Odd Number of Spokes

[WoodlandsCamper]

It appears that alloy wheels on cars and vans generally have an odd number of spokes. Why is this? Our car has 7 spokes and the van has 5.

Edit - Whooops, just looked at a photo of the van and it has 7 spokes as well. Oh, what a well matched outfit.

 

[VicMallows]

My 'van wheels have 10 spokes ... that's an even number (OK, they are arranged in 5 groups of 2).

More to the point, why are caravan wheels alloy at all? - can't be to improve acceleration surely? Even more to the point, wouldn't it make more sense if the spare wheel was alloy, since this weight comes directly out of the available payload. In fact of course the majority of spares are (cheaper and heavier) steel.

All down to aesthetics and marketing IMHO.

 

[Martin24]

Oh blast. I'm now going to have to go to the drive and start counting.

I know the new car will have 5 spokes. I would imagine it's entirely aesthetic reason the same as in gardening you would always plant in threes upwards in odd numbers unless planting a single specimen.

Back in, haven't counted the van as can't be bothered to open the gates. The Isuzu has 5 but then the Corsa has four groups of two. Whichever way I count I can only get evens out of that one. Still it is only a Corsa .

Now thinking to myself that I've reached a new level of sad to have gone outside at half ten to count :woohoo:

 

[colin-yorkshire]

I think it is to do with harmonics and aesthetics. playing a role in the design due to the concept of uneven being a sounder option. [gobbledegook one may say] but there is a sound engineering thinking behind it. for example. a 3 legged stool will always sit firmer than a 4 legged one if the ground is uneven. and wheelwrights found using odd numbers of spokes made the wheels stronger and simpler to make. car and trailer wheels are descendants of the cart so look better as that is what seems to be normal . also odd numbers prevent symmetry so the wheels don't look odd while it is parked as the lines on the wheels are never in unison.
thing is if you take notice it is not just wheels fan blades are always odd numbered as even numbers set up vibration as the fan slices through the air causing a buzz, due to imbalance..
and gears. those that inter mesh. at least one set has to have odd numbers of teeth this is to prevent excessive wear as no two teeth rub together constantly.
ball bearing always have odd numbers off balls or rollers for a similar reason.

so there is a lot of occasions where odd is better if you look. wheels are just one. well spotted that man.

 

[ProfJohnL]

Colin
Thats a hotch potch of ideas and some have no relation to the number of spokes in a wheel.

I think it is to do with harmonics and aesthetics. playing a role in the design due to the concept of uneven being a sounder option. [gobbledegook one may say] but there is a sound engineering thinking behind it. for example. a 3 legged stool will always sit firmer than a 4 legged one if the ground is uneven.

Perfectly true about stools, But harmonics???? Everything has at least one fundamental frequency at which it will vibrate, and it will most likely produce harmonics of that fundamental. I cannot conceive resonance frequencies and their harmonics of a balanced wheel having any significant amplitude or transmission back to the ears of occupants or pedestrians nearby.My strongest suspicion is all about wheel strength and aesthetics.

wheelwrights found using odd numbers of spokes made the wheels stronger and simpler to make.

Really? Odd number of spokes are stronger even? So 5 is stronger than 6?
No, It's a fact that more will share the loads better than less, but that has nothing to do with the numbers being even or odd.

It is easier to work with even numbers becasue without quite accurate machining or jigs, getting evenly spaced odd numbers of spokes on a wheel is a real skill, but even numbers area lot simpler.

fan blades are always odd numbered as even numbers set up vibration as the fan slices through the air causing a buzz, due to imbalance...

No they are not always odd numbered! I have several examples of fans and propellers with even numbers of blades. Every fan blade as it passes through its medium, (air or water) creates localised disturbances to the fluid, its those disturbances that are transmitted as a shock wave through the medium, and in the case of air, is what wee hear. The next blade will do the same. The repeat frequency of those shock waves is determined by the rotational speed of the fan shaft multiplied by the number of blades on the fan. Having an odd number does not magically reduce or stop those disturbances.

 

[Gafferbill]

That is a master class in how to post on a forum Prof

......you corrected the science without being derogatory.

 

[Dustydog]

Science :woohoo:
I thought it was all about sympathetic harmonic vibrations.
Whatever happened to solid wheels

 

[Gabsgrandad]

Just looking at mine out of the window, 6 pairs of two, thank god they are separating the hub from the rim and keeping the air in!

 

[ProfJohnL]

Science :woohoo:
I thought it was all about sympathetic harmonic vibrations.
Whatever happened to solid wheels

Doh! you mean the single spoked wheel - You've got me there Dusty 1 is an odd number and stronger than all the rest put together. Ill go to the corner and put on my dunces hat. - how long do I have to stay there?

 

[Dustydog]

Error with photobucket. Back later

 

[DrZhivago]

Error with photobucket. Back later

Well done, looks like you just blew someone's Photobucket limit :lol: Your own?

 

[Dustydog]

Photobucket wont let me post . something about updating my account! Will leave till later.

 

[WoodlandsCamper]

The photo I put on the Woosie thread yesterday about a break away cable is still there. I looked at my account on photobucket when linking the photo and I had used 10% of allowed memory.

 

[DrZhivago]

Photobucket wont let me post . something about updating my account! Will leave till later.

Perhaps you missed this thread ?
https://www.practicalcaravan.com/forum/our-website/54926-photobucket-costing-399-pa-now?limitstart=0

 

[Dustydog]

Thanks Dr Z
Rats.I missed that thread. That may explain it. I'll look closer later.
WC.
The picture I was trying to post was a new download from this morning . I assume my historic pics are okay?
Sods law says this old dog must be doing something good wrong
Prof.
No need for the D hat.I like the reference to the one spoke solid wheel
Solid.Reminds me of Swift

 

[ProfJohnL]

Oh thnak you your dogginess

 

[colin-yorkshire]

Colin
Thats a hotch potch of ideas and some have no relation to the number of spokes in a wheel........................................................................................................................................................................................................................................................................................................................................................................................

well that spanked my botty good job I'm a thick skinned long standing Woosie I could have got all offended like. :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:

so come on Prof why do wheels have odd numbers of spokes you must know.!!!

 

[Dustydog]

Even Sir Sproket's excellent script is corrupted
https://www.practicalcaravan.com/forum/our-website/51257-posting-pictures
What do you guys use instead please?

 

[Gabsgrandad]

Yet this one's not! Post a 'Teletubby' ! (A bit further on)

https://www.practicalcaravan.com/forum/our-website/51257-posting-pictures

 

[otherclive]

"We rarely notice, the number of most Car Tyre spoke is in the form of a few odd, even. This has a close relationship with the casting process of the wheel hub. Wheel spokes, start by casting or forging process as a whole. However, whether it is casting or forging is to go through an important cooling process.
Even spoke to two spokes are on the same horizontal line, casting unable to deform easily under the stress rupture. The spokes of the odd because two spokes is not in the same horizontal line, the internal stress can be relieved by the small deformation of the spokes, so if it is odd spoke, stress will dissipate uniform deformation may be small."

A translation from a foreign website. It seems that it may all to be related to the casting process, although some reckon that asymmetric wheels "park" better and are thus aesthetically more pleasing to the eye.

 

[Martin24]

I'm now wondering if we should have stuck to the one spoke with holes steel wheel instead of specifying alloys on the new car. All a bit of a dither now as to whether 5 spokes is a good number or not.

 

[ProfJohnL]

Colin
Thats a hotch potch of ideas and some have no relation to the number of spokes in a wheel........................................................................................................................................................................................................................................................................................................................................................................................

well that spanked my botty good job I'm a thick skinned long standing Woosie I could have got all offended like. :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:

so come on Prof why do wheels have odd numbers of spokes you must know.!!!

Because the designer chooses that number. :kiss:

 

[ProfJohnL]

"We rarely notice, the number of most Car Tyre spoke is in the form of a few odd, even. This has a close relationship with the casting process of the wheel hub. Wheel spokes, start by casting or forging process as a whole. However, whether it is casting or forging is to go through an important cooling process.
Even spoke to two spokes are on the same horizontal line, casting unable to deform easily under the stress rupture. The spokes of the odd because two spokes is not in the same horizontal line, the internal stress can be relieved by the small deformation of the spokes, so if it is odd spoke, stress will dissipate uniform deformation may be small."

A translation from a foreign website. It seems that it may all to be related to the casting process, although some reckon that asymmetric wheels "park" better and are thus aesthetically more pleasing to the eye.

Yes there may be manufacturing concern for cast wheels and casting stresses whilst cooling, but that does not dictate even or odd numbers for other methods of manufacture - especially hand made cart wheels which were cited as the prime example.

 

[ProfJohnL]

I'm now wondering if we should have stuck to the one spoke with holes steel wheel instead of specifying alloys on the new car. All a bit of a dither now as to whether 5 spokes is a good number or not.

Five is great number, so are many others. but if it means having to use the fingers of more than one hand you probably need a professorship theoretical mathematics to stand a chance :blink:

 

[Grahamh]

Reminds me of the question about windscreen wipers
Some go from left to right, some go from outside to inside, some cars just have one wiper that sweeps from left to right or right to left; some used to be at the top of the screen and sweep left to right etc etc
Now why is that?? Well it's because its raining!
I'll get me coat....