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Here is the tips how to improve the Edwards vacuumpump against airleakage. :) I used the O-ring to keep tight between the body and cover then the pistonrod is tight against airleakage by glandbox. The brass collar with O-ring is adjustable in height to make a little play between vacuumpump body and cover before the cover bolts is screwed on place and the O-ring is pressed on cover to keep tight against airleakage. The red disc is soft teflon to keep tight against air leakage. See the movie when i tested the Edwards vacuum pump, it show the vacuum pump is air tight. :)

[ame="http://www.youtube.com/watch?v=tL6i8MAElMo"]http://www.youtube.com/watch?v=tL6i8MAElMo[/ame]

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Hello Everyone,
Just wondering were is a good source of gasket material it seems very hard to find 1/64" or less besides Stuart.
Any help will be Greatly Appreciated
Alec Ryals
 
Hi Alec,

I have been using virgin teflon sheet for many years with great results. It can be obtained in very thin sheets indeed.

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Assembles and disassembles beautifully and can be split open without replacement many many times. No sealant required at all.


John
 
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Forgot to add, just go onto ebay (or if in US, Amazon as well) and search for "Thin Virgin PTFE Teflon Sheet" and it should come up with whatever thickness you require for very little money.
You need the virgin bit as it also comes with many types of facing patterns on it, which is no use if you require it to seal.

Hope this helps

John
 
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There is a certain thin brown paper, very dense and smooth, that is/was
used, in the USA at least, for small flat bags such as those used in stationary
stores for cards and such. Small items were placed in them as 'carry' bags
for customers.

I have found that this paper makes excellent gasket material when oiled or
greased.

Pete
 
The thing with ANY paper or fibre based gasket material, in the sizes and thicknesses we use on these models, it is very weak, plus it tends to get the sealing qualities destroyed once the joint is split, in other words, it is rather fragile.
With virgin PTFE, no other materials are required to get a good seal on the joint, oil, grease or jointing compound, it just seals for life. Once you have cut the gasket, basically, if you don't damage it on assembly or subsequent disassembly, it will last the lifetime of the model.

Having upgraded many engines to this gasket material sent to me for repair, I can honestly say, it is the best thing I have ever used, to the stage I wouldn't use anything else.

This is part of a gasket set I made for a Marcher engine sent to me for repair after the customer told me it had paper gasket failure on the steam chests. Due to the very high temperatures in the engine room and near to the boiler, the paper material and it's coating had failed and bits of it were drawn into the steam chest, consequently wearing grooves in the port faces.
Who says paper won't cause damage?

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Port face on disassembly

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After it had basic cleaning, showing the scoring.

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The culprit, the oil soaked paper had hardened and turned into like pieces of a razor blade. Once it got in around the slide valve, the seal was doomed to failure.

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And the cure

marcher18.jpg


Once every gasket on the engine was replaced with PTFE, and I had shown him where to put heat shielding around his boiler, it ran perfectly, and as far as I know, no further problems have ever arisen.

The problem is that people won't take on the qualities of new materials, and continue to use outdated methods for making gaskets that have been used for the last couple of hundred years. Ok, it is a bit more expensive, but to me, is easier to make gaskets from, just a craft knife, compass cutter and a set of hole punches and you should get gaskets that never blow, leak or cause damage, basically, cut, fit and forget.

John
 
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Good grief John! I don't think anyone will argue against PTFE. But some
still want to know about paper. What can I say that you haven't already
said about PTFE??

Pete
 
Hi Pete,

All I was trying to do is to bring PTFE into the limelight against the 'old' methods.

Nothing wrong with the old stuff, it has worked well for a couple of hundred years, and I myself used to use greased or oiled paper and card on my steam and i/c engines, and found it lacking in all areas. I also used to work in an industry where we used to use super heated steam, and even those at the time were using 1/8" to 1/4" thick fibre gaskets, and they tended to fail rather regularly. Looking around now, they all seem to have gone over to this new material.

The main problem with modelling, we tend to scale things down, including gasket thicknesses, just to make things 'look right', but liquids, pressures, steam and heat don't scale down, they stay the same as full size, and that is why old style gaskets fail on our models, they are not strong enough materials.
40 years ago, the average model boiler ran at somewhere around 10 to 20 psi, nowadays, they tend to start at 30psi and go up to well over 100. So again, the old styles are being put under stronger pressure, not intended as a pun.

Sorry to have overloaded everyones senses about PTFE, but if a little of the info sticks in someones mind, I am doing my job correctly, as I have been doing for many years, and that is passing on information that is easily understood and informative as well, plus hopefully, may be of use to others.

John
 
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Don't stop what you're doing John. I just felt like you really took a run at
my post! We're too sensitive and we both know why.

Where did you get those 'cutting' calipers??

Pete
 
I wasn't taking a dig at you at all Pete, but anyway, it is called a compass cutter, and the very expensive ones are made by OLFA, but I purchased mine from a local market stall many years ago for around a pound (1.5 bucks). It came with about 5 spare blades of which I have at least half of them left. Cheapo ones should be available from ebay.

To get a really good cut, you don't use it as you maybe think it is used, that is sticking the centre pin in and doing the circle, it ends up all over the place.

I stick the pin and a tiny bit of the cutter tip through the material into the cutting mat or soft wooden board, and then drag the material gently past the cutting tip. It cuts perfect circles every time doing it like that, and the scale marked on the side gives perfect sizes.

Hope this helps

John
 
Charles,

I use 0.002" for precision lapped or ground faces or 0.005" for general purpose work, sometimes I would use thicker if I was replacing old card gaskets to retain correct alignments, but for head gasket material on i/c engines, I used 0.010" or 0.015", the difference was to allow adjustment for compression ratios.

Throw nothing away as you can use most of the offcuts for making tiny gaskets. I am still using bits and pieces of 12" square sheets I bought over 10 years ago.

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John
 
I took the film one month before I mounted vacuum pump and water pump. This was the test run and checked that everything would be fine. :)

http://www.youtube.com/watch?v=1xhXqMLKHeQ

Tried to watch vid but all I get on my screen is a black square; is there something I have missed ? I use IE11, Win 8.1

George

p.s. the link shows up on my reply... see above... clicked on... plays ok.
 
Teflon sheet seems to be the gasket ticket it comes in all thicknesses from mcmaster-carr
 

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