Questions on hardcoupling

[Tarix819]

6 minutes ago, Marxpek said:

Will it move in the 3rd gear if you power if purely from the battery box, leaving the receiver out?

Just tried it and no, it still remains stationary even if powered directly from the battery box. (Which is a LiPo btw).

Edited May 11, 2018 by Tarix819

[Marxpek]

Well i think you just have to gear down then, sounds like it is just too much for 1 L-motor, have you tried a 20:12 ratio? if that is possible

Or make it lighter? check the drivetrain on 3rd gear? are all gears ok? running smooth without load?

[Tarix819]

Just now, Marxpek said:

Well i think you just have to gear down then, sounds like it is just too much for 1 L-motor, have you tried a 20:12 ratio? if that is possible

Problem is I want it to go fast but gearing it down whilst will improve the torque will reduce the speed.

[Marxpek]

7 minutes ago, Tarix819 said:

will reduce the speed

I thought it was standing still now?  

speed on a 1.4kg vehicle with 1 L-motor is very limited, especially with these wheels (wich are ligther  then expected, but have terrible roll resistance and rotational intertia), and if the drive train breaks with more power.. i see no other options then making it lighter or gearing it down.

 

Edited May 11, 2018 by Marxpek

[Tarix819]

2 minutes ago, Marxpek said:

I thought it was standing still now?  

speed on a 1.4kg vehicle with 1 L-motor is very limited, especially with these heavy wheels, and if the drive train breaks with more power.. i see no other options then making it lighter or gearing it down.

 

Do you think adding a second L-Motor, gearing the drivetrain down and then gearing it up again just before the differential would work?

[Marxpek]

Not really, the less gears the better, but it might help if there is 1 specific weak point where the drivetrain always breaks with added power, but it will most likely just move the point of breaking to another set of gears or connection. maybe try with a XL-motor if you do not have a 2nd L-motor available.

 

What exactly breaks in your drive train? is there no way to strengthen this? are these parts as old as these wheels?

[TheMindGarage]

21 hours ago, Tarix819 said:

Hi, new here! 

I am a big fan of building Lego Technic RC cars but have a few (probably stupid) questions:

When hardcoupling two motors, is a separate battery box required for each motor to improve the mechanical power?

If I only use one battery box to drive both motors does is the power split between them?

What are some ways of reducing stress on a drivetrain to prevent gears from slipping and grinding?

Thanks,

Nick

It really depends on how many motors you're planning to use. LEGO say that one battery box will run 2 XL motors (more for smaller motors). If you try to exceed a battery box's maximum current, overload protection will kick in so they won't run at full power. However, in most cases you can get away with one battery box.

The most important thing to do to strengthen your drivetrain is to sandwich your gears between two beams. This means they have no way of slipping. If there is one part of your drivetrain that is particularly delicate, you can gear up before it and down after it to reduce the amount of torque passing through it, but this increases friction so only do this as a last resort.

[Tarix819]

Just now, Marxpek said:

Not really, the less gears the better, but it might help if there is 1 specific weak point where the drivetrain always breaks with added power, but it will most likely just move the point of breaking to another set of gears or connection. maybe try with a XL-motor if you do not have a 2nd L-motor available.

 

What exactly breaks in your drive train? is there no way to strengthen this? are these parts as old as these wheels?

I have loads of motors so availability isn't a problem.

When I use an XL motor, a 1:1 gear ratio  of two old-style 16-tooth gears breaks, which I have strengthened as best as I can. 

4 minutes ago, TheMindGarage said:

you can gear up before it and down after it to reduce the amount of torque passing through it, but this increases friction so only do this as a last resort.

Thank you I will try that 

[Marxpek]

10 minutes ago, Tarix819 said:

When I use an XL motor, a 1:1 gear ratio  of two old-style 16-tooth gears breaks, which I have strengthened as best as I can. 

this is within an old style gearbox like the 8860? the axles there have to span quite some unsupported distance and might flex, any way to put a 3L beam inside the gearbox that braces the 16z gears maybe?

[Tarix819]

1 minute ago, Marxpek said:

this is within an old style gearbox like the 8860? the axles there have to span quite some unsupported distance and might flex, any way to put a 3L beam inside the gearbox that braces the 16z gears maybe?

It is not actually the gearbox that breaks. The 1:1 ratio is on the drivetrain before the gearbox. It is the only gearing between the motor and the gearbox. But thanks I will try what you said anyway.

[andythenorth]

1 L-motor per wheel, direct drive (or just 1 pair of gears) 

Needs a switch to reverse one motor's direction mind.

1 battery box and one receiver will run up to 4 L-motors fine, but 2 battery boxes and 2 receivers performs better. 

Might not be the solution you need 

 

[sirslayer]

2 Xl motors and a servo is the best for one battery pack and some weight saving optimizations and a 1:1.66 output (postitraction diff) is great for medium scale models