Sand railways of Upper Silesia · Dzierżno – Biskupice
Empty wagons are half the story
Coal travelled out of Silesia, and sand had to be hauled underground. The rolling stock ran in a closed loop: when one train returns later, the excavator stands idle even though the sand is there and the bridge works.
Loaded route → Biskupice · 20 full in transit
Dzierżno · open pit
Loading at full rate (10 wagons)
total 60 wagons in the loop · constant sum
T+0:00
Biskupice · Wojciech bridge
Unloading as they pass: 10 wagons
← Empty route to Dzierżno · 20 empty in transit
- full wagon
- empty wagon
- wagon of the delayed train
- tracked wagon (advanced settings)
A schematic model, not a map and not a timetable. One tile = one wagon; the total is always as many wagons as the fleet has.
Delay one train
Step 30 min, 0–120 min. The arrow keys change the value; the view jumps to the first shortfall.
Advanced settings
Enter a wagon number to see where it is at the chosen moment.
The whole run at once
Eight hours of the model in a single row. The dashed line shows the same circuit without a delay (for the same fleet and bridge); the fill shows the result with the delay. Click a column to set the moment.
- Upper row: wagons loaded in the step (scale 0–10 wagons)
- Lower row: shaft-side bunker (fixed scale 0–2400 t)
- Red bar: no empty wagons or no sand
The axis shows model time T from the start of the simulation (not clock time).
Full step-by-step table
| Time | Loading | Empty, waiting | Loaded route | Bridge | Queue | Empty route | Total | Bunker t | Shortfall t |
|---|
Why an empty wagon is so valuable
Hydraulic stowing pushed sand and water into the voids left by coal extraction so that the roof would not collapse. The mine therefore needed a steady supply of sand, and the sand pit a steady return of wagons. According to the V2 description, roller wagons and discharge bridges formed a matched system, so the rolling stock shuttled back and forth and could not be freely replaced by other stock.
to be verifiedThe description of the design and the dates comes from V2 and the references below (1, 2, 4); they were not reopened for this version.
- 1902The Hedwigswunsch mine in Biskupice adopts hydraulic stowing, at first using nearby sand. [1]
- 1909Borsig and Ballestrem begin to cooperate; the sand pit in Dzierżno near Pyskowice is to supply their mines. [1]
- 1913On 1 October the Pyskowice sand railway was put into operation; one of the unloading points was the bridge at the Euling shaft, later called Wojciech. [1]
- Roller wagon with a body and bottom flaps.
- The wagon's side rollers.
- Guide rails on the bridge which, according to the V2 description, work together with the rollers.
- Gravity discharge of sand as the wagon passes.
- Shaft-side bunker (in the model: a buffer of 0–2400 t).
- Water, which forms the stowing mixture.
How the model calculates and what it does not say
In each 30-min step the excavator loads as many empty wagons as are waiting (at most 10), the bridge unloads as many full ones as it can pass, and the bunker gives the mine 400 t. Wagons neither vanish nor appear: the result of each step is a distribution of the same wagons across six places, and their sum is calculated and displayed (Σ in the table).
When the return of empties is delayed, the model assumes a single track with no overtaking: the train behind the late one waits. The loss therefore depends on the length of the delay. When the bridge is stopped, the same wagons stand full before unloading. The bunker starts to empty at once; a shortfall appears only after the 1200 t buffer is exhausted (at T+2:00 for a 120-min delay, at T+5:00 for the return of empties).
The result is not a reconstruction of a real shift or of a 1913 timetable, and it does not explain the technology of stowing underground. The bunker does not make up losses, because delivery (at most 10 wagons per step) equals withdrawal.
What was removed from V2: automatic playback (replaced by the whole run visible at once), three ready-made scenarios and a separate parameter panel (replaced by a single delay and two advanced settings), and the Commons photograph embedded in the page (the link remains in the sources). In V2 some values were hard-coded and the empty route was calculated as the remainder of the fleet; here every step follows from the rules.
Model assumptions
- Step and horizon
- 30 min; 17 states, from T+0:00 to T+8:00.
- Train
- 10 wagons (V2 counted 3 trains of 20; here 6×10, because the step is shorter).
- Wagon capacity
- 40 t — an example value from V2, to be verified
- Loading
- max. 10 wagons per step (20 wagons/h).
- Bridge
- 20 wagons/h by default (10 per step); adjustable from 10 to 30 wagons/h.
- Travel time
- 2 steps (60 min) each way, as in V2.
- Bunker
- start 1200 t, capacity 2400 t, withdrawal 400 t per step (values from V2).
- Return route
- a single track with no overtaking — a V3 assumption, to be verified
- Not modelled
- work shifts, breakdowns, shunting, track lengths, real timetables, work underground.
Bridge capacity, travel time and wagon capacity require separate sources. The transport diagram does not by itself explain the stowing technology.
Sources and verification status
The references were carried over from V2. Their contents were not opened when this version was built, so they are not presented here as verified.
- Narodowy Instytut Dziedzictwa, „Most zsypowy — samowyładowczy Wojciech” [National Heritage Board of Poland, “Discharge bridge — self-unloading Wojciech”] — dates 1902/1909/1913, guide rails and roller wagons. to be verified
- Państwowy Instytut Geologiczny, „Piaski podsadzkowe” [Polish Geological Institute, “Stowing sands”] — hydraulic stowing. to be verified
- Koleje Śląskie, „Kolej piaskowa — co to?!” [Silesian Railways, “The sand railway — what is it?!”] — scale of the network and relics. to be verified
- Stacja Pyskowice, „Historia kolei piaskowych” [Pyskowice Station, “History of the sand railways”] — shuttle circuit. to be verified
- Photo: Petr Štefek, Wikimedia Commons, CC BY 3.0 — a contextual photograph from another sand pit (Ciężkowice), not embedded in this page. to be verified