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Question on Filter Chamber Size

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Crown Duke

Joined: 19 Mar 2014
Posts: 290

Location: Long Island (USA)

PostPosted: Mon Apr 21, 2014 10:03 pm    Post subject: Question on Filter Chamber Size  Reply with quote

Question for the Grabow gurus ...

After having obtained a lovely Royalton from Sean recently, I immediately noticed an odd difference (with regards to filter chamber size) when compared with my 16+ yr old Freehand.

Both take the standard Grabow 6mm paper filters, but with filters inserted the Freehand has a tight draw (perhaps a little too tight in fact), while the Royalton has a loose draw.

At first I suspected a slightly wider diameter air channel was drilled in the Royalton (connecting the back of the filter chamber in the rear of the mortise to the base of the bowl), but extended smoking and subsequent cleanings of both pipes revealed something else as the more likely cause ... it looks like the filter chamber of the Royalton are decidedly longer (and perhaps very slightly wider) than in the Freehand. This is evidenced by the fact that new filters inserted into the Royalton actually rattle back in forth (end to end) in their chamber until mid smoke (by which they've absorbed enough moisture to stop moving as freely), and upon removal it is very apparent that while the freehand is filtering effectively, a significant fraction of the draw in the Royalton goes AROUND, rather than through, the 6mm paper filter.

Thus my question: if both pipes are nominally Spec'd to use the same 6mm filter, why the unannounced change in filter chamber size in the Royalton to one that allows significant bypass leakage ?

Am I missing something ? Was the Royalton misdrilled (belated gesundheit, BTW), or does it take a different size/type filter than the 6mm paper standard ?

Photos provided upon request.
ΦBK "Philosophia Biou Kybernetes" {love of learning is the guide of life.}
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ozark southpaw
Golden Duke

Joined: 08 Jul 2008
Posts: 9443

Location: Poplar Bluff,Mo.

PostPosted: Tue Apr 22, 2014 12:27 am    Post subject: Reply with quote

I have noticed some variation in the depth that both stems and bowls are drilled for the filter. Most often,it seems to me the stem drilling is not quite deep enough,which will when the stem is shoved all the way in cause restriction-the end of the filter gets crimped a little.  
The machine that does the shank drilling is a round turntable type thing and variances in setup or wear to the drill bits could account for for some difference in depth. That doesn't happen very often from what I have seen.

The stems are not drilled at the Grabow factory-their supplier does that.

There is no other size filter for a Grabow.


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