falconluan

Agreed with @Zerobricks and @1gor, the 12T and 20T gear will skip at even moderate stress. I've tried similar setup during building my Axion TT not long ago. I used this setup at the rear axle, and my setup was more secured than yours in the pics. The 12T gear was fully enclosed all around, I also secured them vertically. However, they still skipped. The problem here is the 20T gear which drives diff is only half secured. When the rotate direction is pushing the gear apart, the 20T gear will bend away from the diff side and skip.

I think a lot of things are sacrificed for the front hitch, especially the room took by the two small LAs. The 8R has a very unique shape at the front, which currently is not shown on your version.

Very promising progress you made here Especially packed lots of motors/functions in such tight space. Lots of 8R have independent suspenstion which I failed to achieve in my version, I was hoping the new suspenstion parts can help, seems still very challenging, unless get rid of the horizontal placed diff, which will take extra space in the chassis and lost extra realism...

This is a good direction I think I can configure the two motor with below functions: High speed gear/RWD Low speed gear/AWD Front and rear linkage Aux PTO By doing so, I can still have the benefit of using C+ L motor as servo to control steering

I'm thinking of adding steering to the power split functions as well. By doing so, Pros are can still have 2 driving motors, no 3rd party hardware involved, Cons are can not use C+ L motor's servo function(or need complex programming), steering is lost when switching to functions, high/low gear and AWD/RWD drive modes are lost, large structure change needed I like the chassis better than its bodywork myself

No worries at all

Fastrac has equal size of front and rear wheels which is a little bit simpler to deal with.

High speed/RWD: 12:28, 20:16 to the 62.4mm tires, so it's 15:28(0.53)to the rear tire Low speed/AWD: 20:28 to the central diff, then the same ratio to rear tire, result is 0.38 to the rear tire. From central diff to front tire, 12:20, 12:20, 12:28, about 0.11 to the front 107mm tire, I know the wheel speed diff is too much here, just to let the low speed gear runs at a lower speed and the front tire gets more torque... If gets rid of one 12:20 pair gears to the front axle, the ratio will become 0.18 to front tire, wheel speed will be more balanced while speed diff between gears will be less...

Thank you all for your kind words I think that's because I've practice some times in my T8, magnum half track and the 8RX MOCs

Now it is finished! Instructions at: https://rebrickable.com/mocs/MOC-256008 Introduction video: Feature introduction: Some more pics: Coming plan: Will make some crude implements to further demo its functions Also I want to make a C+ version, however, due to the C+ connector cannot be stacked, it will be driven by only one C+ L motor, need to adjust reduction ratio to have enough torque, it weights 1.8KG, hope that one L C+ motor can drive it fine...

Both digital and brick version are finished, making instructions for it now

11 studs is very challenging, with 5 studs width of hood(and probably 6 or even 7 studs), there is little room for fender support when the axle is swinging. I can have a 13 studs axle on the TT, however, with the 8 studs wide hood at the axle position, the room is still rather limited. And here is the tractor looks like now:

Agreed with @1gor here, 107mm tire at the front may be the smallest possible scale for a Lego RC tractor with multiple remote controlled functions without using 3rd party small motors, for example, if you want: AWD with central diff, rear and front hitch, rear and front PTO, the list doesn't even include front loader, at least I failed to do so if keep the correct proportions strictly.

Lucky that I have some lego time this month so I take the chance and built a lot, things will be different next month though... Among the tractor brands I've built moc of, CLAAS shares the most information in their brochures, for example, they included a botom view in the old terra trac brochure, I got most of the width info from that picture Tractor building is FUN!

Some update: Redesigned the funtion distribution due to gear arrangement limitation and playable consideration, now the high speed gear/RWD mode is grouped with "rear hydraulic simulation", the low speed gear/AWD mode is grouped with rear and front linkage up and down. Also added a manual switch to enable/disable the front linkage operation, since if a front weight is equiped, lower and lift it together with rear implement doesn't make sense. Am thinking about extend the front drive shaft into a front PTO at the bottom of chassis, however, it seems that tracked tractor is not suitable for mowing work, so the front PTO is not very useful... Now using the 62.4 truck wheel as rear sprocket for better proportion, tested driving it for some time, its traction is ok and didn't lose the track on it. @eric trax I also covered the hollow part of the hood with some parts, I think it looks better Not a fan of the curved tank @1gor, I will put the flat 3x7 panel back and get rid of the 3x5 curved panel to make it completely flat. A new video:

Hi @eric trax, looking forward to see the version from professional hands You are right, my rear rim is larger, but I don't think it is too much larger. It's hard to get a blueprint of the new 9.450, below are what I've been using for the building: Seems that the dimension of rear track doesn't change in new version. I measure the height including track to compensate the meshing differenence between real one and lego parts, so the result is 8.5L at the front and 10.1-10.3 at the rear. With the large sprocket, the front size is pretty close. When using the 75mm offroad tire, the rear height is about 11.5L, which is around 1L larger than it should be. The 62.4mm tire(32019) or 68.7mm tire(52985, 61480, 44771) may be more closer in term of size, but their tread is more flatter than the 75mm tire, which cause them prone to slip against the tracks. That's why I chose the larger tire. I made the whole track length 1L longer trying to compensate for the larger rear wheel. It is clear that the result is not good enough. I'll try to test those tires more to see if they can hold the weight in good shape to fix this anyway. Thank you for pointing this out anyway.

@Jundis Yes, the 90° angled connector won't fit the angle there, but I got your point and it can be like this: This is a little bit off in propotion but it has the right curve and can leave more room for the headlight in the side. Thank you for the idea!

Looking forward to see your progress on the Fastrac 1:15 is a pretty large scale for farming things other than tractor, such as, a 7.5m wide cultivator will be 50cm in 1:15, no need to say the big trailors, good luck on that I'm planning to build something for the Axion TT, especially something can demo its functions, a triple mower is an ideal candidate, but 9m+ rear mower will also be 50cm+... Yes, still one motor left to be mount, but it will be a PF M motor, since it only has 2 gears and functions to select, I will use the gear changing solution in 42129 for it.

Yep, I'll try the curvy one then. Funny that when I first saw the angle new part, I didn't think it would be so much useful....

I found some broken parts when building stuffer these days too. There are cracks at parts like 6536 and 32039, my first lego part dates back to 2013, maybe more than 10 years is too old for a part.

I am not fan of the tank looks now either. I will give the curved part a try, although the tank side of the real tractor is a pretty straight line, trade off, always, I know

The hood and side tanks are done, still lots of work ahead @1gor you are sharp on shapes The front slope of privous version was too big, now I think it looks right

Thanks. Your Optum will be bigger than this one, looking forward to see your progress on it. I think technic fits tractors well too, tractors are more tolerant on technic holes than cars and have more functions to be implemented. After all the tractor mocs I did, I feel that they are not popular than cars for sure Thank you. I tend to build as much technic as possible. Maybe because I like a more pure technic style(which seems not align with the trend of official sets), or simply maybe because I don't have many system parts to play with...

What do you think of this hood?

I am also a farming simulator player and it is what inspired me to start building tractor MOCs. I've built some AWD halftracks before in smaller scale(around 1:18) if you're interested: Case IH magnum: https://rebrickable.com/mocs/MOC-192623/ New Holland T8: https://rebrickable.com/mocs/MOC-197351/ And a "full track" John Deere 8RX: https://rebrickable.com/mocs/MOC-212799/ They are smaller so they don't have as much functions