Air Hoe Seeder Physics: Real-Life vs. MR-Schema

[Kartoffelhose]

Hey guys,

I mostly play on NA-styled maps with North American tractors and implements. I’ve already edited a lot of mods to fit the More Realistic (MR) schema, and it’s been working well so far. However, the rolling resistance in the field feels a bit off sometimes, so I’ve been experimenting with a setup I know from real life (IRL) to illustrate what I mean.

Let’s take a 40ft airseeder (hoe) with 10-inch spacing in loam at 8 km/h (5 mph), seeding wheat at a depth of 1.4 inches (3.5 cm). This was my standard setup back in Canada in 2015.

I researched the draft force per tine based on PAMI/ASABE data for no-till conditions, which is approximately 285 lbs (1.27 kN).
Multiplying 1.27 kN by the number of tines (48) gives a total tool draft of ~ 61 kN.
I also adjusted the weights, CoM, and PTO max power accordingly. I set the workingspeed @10km/h

As a referance: I used to pull a 380 bu TBT cart + 40ft (10 in) toolbar + 3000 US Gallon NH3 nurse wagon at a 1.4-inch depth @ 4.0-4.5 mph (6-7 km/h) under 100% load (no-till). The tractor was a Case 9270 (~330 hp engine output) on 520 duals, operating in both no-till and light cultivated (stubble) conditions.

I recreated this setup in-game on flat ground under three conditions: no-till, stubble, and cultivated. I set the ground wetness to 0. To pull the rig, I used a Versatile 976 (MR) on 520 duals. It has 30 hp more than the Case but weighs less, making it the closest MR-default vehicle available for comparison.

Results:

No-till: 61 kN, 7 km/h max, 15% slip.

Stubbled: 27 kN, 8 km/h max, 8% slip.

Cultivated: 27 kN, 8 km/h max, 8% slip (same as stubble).

No-till feels pretty spot on. However, stubbled ground feels quite off. IRL i would be going closer to 10km/h. I suspect the rolling resistance is too high; the rig sinks in too much, making the ground feel as soft as deep-cultivated soil. As for the cultivated ground, it feels the same as stubble. While I never pulled this specific setup on heavily worked ground IRL, I’m not sure it should feel this sluggish.

What are your thoughts on the rolling resistance for stubbled and cultivated ground?

This isn't a complaint, just some thoughts for discussion. I’m really thankful for MR and I think Dural has done a fantastic job with it!

[quadural]

Hi,

I think you should take into account the "virtual wheel" if there are any (invisible wheelshape)
You should also "fine" tune the toolbar visible wheels.
Indeed, IRL, at work, the support wheels are not bearing the full weight of the bar => most of the weight is on the ground (weighing tyhe seeding elements)
In game = most of the time (because the friction system is really awful), the implements are not slidind on the ground = all the weight is supported by the visible wheels or invisible ones)

But : since MR engine takes into account the wheel size and width to compute the rolling resistance depending on the terrain => the support wheel or the invisible wheel is overloaded => huge rolling resistance because IRL it would mean the wheel is penetrating the ground up to the "axle".

First thing first = enabling the debumode ingame and checking the rolling resistance factor applied to all the implement wheels.

If this is really the problem, the easy fix = increasing the wheel physics width for "virtual wheels" (invisible ones)
and if this is not possible = decreasing the powerConsumer draftforce to take into account the increased wheels rolling resistance

Maybe I should add a new wheel physics parameter to allow the "modder" to apply a factor to the width of the wheel taken into account for rolling resistance purpose (without impacting the vehicle stability = without modifying the force contact point)

Final note =
when I see your figures, it tells me there is something wrong because you get the same speed with 61Kn draft and 27kn draft (even if we are talking of different ground state)
And how is it possible to get only 8% slip on "loose" field compared to 15% on stubble ? (make sure the tractor is at full power in each case => look the avg fuel consumption for example. because it looks like the tractor is not delivering its full power = limited by max working speed of the implement )

To say it differently = if a given tractor is giving its full power at the same speed on hard ground and loose ground, it is 100% guaranted to get more slippage on the loose ground (with less net draftforce of course)

best regards

[Kartoffelhose]

"To say it differently = if a given tractor is giving its full power at the same speed on hard ground and loose ground, it is 100% guaranted to get more slippage on the loose ground (with less net draftforce of course)" - Yes, that is exactly what I expected to see.

I didn't have much time to go through the XML files, so I just took the MR 8R and the MR Horsch Tiger onto the same field and drove around. Engine load and fuel usage were at 100%:

Unworked ground: 9 km/h, 17% slip, 85 kN

Worked ground: 10 km/h, 10% slip, 60 kN

Grass: 10 km/h, 7% slip, 89 kN

The results are fairly consistent. It seems like I have a general problem that is not related to the implement itself... I will look into it further when I have more time!