MOD - 12 volt wheels with axle hole for Power Functions motor

[Paperinik77pk]

 

Hi all, 

since 7777 book came out, I've always wanted to integrate Trains and Technic worlds. Back in the 80's the problem was the complete lack of train wheels with a Technic axle hole. It was solved with RC trains a lot of years later.

Therefore, I can convert a 9v train to PF without too many problems (aesthetically speaking). But for 12V trains it is different. Wheels are made in a specific way, they have the hole for connecting rods, they're more "fat" than RC/PF wheels. 

Frankly, I do not like 12V trains converted to 9V/PF standard bogies. But I like the PF motor, its speed, the possibility to increase speed gradually...and the fact it keeps the central hole for third wheel.

So, in these years I repaired a lot of 12V motors...and some were really in bad shape. Look at the right wheel, it is completely destroyed inside.

So I decided to try to implement my solution to connect standard, intact 12V wheels to technic axleholes (which I do not list here, since it was not satisfying).

First, I got a standard Technic bush, and cut it a bit. Then I put it inside the damaged wheel hole. It fits fine, but needs to be glued.

Once glued, it is time for some testing. 

The 6-long axle goes right in - but the red ring coming out from the wheel is too thick. So I prepared another wheel (gray bush). This time I cut the bush a bit shorter and fits right.

The 5.5 axle is perfect , so I'll need to cut two 6-long axles to the right lenght.

And this is the result - this is my 7740 no°3, totally converted to PF.

It works fine, but as you all can imagine, it is all made by hand and bushes are not machinery-centered. Therefore the locomotive is not stable as I would like. For the moment, better than nothing! 

 

 

Edited January 29, 2018 by Paperinik77pk
typo

[Paperinik77pk]

Now I come to the interesting part...which could involve all people interested in this solution. I started slowly to learn how to use a free CAD software on internet to prepare a more "professional", 3D-printable wheel for all Eurobricks members interested in 12V world. 

But I'm at the very beginning. Anyone wanting to participate (and more able with CAD design - I am a complete newbie , still learning) is obviously welcome!  

[3797]

That's something that I wanted to do years ago. Only problem was and still is the pricing of the Form 2. Even the Moai is quite expensive, still.

[Paperinik77pk]

I think I will buy one economic printer, there are some used in good condition for good prices.

For the first print I'll go in a store offering 3d printing services, in order to understand if it's feasible (before spending 250 Euros for the printer)  

[LEGO Train 12 Volts]

What a fantastic work!

Do you think to put also the third wheel axle?

[dr_spock]

You can get a DIY 3D printer kit from China very inexpensively.  But it requires effort to build it, tweak it, and learn to use it.  It is a lot of fun if you're so inclined for DIY.

Another option might be to epoxy the Technic axle into the wheel. 

[Paperinik77pk]

13 hours ago, LEGO Train 12 Volts said:

What a fantastic work!

Do you think to put also the third wheel axle?

Hi! 

It is quite simple to fit the third wheel inside the PF motor, the only thing needed is to open the motor case (8 torx screws if I remember well) and use a small plastic lid to lock the standard 3rd wheel (no other modifications or glue needed) in place, leaving it a bit loose in order to emulate the "suspension".  It is more complicated to explain in words...I'll post some photos this evening to show how it works. it is very simple and can be reversed at any time. This photo is from the first version (old axles), but third wheel lock system is always the same 

 

 

 

 

 

 

[Paperinik77pk]

9 hours ago, dr_spock said:

You can get a DIY 3D printer kit from China very inexpensively.  But it requires effort to build it, tweak it, and learn to use it.  It is a lot of fun if you're so inclined for DIY.

Another option might be to epoxy the Technic axle into the wheel. 

Hi! Thanks for your suggestion! I saw these printers, and the building part seems nice to me. For the moment I do not know very much about 3D printers and I'm looking a bit around.  For example I found for the same price an M3D used  printer directly here in Milan - it is smaller and it seems good for what I've to do...we'll see, my birthday is coming...

Regarding epoxy glue: I built a kind of assembly tool (with Technic parts) to glue together and align wheel and axle, but for some reason the result was a jumpin' 7740!   So I tried the bush solution and it solved a bit the alignment part. 

[Paperinik77pk]

Hi all, some pictures showing how I locked the third central wheel inside PF Motor:

First of all, open the PF motor. Get a plastic...well i do not know how this is called in English - I'll call it "strip"  - black is better,

Cut a little part of "the strip" (I took off the first two centimeters) - now look at the central hole - there's a little space where you can insert the little plastic lid. It will not lock, but should stay in place.

Now cut it to 8mm (remove the pointed tip) and insert it into the motor as you did before.

Try to put in place the third wheel, if it is sits higher than the two side wheels (you have to work with the motor in bottom-up position) you'll need to shorten the plastic lid a bit  otherwise you won't get any traction. Try to simulate the "suspension" the central wheel has in the 12v motor.

Close the motor with only two screws and try it on a 12v train. It must run without any slipping. If you see the train not working fine, adjust again the lid lenght and retry. it's a trial and error process, but it does not involve parts modication and it is completely reversable.

If you find a better solution, or you have suggestions, they are always welcome! 

Edited January 31, 2018 by Paperinik77pk

[Paperinik77pk]

Hi all,

after literally months from the first post, I finally got the chance to make some progress on the creation of the 12v wheels. I finally bought (as a birthday gift) a 3D printer. It is an economical, entry point version, just what I needed to learn the basics

There's a website (www.thingiverse.com) were a lot of custom models are created by people. And there are a lot of interesting Lego parts (including modified tracks and bricks).

There's also a model of a Lego train wheel with Technic axle hole, but it is not so precise - and the technic hole seems to be a bit narrow. I printed it but it was not good to me. I therefore proceeded with my original design made on Tinkercad, simplified a bit to speed up the printing time.

Here below, the printing in process of my model (these 3d printers are amazing!). The wheel is printed in PLA material, but the printer can also manage ABS.

The above picture shows how the wheels came out with an intermediate level opf print quality (14 minutes per wheel). As you can see, there are no decorations and the 12v coupling rod hole is missing.

Here below, the test with original rubber bands in place:

It seems the wheel borders are a bit too small, for this reason I'll probably make them a bit bigger. The locomotive works fine and the PF motor is as fast as the 12v one (just a bit more silent without the typical 12v noise of electric contacts on the electrified third rail) - I will post a video made running the 7740 in 1980 configuration (7740+7820) on my 12v test track

The central wheel is now mounted in another way, which I think better and more solid  than the first one I show in the first posts. It can work with RC/PF original wheels too. In order to mount the wheels we've to open the motor, put the modified parts in the two central holes, and close the motor housing.

First, we've to modify this half axle with pin. use a sharp cutter, it will be easier and faster.

Cut away the pin part, you have to keep the axle part and that plastic ring, which is too wide and must be narrowed a bit to allow the wheel to spin freely. The modified part must be inserted on the bottom part of the motor housing (do not modify the motor housing, it is not needed).

As you can see, the gray part is touching a small black plate in the motor housing. In this moment it is crucial to perform some adjustments to the gray ring - slice it (or sandpaper it) until it allows a smooth movement. It is a 2-minutes work - nothing difficult.

Create another modified axle/pin, put it on the other side of the motor housing and reassemble the motor. Insert the wheels, and job is done !!!

And now, to the next step - holes for 12V coupling rods!!!

Bye!!!

Davide

 

[Selander]

Here's a 2011/2012 tutorial for adding a third wheel to a PF train motor.

[Paperinik77pk]

Thanks! I did not know about that tutorial  ...weĺl at least the solution seems correct! I think also axles 3l and 4l with stop can be used (they only must be cut the right lenght and painted black) 

[Paperinik77pk]

Hi all,

after a bit of work on Tinkercad I finally managed to achieve a better design of the 12v wheel - It is not 100% faithful to the original, but dimensions are now correct (I confirm that the border was too small by 2mm)

I recolored the two objects in black and red just to give an idea.

The coupling rod hole was a bit difficult to do (for my limited skills with the CAD software), but at the end I managed to find a solution to replicate it.

It is hard to explain - it is composed by two cylindrical holes: the smaller one is the one we can see on top of wheel . Coupling rod pin goes in there. But the Lego coupling rod pin has a sort of clip, so I needed to create a larger cylinder under the first one to allow the clip to expand and to keep the coupling rod in place. This is the final product:

And now some testing - this time I got my old faithful 7715. After the removal of the 4,5v motor (gray cables can still be seen in the pictures), I installed the PF motor, put an original 12v central wheel and two 12v 3D printed wheels.

Coupling rods fit nicely and work even at high speed.

For the moment wheels work fine, but design can be vastly improved. The important thing for me was to keep the 12v style -  not only on modern trains like the 7740  but also on steamers. I'm quite happy - it is something I want to do since years.

Hope you like it!

Bye, Davide

 

P.S.

Since I had to open again the motor to align the axles (coupling holes must be in the same position), I tried the axle with stop solution to keep in place the third wheel - it works better than modified pins (less friction), but the bad part is that you always need to open the motor. The only effort in this case is to cut the axle with stop part.

 

 

 

Edited May 5, 2018 by Paperinik77pk

[moustic]

would it be possible to share your .stl file in order to try printing these beautiful wheels ? 

Edited June 6, 2018 by moustic

[JopieK]

Or maybe put it in the Shapeways shop so we could order it from there :) (designers then get also some small revenue out of it).

[moustic]

4 hours ago, JopieK said:

Or maybe but it in the Shapeways shop so we could order it from there :) (designers then get also some small revenue out of it).

Obvious !  I would pay for that ! 

 

[Paperinik77pk]

Hi all, here it is the .stl file!

I prefer to keep it free, for all who want to contribute to avoid 9v wheels on 12v trains 

https://www.tinkercad.com/things/l55F9eeD8db#/

Feel free to modify it as you like!  

Ciao!

Davide

 

[retuow]

hi all, 

This is the solution I have been waiting for! Thanks for sharing it Davide! I had the wheels printed at two different (internet)shops using 3dhub, but unfortunately I could not fit the technic axle into the wheels they printed. The holes are too narrow for the axles. Using brutal forces resulted in a twisted axle :-) 

Can anyone recommend a printing service that has successfully printed these wheels? 

Any help would be appreciated!

regards,

Wouter. 

[LEGO Train 12 Volts]

Just one word: AWESOME!

[mrseven]

On 6/7/2018 at 9:36 PM, Paperinik77pk said:

Hi all, here it is the .stl file!

I prefer to keep it free, for all who want to contribute to avoid 9v wheels on 12v trains 

https://www.tinkercad.com/things/l55F9eeD8db#/

Feel free to modify it as you like!  

Ciao!

Davide

 

First of all I apriciate this effort in constructing this wheel. Thinkercad allows you to pass this design to a 3D Printing factory. So I imported this design to my acount in shapeways. And I ordered them.. but istead receiving them from shapeways, I got a response: NOT PRINTABLE. Why? The wollthickness doesn't meet with their specifications.

After a view sleepless nights I came to the conlusion to construct them newly. Finaly I uploaded a printable design and got some wheels.

Now it is time to share it.

https://www.shapeways.com/model/3dtools/7898164/0/76?key=84d31c95d5427c432fdc35440a427196

This design is still in a beta stage. So I need Feedback to improve it.

 

Andreas