"why did artillery wheels have dished spokes?" Topic

The things you do learn. I am no Facebook type, but do like to see what Westfalia are up to and found this. The figures are brilliant, as I do like a good conversion. I was intrigued though by Summerfield's observation on why artillery wheel spokes radiated laterally (dished) rather than totally vertically. You may all have known this. I had often wondered!

link

It helped throw mud away from the gun and carriage.

Most load-bearing wagons had dished wheels – some even two sets of spokes dished in opposite directions.

link

For strength, especially when turning.
link

- Sasha

My understanding was that it allowed artillery to travel better over uneven ground, specifically across slopes. When the gun carriage tilted sideways going across a slope, more of the load was placed on the lower wheel. Straight spoked wheels could break, spokes pulling out of the wheel, while the dished spokes would be pushing into the wheel.

Without doing any research, my 'off the top of my head' idea would be that it gives the gun a wider wheel-base, and therefore stability – you could do the same thing with a wider axel but it would be a weaker axel.

David F Brown

I'm an engineer and here is my take on why the wheels were "dished". By "dished" I mean that the hub of the wheel was closer to the centerline of the carriage than the rims.

(((Some references say that the axle (the rotating shaft that goes cross wise left-to-right and upon which the center hub of the wheel rotates was "also inclined downwards so that the hub was directly above the rim of the wheel touching the ground, while the top part of the wheel (up in the air) was more to the outside. Now just a minute here. The axle shaft is a one piece thing. It can not be higher under the center of the carriage and lower at out the wheel hub because the entire shaft is ONE piece and connects to both the left and the right wheel. It is not an "independent suspension" situation like modern cars and race cars!!))))

A very simple reason for the dishing is due to the shock absorbing nature of the wheel spokes. If the hub was directly above the wheel rim, any shock from the wheel bouncing into a hard pothole would be down the grain of the wood. It would give the wagon a serious jolt, since the shock would be directly transferred to axle and then the carriage. The stress on the spoke would be taken straight down the grain of the wood, so it would either take it, or shatter. If the spoke was at an angle (not vertical) to the ground, this force would tend to be partly across (not down) the grain of the wood. Notice that tree branches sway in the wind quite well. Bend but not break. This springy action would soften the shock while the spoke bent a little and spread the forces out into a bending of the spoke and later release of the energy by a bit of bouncing. It is sort of a built in shock absorber feature.

And, yes, it also does add some stability if the carriage tilts sideways, since the hub then is directly above the rim and the stress where the spoke sticks into the rim is towards the center of the axle rather than a sidewise snapping direction.

Damn painted so many of these wheels and never thought about why they were that shape. Great source of knowledge this forum, cheers!

I did not know that. You learn something new and interesting every day.

Exactly my reaction. It is just something I took for granted in mouldings and I never even considered there might be several really good reasons for the shape.

Funny thing. Napoleonic Wars were (pretty much) pre industrial revolution. Not a lot of steam powered machinery about and no locomotion. I've tended to think of them as horse and musket, sword and lance.

But, when you look at the design features that went into a gun carriage, into the limber, into the ammunition, let alone into a ship of the line…….there were some skilled engineers around who could work with limited contemporary facilities!

I would stress it was Summerfield who got me thinking on this………….

Gents,
besides mud and cargo weight is an ohter problem? greetings serge joe

It's mostly a wheel strength thing, serge joe.

Get a team of horses pulling a cart on a rough ground and things are going to bounce all over the place, so you want the strongest wheels you can make.

If you have a metal axle, it might be slightly arched unloaded so that when you put a gun barrel on there it's straight. That's stronger than a straight unloaded axle, and it makes it less likely for the wheels to be pushed off the ends of the axle.

The first guy put them on crooked and everybody else just did what he did.

(((Some references say that the axle (the rotating shaft that goes cross wise left-to-right and upon which the center hub of the wheel rotates was "also inclined downwards so that the hub was directly above the rim of the wheel touching the ground, while the top part of the wheel (up in the air) was more to the outside. Now just a minute here. The axle shaft is a one piece thing. It can not be higher under the center of the carriage and lower at out the wheel hub because the entire shaft is ONE piece and connects to both the left and the right wheel. It is not an "independent suspension" situation like modern cars and race cars!!))))

What do the multiple parentheses mean?
An axle can be bent as it need not rotate, the wheels can rotate around the axle stubs.

Druzhina
Illustrations of Costume & Soldiers

FWIW, the idea of dished wheels were already about 300 years old by the time of Napoleon.

Dear All
It is interesting that artillery wheels were universal in design.

There are many reasons for dishing the wheels
1. Compression makes the joints tighter and strengthens them.
2. It makes the track narrower.
3. The slight angle on the axle keeps the wheels in place without the need of fixing them.
4. It puts the axle into compression rather than strain.
5. Reducing wear etc…
6. The Hub is not sticking out to catch upon walls etc..
7. Roads had restricted widths.

All these have been discussed above and in contempory texts are mentioned.
Stephen

Druzhina

Yes, looking at some more references, the "shaft" may not have been a straight piece of wood or metal (as I was assuming) but would more massive and be carved/built to bend downward from the centerline to the edges. That would allow the upper part of the wheel to be vertical, while the part in contact with the ground would be splayed outwards.

link

It gets more interesting all the time. I understood "dished" to mean that the spokes radiated from the hub, resulting in a 3D wheel rather than a flat thing, with the rim more laterally than the hub. But then comes a separate issue, that the wheel was not in a true vertical orientation anyway. This "dished" wheel was angled so the upper part was more lateral than the lower, in contact with the ground. Now that is rarely shown in modelling, but somehow it does seem right.

There is something about artillery. It just has to be "right", whereas anything goes for infantry and cavalry units in modelling. The rammer, the loader, the firer, the ventsman, the NCO, etc…you simply have to get them in the right place. Now I realise that applies to the wheels.

OK, let me risk one more question. Ignoring what actually looks right at any scale……..just how off vertical were artillery wheels on guns? (accepting that Portuguese in summer may be different from Guard Cossacks in 1812)

Back in 2014, Deadhead wrote:

"OK, let me risk one more question. Ignoring what actually looks right at any scale……..just how off vertical were artillery wheels on guns? (accepting that Portuguese in summer may be different from Guard Cossacks in 1812)"

. . . and the conversation died. Does anyone actually have this information? Should the wheels be splayed slightly so the "wheelbase" at the top is narrower than at the bottom? If so, would it be enough to notice in the scales we use?

/o\ or |o|?

Cheers,
John (about to put some 18mm artillery together . . .)

AIUI the spokes should be vertical beneath the hun and outward-leaning above.

Interesting. And this photo proves that you are right. Thanks very much.

could blast with the wagon wheels hold gun blast and not getting destroyed? link 1?

gun carriages and steel no
bal bearings
no
suspension just grease

The French Gribeauval artillery system introduced brass wheel housings in the naves to reduce friction and greatly aid in mobility.

I guess many of our posters have not spent any time axing and chain sawing trees down for firewood. Or putting in fence posts. IF you do that, the shape is a no-brainer- why would you do something that doesn't make sense? … .. Note that there was a similar "discovery" in the use of "cast iron' for building structures in the early 1800's. Cast iron is great when under compression ( pushing both ends towards each other ) . IT is poor in taking on lateral stressess- weight coming perpendicular to the long lenght of a beam. ( link ) . Pretty much the same thing with wooden wagon spokes.

@ 1968billsfan

That would explain only why the spokes are always vertical when directly under the hub. But a flat wheel would achieve the same. The bit that's less obvious is why the wheels need to be dished at all.

What is clear is that the wheel rims are not vertical when seen fore and aft.

Perhaps the following will help:

From the American Artillerist's Companion by Louis de Tousard, Volume II, 295-296:

'The strength of artillery wheels should be in a compound ratio of the weight which they are to be loaded with, and of the quality of the roads which it is presumable they are to travel on. Besides these two considerations which are to be observed generally in all artillery wheels, attention should be paid to the shocking which those of gun carriages experience in the firings.'

'We have already mentioned…the reasons which have determined the height of artillery wheels; we will remark, that, in the workmanship of the wheels, the dishing* or bevil requires much attention; the dishing, which is the setting off the spokes and fellies outwards, is regulated by the height of the wheel; it serves to give a setting off to the sides of the carriage, renders it less liable to overset, throws the mud outwards, and contributes to give more solidity to the wheel, which, in all the obliquities of the road, presents its spokes in a perpendicular direction, consequently, acts with the most powerful effect.'

*'The dishing of the wheels is the inclination of the spokes on the nave, or the distance of the front part of the mortise to a rule which is applied upon the fellies. For the form of the wheels, some make them more dishing, as they call it, than others; that is, more concave, by setting off the spokes and fellies more outwards.'

If anyone wants the definitions of the parts of the wheels, please let me know and I will supply them.