Original:

Lathe Setup

On one side of the lathe chuck up 140mm tubing this will be the top of the funnel. On the other side the main body of the funnel.

Preparation of the Body

Cut off the necks of both the 3 liter and 4 liter flasks. Then seal out the 4 liter flask with 51mm tubing, and seal out the
3 liter flask 35mm tubing. The reason for doing this is we ran into a problem packing the 3 liter flask into the 4 liter with the standard Erlenmeyer blank necks. This should give even spacing for the dewar seal.

Once flasks are sealed out ,bottoms of the flasks are scored and cracked off roughly one inch from the bottom of the flask. Prior to packing the body for the dewar seal insert a cork into the 35mm tube of the inner section. This will allow you to blow only on the outer jacket while performing the dewar seal. Using two lengths of woven glass tape sixteen inches long in four layers lengthwise in a criss cross pattern over the top of the corked 35mm tube on the 3 liter flask this will give you approximately seven inches of glass tape down each side of the 35mm tubing. Then insert the 3 liter flask into the 4 liter flask.

Edited:

Lathe Setup

Chuck up 140mm tubing on one side of the lathe—this will be the top of the funnel. The other side will be the main body of the funnel.

Preparation

  1. Cut off the necks of both the 3-liter and 4-liter flasks.
  2. Seal out the 4-liter flask with 51mm tubing.
  3. Seal out the 3-liter flask with 35mm tubing (this should give even spacing for the Dewar seal—standard Erlenmeyer blank necks were problematic).
  4. Score and roughly crack off approximately one inch of the flask bottoms.
  5. Insert a cork into the 35mm tube of the inner section (this allows you to blow only on the outer jacket while performing the Dewar seal).
  6. Pack the body for the Dewar seal.
  7. Use two lengths of woven glass to tape four layers of sixteen inches, lengthwise, in a criss-cross pattern over the top of the corked 35mm tube on the 3-liter flask (this will leave approximately seven inches of glass tape down each side of the 35mm tubing).
  8. Insert the 3-liter flask into the 4-liter flask.