in their right mind would fit welded spheres to a Dee? :nownow:

At $60 and available on every street corner,
still not enough reason to ignore the original at $250 If you can find one........

I would. Maybe you think I am crazy, but when I first got my DS back on the road I made many appeals on Aussie Frogs for some split spheres for rebuilding but got zero response. Short of paying a kings ransom for a set from an "expert" I ran the car on welded ones. Better than having the car useless.

I have now a pair of split spheres with removable dampers on the front of the car. I bought diaphragms from Roger Parker and rebuilt them at home using the CCCNSW equipment and gas. The back still rides on welded ones.

 

[DoubleChevron]

I would. Maybe you think I am crazy, but when I first got my DS back on the road I made many appeals on Aussie Frogs for some split spheres for rebuilding but got zero response. Short of paying a kings ransom for a set from an "expert" I ran the car on welded ones. Better than having the car useless.

I have now a pair of split spheres with removable dampers on the front of the car. I bought diaphragms from Roger Parker and rebuilt them at home using the CCCNSW equipment and gas. The back still rides on welded ones.

That's not really surprising. Most removable damper spheres are rusted and buggered (and were binned with the cars). Later cars can have broken discs in the valves (that you can only see once you have pulled htem apart). So anyone that does actually have a spare sphere or two. Will keep them for themselves. It's unlikely anyone will have a quantity of spheres sitting around.

seeya,
shane L.

 

[DoubleChevron]

I have all the gear and diaframs here and can do them, and around 50 spare spheres if bits are needed, but you will have to send them to tassie

Did you buy all of Richos stuff when he got rid of it I wouldn't mind seeing a piccie of his fabricated sphere tools (offline of course, I know he doesn't like his stuff being shared around).

seeya,
Shane L.

 

[Balki]

No i built my own with help from a club member is is a fitter and turner, happy to post pics next time i gas some


Via the aussiefrogs App

 

[DoubleChevron]

No i built my own with help from a club member is is a fitter and turner, happy to post pics next time i gas some


Via the aussiefrogs App

The more piccies, the better for everyone wanting to build one

 

[David S]

Its not just if the engine stalls. If you are on the brakes..... you are off the throttle... at idle, the pump will not replenish the supply quickly enough, specially if the steering is used, and possibly the front height corrector..... Ummm that's why the accumulator is there.... it accumulates flow. To identify which models use a 40 bar accumulator.... its any WITHOUT a separate brake accumulator (except for the early master cylinder ID19 cars (pre 63) ID Safari (I had a '68 one on the road for several years, fantastic car) has a brake accumulator.... so 65 bar is used in the main accumulator.

No, that does not appear to be entirely correct. The parts book shows from 7/72 DV and DT, being Special and Super, neither of which has a brake accumulator, use 60 Bar, then 62Bar accumulators. 65 Bar for DS with brake accumulator. Safari is much like a DS under the skin from the early 60's, which explains 65Bar. There is only one type of regulator listed for all models after 7/72. Prior to 7/72, DV and DT do seem to specify a 40 Bar accumulator.

I have all the gear and diaframs here and can do them, and around 50 spare spheres if bits are needed, but you will have to send them to tassie

They'd be classed as dangerous goods, so shouldn't go by any form of regular mail that might involve air to/from Tas (or anywhere). The limit on allowed maximum pressure is very low, under 1Bar I'm confident, and you are always signing an aviation declaration on even Parcel Post. I'd expect services like Express Post do involve air transfers.

No need to check Roger, the reason is a simple hydraulic one, not a designers whim. The lower the precharge pressure in a sphere, the more volume of hydraulic fluid is required to bring the pressure up to regulator cut-out. If the accumulator precharge is above regulator cut-out.... it will not accumulate at all. If the accumulator precharge is very low, the sphere is almost completely filled with accumulated fluid at cut-out pressure. When the accumulator is discharging flow to the system, one with lower precharge, has more available volume to deliver before the flow exhausts at precharge pressure. Systems with a brake accumulator, use the main accumulator to feed the brake one, thus the reserve flow is much higher. Systems without brake accumulator, rely only on the main accumulator to store flow. It it important that this storage is capable of delivering adequate flow to all the cars systems, at idle, and maintain emergency braking capacity. That is potentially a big ask, specially in an old car with worn pump, worn valves, and high return leakages in the system. If you have a fast cycling regulator cut-out and no brake accumulator, I'd suggest you need know that your parking brake works well, and to drive VERY carefully.

The cut in/out pressures are over 100Bar, so 40, 60, 65 and 62 Bar will always be well below that. The accumulator precharge also limits the pressure available as it tends towards the point of exhaustion, even if there is a larger volume. Low precharge = higher volume, but at a lower pressure ultimately. So more volume alone would not be the only criterion. The welded accumulators are 400cc, which appears to be greater than the two-piece unit volume. I don't know the actual volume. It may be that the larger volume of the welded sphere at least partly compensates for using a 62Bar sphere in place of an original 40 Bar unit. It can be worked out if anyone is keen as the precharge will be compressed to the reg cutout pressure to determine the maximum reserve volume available.

New welded ones supplied for accumulator... what volume? Were welded spheres ever original on a Dee? Who in their right mind would fit welded spheres to a Dee? :nownow: At $60 and available on every street corner, still not enough reason to ignore the original at $250 If you can find one........

You'd avoid the two piece unit wherever possible due to probable overloading and fatigue after probably 40 years in use. Ask UFO about his failure at speed and that is sufficient evidence to argue for binning them and converting to a welded unit if it will physically fit. In a D, the 400cc accumulator fits perfectly well, but not if you use the factory regas plug. CCCNSW has a factory gassing kit from memory and uses these, so this is one application where you have to reuse the original sphere plug and not use the one with the thread in the back to fit into the factory gassing head.

I'd have to check, but possibly on very late ('74-'75) cars. They were already in use on the CX and GS.

Book lists them from 6/74, which makes sense. Like the late CV joint driveshafts. The 62 Bar unit is given as a suitable service replacement for 60 and 65Bar units.

I would. Maybe you think I am crazy, but when I first got my DS back on the road I made many appeals on Aussie Frogs for some split spheres for rebuilding but got zero response. Short of paying a kings ransom for a set from an "expert" I ran the car on welded ones. Better than having the car useless. I have now a pair of split spheres with removable dampers on the front of the car. I bought diaphragms from Roger Parker and rebuilt them at home using the CCCNSW equipment and gas. The back still rides on welded ones.

If the volume is the same, the pressure the same and the damper has the same damping / flow properties as a two piece unit, then there should be no difference. If the is any difference and the other parameters are the same, then it has to come down to the nature of the diaphragms.

 

[pottsy]

OK, setting aside the abstruse discussions above, which are fascinating in their detail and complexity, I've created some drawings of my proposed tool.

Not trying to re-invent the wheel, just my interpretation of how to achieve the end result.

Notice I plan to use hydraulic pressure from the workshop press rather than a percussive method, not for any gentle reason, just as a sort of homage to M Mages.

Comments will, as always, be welcomed.

Cheers, Pottsy

 

[Buttercup]

OK UFO Please explain:

Quote from David S:

"You'd avoid the two piece unit wherever possible due to probable overloading and fatigue after probably 40 years in use. Ask UFO about his failure at speed and that is sufficient evidence to argue for binning them and converting to a welded unit if it will physically fit."

Pending UFO's report....... I'd argue strongly against this. There must be pretty severe mis-treatment of a sphere to "overload it".

Its very easy to respond to a catastrophic failure, with improper science and invalid scare.

 

[Buttercup]

OK, setting aside the abstruse discussions above, which are fascinating in their detail and complexity, I've created some drawings of my proposed tool.

Not trying to re-invent the wheel, just my interpretation of how to achieve the end result.

Notice I plan to use hydraulic pressure from the workshop press rather than a percussive method, not for any gentle reason, just as a sort of homage to M Mages.

Comments will, as always, be welcomed.

Cheers, Pottsy

My initial response to your drawing is:

You might be underestimating the forces needed to initiate unscrewing on some spheres.

I expect that the support cradle is not rigid enough, I expect it will bend significantly under load, allowing the sphere to get completely out of position, and possibly damage the exposed screw thread. You might add gussets, or use significantly heavier material.

Also because the applied torques are displaced laterally, there is a strong twisting moment, that will further try to bend the cradle.

As soon as you get some movement the surfaces bearing on the support and press tool will be inclined such that there will be a very strong force trying to expel the tools (and sphere) from the system.

Also I find that moderate percussion is a big advantage in starting the unscrewing movement.

You might do better to attach 1 tool very strongly to your bench ( and the bench to floor or wall) and use a very long handle on the other tool, and tap with a hammer.

 

[David S]

... Its very easy to respond to a catastrophic failure, with improper science and invalid scare.

For the report of the catastrophic failure mentioned, see:
http://www.aussiefrogs.com/forum/ci...cial-failed-two-piece-accumulator-sphere.html
Invalid scare ??? Why take the risk with a critical component?

Everyone is of course entitled to reach their own conclusions and a range of thoughts are expressed in that thread. The points about cleanliness, testing etc. are well made, especially regarding the regulator. It was possibly not intentional, but they also point to the root concern that you can't really know the service history of some randomly exchanged old accumulator. It might have been on half a dozen different cars, some in poor condition and allowed to run flat.

I would think the improper science is possibly being performed by all the rebuilders of old accumulators and spheres who choose to close their eyes to the possibility that being at least 40yo and maybe run very flat at times when the cars were worthless, could pose a risk of abuse and fatigue. I wonder how many rebuilders take steps to really check for any sign of cracking???

 

[Balki]

looks good potsy but i would give them a bit more thickness around the sphere, also keep the bolt for tightening very close to the hole for the sphere, you might like to leave a lug on the side for shocking it loose with a hammer when it wont budge with the press

 

[pottsy]

Thanks for the feedback chaps.

I take the points about the strength of the cradle and the positioning of the clamp bolts.

I was actually beginning to wonder a bit about the best way to hold the thing in a press, or percussion, situation and begin to suspect the base plate for the cradle needs to be a lot wider and perhaps include the support boss that I mentioned as a spacer.

The angle will certainly change as rotation begins, but that can be offset slightly by starting the position of the clamp bolt and bosses a bit higher I think.

This is just ideas at this stage, certainly based on Bob's lovely work as shown, so the end result will most likely bear little or no resemblance to the drawings. (I'm a practical technician, not a theoretical engineer! )

As far as explosive failures, cracks, etc are concerned I think I have a double strategy for that.

First part is that I have always used one piece accumulators in my D's and Xantia. This choice was dictated primarily in never having had a two piece accumulator available to me as well as not being overly concerned with originality issues. I can believe that the original two piece accum was specified for sound reasons, but time, and practicality, usually dictate moving on, in my humble.

The second string to that particular bow is that I only plan to work with suspension spheres, which, while experiencing the same sorts of pressures in general, are not subject to the same sort of stresses potentially present in an accumulator, not the least being the constant (albeit small) shock loading of the unloading/loading process as well as the risk of having been run flat.

Combined with careful inspection while dismantled, I'm reasonably confident that things will be fine.

Thanks again for all the feedback. Now, all I need is the time and materials to start, neither of which are readily present just now.

Cheers, Pottsy

 

[Buttercup]

Re exploding acc spheres....

I am not convinced either way.
The pic from UFO shows pre-existing cracking, probably due to run flat shock/fatigue.
This cracking starts at the base of the female thread, where there is a stress focus caused by the machining.
I don't believe that this failure was caused by regulator malfunction.
Other reported incidents do point to regulator malfunction.
Suspension spheres cannot be subject to equivalent shock loads, even when completely flat.
Its possible that inspection would not detect the start of such cracks.

I believe that re-using acc spheres of known history is not a serious risk, (I have a few of these).

I will continue to use 2 piece acc spheres..... that I have inspected and prepared myself.

 

[David S]

...

I believe that re-using acc spheres of known history is not a serious risk, (I have a few of these).

I will continue to use 2 piece acc spheres..... that I have inspected and prepared myself.

That's a reasonable approach to the issue. The point of difference being that you have some idea about the history of the components involved and the technical ability to test both the regulator function and sphere/accumulator components.

To stay with the 2 piece accumulator, proper testing of increasingly aged components will become more important as part of the rebuilding process. Of course, there seems to be no choice with an LHS system unless it is converted to LHM. Brake fluid and green spheres don't seem to get on.

 

[GreenBlood]

That's a reasonable approach to the issue. The point of difference being that you have some idea about the history of the components involved and the technical ability to test both the regulator function and sphere/accumulator components.

To stay with the 2 piece accumulator, proper testing of increasingly aged components will become more important as part of the rebuilding process. Of course, there seems to be no choice with an LHS system unless it is converted to LHM. Brake fluid and green spheres don't seem to get on.

Condition of the pressure regulator has to be considered especially after a sphere failure, as witnessed here. . .
http://www.aussiefrogs.com/forum/citro%EBn-forum/100311-xm-fdv-wtb.html

This is an XM, but clearly illustrates the potential pressures involved, a failed sphere replaced with the same result. . . i.e. two blown spheres!

Darrin at Citroen Classics UK shows the changeover for two part and welded spheres for ID/D Citroens.

I also note 648 shows a welded sphere in the illustration of the pressure regulator.

I can no longer find the link within Jint's site but it is stated in Citroen's notes that the use of 60-65 bar accumulator happened on all cars fitted with power steering.

Cheers
Chris

 

[pottsy]

OK, here's a revision of my first concept.

The only addition I may consider is to make the end pieces of the cradle able to clamp the sphere in position, say by the larger one having the full 360 deg hole and the smaller one with a clamping bar.

The cradle itself can be clamped or bolted to the bed of the press, or such large object as is needed.

Otherwise I've taken into account the comments so far.

Let me know what we all reckon please.

Cheers, Pottsy

 

[David S]

A good lesson from Chimbu's burst accumulator thread.

Darrin's comparison is for the suspension spheres, while the 2-piece accumulator is about 2/3rds that size. Is there a quoted volume?

Did pas become a standard fitting after 1972? It would always have had the 7 piston pump. Is that a better test for 62 vs 40 Bar than the absence/presence of the brake accumulator?