Sphere part numbers

Unread post by **Dommo** » 09 Jan 2010, 19:33

That makes sense now, I did wonder if it was more than it's name suggested. So when exactly are the rear corner spheres isolated by the anti sink valve? Ie when is there a pressure difference between the main system and rear suspension, when the engine's off, or when building pressure?

A full set from GSF should be (a mere

) £250 then. Any idea how much Pleiades charge for a pressure change on a sphere?

By the way, do you have any idea why the anti sink sphere on GSF says excluding activa:
"N45372 ANTISINK SPHERE-REAR XANTIA ANTI SINK (EXC ACTIVA) 20.90"

From what I can see on servicebox they're all the same

Cheers.

addo · Unread post by **addo** » 09 Jan 2010, 19:59

It's worth checking with Pleiades as to whether his gassing rig "tops up" spheres or fully regasses - I'd suggest the former is more typical. If the (normally round) cap of a regassed sphere has any sort of slot, flats or quadrant bevel ground into it, it's almost certainly being tightened from dead slack (degassed).

In this case, I would suggest going for a used sphere with over 10Bar residual pressure - cheaper to buy.

Unread post by **Dommo** » 09 Jan 2010, 20:12

I presume the flats are to remove the end cap? How else would you regas a sphere if you don't remove the cap? Is it removed and replaced with a cap that has a valve of some type on it for pressure checking/topping up?

Cheers.

Unread post by **CitroJim** » 09 Jan 2010, 21:04

Another role of the anti-sink sphere is as a component of the dual-circuit brakes. Hydraulic Citroens don't have dual circuit brakes in the conventional sense but achieve it by arranging that the dosuer valve is effectively two independent valves and the front and rear brakes are supplied from two different sources of pressure.

The rear anti-sink valve will close whenever there is a pressure differential between the main system and the rear suspension proper. Therefore the valve will operate as soon as main system pressure falls, normally when the engine stops and thus achieve it's main function of preventing the car from sinking. It could come into action whenever big demands are placed on the main system for some reason or if there is a fault. A sudden catastrophic loss of main system pressure would shut the valve and that same loss might also stop the front brakes working. The a-s sphere though, would still provide some reserve to allow the rear brakes to work and therefore the sphere can be considered a safety item from that point of view.

Luckily, such catastrophic losses of pressure are very rare and there are other mechanisms to ensure that the very last circuit to loose pressure will be the brakes, via the security valve.

addo · Unread post by **addo** » 10 Jan 2010, 08:23

Dom,

Some of the more clever OEM style gassing rigs have little "side gripping" means of holding the endcaps - it means you can adjust the pressure slightly without having to go back to dead flat. Look for tiny dimples on opposing sides of the endcap.

Most of the home built and hobbyist gear requires pressurising from zero in one shot, as they can only tighten the cap - hence the one-way quadrant bevel ground in. Some people like to do this anyway, as they reckon an O-ring gas seal is only good for one tighten.

Happy to furnish photos of either or both!

Cheers, Adam.

Unread post by **Dommo** » 10 Jan 2010, 10:01

It's a clever design isn't it! Cheers Jim.

Addo - I'm not sure I understand the two methods you describe, if you could post pictures of them I'd appreciate it and possibly be able to understand it

Do you gas your own spheres??

Jim - have you any idea how Martin gasses up spheres?

Cheers.

Unread post by **CitroJim** » 10 Jan 2010, 10:09

Dommo wrote: Jim - have you any idea how Martin gasses up spheres?

No, in the times I've visited Martin, I've never seen his gassing rig. It could be one of his trade secrets

Unread post by **Dommo** » 10 Jan 2010, 10:30

Ah fair enough.. I'm assuming his methods are probably quite safe for the long term reliability of the spheres?

Unread post by **CitroJim** » 10 Jan 2010, 10:48

Dommo wrote:Ah fair enough.. I'm assuming his methods are probably quite safe for the long term reliability of the spheres?

Oh yes, Martin and his dad before him have been regassing spheres ever since the days of the DS! That's a lot of years and I reckon they have the procedure pretty well licked by now...

Pleiades comes with the very highest recommendation.

addo · Unread post by **addo** » 10 Jan 2010, 10:56

Dommo wrote:Do you gas your own spheres??

Er, no.

Neither hot air nor "P*ss and wind" are acceptable pressurisation media. We have a regassing machine at disposal of the Club's technical occifer.

Pics in a day or so, of the different treatments to endcaps.

Unread post by **Dommo** » 10 Jan 2010, 11:26

Ah fair enough addo, but by the sounds of things you've done some research into it.

Does Martin only work in the week? I tried ringing yesterday with no response.

Do you have a rough price that he charges per sphere for replacement and for regassing? PM me please if you'd rather not post it up on here. I'm just wondering whether its worth me going to him for sphere replacement or whether I should replace them all myself. And then I'd like to know how much I should expect to pay for a pressure test/regass in a couple of years.

Thanks.