kizwan

Hi,

This is USM41A3 Walker Bulldog Light Tank, production Jan/2014. 5 days old, played only less than a hour total. Battery recharged two times; first when I brought it back & second was yesterday. Today is my day off, so I thought want to play with my tank.

Chronology:-

1. Played for few minutes inside the house. On carpet & floor.
2. continue played outside the house, started on the floor
3. then continue on the soil/ground surface. No obstacle at all. Moving the tank slowly, not full throttle. Honestly less than a minute. Then I noticed the sound cut off & the lights on the tank flashing. The tank still can move & accept all commands.
4. I immediately moved to the floor. I shutdown & restart the tank. This is when I tried to moved the tank forward, the "engine" cut off. Restarted it again, same thing. I thought the battery already discharged.
5. ~5 hours later, after battery recharged, the tank still doing the same thing. I picked up the tank & I found out the left wheel only going backward & the right wheel only going forward. This is when I smell something burning & smoke started coming out from the right side of the tank.

cleong

Take it as an excuse to upgrade to a Clark TK board. You will find that your tank drives a lot better, with better sound, no herky jerky recoil, and you can gain IR battle compatibility with Tamiya tanks.

ausf

It's been a while since I've used a RX-18, but if I recall correctly, the FETs are under the piggybacked board there (they weren't covered in earlier models). If so, those puppies get hot when worked, most guys used to either keep the cover off or add a fan (or both). It's the nature of the beast, when you could get a board for under $10 retail, this happens, it's nothing you did.

You can replace and add a fan, etc. but as cleong said, no better time to upgrade.

YHR

I think the issue is the quality control. I have had an RX 18 go up in smoke as well for what appears no reason. However I have had others that perform really well


This weekend I had my Leopard 2 out with all metal suspension and tracks. I ran a 5000 mah Lipo and the gear boxes have Max Pro 400's, I ran the thing solid for over an hour in long grass just to see what would happen to the RX 18, Answer, Nothing. The motors were hot to the touch,( hotter then the RX18) but the RX18 handled it.

I think the RX 18 gets a bad wrap as every failure is thrown up as a reason to get something else. I have had a Clark and an IBU2 go up in flames as well. So these things will happen from time to time. Nice thing about the RX 18 is it can be replaced for 20 bucks.

This is kind of ironic as I was about to post about how durable the RX18 has become, and use my Leopard 2 story as an example.

Panther G

Me thinks he may have had something jammed a couple of times. Looks like stalled motor damage to me.

kizwan

@cleong & @ausf, do I need new transmitter with TK board? Since RX18 is cheap, I might get two or three for rainy day & a fan.

I can't believe this is happening to me because others run just fine in the same environment/ambient (if I were going to blame hot ambient).

The motor doesn't seems to stuck or jammed when it was working. However, when I tried to turn the wheels (sprocket) by hand, I can feels some resistance. Should it behave like that?

YHR

What I have found is the most common problem for an RX 18 failure is a gearbox issue. Tight or cogging gears will cause the motors to draw more amperage and that is what will kill the RX 18.

My leopard 2 is a heavy tank and I was running it in long grass. The Lipo battery has way more potential to deliver RX18 killing amperage then a standard Nimh battery and it powered the tank fine. Honestly the Maxxpro 400 motors were uncomfortably hot to the touch when I was done.

However the tank runs smooth and true with no drive line issues. Also never work a stalled motor with an RX18. If the track stops turning find out why..

Yes a Clark board will require a new transmitter. A hobby grade radio can be had for less then $30 now though so it is not much of an issue.

kizwan

The tracks never stop turning while moving. It doesn't stall. Everytime I played with the tank, I don't detect anything unusual from the tracks. I'm 100% sure at full speed the tank moved smoothly but when I tried to move at low speed, come to think of it, it's not smooth when to get it going, sometime it suddenly move at faster speed. I thought I'm just clumsy with the remote control because when it already moving it move smoothly at low speed just like I command it. But like I did mentioned earlier, if I try to turn the sprocket by hand, there is some resistance. The left sprocket feels more resistance than the right one. I just want to confirm again, is this cause the board to burn? I have cheap OEM tank where it only have little resistance when I try to turn by hand but this tank is slightly smaller than 1/16 tank. When the second time, after the battery recharged, the power cut off when trying to move forward, I did consider stuck wheel/gear & maybe it is because both tracks can only move in one direction right before the smoke coming out from the tank.

If it's the gear or motor, how to troubleshoot & how to fixed it?

kizwan

This a video showing the gearbox & motor. The right motor loose little bit (not shown in the video). I'll need to tighten it later. Please let me know if there's anything wrong with them.

http://www.youtube.com/watch?v=3GGVzNa1-j0

YHR

I didn't watch the video but you may of just got a bad RX18. The nylon gears with a slipper clutch should have protected the RX18 if it was a gear problem

kizwan

Yeah, just my luck to get faulty board. I hope next board doesn't have any problem. It seems, the sudden flashing light while the tank moving maybe an indication of overheating. I checked the manual, cover to cover, no mention about this at all. Funny thing, when I saw the light flashing, I did consult the manual. If this info was added to the manual, the board might not burn & I can take preventive action.



@cleong, do you know any SG rc online store that sell RX18 board?

ausf

It's not an issue of luck, it's just an issue of RX-18s. I would bet of the guys using these over the years, the ones who haven't experienced a toasted HL board would be in the minority. Out of the 4 I've owned, in stock condition, I've had a bad board, bad wiring and bad Tx, but you know 3 out 4 ain't bad...

I bought a bagful of RX-18s a while back through Banana Hobby, but I think that deal is long gone ($8 a piece and they were literally stuffed in a bag all stuck together with double sided tape). You should be able to get a reasonable price on one somewhere, if so, grab a couple if you plan on sticking with HLs.

cleong

Try www.rctanksingapore.com.sg they should be able to set you up with something.

kizwan

Thanks but RX18 is not listed in their website. The seller from whom I bought my tank want to sell the full set (electronics) including the remote control.

Marc780

Sorry this had to happen.
I wired in a 5 amp fuse. it is easy. (It's shown by the vertical white arrow) Alls you need is two female crimp on connectors and a 5 amp automotive fuse. It goes from the power switch where the red wire goes to the plug in connector on the RX18. The female crimp connectors just push right onto the fuse. You can use the insulated type or the bare metal type, if the latter is all i have at the moment, i wrap some elec tape around the bare metal connectors so they don't short out.
I tape a spare fuse or two inside the tank, as I've had this same problem-driving the King tiger through some loose wood chips (the kind they throw around trees for decoration) some chips jammed the tracks and the tank stopped. Cleaned out the chips and changed the fuse, no harm done.



You can see where i glued on a 25 mm fan from Evercool, to the box. It cost $10 from amazon, it turns at 8,000 rpm. I traced around a nickel and cut the hole with a dremel tool, plus some slots on the bottom of the box to hopefully let some hot air out. The fan is in line with the fuse also-i split the wire using the female connector, coming from the motor side of the fuse, two wires coming out of one female connector, from the fuse.

mcovalsk

I have had the same problem with a Sherman, the first Rx18 burned. I almost didn't run the model, then what happened?
I discovered that the gearboxes are very closed in the Sherman and one motor terminals ( those wires for the capacitors) touched with the case of the opposed gearbox, that was the cause.
I checked my others Sherman and some had the same problem, I placed an isulator and fixed the problem.

kizwan

@Marc780, how often you need to change the fuse? In my case nothing was jamming the tracks.

@mcovalsk, yeah, there's a lot of exposed wires/terminals that should be insulated properly. However nothing is touching that can cause short circuit. I don't think I check the wire on the motors. I'll check that later. Thanks.

MYR$300 question; should or should not the RX18 handle the stress & load when running off road; tall grass, soil/ground surface with obstacles? Yeah, I know, why I'm still asking this question since YHR pretty much proved RX18 can handle it.

ausf

From what I know about electronics, everything is rated for usage, intended and nominal. Things like capacitors can be chosen based of hours of life expectancy, so much so that manufacturers can decide how long they want something to have a useable life. Depending on the company, they engineer to last a long time or just past the return date. There's no surprise that you don't hear a lot about FETs burning on Tamiya DMDS with their lifetime replacement compared to HLs.
I bet HL's FETs are barely rated to do what they do without resistance, so any added load is asking for trouble. They solution is to protect it (fan or fuse), often replace or use a different system.
I comes down to economics, $8 (HL) versus $200 (Tamiya) and everything in-between.

YHR

The load rating on the FETS is not that bad. I believe it has more to do with the QC at the chip manufacturer. You get a bad FET and you have trouble. I have had an RX18 go up in smoke for no apparent reason, and others move 14 pound tanks around.

i believe the design is good, but the unit suffers from some bad components from time to time.

YHR

See below

YHR

I can send you one

ausf

That's what I'm saying.

When I was working out the TBU design, I could choose a cap that just met the requirements and had a useful life of x amount of hours or I could pay more and get one that is rated much higher (so it has less strain on it) and xxxx hours of useful life. If I plan of providing a warranty and continuing in business, I get the better one. If I just want to pump out stuff as cheap as possible, I get the cap that'll last til next Thursday and not answer the phone.

I'm assuming Clark and others are using better components, HL can't at the price point.

kizwan

Thank you. I really appreciate that. I just got another RX18 board yesterday. There is miscommunication which ended up cannibalising a tank for this. For some reason the original receiver board also dead. So both changed.

Panther G

Actually the RX18 doesn't have a true slow speed. they are supposed to be proportional but they aren't really in stock configuration. when you are trying to drive the tank slow with a stock board you are actually drawing more amps just like if the motors are stalled.
It has more to do with the physics of electric motors really and Ohms law than it does with the board. For true proportional driving you need an upgrade board or an add on system. Even tall grass for short periods of time can really stress the motors which in turn pull many amps for short periods of time.

Marc780

Kizwan the fuse should behave just like the ones in our cars, they don't normally require changing. In 35 years of automotive, which is generally the same type of fuse everyone uses (some use a 10 amp fuse, or 7.5 amps instead of 5) seldom seen bad fuses when everything else is ok on that circuit -so should the fuses be. If you install a fuse and it blows straight away something is wrong in the circuit, period. You're certain there's not a short circuit then one of the motors could be drawing too many amps for some reason (i dont know what that reason would be but it is possible)also these goofy Asian electronics could be the circuit board itself.

Don't forget anything is possible with this half- engineered Chinese stuff they put in our tanks. If we all had the money we'd skip this schlock and just buy Tamiya. But we don't so these are the problems we get. I have 3 of these tanks, they are all lots of fun, but never are all three of them working at the same time. And for the love of all that's holy NEVER drop your transmitter or slap it to get the batteries out!!! They are MORe fragile then eggs, plus there's no guaranty, when you spend $40 and wait a month for the new one, THAT one wont be bad out of the box!!! ( If you want 100% tested and guaranteed HL electronic parts i highly recommend TPA store at Amazon...everybody else is a crap shoot esp anybody on that online garage sale Ebay...)