What is this mystery screw thread?

[Group Leader]

I'm trying to identfy a screw thread on a plastic hose connector which seems particularly strange. It's actually off an old Harry Moss air horn from the '70s and I need to make a replacement elbow rather than the straight connector seen here.

An M8 bolt sort of screws in but is a "P .... in a bucket" fit (an old engineering term ) such that over the available thread length it doesn't really bind up so the pitch is vaguely similar. It isn't 1/8 BSP; it's pitch is too coarse and it is too small in diameter.

I can't find any threads with a 65 degree angle or look anywhere close. The photo/sketch below shows it. The dimensions are a "rough guide" and the thread angle was determined from the photograph using my calibrated version of Powerpoint.

Any knowledgable suggestions would be gratefully received.

Cheers

Alan

Thread.jpg

[SPRIDDLER]

. What is this mystery screw thread? It's actually off an old Harry Moss air horn from the '70s

They probably used any old thread just for a hoot.

(Sorry Alan )

[Group Leader]

Boom boom!

[Mick D]

Hi

Could be a 3/8" thread, the plastic may well have shrunk over the years.

Don't think your guestimate of 65 degrees is correct - you seem to have used the centre of the root and the tip of the crest as reference points - you need to measure the actual angle, (the apex of which extends beyond the thread root).

Regards Mick

[Group Leader]

Hi
Don't think your guestimate of 65 degrees is correct - you seem to have used the centre of the root and the tip of the crest as reference points - you need to measure the actual angle, (the apex of which extends beyond the thread root).

After a re-count (much more exciting than an election) the numbers worked out to 59.7 - that's close enough to 60 degrees for me given the high quality image I used to measure it which is much more sensible.

Could it be an M9? Pitch and OD would seem to be right for that. Now to find one to check!

Thread data.JPG

[Rob Harknett]

I would just throw it away as junk, without giving it another thought. But then, I guess that means I would be doing the same thing as many did, with bits of our old bikes many years ago. Better just hang on to it, one day someone might want to restore it.
To add more theories to the thread changing angles etc. My garden hose froze solid last year. It had a multi jet nozzle trigger grip gun on it. When I next went to use it. Water leaked from every where. The trigger did not always lock/unlock, so much water escaped, nothing much came out the nozzles.

[Group Leader]

I would just throw it away as junk

Ah, but if I did that Rob the air from the old compressor would not get to the potentially life-saving air horn surreptitiously located under the seat of the even older AJ .....

Alan

[Rob Harknett]

I would just throw it away as junk

Ah, but if I did that Rob the air from the old compressor would not get to the potentially life-saving air horn surreptitiously located under the seat of the even older AJ .....

Alan

Life saving ??? I recall years ago Bill Redford having an air horn on his much famed G80. He unexpectedly came across me riding along a country lane and tagged on behind me. He gave me a blast on his air horn to draw my attention to him behind. Nearly frightened to Life out of me. I felt Jan jump up on the pillion.
I wonder if any of the Hozelock garden hose fittings would be the same, or perhaps fish pond aeration fittings. Offer a replacement part for you?
I recently brought an old tobacco tin full of inner tube valves, chrome valve dust caps, of the type that will remove the valve. Also two other fittings I have never seen before ( pictured ) both are fitted with valves, of the type found in inner tubes. The thread by the Red " X " is the same thread as an inner tube valve the dust cap screws onto. Thread with the Red X will screw into the other fitting. What were they used for??? Model air brush spray gun?? Air horn?? If you think you can use any of those fittings to make up a line from your compressor to air horn, you are welcome to what you may need. I only have 2 of the double threaded type. About 20 of the type that take a pipe one end. The internal valve screws into the Red X end and non pipe end of the other fitting. If you need to know airflow direction with the valves fitted.

SDC14813.JPG

[Group Leader]

The air horn will only be used to signal my presence (as if a bright yellow full face and yellow/black marked jacket weren't enough) to those road users waiting in side turnings until you approach on the main road and then they decide to pull out. I'm sure most will be familiar with such idiots .....

The air horn is an additional not a replacement audio signalling device and all such normal emissions will be via the original factory fitted job rather than the air horn.

Unfortunately the only sensible mounting place and orientation for the compressor mean that the red plastic pipe connector which is the subject of the thread emerges about 1/2" from the back of the oil tank hence I need a replacement elbow connection rather than straight. To find a ready made job would be too much to ask so, as long as I can find some suitable material with the correct thread on I can fabricate the rest.

I found on a push bike website an M9 Shroud Nut which looks like it might be useable so I'm off to the local push bike shop to see if they are fairly common. Of course, they look just like a car brake pipe fitting but unfortunately they are normally M10

Many thanks for the offer Rob, I'll see what I can come up with locally and if not I might come back to you!

Alan

M9 Nut.JPG

[Mick D]

Hi

Try Googling 'M9 barbed elbow' - that's the description of what your after I think.

Regards Mick