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Hose/Fittings questions

MikeC5 on Sat August 29, 2009 5:44 PM User is offlineView users profile

What is the typical amount of interference (if any) between a bead-lock fitting and hose ID when you assemble them?

I ask because I just started cutting away and removing the original ferrules on my 85 vintage German car and was a bit surprised at what I found. First, the ferrules have hose barbs on the inside (to grip the hose OD) and they seem to be of cast material rather than sheet metal as they break apart more than bend. Second, I cut through the hose well away from the fitting to check the hose ID and found it was about 40 thou larger than OD on the fitting barbs. I suppose the hose may have swelled over time? I can find specs for nominal hose ID for #6, #8, etc. barrier hose but not on the OD of bead-locks (or any other kind) of fitting.

For example, a #6 hose has an ID of 5/16 (0.312) diameter and the fitting barb I mentioned above measures 0.330 at OD of barbs. Is this enough interference? I'm trying to determine if I can put new hose on my old fittings (and I plan to smooth down the edges on the R-12 barbs too).

Cussboy on Sat August 29, 2009 7:34 PM User is offline

I had my AC line repaired once by a knowlegable AC pro, was leaking at a crimp. This was also a metric (Japanese-made) vehicle with R-12.

The tech told me that the original barbs couldn't be re-used as they would leak with a manual crimp, so he welded on a new barb which did have larger and different-design barbs. Then he re-made the crimp, and it's still holding fine, years later, still R-12.

MikeC5 on Sun August 30, 2009 9:56 AM User is offlineView users profile

bump. Can anyone answer this question please? "What is the typical amount of interference (if any) between a bead-lock fitting and hose ID when you assemble them?"

HECAT on Sun August 30, 2009 11:09 AM User is offline

Typical specifications such as you ask for are not available. Specifics may be available from the hose, fitting, or vehicle OE. Keep in mind that such specifics from a hose manufacturer would be in regard to only their hose, fittings, ferrules, and crimp specifications. Mixing, fixing, welding, and reusing fittings is not something (for liability reasons) the manufacturers will publicly support. Making hoses sometimes requires a considerable learning curve with some trial and error along the way. It is normal for the insert to be a little undersized to allow for easy insertion. The "teeth' on the barb and inside the ferrule are part of the designed retaining system; grinding them down changes the game for the better or the worse (who knows).

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MikeC5 on Sun August 30, 2009 12:50 PM User is offlineView users profile

I'm looking for a ballpark number is all. If I buy beadlock fittings from ACkits and the corresponding barrier hose what is the interference fit? I know the hose ID is nominally 5/16 for a #6. Can anyone tell me what the beadlock fitting OD is at the beads or otherwise? As for modifying barbs, I'm looking at this thread:
http://www.autoacforum.com/messageview.cfm?catid=20&threadid=14922

mk378 on Sun August 30, 2009 1:15 PM User is offline

Barrier hose must be retained by a captive ferrule on the OD. If it only has barbs on the ID it will slip apart at the barrier layer. Those ferrules crush down so hard that I don't think the initial fit on the ID is that important.

MikeC5 on Sun August 30, 2009 4:41 PM User is offlineView users profile

I still plan to use replacement ferrules. I didn't mean to rely on the barbs only.

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