jackal
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| posted on 21/11/07 at 04:55 PM |
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Brake fitting sealing- brake light pressure switch.?
Right, i'm currently constructing the brake system on my stm locost. In the front circuit there is an m10x1 4-way union (front wheels, master
cyl. and brake light pressure switch), the male fittings from the two front wheels and master cyl. will seal correctly in the 4-way because of the
convex/concave faces, the one that worries me is the brake light pressure switch as it is a male tapered thread (and no convex face) going into a
parrallel female thread in the 4-way union, surely this can't seal suffciently for a braking system, shouldn't the female thread in the
4-way be tapered as well...? What pressure switch/4-way union combination has everyone else used..?
Cheers.
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stevec
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| posted on 21/11/07 at 05:03 PM |
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It will be fine, The taper will seal the thread.
Steve.
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tks
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| posted on 21/11/07 at 05:08 PM |
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i thought that my part was called
3way + brake switch.
sow it has a special hole (incl. thread) in the middle and 2 outlets on the sides and one entrance in the middle.
Tks
The above comments are always meant to be from the above persons perspective.
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jackal
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| posted on 21/11/07 at 05:18 PM |
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quote:
Originally posted by stevec
It will be fine, The taper will seal the thread.
Steve.
I would say it was a bit of a bodge really, tapered thread sealing relies on the two tapers tightening into each other across their length, where as
if a male taper goes into a female parrallel then it will only seal right at the base of the male thread...? Also my pressure switch looks like it
will bottom out if i tighten it properly....
cheers.
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jackal
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| posted on 21/11/07 at 05:20 PM |
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quote:
Originally posted by tks
i thought that my part was called
3way + brake switch.
sow it has a special hole (incl. thread) in the middle and 2 outlets on the sides and one entrance in the middle.
Tks
Not sure bout that one, i'm sure mine is a 4-way m10x1 (i.e. parrallel thread)... Where did you get it from?
Cheers.
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twybrow
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| posted on 21/11/07 at 05:44 PM |
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That is what I have - 4 way M10, and the sensor has a tapered thread. No leaks from that part so far (leaks most other places!). You can also get a
compound to apply that helps the seal (I dont think PTFE is advisable). Try it and see, if it leaks, nip it up a bit tighter. If it still leaks, look
for another solution.
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NeilP
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| posted on 21/11/07 at 05:57 PM |
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Put a suitable no. of copper washers in to stop it bottoming out and provide another seal...
If you pay peanuts...
Mentale, yar? Yar, mentale!
Drive it like you stole it!
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jackal
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| posted on 21/11/07 at 05:59 PM |
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yeh i was going to try it but i'd prefer to get it right in the first place... Anyone used a pressure switch with a convex end fitting or 4-way
with a tapered thread for the switch...? or any other ideas...?
cheers
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tks
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| posted on 21/11/07 at 06:23 PM |
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make a pic of yourse
/ look at suppliers sites wich you have and wich they also sell,
i'm quite sure there are wrong ones out there
Tks
The above comments are always meant to be from the above persons perspective.
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BenB
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| posted on 21/11/07 at 06:26 PM |
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We've done this one before re suitability of ptfe tape and bodged non-similar threads in the brake circuit. Whilst it's possible and can
work, the concern is re weeping brake fluid loss resulting in a distinct lack of breaking.... In fact, I recall it getting quite heated 
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tks
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| posted on 21/11/07 at 06:33 PM |
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okey i looked at merlin motorsport.
there are 2 types M10x1 or UNF
the switches exist also in 2 types sow make your own conclusion.
Tks
p.d. my switch was deliverd incl. a copper/blue grommet thing..
The above comments are always meant to be from the above persons perspective.
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jackal
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| posted on 21/11/07 at 06:37 PM |
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quote:
Originally posted by BenB
We've done this one before re suitability of ptfe tape and bodged non-similar threads in the brake circuit. Whilst it's possible and can
work, the concern is re weeping brake fluid loss resulting in a distinct lack of breaking.... In fact, I recall it getting quite heated
Well the way i look at it there should be no need for sealant/ ptfe tape as the fittings should make the seal, eg convex/concave face, tapered
male/female, paralell thread with copper washer either side (as long as the faces are suitable), a mixing of any of these types of sealing won't
seal in the way designed surely...? or am i just wrong/being too picky..?
So has anyone fitted a brake pressure switch without putting a tapered thread into a parallel one....?
cheers.
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tks
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| posted on 21/11/07 at 07:26 PM |
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quote:
Originally posted by jackal
quote:
Originally posted by BenB
We've done this one before re suitability of ptfe tape and bodged non-similar threads in the brake circuit. Whilst it's possible and can
work, the concern is re weeping brake fluid loss resulting in a distinct lack of breaking.... In fact, I recall it getting quite heated
Well the way i look at it there should be no need for sealant/ ptfe tape as the fittings should make the seal, eg convex/concave face, tapered
male/female, paralell thread with copper washer either side (as long as the faces are suitable), a mixing of any of these types of sealing won't
seal in the way designed surely...? or am i just wrong/being too picky..?
So has anyone fitted a brake pressure switch without putting a tapered thread into a parallel one....?
cheers.
???
this sounds for me that you have 10x1 on the 4-way thing and UNF on the switch..
test the switch with a 10x1 nut
(like the Sierra diff bolts/nuts)
you could try a sierra diff bolt in the 4way hub to test if that works your switch is deff UNF
Tks
The above comments are always meant to be from the above persons perspective.
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dhutch
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| posted on 21/11/07 at 11:00 PM |
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Its not unheard of in the steam-engine world to run tapored male bsp threads into parallel bsp female threads. Making the seal with the threads and a
turn of ptfe.
- Many parts are cut with a tapored thread and no facing flange, and a lot of boilers/manifolds are cut with parallel threads.
However at the same time, its obvously not recomended pratice. And certainly if your finding that the tapored is running out before it its tightening
up, that doesnt sound at all good to me!
Daniel
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_Aero_
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| posted on 21/11/07 at 11:01 PM |
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quote:
Originally posted by jackal
quote:
Originally posted by stevec
It will be fine, The taper will seal the thread.
Steve.
I would say it was a bit of a bodge really, tapered thread sealing relies on the two tapers tightening into each other across their length, where as
if a male taper goes into a female parrallel then it will only seal right at the base of the male thread...? Also my pressure switch looks like it
will bottom out if i tighten it properly....
cheers.
Jackal - as a couplings manufacturer specialising in fluid and gas fittings some years ago - it is intentional for parallel female and tapered male to
mate. They both deform slightly to give a better seal than tapered to tapered or paralled to parallel, without using some sort of sealing medium.
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iank
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| posted on 22/11/07 at 12:04 AM |
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quote:
Originally posted by twybrow
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You can also get a compound to apply that helps the seal (I dont think PTFE is advisable).
...
Frost sell the sealing compound, not cheap and no idea if it makes any real difference.
http://www.frost.co.uk/item_Detail.asp?productID=8874
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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RazMan
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| posted on 22/11/07 at 08:04 AM |
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I always put a drop of Loctite Threadseal on anything with pressure behind it - never PTFE.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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