[WIP] MCI D4500CT Commuter Coach

[JLiu15]

Last year, I built a MOC of the NJ Transit New Flyer XD60 Articulated Bus. That model was a huge success, so back in August I started working on another bus model: the NJ Transit 2016-2022 MCI D4500CT Commuter Coach.

I anticipate this model having a lot more functionality than my XD60 model. There will be 6 motorized functions total, 4 of which are controlled via a 4-output distribution gearbox. The model will use Control+ electronics, with a single hub powering 4 motors (1 C+ XL for drive and 3 C+ L for steering, gearbox functions and gearbox switching). The 4 motorized functions controlled via the gearbox will be opening/closing the passenger door, extending/retracting the wheelchair lift, raising/lowering the wheelchair lift, and opening/closing the wheelchair door. The model will also feature suspension on all axles. I believe the real MCI D4500CT have independent front and tag axles and a solid driven axle (not 100% sure), but a such a setup might be too complicated so I went with a live axle suspension on all axles. I also plan to include a model of the Cummins X12 engine with mini pistons, which can be removed from the chassis as the pistons won't be visible when the engine model is inside the bus. Only the 2020-2022 (plus a handful of 2019) models have the Cummins X12 engine (previous years had the Cummins ISX12 engine), so my model will be of a 2020 or newer unit, most likely 2021 as the 2021 order was by far the largest.

I started designing the model in Stud.io shortly after BrickFair VA back in August, focusing primarily on the chassis. The biggest challenge was making sure the wheelchair lift can fully extend/retract from the chassis and not interfere with any other mechanisms. The wheelchair lift's transverse range of motion takes up almost the entire width of the bus, so it was difficult making sure I can squeeze all the functionality in there without compromising on looks. Making sure I had the space to fit everything was also a challenge, as the distribution gearbox and Control+ hub both take up a lot of space.

I have a preliminary version of the chassis modeled in Stud.io, and have begun building the physical model. The chassis is a very dense build, with plenty of mechanisms running through it. I also have the "stainless steel" side panels (all metallic silver - definitely won't be cheap) and seats in place in the Stud.io model. The Stud.io model is already over 4000 pieces, so I think this model will easily surpass the part count of my XD60 model. Just like my XD60 model, because I am modeling it in Stud.io, I plan to publish instructions for this MOC when it's finished.

I've included some photos of the physical model as of right now (I mostly just have the gearbox section done), and some screenshots of the Stud.io model showing its progress since August.

Photos:

[Thirdwigg]

The Flyer was incredible, and this is looks great so far.

Are you going to make little suitcases to go in the bottom too? 

[Jurss]

Poor tires. Or it won't be so bad (weight)?

[1gor]

Perhaps it is not the best day (today) for anything funny, but if I remember you are on the busses lately (sounds like classic british sitcom).

Important is that you enjoy building and I believe that this one would end up great as Flyer.

kind regards 

[Aleh]

But were poor passengers will carry their bags? :)

[JLiu15]

On 11/17/2022 at 8:52 PM, Thirdwigg said:

The Flyer was incredible, and this is looks great so far.

Are you going to make little suitcases to go in the bottom too? 

Thanks!

Lol, the chassis is very densely built and nearly every inch of space is taken by mechanisms or electronics. The luggage compartment space is completely taken up by the Control+ hub lol.

On 11/18/2022 at 1:33 AM, Jurss said:

Poor tires. Or it won't be so bad (weight)?

I think the tires will be fine. The 62.4x20 tires are pretty stiff so weight shouldn't be an issue. Their rims also come in metallic silver (from set 8285) which I plan to get as they'll match the metallic silver "stainless steel" sides well. They definitely won't be cheap though...

[JLiu15]

UPDATE 11/19/22

Got a little more of the chassis built. I'm mostly just following the Stud.io model, making changes where necessary. The drive motor and attachment points for some of the seat pairs are now in place. It's not the best location for the drive motor, but it's placed just far enough for its wire to be able to reach the hub. This also leaves more room behind the rear axles for the engine model.

The biggest challenges right now are to make sure the motors' wires can reach the hub and not interfere with the wheelchair lift extending out from the chassis. The hub cannot be placed any closer to the drive and gearbox motors, and their wires are stretched as far as they can (there's probably 3rd party Powered Up extension cables out there, but I want to keep this MOC 100% LEGO).

I've included some screenshots of the Stud.io model with the wheels, seats, and "stainless steel" panels hidden to get a better view of the chassis. It's very densely built - nearly every inch of space is taken, and the chassis alone has nearly 3000 pieces. No room for a luggage compartment in the bottom. 

Photos:

[weavil]

This look nice and very big.

 

On 11/19/2022 at 1:27 PM, JLiu15 said:

On 11/18/2022 at 1:33 AM, Jurss said:

Poor tires. Or it won't be so bad (weight)?

I think the tires will be fine. The 62.4x20 tires are pretty stiff so weight shouldn't be an issue. Their rims also come in metallic silver (from set 8285) which I plan to get as they'll match the metallic silver "stainless steel" sides well. They definitely won't be cheap though...

The tires should be fine, however, the flex/play of the axles might an issue.

[JLiu15]

UPDATE 12/3/22

I had to rework the gearbox, which meant redesigning some of the chassis. The previous design used a worm gear for both extending/retracting and raising/lowering the wheelchair lift. Because the extension mechanism used 8-tooth gears meshing with racks along the chassis floor, it made the mechanism painfully slow - so slow you could barely see it move. The worm gear mechanism was embedded deep in the chassis, so I had to go back to the drawing board on that part. I was able to figure out a way of transferring drive to the extension mechanism with a 1:1 gear ratio, which should make the extension/retraction speed much more reasonable.

The width of the model was the primary challenge of transferring drive to the wheelchair lift module. The wheelchair ramp needs to both fully extend from the chassis and fully retract into the chassis, and 7 studs of the chassis width is taken up by the ramp itself with the gear trains for the two wheelchair ramp functions made to take as little width as possible. The chassis is 17 studs wide, and the wheelchair ramp module slides along 2 16L axles transferring drive for the two functions. Being able to allow for the full range of movement while keeping the chassis robust was a challenge, but so far it looks like the chassis remains pretty rigid.

As noted in my previous update, another challenge was finding a place to put the Control+ hub and have the motors' wires able to reach it. The heart of the chassis (i.e. between the front and rear axles) is divided into three main sections - the rear third is the gearbox and the middle third is the wheelchair ramp, leaving only the first third available for the hub. Thankfully, the motors' wires were just long enough to reach the hub's ports. The wires also sit high enough that I don't think they'll interfere with the extension/retraction of the wheelchair lift. I had built the wheelchair lift module prior to rebuilding the chassis and it seemed to work fine, but I will have to redesign that as well as it needed a greater range of raising/lowering motion (I already have it modeled in Stud.io). I do have to order some parts before I physically build it though.

Photos:

[JLiu15]

UPDATE 1/22/23

I finally had some time to work on the model, so I built the wheelchair lift module and inserted it into the chassis. Two independent motorized functions pass through it: the wheelchair lift extension and elevation, which are controlled by the two 16L axles the wheelchair lift module slides along.

Unfortunately, while my design works in theory, it will not work in practice for several reasons. The main reason is that there is an immense amount of friction in the mechanism from all the gears involved. Three 8T gears alone are used to transfer drive inside the wheelchair lift module alone for the two motorized functions, one of them being the red frictionless 8T gear that can slides along the 16L axles. This plus all the gears in the gearbox results in so much friction for the extension mechanism that I could barely turn the input gear in the gearbox by hand. I didn't test it with the motor but my guess is the linear clutch in the gearbox will start slipping before the wheelchair lift will actually move. The second reason is that there is a lot of play in the wheelchair lift elevation mechanism. Due to space constraints, the worm gear mechanism can only be housed in the chassis instead of on the extendable module. The three 8T gears and the torsion in the 16L axle results in so much play that I can practically raise the wheelchair lift to the upper position by hand without any motor input. The play in the mechanism also prevents me from being able to control its position precisely, making it very difficult to line up horizontally when retracting the wheelchair lift. It also takes several rotations of the input before the wheelchair lift even begins to raise, and when lowering, the wheelchair lift lowers a ton at once that if a passenger were to be using it, they would probably fall off. 

To be fair, when I was building the model in Stud.io I had realized that some of the mechanisms might not work in practice, but I decided to give it a try just to see how it goes. This is also one of my most mechanically advanced MOCs to date, from the remote-controlled 4-output distribution gearbox to the complex wheelchair lift mechanism. There's no easy fix to the issues as there will always be the issue of directing two motorized functions into a sliding module with very limited space, and even without accounting for the gearbox the friction and play issues are already very prominent. Because of this, my plan is to completely remove the wheelchair lift function and focus on the aesthetics instead (while still keeping the motorized opening door), just like my New Flyer XD60 model. This will also reduce the weight of the model and can allow me to add a second C+ XL motor for propulsion. This will also eliminate having an unrealistically large door for the wheelchair lift mechanism on the right side. Lastly, I could see more issues coming up down the line with the whole wheelchair lift setup, such as the sliding wheelchair lift door mechanism as I cannot find a place to brace the sliding door from the bottom with that space completely taken up by seats in the Stud.io model.

While this was a disappointing setback for the model, especially as I already put so much work into designing it in Stud.io, it's also good that I found that it won't work effectively early on in the build before I got too deep into it. This does mean I'll have to redesign and rebuild the chassis from scratch, so it will probably be a while before my next update.

Photos:

[JLiu15]

UPDATE 3/23/23

I have not touched the model since my previous update, but in the meantime I completely reworked the Stud.io model. The front and rear ends of the chassis remain largely the same, but the space in between the front and rear axles was essentially reworked from scratch. Because the wheelchair lift mechanism proved to be impractical, both the gearbox and the wheelchair lift mechanism were stripped. The drive motor and Control+ hub remains in the same locations. I was thinking of adding a second Control+ XL motor for drive since there is an extra port on the hub available without the gearbox, but such a design proved to be very wide. I thought of moving the hub towards the center of the chassis, but it looked awkward sitting in the middle of the chassis with nothing else surrounding it and the hub in the front could act as a counterweight to balance out the engine model. The new chassis design is much more symmetric since it no longer has to accommodate for the gearbox and wheelchair lift mechanism, which made the attachment points for the passenger seats easier to install.

The following screenshots are of the Stud.io model with seats, side panels and wheels hidden.

When the hidden elements are shown, the appearance is not much different from the previous design. However, it did allow for a simpler design of the side "stainless steel" panels as previously the plates which the silver tiles sit on had gaps to allow for 12T gears to rotate for the wheelchair lift mechanism. The right side panel also had a gap for the wheelchair lift door, which has now been eliminated. Screenshots of the full Stud.io model are shown below.

[JLiu15]

UPDATE 9/7/23

After nearly 9 months without progress on this model, I am happy to announce that work on the model is once again underway. As I noticed in my March update, the entire model was reworked in Stud.io without the wheelchair lift mechanism and gearbox. The rear 3/4 of the chassis is complete as of this update, with the front 1/4 and front axle still yet to be built. The chassis also has a Cummins X12 engine model in the back. The seats (along with the supports they're attached to) are not installed yet, as I'm waiting for the chassis to be finished before building anything on top of it (e.g. seats, wheel arches, etc).

The build is going well so far. The chassis is very robust thanks to the use of 7x11 frames along the sides of the chassis - it's built like a tank. The area above the drive and tag axles is also reinforced well enough that the chassis does not bend much when the suspension is compressed.

Any suggestions are appreciated!

Photos:

[JLiu15]

UPDATE 10/3/23

I've done a full rebuild of the chassis in front of the rear axles since the last update. This is because I had to move the Control+ hub back two studs, and it sits deep in the chassis and acts as a structural element. I had to move the hub back because while my original design had the front axle suspension mounted from the front, I changed it to be mounted from the rear to allow for the gearing for the door mechanism (previously the steering motor protruded into the passenger entryway space too much).

Much of the chassis is complete at this point. I still need to include the passenger seats and the motor for the front door (it will be located in a roof frame similar to how I designed my other bus models). I was worried that the passenger entryway is not reinforced enough as there's not much space for reinforcement between the front axle suspension and the chassis. There is some bending, but the chassis is overall quite rigid and this should improve once the bodywork is put on.

Any suggestions are appreciated!

Photos:

[JLiu15]

UPDATE 10/24/23

The chassis is complete with all 57 passenger seats in place, as well as studs on the sides for SNOT connections (the silverside panels will go here). Additionally, the wheel arches are also in place - they placed at a half-stud offset so they will protrude from the body slightly once the model is complete. Note the white axle pieces along the length of the model - they will be used to attach the body panels with 1x1 bricks with axle hole, similar to my MTA New Flyer XD40 model which allows for a seamless finish without any pins showing.

I redesigned the front section to house the passenger door motor in the chassis instead of in the roof frame. The previous design had the motor first connected to the rear door panel, through a set of bevel gears and then to the front panel which meant the front panel had significantly more backlash. Now the motor and worm gear mechanism for the door are placed beneath the passenger entryway, which allows for a much more direct connection to the door mechanism and allows all motors to be placed in the chassis. The front section was also reinforced, as it had a tendency to bend due to the space in the chassis for the front suspension. It still bends a little, but not as much as before.

Once again, please let me know if you have any suggestions for me.

[jorgeopesi]

Impressive WIP, just one advice, reduce weight it seems that it weights tons, the front wheels will suffer too much.

[Milan]

I am glad to see every update for this build.

[JLiu15]

22 hours ago, jorgeopesi said:

Impressive WIP, just one advice, reduce weight it seems that it weights tons, the front wheels will suffer too much.

Thanks! It does seem to be heavier towards the front right now as the hub is right behind the front axle, but this may change as the bodywork is installed. 

22 hours ago, Milan said:

I am glad to see every update for this build.

Thank you. As per usual for my MOCs, I will continue to make updates throughout the building process :)

[Thirdwigg]

Great job on this! It keeps getting better.

I cannot tell from the photos, are the seats rotationally fixed, or can they fold down?

[JLiu15]

UPDATE 10/27/23

Worked on the Stud.io model a little more, and now all of the metallic silver stainless steel panels are in place. I've also designed the front and rear bumpers. Haven't started working on the main bodywork yet, but the model is starting to take shape.

Thankfully, most of the metallic silver pieces are available on Pick A Brick. Still it's gonna cost around $80 to get all of them, and that's not including the discontinued ones that aren't available on there...

If you have any suggestions for me, please let me know.

Photos:

[JLiu15]

UPDATE 11/5/23

I've gotten a good amount of the bodywork done, and the model is really starting to take shape now. The front body panel was challenging as it had to account for the bevel gear for the front passenger door panel, and there wasn't an easy way to relocate it. There is a "cutout" in the front body panel for the gear to be able to rotate freely while still maintaining the aesthetics. I don't like how the headlights stick out, but the way they're placed makes it rather difficult to make them flush with the body panel and just a plate further back on the right side would interfere with the bevel gear.

Modeling the side body panels was important as this allowed me to determine where the window pillars will be so I can add a support pillar for the roof frame where there is no passenger seat. The roof frame was quite floppy last I tried putting it on due to how long it is, so the support pillars should help with that.

If you have any suggestions for me, please let me know.

Photos:

[JLiu15]

UPDATE 11/13/23

I've installed the roof frame, so the entire inner "skeleton" of the model is done. I had to do some modifications to the chassis to install support poles through the length of the model for the roof frame, as the original design was very flimsy. The frame has also be reinforced so that it is 2 studs thick for most of its length.

The support poles for the roof frame is placed at locations where they will be "hidden" by a window pillar and not be obstructed by a passenger seat. I was only able to include three pillars (two on the right and one on the left), but this gives the roof frame a good amount of support.

If you have any suggestions for me, please let me know.

Photos:

[1gor]

Can you take picture from above?

[JLiu15]

UPDATE 11/18/23

A year after creating this topic, I am close to finishing the Stud.io model. Except for the rear which I still have to design, the design is pretty much complete. I finished modeling the roof and front portions - the roof is made of Technic 5x11 panels to reduce weight (the edge is still made using curved slopes) and the destination sign is similar to the one from my previous New Flyer Xcelsior models. Designing the mirrors was challenging as the real bus has them attached to the windshield pillar, with the right one also mounted on a cantilever. This was difficult as the windshield pillars were made using rigid hoses held at an angle, which does not allow for a very robust connection. I like how the design turned out, although I will have to see if the solution is practical on the finished build.

I've attached a rendering of the model below, viewed from the front where everything is pretty much complete. If you have any suggestions for me, please let me know.

[JLiu15]

UPDATE 11/20/23

Since my previous update two days ago, I found some time to model the rear and now the Stud.io model is pretty much done. I've included a few renderings below. I'm pretty happy with how the design turned out - I may have to make some changes in the final model, but overall it should look pretty similar to the renderings.

The current part count is 6050 (I realized I forgot the side destination sign in the renderings, and this part count is with the side sign included).

If you have any suggestions for me, please let me know.

Photos:

[Milan]

Indeed, it looks very close to the original. Every line, and every broken line, seems to have been put into the model.
Again, mudguards/fenders, rear bumper and the whole rear side look incredible.
Oval windshield glass is something that is always hard to reproduce accurately. I started using transparent plates to make curved glass sections, and I love how they look, even though I understand the majority of people hate seeing them.
A bit of detailing on the front panel might help it flow even better with the rest.
The main doors...they somehow feel a bit out of place, compared to the ultra clean design of the rest of the side of the bus. Probably not much can be done, as they need to have some rigidity and functionality.

I might have missed...will the bus have any decals?