Hello All,

I have a question regarding movement behavior of a tank of mine using a Tamiya Sherman DMD and a Pershing MFU. I put these electronics is a stock WSN T-34 (meaning stock gearbox at least). If I push the throttle forward and move the tank, I can turn the tank by pushing the stick left or right as you would expect. However, if the tank is at a standstill, if you push the stick left for instance, then while the stick is in the full left position, start pushing it foward (to make a left from a stand still), the tank will actually kick right! If I repeat the same steps and try to make a right hand turn from a stand still, it will kick left. If I have any foward movement (at any speed), it will turn left and right correctly while on the move. Is this normal or possibly an issue with using mixed electronics?

Thanks alot all...

Dave

Check your tank antenna from the receiver first. In the past I have duplicated your issue (and others) by not having a good enough tank antenna. As to mixing DMDs, I cannot address that issue, but I have observed others are using that mixed setup for their Sherman Easy 8's without issue.

Your Sherman Control Unit is intended for a front wheel drive tank. You have it installed in a rear wheel drive tank. Seems you would have needed to swap leads (right to left side) on the motors and reverse your throttle direction to make it function properly, maybe it has something to do with what you did to correct for the change from front to rear drive in your transmitter.

If I were to obtain one of those WSN / Trumpeter T-34s I would put KV DMD/MF units in it. I don't see that happening any time soon though.

I never had a problem when I tested my set up on my Sherman with those electronics matched. But I do have a Sherman set up in my WSN T34 and you do have to flip-flop the L & R leads to the motors.


- Jeff

Check your plugs on your cable that runs from the dmd to the mf unit.  I had one do similar stunts and discovered a wire had backed out of the molex plug body on this cable.  If one has backed out, you'll see it.  I used an icepick to push it back in, and everything worked. 

I'd also try a self test on the DMD (its in your dmd manual). Afterwards, I'd try to reprogram (I mean recalibrate per the instruction manual ) it. Also check to make sure you haven't got any of the DMD wires plugged in backwards to the receiver (i.e. the positive side on the negative side).

Next, I'd swap out the radio with another tank (to make sure the radio isn't the problem) and reinstall if thats not the problem. Next I'd swap the dmd out with another tank and reinstall if that's not the problem, and finally swap the mf unit. It's kind of shotgun troubleshooting, but it works. Sooner or later, you'll find what's causing it. I'd suspect faulty Tamiya electronics last, as they are pretty robust.

You didn't really think you were gonna get to lay around and watch sports on Christmas day did you??

Jeff's right, thinking back I had one that didn't act quite right at first. A simple double check of all connections and recalibrate the electronics and it all worked fine after that. I guess sometimes it doesn't read the radio while going through the process and re-trying it does it.

I've never had a defective DMD MFU, ever.


- Jeff

I had a MFU go bad...once.  MF-01 out of a Panther.  Symptom was that when powered up, the gun immediately went into a continual recoil cycle at 1/2 speed without the gun sound.  Wierd.  Tamiya replaced, no problem.  Funny thing was, my buddy Tail End Charlie had the same thing happen to one of his about 3 months later.  Oh well, at least it was easy to diagnose. 

That's good to know Jeff. I'm working on my Panther now, maybe I should look into it.


- Jeff

Hey, thank you all for your responses on this. I'll be going through that tank over the holidays and hopefully will find why it behaves this way. Thanks again for all the advice.

Dave

Hello Dave

You may want to try reprogramming and pay special attention to the stick deflection. An overstick condition when not intended can produce some unpredictable results.

Well all, I tried everything from recaliberating (moving shy of the extents and also going to full extents), changing the leads on the motors, to checking/rechecking every wire and polarity, and I still get one of two behaviors.

1. It behaves as my original message states, if you move forward, you can gently turn left or right. If you try to move foward while the stick is in a turning position, it kicks to the opposite direction.

2. This is almost the exact opposite of #1. If you move foward then try to gently turn, it will turn in opposite directions. If however you move foward then kick it either hard left or right, then it will turn in the correct direction all be it very fast and hard.

I can switch between problem 1 and 2 by simply reversing the servo on the radio. It's almost undrivable while battling as it's hard to always make gentle easy turns while you're getting shot at.

I'd rather not rip out my Tiger I DMD/MFU from my Bandai IV as I'm guessing it would simply work just as it currently does in the PzIV. I'll have to look into getting either a Sherman MFU (unlikely as I'm using gun recoil) or a Pershing DMD in order to have full matching sets since the mismatched isn't working out.

If anyone else has any other ideas, I'm all ears.

Thx again you all, I appreciate all the help.

Dave

If it were me I would give Tamiya a buzz 949-362-2240 before you do anything drastic.


- Jeff

Hello Dave

This sounds like a radio/stick deflection issue more than the Tamiya electronics. I'm musing here but it sounds like the left and right sticking is acting like a trim is not zero'd properly. Maybe a negative shift for extreme deflection?

The fact that you can gently turn from a forward (or reverse position supposedly) may indicate a range near the extreme left or right that reverses the motor direction.

Can this issue be duplicated from a reverse steer direction? Have you tried another radio? Is the crystal socket secure?

Check to see if there is a small range in the extreme left and right that reverses the direction desired.

Hello all,

Is there somone out there who is using a Sherman DMD (I've tried it with the Pershing MFU unplugged and it still behaves the same) in a WSN T-34? If so, could you tell me how you've wired the blue, purple, white, and orange motor leads coming off of the MFU to your left/right motors? I don't think this will make a difference ultimately, but at least I will know that I've checked this area off the list of possible culprits for the problems I'm having.

I have tried another radio and still get the same behavior so I think that possibility has been eliminated. Thanks Panther F, I think I will have to finally admit defeat and call Tamiya about this.

Thx again everyone.

Dave

Hey Dave, hope you find something out and hang in there!


- Jeff

Hi Dave, Here you go, good luck and let us know. John

1. First generation DMD gearboxes (no black plastic covers) are wired in my Sherman as follows:

a. Sherman right side gearbox, no black plastic covers:
yellow to orange
green to blue

b. Sherman left side gearbox, no black plastic covers:
yellow to white
green to purple

2. NOTE second generation DMD gearboxes (with the black plastic covers) are wired as follows:

a. Right side gearbox with black plastic covers:
yellow to purple
green to white

b. Left side gearbox with black plastic covers:
yellow to blue
green to orange

Thank for the Info Pcomm1. I tried different wiring schemes and it's still a no go. I'm going to give Tamiya America a call tomorrow and see if they can test this DMD that I have. I've never had this type of issue before so I'm convinced it has to be the electronics in this case.

Again, thanks all for the help and advice.

Dave

Could you please elaborate and tell me which DMD and MF units you used? I ask because the DMD T-01 that came with the 56005 Sherman is slightly different from the DMD T-5 that comes with the 56014 Sherman.