Valve core details.. 1

[sbrats]

Hello,
I'm playing in the garage (again) fixing some air equipment related to air fittings on my car and bicycle(s) wheels. I'm looking at using a presta valve core (normally used on cycle tires)in a housing.
Is there a specification somewhere for the threads and such (housing and sealing edge details) of the valve core body so that I can drill & tap a housing to accept a presta valve core.
I have spent some time "on google" but haven't really found something that is definitive.

Or a pointer to a spec.

Thanks

Stephen

 

[CapriRacer]

First, I am assuming that a pesta valve complies with the normal valve core standards - and according to The Tire and Rim Association, all cycle valves are Valve Core Chamber No. 1 configuration.

It would be wise to do a reality check to make sure that what is attached is indeed what you are looking for.

 

[sbrats]

CR..
Thank you - yes indeed this is the information that I'm looking for. I'll 'cut open' a presta valve stem and compare best I can (sanity check!!)

The Tire and Rim Association 'book' is it available to non-members? (even an old one)

Stephen

 

[Tmoose]

why ?

 

[GregLocock]

Yes it is.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[CapriRacer]

To expand on what Greg wrote:

TRA issues yearbooks every year - usually about February. If you have a need for such a book, it's best to get the current copy. Unfortunately, they are expensive. I just looked it up, and they are $100.00!!

The good news is that the standards don't change from year to year. The updates are adding or dropping sizes and tables. So if you can find an old copy - and it has what you are looking for, then you can be pretty sure, the current book doesn't contradict the old one.

The bad news is that finding an old copy almost requires you have contact with someone who has need for the book in the first place. Obviously some of us have copies. (You should have noticed that the page I scanned was from a 2007 book.) I do have extra copies and I am willing to send one out.

HOWEVER, my opinion is that if you don't have a need for such a book on a regular basis, having one has very little value. It would be better to contact someone who has an up to date version - when you need it. If your need is on the order of once a year, I can't see having one. Besides, there are bits and pieces of the book available on the Internet (albeit in different formats). Most of what you'll need can be found using a search engine.

 

[sbrats]

Thank you..

Re the TRA book - valid points - leads me to the next couple of lines.

CR I briefly looked at the copy of the core configuration dimensions and started to compare these to a presta valve core. I thing (underline think) that everything lines up at first glance.


Then I measured a valve core and noticed a couple of things.

TRA shows a thread of .210-32 - the core measures .180 OD (over the threads) and it appears something other than 32 pitch (metric?) the dia of the body is .162 (sample of one BTW) so maybe its a less than full thread 10-32?

So unless there is a specification somewhere for presta valves - if I can get round to it I'll cut open a presta inner tube and use an eye loop and thread gages and compare. I can also play with a 10-32 tap and some aluminum and see what happens before I look for a .210-32 tap - (or mod a #12-32)

Stephen

 

[Tmoose]

Is there a sealing feature at the end of the core?

the white tapered plastic section here -

http://www.bobs-bicycles.com/images/P/Presta Valve Core.jpg

 

[sbrats]

TMoose..

Yes, the image is correct. The white feature, I believe, sits on the taper cut in the chamber (ref to the image that CR provided)or at the very least maybe 'jams' against the edge created by the taper and the 'smaller' diameter of the bore in the body.
The threads that I measured are just to the left of the 'white' section in the image that you provided - 6 (six) threads. As I described they measure .180" OD (over the thread) and I looked at it last night with an eye loop and thread gauge (using the tips of the threads on the thread gauge held next to the threads on the body - because less than full thread) it appears the pitch is 0.6 (mm) or 40 pitch so different than the 0.210-32 noted in the specification. But I should look again and on others that I have around the garage.. maybe I have a 'weird' one

I have yet to take a tube and 'cut' one open...

Stephen

 

[CapriRacer]

sbrats,

First, is there any reason not to use a shrader valve? You can get these on brass stems - which would be suitable for splicing in to air lines - either but soldering or creating threads.

Also, do you have the ability to measure metric threads?

I did a search on both TRA and ETRTO (the European equivalent) and don't see anything as small as you reported. That makes me think that Pesta isn't following these standards - which is OK, but may mean there isn't anything published on what the dimensions are.

 

[sbrats]

CR..
At this point there is no reason why not to use a shrader valve, and I will change and use one for the ease of what I'm doing.
It has now become a bit of a 'how can something widely used' not be defined - and being detailed oriented I'd like to see it through.

Any other help or suggestions are welcome.

Stephen

 

[CapriRacer]

sbrats,

Defined? I'll bet it is defined - BUT - it is peculiar to the manufacturer. Let me give you an example.

Nut and bolt threads are "defined", but there are plenty of non-standard threads. Off the top of my head: There are NST (National Srandard Threads), NSP (Natioal Standard Pipe threads), BSP (British Standard Pipe threads) and metric (and I'm thinking those are DIN - which is German for the standardizing organization)

- BUT -

There is no law that these sorts of things have to be built to standard. I've encountered screws that were non-standard. Even tires are sometimes built to non-standard size - that is, a 205/55R16 could be built taller and narrower, but still labeled as though it is built to the dimensions indicated.

It's just one of those wondeful things that drive us engineers crazy!