Simple Recoil System
 

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….

Interesting approach. Typically we see things going digital( servo Recoil) in this case you are promoting a return to mechanical. Cool.

Dan,
I did go to servo recoil with programmed fast recoil and slow return. But the recoil wasn't as fast as I see in prototype video. Also, tying in the servo required more wires to the turret. I'm limited to 12 wires thru the slipring I use.
I also had servo gun elevation, but no matter what, the motion was too "ratchety". And with elevation linked to MG fire and Gun fire functions, I had to use a separate channel to control elevation. Worked fine with Tx channel mixing, but again just a bit more complicated.
I have a very small, simple mechanical elevation worked out that will work directly off the existing Tam two-wire output, but I'm not home til mid Dec to install/test it.
Best,
Dan

I'm planning to use servo recoil and servo elevation with a 12 wires slip ring in my panzer IV turret...

I will use a step down voltage regulator adjusted at 5 Volts to power the servos and just send the servo signals through the slip ring: Meaning 4 wires( positive, ground, recoil signal, elevation signal)...

Hope it'll work.:o

The 12 wire slipring worked fine with servo wiring and with TBU wiring. Used a common ground and positive for servos at full battery V, but your approach to use reg. 5V is better.
Ran power for BP firing gun through a single set of slipring wires. Measured 4A spike at 7.6V. Slipring was fine, but the current surge was very short – the fine nichrome wire used as an ignitor blows like a fast acting fuse. Ran many shots thru the slipring, but still decided to run separate wires for the gun to prevent damaging the slipring.

A large capacitor in the turret could help taking some of the load of the slip ring...

In the same line of thought; I wonder if a high voltage flash unit driver would supply enough current to the nichrome wire as to ignite the charge...:confused:

That is an interesting concept. Reduces the wires need to run through the slip ring. You just need on set of power wires,, and only 1 wire for each servo passing through the slip ring.

I have not gone down the slip ring apporach yet, as for me having enough slack for two complete turns is enough. Wrap up the power supply to the rotation motor with the turrret wires and make it the short one. It will pullout first and prevent any harm to the rest..

Norman,
I don't use the Hi V flash because I set the gun up to work with a socket for interchangeable modules - one with an LED when just flash is wanted and the other is a BP cartridge for pyro flash and smoke. The socket is activated by a servo mounted switch in the hull. The servo is simply Y'd off the Tamiya Elevation/MG channel.
In the sketch below how would I add your suggested capacitor? Seems that the servo and switch would need to be in the turret for the high current to be above the slipring. But then the ground leg would see the current anyway?
On the HiV flash....thought about using it for the nichrome igniter, but , one, I didn't know how to hook up the trigger (third wire) circuit, and two, I needed to know for sure that no power/charge was in the circuit when I load a BP cartridge.
Any help appreciated.
Thanks much,
Dan

I don't see any obvious electronic solution to that problem...

I would keep the system the way it is right now until failure of the slip ring( if it ever happens ); and upgrade to a 24 wires slip ring if needed:http://www.ebay.ca/itm/22mm-24-2A-24...item4ac29f2728

They went down in price quite a bit since I bought my first one a couple years ago...You now have 24 wires for the price of a 12 wires back then...:o

Very interesting approach. It looks to be easily adjusted too. Nice work. I love it when we can "think outside the box".

I liked the impact system but it is way too heavy. Plus, many were built upside down (dowel pin protruding from the wrong side of the gear disc).

I decided to make my own version. I have about 40 of them out there now in customers tanks. The one in my #1 Battle tank (my Panther G) has been working for 5 years now.

Here is my approach: The Held high speed recoil http://www.rcuniverse.com/forum/atta...mentid=2050618http://www.rcuniverse.com/forum/atta...mentid=2050619http://www.rcuniverse.com/forum/atta...mentid=2050620http://www.rcuniverse.com/forum/atta...mentid=2050621

Bob

That's exactly the design of the Leo recoil unit. Just get one of those to install instead of modifying.