Traction

[HRBuildNStuf]

For those of you who power a "steam" locomotive by the big drive wheels (not using the specialized train motor), how do you get to where you can pull coaches?

I finally have a motor with enough power that it's not stalling (45303 stalls just trying to pull the weight of the battery box; I'm using 22169 which has enough power to cause gear slip before it stalls); I have 1:1 (12-tooth) gearing that doesn't slip under sufficient driving force (I can push down on the train pretty hard while the wheels spin without the gears slipping), and I even add more weight than I can realistically get just with LEGO (I set a couple of D batteries (almost 300g/10oz) over the driving wheels to push the thing into the track). The 4 geared wheels (yes they are the flanged wheels with the O-ring) are the only load bearing wheels, all other wheels "float" with suspension travel so they don't apply any competitive downward force on the rails, so I've done as much as I can to create downforce upon the driving wheels.

But the locomotive can at best only pull itself. The moment I add a coach the wheels start to spin, and I can eventually get around a curve but can't make it through a switch.

I'm at a loss and wondering if it's even possible to create a train that uses the linear motors and gearing and doesn't rely on the dedicated train motors. I see so many MOCs not using the train motors, I'm really wondering how you do it! It's not as if I can throw more motors or more power at the problem, since the problem now is not power but traction. Will I really be required to have a helper at the back with one of the bogie-train-motors if I want to pull any coaches?

Edited April 3, 2020 by HRBuildNStuf
calculated weight

[Duq]

Are these LEGO wheels or Big Ben? Sounds like you need rubber traction bands rather than more weight.

What's the 22169 motor, can't find that on Bricklink? The Power Functions L and XL motors are popular with train builders.

[dr_spock]

Can you post a link to pictures or videos of your setup? 

 

[HRBuildNStuf]

1. LEGO wheels, 85489 with transmission to the fore and aft while the center unflanged literally float (with some suspension travel) unconnected to anything so they never add any friction or resistance.

 

2. It’s the Powered Up version of the L motor (though I think they give it the Technic moniker for whatever reason). Indeed bricklink does not have it, try brickowl or you’ll have to google it. It actually snapped a 12-tooth beveled gear when things got inexplicably stuck, so its power is definitely sufficient. Though, disappointingly, it’s still too easy to stall if I try to gear up to 2:1 for speed.

 

3. I’ll get some photos going soon, sorry.

3. I’m actually getting inconsistent performance. I’m paying close attention now to exactly where the weight is distributed as well as the effects of the cars behind and how their coupling design might possibly create unwanted lift.

 

Just when I think I have success, it’ll turn into failure without changing anything. This has happened a few times. I’m also still trying to zero in on a transmission build that doesn’t inevitably wind up slipping (or even breaking) gears. I don’t have enough of them at the moment but I’m trying to just stack a few 12-tooth double bevel gears now. The last incarnation had a vertical drive shaft, things got stuck (I still don’t really know exactly where) and a bevel gear snapped.

[SD100]

I've motorized the hogwarts express with an L motor, and have been fighting to get DaMangos Flying Scotsman motorized. I think most steam locos will need an XL motor in them if you want them to pull anything. I try and put a boat weight in each loco but I don't think that's even enough half the time.

[Duq]

16 hours ago, Duq said:

Sounds like you need rubber traction bands rather than more weight.

My BR 55 happily pulls a string of freight cars on a single L-motor and even the old BR 65 on a single M-motor manages to pull trains. 

Neither has extra weight on board, both have rubber bands (on one side!).

I haven't used XL yet because I just don't have the space in the engines I build.

BR65 Drivetrain by Duq, on Flickr

BR55 Drive train by Duq, on Flickr

 

[zephyr1934]

3 hours ago, Duq said:

both have rubber bands (on one side!).

Those last three words are important. If you have bands on both sides and your motor is already at its limits, then the different radii of the rails on a curve could stall the motor if you have bands on both sides. With bands on just one side that radius wins.

 

[HRBuildNStuf]

The simplest way I can describe my current problem is that my gears mesh, but they won't *stay* meshed. They keep slipping. Then if I try to tighten things up there's too much friction. I'll put something together and put it on some straight track and go back and forth like 4 or 5 times and on the 5th time it stops moving as some gears have slipped. *shrug* I've been trying my hardest to do this where I'm powering the fore and aft wheels and carving out some suspension in the center for the center wheels to float a bit, but I think I'm going to have to give up on that. It probably won't make any sense until I post some pictures which I will eventually, but what I've found is that the L motor will easily pull apart studs so you can't hold your transmission together that way, but mixing technic with studs is easier said than done for me.

By the way Duq, what is that piece on the end of the motor in your BR55 transmission that's holding the transverse gears together so nicely? I've never seen it before and have no idea how to find it haha. That might be the sort of thing that can help me out a lot since as I said I can get my gears to mesh nicely, but they're not staying meshed under power.

[HRBuildNStuf]

After doing some more research and watching a video or two, I verified my suspicion and figured out my biggest problem with the gears. My limited inventory had sent me into a cul-de-sac of futility. I have 2 double-bevel 12-tooth gears and a bunch of single-bevel 12-tooth gears. Outside of that I only have the standard gears (8,16, 24, 40). You can *kinda* mesh those 12s with the standard gears, enough to move your train a little bit and fool you, but they don't really mesh. I have some more double-bevel 12s and a couple of double-bevel 20s on order. Once those arrive I think I will have better luck with my transmissions and not run into the *almost* problems I've been running into trying to mix 1/2 gears with the 1/4 gears. I suppose most people probably already knew this but newb me is still learning LEGO gear basics haha.

After I finally get a consistently working transmission I'll probably still have to wrestle with traction a bit. Banding only one side of the wheels is a good tip, makes sense.

[Duq]

As mentioned in the comments on Flickr, it's part 48496, "Technic, Pin Connector Toggle Joint Smooth Double with 2 Pins".
alpha.bricklink.com/pages/clone/catalogitem.page?P=48496#T=C

Where possible use some sort of bracing for your gear train, like I did with the 5L beam at the front in the second picture. In most situations it's best to use 8, 16, 24 and 40 together, and 12, 20, 28 and 36. They will mesh nicely at standard distances.

Don't use single-bevel gears unless you need to turn a corner. And finally, the fewer gears the better. LEGO gears are engineered for simplicity and easy use, not for minimal friction.

Show us some pictures of what you're doing.

[HRBuildNStuf]

Thanks for all the advice and commentary so far!

I'll start with a video showing that I've had some success, though I haven't been able to maintain it:
http://www.youtube.com/watch?v=eCB0UCQI3xs

This was at the end of an evening working on things. With no extra ballast and a 1:1 gear ratio (vertical driveshaft using all single-beveled 12-tooth gears) it's chugging along with ease pulling a couple of coaches. I think I've got it!

Alas, the next morning it can't even pull its own battery box! Nothing but wheelspin, even as I added over 1/2 a pound! Huh? This explanation is a bit much, but the only one I can think of at the moment: an F1 car might as well be a curling stone on ice without proper heat in the tires. Maybe the night before the O-rings were sufficiently warm, but the next morning they were too cold to provide grip? It sounds extreme but it's the only idea I currently have for why success turned to failure without touching a brick. Also, as I was adding weight, this eventually happened:
http://onedrive.live.com/?authkey=!AKwHJlsUGRaiXiE&cid=68647F36576FACB2&id=68647F36576FACB2!117615&parId=68647F36576FACB2!117595&o=OneUp

...which at least let me know I wasn't in need of a more powerful motor.

Some background on the project (skip ahead if you don't care, it's totally fine), what I'm building is the Galaxy Express three 9s train (which is essentially a JNR C-62; 49 of those were built and the GE999 in the first season is emblazoned with C6250). My starting point was to build a chassis that could navigate any track layout thrown at it, and I think I've managed that. I built any number of test tracks to make sure all the surface bits cleared as it went up and down and around all manner of curve combinations, grade combinations, and curve + grade combinations. And what I'm most satisfied with is that no matter the track geometry, none of the driving wheels are ever lifted off the track and none of the locomotive's weight is ever supported by any of the passive wheels. Basically I think that I've maximized traction to the driving wheels by ensuring that all of the passive wheels always "get out of the way" and even as it enters or exits a grade the chassis "bends" enough that the driving wheels never go airborne.
http://onedrive.live.com/?authkey=!AM8f86uT_zNplsA&cid=68647F36576FACB2&id=68647F36576FACB2!117613&parId=68647F36576FACB2!117595&o=OneUp

Front bogie: 
http://onedrive.live.com/?authkey=!ALFxBjYKcLSvxOA&cid=68647F36576FACB2&id=68647F36576FACB2!117597&parId=68647F36576FACB2!117595&o=OneUp

Rear bogie:
https://onedrive.live.com/?authkey=!ADyt80ctcWZdcSs&cid=68647F36576FACB2&id=68647F36576FACB2!117598&parId=68647F36576FACB2!117595&o=OneUp

You can see how the front and rear aren't really necessary:
http://onedrive.live.com/?authkey=!AO4x4eZnyfUhiJg&cid=68647F36576FACB2&id=68647F36576FACB2!117612&parId=68647F36576FACB2!117595&o=OneUp
http://onedrive.live.com/?authkey=!ANLCtbs2lh9O0W0&cid=68647F36576FACB2&id=68647F36576FACB2!117610&parId=68647F36576FACB2!117595&o=OneUp

If you're at all familiar with "Galaxy Express 999" you'll know that the locomotive's computer is an oft-referenced and sometimes even featured character in the show, so of course I need to include it. :-)
http://onedrive.live.com/?authkey=!ADnsHSo9QE_R3O8&cid=68647F36576FACB2&id=68647F36576FACB2!117596&parId=68647F36576FACB2!117595&o=OneUp

Motor mounted (as I work out the gearing it may move up or down or forward or back a bit):
http://onedrive.live.com/?authkey=!AEq-QaKYFv0fEbM&cid=68647F36576FACB2&id=68647F36576FACB2!117608&parId=68647F36576FACB2!117595&o=OneUp

Shot of the fundamental chassis underneath everything:
http://onedrive.live.com/?authkey=!AD-ETMrjDHf-k6U&cid=68647F36576FACB2&id=68647F36576FACB2!117607&parId=68647F36576FACB2!117595&o=OneUp

I made a copy of that chassis to show my starting point:
http://onedrive.live.com/?authkey=!APJMYujW-SH577M&cid=68647F36576FACB2&id=68647F36576FACB2!117602&parId=68647F36576FACB2!117595&o=OneUp
http://onedrive.live.com/?authkey=!AIAICBnUMBN9C-k&cid=68647F36576FACB2&id=68647F36576FACB2!117603&parId=68647F36576FACB2!117595&o=OneUp
http://onedrive.live.com/?authkey=!AFlvYGn0MjcZUYo&cid=68647F36576FACB2&id=68647F36576FACB2!117605&parId=68647F36576FACB2!117595&o=OneUp

The first solution I'm pursuing puts a gear on that driveshaft, then stacks another one on top of it to get me above the wheels where there's more room to work:
http://onedrive.live.com/?authkey=!AMcvpTxReg9JZJA&cid=68647F36576FACB2&id=68647F36576FACB2!117606&parId=68647F36576FACB2!117595&o=OneUp
http://onedrive.live.com/?authkey=!AIzDd2KmaYGGYuw&cid=68647F36576FACB2&id=68647F36576FACB2!117604&parId=68647F36576FACB2!117595&o=OneUp

Part of the problem I'd been having is that's the last of those gears that I have, so all of my other gears are what I've now learned are sorta incompatible with those; at least if you're confined to a tight space good luck making a 12-tooth work reliably with an 8, 16, or 24. Pun intended I really "spun my gears" trying to make those work haha. I also tried just using 8s to get above the wheels, but ended up having to choose between too much slippage (fail) or too much friction (also fail).

Here's an alternative solution that makes use of the venerable vertical driveshaft that appears to be widely used:
http://onedrive.live.com/?authkey=!AGAO8KOfIvolitQ&cid=68647F36576FACB2&id=68647F36576FACB2!117601&parId=68647F36576FACB2!117595&o=OneUp

A downside to this is it pushes the motor back a stud and up a plate, which I'm not sure I'll have the room for either. Another drawback is this little gap on that vertical axle that will allow the gear to lift up a bit, which I can't seem to fill with any LEGO I know of:
http://onedrive.live.com/?authkey=!AJtJJXXggxN5N6g&cid=68647F36576FACB2&id=68647F36576FACB2!117600&parId=68647F36576FACB2!117595&o=OneUp

As the slack gets taken up on that gap the gears down there still stay meshed, but they're right on the edge of slipping at that point. I'd feel better if they stayed more strongly engaged for when they start to encounter more torque.

Final drawback will be that it's 4 gears to get the driveshaft in the undercarriage spinning. Two at the top of the vertical driveshaft and two at the bottom.

With the stacked gear solution I'm going to try out as my primary, I think I might be able to mesh a 20-tooth directly to that 2nd 12-tooth poking out above the wheel line, attached directly to the motor. That will not only get the undercarriage driveshaft spinning in 3 gears instead of 4, but it will also give me a 5:3 gear ratio which I think would be nice for speed if it'll work out. (The C62 has been clocked at 129mph and well the cartoon version achieves escape velocity so it's not inappropriate for this model to have a little zip.)

But since I just don't have any of the requisite gears, I  have to get some in order to continue.

 

 

Edited April 5, 2020 by HRBuildNStuf

[Duq]

I see a few issues in your pictures...

Picture 11 shows that your drivers are not 'quartered'. That's important to stop the whole thing jamming.

Why do you have this odd construction for the middle axle? It looks like you want it to move up and down, but that won't work with the drivers and may again contribute to the drivetrain jamming. You are using a 'blind' driver in the middle which will float left and right when the engine takes corners. You are using axle-pins for the middle drivers. An single axle for the two wheels would be better but that gets in the way of your driveshaft. Second-best are 2L axles; they will give less friction. The side-rods will stop the wheels falling off.

Third thing I noticed is that your side-rods/coupling rods are not rigid; you have a hinge point in them, possibly for that suspension in the middle axle.

Last thing are your connecting rods that go through an axle/pin connector. This is another construction that may jam. Have a look at other (LEGO) steam engines. You'll see that most will have some way to guide the horizontal movement of the end of the connecting rod.

The image above is from the Big Ben site. It's got some good tips for building a drivetrain: http://www.bigbenbricks.com/applications.html

I hope with all these comments you can make some progress tonight. Looks like you're working on an ambitious project!

 

[Thai bricks]

@HRBuildNStuf Onedrive says the items don't exist... Have you moved or deleted your pictures?

[Duq]

Hey @HRBuildNStuf, you've been quiet for a few days. Did my comments help? Have you made some progress with the running gear?

[HRBuildNStuf]

Hello @Duq and also @Thai bricks & @zephyr1934, @SD100, @dr_spock; sorry for taking a while to post again, I've had a busy week and wasn't really able to work on my project at all until late in the weekend.

First off, thanks for the tip about quartering. I'd totally forgotten that steam engines are asymmetrical, haha. I'd been fortunate not to have had any real problems getting stuck while symmetrical, but I've quartered the wheels now so thanks for that.

Next up, getting a 20-toothed gear (getting a gear that's truly compatible with 12-tooth gears) made all the difference for my transmission. Fit right in,meshed beautifully and stayed meshed under power. If only I'd had one of those gears to begin with I sure could have saved myself a lot of time and headache! Haha... for future builders, don't waste your time meshing 8, 16, or 24-tooth gears to a 12. It'll seem to work just enough to make you waste your time, but won't hold up under stress.  So I'm good to go with transmission now and no longer suffer from gears slipping or seizing up.

As for the odd construction in the middle of the chassis, it is indeed suspension to allow the center wheels to move up and down. I'll try adding a photo here to provide some insight as to what I'm up to with that suspension:

http://www.flickr.com/photos/187779091@N02/49762277411/

(BTW I try to use the "insert image from URL" function but it doesn't seem to accept the URL, so I don't really know how to just put a photo in the post. This is the best I know how to do, sorry.)

Basically if the center non-driving wheels are inline with the terminal driving wheels, they can at times cause either of the driving wheels to lift off the track, even if not all the way off the track take some of the weight off of the drivers, thus reducing tractive force. Just trying to maximize the tractive force. One way is to keep adding weight, but I'm trying to not just add weight only but also add this approach of keeping the most weight possible directly on the driving wheels at all times. So, I've made it such that none of the weight is wasted on the center wheels, and also they're never going to negate any of that downforce on the driving wheels so that I'm always as close as I can get to the locomotive's theoretical maximum tractive force.

You have a keen eye to spot so many things in the photos! But what I perhaps hadn't mentioned is that the center wheels aren't part of the drivetrain at all. They're not actually attached to the driving rods, they really are just there for decoration. So they don't add any real friction directly to the drivetrain. That being said, if I just used a 2L axle they actually would want to fall out or at least collide with the driving rails a lot since they're not actually attached. I do however use 2L axle in lieu of a pin on one of the gears in the transmission so I agree with using that to reduce friction, where I can get away with it.

That bend in the driving rods is more the result of an aesthetic choice than anything*, but it's not actually a hinge point where there's movement or you're right it would totally seize up the rods constantly. There's a friction pin in there (actually a 1/2 friction pin as I cut it down since keeping all of the driving rod assembly to a minimum footprint is a priority for me), so it doesn't move around. It always finds that one slight bend and stays that way. I can and may end up putting a little glue in there so that it can be a slightly more aesthetically pleasing straight line, but I do also find it interesting that its all at its happiest when it's slightly askew like that. Probably because the two connectors with a 2L axle which should be equivalent to 4L ends up being just slightly longer than 4L. That, or that distance from hole to hole in the wheels is just slightly less than 5L rather than being exactly 5L. Whatever the case, I'm actually doing ok there so long as there's no movement at that point (friction pin does enough to keep it still).

*The aesthetic choice(s) would be, for one, I really don't like the look of liftarms as the driving rods, so I am trying to use anything other than liftarms. Though I'm also still keeping it strictly LEGO and not using custom or other branded parts. (OK cutting a pin in half was customizing a part, I give you that. So was cutting a black 10L axle down to 9L instead of using a grey 9L axle.) Anyway, my goals were to avoid beams if I could (had to use one but I kind of have it buried under everything else) and to keep it as minimal as possible (didn't want to have stuff sticking out as far as 10 studs wide; the widest bits of the driving rods go as far as 9 studs). That's also why I didn't even go for a valve gear. Honestly while everything is chugging along, there are things most people won't even notice, like no valve gear and that maybe the center wheels occasionally aren't actually spinning (you really can't see the latter unless you were specifically looking for it in a slow motion closeup video). Especially anyone who's not totally into steam locomotives, but maybe just regular ordinary observer probably doesn't even know about all the valve gear intricacies  and is just happy enough seeing those bits chug in and out. Anyway, that's what I came up with that uses stuff besides liftarms, obscures the one liftarm that I'm using, and only totals 1.5 studs in width so doesn't protrude too far out each side. Its equilibrium includes this little kink, which I might keep straight with some glue but by virtue of remaining in its orientation due to the friction pin doesn't impede or seize the motion. I've seen it work fine with the rods in straight alignment too, though I wonder if there's some slight resistance introduced when they're straight, since they eventually find their way into that kink.

Last thing I've learned, is that at least with my wheels, it really does matter if the O-rings are warm or not. When they're stone cold, there's really no grip at all.

As of now my locomotive is pulling along a pair of 340g coaches, and it only struggles with some wheelspin as it has just come out of a turn into a straight but the coaches are still amidst their turns. (Which I understand, less friction in the straight more friction in the curve.)  This is without any added ballast. I have 50g-100g of tungsten weights I am likely to add if I can find satisfactory places to put it, but I'm not sure how many more coaches, if any, that will get me. I'm prepared for a future where I have 4 or 5 coaches but the last one is motorized.

@Thai bricks, sorry about the links not working. I wonder, anyone else having the same problem? Let me know if that flickr link above works, I can try pointing you to photos that way. And I may yet learn how to get inline photos showing up right in the post itself so that you don't have to follow a link.

It's close to being presentable if not completed; I'll get some more photos of the project up next weekend.

Edited April 14, 2020 by HRBuildNStuf

[doug72]

Re photo,link,  read the Forum FAQ,s to find out how to embed images in your post. There is step by step guide on how to do it.

Edited April 14, 2020 by Doug72

[Duq]

Posting images from Flickr should be simple:

Flickr - BBCode link by Duq, on Flickr

The popup window is slightly different but you still simply copy that line and paste it in your post like I've done here.

[zephyr1934]

9 hours ago, HRBuildNStuf said:

As for the odd construction in the middle of the chassis, it is indeed suspension to allow the center wheels to move up and down. I'll try adding a photo here to provide some insight as to what I'm up to with that suspension:

That is probably overkill, any sort of track where you would need that clearance would likely derail your train anyway. A blind driver between two normal drivers will already have a gap above the rails. Even if there was an occasional rail joint that was high enough to push the center axle up and lift one of the flanged drivers off the track it would only be a very short distance (under 4 studs) and the momentum of your train will keep it moving over that gap. Anyway, if you do go that route, just remember do NOT pin the middle axle to the rods, otherwise, as noted in the earlier reply, the rods will keep the middle axle from lifting as designed.

As for pure lego rods, as long as you do not mind the added width, you can build up some okay looking rods with technic connectors. But they will tend to pull apart over time so either gearing the driving wheels together or a drop of glue on the joints of the built up rod helps.

[Duq]

Didn't have time this morning for a longer reply but was going to say pretty much what @zephyr1934 wrote there. My steam engines all have rigid frames, and none of them have ever got stuck on uneven track.

This one has no power but is another example of running gear using Technic parts:

BR70 rear by Duq, on Flickr

 

[HRBuildNStuf]

Hey guys! Thanks for the continued feedback and advice! Including the image posting advice -- I was pasting the raw HTML URLs not the BBCode URLs, oops! Thanks for the tip!

@zephyr1934 & @Duq you're both right that with momentum and weight I can overcome most of the ups and downs in any typical track layout, but that hasn't stopped me from attacking problems from every angle haha. You're also right about not having the center wheels pinned to the running gear, which I don't. You may also spot in one or more of the clips and images below that my running gear is mostly technic axles and connectors, with a liftarm tucked underneath begrudgingly included. (The connectors near the pistons are sliding back and forth along a Bar 6L.)

Here's a video I took today of me running on my little test track:

So subtle and fine the line between enough traction, and not enough traction! The naked eye can't even really see it (reduction in downforce), only the effects. So the engineer in me went to work, and eventually I figured out where that lift was coming from. (You'll see it in the next video.) It doesn't happen when pulling (forward), only when pushing (reverse) but the way my rear bogie articulates led to that little bit of lift -- not even enough to see on the track with the naked eye, but enough to negate sufficient tractive power.

I reworked that connection a little bit (pictured -- comes with its own drawback, reduced track clearance and I might end up clipping switch tracks but I'll figure that out and sort that out next), which you'll  see makes a difference.

I don't really know the best way to describe the change with words, other than I sort of lowered things a bit to put vectors of force more in a straight line. I dunno I hope that somehow makes some sense. See the result below:

One more clip just highlighting how even flat track isn't really flat, and while I can generally sledgehammer my way through these ups and downs with weight and momentum on a rigid chassis, I'm a little happier if I can flatten out my traction power's graph so that it's more consistently at its max and doesn't have as many of the little peaks and valleys even if their effect isn't terribly significant. (If you were to accuse me of building what is essentially a rally car of a steam locomotive, I wouldn't argue haha.)

Also, I'm still seeing the effects of temperature play a significant role! Basically in the morning when the locomotive has been sitting near a window and its tyres are stone cold, it just won't have the grip it had the night before which before I kind of put 2 and 2 together really had me at a loss and is exactly what prompted me to start this thread asking "what am I missing?"

I've got some more black pieces showing up later this week that should clean up a few spots where I just have placeholder pieces, like around the cylinders and steam guards. I'm still not satisfied with the "belt line" details, (the space between the wheels and the boiler), so I'm still working on trying to tweak the aesthetics there.

I've been really appreciative of your wisdom and feedback and have really learned a lot throughout this undertaking! Thank you again! I should have another update over the weekend.

Edited April 15, 2020 by HRBuildNStuf

[zephyr1934]

10 hours ago, HRBuildNStuf said:

So subtle and fine the line between enough traction, and not enough traction! The naked eye can't even really see it (reduction in downforce), only the effects. So the engineer in me went to work, and eventually I figured out where that lift was coming from.

The locomotive getting caught in a sag like that is different than the middle driver axle lifting another driver axle off the track. That problem is due to the pilot and trailing trucks not having enough clearance above. Lego locomotives with three "trucks" are not great on rolling terrain unless specifically designed for it. To address that you need to think of the clearance above and the points of articulation within. For the clearance above, as you build you need to carve out space above the pilot and trailing trucks and then test your design on the most extreme track you plan to run on. For the articulation, that can become a nasty mechanical engineering problem. While I do not have specific guidance there, this build has vertical angle rotation around the rear driver axle:

Works fine and this locomotive is pushed by the tender (similar dynamics as you encounter backing up). I designed this much play because my club has notoriously uneven tables due to members standing on them to assemble skyscrapers.

Now looking at your track setup, PF is not great with grades. It looks like you are climbing at least one plate per track segment, maybe more. That is extreme (I've heard that the max recommended is one plate per track segment). One can do steeper than that, but you will have to engineer it knowing that you are fighting the limits.

Now if your goal is maximum power, remember that big wheels are for speed and little wheels are for power.

Finally, a tip on photographing black steam engines- try to get the lighting behind you, i.e., coming from the same direction as you are taking the picture from. In some of your shots the lighting is on the far side of the build, putting the features you are trying to show are in the shadows, where it is very hard to see the details of the black parts.