This was a mechanical hack for a test set-up, not for riding the bike.
In 2011 I wanted to test Q-Rings, if they improved my biking relatively to
round rings. For this I made a set-up with two 53-chainwheels next to each other,
one round, one a q-ring, such that I could
move the chain back and forth during test runs. That looked like this:



I put the results of the test hereunder for those who are interested:


Of course I had to move the chain between the test runs by hand, because the frontderailleur doesn't work with two 53-wheels.
The chain was on the 17-cog, which was not exactly between the two rings, but it cannot be all perfect...
The Q-Ring was mounted with OCP-value 3.

For the test the bike was mounted in the tacx flow with setting "constant wattage".

I tested at quite low perceived-intensity with pedaling frequency of about 80.


One test run was as below:
2'30'' with 220 W round ring : write down HF at the end.
1' with 130W regeneration
2'30'' with 230 W round ring : write down HF at the end.
1' swap chain and with 130W regeneration
2'30'' with 220 W Q-ring : write down HF at the end.
1' with 130W regeneration
2'30'' with 230 W Q-ring : write down HF at the end.
1' swap chain and with 130W regeneration

I did five same test runs which lasted in total thus about an hour.

Result of the test:
test run:--------------------------1-----2----3-----4----5
220 Watt Round ring HF: 116 116 118 116 114
230 Watt Round ring HF: 120 121 119 121 117
220 Watt q-ring HF: ------- 117 119 117 117 114
230 Watt q-ring HF: ------- 121 121 121 119 117

Conclusion:
There is a significant difference between the runs with 220W and 230W: about 3 heart beats.
10 W difference is about 5 % at 220/230W and is thus clearly noticeable in the Heart Frequency.
Comparing the round and the Q-ring, there is no significant difference. The difference must be at
least a lot smaller than 5 % or 4 % (with which Rotor advertised in 2011) because that should have
been noticeable, as can be seen from the difference between 230 and 220W.


(in the fifth run the HF was lower: probably because I was warmed up).


Although I did thus not see any difference, I decided to leave the Q-Rings on, since Rotor says your body adapts to them.


In 2012 I did the same test again, and found again no difference. That's when I decided to go "round" again.

By the way, since I rode 3 chainwheels on the front in those days, I needed another "hack" for my frontderailleur to work with Q-rings on the street: