oval chainring

[trplay]

@Randyc3 Yes. You are spending a little less time in your pedal stroke in the power stroke, and a little more time in the dead spot. Better for your knees, perhaps, but it works a bit against your power.

I do not think so. It is a push through the entire high side of the ring. My biggest query is these (adjustable) rings are not adjustable. This is the only way I know how to fit them on the spider. The silver screw set on 4 is nothing more than a spacer to help the chain shift. As far as power goes I can change from these to round 50/54 to 53/39 to 53/36 power stays the same. Well documented with 1000's of miles.

 

[billyk]

As @castlerobber says above, every couple of years we beat this topic to pieces. There are several multipage threads going back more than a decade (some linked above by me).

The whole thing is complicated by the availability (or not) of the right holes to fit your spider, given that most e-rings are designed for uprights.

But isn't the basic premise that your strongest push is near the middle of your leg extension? That's going to be roughly 45° past where the chain engages. (Tolhurst said 40° in the instructions I can't find anymore).

I'd shoot for that, then adjust a little in each direction and ride for an hour to test and tune.

 

[trplay]

Yes, this issue is reborn every 10 years or so as a new generation of cyclists looks for the magic bullet. I first saw the non-round ring concept at college in a science display in 1974. I believe this idea goes back over 100 years. But to this day, even with the high variety of accurate technical measuring devices, there is yet a single convincing study showing these things work. Not one. Tim Krabbe nails it in his book "The Rider" where he writes about 5-time tour de France winner Jacques Anquetil. Apparently, Jacques would always take his water bottle out of the holder before every climb and place it in his jersey. When he was asked about this strange habit he said a racer was made of two parts, the rider and, the bike. Bike weight of course slows you down so removing the bottle from the bike reduces bike weight and makes it faster when the going gets tough. Got it? Krabbe went on to write, "what Jacques needed was faith. And nothing is better for a firm solid faith than being in the wrong." He also said, "if they'ed forbidden Antiquetil to put his bidon in his back pocket, he would have never have won the Tour de France." I believe These funny little rings fit in here somewhere.

 

[Randyc3]

As far as power goes I can change from these to round 50/54 to 53/39 to 53/36 power stays the same. Well documented with 1000's of miles.[/QUOTE]
Can I get a clarification? So your watts are the same when comparing elliptical to round?
I had been using ellipticals for years on my DF with good (perceived) resultS. So for me installing them on my S40 was natural. Have to admit, would be interesting to design a test setup to do a comprehensive evaluation.

 

[Beano]

In a nutshell:-

Through the dead spot you want the q ring to be at it's least oval state with respect to the chain line - oval chain ring 1.
Through the power stroke you want it to go through it's most oval state with respect to the chain line - oval chain ring 2.

See images below and the red line regarding how oval the chainring is through the power stroke and dead spot. If you use the front mech clearance as a reference.

 

[bladderhead]

This is so cool. Since the lube wars were won by wax we have needed something else about which to argue. And this is a three-way argument. Do you prefer the Biopace or conventional orientation? Or is the whole thing daft? How long can we keep this up?

Anyway, everybody prefers a different setup. You have to keep changing it until you get it right.

Well, what did you expect from a Cruzbike?

 

[Gary123]

Could we bring back the powercam.

 

[Beano]

This is so cool. Since the lube wars were won by wax we have needed something else about which to argue. And this is a three-way argument. Do you prefer the Biopace or conventional orientation? Or is the whole thing daft? How long can we keep this up?

Anyway, everybody prefers a different setup. You have to keep changing it until you get it right.

Well, what did you expect from a Cruzbike?

Whatever floats your boat.

Having used both round and oval rings on a trainer in ERG mode at the same power, I found my pedal stroke with oval rings more smooth than with round rings.

Or it could just be that my pedal stroke is off - what is the most efficient way of pedaling on a recumbent?

 

[Randyc3]

All great discussion. After my last post I did a quick search for tests showing the documented benefits of elliptical rings. 2 papers I found stated there is little to no difference between conventional round and elliptical rings. So I have to agree with TRPLAY that benefits cannot be proven. I’ll still be using my QXLs.
Did try Osymetric rings years ago- loved them but my knees did not. The ramp or transition is too aggressive.
Thanks and cheers.

 

[Apollo]

Did try Osymetric rings years ago- loved them but my knees did not. The ramp or transition is too aggressive. Thanks and cheers.

The one Osymetric chainring I ever used did not seem to give me the same performance as 'standard' ovals such as Rotor and other brands. A more even transition from narrow to wide axis of the chainring works better for me.

 

[TransAm]

I had switched to the Hinault Ogival chainrings a while back to help with climbing. These look weird, but are actually designed to give a smooth sinusoidal effort profile (the oval rings look smoother, but their torque profile is not). I set them up the same way Beano described above, but I only had the five 72 deg orientations to adjust for the angled chainline (the extra 4 holes are for 4-bolt cranks).

These did seem to make it easier to climb at a slower speed, but I didn't try going back to the round rings to confirm. Has anyone else tested oval chainrings specifically for climbing?

 

[Apollo]

I was looking at the Ogival chainrings a couple of years ago. There's some compelling info on their site but I never found any rider reports where these rings are compared to other ovals, and decided not to purchase them at that time. Did you ever try typical oval rings before to compare?

 

[bladderhead]

With the @TransAm one you are stuck with one angle. Mine has 5 possible angles.

 

[TransAm]

I was looking at the Ogival chainrings a couple of years ago. There's some compelling info on their site but I never found any rider reports where these rings are compared to other ovals, and decided not to purchase them at that time. Did you ever try typical oval rings before to compare?

No. What I read about the standard oval rings is that they are not oval enough to make a significant difference. The Osymmetric rings have a more pronounced shape, but I couldn't find what I needed, so I went with the Ogival. A guy I raced with at Sebring really liked them, so I went with that.

 

[Apollo]

No. What I read about the standard oval rings is that they are not oval enough to make a significant difference. The Osymmetric rings have a more pronounced shape, but I couldn't find what I needed, so I went with the Ogival. A guy I raced with at Sebring really liked them, so I went with that.

That's interesting. I've tried both regular Rotor Q-rings and QXL as well as Osymetric. I find the Rotor chainrings to be superior. That said, I do prefer a more pronounced oval shape but for some reason the Osymetric shape doesn't do it for me. Maybe because it's too irregular and less smooth or doesn't have the eccentricity in the right position for my needs. I'm very interested in trying the Ogival.

 

[Jim Parker]

This is my current V20 setup, the one I rode on BRAG and the 2022 Sebring Century (where I did my best time ever and set the recumbent course record). In this photo the up-pedal is approaching TDC or the point of maximum power on my forward-thrust. The blue-tape is pointing at the maximum diameter portion of the ring (tape put there just for this photo). I want the taut part of the chain to just be engaging the teeth at the widest part of the ring when my power is at maximum. That's a Rotor Aldhu 150mm
crankset with the built-in (In-spider) power meter. The point of maximum power may differ between individuals and bike
configurations (x-seam and chainstay length may affect where this is).

Jim

 

[Andrew Wilson]

Thanks @Jim Parker Great info. Now I need to take a closer look at my set up

 

[Andrew Wilson]

Thanks @Jim Parker Great info. Now I need to take a closer look at my set up

I set mine up with the ‘dead spot’ method. Checked today like @Jim Parker did and it’s very similar.

 

[TransAm]

@Jim Parker thanks for posting this. It also made me take another look at my setup posted above.

I also re-read this study: Biomechanical study chainrings - release 2.pdf. The authors created a mechanical model for evaluating non-circular chainrings, and suggested starting with the cranks roughly perpendicular to a standard bicycle seat tube when the major axis was vertical (i.e., perpendicular to a level chainline):

I did not have it set up like @Beano and you did, with the major axis (largest diameter) aligned with maximum leverage. It was actually set up more like the chainring designer originally intended, with the chain engaging the major axis after the pedals passed perpendicular to the imaginary seat tube line (between the hip joint and the crank axis). That roughly corresponds to the point of maximum leverage (assuming your hip joint is in line with the seat tube centerline as in standard bike design/fit).

I realized I have more adjustments than I thought with the 5 chainring bolts. The chainring has 180-degree symmetry, so the adjustments are 180/5=36 deg, not 72 deg as I had thought. That's not as fine as the 1 deg increments of your Rotor setup, but it lets me get within +/- 18 deg of any desired "ideal". And I don't think anybody knows the ideal angle with a lot more precision!

But it does force me to choose between putting the major axis slightly before or after the imaginary seat tube line. I advanced the timing so the taut side chain is perpendicular to the major axis just before the cranks are perpendicular to the imaginary seat tube angle:

My chainline is not as vertical as yours, even though I have the long chainstays. Also, I don't have to mark the major axis with tape, because the pointy end of the ogive is pretty obvious on its own!

After going over to the other side, I did a couple of long rides with this advanced timing setup, and my initial impression is that I like it better than the retarded timing setup. I think my last ride was my best ever on the V20! So I will keep it this way for a while before I try going back to retarded timing, or a round ring for comparison.

Note that my primary reason for using the ogival rings is for climbing, not for top speed, so my use case and experience may be different. That's why I have shown the chainline in the lowest gear (50t/50t).

Also, I have not tested for traction effects, which may be more important, i.e., which setup has less wheel slip to allow climbing steeper slopes? A related primary factor would be pedal steer, which would trump any other considerations. I didn't notice any pedal steer issues, but I would need to do more testing to be sure.