Power Functions Project

[aminnich]

Hey guys

The micro motor topic got me thinking about power functions and their pros and cons. They are not cheap and they do not have much power behind them. The XL motor gives you some power but not a ton, sure you can gear it down, but then your truck or car (or whatever, im just a vehicle kinda guy) is barely moving.

So I am going to try and make a powerful motor for my lego technic models. I am going to guess that it will be a little bigger than the XL motor, but have much more torque. But I need to know some things first. Does anyone know the voltage in the power functions motors? On the LEGO website the RPMs are listed, but no voltage. If you could help me out thanks!!!

Any comments or suggests, please comment!!

[DrJB]

Check out philo's homepage, he has plenty of info on PF.

[bonox]

They are all 9V with the IR receiver adding PWM for speed control.

The battery boxes are also current limited to about an amp - much of the data on Philo's site is unlimited current and some values are elevated voltage as well.

There has never been a problem applying high current third party motors to lego - the question is "why would you bother ripping up the plastic components to do so?"

[MrNumbskull13]

9V but you will need a motor rated at 1.5A or less if you have the V2 reciever, 0.6A for V1 I think.

[DrJB]

One thing to keep in mind: yes, you can make a more powerful motor, but will the plastic parts (gears and else) be able to handle such high torque applications?

[nerdsforprez]

Check out philo's homepage, he has plenty of info on PF.

www.philohome.com

ALso, I have heard many people talk about how other motors, non-PF, will rip LEGO elements to shreds, but I have not actually seen many posts or youtube vids showing this. Often talked about, rarely demonstrated. Any non-purists out there willing to give it a go? I am currently working on a project trying to power a large LEGO car (4000 pieces) with an RC motor. Once built, I will post vids and pics.

[aminnich]

That would be great. I did not think about the plastic parts getting torn to shreds. And i really dont want to have to make metal gears. if a RC motor does destroy the plastic, i will just stick with the torque-less power functions

[S.I]

Don't the trial trucks regularly already destroy the 8 / 16 tooth gears using only PF motors? You can always design around the problem by using multiple gears, better reinforced designs, etc.

[9v system]

I opened up my pf motors as I don't use them any more. i found that the internals of the xl are the same as the m motor, this is why they have so much power behind the motor. the voltage is 9v but can be adjusted.

[aminnich]

That is interesting to know.

[Saberwing40k]

I don't know what you are really talking about with power functions motors. I mean, have you built creations and have had terrible performance, or are you just saying things. In my experience, PF motors offer plenty of torque, often without compromising speed. If you have problems with that, you've usually built the drivetrain wrong. Also, I've broken gears, as have many other builders. Just ask Boxerlego or Sariel, and they'll tell you all about it. Also, if the PF system is "torqueless", how can ZBLJ's Fox pull a car, or his entire vehicle collection?

[DrJB]

One option is to use dual motors (in parallel) to drive whatever you're after. There is a good example in the PowerPuller. There they use the old motors, but you can use the same idea to double the torque with the new studless motors. Check pages 145-149. I did build it several years ago, and it does work as a single motor could not overcome the high friction from all the fake engines.

http://cache.lego.com/bigdownloads/buildinginstructions/4133390.pdf

[andythenorth]

A single XL motor will chew up 8t, 24t, 16t bevel, and old 16t gears trivially. Just use it on any high-reduction gear train, and stall the tyres. The XL will do this on the 7.2v put out by NiMH batteries, doesn't even need 9v.

Also chews the projecting stubs off CV joints if you have a powered axle with steering. I think it would shear an x-axle too, given the right opportunity.

I have seen fewer (or none) broken 12t, 20t or new style 16t gears. Have yet to break gears with an L motor, but I think it would split 8t easily if pushed.

[aminnich]

I understand everything that you guys are saying. But in all od the experiences, when you wants torque you lose all the speed. and when you get speed you lose the power. I want to use my creation of a new motor for a semi truck to pull a trailer with the 42030 Volvo loader. The truck pulls the combination just fine without breaking anything, but I barely crawls. So want the best of both worlds, speed and power.

[Saberwing40k]

Are you using worm gears anywhere? also, what motor are you using? I think the best setup for you is 2 xl motors, geared down 3:1, with as direct a connection to the drive axles as possible.

[aminnich]

no im not using a worm gear. I am using 2 XL motors (not sure what the gear ratio is) and each motor powers each axle.

[Blakbird]

But in all od the experiences, when you wants torque you lose all the speed. and when you get speed you lose the power.

This is true of any electric or mechanical motor of any size at any price. Speed and torque are inversely proportional. The only way to get more of both is to consume more current. It sounds like you are trying to achieve results that are not practical with LEGO. The XL motor already exceeds the power that can reasonably be reacted by LEGO components. A more powerful motor will not result in a faster heavy model, it will result in more broken LEGO parts.

[aminnich]

:sceptic: UGH... is their anything that could be done to increase the voltage?

[Zerobricks]

Just keep the gearing to the bare minimum. That works wonders.

Also, if the PF system is "torqueless", how can ZBLJ's Fox pull a car, or his entire vehicle collection?

Yes And you know how many U/joints or 8 tooth gears fox broke? Exactly zero.

[Saberwing40k]

:sceptic: UGH... is their anything that could be done to increase the voltage?

I'm sorry to say, but it feels like you're not looking for advice, but to validate your own bad idea. It just feels like you're not following what all of us have said so far. Also, if you post pictures, that will let us help you more. Also, even XL motors have trouble moving a vehicle if they are attached directly to the wheels.

[aminnich]

Just so that everyone is on the same page as I am. I want a power functions/RC/Homemade motor set up that has torque and speed. Currently my truck is running 2 XL motors and is crawling. So the XL motors move all the weight, but I want it to move faster. I understand using a brushless RC motor will just destroy any LEGO in its path.

As whole new idea, what would happen if the voltage was from the battery box was increased?

[Saberwing40k]

You can slave two battery boxes together, and power the motors like that, but, Lego motors are designed to operate and 9 volts, and if that is exceeded, the motor would start frying.

[Blakbird]

You are not going to get speed from a heavy Technic model, it is as simple as that. There have been a couple of builders who have optimized a model to get speed, but if you look at those models they have NO structure; they are just motors and wheels. Every heavy model tends to be pretty slow, at least compared to anything R/C.

You can't have everything at once. Dan Goldin's "Faster, Better, Cheaper" didn't work either.

[Saberwing40k]

You are not going to get speed from a heavy Technic model, it is as simple as that. There have been a couple of builders who have optimized a model to get speed, but if you look at those models they have NO structure; they are just motors and wheels. Every heavy model tends to be pretty slow, at least compared to anything R/C.

You can't have everything at once. Dan Goldin's "Faster, Better, Cheaper" didn't work either.

You're absolutely right. Every Lego model has a certain level of compromise in it. And one of those is between weight, and speed. If it's a heavy model, it will not go fast.

[Corvette3]

Did he say he wants to pull a trailer with a 42030 on it? even trucks in real life pulling heavy machinery are aggressively slow.