Motor Comparison

[Burf2000]

I thinking of building a second Robot (see George) and so I always thought that the XL motor was the most powerful one available

Looking at http://www.philohome.com/motors/motorcomp.htm , is it the NXT motors?

What motor is the best to use for pure strength even if I need to gear it down?

[backbone]

What motor is the best to use for pure strength even if I need to gear it down?

Power Functions XL definitely

[Sariel]

NXT motors, definitely.

[Burf2000]

NXT motors, definitely.

So your saying NXT motors are stronger than XL remembering that (if I remember) NXT run at around 9v and on a rechargeable, XL run at 7.4

[DLuders]

I agree with Sariel -- the NXT Motor is the "most powerful". To compare "apples with apples", let's look at the data 1/3 of the way down Philo's Lego 9V Technic Motors Compared Characteristics webpage. At 9V, the NXT Motor stalls at 50 Newton-centimeters while the Power Functions (PF) XL Motor stalls at 40 N.cm. For torque, the NXT motor at 9V produces 16.7 N.cm while the PF XL Motor produces 14.5 N.cm.

Edited October 6, 2011 by DLuders

[Burf2000]

Ok to ask a silly question, is that physical motor or after gearing (e.g internal gearing)

[DLuders]

Philo bench-tested the physical (raw) motors without any external gearing. He compared "apples with apples", running the motors at the same voltage. If one were to run with different batteries (alkaline vs. rechargeables), the results will be different. Philo has numerous charts and graphs to determine your specific situation.

[Burf2000]

Philo bench-tested the physical (raw) motors without any external gearing. He compared "apples with apples", running the motors at the same voltage. If one were to run with different batteries (alkaline vs. rechargeables), the results will be different. Philo has numerous charts and graphs to determine your specific situation.

Sorry when you mean raw, are you referring to the metal motor inside the lego motor, or the lego motor output including internal gearing?

[DLuders]

The motor that you buy from The Lego Group is the "raw", unadulterated motor (just like you see in the two pictures I posted above). No additional gearing, no modifications -- just straight out of the retail bag.

You could always do your own testing if you don't believe us....

[Burf2000]

No sorry of course I trust you mate, I was just confused if he opened up the motor. Sorry

This post is going to save me some good money, thanks!!!

[yoraish]

That's interesting! I read over at Philo's Lego 9V Technic Motors Compared Characteristics that the efficiency of the XL motor is better than the NXT motor. Does that mean that its all-over abilities are better? Would using the XL motor (let's sat in a Trial Truck) be better in the power and speed aspects?

P.s. I saw that you wrote that the NXT motor is more powerful but this efficiency thing confuses me.

[Philo]

That's interesting! I read over at Philo's Lego 9V Technic Motors Compared Characteristics that the efficiency of the XL motor is better than the NXT motor. Does that mean that its all-over abilities are better? Would using the XL motor (let's sat in a Trial Truck) be better in the power and speed aspects?

P.s. I saw that you wrote that the NXT motor is more powerful but this efficiency thing confuses me.

Actually these two things are related. I believe that the core engines inside NXT and XL motors are the same, so using them at the same voltage, they should be able to deliver the same mechanical power. But the XL motor is less geared down internally (its output turns at 220 rpm vs. 170 RPM for NXT motor), so the available torque is a bit lower. And less gearing also means less friction, hence the slightly better efficiency. Note that if you need more external gearing to get the proper speed with faster XL motor, you may well end-up with a lower overal efficiency!!!

The down gearing of NXT motor and XL motor are also done very differently, with a long chain of gears and pinions while XL uses a two stages epicyclic gear train. This can also explain some efficiency difference.

[yoraish]

Thanks you very much!

[Burf2000]

Actually these two things are related. I believe that the core engines inside NXT and XL motors are the same, so using them at the same voltage, they should be able to deliver the same mechanical power. But the XL motor is less geared down internally (its output turns at 220 rpm vs. 170 RPM for NXT motor), so the available torque is a bit lower. And less gearing also means less friction, hence the slightly better efficiency. Note that if you need more external gearing to get the proper speed with faster XL motor, you may well end-up with a lower overal efficiency!!!

The down gearing of NXT motor and XL motor are also done very differently, with a long chain of gears and pinions while XL uses a two stages epicyclic gear train. This can also explain some efficiency difference.

Thanks so much, brilliant answer!

[allanp]

Looking at the comparison web page, it seems to me that the buggy motor is the most power as it delivers the most mechanical power (at 9 volts) of 2.38W as compared to the NXT (2.03) and the XL motor (2.21W). There is an even greater power difference at 7 volts. It has lower torque that the other two but a much higher speed meaning that with efficient gearing down (no worm gears but as few gearing down steps as possible, ie using only 8t to 40t gearing) you should get the most power, especially running at around 7 volts, from the RC buggy motor. However it is very power hungry, so be sure that you have the power source to run these motors at their full potencial. I find using the rc reciever unit (like the one that came with the RC buggy) with 6 rechargable 7.2V NiMH batteries works best, the power is increadable!

As an unrelated note, it's interesting that the old 9V ungeared motor delivers far more mechanical power than the geared motors that replaced it in 1997, and almost as much power as the PF-m motor. I always suspected that was the case!

[CP5670]

Yes, I've also found the RC motor to be the most powerful of all. It does eat through batteries quickly but you can run it off a train speed regulator or control center at the full 9V output. It has an odd shape but the high speed makes it more useful than the PF motors in many situations.

[SNIPE]

I would reccomend using the 12v motors alough it depends on the current really.

These dont have any gears inside and are not too big:

You will have to experiment with the power source but dont overload it otherwise you can burn the motor out

I have not seen any information on the internet about the amount of current these motors can handle so its a blind guess but, if you use the baterys.

If you can make 12 volts using batteries with a lego battery pack then that would be fine

I would use the newest batteries of a good maker availible, these now ones are very good.

Im really not so good at electronics to be honest but I know a bit.

Edited October 10, 2011 by SNIPE

[Burf2000]

I would reccomend using the 12v motors alough it depends on the current really.

These dont have any gears inside and are not too big:

You will have to experiment with the power source but dont overload it otherwise you can burn the motor out

I have not seen any information on the internet about the amount of current these motors can handle so its a blind guess but, if you use the baterys.

If you can make 12 volts using batteries with a lego battery pack then that would be fine

I would use the newest batteries of a good maker availible, these now ones are very good.

Im really not so good at electronics to be honest but I know a bit.

I have 1 of them, so are we saying they are better than an XL or NXT? How would you remote control them?

[SNIPE]

One of those is powerful, two is amazing , it depends on your model really, im not going to add two of them to a model that cant handle the power or just looks bad with them.

Yes this motor should be more powerful if you use the correct voltage (you will have to work out what batterie amount to use then get the correct lego be atery pack. using a lower amount means that the motor is not as powerful

However these do not have as much touque as some of the other motors from Lego, I am referring to speed and voltage.

If you want 2 or 4 axles from one motor you could try a 12v train motor, this is compact and means you dont have to have two motors OR add a differential or other gears.

You can use OHMs law to work out the current over the voltage and resistance.

voltage is not that important, its current that is what matters

[Tadej]

I agree the Electric RC Race Buggy Motor has the most mechanical power, it also has far better cooling than the XL or NXT motor and it has the smallest weight out of all three. So if you are looking for the strongest lego motor the RC motor wins hands down.

If you calculate the mechanical power to weight ratio, you can see that the RC motor is far ahead of the newer XL and NXT motors.

RC motor ... 4.33W/100g

XL motor ... 3.20W/100g

NXT motor ... 2.54W/100g

[Burf2000]

I am trying to use the other motors but XL just seem so much easier to mount. The RC / NXT have horrible mounts. Also the RC would need gearing down quite a bit

[CP5670]

That black 12V motor is pretty obscure and hard to come by. I think it only appeared in one supplementary set in 1980. I don't know if it's all that powerful either. I remember someone on Lugnet saying that it uses the same core as the 4.5V motor (which is pretty wimpy), but runs at a higher voltage. Maybe someone can compare it with the XL or RC motors? (with appropriate gear reduction, perhaps using those old gear blocks they had back then)