[WIP] Grimme Varitron 270 - potato harvester

[eric trax]

It's been a while since I presented my last large model - the Krone BigX 770 forage harvester.

I decided that this time I would start building something more demanding. It will be a potato harvester Grimme 270. Where did this idea come from? On one Bricklink order, a seller made a mistake and sent me three Power Puller rims. I took that as a sign to start building this three-wheeled monster.

 

There are several configurations of this machine with different wheels and even a track only on the right side instead of the wheel. I decided to build a classic version with wide tires. The biggest advantage of this model is that the engine and mechanisms are in the thrust on the right. It's the perfect place to make use of it and use it as the main frame for the entire model. It's the perfect place for all engines. This is very important because I would like the combine to be solid and able to operate at exhibitions.

I would like the harvester to actually harvest "potatoes" that will be brick round 1x1 or small beans. This is why I gave up building the larger Varitron 470 terra track. The 270 version gives you a better chance of it running like the real thing. However, this is a huge challenge. The model will use the Power Functions system controlled by 2 or 3x Sbrick. This is my favorite setup. The combine will have 10 functions and will use 8-11 channels depending on how I manage to place the mechanisms. This will be:

- driving
- turning
- rear axle width extension
- lifting the collecting belt
- control and drive of the haulm cutter (this is the front tool)
- unfolding the main tank
- unloading belt drive
- fine haulm conveyor drive - belts at the rear
- main belt drive
- lighting

 

I started the construction with the most difficult element - the rear axle. I really wanted to keep the width change function. After building a dozen or so versions, I finally decided on one without a differential and with one-wheel drive. Instead, it has two actuators that stabilize the right wheel. This is very important because about 70% of the model's weight will be loaded on this axle.

  

 

 

The GIF below shows how the resize function works.

You won't have to wait that long for the next updates. This model is one of the two major projects for 2022 :)

 

 

Edited December 18, 2021 by eric trax

[1gor]

At least it is nice to see that someone of us agriculture equipment lovers find some te for mocing. There are new CV joints in Zetros that enable axle sliding, but I don't have Zetros (not even hubs from 42099) so I don't know if the sliding length is enough for you to make rear wheels drive (one wheel drive is a bit odd IMHO or you could try to power rear wheels directly?

I was thinking about this part

https://www.bricklink.com/v2/catalog/catalogitem.page?P=77590&idColor=86#T=C&C=86

(Hm... perhaps with that solution axle would be to wide and I suppose that new light bluish gray wheels like one from land Rover doesn't help you)

[eric trax]

2 hours ago, 1gor said:

There are new CV joints in Zetros that enable axle sliding, but I don't have Zetros (not even hubs from 42099) so I don't know if the sliding length is enough for you to make rear wheels drive (one wheel drive is a bit odd IMHO or you could try to power rear wheels directly?

I tried to build a version with these shafts. However, they may extend by two studes. I needed three studs. I don't want to use 3D printed parts. I also tried to use z8 gears without friction but was not happy with the effect.

Perhaps before I finish building this model I will make an axle with two wheel drive.

[2GodBDGlory]

The model looks like it'll be pretty cool! Is there any reason you are preferring the Power Puller rims over newer ones?

My TC21 entry also has varying width; my solution to drive it was to put bevel gears on the wheel hubs to make the drive longitudinal, and then use long axles with CV/U joints at each ends. This way, when it contracted, I only had to deal with a relatively small amount of length in the longitudinal axles. Perhaps something like this could work here, but maybe you need something more compact. Also, it looks like only one of your wheels moves relative to the body, which may change things.

[Jeroen Ottens]

Great to see a wIP topic from you Eric. Looking forward to following this. That sliding wheel is a challenge indeed. It looks like the best compromise between rigidity and functionality to me.

[1gor]

9 hours ago, eric trax said:

I tried to build a version with these shafts. However, they may extend by two studes. I needed three studs. I don't want to use 3D printed parts. I also tried to use z8 gears without friction but was not happy with the effect.

Perhaps before I finish building this model I will make an axle with two wheel drive.

I thought that axle should extend both right and left... otherwise you'll get differential "floating" to just one side and IMHO it should stay in center...

I suppose there is only possible to connect 42099 hubs with new CV joints...

[Rebel_Lego]

Interesting project! Finally some agricultural equipment again.

I wonder if you let two wheels extend using cv-joints from the Zetros could it work?

2 studs + 2 studs = 4 studs

[1gor]

8 minutes ago, Rebel_Lego said:

Interesting project! Finally some agricultural equipment again.

I wonder if you let two wheels extend using cv-joints from the Zetros could it work?

2 studs + 2 studs = 4 studs

That was my idea in the first place, but question is if such solution is not to wide...

Based on information here https://www.grimme.com/uk/producttypes/selbstfahrende-erntetechnik-kartoffel/varitron-270-platinum-terra-trac

Width is variable from 3300 to 4023 mm; so in this case (if I remember correctly all models are 1:17 ); Lego model should have overall width from 24 studs (maximal compressed) to 30 studs (maximal extended) over tires...

I hope that I didn't bring more confusion @eric trax

[Jundis]

What a ambitious project, thanks for sharing the building process with us :-)

For the axle extension problem: Did you think about using two motors (one for each wheel)? So the motor just moves with the wheel...?

As a non-puristic solution I suggest just using 20 bevel gears or 24 gear as somehow they seem to float rather easily on axles in contrast to other gears. I have 2 used ones in my collection that allow movement with nearly no friction...

[chlego]

On 12/19/2021 at 9:01 AM, 1gor said:

I thought that axle should extend both right and left... otherwise you'll get differential "floating" to just one side and IMHO it should stay in center...

I suppose there is only possible to connect 42099 hubs with new CV joints...

Thought the same, it wouldn't be rigid enough I believe... Or you would have one wheel that sticks out on one side.

Following!

[eric trax]

On 12/19/2021 at 1:51 AM, 2GodBDGlory said:

The model looks like it'll be pretty cool! Is there any reason you are preferring the Power Puller rims over newer ones?

Yes, there is a difference in the shape of the tire. By using power puller rims, you make the tire look bigger. Below is a comparison:

On 12/19/2021 at 9:41 AM, Rebel_Lego said:

I wonder if you let two wheels extend using cv-joints from the Zetros could it work?

2 studs + 2 studs = 4 studs

The axis is 11 studs wide. The joint CV you are writing about is 4 study wide. There is no space for the differential and its mounting. Besides, only one wheel, not two, comes out.

On 12/19/2021 at 9:56 AM, 1gor said:

Based on information here https://www.grimme.com/uk/producttypes/selbstfahrende-erntetechnik-kartoffel/varitron-270-platinum-terra-trac

Width is variable from 3300 to 4023 mm; so in this case (if I remember correctly all models are 1:17 ); Lego model should have overall width from 24 studs (maximal compressed) to 30 studs (maximal extended) over tires...

I hope that I didn't bring more confusion @eric trax

Your calculations have a fundamental error. Dimensions 3300 to 4023 mm do not describe the axle width. The wheels do not match the width of the machine. They are narrower. The right wheel on a real machine extends about 40 cm ;)

Finally, 40 cm is 3 studs in 1:17scale. Perhaps, I will limit axle extend to two studs and use the zetros shaft.

On 12/19/2021 at 8:51 AM, Jeroen Ottens said:

Great to see a wIP topic from you Eric. Looking forward to following this. That sliding wheel is a challenge indeed. It looks like the best compromise between rigidity and functionality to me.

Thank you. Hopefully there will be some interesting discussions here during the building process.

On 12/19/2021 at 10:21 AM, Jundis said:

For the axle extension problem: Did you think about using two motors (one for each wheel)? So the motor just moves with the wheel...?

I tested this solution. It seems good, however, it creates a problem with the mounting of the axle-extending actuators. I liked this solution and maybe I will come back to it again if I have a better idea how to build this element.

Edited December 24, 2021 by eric trax

[1gor]

You could be right; nowhere is written that it is worth over tires; speaking about tires - very interesting solution for mudguards on Fastrac 3185