Theoben Rapid Forum

KevG Lathe work undertaken => kevG section => Topic started by: rapidave on May 18, 2026, 10:10:11 AM

Title: doctor bob quick fill
Post by: rapidave on May 18, 2026, 10:10:11 AM
hello Kev hope all is well what I would like to know is I have removed the o-ring bs007 from the MFR push pin replaced push pin back and nipped up the grub screw in to the bottle adaptor when I fit the quick fill air is escaping from the little hole where the grub screw which hold the push pin in place Hopefully you might have the answer to my question it does have one of your own reg fitted would that make any difference
Title: Re: doctor bob quick fill
Post by: angrybear on May 18, 2026, 11:55:40 AM
Change the BS804 under the push pin to stop it leaking from that grubscrew  ;)
Title: Re: doctor bob quick fill
Post by: rapidave on May 18, 2026, 12:08:44 PM
afternoon Angrybear
when you say change the BS804 o-ring do you mean with a new one or remove it totally
only asking as it is not a old one that's in the Bottle adaptor
Title: Re: doctor bob quick fill
Post by: Ca_Varminter on May 18, 2026, 02:37:36 PM
Quote from: rapidave on May 18, 2026, 10:10:11 AMwhen I fit the quick fill air is escaping from the little hole where the grub screw which hold the push pin in place
Dr Bob covered this problem many Moons ago....
His solution is to cut piece of O-ring
Insert the piece of O-ring into the hole before you screw in the grubscrew.
Then tighten down the grubscrw.
This will create a seal so air doesn't pass by the grubscrew!

Good Luck,
Stuart
Title: Re: doctor bob quick fill
Post by: rapidave on May 18, 2026, 03:51:54 PM
thank you Ca-Varminter for that info I will try that also would it be of any help if I was to use a mild thread lock on the grub screw as well
Title: Re: doctor bob quick fill
Post by: Ca_Varminter on May 18, 2026, 04:17:08 PM
Quote from: rapidave on May 18, 2026, 03:51:54 PMthank you Ca-Varminter for that info I will try that also would it be of any help if I was to use a mild thread lock on the grub screw as well
Yes...I use Loctite on the Valve-body locating screw on all my rapids!
Loctite will act like a thread sealant!

Atb, Stuart
Title: Re: doctor bob quick fill
Post by: rapidave on May 18, 2026, 04:22:33 PM
thank you Stuart for your info

many thank Dave
Title: Re: doctor bob quick fill
Post by: angrybear on May 19, 2026, 01:56:03 AM
Quote from: rapidave on May 18, 2026, 12:08:44 PMafternoon Angrybear
when you say change the BS804 o-ring do you mean with a new one or remove it totally
only asking as it is not a old one that's in the Bottle adaptor

Change it for a new one, BS007 seals the bottle valve but 804 stops the air leaking back past the push pin.

My personal experience is they must be replaced every time the push pin is disturbed, & more than once the new one has failed on fitting, they definately need a good smear of Molykote.
Title: Re: doctor bob quick fill
Post by: Ca_Varminter on May 19, 2026, 02:41:52 AM
Quote from: angrybear on May 19, 2026, 01:56:03 AMChange it for a new one, BS007 seals the bottle valve but 804 stops the air leaking back past the push pin.

Exactly....you only would need to replace the BS 804 if you have a problem with Reg Creep!!
This will not have any effect on air leaking out the threaded grubscrew hole!
(https://photos.imageevent.com/scl_electronics/gun/air/websize/reg-front-strip1.jpg)
What keeps air leaking pass is the push-pin O-ring BS 007...If he was using a MFR bottle!!

Since he is using Dr Bob's QF.. Now the "bottle " connection is sealed using a standard Valve Neck O-ring BS 111
This means the whole area where the push pin resides is Pressurized!
So that thread hole that locks the Push-Pin is now Exposed Bottle air pressure!
So It needs to be sealed.....

Stuart
Title: Re: doctor bob quick fill
Post by: rapidave on May 19, 2026, 06:20:43 AM
thank you Stuart for explaining it so clearly and the bit about reg creep


Dave
Title: Re: doctor bob quick fill
Post by: angrybear on May 19, 2026, 12:32:31 PM
Having never seen one of Dr Bobs for an MFR I can't argue,
But surely if it doesn't duplicate the MFR valve sealing around 007 and instead uses a std bottle 111 O ring seal, to pressurise the whole internal area, it would make far more sense to use a standard push pin & adaptor, to do away with that grubscrew hole completely, in fact it could only be beneficial.  ???  ???
Title: Re: doctor bob quick fill
Post by: Ca_Varminter on May 20, 2026, 05:49:15 PM
Well it depend how deep is your Pocket...
So it is not as EZ as not using the MFR depressing pin disk.
You Can Make a Standard Pin disk, but still have the Grub screw to deal with.
So this leave you having to get a standard MKII Reg,,,,,,,,

Stuart
Title: Re: doctor bob quick fill
Post by: angrybear on May 21, 2026, 12:41:10 PM
Not a matter of pockets just do a swap with someone  ;) I've got at least 1 spare reg adaptor with no grubscrew.

I believe I'm right in saying the grubscrew is a fail-safe to prevent any risk of 007 sticking to the bottle, causing the push pin to unscrew along with the bottle  :-\ so with a Bob QF there appears no reason to have 007 at all, in fact no reason to have an MFR push pin at all, as the pin is only there to seal the reg off the other side.
Title: Re: doctor bob quick fill
Post by: Ca_Varminter on May 21, 2026, 02:51:35 PM
No Reason.... Just avoiding  having to replace Costly item on your Rapid..

Stuart