Oval chainring?

ColinJ

Puzzle game developer
I think they look a bit ugly, but I bet they would make riding singlespeed a little easier on climbs?

I ride a 52/19 gear which is ideal for me at 27-32 kph (17-20 mph) but it is hard to get the cranks through the deadspots when pedalling slowly up steepish hills.

It makes sense to me to effectively use a smaller ring where legs are struggling and a bigger one where they are generating the most power.
 
Well written review. Excellent grammar and some some nice fuzzy but vague terms like feels, sounds and smooths. Unfortunately, not a single ounce of evidence that the chain rings do anything except lighten your wallet in exchange for a nicely machined piece of placebo bling!
Where is the data, the increased power outputs, the reduced times, the gold medals?
 

Ajax Bay

Guru
Location
East Devon
"You can test the ‘smoothing out’ theory by riding a knobbly tyre on flat tarmac with a round chainring. If you lack souplesse, you’ll probably hear a rhythmic buzz as the torque changes through the 360 degrees of the pedal stroke. Fit an oval ring and this ‘bouncing’ should disappear."
Why would the torque change cycle which the drivetrain experiences with a circular chainring result in a change in rhythmic buzz? A oscillating frequency of tyre noise on a (NB) flat tarmac surface (so 10+mph) implies a change in speed every half crankset cycle sufficient to detect audibly. Seems unlikely to me.
Is she equating 'rhythmic buzz' with 'bouncing'? You get some 'bounce' (with a suspension fork particularly) during pedalling (lacking souplesse)) and I guess that might cause 'rhythmic buzzing' as the vertical load cycles through on a knobbly tyre.
"It’s arguably kinder on the knees as the gear is effectively lowered where the stroke is weakest."
and then without caveat in the 'Verdict': "Worth trying on hilly terrain to ease [sic] the knees,"
Is there science to support this argument/assertion?
https://www.bikefitadviser.com/blog/oval-chainrings
Rather less expensive option - to try them out:

View: https://www.amazon.co.uk/DECKAS-Chainring-Mounrtain-Ultralight-Chainwheel/dp/B0887SJ6YK
 
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fossyant

Ride It Like You Stole It!
Location
South Manchester
Where have Cycling Uk been for the last five or more years ? These aren't new on 1x MTB's. Personally I will stick with round, but they have been the 'fad' for many years.

There is a who load of 'rubbish' talked in MTB circles about them. It's another bit of bling ! Some folk like them. I can't see them helping much as there is way too much other stuff going on on a MTB, rocks, gravel, mud affecting traction, suspension movements and all sorts.
 

fossyant

Ride It Like You Stole It!
Location
South Manchester
An oval would be fine - it's symmetric, so same number of chain-links in contact all the time.
Other shapes could be problematic. A fun geometry project for lockdown??
It might be symmetric, but the 'taller' profile will pull the chain 'tighter' as the profile rotated to the front/back, where the mech will take up the slack, but not on single speed. Where the taller profile is 'top and bottom' the chain will be slacker. This won't work well without a chain tensioner.
 

matticus

Veteran
Where have Cycling Uk been for the last five or more years ? These aren't new on 1x MTB's. Personally I will stick with round, but they have been the 'fad' for many years.
Five OR MORE is a bit of an understatement.
 

matticus

Veteran
It might be symmetric, but the 'taller' profile will pull the chain 'tighter' as the profile rotated to the front/back, where the mech will take up the slack, but not on single speed. Where the taller profile is 'top and bottom' the chain will be slacker. This won't work well without a chain tensioner.
I see what you mean. Could be right! Don't know how big the effect will be ... can someone make a video? Are you busy Fossyant?
 

fossyant

Ride It Like You Stole It!
Location
South Manchester
Is she equating 'rhythmic buzz' with 'bouncing'? You get some 'bounce' (with a suspension fork particularly) during pedalling (lacking souplesse)) and I guess that might cause 'rhythmic buzzing' as the vertical load cycles through on a knobbly tyre.
It's rubbish. It won't stop the bounce - I can noticeably see the rear suspension compress on every down stroke (left or right) due to more pressure being applied to the cranks, in turn compressing the suspension. Thats when you get the increased buzz.
 

fossyant

Ride It Like You Stole It!
Location
South Manchester
I see what you mean. Could be right! Don't know how big the effect will be ... can someone make a video? Are you busy Fossyant?
I don't have oval rings nor a singlespeed now, but I certainly know if you don't fix a singlespeed chainring centrally on the spider, you'll get widely varying chain tension on a fixie (I owned on for 10 years). Even slightly out of centre, you could get some shift in tension. This will be huge on oval rings. Even manufacturing tolerances affect the chain tension enough.
 

Ajax Bay

Guru
Location
East Devon
An oval would be fine - it's symmetric, so same number of chain-links in contact all the time.
Other shapes could be problematic. A fun geometry project for lockdown??
It might be symmetric, but the 'taller' profile will pull the chain 'tighter' as the profile rotated to the front/back, where the mech will take up the slack, but not on single speed. Where the taller profile is 'top and bottom' the chain will be slacker.
I see what you mean. Could be right!
In the spirit of Matt's 'geometry project' I have done the maths.
There will be a chain length 'difference' on the tension section (hence @fossyant's "tighter") from sprocket to ring of about 0.8mm when the elliptical ring's long axis is vertical cf when the short axis is vertical. This is for a ring with a ~1:1.12 axis ratio with ~40t, using a ~18t sprocket and a chainstay length of ~420mm.
I'll leave it to you 'fixed/SS' chaps to say whether that difference will have a noticeable/deleterious effect.
 

byegad

Legendary Member
Location
NE England
These come around every few years .
In that time I've seen then set at different angles in relation to the cranks, and claims that they miraculous.
Next will be the hand and leg powered bike, the idea for which is over 100 years old.
 
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