Motor Upgrade

[Boxerlego]

Hello, I have just took apart the XL motor to look at some things and see if it was possible to put the XL planetary gear reduction on another motor. The goal is to get more Rpm (@9v) out of the planetary gear reduction by attaching it to another motor. I have setup this tread to document this attempt.

I did not want to break the clips off the case so dismantling the XL motor was tough. Currently the motor shaft is a little bigger than the XL motor shaft size.

Is there any technical information on the motor that is in the XL.

[allanp]

I don't have any technical data on the motor but I have messed with it to make it faster. I basically removed the outer ring gear and glued up all the remaining gears, effectively removing all the internal gearing down whilst retaining the look and the orange axle hole. Whilst it looks identical (aside from some scratches obtained from taking it apart), as you can imagine it now spins very fast, faster than the old 9v ungeared motor and still has more torque than that motor to. Enough speed to spin some tyres of it's wheels due to centrifugal force causing the tyre to expand. It's overall mechanical power output remains about the same as before, more speed, less torque. It's now much more useful. I can motorise anything that requires the power of an XL motor with it with the added benefit of being able to protect gear trains using clutch gears (previously useless with an XL motor) or even a belt drive, which is alot quiter than the standard XL motor. It drives engines at very high speeds like you would get in real life (they even begin to sound real at that speed) and there's the added joy of building all the needed gear trains and gets rid of the kind of boring over simplification as seen sets like the bulldozer whose gear trains were far to mechanicly simple for my taste. Now i've just got to convice my purist self to use the darned thing

[Boxerlego]

Since I have no technical data sheet on the motor I resorted to measuring the motor shaft's diameter and it is 2.0mm. Along with the shaft size I have made some progress with determining the RPM on the motor shaft. I started by calculating the planetary gear ratio which is 1:25. When you multiply the 200 RPM output on the XL motor by 25 is 5000 and that is the RPM for the motor shaft. Now that I have some numbers on the motor I am able to select a motor that could potentially double the output on the planetary gearbox at 9 volts.

@allanp: By your method of making it faster the gear ratio becomes 1:5. Have you tested the RPMs your modified XL motor, was it around 1000 RPM.

@DLuders: Thanks for that link. That is the easy way opening the XL motor.

[DLuders]

@ Boxerlego: The technical data sheet you seek for the Lego Power Functions XL Motor is on this Powerfunctions.Lego.com webpage (which leads to this PDF Element Spec for the XL Motor).

[Boxerlego]

@DLuders: Awesome! After looking at that data sheet I wonder if there will be a V2 for the XL motor.

Instructions on how to open the XL motor. With out breaking the clips off. If you are trying to upgrade the XL motor just break the clips off.

First dig out one side of the clips with a small flat head screw driver... On the other side dig some of the clip out but leave some on there so the case can lock together... Watch the begging part of my XL motor video and try to open the motor like that...

You will need to cut three 9mm length pegs from the tooth pick...

--------

Wrap about a 0.4mm of the end on the peg with a small strip of tape.. Do not wrap the entire peg with tape because we want some of the peg to slide in on the other half of the planetary set...It is important that the tape is wrap around the peg in the right spot other wise you wont here it snap shut... It does not matter how much excess tape you have at the end that will be some of that will be cut off... The tape layer should not be thick two or three turn is enough...

Make sure the pegs fit firm and secure and do not exceed the top of the plate...

Make sure you hear it snap shut... If you do not hear it snap shut then the plantar set are not sitting even together.

Edited April 13, 2013 by Boxerlego

[allanp]

@allanp: By your method of making it faster the gear ratio becomes 1:5. Have you tested the RPMs your modified XL motor, was it around 1000 RPM.

Nope, by boxerlegos cool looking method you get a 1:5* ratio. I glued all the gears together and removed the outer drive gear, the gear ratio is now 1:1. I haven't done any proper testing but I can say it is definitely faster than the old ungeared 9v motor which spins at roughly 4200 rpm by quite alot.

*BTW, do you know that when you are working out the gear ratio of a planetary gear system such as this, you have to divide the number of teeth on the outer ring gear by the number of teeth on the inner sun gear (looks to equal about 5) and then add 1. This means that each stage actually has a 6:1 ratio, resulting in a final reduction of 36:1. Which means if the output is spinning at 200 rpm, the input is spinning at 7200 rpm. I would say my modified motor is about that!

Edited January 15, 2013 by allanp

[Boxerlego]

@allanp Thanks for correcting me on the planetary gear ratio. Appears that I have low battery power. The XL "motor" has some serious power behind that speed for its compact size. I have not tested the XL motor out with the 6:1 ratio yet. I will sure do some test on that before anything else happens here.

[allanp]

Doh! you are boxerlego, silly me haha!

[Boxerlego]

After testing out the XL motor with the 6:1 gear I took apart another XL motor . I have tested both versions of the IR receiver powering this XL motor and with additional gear reduction a single modified XL motor can be pretty fast on four wheels, still not quick as the 5292 buggy motor. I have tried powering this motor with the combined voltage of two battery boxes but two AA battery boxes are to heavy for the single XL "motor". Additionally I have come up with a easy way to open the XL motor case and detailed walkthrough on how to connect the two planetary set together.

[jadedomg]

Thanks for the info, I might have to buy some xl motors from S&H and modify them if they work almost as good as the old buggy motor :)

[allanp]

They will never be close to being as good as the buggy motor. You can increase the speed but you lose torque leaving you with (if you do it well) the exact same total power output as you had before, which is about half that of the buggy motor. Still I much prefer it having no internal gearing, constructing the mechanics yourself with your own external gearing is what technic should be about.

[Boxerlego]

Here is the gear train that was used with the modified XL motor in the test. Note that the portal hubs were at a 1:1 ratio.

This was made here http://gears.sariel.pl/

Thanks for the info, I might have to buy some xl motors from S&H and modify them if they work almost as good as the old buggy motor :)

@jadedomg: Your welcome. Though the xl motor will not be as fast as the buggy motor, you will get a boost in RPM out of the xl motor by doing this.

They will never be close to being as good as the buggy motor. You can increase the speed but you lose torque leaving you with (if you do it well) the exact same total power output as you had before, which is about half that of the buggy motor. Still I much prefer it having no internal gearing, constructing the mechanics yourself with your own external gearing is what technic should be about.

@allanp: I agree that they will never be as fast as the buggy motor. However the xl motor takes considerably less amount of current to run compared to the buggy motor.

Edited April 12, 2013 by Boxerlego

[Boxerlego]

I took off the gear on the XL motor and there is a youtube video on how it was done. Not my video but that is how I did it. I did not have the precision of the torch lighter to get the gear off as seen in the video. What I used was a bulky propane torch which got the entire motor hot because of how big the motor was. The motor still works even though it got hot to the touch. Also I had the Motor upside down in the vise so that the pinion gear will fall down under gravity.

Edited January 19, 2013 by Boxerlego

[Kierna]

Would it be possible to put two or 3 XL electric motors on one shaft in one XL motor housing?

There's definately room, but I don't know if it's easy to change the steel centre shaft.

[Boxerlego]

Would it be possible to put two or 3 XL electric motors on one shaft in one XL motor housing?

There's definately room, but I don't know if it's easy to change the steel centre shaft.

@Kierna: No it is not possible. If the XL motor case was one stud bigger length wise, then you could put a bigger motor inside but not two motors stack on one shaft. I dont know how to change the steel shaft or even know if you could change the steel shaft.

Edited January 19, 2013 by Boxerlego

[Boxerlego]

I have put the 12T Pinion gear from the XL "motor" on the new motor shaft. I heated up the pinion gear glowing hot and slid the cool motor shaft directly on it real quick. I had two metal spacer magnetically stuck on the motor to act as a barrier so that when I quickly slide the motor on the glowing brass pinion gear it will stop before the gear comes near the motor creating a space. I still am figuring out how to lock the gear box to the motor.

Edited January 19, 2013 by Boxerlego

[allanp]

Nice work so far, do you have any specs on the new internal motor you are using?

[kieran]

Would also like to know what spec motor is going in

[Boxerlego]

Here is some technical data on the motor below. I have power the motor through both v1,v2 IR receivers along with the AA reachable batteries in the 9v battery box and got around 1500 RPM (6:1 internal gear ratio) on the 5206 Speed computer on both v1,v2 IR receivers.

[Hopey]

So have you done any empirical comparisons of the torque? I'm now quite sure how to calculate it.

Based on stalled torque of 393g.cm = 3.85 N.cm ungeared at 13000rpm. With the original gearing (for comparison) of 1:36, this would be (ignoring losses) about 140 N.cm at 360rpm, compared to the original XL motor's 40 N.cm at 220rpm.

I'm not sure how accurate stalled torque is as a measure, but that looks pretty good.

[Boxerlego]

Here is another technical data sheet for the motor.

[Boxerlego]

So have you done any empirical comparisons of the torque? I'm now quite sure how to calculate it.

Based on stalled torque of 393g.cm = 3.85 N.cm ungeared at 13000rpm. With the original gearing (for comparison) of 1:36, this would be (ignoring losses) about 140 N.cm at 360rpm, compared to the original XL motor's 40 N.cm at 220rpm.

I'm not sure how accurate stalled torque is as a measure, but that looks pretty good.

I have not done any empirical comparisons on the torque. So far the motor is half way completed. When the motor is together I will see if everything will work together under a load. That is a interesting comparison you made between the XL "motor" and this motor. I have done a simple torque test with me holding down the drive shaft in between my fingers and seeing if either one of the v1,v2 IR receiver will shut down power to the motor but that did not last for 10 seconds because the axle was hard to hold on to.

Edited January 21, 2013 by Boxerlego

[allanp]

"power output: 5.71 Watts"

NIIIIIICE!

[Hopey]

How did you choose this motor?

There's a whole range of them at the mabuchi website.

Including this one: 50mm x 36mm excluding shaft, no-load rpm 23,400 at 9.6V draws 1.4A. Stalled torque 21 N.cm draws 57A (!). Draws 9.5A at max efficiency, outputting 65W. About US$10.

Go big or go home, I say

[Paul202]

It would be very awesome if the RPM of the motor sped up AND the torque stayed the same. I could see numerous applications if this is the case.