Tank alignment...

[Myk]

Hello everyone,

with all of the rain in San Diego lately I have been unable to fly any of my planes, so I thought it would be a great opportunity to finally buy myself a tank. The Abrams is the only machine that has ever caught my eye, so I picked up a Heng Long 7.0 with the plastic wheels, treads, steel gears and metal gearboxes; production date was sometime in 2022.

I love this thing! I take it with me everywhere in the hopes that I can run and listen to it! Just about a week ago, I bought the 390 Red motors from Toucan Hobby to get a little better speed out of the tank, and it responded beautifully.

However, I went to the tank one morning, started it up and noticed that it was pulling severely to the left when I was commanding it to go straight. I had to push the drive stick up and to the right to drive straight. I checked the left tread and wheels for any hang-ups; everything seemed fine. I checked the tension and both treads seem equal. I opened up the gearboxes again and did not see any problems with gears or anything like that.

What could be causing my tank to pull left? i marked the treads and can see that the right tread is moving much faster than the left. Any suggestions on how to troubleshoot will be greatly appreciated. Thanks in advance!

[SoCalBobS]

Could be a bad motor, or something more subtle. Check to see if any track pins have drifted out, which did on mine some time back. If so, you may see some plastic shavings where the pins rubbed against the tank. If it's a bad motor, you could always put the old ones back temporarily.

Bob (SEFSD member)

[Myk]

Could be a bad motor, or something more subtle. Check to see if any track pins have drifted out, which did on mine some time back. If so, you may see some plastic shavings where the pins rubbed against the tank. If it's a bad motor, you could always put the old ones back temporarily.

Bob (SEFSD member)

Bob, thanks for the quick response. Yes, my next idea was to put the original motors back in and see if the problem remains. Is this a common occurrence with these motors?

[Myk]

An update: I reinstalled the original 380 motors and the tank still pulls to the left. I'm still not seeing anything wrong with the gearboxes or the drivetrain on the left side. Any other ideas guys? This thing was driving perfectly straight just two days ago...

[cmdrcody]

Check on your transmitter to see if both of the trim controls on control stick 2 are still centered. The trim control below control stick 2 makes the motors run evenly (balanced) on RPM for forward and reversing. The trim control to the left of stick 2 controls the amount of RPM to motor while making left & right turns, also making the turns balanced. If those trim controls are still centered, try swapping the tracks to see if binding links are the issue.

[SoCalBobS]

Did you check the track pins? Tanks with side skirts are vulnerable to this issue, because of the tiny clearances.

[SoCalBobS]

Did you check the track pins? Tanks with side skirts are vulnerable to this issue, because of the tiny clearances.

[RichJohnson]

If the trim controls are centered and you still have the problem something is dragging. You could have a wheel locked up or tightly rolling. Its also possible the bushings or bearings in that trany are going bye bye. I have blown out a number of stock HL tranys and even the ball bearings in the high grade ultimates because the bearings are now cheap chicom ones.
If you need some help your welcome to come over to my house and we can dig into it, Im in west chula vista

[Rubicon99]

Hello everyone,

with all of the rain in San Diego lately I have been unable to fly any of my planes, so I thought it would be a great opportunity to finally buy myself a tank. The Abrams is the only machine that has ever caught my eye, so I picked up a Heng Long 7.0 with the plastic wheels, treads, steel gears and metal gearboxes; production date was sometime in 2022.

I love this thing! I take it with me everywhere in the hopes that I can run and listen to it! Just about a week ago, I bought the 390 Red motors from Toucan Hobby to get a little better speed out of the tank, and it responded beautifully.

However, I went to the tank one morning, started it up and noticed that it was pulling severely to the left when I was commanding it to go straight. I had to push the drive stick up and to the right to drive straight. I checked the left tread and wheels for any hang-ups; everything seemed fine. I checked the tension and both treads seem equal. I opened up the gearboxes again and did not see any problems with gears or anything like that.

What could be causing my tank to pull left? i marked the treads and can see that the right tread is moving much faster than the left. Any suggestions on how to troubleshoot will be greatly appreciated. Thanks in advance!

First make sure the track is properly set on the sprockets. They have a tendency to ride up and slightly off then catch in an "out of timing" position. This will cause the tank to pull to the side that has the catch.

If the track and sprockets are alined and meshed correctly use the trim feature to make the tank drive starlight. "G" button and right stick. Press and hold the "G" button and move the right stick in the direction you want to trim. Might take four or five adjustments to get the trim set.

Having to trim a tank is normally, but if the trim does not work to solve the problem then you have a another issue.

[Myk]

Check on your transmitter to see if both of the trim controls on control stick 2 are still centered. The trim control below control stick 2 makes the motors run evenly (balanced) on RPM for forward and reversing. The trim control to the left of stick 2 controls the amount of RPM to motor while making left & right turns, also making the turns balanced. If those trim controls are still centered, try swapping the tracks to see if binding links are the issue.

I'm certain that the trim controls on the stock Heng Long transmitter don't actually work since they don't move. I can understand cost cutting, but why even go to the trouble of making fake trim buttons lol.

Did you check the track pins? Tanks with side skirts are vulnerable to this issue, because of the tiny clearances.

I did in fact check the track pins. Some of them were slightly backed out, but not enough to cause physical interference with the body of the tank such as the side skirts. Of course, now I want to triple check the treads just to make sure the pins aren't touching anything.

If the trim controls are centered and you still have the problem something is dragging. You could have a wheel locked up or tightly rolling. Its also possible the bushings or bearings in that trany are going bye bye. I have blown out a number of stock HL tranys and even the ball bearings in the high grade ultimates because the bearings are now cheap chicom ones.
If you need some help your welcome to come over to my house and we can dig into it, Im in west chula vista

I truly appreciate the offer for assistance! If the bearings/bushings are gone, then can I just order new ones from Motion or Heng Long, etc? Would it be better just to replace the gearboxes?

First make sure the track is properly set on the sprockets. They have a tendency to ride up and slightly off then catch in an "out of timing" position. This will cause the tank to pull to the side that has the catch.

If the track and sprockets are alined and meshed correctly use the trim feature to make the tank drive starlight. "G" button and right stick. Press and hold the "G" button and move the right stick in the direction you want to trim. Might take four or five adjustments to get the trim set.

Having to trim a tank is normally, but if the trim does not work to solve the problem then you have a another issue.

Ok thanks for the suggestion on the trimming: I didn't even know that trimming was possible on these things because the transmitter has those fake trim buttons, and that factory manual wasn't the easiest to follow. I'm almost certain that the track is seated properly on the idler, road wheels and drive sprocket, so I'll be sure to try the trim feature as soon as I get back to the tank. I want to thank everyone for replying and trying to help out. I contacted Motion, since the tank is still in its thirty day warranty, but they just want to start a return/warranty claim. I don't want to do any of that stuff, I just want to drive this tank! I'll let you guys know if anything else develops.

[tank_me]

I've even had gearboxes where the sides of two gears on separate shafts are rubbing. I shimmed the shaft that was shifting side to side with a washer to keep them from putting drag on the gears.

Derek

[Myk]

I've even had gearboxes where the sides of two gears on separate shafts are rubbing. I shimmed the shaft that was shifting side to side with a washer to keep them from putting drag on the gears.

Derek

That's another great idea. When I get back to the tank today, I will check to see if the gearboxes spin differently from one another.

[SoCalBobS]

Since we're not there, it's hard to interpret what the problem is. here's another possibility: Look in your 7.0 manual addendum. Near the bottom of the third page there an option for for a double current system. This is for a one drive, one steering motor transmission system. Could you inadvertently changed this option? "G" and "Lock" buttons held down for 5 seconds toggles this option.