The Tamiya recoil unit can be modified to be simpler, smaller and to give very fast recoil and slower barrel return. This is possible because of a quirk in the Tamiya recoil circuit (see sketch).
See the pics:
Pull the motor from the Tamiya recoil unit. Carefully pull the worm gear off the shaft without pulling on the shaft (press the shaft out of the gear vs pulling on the motor body). Add two small discs to the shaft to make a “winch drum”. Add heavy nylon line as shown. Modify the original support arm as shown and mount the motor to it with hot glue and a zip-tie (I use hot glue a lot). Tie the string to the barrel.
Your particular barrel setup, recoil length, etc. will determine the details here – experimenting will be necessary. When the recoil setup is done, add bungee as shown to return the barrel. The bungee needs to be set up to pull the barrel back fully to normal position, but not so tight as to prevent the motor/winder to pull the full recoil. Bungee is adjustable (unlike springs) so this step isn’t as hard as it seems. Note that a long run of bungee is needed for stretch capacity. See the bungee path in the pic. Again, some experimentation with each individual model will be necessary.
Advantages:
- Much smaller and lighter than original unit
- Simple
- VERY fast recoil, slow return
- Eliminates one wire (blue wire no longer needed) between turret and hull
(if you have another ground wire to turret, the white recoil wire can be attached to that ground
wire and only one wire (green) is needed from turret to hull to operate the recoil).
- “Soft” mechanical connections, bungee and string, allow bumping of barrel with no damage.
- No servo or extra parts needed
- Works without modifying TX or Tamiya electronics setups (sound, flash, etc. all work as in stock setup)
Disadvantages:
- Takes some fiddling to set up.
- Uses a good Tamiya recoil, but if careful and save Tamiya bracket, you can reassemble Tam unit and go back to it.
Note that I used wound string on the elevation unit too. Makes the elevation control much smoother and also “bump-proof”. Working on a smaller, simpler system. More soon….