Ever since I had my On-One Inbred 29'er as a SS, I've been dealing with chain tension with a QR. The forward facing horizontal dropout (not a track dropout) adds even more of a problem. This is a nagging issue if you've converted an old MTB (such as my 1986 Rockhopper) to a SS.
The most known set-up that actually works well is by purchasing a set of Surly Tuggnuts with QR adapters. Theoretically, you only need one on the drive side, however, I have had the non-drive side slip on a hill mash - and it sucks. From there, you use brute force to tighten the QR to keep it from doing that again, or, you buy two Tuggnuts - one for each side. With the adapters, Tuggnuts cost about $30 a piece, so this isn't the cheapest way to go. And ultimately, the real problem with two Tuggnuts is the QR rod is too short to for a safe, solid set-up.
I have finally found a set-up that works - and works well. The following are instructions on how to correctly tension your single speed with the use of a QR and forward facing horizontal dropouts.
What is Needed
You will need to modify the BMX chain tensioners by removing the "stop plate" on the backside. There is a tiny e-clip that holds it in place. which you may try to wiggle off with needle nose pliers. I simply broke them off mine, knowing I wasn't going to need the tensioners in their original form. After removing the stop plate, this is how it will look like. I also removed the nut, opting for blue thread lock, instead.
Notch the rear of the dropout with a file. Do this so that the modified chain tensioner won't move or slip out of place when putting it all together. The "screw pin" on the tensioner will be placed in the notch accordingly. The notch doesn't have to be deep - just enough for the screw pin to settle in.
Assemble all the parts together, using the Toba Quincy extra long skewer. The extra long skewer will be long enough to hold both tensioners and the adapters and still have plenty of thread left. This photo shows how the screw pin on the tensioner fits into the notched backside of the dropout.
Carefully adjust your chain tension by tightening the screw pins on the tensioners. You don't want your chain too tight, but snug enough so that it doesn't drop. I like to have the skewer slightly clasped when tensioning my chain. Find the appropriate chain tension and tighten the skewer down. Give the tensioners a final tighten so that the pins are firmly against and placed in the notches. Since you are using chain tensioners on this set-up, there is no need to over tighten the skewer with fear of it slipping.
This was the "econo" version of this set-up - the same thing can be attained with Surly Tuggnuts, QR adapters and the Toba Quincy XL skewer. With Tuggnuts, you will not have to notch the dropouts.
I hope my how-to has helped solve this nagging issue. I've tried about a dozen set-ups and each one was either sketchy, or just didn't survive the trail. Please feel free to share this.