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From: Jeff Liebermann <jeffl@cruzio.com>
Newsgroups: rec.bicycles.tech
Subject: Re: Two stage tire pump?
Date: Sat, 10 May 2025 09:09:54 -0700
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On Sat, 10 May 2025 15:22:38 -0000 (UTC), bp@www.zefox.net wrote:

>I do have an old "WindPipe", from Specialized. This is two-mode,
>not two-stage. It uses a very small-bore cylinder for high pressures
>and a co-axial large-bore cylinder for low pressure. The internal seals
>gave up and it no longer develops any pressure at all. Far as I can 
>tell they're no longer offered. It was helpful while it worked, but
>being single-stage the volumetric efficiency was always lousy.

Rebuild kit:
<https://www.certini.co.uk/accessories/pumps/specialized-windpipe-rebuild-kit--silverblack__45392>

Offhand, it looks like the seals are o-rings.  Measure your existing
o-rings and find substitutes.
<https://www.harborfreight.com/search?q=o-rings>
<https://www.ebay.com/itm/372061728115>
<https://www.ebay.com/itm/372621207595>

There might be a leather "cup" valve inside.  
<https://www.pyramydair.com/blog/2007/12/how-to-make-a-leather-piston-seal/>

If you want an air pump with really high pressure, look into air gun
pumps, which typically operate between 100 and 200 psi but can go much
higher.
<https://www.airgundepot.com/vault/articles/how-much-psi-can-a-hand-pump-produce/>

4 stages perhaps?
<https://www.amazon.com/NDCYJG-Pressure-4500Psi-Filling-Stirrup/dp/B0CGF988MN>
"Today’s hand pumps can hit 4500 psi."

Try a conventional single stage bicycle pump to get to around 100 psi,
and then use a two or more stage air rifle pump to go higher.  Trying
to pump to high pressures from atmospheric pressure involves too many
low volume hand pump strokes.

Another problem with high pressure air rifle pumps is heating:
<https://en.wikipedia.org/wiki/Boyle%27s_law>
The usual method is to pump a little, wait for the pump to cool down,
and continue.  I also suggest that you carefully monitor the air
pressure to prevent your tire and valve stem from achieving escape
velocity.

No warranty expressed or implied on my advice.


-- 
Jeff Liebermann                 jeffl@cruzio.com
PO Box 272      http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann      AE6KS    831-336-2558