strange recoil bug

[John Grima]

When testing the model today I ran into an interesting bug, when the tank is powered on the barrel recoils, then the left hand track runs full throttle in reveres. What is interesting is that when the servo for the recoil is unplugged the issue stops.

The recoil system is new and is fresh, and when tested with another speed controller the same issue occurs. I was thinking it may be the bene sound system, and before I do any further disassembly I was wondering if the sound system is not configured correctly. When the tank is powered on it makes two pops, the rest of the sound system works fine. there is throttle, proportional smoke, and firing sound, the only hiccup is this running issue.

Like always any help would be appreciated

[Armortek]

Hi John

Two things are happening here. The first is that the high power recoil servo draws enough current, when switching on, to pull down the 5V supply. This makes the receiver think that it has lost signal and it goes into failsafe mode. This failsafe is for IC engined aeroplanes and makes the track run in reverse.

Turn failsafe mode off on your transmitter. This is an essential for these tanks anyway.

Connect a 4.8Volt Ni-cad battery pack in parallel with the 5V power supply via an on off switch. The receiver battery and switch that comes with the radio gear is ideal for this. The battery provides back up power for the servo at times of high demand and is kept fully charged by the 5volt power supply at other times. Use the switch to isolate the battery when you finish running.

This solution also massively reduces servo noise heard through the sound system.

Mark

[John Grima]

Thanks mark, I'll turn off the failsafe on the transmitter. As for the battery is there a diagram, or a picture of how the setup goes together?

[John Grima]

A quick update, the fail safe was turned off, and the track now behaves itself (thanks again Mark!). The recoil is a little hit and miss and sometimes it looks underpowered at times.

I'm interested in adding the second battery, does anyone know or have any pics of the setup?

[Dave Nadin]

Sounds like you have a small amount of drag between the barrel end & the recoil bush or the recoil guide. A bit of gentle work with fine grade ememery cloth. Untill the recoil moves by hand without any resistance. Its a case of a little at a time untill it moves sweetly with the servo cornected
This worked well with my centurion, & I did'nt require the back up battery.
Cheers Dave N

[John Grima]

Thanks Dave, the hand fitting was already done to the barrel / bushing. a small amount of grease was also added during install, and I the barrel movement is very smooth when moved via hand.

Sometimes the recoil works like a charm other times it's a little sticky.

[Dave Nadin]

Hi John, wipe the grease off with a dry cloth, but dont degress the surfaceses. Its possable that the grease is a bit to heavy and causeing the recoil drag. I use a smeer of 3in1 light oil to lubricate the recoil bush.
cheers Dave N

[John Grima]

Dave, thanks again for the advise.

This morning I took the barrel off and noticed the issue, When the tank was painted the extra layer of paint closed the tolerances of the barrel and the bushing. I evenly removed some material from the bushing with a sanding drum on a dremel and polished the bushing smooth. Now the recoil system is buttery smooth!

[Dave Nadin]

Glad to be of assteance, Proper job done, now time for tea & crumpets