Back in the olden days, most lorries had top mounted wipers.
In more recent times, most, if not all are bottom mounted. Why the change ?
A lot of the wagons built up to the late 1950’s had “air conditioning” - meaning an opening windscreen. When they had a central pillar, this would sometimes be just the top half of the driver’s side screen, sometimes both sides, or the whole screen would crank out - but always hinged at the top. Mounting the wipers anywhere but at the top would just not work, if they were fitted at all. Look at photos of wagons from the 20s, 30s and 40s, it’s surprising how many had no wipers, and just one mirror in many cases.
If you’ve ever driven a lorry with top mounted wipers in the rain - you’ll know why!
The wiper comes up the screen and you have a few moments of clarity. The wiper goes down the screen - and all the water it has just pulled up follows it down, in streaks, right in front of your eyes…
And, repeat.
Frustrating? Oh yes! I wanted to drag whoever designed top mounted wipers and tie them to the seat and make them watch for a full day! Perhaps somebody did and that’s why they changed.
John.
John West:
If you’ve ever driven a lorry with top mounted wipers in the rain - you’ll know why!The wiper comes up the screen and you have a few moments of clarity. The wiper goes down the screen - and all the water it has just pulled up follows it down, in streaks, right in front of your eyes…
And, repeat.
Frustrating? Oh yes! I wanted to drag whoever designed top mounted wipers and tie them to the seat and make them watch for a full day! Perhaps somebody did and that’s why they changed.
John.
The other disadvantage of top-mounted wipers was that taller drivers stared straight into the arc of untreated windscreen whilst the rest of the screen was being cleared outside their field of focused vision 
. I’m only a short-arse so I didn’t mind so much! R 
Never drove one with bottom mounted but didn’t need to try top mounted to know they were wrong, did motor designers ever drive?
The ultimate was, of course, the Foden top mounted n air operated, you had to experience them to fully appreciate the awfulness of them. If they’d have fitted them on that Wermacht Foden the two lads would have blown it up. Cheers Coomsey
Bottom mounted also means less wiring snaking around to power them. Less wire to supply (and pay for) in the loom and quicker to install I imagine. So both manufacturers , buyers and drivers got what they wanted…
You have to look back at vehicles with top mounted wipers to see why they were there, the wiper blades were so small fitted at the bottom they would only have came half way up the screen, totally useless as they wouldn’t have cleaned the area the driver needed to see out. Why not fit longer blades, the motors back then would have had difficulty managing longer heavier blades and they would have been 12v, car wipers were just as puny and also not very effective. A change to 24v and cab design enabled the wipers to be bottom fitted with longer blades, not that it meant access to the wiper linkage and motors was any better but they were hidden. Interesting that the Seddon Motor Panels cabs had bottom wipers then later models changed to the top! Franky.
Greetings,All.
The LAD cabbed Comet : a prime example.900x20. 
The only motor I drove that had top mounted wipers was a Leyland FG during my tyre fitting days. The wipers swept towards each other, which made it nigh on impossible to see out of the screen driving in heavy snow as it all built up in the middle.
Also, can remember going in the old mans Thames trader as a kid and the wipers went faster on tick over, than when he was flat out
(45 mph) 
Suedehead:
The only motor I drove that had top mounted wipers was a Leyland FG during my tyre fitting days. The wipers swept towards each other, which made it nigh on impossible to see out of the screen driving in heavy snow as it all built up in the middle.
Also, can remember going in the old mans Thames trader as a kid and the wipers went faster on tick over, than when he was flat out
(45 mph)
Yes, my FG had 'em top-mounted too. I also had a BMC LDM van with them. Also the three Leyland Titan double-deckers I drove had 'em. And a Volvo F88 with crap ones that were vacuum or air operated like a Ford Prefect and went slower the faster you travelled. R
As already said some were air operated, and were…creaky to say the least. Given they were used on split screen designed cabs (glass technology has advanced of course) their sweep and length were limited. But, again already said, trying to defy gravity by pushing water uphill, ain`t gonna end well…
A single broad screen allows for longer sweeps and longer blades with overlapping swept areas.
Didn’t all Ergos have top mounted wipers?
ramone:
Didn’t all Ergos have top mounted wipers?
The ones I drove were R, they’d have been big old beasts if they’d have been top mounted!
Wasting time till the joy of going with the missis to Dunelms
There’s more bottom mounted than I thought, one I had n can’t remember Bathgate reiver,crusader,k dodge,tk n ford d
coomsey:
ramone:
Didn’t all Ergos have top mounted wipers?The ones I drove were R, they’d have been big old beasts if they’d have been top mounted!
Yes they were top mounted on all Ergomatic cabs, originally air operated, then later models had electrically operated wipers. the passenger side wiper was shorter than the driver’s side wiper.
Franglais:
As already said some were air operated, and were…creaky to say the least. Given they were used on split screen designed cabs (glass technology has advanced of course) their sweep and length were limited. But, again already said, trying to defy gravity by pushing water uphill, ain`t gonna end well…
A single broad screen allows for longer sweeps and longer blades with overlapping swept areas.
Whether bottom mounted or top mounted there is still an upward and downwards sweep by the wiper blade in each arc…just think about it. And more so on a car windscreen with a steeper rake than a lorry windscreen, the air flow over the bonnet pushes the water up the windscreen.
gingerfold:
Franglais:
As already said some were air operated, and were…creaky to say the least. Given they were used on split screen designed cabs (glass technology has advanced of course) their sweep and length were limited. But, again already said, trying to defy gravity by pushing water uphill, ain`t gonna end well…
A single broad screen allows for longer sweeps and longer blades with overlapping swept areas.Whether bottom mounted or top mounted there is still an upward and downwards sweep by the wiper blade in each arc…just think about it. And more so on a car windscreen with a steeper rake than a lorry windscreen, the air flow over the bonnet pushes the water up the windscreen.
When the blade stops to change direction at the end of it’s sweep, the water is either left at the bottom of a vertical truck screen, or is left at the top to follow the blade down…
See? I have thought about it.
Sent from my SM-G930F using Tapatalk
Franglais:
gingerfold:
Franglais:
As already said some were air operated, and were…creaky to say the least. Given they were used on split screen designed cabs (glass technology has advanced of course) their sweep and length were limited. But, again already said, trying to defy gravity by pushing water uphill, ain`t gonna end well…
A single broad screen allows for longer sweeps and longer blades with overlapping swept areas.Whether bottom mounted or top mounted there is still an upward and downwards sweep by the wiper blade in each arc…just think about it. And more so on a car windscreen with a steeper rake than a lorry windscreen, the air flow over the bonnet pushes the water up the windscreen.
When the blade stops to change direction at the end of it’s sweep, the water is either left at the bottom of a vertical truck screen, or is left at the top to follow the blade down…
See? I have thought about it.Sent from my SM-G930F using Tapatalk
The motion of a wiper blade is the same whether top or bottom mounted, its carving an arc in an incomplete circle…as Mr Spock would say (or was it Scottie) “you cannot change the laws of physics Jim” 
Cue the entry of Carryfast
Going off wipers a bit .Anybody remember the electric stick on demisters ?
This one isn’t sure what it prefers! from the Brewery Lorries thread.
