SPICA TA REPAIR DO IT YOURSELF

This is a description for repairing the Spica TA with special thanks to Wim Neijenhuis, who did most of the technical thinking and practice.

The advantage of the adjusting screw is:

1) Easy to adjust after repairing the TA

2) The possibility of re-adjusting in case of a minor leak in the system.

Materials used:

1) Copper tube (for sleeves) Ø 4x1mm price: ¤ 0.60

2) 3-way T-coupling 4mm with compression fitting

price: ¤ 3.90

3) Compression chamber with adjusting screw

price: ? It was home made by a friend as a

favour.

4) Brake fluid

5) Syringe with needle

6) Metal saw

7) Small gas-burner/torch

Repairing the TA:

Cut the capillary tube of the TA about 50mm from the beginning (from the plunger end).

Clean the tube ends using fine sandpaper so that you can make a good solder joint.

Cut two 23mm copper tubes which you will use as sleeves. The diameter of the sleeves has to be enlarged using a 2mm bore.

Slide the sleeves over the capillary ends, letting 7mm of the capillary stick out (this is to prevent the solder flowing in and obstructing the capillary).

Solder the sleeves to the capillary and cut off the 7mm of the capillary that sticks out.

Put the expansion bulb in warm water till fluid comes out of the capillary (to make sure there is no air left in the tube) Then put the bulb in cold water while constantly filling it with a syringe filled with brake fluid.

Connect the end of the capillary from the expansion bulb to the 3-way T-coupling.

Fill the T-coupling with brake fluid using the syringe.

Connect the compression chamber to the T-coupling and fill with brake fluid.

Turn in the adjusting screw in the compression-chamber, holding the open end of the T-coupling upwards till fluid comes out..

Fill the capillary connected to the piston housing using the syringe and connect to the T-coupling.

Now all components are filled with brake fluid and connected.

Adjusting the TA:

For the adjustment of the TA we used the diagram on Bruce's website.

We worked in a room at 19.9º C, so according to the diagram the extension of the piston has to be 23mm.

The only thing to do now is to turn in the adjusting screw until the extension of the plunger is 23mm.

Finally we checked the max. extension of the plunger in boiling water. It was 31mm.

And also the extensions at intermediate temperatures were exactly according to the diagram.