Reference · How-tos · Guns

Lowering the gun in the port by setting the axletrees deeper

Put a trial gun in the port, and set the axletrees deeper into the gun carriage so that the barrel sits at the right height in the port.

The barrel after lowering: the top sits at about half the height of the port.
The barrel after lowering: the top sits at about half the height of the port.

What you need

materials and suppliers

  • gun carriage and barrel of an 18-pounder from the kit

Dimensions

  • gun carriage 1.5 mm lower
  • top of the barrel at half the port height (centre line one third above the sill)
  • port size 14 x 16 mm
Time
an evening
Difficulty
moderate
When in the build
Phase 3,
From the log post
The gun carriage a millimetre and a half lower · forum

Before you start

The gunports have been cut. Do this check before you glue the linings into the ports, because linings make the port smaller.

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  1. Assemble one gun with its carriage and place it on the gun deck behind a port. Do this early: you see at once whether the barrel comes out at the right height.

    The trial gun on the gun deck.
    The trial gun on the gun deck.

    Tip from Johan Verschuren: I assembled one gun and then decided to raise the openings slightly, with a line parallel to the deck. The barrel now comes out through the opening just off centre.

  2. Look from the side and from above at how the barrel sits in the port. Ours came out too high; only at the aftermost port was it right: the upper deck sits up to 4 mm higher there than amidships. With linings in the port the gun amidships didn't fit at all.

    Amidships the barrel comes out too high in the port.
    Amidships the barrel comes out too high in the port.

    Tip from pietsan: The sheer must be the same for both decks. It's not too bad: you can adjust the barrels later with the quoin, so that they sit centrally in the ports everywhere.

    Watch out: We should have measured this height difference between the decks before fitting the gun deck and corrected it with a strip on the bulkheads. Now it can't be fixed any more.

  3. The holes for the trunnions are not in the centre of the barrel. Turn the barrel over and it sits just a little lower. Every little helps; for us it suddenly fitted because of this.

    After turning the barrel over the gun fits in the port.
    After turning the barrel over the gun fits in the port.

    Tip from Johan Verschuren: Just like mine, the holes through the gun are not in the centre. If you turn it over it sits just a little lower.

  4. Set the axletrees a little deeper into the gun carriage. That drops the whole carriage, in our case by 1.5 mm. This is neater than adjusting the barrel up or down, because the angle of the barrel stays the same.

    1.5 mm lower

    The gun carriage with the axletrees set deeper.
    The gun carriage with the axletrees set deeper.

  5. Put the gun back and check that the top of the barrel comes out at about half the height of the port; the centre line of the barrel is then a third above the sill. That way the gun can fire both high (at rigging) and low (at the waterline).

    The barrel now sits lower in the port.
    The barrel now sits lower in the port.

    Tip from paulbo: Ideally the centre line of the barrel should sit one third up from the bottom edge of the port, in other words the top of the barrel at half the gunport height.

  6. If necessary, adjust a little more with the quoin under the barrel. Do that sparingly, otherwise the barrels end up at very different angles.

    The quoin under the breech, here on a later scratch-built carriage: that wedge sets the last millimetres of height.
    The quoin under the breech, here on a later scratch-built carriage: that wedge sets the last millimetres of height.

Result

With 1.5 mm of lowering the barrel sat at the right height; Piet and Hans reckoned there was little more to do. On a next model we will measure the sheer of both decks before the gun deck goes in.

Problems met with this technique

2018-01-02

Aft, the upper deck sits up to 4 mm too high relative to the ports; with the port linings in, the gun amidships no longer fits in the port. The gun turned out to fit when turned round (the hole is off-centre); set the axletrees deeper into the carriage so it drops 1.5 mm; the top of the barrel at half the port height is right. (Tips from Pingu57, pietsan, Johan Verschuren, paulbo) to the register

In the same series: Guns

  1. Lowering the gun in the port by setting the axletrees deeper
  2. Blackening brass gun barrels with blackening solution
  3. Detailing a kit gun carriage with bolts, linchpins, quoin handle and breeching ring
  4. Turning the quoin handle from a satay skewer
  5. Milling gun carriages for the 9-pounders on the cross-slide table
  6. Making washers and linchpins from brass pin heads
  7. Carronades: trucks from brass tube and a working elevating screw

All how-tos · Guns, carriages and carronades in scale