I've just fried the main board

[Marty]

Thanks for that, I'll wait for the new board and I'll see what happens.

[wibblywobbly]

Just to explain.

A battery is described as 7.2v xxxxmah. The voltage is a constant no matter what the xxxxmah rating is. The xxxxmah is simply an indication of how long the battery will last before a recharge. The bigger the xxxx is the longer the battery will last. Fully charged batteries will put out 8.4v, and then drop with use. Most boards need a minimum of 6v to function, so that is when the tank stops.

The bigger the xxxx is, the longer it takes to charge.
Quality batteries will pump out 6v+ for longer than cheap ones.

The board pulls current from the battery. An RX18 is a basic board without much in the way of current overload protection. The board will pull current in ever increasing amounts to keep trying to turn the motors. So, when the tracks get caught in grass the motors stall (eg they can't turn) the board keeps pulling more and more current from the battery to try and make them turn. If you don't let go of the stick and clear the jam, the current will keep rising.

The part of the current that does the damage is amps. The board will pull low amps during normal running as there is low load on it.
Jam the tracks and the amps pull from the motors will rise from 5amps to 20amps. That is what fries the esc's on the board. They can't handle 20amps so they fry from the heat that is generated.

Putting metal gears, or low ratio gears won't really help. If the tracks are locked up the motors will still pull amps regardless. It's why HL put slipper clutches on the plastic gearboxes, the clutches will slip allowing the motors to turn and reducing the amp pull. Metal gears don't have slipper clutches, the motors will stall and the board will fry. Low ratio gearboxes will allow the motors to keep turning under excessive load, but even they will lock up if the jam is sufficient to resist the motor/gearbox forces.

You can put 10 or 20 amp fuses between the battery and the board, and between the board and the motors which can reduce the risk of a blown board, but power surges may be faster than the blow response time of the fuses. There are fast response fuses, and resettable fuses if you want to go down that route.

Aftermarket boards have overload protection. If the board detects a current overload that it can't cope with, then it will shut the board down.

The golden rule is that if a tank gets stuck in grass, shut the throttle immediately. Try reversing to untangle the tangle, but only momentarily. Don't keep pushing the stick because all that will happen is that the esc's will fry. It's way better to pick the tank up, pull out the tangled grass, and learn that long grass is a killer when it comes to electronics.

At any tank club meet at the shows the first thing that we do is get a strimmer or lawnmower and cut the grass down. We all know that it is a complete no-no to try and run tanks on anything other than short grass. We wouldn't even try as we know what will happen.

Rob

[Max-U52]

My advice is to dump the RX18 and get a decent board. I put this package in my M41 for about $130US, under 90 pounds, and that included both the board and the TX/RX.

[Marty]

Thanks for that great explanation rob, so I did everything wrong that I could possibly do. Ah well.

Now when I untangled the grass and got it on the bench the motors and gear boxes were free moving but could not get one of the motors to move at all, the other side moved a little then stalled, will this be because one channel was already fried and it was pumping all the power to oneside?
Now when I get the new board hopefully tomorrow, what is my course of action plug it all in and test with no tracks on? Plug both sides in or just one side?

Any way of testing the motors without going through the board?

Thanks for all the help lads.

[hawkeye3guns]

Hi
You can try your motors separate from the board. Just unplug them from the board and connect a 6v or your 7.2v battery direct to the motors, if you put your tank on a block of wood so the tracks are free you can run the motor/gearbox and tracks to check they are free and easy to run. ( positive battery to the red wire for one way of rotation and then swap the leads ie positive to the black wire for the other way). at least you can check they are free before you plug in your new board.
Ckeck in the electronics section of this forum under Heng long and there is a wiring diagram of the RX-18 showing which plug goes where and also which way it plugs in (ie. positive and negative wires).
Hope you are up and running soon
Denzil

[Marty]

Thanks denzil, going too try it today. Fingers crossed.

[Marty]

Quick update,
I connected the motors direct to battery before replacing new rx18, all working.

Connected both motors through the board and all seems good responsive and I ran them for 10 mins with no issues.

So lesson learnt don't think the because it's a model of a tank it will do what a real tank can do, because grass which is 6-8 inches long is 20 odd feet in real terms.
Anyone new to this like me, you will get no better advice than from these guys, thanks again lads.

Martin.

[Marty]

My advice is to dump the RX18 and get a decent board. I put this package in my M41 for about $130US, under 90 pounds, and that included both the board and the TX/RX.

Max the sounds on you bulldog are great what or how do you get that, add on or new speaker to get that deep sound.

[Roboticus_Prime]

Quick update,
I connected the motors direct to battery before replacing new rx18, all working.

Connected both motors through the board and all seems good responsive and I ran them for 10 mins with no issues.

So lesson learnt don't think the because it's a model of a tank it will do what a real tank can do, because grass which is 6-8 inches long is 20 odd feet in real terms.
Anyone new to this like me, you will get no better advice than from these guys, thanks again lads.

Martin.

Something I figured out. You can drive it backwards in the tall grass much better than forwards. But that only works because it's a rear drive tank.

[Max-U52]

Martin, those sounds are from the TK22 for the M41 and it's just a stock Taigen speaker. I agree that the TK22 for the M41 sounds very good right out of the box.

Chase, there's a guy at DTC that has a Tamiya pershing and he's got it set up to drive backwards all the time! He says it just drives much better that way.