Glossary entry (derived from question below)
French term or phrase:
roue de ventre
English translation:
undershot mill wheel
Added to glossary by
Sheila Hardie
Apr 21, 2005 13:42
19 yrs ago
1 viewer *
French term
Spain
passion des mots
Native in: English 
Works in: Catalan to English, French to English, Spanish to English, and 2 more.
roue de ventre
French to English
Other
Archaeology
mill wheel
Les fondements actuels du Grand Moulin pourraient remonter au 16e siècle. D'allure monumentale, ses élévations datent, pour l'essentiel, du 19e siècle. Parmi ses équipements, ***une roue de ventre*** de 7,5 m de diamètre. Les fondements actuels du Petit Moulin ont été posés vers 1770. Propriétés de la commune depuis 1973 et classés depuis 1980, les bâtiments abritent actuellement l'ancienne meunerie du Petit Moulin (restauré), un musée d'histoire locale, le syndicat d'initiative et une taverne.
Any ideas? All I can think of is mill wheel. Maybe it is a specific type of mill wheel, but I'm not sure which.
Many thanks in advance,
Sheila
Any ideas? All I can think of is mill wheel. Maybe it is a specific type of mill wheel, but I'm not sure which.
Many thanks in advance,
Sheila
Proposed translations
(English)
| 3 +2 | undershot mill wheel |
Christopher Crockett
|
| 5 | water wheel |
Graham macLachlan
|
| 1 +3 | millwheel types |
Bourth (X)
|
| 4 | LATE POST-GRADING COMMENT |
Tony M
|
| 3 | waterwheel or pitwheel |
cchat
|
| 3 | spurwheel |
Dr Sue Levy (X)
|
Proposed translations
+2
7 mins
Christopher Crockett
Native in English
Specializes in field
M.A., Ph.D. Historian/Art Historian
Native in: English 
Works in: French to English, English
Related KudoZ points
:
131
Selected
undershot mill wheel
There are two types of mill wheels: "overshot" and "undershot", depending upon whether the water falls onto the wheel or flows below it.
I'm guessing that "ventre" would designate an undershot; but I need to do some more searching to be sure.
Undershot wheels are, of course, much more common.
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Note added at 29 mins (2005-04-21 14:11:16 GMT)
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Well, it\'s either one or the other.
A wheel 7.5 meters in diameter strikes me as a *very* large one, and, typically, overshot wheels are quite large, since they need the extra leverage to make up for the fact that they have relatively less water turning them.
There is an early 19th century overshot mill --now part of a state park-- not far from me, here in Southern Indiana.
The water comes from a spring (hence the name \"Spring Mill State Park\") up in a hillside and is brought to the mill in the bottom of a little valley by an elevated wooden \"millrace\"
http://www.southernin.com/Media/may_01/Spring_trough.jpg
You can just see the millrace to the right of the large mill building itself here :
http://www.cyberindiana.com/outdoors/img/springml.jpg
At the end of the millrace the water falls on the huge overshot wheel, barely visible here in the shadows (the millrace is comming in from the upper left) :
http://p.vtourist.com/1168464-Spring_Mill_grist_mill-Spring_...
Better shots, but farther away:
http://teelcountry.com/springmill.htm
Clearly, the amount of water which is comming from that spring is quite small compared to what one would have use of in a mill built on a stream or even a pond (with a millrace running underneath the wheel), but, because of the *size* of the wheel there is plenty of power to turn not just the grain mill (which is inside the large stone building), but also a \"gang saw\" in the smaller building nearby. The \"gang saw\" has three or four straight, vertical blades set in a \"frame\" and cuts several logs simultaneously.
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Note added at 32 mins (2005-04-21 14:14:48 GMT)
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Bourth\'s agreement to the contrary notwithstanding, I\'m now tending towards an overshot wheel --just because of the size of the thing. (In any event, it\'s clearly a question of the main wheel of the mill, not one of the several smaller ones, I should think.)
Is there any information elsewhere in your text which suggests what the *source* of the water is --stream, pond, spring?
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Note added at 51 mins (2005-04-21 14:33:58 GMT)
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Going back to the curious use of \"ventre\" (say, it\'s not \"vente\", is it??), there *may* be some sort of cultural thingie going on here.
In Anglo-Saxon sensibility the top of a wheel would be its \"back\" while the bottom would be its \"underbelly\".
But maybe the French are thinking in terms of the wheel \"catching\" the water in its \"ventre\" --\"les godets\", in Bourth\'s source-- in which case we\'re dealing with an overshot wheel. Undershot wheels just have flat paddles, while overshot ones have large \"buckets\" to catch and hold the water untill the wheel turns far enough for the water to spill out.
Very efficient devices, are overshot wheels. The one at Spring Mill S.P. was built by Germans, I believe. Wonder what the German phrase is.
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Note added at 52 mins (2005-04-21 14:35:08 GMT)
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What the hell is a \"breast wheel\" ?
Sounds like something Homer would like: \"Mmmmm... breast wheel...\"
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Note added at 1 hr 1 min (2005-04-21 14:44:13 GMT)
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Well, your added note settles the question, I should think.
Clearly a water mill (or two), with a \"solide barrage médiéval\" channeling the water to increase its power.
An undersot wheel is called for here, without doubt.
A water mill is also suggested by the reference to earlier foundations on which the present mill is (re-)constructed --windmills have relatively scant foundations compared to water mills, where the foundations are more important (and difficult/expensive to build) than the building built on them.
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Note added at 1 hr 8 mins (2005-04-21 14:51:01 GMT)
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Arrggg...
O.k, \"breastwheel\".
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Note added at 2 hrs 2 mins (2005-04-21 15:44:55 GMT)
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I hate it when that happens.
Note to Sue:
Yes, it\'s not these wheels http://www.pixelsbw.com/balades/arenberg/images/roues.gif
which are... I don\'t know, \"driving wheels\" which take belts and transfer the power from the shaft to somewhere else (a machine, maybe). They are quite small, obviously.
It\'s a question of the great water wheel on the exterior of the building which conveys the power of the water to these smaller wheels via the shaft which is its axle.
I'm guessing that "ventre" would designate an undershot; but I need to do some more searching to be sure.
Undershot wheels are, of course, much more common.
--------------------------------------------------
Note added at 29 mins (2005-04-21 14:11:16 GMT)
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Well, it\'s either one or the other.
A wheel 7.5 meters in diameter strikes me as a *very* large one, and, typically, overshot wheels are quite large, since they need the extra leverage to make up for the fact that they have relatively less water turning them.
There is an early 19th century overshot mill --now part of a state park-- not far from me, here in Southern Indiana.
The water comes from a spring (hence the name \"Spring Mill State Park\") up in a hillside and is brought to the mill in the bottom of a little valley by an elevated wooden \"millrace\"
http://www.southernin.com/Media/may_01/Spring_trough.jpg
You can just see the millrace to the right of the large mill building itself here :
http://www.cyberindiana.com/outdoors/img/springml.jpg
At the end of the millrace the water falls on the huge overshot wheel, barely visible here in the shadows (the millrace is comming in from the upper left) :
http://p.vtourist.com/1168464-Spring_Mill_grist_mill-Spring_...
Better shots, but farther away:
http://teelcountry.com/springmill.htm
Clearly, the amount of water which is comming from that spring is quite small compared to what one would have use of in a mill built on a stream or even a pond (with a millrace running underneath the wheel), but, because of the *size* of the wheel there is plenty of power to turn not just the grain mill (which is inside the large stone building), but also a \"gang saw\" in the smaller building nearby. The \"gang saw\" has three or four straight, vertical blades set in a \"frame\" and cuts several logs simultaneously.
--------------------------------------------------
Note added at 32 mins (2005-04-21 14:14:48 GMT)
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Bourth\'s agreement to the contrary notwithstanding, I\'m now tending towards an overshot wheel --just because of the size of the thing. (In any event, it\'s clearly a question of the main wheel of the mill, not one of the several smaller ones, I should think.)
Is there any information elsewhere in your text which suggests what the *source* of the water is --stream, pond, spring?
--------------------------------------------------
Note added at 51 mins (2005-04-21 14:33:58 GMT)
--------------------------------------------------
Going back to the curious use of \"ventre\" (say, it\'s not \"vente\", is it??), there *may* be some sort of cultural thingie going on here.
In Anglo-Saxon sensibility the top of a wheel would be its \"back\" while the bottom would be its \"underbelly\".
But maybe the French are thinking in terms of the wheel \"catching\" the water in its \"ventre\" --\"les godets\", in Bourth\'s source-- in which case we\'re dealing with an overshot wheel. Undershot wheels just have flat paddles, while overshot ones have large \"buckets\" to catch and hold the water untill the wheel turns far enough for the water to spill out.
Very efficient devices, are overshot wheels. The one at Spring Mill S.P. was built by Germans, I believe. Wonder what the German phrase is.
--------------------------------------------------
Note added at 52 mins (2005-04-21 14:35:08 GMT)
--------------------------------------------------
What the hell is a \"breast wheel\" ?
Sounds like something Homer would like: \"Mmmmm... breast wheel...\"
--------------------------------------------------
Note added at 1 hr 1 min (2005-04-21 14:44:13 GMT)
--------------------------------------------------
Well, your added note settles the question, I should think.
Clearly a water mill (or two), with a \"solide barrage médiéval\" channeling the water to increase its power.
An undersot wheel is called for here, without doubt.
A water mill is also suggested by the reference to earlier foundations on which the present mill is (re-)constructed --windmills have relatively scant foundations compared to water mills, where the foundations are more important (and difficult/expensive to build) than the building built on them.
--------------------------------------------------
Note added at 1 hr 8 mins (2005-04-21 14:51:01 GMT)
--------------------------------------------------
Arrggg...
O.k, \"breastwheel\".
--------------------------------------------------
Note added at 2 hrs 2 mins (2005-04-21 15:44:55 GMT)
--------------------------------------------------
I hate it when that happens.
Note to Sue:
Yes, it\'s not these wheels http://www.pixelsbw.com/balades/arenberg/images/roues.gif
which are... I don\'t know, \"driving wheels\" which take belts and transfer the power from the shaft to somewhere else (a machine, maybe). They are quite small, obviously.
It\'s a question of the great water wheel on the exterior of the building which conveys the power of the water to these smaller wheels via the shaft which is its axle.
Peer comment(s):
| agree |
Bourth (X)
: Four types (at least) actually, but if it has to be one of them, it would have to be the undershot I should think.
11 mins
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|
Two, four, whatever. Undershot definitely the most common (my Spring Mill was a very unusual situation). It's just that it is so damned large, makes me doubt my first thought.
|
|
| agree |
Tony M
: As Bourth says, at least 3 or 4 'standard' types, but only undershot or breast seems appropriate to me here.
114 days
|
|
Maybe so. Thanks, Dusty.
|
4 KudoZ points awarded for this answer.
Comment: "Thanks you all so much for your help - I wish I could divide the points up between you! To be honest, I had never heard of 'undershot wheels' before, but it does sound very likely that that is what they meant. Thank you again!
Sheila"
16 mins
waterwheel or pitwheel
You should be able to find what you need here.
Depending on the type of mill (wind or water) it could be a waterwheel, or a pitwheel, or something else again.
Hope this helps.
Depending on the type of mill (wind or water) it could be a waterwheel, or a pitwheel, or something else again.
Hope this helps.
Reference:
22 mins
spurwheel
I don't know whether your mills are watermills or windmills.
The spurwheel is the wheel on the vertical shaft in the middle of the mill. Nice diagram here: http://www.southernlife.org.uk/bursledonmill_schematic.htm
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Note added at 33 mins (2005-04-21 14:16:11 GMT)
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I took \"roue de ventre\" to mean in the middle of the mill.
The spurwheel is the wheel on the vertical shaft in the middle of the mill. Nice diagram here: http://www.southernlife.org.uk/bursledonmill_schematic.htm
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Note added at 33 mins (2005-04-21 14:16:11 GMT)
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I took \"roue de ventre\" to mean in the middle of the mill.
Peer comment(s):
| neutral |
Christopher Crockett
: We're in the dark here, but I'm definitely thinking of a water mill. In any event, the spurwheel in your windmill there looks to be a lot less than 30 feet in diameter.
20 mins
|
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yes you're right CC - in fact we're dealing with the exterior wheel here! http://www.pixelsbw.com/balades/arenberg/page1.htm
|
+3
21 mins
millwheel types
C'est la roue qui permet de transformer l'énergie de l'eau en mouvement. Il existe quatre types de roues en fonction du terrain et de l'utilisation.
La roue en-dessous
Cette roue est composée de palettes et ne tourne que par la poussée du courant. Elle peut parfois être réglée en hauteur pour s'adapter au niveau de l'eau.
La roue de coté
L'eau agit par son poids sur des palettes ou sur des augets. Elle nécessite un grand débit.
La roue en-dessus
Cette roue est composée de bacs. Cette fois, c'est l'eau, arrivant par le dessus et tombant dans les godets, qui fait tourner la roue.
La roue horizontale
L'axe vertical est entrainé par le choc de l'eau sur des palettes, à la façon d'une turbine ; la meule est entrainée directement. Elle convient très bien aux régions accidentées
[forgot to copy the address]
If it has to be one of these, I'd go for the "en-dessous" (undershot), like CC.
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Note added at 25 mins (2005-04-21 14:07:40 GMT)
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Another hypothesis of course is that the roue here is not the wheel that harnesses teh water power, but the millstone that grinds the grain. These can be of different shapes. One I have seen (though on a much smaller scale) is domed quite pronouncedly (grinding stones generally have a Scandinavian accent in my experience), a shape that could be likened to a rotund/pregnant belly ... This means that the ground material falls quickly from the stone ...
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Note added at 26 mins (2005-04-21 14:08:27 GMT)
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Such a stone would be mighty weighty at 7.5 m dia. so I actually think not ...
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Note added at 46 mins (2005-04-21 14:28:49 GMT)
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Unless it\'s a typo for \"roue de vent\" which I cannot substantiate in French but which has a convenient English equivalant in \"wind wheel\" :
• AGRICCO WINDMILL # This windmill was built in the 1920\'s. It used a paddle type WIND WHEEL instead of a conventional tail for orientation and a similar but larger arrangement for the main drive. The wheel was tilted back over the head about 20 degrees to the vertical. The main blades were able to feather for WIND WHEEL speed control. They were rotary drive power mills which could be adapted for pumping, generation or machinery operation. Water screws were offered for pumping purposes.
...
• BJ360 WINDMILL # 3.6 metre WIND WHEEL direct action windmill. 8 paddle blades, single spar tail and side vane.
• LJ3600 WINDMILL Wind generator with pumping package. 3.6 metre WIND WHEEL with eight blades.
[http://members.westnet.com.au/caladenia/european_windmill_ma...]
The European windmills were of the post type, being a vertical post around which the entire mill rotated, and the turret type with the WIND WHEEL and ...
www.albemarle-nc.com/camden/history/mills.htm
Few people, however, are aware of Angmering’s fourth mill, an unusual type driven by a WIND-WHEEL in place of conventional sweeps. ...
www.findonvillage.com/0807_preston_place_mill.htm
Later the Crusaders would turn to the idea of the wind mill for building mills in France and England. They took the idea of the Roman vertical water wheel and applied it to create the WIND WHEEL that would power the millstones below by gears. [http://www.angelfire.com/journal/millbuilder/historical.html]
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Note added at 54 mins (2005-04-21 14:36:59 GMT)
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Then again, MAYBE SARAH HAS IT with a type for \"roue de Centre\", though this does not appear to be standard terminology either:
Focus Word: breastwheel
1. a water wheel, on which the stream of water strikes neither so high as in the overshot wheel, nor so low as in the undershot, but generally at about half the height of the wheel, being kept in contact with it by the breasting. the water acts on the float boards partly by impulse, partly by its weight.
[http://www.thesaurus-dictionary.com/files/b/r/e/breastwheel....]
Picture at:
http://www.nps.gov/lowe/2002/loweweb/lowe_history/lowe_handb...
and at:
http://www.geocities.com/Heartland/Hills/6365/pic4.html
At the Gilbert Stuart Birthplace, an UNDERSHOT wheel powers the snuff mill and a BREASTWHEEL powers the gristmill. Each wheel is connected to the river ...
www.geocities.com/Heartland/Hills/6365/stuartwater.html
--------------------------------------------------
Note added at 55 mins (2005-04-21 14:37:58 GMT)
--------------------------------------------------
Man for man, Word for word, Typo for typo
La roue en-dessous
Cette roue est composée de palettes et ne tourne que par la poussée du courant. Elle peut parfois être réglée en hauteur pour s'adapter au niveau de l'eau.
La roue de coté
L'eau agit par son poids sur des palettes ou sur des augets. Elle nécessite un grand débit.
La roue en-dessus
Cette roue est composée de bacs. Cette fois, c'est l'eau, arrivant par le dessus et tombant dans les godets, qui fait tourner la roue.
La roue horizontale
L'axe vertical est entrainé par le choc de l'eau sur des palettes, à la façon d'une turbine ; la meule est entrainée directement. Elle convient très bien aux régions accidentées
[forgot to copy the address]
If it has to be one of these, I'd go for the "en-dessous" (undershot), like CC.
--------------------------------------------------
Note added at 25 mins (2005-04-21 14:07:40 GMT)
--------------------------------------------------
Another hypothesis of course is that the roue here is not the wheel that harnesses teh water power, but the millstone that grinds the grain. These can be of different shapes. One I have seen (though on a much smaller scale) is domed quite pronouncedly (grinding stones generally have a Scandinavian accent in my experience), a shape that could be likened to a rotund/pregnant belly ... This means that the ground material falls quickly from the stone ...
--------------------------------------------------
Note added at 26 mins (2005-04-21 14:08:27 GMT)
--------------------------------------------------
Such a stone would be mighty weighty at 7.5 m dia. so I actually think not ...
--------------------------------------------------
Note added at 46 mins (2005-04-21 14:28:49 GMT)
--------------------------------------------------
Unless it\'s a typo for \"roue de vent\" which I cannot substantiate in French but which has a convenient English equivalant in \"wind wheel\" :
• AGRICCO WINDMILL # This windmill was built in the 1920\'s. It used a paddle type WIND WHEEL instead of a conventional tail for orientation and a similar but larger arrangement for the main drive. The wheel was tilted back over the head about 20 degrees to the vertical. The main blades were able to feather for WIND WHEEL speed control. They were rotary drive power mills which could be adapted for pumping, generation or machinery operation. Water screws were offered for pumping purposes.
...
• BJ360 WINDMILL # 3.6 metre WIND WHEEL direct action windmill. 8 paddle blades, single spar tail and side vane.
• LJ3600 WINDMILL Wind generator with pumping package. 3.6 metre WIND WHEEL with eight blades.
[http://members.westnet.com.au/caladenia/european_windmill_ma...]
The European windmills were of the post type, being a vertical post around which the entire mill rotated, and the turret type with the WIND WHEEL and ...
www.albemarle-nc.com/camden/history/mills.htm
Few people, however, are aware of Angmering’s fourth mill, an unusual type driven by a WIND-WHEEL in place of conventional sweeps. ...
www.findonvillage.com/0807_preston_place_mill.htm
Later the Crusaders would turn to the idea of the wind mill for building mills in France and England. They took the idea of the Roman vertical water wheel and applied it to create the WIND WHEEL that would power the millstones below by gears. [http://www.angelfire.com/journal/millbuilder/historical.html]
--------------------------------------------------
Note added at 54 mins (2005-04-21 14:36:59 GMT)
--------------------------------------------------
Then again, MAYBE SARAH HAS IT with a type for \"roue de Centre\", though this does not appear to be standard terminology either:
Focus Word: breastwheel
1. a water wheel, on which the stream of water strikes neither so high as in the overshot wheel, nor so low as in the undershot, but generally at about half the height of the wheel, being kept in contact with it by the breasting. the water acts on the float boards partly by impulse, partly by its weight.
[http://www.thesaurus-dictionary.com/files/b/r/e/breastwheel....]
Picture at:
http://www.nps.gov/lowe/2002/loweweb/lowe_history/lowe_handb...
and at:
http://www.geocities.com/Heartland/Hills/6365/pic4.html
At the Gilbert Stuart Birthplace, an UNDERSHOT wheel powers the snuff mill and a BREASTWHEEL powers the gristmill. Each wheel is connected to the river ...
www.geocities.com/Heartland/Hills/6365/stuartwater.html
--------------------------------------------------
Note added at 55 mins (2005-04-21 14:37:58 GMT)
--------------------------------------------------
Man for man, Word for word, Typo for typo
Peer comment(s):
| agree |
Christopher Crockett
: 2, 4, whatever. Agree with your last that it really cannot be the grindstone. See my most recent musings wherein I vacillate towards an overshot wheel because of the extraordinary size. But, that's the only reason why I do, and could be wrong, yet again.
16 mins
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It's always nice to have something to get one's teeth into ...
|
|
| agree |
sarahl (X)
: yes unless it's a typo for centre.
19 mins
|
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Aha! So a breastwheel then (ventre, breast ... nothing personal ...)
|
|
| agree |
Tony M
: I'm inclined to go for beast wheel
114 days
|
4 hrs
water wheel
From the extract below it seems that the 'ventre' relates to the building rather than the piece of equipment, it is the 'roue' in/at the 'ventre of' the mill:
Dans le ventre du moulin, on retrouve toujours les équipements pour moudre la farine ; la grande roue à godets de 20 pieds de diamètre, trois moulanges, le bluteau et le crible semblent attendre le prochain meunier.
http://www.villesaintpascal.qc.ca/patrimo.html
Godets : n.m. Compartiments situés sur la circonférence d’une roue pour retenir l’eau. Le poids de l’eau accumulé dans un certain nombre de godets provoque la rotation de la roue.
N.B. Les godets servent aussi au transport de la mouture dans le cas de l’élévateur à godets.
Goulotte : n.f. Voir Anche.
Grande roue : n.f. Roue à godets servant de force motrice au moulin à eau.
http://charlevoix.qc.ca/moulins/a_lexique.htm
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Note added at 17 hrs 27 mins (2005-04-22 07:10:01 GMT)
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I thought the dimensions were similar, 20 pieds would be just under 7 m - whatever the detail, the main thrust is that the \'roue de ventre\' is likely to be a water driven wheel...
Dans le ventre du moulin, on retrouve toujours les équipements pour moudre la farine ; la grande roue à godets de 20 pieds de diamètre, trois moulanges, le bluteau et le crible semblent attendre le prochain meunier.
http://www.villesaintpascal.qc.ca/patrimo.html
Godets : n.m. Compartiments situés sur la circonférence d’une roue pour retenir l’eau. Le poids de l’eau accumulé dans un certain nombre de godets provoque la rotation de la roue.
N.B. Les godets servent aussi au transport de la mouture dans le cas de l’élévateur à godets.
Goulotte : n.f. Voir Anche.
Grande roue : n.f. Roue à godets servant de force motrice au moulin à eau.
http://charlevoix.qc.ca/moulins/a_lexique.htm
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Note added at 17 hrs 27 mins (2005-04-22 07:10:01 GMT)
--------------------------------------------------
I thought the dimensions were similar, 20 pieds would be just under 7 m - whatever the detail, the main thrust is that the \'roue de ventre\' is likely to be a water driven wheel...
Peer comment(s):
| neutral |
Bourth (X)
: Saw the St Pascal site too (there's also ONE other I found with "ventre du moulin"), but "ventre" COULD be many things. Maybe the "roue de ventre" was some sort of torture machine ;-) ......
2 hrs
|
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It seems to be doing a good job of torturing us! Cheers Bourth
|
114 days
LATE POST-GRADING COMMENT
I was disappointed to discover this question only after the event, as I own and live in a watermill!
I just wanted to make a couple of points that no-one else seems to have mentioned, though several have commented on questions of size.
An undershot wheel is often used on a flat, slow flowing river where there is little or no natural (or artificial) fall --- as very often seen on the Loire etc. In this case, the wheel is often large, to gain more leverage (turns quite slowly) --- it is relatively inefficient, as only a small part of the perimeter is actually being driven by the water at any one moment.
An overshot wheel can only be used where there is a fall of water (as is the case in Asker's context, which clearly mentions a 'mediaeval dam') --- BUT the diameter of the wheel is limited, as the water has to go over it, so the wheel cannot be larger in diameter than the height of the fall of water. My own is only a puny 2m, but one of our local mills, still working, uses a massive 5m fall!
The breast wheel, on the other hand, can have a diameter up to about twice the fall (or even more) --- so the 24ft wheel in the context above is entirely feasible --- as the water only joins the wheel half way round. These wheels are noted for being the most efficient, as the full power of the water is exploited, since it remains in contact with the wheel (and thus, doing useful work) for approx. 90° of its rotation, and is channelled round the wheel by the 'breast'. Also, the wheel can be quite large, enabling advantage to be taken of the greater leverage.
I hope these added comments throw some light on the matter for future enquirers!
I just wanted to make a couple of points that no-one else seems to have mentioned, though several have commented on questions of size.
An undershot wheel is often used on a flat, slow flowing river where there is little or no natural (or artificial) fall --- as very often seen on the Loire etc. In this case, the wheel is often large, to gain more leverage (turns quite slowly) --- it is relatively inefficient, as only a small part of the perimeter is actually being driven by the water at any one moment.
An overshot wheel can only be used where there is a fall of water (as is the case in Asker's context, which clearly mentions a 'mediaeval dam') --- BUT the diameter of the wheel is limited, as the water has to go over it, so the wheel cannot be larger in diameter than the height of the fall of water. My own is only a puny 2m, but one of our local mills, still working, uses a massive 5m fall!
The breast wheel, on the other hand, can have a diameter up to about twice the fall (or even more) --- so the 24ft wheel in the context above is entirely feasible --- as the water only joins the wheel half way round. These wheels are noted for being the most efficient, as the full power of the water is exploited, since it remains in contact with the wheel (and thus, doing useful work) for approx. 90° of its rotation, and is channelled round the wheel by the 'breast'. Also, the wheel can be quite large, enabling advantage to be taken of the greater leverage.
I hope these added comments throw some light on the matter for future enquirers!
Discussion
Probablement appuy�s sur un solide barrage m�di�val, en un point de reserrement de la plaine alluviale de la Senne, � hauteur du promontoire villageois, les moulins de Rebecq sont les t�moins privil�gi�s d'au moins cinq si�cles d'histoire. Se faisant face de part et d'autre du cours d'eau, le Petit Moulin (rive droite) et le Grand Moulin (rive gauche) disposent chacun d'une vantellerie ind�pendante appuy�e sur un �lot artificiel plac� au centre de la rivi�re. Les fondements actuels du Grand Moulin pourraient remonter au 16e si�cle. D'allure monumentale, ses �l�vations datent, pour l'essentiel, du 19e si�cle.
Thanks again!
Sheila