We had a hooded UDH at the 2019 PBE, we may have been ahead of our time. It bombed pretty hard, because few builders knew that it was the gateway dropout for SRAM’s coaxial derailleur. I may have a couple steel ones left if you want to try it. It is 1-3/4" diameter on the right side, 1-1/2" diameter on the left. The two sides are concentric, so the idea is to miter one side of the stays, switch hole saws and miter the other side. Some builders may have seen this as too much work. This dropout meets all of SRAM’s specs for UDH. Photo below. Combined with our BK2016, it will do what you’re asking for.
We are working on a hooded flat mount dropout with integrated brake mounts. It has two right sides that are interchangeable, for UDH and our snap ring hanger. We’re still working on the cosmetics, that’s turned out to be a real hurdle. There’s a lot going on here.
We’re considering two versions, and would like some comments. I’ll call the first the small version. It will be 140 FM, with small hoods for 16 mm stays. It will have clearance for a 160 FM adapter. The large version will be 160 FM, with hoods for 3/4" seatstays and 7/8" chainstays. It will have clearance for a 180 FM adapter. This is the one to put a post mount adapter on.
FYI, Fairing makes several tapered 22.2mm w/ different butts. Unfortunately, I think 22.2 stays is a minority, but those tubes might help you get there.
Wow, totally flew under my radar! I like the idea of different sizes left and right. Agreed that the aesthetics are the hardest part of this design. Do you have a CAD drawing or STEP file for review? I can drop it into one of our 3D bike models to help people visualize.
I don’t think that say: 27mm instead of 25 is something unreasonable to request. I can work with 25mm and 7/8 stays. I’m sure it’s also fine for welding, but it’s a bit tight for brazing. There is no good way to make triple bend stays with tapered tubes.
This is the .STP file for the right side: DR2072.STEP (112.5 KB)
A dummy axle for this may be a challenge, as the dropout slots are at slightly different angles. You’ll see when to get the files in your CAD program. I’ll try one of our UDH dummy axles and see how it works.
Post mount on the chainstay is always going to be a clearance issue, and an adapter will probably make it worse. A simple solution is to bend the seatstay to make clearance, but that is another step, and not everyone likes the esthetics of it. Plan ahead!
Even though I originally thought an asymmetrical design wouldn’t be an issue, it looks like it could indeed be a problem with customers thinking the frame is misaligned. Plus, there’s the extra work to make it work.
I look forward to seeing what Mark is currently cooking up.
There’s some precedent for asymmetric stays, and by effectively shifting everything to the non-drive side a bit you could be doing the work of undoing the net amount of ai-offset in the world.
I’ve been thinking about this a lot in a road/gravel context. I drew up some dropouts that were asymmetric (adding some space to the NDS) so that the stays themselves would be symmetric. The dropouts aren’t exactly the prettiest thing I’ve ever drawn, but they look fine when built into a bicycle with a caliper, wheel, and rotor in there.
That being said I don’t think that’s the avenue I would purse for smaller bikes, though I think it’s fine for mountain bikes. Personally I have no objection to asymmetric stays, since ultimately I’m designing bikes and not frames as standalone objects. That’s the direction I’m going for UDH gravel bikes.
I’d love to see a readily-available hooded dropout. Even if it relies on a small amount of fussing with stays, I think it would provide an option for people to experiment with. And the more people who are experimenting, the more options we’ll see out there for solving this problem.
OK, there’s a lot going on here. I thought I had some of these UDH dropouts laying around, but I can’t find them. The clean up purge must have found them. That means if we’re going to do another batch, some changes can be made.
@Daniel_Y and others mention that asymmetry may be a deal killer. I’m not the builder, but I’ll argue that if things need to be asymmetric to build the bike a rider wants, asymmetry is not an insurmountable hurdle. @manzanitacycles mentioned it may look like the frame is not properly aligned. Good point, but a typical rider won’t see it. It’s just us frame building nerds who will notice. @DEVLINCC mentioned that asymmetry is why he prefers plate style dropouts, but with UDH and a plate style dropout, asymmetry is still a design element to solve. @jeremy mentioned he can handle the asymmetry if needed, but offered a solution with wider flanges to get to a symmetric rear triangle.
This last comment gets to the point of PMW making a fresh batch of updated UDH dropouts. Do builders want symmetry enough to buy a dropout that is wider, which is more weight and less heel clearance, or does a narrower, lighter DO justify asymmetry? Full symmetry means making the left side 1-3/4" diameter as well, adding to the weight. It may be possible to use less than 1-3/4" diameter, but as I recall from our original design, we couldn’t meet all the UDH spec with anything smaller.
There are still some things to consider with UDH and round hooded dropouts. To meet all the UDH specs, the right chainstay must meet the dropout fairly high, almost on center. See @Daniel_Y first pic, side view. With 1-3/4" diameter there’s plenty of room to make the miter, but some may not like the esthetics of this. The other thing to consider is that the UDH spec forces rack/fender eyelets higher than usual on the seatstay. Is anyone planning to build touring/commuting/city bikes with UDH? Is this even an issue?
I see this as a project to design an updated UDH hooded dropout. What do all of you, as builders, want? Are there any riders looking at this that want to comment? We can do these in steel for around US$50.00, but it’s not worth it unless we have a clear design consensus and sales to justify the work required.
I agree with @Daniel_Y that the scope for now is mountain bikes. A little extra weight isn’t a deal killer for the flexibility of wider flanges to accommodate larger diameter chainstays. Builders who use tapered chainstays can always grind the flanges narrower if they like.
Something like Daniel’s design looks really nice. A hybrid hood and plate looks great.
As soon as we depart from a purely round exterior shape, the price rises rapidly. The exterior profile must be machined, as opposed to buying round bar that’s already a usable size and shape.
More questions: Are builders willing to pay significantly more for a dropout shape that’s not round? What are the advantages to a builder with a non-round shape?
I think gravel/road UDH will eventually get here from SRAM, it’s too big a market for them to ignore. The current UDH will work with any derailleur, but perhaps not optimally. People forget that Syntace was originally a mountain bike standard. There’s never been a gravel/road hanger built for it, and nobody notices. Same with UDH.
Price for a non-round version will be roughly $70 for steel. I like your version a little better, because there’s more angular range to land the seatstays. Which brings up an idea, is there any advantage to making the chainstay hood flat, so that the chainstay miter is a straight cut?