Qrings
- Thread starter Doug Burton
- Start date
Doug Burton
Zen MBB Master
Well Done, Jack,
Very interested in what you learn.
They're super adjustable, and I'll be interested to find out where you select your optimum eccentric point to be.
Best,
Very interested in what you learn.
They're super adjustable, and I'll be interested to find out where you select your optimum eccentric point to be.
Best,
defjack
Zen MBB Master
Heres an update on my Q rings. First I followed the Recumbent instructions and after a 45 mile ride didnt notice much change.Next I started trying different ring positions.I tried about 10 holes untill there was one that felt pretty good.Did the same 45 mile ride on the new position and that was much better. Like the change from narrow road bars to the wider Origin 8 bars. Now I feel faster and climb better.No shifting problems at all because I was able to rotate the derailer after one hole on the bracket was filed out. It was kind of strange as the new setting was 90 degrees from the recommended setting. Jack
John Tolhurst
Zen MBB Master
Jack,
looking at the bike from the right hand side, and starting at 0 degrees being straight up, and measuring degrees clockwise, this is my guess at your favoured setting:
Major axis is at 40 degrees.
How did I go?
looking at the bike from the right hand side, and starting at 0 degrees being straight up, and measuring degrees clockwise, this is my guess at your favoured setting:
Major axis is at 40 degrees.
How did I go?
I'm not sure I understand the orientation of the cranks where John is asking for the angles measured from either, so I'll specify my setting differently, and I'm sure you can translate it. Looking at the right crank, I measured how many degrees counter-clockwise is the major axis of the ellipse. For me it's 7.5 holes, or 77.14 degrees. I have no reason to believe this is especially optimal, I just don't like making mechanical changes so I've only tried the one setting. There were a couple points during the instructions (picking the dead spot, and picking where the chain touches the chainring) where there wasn't any clear unambiguous answer and I could have gone quite a few degrees either direction. But for me the result is so much dramatically better than the previous round rings that I don't have any real motivation to try fiddling with it further.
I do need to mess with the derailler again though.. the other two chainrings (big and little) are just barely usable right now.
- Mark
I do need to mess with the derailler again though.. the other two chainrings (big and little) are just barely usable right now.
- Mark
John Tolhurst
Zen MBB Master
yikes, nor me! Lets draw.
This is what I understand is being espoused by rotor cranks. That max power is about 3/4 through the power side of the stroke, because of leg momentum they say (which I think actually is the far greater strength the leg has when it is more extended).
So, anyhow, the drawing says that on the 39 ring and 19 sprocket, the retard angle is 91.6 on the Silvio with median leg length rider.
John Tolhurst
Zen MBB Master
http://www.ptjournal.org/cgi/content/full/87/9/1243/F1
http://www.ptjournal.org/cgi/content/full/87/9/1243
Note that zero degrees is the crank dead spot, and that about 45 degrees before this there appear many muscle groups activated.
http://www.ptjournal.org/cgi/content/full/87/9/1243
Note that zero degrees is the crank dead spot, and that about 45 degrees before this there appear many muscle groups activated.
Mark B
Zen MBB Master
OK, wait... Did I miss something?
I thought we were talking about Q rings, which are elliptical chainrings. In my mind's eye, the big question is; where is the crank in relation to the oblong ends of the rings? Then again, my mind is known to be blind in one eye, can't see out of the other.
Mark
I thought we were talking about Q rings, which are elliptical chainrings. In my mind's eye, the big question is; where is the crank in relation to the oblong ends of the rings? Then again, my mind is known to be blind in one eye, can't see out of the other.
Mark
It's true there's only one angle you get to pick when you install the q-rings, and that's as you said, the orientation of the ellipse relative to the cranks. But there are other angles that affect that choice. One is what crank position you pick as the dead spot (I picked straight horizontal, same as it looks like John did). The other is the angle where the chain makes contact with the chain ring. This depends on the bike design and what gear you're in.
So my interpretation of John's diagram is that he's got 91.6 degrees from the ellipse's major axis to the crank, so the crank ends up at 45 degrees up from horizontal when the ellipse is at its largest diameter at the contact point with the chain thus delivering the most resistance. In my setup my cranks are only 77 degrees clockwise from the ellipse's major axis, so my "highest gear" comes several degrees earlier.
- Mark
So my interpretation of John's diagram is that he's got 91.6 degrees from the ellipse's major axis to the crank, so the crank ends up at 45 degrees up from horizontal when the ellipse is at its largest diameter at the contact point with the chain thus delivering the most resistance. In my setup my cranks are only 77 degrees clockwise from the ellipse's major axis, so my "highest gear" comes several degrees earlier.
- Mark
Oh, except my legs are longer than medium, so that probably make my retard angle smaller, meaning my crank position at "highest gear" isn't as much earlier than the 45 degree point as I at first though when comparing to John's diagram, but I might still be a little earlier.
- Mark
- Mark
Okay, I'm really surprised by that (defjack's q-ring position). It seems to me that where the chain begins making contact with the chainring at its largest diameter would put the cranks somewhere between horizontal and their current position in jack's picture. Compare that to mine
where I've attempted to put the cranks in the position where the chainring is in its "highest gear", and my crank is somewhere around 45 degrees up from horizontal. I still have trouble deciding exactly where the chainring is first making contact with the chain though. If I should be picking the point at which the chain is making a right angle with a radial line through the chainring, then I should have taken my picture with the cranks rotated a bit further counter clockwise, meaning I might have my high gear occuring too early.
- Mark
where I've attempted to put the cranks in the position where the chainring is in its "highest gear", and my crank is somewhere around 45 degrees up from horizontal. I still have trouble deciding exactly where the chainring is first making contact with the chain though. If I should be picking the point at which the chain is making a right angle with a radial line through the chainring, then I should have taken my picture with the cranks rotated a bit further counter clockwise, meaning I might have my high gear occuring too early.
- Mark
WhiteSilvio
Well-Known Member
Just looking at the setup, and well, for what it's worth, I think it should look more like this with the major axis about 30 to 40degrees anticlockwise back from the crank at "level dead centre".
John R.
John R.
John Tolhurst
Zen MBB Master
We really need some simple language around this. May I propose the following:
1) Angle Between Bottom Dead Centre and the Chain Tangent Point at the Ellipse Major Axis. Lets call this the Tangent Angle
2) Desired Angle Between Crank and Chain Tangent Point at the Ellipse Major Axis. Lets call this the Power Angle
To set up the rings, calculate the Retard Angle, which is 1) - 2). The Retard Angle tells you how far behind the cranks you should place the major axis of the ellipse.
To take measurements, just count teeth and note how many teeth on the ring. (True, number of teeth on an ellipse its not a regular measure of angle, but for our purposes it will work.)
To take pictures, place the major axis at the chain tangent, so we can see the orientation of the crank. I think that will allow us to compare cases and build some collective understanding.
1) Angle Between Bottom Dead Centre and the Chain Tangent Point at the Ellipse Major Axis. Lets call this the Tangent Angle
2) Desired Angle Between Crank and Chain Tangent Point at the Ellipse Major Axis. Lets call this the Power Angle
To set up the rings, calculate the Retard Angle, which is 1) - 2). The Retard Angle tells you how far behind the cranks you should place the major axis of the ellipse.
To take measurements, just count teeth and note how many teeth on the ring. (True, number of teeth on an ellipse its not a regular measure of angle, but for our purposes it will work.)
To take pictures, place the major axis at the chain tangent, so we can see the orientation of the crank. I think that will allow us to compare cases and build some collective understanding.
Peder Torgersen
Guru
Mark B wrote:
I think my brain just farted. Right there's a retard angle for ya!
Mark
If there is an ideal position that gives a benefit that’s very good.
Mark when do you get up in the morning to answer on the forum? :roll:
Peder
Mark B
Zen MBB Master
When I ride to work, I get up at 4:00 AM. I sit down at the computer with my cup of coffee and my bowl of cereal to see what's going on in the world when I should be sleeping. Then, I ride to work, take my shower, get dressed and sign on again to see what happened in the last 2 hrs. Simple, eh?
Mark
