[WIP] Bergmann Swivel Tip Dumper

[JLiu15]

Just made a MOC based on a real vehicle - the Kalmar forklift. Well, how about another one? This will be a model of the Bergmann C815s (formerly Bergmann 3012) in the swivel tip dumper configuration. It will be my first MOC to use Control+, with 4 motors to control drive, articulated steering, dump bed rotation and dumping. It will feature AWD with planetary hubs from the 42099 set, a sprung front axle (live axle), and will tentatively feature pneumatic dumping to reduce the amount of driveshafts for functions.

https://www.bergmann-dumper.de/pdf_files/folder/folder-sammel-2018-eng_826_9.pdf

https://www.maskinia.se/upload/products/documents/neu-2020-folder-c815s-h03-10452-11758-en-web-einzelseiten.pdf

Note that the name of this vehicle was Bergmann 3012 prior to 2020. My model will be the current version of this vehicle.

There's very limited space for electronics and mechanisms here - I already had to scratch the idea of including a 4-cylinder fake engine. I anticipate this model being packed to the brim with mechanisms - for instance, the steering motor (which will be a C+ L motor) will sit back to back with the drive motor, transferring drive through a driveshaft directly below them as to not interfere with the suspension's travel. The C+ hub will sit below the steering motor, directly in front of the front axle. I'm hoping this won't cause the suspension to sag or anything - there's literally nowhere else in the model I could feasibly put it.

So far, I have the front axle and parts of the chassis in front of the articulation joint completed. It seems to be well reinforced at this point - thankfully the C+ motors have a lot of attachment points so I can see them supporting the chassis here pretty well. The articulated steering will be done by 2 mini LAs - this was quite a challenge for me to figure out, as they sit directly in front of the gears for the drivetrain. I had to make sure the mechanism is sturdy, can be geared easily, and not be too high as the body slopes downward right here. They feel a little wobbly, but a test with some beams representing the rear section of the chassis shows that there's little play in the mechanism. The LAs will be installed like a 'Y' (I find this to be the best angle for them), which isn't the most realistic as the real-life counterpart seems to have them pointing rather parallel to the chassis and are installed lower, but given the limited space in the chassis I have to make some compromises I guess.

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

Photos:

Edited January 28, 2022 by JLiu15

[Jundis]

Looks very good so far :-)

Depending on the speed of the small linear actuators, you maybe have to change the transmission gears below to 20/12 combination to speed up the articlated steering.

What kind of wheel are you intending to use?

[JLiu15]

3 hours ago, Jundis said:

Looks very good so far :-)

Depending on the speed of the small linear actuators, you maybe have to change the transmission gears below to 20/12 combination to speed up the articlated steering.

What kind of wheel are you intending to use?

The small LAs for steering are driven by a C+ L motor geared 1:1, which I find to be the perfect speed - not too fast, not too slow. I'll be controlling it with the BuWizz app which has proportional control, but I still prefer articulated steering that isn't too fast to ensure precise control.

Wheels will be CLAAS Xerion wheels with gray rims, as well as a small disc in the middle (I'm thinking of using this piece). I was debating between CLAAS wheels and Unimog wheels, but CLAAS wheels are more realistic here imo.

[suffocation]

Great start - you always manage to keep your builds really clean. You've also made the rear axle mostly form-locked, something that's all too often overlooked.

[Rudivdk]

Nice start, I like your axle design. But since you are going to motorize it, wouldn't it be better to use the newer stronger RC-differentials (with the red gear on it)? Or was your choise for these older diffs intentional?

[JLiu15]

2 hours ago, suffocation said:

Great start - you always manage to keep your builds really clean. You've also made the rear axle mostly form-locked, something that's all too often overlooked.

Thanks!

btw what do you mean by "form-locked"? Do you mean the front axle? I've only built the front axle so far - nothing behind the articulation joint is built yet.

1 hour ago, Rudivdk said:

Nice start, I like your axle design. But since you are going to motorize it, wouldn't it be better to use the newer stronger RC-differentials (with the red gear on it)? Or was your choise for these older diffs intentional?

Unfortunately I don't have any of the newer differentials. I wish I had them, but since they're relatively new they're still quite expensive on BL. The 12:28 gear reduction would also be a bit overkill together with the ~5.4:1 reduction in the planetary hubs imo.

[suffocation]

1 hour ago, JLiu15 said:

btw what do you mean by "form-locked"? Do you mean the front axle? I've only built the front axle so far - nothing behind the articulation joint is built yet.

Silly me, I mistook it for the rear axle - I even misread your intro. I need a brain transplant

A section is form-locked when the bracing is done using beams (or connector combos) rather than relying only on friction from pins and/or axles. Didumos69 is a master at form-locked builds.

[JLiu15]

2 hours ago, suffocation said:

Silly me, I mistook it for the rear axle - I even misread your intro. I need a brain transplant

A section is form-locked when the bracing is done using beams (or connector combos) rather than relying only on friction from pins and/or axles. Didumos69 is a master at form-locked builds.

Oh of course, I always make sure to reinforce my builds as much as possible, especially in load-bearing situations such as axles. In fact, sometimes I even find myself reinforcing my builds too much 

Edited July 16, 2020 by JLiu15

[JLiu15]

UPDATE 7/16/20

I've made some progress on the front section of the chassis. The steering motor and mechanism is in place, the suspension is fully set up, and the articulation joint is complete with turntable and linear actuators attached. I was worried the articulation joint would be a weak spot as the pivot point is connected by pins rather than e.g. small turntables, but I've found it to be pretty robust in all 3 axes of rotation.

The only thing left to do in the front section of the chassis is to attach the C+ hub. The chassis will dip downwards at the front to create an attachment point for the hub, and I anticipate a solution that allows for easy removal of the hub for battery replacement. I might also add a working steering wheel as the steering motor's output sits so close to where the steering wheel will be, but it'll be a little unrealistic in that the steering wheel will continue to rotate past the left/right extremes of the steering mechanism. Still, it'll be nice to throw in some extra functions/features.

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

Photos:

Edited January 28, 2022 by JLiu15

[Rudivdk]

Looks good, you've been able to package all systems very tightly and very clean! Those C+ motors look like real solid structural braces, your chassis will be pretty stiff I assume.

Is the steering pivot only swiveling left-right, and is up/down or rotational movement being handled by the suspension? Or is the entire back section of the chassis attached to that large turntable (allowing the rotational movement)?

[JLiu15]

3 hours ago, Rudivdk said:

Looks good, you've been able to package all systems very tightly and very clean! Those C+ motors look like real solid structural braces, your chassis will be pretty stiff I assume.

Is the steering pivot only swiveling left-right, and is up/down or rotational movement being handled by the suspension? Or is the entire back section of the chassis attached to that large turntable (allowing the rotational movement)?

The articulation joint allows movement in the axis of roll (hence the turntable) but not in the axis of pitch. And yes, the entire rear section of the chassis will be attached to the turntable.

[Jundis]

14 hours ago, JLiu15 said:

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

You should be careful not to place the hub to far in front or the vehicle gets very nose heavy I think... Also you may even need to double the hard shock absorbers or add a soft one per side. Just be prepared :-)

Edited July 17, 2020 by Jundis

[JLiu15]

8 hours ago, Jundis said:

You should be careful not to place the hub to far in front or the vehicle gets very nose heavy I think... Also you may even need to double the hard shock absorbers or add a soft one per side. Just be prepared :-)

Do you know how I could incorporate double shock absorbers in a suspension design like this? I've never seen more than one per wheel used on live axles so any advice is appreciated here - there's just so many different planes involved unlike an independent suspension or something.

[JLiu15]

UPDATE 7/17/20

The front section of the chassis is essentially complete. I've installed the Control+ hub and added a mechanism for the working steering wheel - the hub sits in front of the front axle, connected to the chassis by four of these. They have enough clutch force to keep the hub firmly in place without the risk of it falling out while driving, but also allows the hub to be removed for battery replacement. The hub may appear to sit way too low in the chassis, but a stud higher and it would interfere with the 24T gear connecting the steering motor to the steering mechanism. Also keep in mind that this is without wheels - when the wheels and bodywork are in place, I doubt the hub would protrude much from the underside of the chassis - one stud at most.

Even with the hub in front of the front axle, I have not noticed any issues with the suspension. In fact, the hub is actually not touching the ground here - it's being kept off the ground by the front axle. However, I am ready to modify the suspension at any time if the suspension starts sagging (e.g. when the bodywork is being built). I'm not sure how to use multiple shock absorbers on each wheel in a live axle suspension setup like this - the shock absorbers have to move in multiple planes, which makes attaching the shock absorbers more difficult than a suspension with shock absorbers moving in a single plane, such as a double wishbone independent suspension. Any suggestions on how to incorporate dual shock absorbers per wheel here is appreciated 

Photos:

Edited January 28, 2022 by JLiu15

[Pattspatt]

58 minutes ago, JLiu15 said:

Any suggestions on how to incorporate dual shock absorbers per wheel here is appreciated 

A simple solution could be to add another spring right next to the existing, secured with a 3L axle with stop at each end.

[JLiu15]

16 minutes ago, Pattspatt said:

A simple solution could be to add another spring right next to the existing, secured with a 3L axle with stop at each end.

That's a good idea, haven't thought of that 

[Rudivdk]

1 hour ago, JLiu15 said:

That's a good idea, haven't thought of that 

On a (yet unfinished) build of mine I use instead of your , with the center hole attached to the chassis (tan pins) and a spring on both the grey pins of the connector. Keeps it nicely symmetrical. Works best with old versions of this part, as the pins on those have tremendous friction power making it nearly impossible to lose the spring 'in operation'.

In your build it will make the spring assembly 2 studs shorter compared to current setup, so you'd have to rearrange some stuff to accommodate it...

[JLiu15]

40 minutes ago, Rudivdk said:

Works best with old versions of this part

There's two versions of this part?

41 minutes ago, Rudivdk said:

In your build it will make the spring assembly 2 studs shorter compared to current setup, so you'd have to rearrange some stuff to accommodate it...

I don't think that should be too difficult. The C+ motors have got more than enough attachment points, so I could easily reinforce the area around them if I want to lower the upper attachment point of the shock absorbers. Once again I'll only upgrade it to dual shock absorbers if the suspension starts sagging under the model's weight, so I'm not even sure if I'll make any changes to the current suspension setup.

[Rudivdk]

58 minutes ago, JLiu15 said:

There's two versions of this part?

I don´t think it´s two versions, more likely just a slightly different mixture of ABS or perhaps the mold starts wearing a bit, but it seems the older ones have a bit more friction power to them (aka harder to pull apart)...

[Jundis]

2 hours ago, Rudivdk said:

On a (yet unfinished) build of mine I use instead of your , with the center hole attached to the chassis (tan pins) and a spring on both the grey pins of the connector. Keeps it nicely symmetrical. Works best with old versions of this part, as the pins on those have tremendous friction power making it nearly impossible to lose the spring 'in operation'.

In your build it will make the spring assembly 2 studs shorter compared to current setup, so you'd have to rearrange some stuff to accommodate it...

This is so funny, cause this has been my first thought for the connection :D

But if it works for now, leave it. Sometimes, if the model is a little bit more "bouncy", it actually has a nice and more realistic feel than a rather stiff version.

[JLiu15]

1 hour ago, Rudivdk said:

I don´t think it´s two versions, more likely just a slightly different mixture of ABS or perhaps the mold starts wearing a bit, but it seems the older ones have a bit more friction power to them (aka harder to pull apart)...

AFAIK all of mine are of a similar mold (black, gray, red) except for some gray ones from the 42099 set that have a thicker wall for the pins.

29 minutes ago, Jundis said:

But if it works for now, leave it. Sometimes, if the model is a little bit more "bouncy", it actually has a nice and more realistic feel than a rather stiff version.

I agree. I'll probably leave it. I'll only change it if I notice the suspension having a hard time springing back up when compressed.

[Rudivdk]

Just now, JLiu15 said:

except for some gray ones from the 42099 set that have a thicker wall for the pins.

Yeah, I think these are the newer, 'softer' ones... Probably only 1 year in production sofar, so all others are 'older' then...

Anyway, as Jundis said, don't change anything just yet until you are sure you need it, but keep it in mind when building further (don't occupy space you might need for additional springs) and you're good.

[JLiu15]

2 minutes ago, Rudivdk said:

Yeah, I think these are the newer, 'softer' ones... Probably only 1 year in production sofar, so all others are 'older' then...

I noticed the same with the crank pieces in the set - they too had a thicker pin. In fact a lot of pieces appeared different - for instance the differentials in the set were glossy instead of matte like my other ones (but tbf those were my first 28T differentials in 5 years).

Tbh I don't really like the thicker pins - I prefer thinner collars on pins. I tend to avoid the pins from older sets I have when building MOCs (e.g. 8436) for this reason as they have a significantly thicker collar, unless I need black 3L pins ofc.

[Rudivdk]

3 minutes ago, JLiu15 said:

I tend to avoid the pins from older sets I have when building MOCs

I actually do the same. I have also noticed that the older pins can't fit a bar inside because of the ticker the collar, while the newer pins can (see the grille attachment in the 42043 Mercedes truck  for example). With this, you can put 2 pins on a 4l bar, creating a 4l pin effectively. I haven't used it much, but I like the option. This only is the case on friction pins though, smooth pins have a stop inside, in the middle of the pin, so you can't put a bar all the way through.This is even the case for the newer, thinner type.

Enough rant about pins and OCD, back to your MOC... Have you already put wheels on to see how the suspension behaves when sitting higher? And put something heavy on top to simulate bodywork weight? This is what I often do to get an idea early on... It's not science, but still a reasonably good indication of what to expect.

[JLiu15]

9 minutes ago, Rudivdk said:

Have you already put wheels on to see how the suspension behaves when sitting higher? And put something heavy on top to simulate bodywork weight? This is what I often do to get an idea early on... It's not science, but still a reasonably good indication of what to expect.

I have put the wheels on to see how long the chassis needs to be, but I haven't tested bodywork weight. It's really unpredictable how heavy the bodywork will be, as you never know what/how many pieces you'll end up using.