Side rod/ valve gear advice.

[Modeltrainman]

Hi, everyone! Building a 2-4-0 locomotive, and it's so small and cramped that I shoved the Powered Up train  motor underneath the cab, and put my driving wheels under there.(Official Emerald Night wheels), my problem is, the LEGO curves are tight, and I feel like I should let the motor swivel. How should I do the side rods? My prototype. I COULD let the tender push, but I prefer actually letting the locomotive pull.

[Roadmonkeytj]

@zephyr1934 came up with a neat solution for the lone ranger train that might work for you ... If Its not posted before I get home tonight I will try to find the link for you.

[Modeltrainman]

Just so there's more info, I was hoping to have side rods, and still let what needs to swivel for steering.. 

[Roadmonkeytj]

Have a gander through THIS GALLERY and see if that or an adaptation of that might work

And if you like those side rods get a hold of zephyr1934 to buy some.

[M_slug357]

@Modeltrainman if anything, the piston housing for the siderods should be attached to whatever part of the frame that your driving wheels are... 

[Modeltrainman]

@m_slug to the  motor itself then? The way I have it set up is the cab sits on top of the Technic plates with holes, motor is attached to those, cylinders are underneath the front of the boiler. Front truck under that.

[M_slug357]

@Modeltrainman Yes, that sounds about right. Just make sure that the piston housing swings clear of your leading wheels, and you should be good to go!

Oh, and feel free to post some pics of your progress so that others might chime in with some of their tips & tricks!

[Glenn Holland]

Help me better understand: why do you feel the motor needs to have the freedom to rotate? Casey Jr., as shown in your reference, is a 2-4-0, which is nearly the smallest wheelbase possible for a steam locomotive. You could almost get away with all six wheels being fixed to a rigid frame, but for the sake of ease, I think you'll want to allow the pilot wheels to move.

As @M_slug357 mentioned above, you'll want your cylinders to be rigidly attached to your train motor, and leave room for the pilot wheels to swing around/beneath them. This will save you the headache of having to articulate your connecting rods.

Once you arrive at a solution you're happy with, you'll want to measure the distances between your two driving wheels and then from the main driver to your cylinder. You should need a 7-stud long rod to connect the wheels together.

The distance to the cylinder depends on which axle you want to have as your main; the front or the rear. Keep in mind you'll need at least three studs worth of travel built in, so your main rod doesn't collide with your cylinder, or fall off, and drag along the ground. It will depend on your design. Zephyr1934 can help you out once you know what you need.

[Modeltrainman]

@Glenn Holland I feel like the motor should rotate because I don't want any derailments. Um… here's an early render showing what I'm aiming for. Without the rods, but it will give an idea. https://1drv.ms/u/s!Akmnn7PtxrDah7dkRiYL_FXjSRo78g?e=XYMUtB And, I can't use non LEGO parts for the valve gear, for a very important reason.

Edited July 23, 2019 by Modeltrainman

[zephyr1934]

Hey there,

 indeed, if you want a pretty good go-by, the instructions for either the Lone Ranger train or Harry Potter train MODs would be a promising start. You could literally just drop the rear axle on the Lone Ranger and you would have the configuration you need. I might have an IDEA why you need pure Lego parts, but you could easily replace the rods with technic beams. Well, you might want to move the cylinders one stud closer to the wheels on the Lone Ranger since the half wide beams only go to 7, but that would probably fit well with your prototype... though I don't know if the technic beams offer enough "play" to get it to line up, so it would take a little trial and error to make sure it works to your satisfaction.

 

Another option would be to copy the rod mechanism from the Harry Potter train (connecting rods but no side rods) or one of the non-city steam trains that lego released over the past few years (side rods, but no connecting rods). Here is a thread with some clever ideas for adding rods to the holiday train.

 In any event, think of your locomotive as being just another piece of rolling stock, it is long enough that something needs to turn on a truck or otherwise bend. Your proposal is to have the motor rotate under the locomotive, you could do that, but you would probably have to do away with the connecting rods (still having quartered side rods on the wheels). I think that is how they did it on the Toy Story train. However, as the two images above show, it is not too hard to have the drive wheels rigidly fixed to the cab and boiler, then have the pilot twist (HP) or bend (LR).

 

Hope this helps.

[Modeltrainman]

@zephyr1934Thank you for your response! I've seen your work online, and between your work and others' I'm often intimidated, but for Casey Jr., I decided I  really have to do the best job I possibly can(he's a favorite character of mine, and LEGO has already done phenomenal work on Toy Story, and my Up house is trying to gather support...) So, thank you for your response, and help! (And yes, your IDEA was correct. I want to see this model bring joy to others, possibly.)So, it was time to stop building in a vacuum...  I'm just glad to hear that fixing the motor won't break it, should it come to that. Once my 1x7s are here, and I have it working, I'll definitely have to share some pictures! EDIT: Also, your rods are very well done, but due to rules...;)

Edited July 24, 2019 by Modeltrainman

[Modeltrainman]

So, some questions about side rods/valve gear, and the PU motors. I noticed that when the train moves into a curve the light on the Hub blinks. Is that normal? Am I overloading anything? Also, I'm using 7 stud thin beams to connect the driving wheels. How long should the one that feeds back to the cylinder be? Is there a way to measure? Don't want to burn up my motor, and I'm at a loss.

[dr_spock]

That could also be the low battery warning on the PUP hub.

 

[M_slug357]

@Modeltrainman I agree with @dr_spock . If the light on the box flashes orange, that means the battteries are too low for operation. If the light is flashing white, that means that it is either out of range, trying to pair, or receiving interference. Hope this helps! 

[Modeltrainman]

Thanks @m_slug357! Now, on the subject of side rods, do I want a lot of slack, or a little? Using 1x7s on the back wheels, then 1x6s to the cylinders. Too much? Too little? It's hard, because I know on the Emerald Night they gave enough slack, but I remember it had to push 6 wheels, and pull at least one car. I'm trying to pull a tender and 3 cars(elephant car, coach and caboose.) And I have the cylinders hanging, because that's how they were drawn in Dumbo. I've tried 1x6 and 1x4 rods to support the valve gear. Progress pics in my other post.

 

Edited July 28, 2019 by Modeltrainman

[Roadmonkeytj]

As long as your not getting any binding either should work you may need a longer piston rod if modeling similar to the emerald.  But if using the 2 bars and pin then as long as they aren't pulling out or pushing

[zephyr1934]

The EN design of pushing an axle through a hole is a lot of resistance. It is not a problem on the EN because of the XL motor, but it might be an issue in your build. The pin between two bars (as per the two designs linked in my earlier post) is far more energy efficient. As for spacing, slack, etc., it all depends on the design. You really have to build up the mechanicals and tweak them until you get something you like. Be sure to test for clearance and functionality on curves, not just straight track. If you want your design to be really robust, add a bump to your test track (a plate under a rail joint)

[Modeltrainman]

@zephyr1934 Thank you for all the help! I think after I make one more attempt at this, I might have to call it quits, and do just the back linkages. My problem being that I'm going from a cartoon prototype, and he doesn't have anything resembling the two bar system. (I'm not sure how he doesn't rip himself apart, after trying to build him, but maybe that's my problem. Trying to build a model of a cartoon character who can shrug with his cylinders, and real world physics can't match. Regardless, this thread will come in handy as there are many  Disney trains(DLRR, WDW) that I want to build, so these ideas aren't wasted. Sorry if any of you feel you wasted your time, wasn't my intention.

Edited July 29, 2019 by Modeltrainman

[Roadmonkeytj]

I would use a similar set up to the emerald night with a rod sliding through the steam chamber 

Im looking at this reference photo 

 

[Modeltrainman]

@RoadmonkeytjI was trying that. My wheelbase just proved too small to stuff that into. That's OK though. I realized I don't want to stress the motor too much. 

[Roadmonkeytj]

I think your underestimating the power of the motor. As long as your drive wheels are quartered you should see no problem with this set up.  Infact as I think about this I think the way ALCO converted the holiday train  to have side rods will work if you just use the piston conversion ... Then if you combine it with the pilot truck design from Zephyr1934's lone ranger it should give you the effect your looking for.  I truely belive either powering this with a m motor in the loco or the train motor under the tender will power this just fine.

[zephyr1934]

13 hours ago, Modeltrainman said:

Sorry if any of you feel you wasted your time, wasn't my intention.

Not a bother, I would not have written in the first place if it were. The whole point is to have fun.

[Modeltrainman]

2 hours ago, Roadmonkeytj said:

I think your underestimating the power of the motor. As long as your drive wheels are quartered you should see no problem with this set up.  Infact as I think about this I think the way ALCO converted the holiday train  to have side rods will work if you just use the piston conversion ... Then if you combine it with the pilot truck design from Zephyr1934's lone ranger it should give you the effect your looking for.  I truely belive either powering this with a m motor in the loco or the train motor under the tender will power this just fine.

So, um, question, because you brought it up, are there pros and cons to the motor in the tender? I personally like the idea of the locomotive doing the running, and the Powered Up train motor is all I have for Powered Up, which I want to get comfortable, since that's the newest platform LEGO is offering...Could I get away with driving rods and all with the motor in the loco? My problem is, I ALMOST (emphasis) got it o work, but the side rods pulled the cylinders off the frame. Bought some(more) of the frictionless pins @zephyr1934 mentioned in the Holiday Train rod thread you linked, and LEGO shipped my black 1x7s, so should be ready soon. Also, @zephyr1934, I'd like to know, how'd you balance the pilot truck on the Constitution? On Casey, it either wants to tilt ever slightly forward or back, despite my efforts, and when it does, it derails. Oh, and not That it matters, but this is my first train in years, so I probably read,(and forgot) some fundamentals...

Edited July 30, 2019 by Modeltrainman

[Roadmonkeytj]

You should be able to fix the motor solid to the engine the side rods would then always be in line with piston housing.  As far as the truck it shouldn't derail the train if its pivoting properly.

The new powered up line dont limit yourself to just the train motor if the m or l motor would work better.  Its not showing the simple m motor 45303 (came in batman car)

 

[zephyr1934]

Oh yes, you always want non-friction pins for the rods (except for the cases where you KNOW you want friction). Parts will usually be cheaper from Bricklink than from Lego, but not always. The biggest advantage of putting the motor in the tender is that you have a lot more room to hide the PF stuff. Since you are using PUP, you still have the battery box to hide. If your loco is small you might not have room in the loco. Second advantage is that with the normal motor wheels the train will go slower than if you powered the large driver wheels. Of course if you are building for an IDEA, you probably do not need a motor [(1) even great trains don't win that lottery, (2) if Lego did make a set of that train it would probably be unpowered- see toy story, lone ranger, HP, xmas, etc, (3) the accepted IDEA designs usually get a major overhaul before becoming sets].

In terms of the constitution, you are first building virtually? If so, follow the posted instructions first for the bits you need. It might very well be that my design is not compatible with using the train motor for the main driving wheels.