I absolutely agree with you about the small
UBK 6911 (
Zetor 5011 to 7045 series cabin). There is no way to open the roof or a side window - unless you take the door off. That would ruin you in the middle of summer when it's 38°C outside... disaster!
The
BK 6011 (wide cabin, from Zetor 5211 to Zetor 7745 Turbo) has a roof hatch that opens wide and, above all, the upper door windows can be opened outwards by about 15 cm. The roof hatch is of little use, especially as the sun is often still shining on your head. But the opening windows in the doors let the airflow in very well and it is cooler than the "cooling air" of the air sucked in above the windscreen and preheated by the engine exhaust air.
The effect on the BK 6011 is similar to that on the Zetor 7520 to 10540 where you can lock the door that opens to the front when it is opened by about 12 cm and also get cooler air than from the roof cabin ventilator.
But they both have one thing in common - if you use the opening function, it gets noticeably louder inside. So in summer you can choose between going deaf or suffocating.
The
BK 6245 (Zetor 3320 to 7340 Turbo) works the same way, but it is even better insulated and soundproofed. It is also worth mentioning that the air intake at the top of the roof has been significantly improved in terms of filtering compared to the BK 6011 (paper filter), but the air here is sucked in from below directly at the top edge of the windscreen... so it is potentially even warmer.
The older cabins from
7er and 9 series also had problems with the heat. They still had the pop-up roof but no insulated cabin floor and no proper insulation from the engine. In the summer, massive amounts of heat came from the engine and transmission...
I don't want to say anything about the appearance, for me they all have their charm, it was just the spirit of the times.
The first
UR2 Crystal cabin was of course absolutely modern for its time and Zetor was the first European tractor manufacturer to have a standard safety cabin that also looked modern and had large glass surfaces. What I wouldn't like so much is how the doors open. But that's a matter of taste, there's no arguing about that.