Hi Paul did you say 4 or 40?
Below - 40 seater from Huntley colliery was on 3'6 but now on 2' gauge seated 5 wide across.
It doesn't matter which way you pack the miners into the car, it weighs that much that the centre of gravity is low and always between the rails so it won't tip,
The seating is less than salubrious for up to a 45 minute ride each way each shift. Most miners took their own cushions.
A closer look at the seating
And now for a 3' 6 " gauge 14-seater battery-electric self propelled mancar. This is the remains of a 1964 vintage EM Baldwin "jitney". As originally supplied it had no roof and the ends were eventually sheeted with clear (glass/perspex?). It was basically a battery-powered flatcar.
A photo at the top of Page 24 in the "Built by Baldwin" book shows it in service at Huntley colliery minus a roof but with a metal framed perspex? windscreen at each end that was just higher that the top of seated miner's hard hat.
Riders sat around the edge of the vehicle. Miners sat 3 at each end, with a seat on each side of central entry point on each side. The vertical cylinders are the sand containers for the sanders.
This photo shows the brake and sander arrangement on one axle, probably adjacent to the driver's position.
And here is where the missing motor and clip-in battery pack used to be - between the 2 axles - The battery ran longitudinally down the middle of the car. The photo mentiond shows the battery appearing to be 4"- 6" thick central divider and it was about shoulder height against a seated miner. The motor sat transversely under the battery and drove the axles by chain.
Unfortunately the book does not have plans for the "jitney". The diesel cars that replaced these were about 4'6" high with crew compartment on eac end that was 5'6" long on a 4' wheelbase. The inboard end of the crew compartment was over the wheelcentre of each axle. This gave a total length of just under 15' for the diesel manxcar.
A smaller GN15 version could be made easiest by bolting a 2-seat width crew compartment to one or both ends of one of your small balttery electric locos. Driving controls would be on each of the outboard crew compartment bulkhead. As a fleet operator this would standardise your battery and traction components.
These units ran as singles and were rarely coupled together, so coupler overhang should not be an issue.
As to weathering the inside, yep the only couple I have seen inside of were almost solid dust/ mud to boot top level (steel-capped rubber gum boots were mandatory safety equipment) , seats were dusty but reasonably clean but the walls were smudged to shoulder level. There we greasy/ muddy hand prints around the door area where miners grabbed the door opening as they entered and left the cars.
I have still been unable to find a photo of any of the EM Baldwin, Titan or Gemco Aussie-built battery man cars. One of the Gemco battery-electric mancars ws still in service when Huntley closed and the equipment was auctioned in the ealy 1990's. I would be surpised if Atlas, Jeffrey and other similar US firms did not make similar battery-electric mancars, but so far I have not been able to find any photos of them in use either.
I hope that this helps.