Hi all,

In the spirit of d-i-y I've taken the non return valve out of my Bambi
75/150 compressor and found out why it is leaking.

The actual valve is small rubber 'bullet' (10mm diameter x 10mm long)
that has a fairly light coil compression spring clipped over a
shoulder at the back and this 'bullet' is pushed against a conical
seat, initially by the spring than then the stored air pressure (~120
psi).

From close inspection it looks like something has been trapped in the
valve and formed a slight ridge in the rubber bullet face, stopping it
sealing properly.

So, on the grounds I've little to lose (I'm probably in for a new
valve anyway[1]), if I could gently hold said bullet in the lathe,
what sort of tool (hand or machine) would be most likely to get me
re-surface this without ripping it up do you think please?

The rubber is about the consistency of a pencil rubber.

An alternative solution could be a 10mm diameter rubber ball and I
could always turn a small nylon cup to carry the spring etc.

All the best ..

T i m

[1] My local Bambi dealer doesn't carry a spare valve so I've got a
bit of time to play. Also it seems a shame to throw away a perfectly
good, nicely machined and chromed brass fitting for the sake of a 10p
rubber valve. :-(

On 20 Aug, 11:06, T i m wrote:
Hi all,

In the spirit of d-i-y I've taken the non return valve out of my Bambi
75/150 compressor and found out why it is leaking.

The actual valve is small rubber 'bullet' (10mm diameter x 10mm long)
that has a fairly light coil compression spring clipped over a
shoulder at the back and this 'bullet' is pushed against a conical
seat, initially by the spring than then the stored air pressure (~120
psi).

From close inspection it looks like something has been trapped in the
valve and formed a slight ridge in the rubber bullet face, stopping it
sealing properly.

So, on the grounds I've little to lose (I'm probably in for a new
valve anyway[1]), if I could gently hold said bullet in the lathe,
what sort of tool (hand or machine) would be most likely to get me
re-surface this without ripping it up do you think please?

The rubber is about the consistency of a pencil rubber.

An alternative solution could be a 10mm diameter rubber ball and I
could always turn a small nylon cup to carry the spring etc.

All the best ..

T i m

[1] My local Bambi dealer doesn't carry a spare valve so I've got a
bit of time to play. Also it seems a shame to throw away a perfectly
good, nicely machined and chromed brass fitting for the sake of a 10p
rubber valve. :-(

It will grind nicely,but keep a good hold of it.

"T i m" wrote in message
...


So, on the grounds I've little to lose (I'm probably in for a new
valve anyway[1]), if I could gently hold said bullet in the lathe,
what sort of tool (hand or machine) would be most likely to get me
re-surface this without ripping it up do you think please?

The rubber is about the consistency of a pencil rubber.

Some fine wet or dry paper I would think.

Just cup it in the hand and rotate the rubber slowly.

"T i m" wrote in message
...
Hi all,

In the spirit of d-i-y I've taken the non return valve out of my Bambi
75/150 compressor and found out why it is leaking.

The actual valve is small rubber 'bullet' (10mm diameter x 10mm long)
that has a fairly light coil compression spring clipped over a
shoulder at the back and this 'bullet' is pushed against a conical
seat, initially by the spring than then the stored air pressure (~120
psi).

From close inspection it looks like something has been trapped in the
valve and formed a slight ridge in the rubber bullet face, stopping it
sealing properly.

So, on the grounds I've little to lose (I'm probably in for a new
valve anyway[1]), if I could gently hold said bullet in the lathe,
what sort of tool (hand or machine) would be most likely to get me
re-surface this without ripping it up do you think please?

The rubber is about the consistency of a pencil rubber.

of wood An alternative solution could be a 10mm diameter rubber ball and I
could always turn a small nylon cup to carry the spring etc.

All the best ..

T i m

[1] My local Bambi dealer doesn't carry a spare valve so I've got a
bit of time to play. Also it seems a shame to throw away a perfectly
good, nicely machined and chromed brass fitting for the sake of a 10p
rubber valve. :-(



Do you have a conical drill bit? drill a conical hole 10mm wide in a bit of
wood,then turn the rubber bullet in the wood hole.
Doesnt take much effort to smooth off rubber.

George wrote:
"T i m" wrote in message
...
Hi all,

In the spirit of d-i-y I've taken the non return valve out of my Bambi
75/150 compressor and found out why it is leaking.

The actual valve is small rubber 'bullet' (10mm diameter x 10mm long)
that has a fairly light coil compression spring clipped over a
shoulder at the back and this 'bullet' is pushed against a conical
seat, initially by the spring than then the stored air pressure (~120
psi).

From close inspection it looks like something has been trapped in the
valve and formed a slight ridge in the rubber bullet face, stopping it
sealing properly.

So, on the grounds I've little to lose (I'm probably in for a new
valve anyway[1]), if I could gently hold said bullet in the lathe,
what sort of tool (hand or machine) would be most likely to get me
re-surface this without ripping it up do you think please?

The rubber is about the consistency of a pencil rubber.

of wood An alternative solution could be a 10mm diameter rubber ball and I
could always turn a small nylon cup to carry the spring etc.

All the best ..

T i m

[1] My local Bambi dealer doesn't carry a spare valve so I've got a
bit of time to play. Also it seems a shame to throw away a perfectly
good, nicely machined and chromed brass fitting for the sake of a 10p
rubber valve. :-(



Do you have a conical drill bit? drill a conical hole 10mm wide in a bit of
wood,then turn the rubber bullet in the wood hole.
Doesnt take much effort to smooth off rubber.


Indeed. Or simply mount in anything that spins and hold some fine wet
and dry against it.

Or even make a mould and cast one out of silicone ...

On Wed, 20 Aug 2008 05:05:27 -0700 (PDT), wrote:


So, on the grounds I've little to lose (I'm probably in for a new
valve anyway[1]), if I could gently hold said bullet in the lathe,
what sort of tool (hand or machine) would be most likely to get me
re-surface this without ripping it up do you think please?


It will grind nicely,but keep a good hold of it.

Ok ta and the keeping hold of it seems to be the issue!

I tried putting it in the lathe earlier but it's just too unstable to
be reliable (and I've images of it flying across the workshop, never
to be seen again) :-(

What might work though is if I can hold it further in the lathe chuck,
counter drill a small hole from the back and then glue in a small
plastic rod (knitting needle etc) that should give me something to
hold it with to be able to spin it whilst dressing it on some
wet-n-dry / file / whatever?

All the best ..

T i m

On Wed, 20 Aug 2008 13:23:06 +0100, "dennis@home"
wrote:



"T i m" wrote in message
.. .


So, on the grounds I've little to lose (I'm probably in for a new
valve anyway[1]), if I could gently hold said bullet in the lathe,
what sort of tool (hand or machine) would be most likely to get me
re-surface this without ripping it up do you think please?

The rubber is about the consistency of a pencil rubber.

Some fine wet or dry paper I would think.

Just cup it in the hand and rotate the rubber slowly.

Understood.

I'm not quite sure yet how important concentricity is compare with
surface smoothness. The existing item looks quite smooth till you look
at it closely but if you view it in profile and slowly rotate it it
also looks a bit wonkey (like it's not sat square in the seat for a
fair while).

All the best ..

T i m

On Wed, 20 Aug 2008 13:08:03 GMT, "George"
wrote:



Do you have a conical drill bit?

Conical burr probably George.

drill a conical hole 10mm wide in a bit of
wood,then turn the rubber bullet in the wood hole.

Ooo, that's a goodun. I still need to sort the holding bit then.

Doesnt take much effort to smooth off rubber.

Ok, thanks.

All the best ..

T i m

On Wed, 20 Aug 2008 14:11:38 +0100, The Natural Philosopher
wrote:


Do you have a conical drill bit? drill a conical hole 10mm wide in a bit of
wood,then turn the rubber bullet in the wood hole.
Doesnt take much effort to smooth off rubber.


Indeed. Or simply mount in anything that spins and hold some fine wet
and dry against it.

That's the tricky bit as if you hold enough of it to be sure it's held
there isn't anything left to tidy. :-(

And alternative to me fitting it on a plastic mandrel above I could
glue it temporarily to a holder as there is enough rubber shoulder
(that the little coil spring slips over) for me to shave it off the
mount once finished.

Or even make a mould and cast one out of silicone ...

Ah, there's an idea. At least I could turn a plug in something harder
(like ally) but I think that might be going a bit too far (time wise ,
well depending on how much the replacement one is of course).

Alternatively I've been looking about for a plain rubber ball of about
10 mm diameter. I think a mate has found something that is .43"
(~10.9mm) in paint ball gun round. It might just be too big though and
ironically, being a bit smaller than 10mm would be ok / better.

I've also just had a quick look through a pound shop in case a kids
game had a suitable ball but the nearest I saw was a mini snooker set
and they were hard plastic. :-(

All the best ..

T i m

On Aug 20, 3:48*pm, T i m wrote:
On Wed, 20 Aug 2008 14:11:38 +0100, The Natural Philosopher
wrote:

Do you have a conical drill bit? drill a conical hole 10mm wide in a bit of
wood,then turn the rubber bullet in the wood hole.
Doesnt take much effort to smooth off rubber.

Indeed. Or simply mount in anything that spins and hold some fine wet
and dry against it.

That's the tricky bit as if you hold enough of it to be sure it's held
there isn't anything left to tidy. :-(

And alternative to me fitting it on a plastic mandrel above I could
glue it temporarily to a holder as there is enough rubber shoulder
(that the little coil spring slips over) for me to shave it off the
mount once finished.



Or even make a mould and cast one out of silicone ...

Ah, there's an idea. At least I could turn a plug in something harder
(like ally) but I think that might be going a bit too far (time wise ,
well depending on how much the replacement one is of course).

Alternatively I've been looking about for a plain rubber ball of about
10 mm diameter. I think a mate has found something that is .43"
(~10.9mm) in paint ball gun round. It might just be too big though and
ironically, being a bit smaller than 10mm would be ok / better.

I've also just had a quick look through a pound shop in case a kids
game had a suitable ball but the nearest I saw was a mini snooker set
and they were hard plastic. :-(

All the best ..

T i m

plastic probably would work if you lined the valve seat with soft
silicone.


NT

"T i m" wrote in message
...
Hi all,

In the spirit of d-i-y I've taken the non return valve out of my Bambi
75/150 compressor and found out why it is leaking.

The actual valve is small rubber 'bullet' (10mm diameter x 10mm long)
that has a fairly light coil compression spring clipped over a
shoulder at the back and this 'bullet' is pushed against a conical
seat, initially by the spring than then the stored air pressure (~120
psi).

From close inspection it looks like something has been trapped in the
valve and formed a slight ridge in the rubber bullet face, stopping it
sealing properly.

So, on the grounds I've little to lose (I'm probably in for a new
valve anyway[1]), if I could gently hold said bullet in the lathe,
what sort of tool (hand or machine) would be most likely to get me
re-surface this without ripping it up do you think please?

The rubber is about the consistency of a pencil rubber.

An alternative solution could be a 10mm diameter rubber ball and I
could always turn a small nylon cup to carry the spring etc.

All the best ..

T i m

[1] My local Bambi dealer doesn't carry a spare valve so I've got a
bit of time to play. Also it seems a shame to throw away a perfectly
good, nicely machined and chromed brass fitting for the sake of a 10p
rubber valve. :-(


If you haven't already tried the suggestions - the fiddly part with rubber
being finding a piece as hard/soft/solvent proof etc. as the original; if
you can find a piece of the right stuff, I find an old set of lab
technician's cork borers often comes in useful for making washers/bungs and
the like - you might find that your original can actually be *revived*.

We used to sell 'blanket reviver' for rubber printing blankets. This was
basically a mixture of white spirit and a solvent like dry cleaning fluid or
paint thinners. This swells the rubber and takes off the glaze. The right
mix can make rubber double or treble in size or more with soaking. In your
case you only need to soak it long enough to take out the ridge. Note that
while the rubber is swollen full of solvent it will be weak so let it dry to
a 'no smell of solvent' state before you put it back.

Academic as you've probably finished by now...

S

On Thu, 21 Aug 2008 21:15:48 +0100, "Spamlet"
wrote:


[1] My local Bambi dealer doesn't carry a spare valve so I've got a
bit of time to play. Also it seems a shame to throw away a perfectly
good, nicely machined and chromed brass fitting for the sake of a 10p
rubber valve. :-(


If you haven't already tried the suggestions - the fiddly part with rubber
being finding a piece as hard/soft/solvent proof etc. as the original; if
you can find a piece of the right stuff, I find an old set of lab
technician's cork borers often comes in useful for making washers/bungs and
the like - you might find that your original can actually be *revived*.

Ooo, no I haven't tried anything as yet as I have been busy elsewhere
and was waiting for a call re how much a replacement was. Good news,
£19 for the part, bad news £50 minimum order and £20 postage!

We used to sell 'blanket reviver' for rubber printing blankets.

Ok

This was
basically a mixture of white spirit and a solvent like dry cleaning fluid or
paint thinners. This swells the rubber and takes off the glaze. The right
mix can make rubber double or treble in size or more with soaking. In your
case you only need to soak it long enough to take out the ridge. Note that
while the rubber is swollen full of solvent it will be weak so let it dry to
a 'no smell of solvent' state before you put it back.

Oooo ..

Academic as you've probably finished by now...

Not at all, so, where do I find said potion please or are you saying
it is simply white spirit and dry cleaning fluid (or was that just a
guess / example) and we don't know the ratios etc?

All the best ..

T i m

"T i m" wrote in message
...
On Thu, 21 Aug 2008 21:15:48 +0100, "Spamlet"
wrote:


[1] My local Bambi dealer doesn't carry a spare valve so I've got a
bit of time to play. Also it seems a shame to throw away a perfectly
good, nicely machined and chromed brass fitting for the sake of a 10p
rubber valve. :-(


If you haven't already tried the suggestions - the fiddly part with rubber
being finding a piece as hard/soft/solvent proof etc. as the original; if
you can find a piece of the right stuff, I find an old set of lab
technician's cork borers often comes in useful for making washers/bungs
and
the like - you might find that your original can actually be *revived*.

Ooo, no I haven't tried anything as yet as I have been busy elsewhere
and was waiting for a call re how much a replacement was. Good news,
£19 for the part, bad news £50 minimum order and £20 postage!

We used to sell 'blanket reviver' for rubber printing blankets.

Ok

This was
basically a mixture of white spirit and a solvent like dry cleaning fluid
or
paint thinners. This swells the rubber and takes off the glaze. The
right
mix can make rubber double or treble in size or more with soaking. In
your
case you only need to soak it long enough to take out the ridge. Note
that
while the rubber is swollen full of solvent it will be weak so let it dry
to
a 'no smell of solvent' state before you put it back.

Oooo ..

Academic as you've probably finished by now...

Not at all, so, where do I find said potion please or are you saying
it is simply white spirit and dry cleaning fluid (or was that just a
guess / example) and we don't know the ratios etc?

All the best ..

T i m

Now you're asking, as I used to be in a lab, with plenty of different
solvents to try. For real spectacular swelling, chloroform was very good on
it's own. But, where a balance had to be struck between cleaning/reviving
and dissolving - plus the fire risk and toxicity and cost had to be
considered too - various mixtures were used. Most of ours tended to be cheap
white spirit, plus xxx, or cheap iso propyl alcohol plus xxx. It's a long
time ago now, but I think the blanket reviver was the white spirit plus
tri-chloro-ethane {'Trike': Which is similar to the per-chloro ethane -
'Perk'- they use in dry cleaners.)

These chemicals are only the 'preferred ones' because of the flammability or
toxicity of others that might otherwise be suitable (Carbon tetrachloride
having been the preferred dry cleaning solvent before safer alternatives
came along.)

In your case you are not so concerned about flammability and solvent abuse,
so you could try petrol for starters, or lighter fluid (though obviously,
these are not going to work if yours is the same sort of 'rubber' they make
fuel lines out of...). 'White spirit' itself is already a hotch potch
mixture that can be very variable, and some that you have to hand might
already be enough to swell the rubber a bit. Then there's nail varnish
remover - the 'pear drops' kind rather than the acetone kind. You may even
find that 'penetrating oils' like 'three in one' or 'plus gas', may do the
job, as we used to make a similar solution with the above mentioned 'trike'
with a drop of oil in: the solvent does the penetrating, and leaves a dab of
oil behind once it evaporates.

Take care if trying more severe mixes like cellulose thinners or paint
stripper, as these may dissolve your 'rubber' - rubber itself being a
blanket term for all manner of things. On the other hand, a brush
reviver/cleaner that contains methylene chloride (Dichloro-methane), might
be just the job.

See what you have around. Note that swelling may take several hours, but
check at first that your sample is not going to turn into a sticky mess.

Take care when experimenting: outdoors: no flames (Even the non-flammables
can break down into carcinogens on the end of a lighted fag for example.).

S

On Thu, 21 Aug 2008 22:32:59 +0100, "Spamlet"
wrote:


Not at all, so, where do I find said potion please or are you saying
it is simply white spirit and dry cleaning fluid (or was that just a
guess / example) and we don't know the ratios etc?

All the best ..

T i m

Now you're asking, as I used to be in a lab, with plenty of different
solvents to try.

Cool weg

For real spectacular swelling, chloroform was very good on
it's own. But, where a balance had to be struck between cleaning/reviving
and dissolving - plus the fire risk and toxicity and cost had to be
considered too - various mixtures were used. Most of ours tended to be cheap
white spirit, plus xxx, or cheap iso propyl alcohol plus xxx. It's a long
time ago now, but I think the blanket reviver was the white spirit plus
tri-chloro-ethane {'Trike': Which is similar to the per-chloro ethane -
'Perk'- they use in dry cleaners.)

Understood.

These chemicals are only the 'preferred ones' because of the flammability or
toxicity of others that might otherwise be suitable (Carbon tetrachloride
having been the preferred dry cleaning solvent before safer alternatives
came along.)

Ok .. and I bet they didn't smell as good? :-(

In your case you are not so concerned about flammability and solvent abuse,
so you could try petrol for starters, or lighter fluid (though obviously,
these are not going to work if yours is the same sort of 'rubber' they make
fuel lines out of...).

Well this rubber is black (not much help that I know) and about the
consistency of a firm pencil rubber (but not as firm as an ink
rubber). You can pinch it tween finger and thumb and distort it but
not pinch it flat (or anywhere near). I guess it would be suitable to
not be affected by air pressure, water (condensate) and oil (it's not
an 'oil free' compressor).

'White spirit' itself is already a hotch potch
mixture that can be very variable, and some that you have to hand might
already be enough to swell the rubber a bit.

Ok.

Then there's nail varnish
remover - the 'pear drops' kind rather than the acetone kind.

Ah, I'll ask the girls what they have. I have 5L of Acetone myself.
;-)

You may even
find that 'penetrating oils' like 'three in one' or 'plus gas', may do the
job, as we used to make a similar solution with the above mentioned 'trike'
with a drop of oil in: the solvent does the penetrating, and leaves a dab of
oil behind once it evaporates.

Ok.

Take care if trying more severe mixes like cellulose thinners or paint
stripper, as these may dissolve your 'rubber' - rubber itself being a
blanket term for all manner of things.

Ah. :-(

On the other hand, a brush
reviver/cleaner that contains methylene chloride (Dichloro-methane), might
be just the job.

Ok, not ever used that I don't think.

See what you have around. Note that swelling may take several hours, but
check at first that your sample is not going to turn into a sticky mess.

Luckily I've got most the stuff on yer list inc Tetrosyl, Panel Wipe
(Low flash-point hydrocarbon solvent), Carb cleaner:

NAPHTHA (PETROLEUM) HYDROTREATED LIGHT 100/140 30-60%
EINECS: 265-151-9 CAS: 64742-49-0
[F] R11; [Xi] R38; [N] R51/53; [Xn] R65; [-] R67
• PROPAN-2-OL 10-30%
EINECS: 200-661-7 CAS: 67-63-0
[F] R11; [Xi] R36; [-] R67
• PROPANE 10-30%
EINECS: 200-827-9 CAS: 74-98-6
[F+] R12
• BUTANE 1-10%
EINECS: 203-448-7 CAS: 106-97-8
[F+] R12
• DIACETONE ALCOHOL 1-10%
EINECS: 204-626-7 CAS: 123-42-2
[Xi] R36
• METHANOL 1%
EINECS: 200-659-6 CAS: 67-56-1
[F] R11; [T] R23/24/25; [T] R39/23/24/25

;-)

So, what is the plan here? I soak said rubber thing in a small pot of
whatever for n time and then let it evaporate out again and hope
that during the swelling and (presumably) reduction process the rubber
will lose any distortion?


Take care when experimenting: outdoors: no flames (Even the non-flammables
can break down into carcinogens on the end of a lighted fag for example.).

Ok ta (but don't smoke or work by candlelight ... yet!) ;-)

All the best ..

T i m

T i m wrote:

I tried putting it in the lathe earlier but it's just too unstable to
be reliable (and I've images of it flying across the workshop, never
to be seen again) :-(

The trick for machining rubber is to cool it down to about -50 deg C
first (then work quickly). I've seen this done and it's very effective,
but the trouble is that a small workpiece like yours will probably warm
up too quickly for the technique to be useful.

Freezer spray or a Peltier cooler module from RS will get you down to
somewhere near the target temperature.

--
Andy

In message , Andy Wade
writes
T i m wrote:

I tried putting it in the lathe earlier but it's just too unstable to
be reliable (and I've images of it flying across the workshop, never
to be seen again) :-(

The trick for machining rubber is to cool it down to about -50 deg C
first (then work quickly). I've seen this done and it's very
effective, but the trouble is that a small workpiece like yours will
probably warm up too quickly for the technique to be useful.

Freezer spray or a Peltier cooler module from RS will get you down to
somewhere near the target temperature.

And what's wrong with a british summer ?

--
geoff

On Wed, 20 Aug 2008 15:39:43 -0700 (PDT), wrote:



plastic probably would work if you lined the valve seat with soft
silicone.

I like it, rather than looking for rubber 'valve' .. ;-)

However I'm not sure how easy it will be to re-engineer in practice as
the seat is at the bottom of a fairly deep body.

Something else to think about though if the rubber won't recover
chemically (I've tried lighter fluid so far (no change), now on white
spirit).

All the best ..

T i m

On Sat, 23 Aug 2008 01:12:52 +0100, Andy Wade
wrote:

T i m wrote:

I tried putting it in the lathe earlier but it's just too unstable to
be reliable (and I've images of it flying across the workshop, never
to be seen again) :-(

The trick for machining rubber is to cool it down to about -50 deg C
first (then work quickly). I've seen this done and it's very effective,
but the trouble is that a small workpiece like yours will probably warm
up too quickly for the technique to be useful.

Freezer spray or a Peltier cooler module from RS will get you down to
somewhere near the target temperature.

Thanks Andy but I think it will be easer to buy a new valve (as
interesting an experiment it would be etc). ;-)

I haven't yet though ... still waiting to stumble on that perfect
rubber item to be a replacement valve ...

All the best ..

T i m

Spamlet wrote:
Take care when experimenting: outdoors: no flames (Even the non-flammables
can break down into carcinogens on the end of a lighted fag for example.).

IIRC one of the breakdown products is phosgene. Not a modern war gas,
but still pretty poisonous.

Andy

On Thu, 21 Aug 2008 22:32:59 +0100, "Spamlet"
wrote:


See what you have around. Note that swelling may take several hours, but
check at first that your sample is not going to turn into a sticky mess.

Right, so far I've soaked the rubber valve for several hours in:
lighter fluid, white spirit and panel wipe with no affect at all?

If that means anything to anyone (from their likely chemical content)
what sort of things should I try next please?

All the best ..

T i m

"T i m" wrote in message
...
On Thu, 21 Aug 2008 22:32:59 +0100, "Spamlet"
wrote:


See what you have around. Note that swelling may take several hours, but
check at first that your sample is not going to turn into a sticky mess.

Right, so far I've soaked the rubber valve for several hours in:
lighter fluid, white spirit and panel wipe with no affect at all?

If that means anything to anyone (from their likely chemical content)
what sort of things should I try next please?

All the best ..

T i m

Not sure what the 'panel wipe' is, but all the others are 'non-polar'
paraffin solvents. So you now move on to the other kinds - your ketones like
acetone, and mixtures like 'cellulose thinners'; and the chlorinated
compounds. If you don't have any chlorinated solvents in your rather
enviable list of what you have to hand, getting some methylene
chloride/dichloromethane containing brush cleaner may be as near as you can
get in 'off the peg' availability. Dichloromethane is pretty much the most
aggressive of the 'off the peg' compounds when it comes to dissolving
organics, which is why it is first choice in paint stripping applications,
where cost and fumes are not an issue. This would have been my first
suggestion if I wasn't concerned that you might simply dissolve the thing
before you could get it out of the solution!

Pencil 'rubbers' seem to be silicone based these days, if the smeary mess
many of them leave on the paper is anything to go by. I'm afraid, I don't
know enough about these to know if they can be swelled, but, if this is what
you do have, then you ought to be able to mould a new piece as someone
suggested earlier. Sorry if my suggestions have delayed your 'final
solution'.

Cheers,
S