Author Topic: Gasket cement?  (Read 12701 times)

Offline JohnH

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Re: Gasket cement?
« Reply #30 on: 27.07. 2010 12:02 »
Just following up on a point that Adrian mentioned in this thread a while ago:

John mentioned Dowty washers a while back...
These are really good - a friend gave me 3 for the rocker feed oil pipes on my Velo about 10 years ago & they haven't leaked since.. I want to get some for the A10..
Are the sizes measured across the metal part or the rubber insert?  Anyone know what size I'd need for the 2 rocker feeds and the oil pipe feed/return outlets on the crankcases please?

Does anyone have any thoughts? I looked at the Dowty web presences and the concept of the Dowty washers look really sound .... but it looks as though it's probably very important to get a good seal to the bolt at the inner annulus to ensure that the seal is comprehensive.

John
Triumph Bonneville - long gone (sadly)
AJS 16MS - keeps coming back (thank goodness)
BSA B31 - also long gone
Greeves 250 twin (good fun)
Francis Barnett 197 (first bike)

Offline BSA_54A10

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Re: Gasket cement?
« Reply #31 on: 27.07. 2010 12:25 »
Quote
Thanks Groily re gasket paper - do you use a particular thickness most often?
you need a couple of different thickness.
Some places don't matter ( tappet covers for instance) while others the thickness is important ( gearbox inner )

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Trevor

Online bsa-bill

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Re: Gasket cement?
« Reply #32 on: 27.07. 2010 12:48 »
Talking of Dowty washers I'm unsure that we are all talking about the same thing
A Dowty washer as I understand them to be, is a solid steel washer with a rubber section bonded onto the internal circumference of the washer, the rubber section being thicker than the washer makes the seal.
There are also washers that consist of a thickish rubber washer surrounded around it's outer circumference and partly over both side with copper, these I think seal by squishing up the copper ( which the rubber allows )
Both types work fine but I think the first is a "Dowty" washer.

other opinions are available, and no doubt forthcoming  *smiley4*
All the best - Bill
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Offline JohnH

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Re: Gasket cement?
« Reply #33 on: 27.07. 2010 13:05 »
Sorry - I tried to post the attachment as a BMP file. Here it is as a JPG.

Apologies,
John
Triumph Bonneville - long gone (sadly)
AJS 16MS - keeps coming back (thank goodness)
BSA B31 - also long gone
Greeves 250 twin (good fun)
Francis Barnett 197 (first bike)

Offline Goldy

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Re: Gasket cement?
« Reply #34 on: 27.07. 2010 13:14 »
I think that the clear silicone takes some beating although I dont know about using normal houshold stuff. I use Granville instant gasket which is available from usual sources in the uk.           http://www.granville-oilchem.co.uk/product_info.php?prod_id=44
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Offline JohnH

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Re: Gasket cement?
« Reply #35 on: 27.07. 2010 14:59 »
I made a right fist of my last post. All I managed to get onto the board was the extract from the PDF File that I should have included the link for. Here's the link for the complete document:

http://potterassoc.com/PDF/o_rings/Bonded%20Seal%20Information%20and%20Sizing%20Chart.pdf

The extract I posted earlier is from it.

From what I've been able to glean, the Dowty seal is made at the inner annulus of the washer around the bolt. So in the case of the banjo feeds to the rockers, a Dowty washer would go on either side of the banjo and the seal would need to be a tight fit to the smooth surface of the bolt that screws into the ends of the rocker shafts. So I would read that the inner diameter of the washer would be pretty important and should be the same as the outer diameter of the rocker shaft (oil-feed) bolts - I have no idea what size they are though Adrian.

Thanks for the link on the sealant you use Goldy.

John
Triumph Bonneville - long gone (sadly)
AJS 16MS - keeps coming back (thank goodness)
BSA B31 - also long gone
Greeves 250 twin (good fun)
Francis Barnett 197 (first bike)

Online bsa-bill

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Re: Gasket cement?
« Reply #36 on: 27.07. 2010 17:08 »
Cheers John - that is what I recognise as a Dowty washer, used in lots of hydraulic joints and withstand thousands of pounds per SQ inch pressure, so petrol under gravity should be no problem or oil at 60 lbs/in.
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline brackenfel

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Re: Gasket cement?
« Reply #37 on: 27.07. 2010 18:48 »
Many thanks for the link John. These are the ones, the rubber is slightly thicker than the washer & forms a seal between the 2 surfaces when tightened up..

The same friend is going to lend me a few to try on the BSA.. He is an ex RR aero engineer & understands all about sizes etc so I'll report back if I find any useful ones..

Cheers,

Adrian.

PS Just to prove wisdom doesn't come with age I've just agreed to buy a B33 that hasn't run for 10 years..... *eek*
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Online groily

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Re: Gasket cement?
« Reply #38 on: 27.07. 2010 20:29 »
Missed your query re 'most frequently-used thickness' John - sorry. But, except for gearbox gaskets where a bit of thickness is often needed to maintain free play as already mentioned, I always try to go with the thinner stock from my shelf. But must confess to never having miked it. 8 to 10 thou maybe? Thicker doesn't mean better in my experience, in fact rather the opposite provided the surfaces are decent.
Agree 100% re dowty washers btw - excellent things which really do work (if I have the right size when I want one, which ain't always . . .)
Bill

Offline JohnH

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Re: Gasket cement?
« Reply #39 on: 27.07. 2010 23:03 »
No probs - Thanks Groily. I was intending to get a couple of thicknesses anyway - and several sheets - I know I'll mess some up!

Good luck with the B33 Adrian - that sounds like a labour of love. Do get back to the list if you manage to pin down the Dowty washer spec as I'd be really keen to try them out on my GF .... never did like fibre washers!

John
Triumph Bonneville - long gone (sadly)
AJS 16MS - keeps coming back (thank goodness)
BSA B31 - also long gone
Greeves 250 twin (good fun)
Francis Barnett 197 (first bike)

Offline cus

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Re: Gasket cement?
« Reply #40 on: 28.07. 2010 01:48 »
G'day Everyone,
Just on the silicone thing, use neautral cure silicone, without the acid. I think its been mentioned before by Brian.
I've been using it for years on exhaust headers & sometimes on one side of the gasket on the primary case, sticks
like s__t to a blanket! Usually comes under roof & gutter silicone (neautral cure).

regards, Cus
56 G/Flash project

Offline JohnH

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Re: Gasket cement?
« Reply #41 on: 16.08. 2010 17:06 »
A quick question for Lannis who was kind enough to post a suggestion that Copper-Cote sealer works well for sealing a solid copper head gasket.

Now I've searched pretty hard for Copper-Cote and keep coming up with roofing or anti-fouling products. I did find a Copper Coat gasket cement (CRC 401516 Copper-Coat Liquid at:
    http://hires.amazonwebstore.com/CRC-401516-CopperCoat-Liquid-with-Dauber/M/B000M8Q194.htm

but that doesn't look right as it seems to be designed for paper gaskets. Can you possibly point me at a supply source (preferably UK based) for the Copper-Cote that you use please?

Many thanks,
John
Triumph Bonneville - long gone (sadly)
AJS 16MS - keeps coming back (thank goodness)
BSA B31 - also long gone
Greeves 250 twin (good fun)
Francis Barnett 197 (first bike)

Offline muskrat

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Offline BSA_54A10

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Re: Gasket cement?
« Reply #43 on: 17.08. 2010 12:47 »
What Lannis is referring to is copper anti sieze grease.
You can get it from almost any good hardwear shop or nut & bolt shop or engineering supply store.
Three grades of anti-sieze commonly in stock are copper (normal use) Nickel ( extreamly high temperature ) and tefflon ( food  processing)

It is the came stuff that you should rub on your plugs before fitting them as well.
Take your big wallet in with you it ain't cheap but go for the big jar.
They try & flog you a 1 oz jar ( about the size of lip gel ) at 10 times the price per oz as the big jar.
Bike Beesa
Trevor

Offline Big Nick

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Re: Gasket cement?
« Reply #44 on: 17.08. 2010 17:55 »
clear bathroom sealant is good round the exhaust pipe /head junction
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