sher

Lego technic 42070 All Terrain Tow Truck not moving forward or backwards

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Hi everyone, I have just finished building the lego Technic all terrain tow truck. Unfortunately none of the power functions are working, other than the steering option (i.e. wheels turn left and right).  So my truck won't move forward, backwards, the outriggers won't move either.  The batteries in the remote control are brand new so that isn't the issue.  I have also tried other remote controls from different sets-the other remote controls light up (so again their batteries are new) but the truck still won't move forwards/backwards etc.  The receiver may be the issue however I don't have another one to check if that is the problem.  Has anybody else encountered this problem? If yes, how did you resolve it?  Could it be a problem with the motor?  

Many thanks in advance, Sher

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Sorry to hear that. So what happens when you try the other functions? Can you hear the motors working but nothing happens? Is only one motor working? Are the motors trying to work but are stalled? Can the model be moved along the floor easily when pushed by hand when in neutral or when in gear? It seems strange that steering works but nothing else, as the motor that drives steering can also drive two other functions.

Edited by allanp

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Are you 100% sure the red clutches were not mis-aligned when you built the model? When you fit the switches to either side with the white component the red clutches all need to be center with the switches set to the middle - technically everything is dis-engaged. Allowing the model to be free roamed by pushing it, once you engage the clutches, the power functions take over and then you can control. 

Set 42070 is actually a really complex build, for its harsh reviews its got some clever - but also confusing engineering. 

Oh and yes test the motors, to ensure they all work.

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Probably got one of the two drive differentials the wrong  way round !

Edited by Doug72

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Sorry about this question but, sometimes frustration overtakes common sense. Have you checked that the channels are set the same on the remote and IR receiver?

Edited by 1963maniac

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Did you ever find the problem here sher?

 

I have the exact same issue, everything works except for the moving forward/backward part.

If i lift the truck so that the wheels are in the air, the engine moves them but at diffrent speed.

If i put it in neutral it all works fine when moving the gears manualy.

Edited by MariusNO

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On 27/12/2017 at 2:22 PM, Doug72 said:

Probably got one of the two drive differentials the wrong  way round !

As Doug72 already stated, be sure the differentials are set in the proper way.

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2 hours ago, MariusNO said:

I have checked my differentials, all three of them (one for each axle) and they are according to instructions.

I think you need to change the gears friction by making sure they slightly have area to move.

Look at the instructions warning and you will find what I mean.

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I had trouble using Duracell batteries in the remotes a couple of years ago, I switched to vitiar batteries problem solved

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On 31/12/2017 at 10:13 AM, MariusNO said:

If i lift the truck so that the wheels are in the air, the engine moves them but at diffrent speed.

If i put it in neutral it all works fine when moving the gears manualy.

Definitely seems to be due to friction & / or binding of parts causing this problem.

The front & rear wheels are rotaing at different speeds due to the red 24/16T differential spitting the drive power. 
i.e. twin rear axles have more resistance than front axles.

It pays to test things as the build progresses rather than complete the build before testing, that way you have an easier fix if any problems saving a big strip down to find the fault.

Try following tests and run motor for each test.

1/. Front wheels on the ground, rear wheels in air.

2/. Front wheels in air rear on the ground.

3/. Repeat 2/. but have one pair of wheels on ground, the other pair in air.

4/. Repeat 3/ but reverse which wheels on ground / in air.

5/. All left side wheels on ground, right side wheels in air.

6/. As 5/. but left in air, right on ground.

Should then be able to determine which parts are binding.

Good luck !

 

Edited by Doug72

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Hello from France,

Did you find a solution please?

Here my son has EXACTLY the same problem, he just had this toy for Xmas and he is very disappointed as he was so happy to finish the assembly. Everything works fine except wheels. Posting a video is useless as it would be exactly the same symptoms as MariusNO's.: to me, this red differential is a weird system: it moves correctly front wheels, but it is not efficient to move the rear driveshaft, it spins sluggishly, and once the wheels are on the ground, rear wheels spin the opposite way :wacko: so the truck doesn't move at all...

 I tried Doug's advice but it doesn't help. All gears, bars, shafts and axles seem to move softly, no abnormal friction...  My only temporary idea is to completely remove the rear driveshaft :look:

It seems it is a design problem of this model? Should I return this to the Lego factory?

Thank you for you ideas

Mitch

Edited by Quirole

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With all wheels NOT in contact with the ground, do all wheels rotate the same way ?

If not try disconnecting rear most axle to see if 4 wheels rotate the same way.

I think I recall there was a similar problem with a previous Lego set where it was possible to build a sub assembly correctly but then insert into the build upside down.

==============================================

I have made a test rig to check correct position of all differentails - see image.
When pushed by hand all wheels rotate in same direction together.

Suggest that when reach step175 it should be tested to ensure all wheel rotation in same direction before moving on with the build.

Instruction book Step 192 shows the four diffs. and the position of the Z28 gear on the 3 axle diffs.

38954787824_0726d9df7d_z.jpg

Edited by Doug72

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13 hours ago, Quirole said:

once the wheels are on the ground, rear wheels spin the opposite way :wacko: so the truck doesn't move at all...

 

Check your differentials are installed in the same orientation as the instructions. Which side the large gear is on matters.

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