Bizarre older Litespeed frameset with rear horizontal dropouts.
I thought sheldon brown decided that you gave up your right to ride if you refer to trackends as horizontal drop outs?
I nearly said “thingys” 
anyway, how can you have track dropouts on a triathlon bike?
horizontal dropouts have a fair bit of room for adjustment as well. as long as you get the wheel straight it shouldn’t be an issue. the advantage of horizontal dropouts though is those little adjustment screws that mean that the axle can’t go any further in so you know that’s where to clamp it.
That said, I don’t know if QR skewers could provide enough pressure/surface area to either stop the wheel slipping or the nuts from gouging the metal.
That is one of hottest bikes I’ve seen in a long time.
Horizontal dropouts allow you to move the wheel while still keeping the brake shoe aligned with the rim. Track ends don’t do that.
A QR skewer would be just fine. There’s the same amount of surface contact, it’s just pointing the other way.
The Paul track ends have adjustment screws too.
There are a few other TT/Tri frames out there with track ends and a derailleur hanger.
For semi-hor/track ends a QR skewer is fine, as long as it is steel with steel clamping faces. An aluminium skewer, or aluminium faces are only ok for use on vertical dropouts, where the wheel can’t be pulled forwards.
Why is that? Is it always the case?
As usual, Sheldon says it better than I could:
Internal cam, steel surface QRs are best for non-vertical dropouts.
There’s an interesting link on Sheldon’s page about front disc brakes generating forces that can cause QRs to loosen.
Those drop-outs would make the job of replacing the rear wheel a complete bitch right? Hold frame up, hold wheel, pull chain far enough back for wheel to get in, align frame and wheel, put wheel in let chain go…You’d need to have arms like an octopus to coordinate the task 
I never realised that. Quite ingenious really.
I was more concerned about which way the forces are being applied. The weight of your arse on the saddle is going to push the axle towards the top of a horizontal D.O. The axle needs to resist this force before it’s going anywhere.
Ok, who wants to work out the component of the rider’s vertical load that is acting to move the axle backwards in the DO and compare that to the torque applied by pedalling acting to pull the wheel forwards? Remember that the angle (~20º) means that only ~22% of your weight is acting to move the wheel back, compared to ~78% of the drivetrain load acting to pull it forwards.
In my experience, I’ve pulled a wheel forwards mashing on the cranks (fixed, uphill & geared, QR too loose), but never had the wheel slip due to my not so weighty arse.
Yeah I’ve shifted the axle a couple of times whilst mashing on my last road frame. It’s never shifted on my new frame or my fixie (all three have/had horzintal dropouts).
For me, a good QR is far better than a nutted axle. its quick and its strong and it is nice to your frame. A bad QR is far worse and gives QRs in general a bad name. Shimano QRs are superb, in my experience. I’d like someone to do a study on actual (lateral) clamping force of a nut vs QR… i think you’d need a pretty long lever (spanner) to apply the same force.
My communter pig has rear-facing dropouts and a derailleur - wheel removal/fitting isn’t a big deal once you’ve done it a couple of times. I use a decent quick-release with it and have never had an issue.
There are a few production tri/TT frames around with deep cutouts in the seat tube and rear-facing dropouts, the idea being you can tuck the rear wheel as deep as practically possible into the cutout to get the aero benefits.
Here’s an example (albeit not really a production TT bike):
Something odd about the bent seat tube on this. The Litespeed Ultimate used to have such a tube, then in around 1997 the UCI made it illegal (I had one, and thought I might get busted by some overzealous club official), so after that, they made the tube straight and put a cut-out in it instead. But I seem to recall seeing some recent bikes (Cervelo?) with bent seat tubes.
