Egg rings on a 'bent

[Blodwyn Pig]

Has anyone played with egg rings/ biopace/whatever they are called now, on a bent? I know it's got to be a smooth spinning action, but surely there would be some advantage, especially when clawing up a hill at slightly less than optimum rpm ?

[Wobbly John]

Will Cook used to have them on his Dawes. I don't know if he still visits YACF much.

[dat]

I did on an ice and then on a speed machine. Oval rings and short cranks worked best for me. I regret selling my speed machine...

[RichForrest]

Will Cook used to have them on his Dawes. I don't know if he still visits YACF much.

I sold that one to him  they were on there when I brought the bike back in 2006.
https://photos.app.goo.gl/ioLo65APhyjAcqJn9

Most noticeable when climbing slowly, definitely smoothed things out as you don't get that lurch with each pedal stroke.
If you're a spinner you won't notice it as much as you would mashing on the pedals.

[ElyDave]

I know of people putting them on Cruzbikes, with lots of debate about putting them 90-deg out of rotation vs an upwrong

[Blodwyn Pig]

I did on an ice and then on a speed machine. Oval rings and short cranks worked best for me. I regret selling my speed machine...

Is that, 'Oval rings and short cranks'/ or Oval rings THEN short cranks, or Short cranks THEN oval rings? Or did you change the chainset complete.trying to work out which had most benifit out of the two.

[dat]

I used oval on the ice trike, then short on a trice, then short and oval on the speed machine. Short made more of a difference to me but if I ride recumbents again (which I probably will) I will use both.

[Blodwyn Pig]

I used oval on the ice trike, then short on a trice, then short and oval on the speed machine. Short made more of a difference to me but if I ride recumbents again (which I probably will) I will use both.

what length cranks were they?

[dat]

150mm on the micro, 155mm on the speed machine

[Blodwyn Pig]

I used oval on the ice trike, then short on a trice, then short and oval on the speed machine. Short made more of a difference to me but if I ride recumbents again (which I probably will) I will use both.

In what way did it make a difference, (how tall are you) ,  i can imagine if you've got long legs then 155 cranks would be too short.?

[dat]

Helped with fatigue, I’d presume it was because you are lifting your legs above your hip. I’m 5ft 10 but with short 29/30inch inseem.

[Blodwyn Pig]

Helped with fatigue, I’d presume it was because you are lifting your legs above your hip. I’m 5ft 10 but with short 29/30inch inseem.

Ah, ok,  but I suppose the BB is higher above the seat on a trike and a Speedmachine, than a Streetmachine.

[Kim]

The general consensus amongst racers of faired recumbents is that there isn't a significant disadvantage to shorter cranks (assuming you've adjusted the gearing appropriately, and the rider is used to them).

Not sure if that still holds when you aren't getting the aerodynamic/weight benefit of a smaller fairing to more than offset any biomechanical inefficiency, thobut.  There must be a point where cranks become 'too short', but I'm sure it's a lot less than 155mm.

FWIW, I'm 5'6" and have until recently been using 155mm cranks on my recumbents.  (I've switched to a 140mm left crank to prevent overextending my shorter leg.  It's stopped the Achilles pain dead, but I'm still getting the hang of the change in gain ratio.)

[Tigerbiten]

I cannot use oval rings on my bent trike.
My Schlumpf HSD spins the chainrings at a different speed to the cranks in the overdrive mode.
Plus when shifting out of overdrive the final orientating of the chainring/crank is a bit variable.

I would like to try shorter cranks.
But Schlumpf only make 170mm kick plates.
So if I fit shorter cranks, I'll need to modify the kick plates to fit a shorter length.

Luck ........... 

[Auntie Helen]

Or drill a new crank thread in your existing Schlumpf cranks.

My Bafang cranks have an extra hole drilled so the pedals are 155mm instead of 175, but are still the original cranks.

[Gattopardo]

I know of people putting them on Cruzbikes, with lots of debate about putting them 90-deg out of rotation vs an upwrong

Didn't sheldon say something about that?

https://sheldonbrown.com/biopace.html

[Mr Larrington]

Not sure if that still holds when you aren't getting the aerodynamic/weight benefit of a smaller fairing to more than offset any biomechanical inefficiency, thobut.  There must be a point where cranks become 'too short', but I'm sure it's a lot less than 155mm.

Rob Hague once tried some deeply silly cranks on a Greenspeed trike and reported that 75mm was 'too short'.  Greenspeed bossman, the late Ian Sims, was an advocate of long cranks.  210mm or somesuch, as any longer would have caused his heels to be under the tarmac for a significant period.

[PaulM]

I have a triple set of Rotor Q-rings in 30/40/53. I tried them fairly briefly on a couple of bents. I  think the theory is sound but the Q-rings aren't ovalised enough to makr much differece. Crawling up a hill using the granny was smoother though. They weigh a bit more than round rings and you have to adjust the FD to cope with the ovalisation.