Toxic43

Small Powered Up Shunter with Pybricks control

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Hey Guys. I have been working on this project on and off since September of 2021. It is not my first MOC, but the first I care to show off here as I feel it is of a sufficient standard.

Small Powered Up Shunter - Pybricks Control

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The brief was originally a clone of @BrickPirate's Small PF Shunter, and I was indeed using Power Functions parts in the beginning. As there were no instructions or files available, I reverse engineered what I could and went on from there. Then I decided I didn't want the smallest shunter ever, just the smallest on my layout. I also liked a more rounded styling and incorporated that into the design. The colour choice was pretty much determined by what I had to hand after designing a previous MOC (An Emerald Night clone in dark azure with a custom tender and 2L PF motors in the boiler). The white was to somewhat hide the Powered Up Hub in plain sight. The side covers are shamelessly ripped straight from the aforementioned MOC. I put a couple of round times with holes on the front long hood to allow the hub's light and power switches to be accessible. Previously I was removing tiles to access the power switch. Now I can use an axle or whatever I have to hand to power on and off.

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But there was a little unused space in the rear electrical box hood, so I made a little starting pin which can hide inside if I'm ever anywhere without a technic axle to hand! It just pops in the hole, then a couple of presses later the hub is powered on and the Pybricks program is started. The pin then gets stowed in the rear again until it is time to switch off.

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I originally had this on PF with a train motor in place, which I decided was just too fast and uncontrollable for slow shunting work. So I decided to put in a Powered Up linear motor. The medium was the only one which was able to fit. The square profile helps with fitment as it is only connected to the chassis physically by the axle to the drive gears. Otherwise it just sort of rests in there. The sided and rear short hood hold it in place against the back of the PU Hub. The wiring is a mess as it has nowhere to go but up in this configuration, but there's no room for a Minifig, so not too much of a sacrifice.

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The drive software is actually from another Train Tech thread. Control your trains without smart device - with Pybricks courtesy of @Lok24  With the custom profile they designed I can now move around the layout at reasonable speed pulling a consist, and then with a press of the centre button on the PU controller, I can switch into super low speed shunting mode. The benefits of the linear motor here are that the Hub will control voltage to keep the loco moving at the desired speed according to load. Plus the gear drive sounds a little bit like cooling fans spinning so I can pretend a little bit!

Overall I'm quite happy with it for now, but I will probably end up changing out a few more things as time goes on. If I can get the motor mounted horizontally I may be able to get the drive line top a 4WD version, but I'm not holding out any hope. Poor little guy could really use 4WD! It can get stuck on points and does slip quite a bit if I load it up with too many pieces of rolling stock. I have custom traction bands on in place of the standard Lego ones for more grip but it does struggle for it sometimes.

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Thanks, hope you enjoy the pictures. I'll see if I can get a little running video together later on.

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1 minute ago, Lok24 said:

Hi @Toxic43

 

great small work! The idea with the hidden hub behind the doors is really funny!
 

 

Thanks for the compliment, although the idea of hiding the hub behind the doors dates all the way back to 2013 in the topic MOC: Small PF Shunter from @BrickPirate. I didn't come up with the idea on my own, merely appropriated the idea into my design. I can't take credit for it, although it is one of my favourite design features!

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I always enjoy small shunter moc:s. Thanks for sharing the technical details ! Well done , 👍🙌

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What an incredibly tidy loco! I always enjoy this off-centre-cab shunter style, and you've snuck the PU elements in incredibly neatly - I especially like the side doors and the cab window piece.

As for obtaining 4-wheel drive - why not try what the real thing often did, and add connecting rods? I think they look good on shunting engines, and since you've still got a continuous axle on the rear axle they should stay properly quartered.

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4 minutes ago, ColletArrow said:

What an incredibly tidy loco! I always enjoy this off-centre-cab shunter style, and you've snuck the PU elements in incredibly neatly - I especially like the side doors and the cab window piece.

As for obtaining 4-wheel drive - why not try what the real thing often did, and add connecting rods? I think they look good on shunting engines, and since you've still got a continuous axle on the rear axle they should stay properly quartered.

Now that is not a bad idea at all. I can't believe I didn't think of it! Thanks for the suggestion. I'll give it a try! It might just be the answer to my problems!

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That is all really ingenious and despite all the space saving measures to hide the motor and battery box it is a very attractive loco.  Well done!

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Tight space, but you made it work and look good. How you managed to get all the PUp in there is excellent. The color scheme is really nice too. It stands out as different than most items on the railroad, in a good way.

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really nice model! gives a very "cityish" feel. looks like something lego could do in a set.

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1 hour ago, XG BC said:

really nice model! gives a very "cityish" feel. looks like something lego could do in a set.

Thanks! This is part of the reason I built it so small. Lego hasn't produced anything of this size in quite a while. I'd love to see Lego's designers have a crack at something like this. A smaller shunting loco which runs at a slower speed with a nice set of rolling stock to shunt around and make up a consist. It'll never happen in my lifetime though, hence this!

I also put up a short clip of it in motion. I don't really have a track together that I'd be happy showing on camera right now, so it is on my desk/workbench. Which is also a mess, as per usual. Sorry about that!

 

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17 hours ago, ColletArrow said:

What an incredibly tidy loco! I always enjoy this off-centre-cab shunter style, and you've snuck the PU elements in incredibly neatly - I especially like the side doors and the cab window piece.

As for obtaining 4-wheel drive - why not try what the real thing often did, and add connecting rods? I think they look good on shunting engines, and since you've still got a continuous axle on the rear axle they should stay properly quartered.

So I tried the idea to add coupling rods, but I haven't been able to find a solution which works yet. Even the smallest Technic 1 x 2 liftarm parts are too large for the wheels and connect with the rails on the down stroke. I can't seem to find any working coupling rods done on the standard train wheels with axle hole. The larger train (Steam) wheels are no problem but these smaller ones are a real pain. If anyone has any feedback I'd appreciate it. 

I did have one idea to use the rubber bands on a couple of technic bushes each side. I may see how that works out but I'm not holding out hope for it. I think the Lego bands I have will be too small.

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OK. I tore it down and redesigned the drivetrain in my lunch break today.

I redesigned the drivetrain and the rear hood to accommodate the motor horizontally, as opposed to the vertical mounting before. It uses a 12 tooth bevel idler gear between the 20 tooth bevel gear which will be connected to the motor and the 12 tooth bevel gear which connects to the wheel drivetrain below.

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A better shot of the underside showing the final drive to the wheels. All 4 this time. Hopefully no more slipping!

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And a view inside from the top.

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I have it mostly reassembled, but wouldn't you know it I'm missing a 20 tooth bevel gear. I probably have like 20 or so, but can I find one? Once I get the paid at the end of the month I will put in a Bricklink order with the 20t included so I can finish it!

I'll post an update once it can move under its own power again!

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That video looks great, I do enjoy the slower speed you get from a motor and gearbox compared to the standard train motor.

4 hours ago, Toxic43 said:

So I tried the idea to add coupling rods, but I haven't been able to find a solution which works yet. Even the smallest Technic 1 x 2 liftarm parts are too large for the wheels and connect with the rails on the down stroke. I can't seem to find any working coupling rods done on the standard train wheels with axle hole. The larger train (Steam) wheels are no problem but these smaller ones are a real pain. If anyone has any feedback I'd appreciate it. 

I did have one idea to use the rubber bands on a couple of technic bushes each side. I may see how that works out but I'm not holding out hope for it. I think the Lego bands I have will be too small.

May I bring your attention to the part Technic Engine Crankshaft? It has a 0.5stud offset, perfect for adding coupling rods to standard-size train wheels. I used them on my own 0-4-0 shunter, although I'm not claiming it's my idea by any means! Mine was on standard train motor, together with 2x 7m half liftarms and 4x half bushings:

Word of warning: the train wheels are a little wider than a standard half lift-arm. This means that the remaining bit of 6m axle isn't quite enough to hold onto the crankshaft securely; I often use blu-tack to help keep the crankshafts in place! You'll also want to keep the bushings a little loose to not cause too much friction.

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@Toxic43

This is a fantastic design! Wow.

You have 1) all the power of the linear motor and b) the power of PyBricks - and managed to assemble all that into this beautiful "small" (and at the same time so "big") engine. Congratulations! Hope you'll get your hands on the missing gears sooner than later!

One totally marginal thing: Some of my trains operate their powered bogies on the same principle. What I saw when serious torque is required (slopes, friction) that the 1x2 technic brick (and you secured that additionally with the 2x2 plate with holes) was sometimes popping off.

I used this to get around that issue:

gearspart1.jpg   gearspart2.jpg

(just did draw it up in MLCAD for your geometry) - colors don't mean anything to me but "contrasting" :pir-wink:

Would that also work for your design, or is that "gear framing" simply not required?

I really enjoy seeing your progress.

Thanks a lot for sharing!!!

Best
Thorsten

P.S.: This also demonstrates the power of PoweredUp either using PyBricks or TLGs PoweredUp app using "set speed" :pir-huzzah2:)

Edited by Toastie
Present tense, past tense ... lalala

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11 hours ago, Toastie said:

@Toxic43

This is a fantastic design! Wow.

You have 1) all the power of the linear motor and b) the power of PyBricks - and managed to assemble all that into this beautiful "small" (and at the same time so "big") engine. Congratulations! Hope you'll get your hands on the missing gears sooner than later!

One totally marginal thing: Some of my trains operate their powered bogies on the same principle. What I saw when serious torque is required (slopes, friction) that the 1x2 technic brick (and you secured that additionally with the 2x2 plate with holes) was sometimes popping off.

I used this to get around that issue:

gearspart1.jpg   gearspart2.jpg

(just did draw it up in MLCAD for your geometry) - colors don't mean anything to me but "contrasting" :pir-wink:

Would that also work for your design, or is that "gear framing" simply not required?

I really enjoy seeing your progress.

Thanks a lot for sharing!!!

Best
Thorsten

P.S.: This also demonstrates the power of PoweredUp either using PyBricks or TLGs PoweredUp app using "set speed" :pir-huzzah2:)

@Toastie Thorsten, thank you very much for the CAD drawings! I really appreciate it! The original driveline had these frames built into it but I was put off because I only had one of the larger frames in LBG and none of the smaller ones. I have now ordered all the parts including the frames in black. Your drawing convinced me! I think it'll be a lot stronger overall with this design. I completely omitted bushings on the axles too, which is strange because all my other high torque MOCs have them. The previous steamer I built with 2x L motors had a habit of spitting out gears before I reinforced the driveline with bushings to stop them having anywhere to go. Thanks for the suggestion. I will add them as per the drawing. I did notice some binding in the idler gear too, so I rebuilt that with 2x technic bricks and an axle 3L with stop to prevent it from having anywhere to slide to. I'll probably add a bit more reinforcement around that area too just to make sure no gears have anywhere to slide to. At least I don't have to worry about the 20 tooth as it will be butted up securely against the back of the PU hub!

Many thanks again for the CAD drawings! I'll make sure to post another few pictures once the Bricklink orders are in and I have it all assembled. I'll be sure to get an updated running video too. This time on a track. Now that it is 4WD I want to test exactly how much it can pull!

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2 minutes ago, Pybricks said:

This looks fantastic!

Thanks very much! The remaining parts as suggested above arrived today, but wouldn't you know it, now I have COVID, so now I don't have the energy to fit them. Once I get my strength back I'll get the parts installed and post a running video. 

Presently it runs fine forwards, but switching to reverse will pop the transmission gears apart as all there is holding it together is a couple of studded connections. With the Technic frames I should be able to change direction without issue. 

Overall, it's just me taking a bunch of ideas from elsewhere and other people and putting them all together with my own spin. I couldn't have got to this part without all the others previously mentioned in this thread. 

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2 hours ago, Toxic43 said:

I couldn't have got to this part without all the others previously mentioned in this thread.

First of all: All the very best for your recovery and tell that Covid virus to go to hell.

Secondly: Original post, line 1:

On 2/8/2022 at 3:34 PM, Toxic43 said:

Hey Guys. I have been working on this project on and off since September of 2021.

You had the design already 99.99% done! I'd round that off to 100% So everything else in this thread is just that: Ideas and experiences tossed around.

This is a 100% genuine shunter, you made. I really like it, as said.

All the best,
Thorsten

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7 hours ago, Toxic43 said:

Thanks very much! The remaining parts as suggested above arrived today, but wouldn't you know it, now I have COVID, so now I don't have the energy to fit them. Once I get my strength back I'll get the parts installed and post a running video. 

Presently it runs fine forwards, but switching to reverse will pop the transmission gears apart as all there is holding it together is a couple of studded connections. With the Technic frames I should be able to change direction without issue. 

Overall, it's just me taking a bunch of ideas from elsewhere and other people and putting them all together with my own spin. I couldn't have got to this part without all the others previously mentioned in this thread. 

i hope youll get better. tell covid to go f... itself in the corner.

Edited by XG BC

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34 minutes ago, ivanlan9 said:

Might be better with a 9v motor. ...

Ha! No! :pir-huzzah2:

Reason: (first have another beer for me being a "smart" megablocks: :pir-huzzah2:) Because:

On 2/8/2022 at 3:34 PM, Toxic43 said:

The benefits of the linear motor here are that the Hub will control voltage to keep the loco moving at the desired speed according to load.

The hub with a PUb tacho motor attached will keep the "demanded" >speed< (lets say 5% of full speed) constant, even when it has to put out 100% power (i.e. 100% PWM cycle).

A 9V motor can never do that; in contrast.

All the best,
Thorsten. Wait: :pir-huzzah2:

Edit: At what f*ing rank is a*s not automatically translated to megablocks??? What is megablocks anyway? mega = 10E6; blocks = bricks. So is one a*s = 10E6 bricks?

Edited by Toastie

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