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 Post subject: Custom Seal Tutorial
PostPosted: Sun Aug 24, 2014 10:00 am 

Joined: Tue Aug 20, 2013 8:56 am
Posts: 1079
Location: Calgary, Alberta
I have seen many posts regarding seal problems, so I thought I would share a method that I have been using to date. I have done this to modify seals to my 2240, QBXX, scuba tank and regulators.

My product of choice is; Alumilite Flex 80. This is a two part urethane rubber with a shore hardness (durometer) of 80. Full cure ranges from 8 to 24 hours depending on relative humidity and room temperature. Alumilite products can be typically found in hobby stores. I get mine from PM Hobby Crafts here in Calgary. Smooth On also carries a line of urethane rubber compounds, but the Alumilite is cheaper and the only one with a durometer of 80, which is recommended for high pressure applications.

I'm going to use a CO2 (seal) pistol as an example. I have read that it is difficult to find certain seals for certain models. Here is your solution.

You will need: Flex 80, high quality spray release, q-tip, toothpick and expended CO2 cartridge.

Prep the pistol. Remove the old seal and completely clean the seat. Spray a little release onto a q-tip and coat the seat. Flex 80 is a good product, but nothing is forever and this will make it easy to remove should it wear out. Next, using a scotch-brite pad or steel wool, polish the end of the used cartridge. This will remove any burrs and create a mirror finish to the new seal. The smoother, the better the seal. Now coat the end of the cartridge with the release agent and let dry.
Once all the prep work is done, you have to determine the final seat depth. Insert the cartridge into the chassis and push it in as far as it will go. Put a piece of masking tape across the chassis and cartridge. Cut the tape down the space between the cartridge and chassis. This is your reference mark to the deepest point of insertion. Remove the cartridge.
Now the fun part. Mix up a small amount of Flex 80. Simple, 1:1 ratio. Your pot time (life of product before becoming too hard to work with) is about 10 minutes, again, depending on humidity and temperature.
While performing the next step, it's important to keep "displacement" in mind. Using the toothpick, dribble the Flex 80 into the seat. Be careful not to fill to the rim as it will overflow when you re-insert the cartridge. You don't want this stuff to run into the gun and potentially gum up the parts (you also pack toilet paper or cotton into the cavity beside the seat to catch any over-run should it happen). Also, be VERY careful not to dribble any into the piercing probe. You could insert a sewing needle into this to ensure no product enters the probe. Once the rubber has flowed into the seat and is at the proper level by your best guess (may take a couple of tries) it's time to re-insert the cartridge. The important part here is NOT to insert the cartridge all the way to your original reference mark. You want to stop about 1-1.5 mm short of it. Even if it means moving the tape on the chassis to use as a new mating mark. Once the cartridge is inserted, tape it in place and secure the pistol so that the cartridge is vertical (plumb) until the rubber has cured (leave for 24 hours just to be safe).
Once cured, the cartridge should pop out easily, and you're ready for a new one.
If your new seal leaks, chances are, you displaced too much product when inserting the cartridge. Simply dig out the new seal with a dental pick and start over. On the other hand, you may get lucky on the first try. Just remember, DON'T OVERFILL.

If you want to create custom seals for other applications, PM me and I will be glad to walk you through it.

The flaw with experience is, it causes us to forget what we were like when we didn't have any.

 Post subject: Re: Custom Seal Tutorial
PostPosted: Sun Aug 24, 2014 11:21 am 
User avatar

Joined: Sun May 20, 2007 10:26 pm
Posts: 324
Location: Any Town ONTARIO
Could you post some pics of your methodology ?

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