Scoopey's Heng Long Recoil Mod

[Scoopey]

After noting that many are not happy with the Heng Long recoil unit working "backwards" and finding a mod that essentially involved turning it through 180 degrees and fitting it backwards I've actually found a way to make the mechanics work backwards.
The conversion is so easy that I ended up converting a second one whilst doing the instructions!
However this mod is only for altering the mechanics, not the electrics needed to "prime" and trigger the unit as I've not got around to that yet. For the impatient there are circuits out there and the microswitch design with the "reversed" recoil mod should work equally well here.
Download the instructions here:-
https://dl-web.dropbox.com/get/Public/S ... DNFRO8-9qA

[Scoopey]

Mini update!
If at any time you here a "ratchet" noise and the mechanism is not blocked then the internal compression spring might be too week. Simply pack it with an extra couple of small washers. This may become apparent when trying to move a heavy (metal) barrel or when forced against a tight microswitch

[jonger]

Just tried your link and got the message "It seems you don't belong here you should probably sign in"
you need to put them on here or make the link an open one.

[Scoopey]

Thanks for that. Some of these file host say the file are open. Its only when someone else tries it I find they are locked out..wish these site would stop hiding bloody setting! I did tried to put the file on here but at just over two megs it said it was too big..
I'll try another file host

http://www.mediafire.com/view/?a5bu8abue8eluin

This one seems to have worked as I logged out and tried the link

[jonger]

Hi Scoopey
Yes that works, good clear instructions, easy to follow so should help a few folks out.

[MichaelC]

Scoopey, great instructions. I have never heard of this before so it was definitely an eye opener for me. As far as the electronics are concerned, isn't it just the case of making sure that there is a "firing pin" on the other side of the slider, and mount the microswitch accordingly (i.e. near the front of the unit).

Correct me if I am wrong, the barrel if wired up this way would be in the retracted position normally, but when you fire, it will extend out slowly, flash and sound will happen when it hits maximum extension, and then recoil back like a real gun ? So for sure the recoil part is very realistic, but it would mean that in the resting position, the barrel will be retracted in, correct ?

[Scoopey]

Technically you are right but as soon as power is applied the barrel will go to its proper position.
Its a little bit confusing but essentially but for most circuit designs for backwards "recoils" involve the recoil unit being connected directly to the battery.
This design I'm going to work on.
A micro switch will then be put in the link to ground which breaks the circuit when the barrel is extended (or nearly extended).
All that is needed then is a trigger, (normally a MOSFET design) that bypasses the switch connecting the negative side to ground.

If my theory is right and I borrow part of the trigger design for anti track recoil the unit will work something like this

First power up
Barrel will extended
Fire the gun (this will momentary bypass the micro switch)
Barrel with spring back and then return by the motor
Switch will cut off power

Gun is now ready to fire again.

In theory unless you have a spurious trigger, once the barrel moves into position for the first time, no matter if you disconnect the battery etc it will function properly. The main trick with this set up is positioning the cut off switch. If its not quite right the you could end up with a form of mechanical "overshoot" where by the micro switch cuts power but the spinning gears cause the slider to spring back thus the switch resets and you end up with a permanently firing gun!
Its all a little trial and error and my proposal is setting the micro switch to cut of power slightly early in the barrels forward travel.
Thus when you fire the gun it will move forwards before springing back and recoiling. I've already tested this idea on the prototype (just don't have any parts to build a trigger circuit) and the slight forwards movement is negligible.

Hmm think I might have lost a few people there...
I'll try to whip up a circuit diagram tommorow!

[971wright]

Hi You shoud have asked before you started its already been done 2 different ways here is my way done in 2008.
http://www.rcuniverse.com/forum/m_80453 ... hor/tm.htm

regards pete

[Scoopey]

Great minds think alike huh!
I like to work on electrical/mechanical puzzles...the trick is to do them ins such a way that they are repeatable

[MichaelC]

pete do you have a youtube video of the actual operation of the recoil ? I am still having a tough time "seeing" it in my head how it works.