Put me down for 2 
I would prefer 203mm and 2.3mm thick.
I hope UDC UK can sort out the manufacturing needs!
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Me (depending on price, of course)
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So, here are the latest news: Roger may be able to sort this out for us. However, he doesn’t want to lose money, as he did on the BrakeFast project. That’s totally fair of him, and I personally think he should be rewarded as he helps us sorting out the issue as his job.
Here’s the deal: if we get at least 7 statements of intent of purchase, we should be able to process the ordering. The price is yet unknown, but it should be under €150 so they would be shipped to EU without duty. We still have to figure out if all rotors have to be the same (thickness/diameter). I’ll let you know as soon as I have the answer.
Regarding the specs: The rotors will be profiled and hardened (Stainless 410 hardened to 32-38 HRC). It is still unknown whether they will be countersunk. Hope can’t countersink the holes, but we may arrange something with Roger.
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@Elias Are you interested?
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Sure, put me down for one rotor (203mm preferred).
I still have a functional BrakeStuff rotor for each hub, but I wouldn’t mind having a backup.
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Can count me in for one 203mm rotor at 2.3mm thickness 
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Perhaps also if they want to pre test any design that’s decided on it could be printed on a 3D printer (Roger might you oblige?) and tested for fit on a hub - happy to check it it fits.
I would hope that the countersinking into too hard to do after any production work from Hope.
Very curious if they’ll make a design that follows BrakeStuff or what @finnspin is working on 
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It seems like they are waiting for us to send them a design. So, if @finnspin is OK, we’ll laser cut his design 
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I just performed some tests with the design I received from @finnspin. For these tests I just 3d-printed only the interface itself, not the entire disc.
The interface towards the hub matches the profile of the original disk quite nicely, but it was too tight to put onto the hub without any kind of filing.
I printed 2 additional tests, where I offset the interface spline by either 50um or 100um (e.g. 100um or 200um larger inner diameter). The print with the 50um offset I was able to mount onto my hub without filling, but it was a very tight fit (press-fit?). The 100um offset one nicely slid on, and the amount of play felt roughly similar to that of the original disc.
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I haven‘t yet taken my final decision, but I‘m probably out - 150ish € is a lot of cash for a brake disk. Not saying that it‘s unjustified as far as the end product is concerned. But with shipment, duty and VAT I‘ll be likely to pay around 200 bucks. Under these circumstances it probably makes more sense for me to try and DIY an adapter myself, using an existing floating type disk…
Then again, let‘s see what the final quote for the disk is …and what dimensions (180/1.8 preferred).
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Awesome, thank you! I will add an extra 0.1 mm of clearance and send the design to @Maxence & @rogeratunicycledotcom (today or tomorrow most likely) so they can continue the discussion with Hope
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€150 Euro (about £130) is the max that can be sent under the IOSS scheme. It is not how much the disc’s will cost! Sending under the scheme means that you do not pay VAT or Duty on import it is sorted at our end. So the price it is sold at is the price you pay. What this may do though is stop you getting 3 or 4 in one go!
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Something for discussion…
Hope’s own discs are 1.8mm for less than 180mm and 2.3mm for above. I suspect this is for integrity of the disc ring as it expands on the bigger size rotors. What is everyone’s thoughts on this?
I suspect we will only be getting one thickness of rotor.
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I got that, but since I live in Switzerland the max amount before having to pay VAT (and duty, and a handling charge) is around CHF 60, including shipment (which is always more expensive than shipment to / within the EU). So there‘s no way for me to get around those additional costs, unless the disc is in the € 40 range.
As to the thickness: My guts tell me 1.8mm should be enough (considering the large hub diameter), but I have virtually no clue about disk brakes. Common opinion seems to be to go for 2.3mm.
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If only there were people coming from the UK to Switzerland during the summer, they could maybe bring the rotor(s) with them…
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Hi @finnspin, thanks for sharing this new rotor design—I think the swept‐arm geometry and directional spoke layout are heading in a good direction. I’d like to offer a few suggestions that might help reduce heat‐induced distortion and improve overall strength:
- Taper the spokes so they’re thicker at the hub and finer toward the outer ring
Right now the spokes look fairly uniform in section. If you make them a bit chunkier where they join the hub and gradually taper down as they approach the outer ring, they’ll still flex predictably under thermal expansion but carry load more efficiently closer to the hub. A finer cross‐section outboard also reduces mass at the hot zone, which can help the rotor “bloom” evenly without putting undue stress on each spoke. - Increase the O.D. of the mounting ring by a couple of millimeters
If the outer mounting lip is just a hair larger—say +2 mm—the spokes won’t have to twist as they flex outward. That extra clearance lets the ring expand unimpeded when it heats up under heavy braking. Just be sure that mounting flange is uniform all around so there’s no spot where a spoke could bind or rub as the disc blooms. - Use more spokes (and make them finer)
I counted six spokes on a 203 mm disc, which does feel a little sparse if you want really smooth, uniform expansion. If you bump up to eight or even ten slimmer spokes (still swept and directional), each spoke carries less individual load. The ring will “float” more consistently, giving a quieter, stabler feel under heavy use.
One more thought: I noticed the two circular holes near the tip of each spoke. Do those serve a specific function (heat relief or weight savings), or are they just for looks? My concern is that, as the disc rotates and flexes under heat, those holes could become stress concentrators and eventually lead to cracking. If you need cutouts there, you might consider a small triangular relief instead of round holes—the sloping sides of a triangle tend to transition stress more gently than a circle, which can help avoid a fatigue crack path.
If it’s not too much trouble, would you mind sending me a DXF of your current spoke layout? I could sketch out some of these ideas (showing revised taper profiles, the enlarged O.D., and an alternate hole geometry) so it’s easier to visualize. A small DXF file should pass through my email just fine—if you’re willing, please send it to contact@unicycle.co.uk and I’ll put together a quick annotated drawing.
Thanks again for sharing, and keep up the good work!
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Great input!
Nine would be a nice touch, on a Schlumpf…
Also, the more gentle the outer edge, the smaller the risk of bad injuries.
Question on the outer notches normally found on Rotors… Anyone know what they are for? I suspect it is for clearing dust, but I don’t actually know.
+1.
Yes, I think it is for cleaning the pads. Galfer have their ‘wave’ and ‘shark’ discs which are supposedly shaped to remove mud. The shark ones look pretty neat with the shark fin/teeth on the inner side of the rotor (which is probably why they say ‘patented’ on them) – you can certainly see how those would clean stuff away.
Hope used to do a more aggressive sawtooth rotor, I have one on my KH26. I assume that they stopped doing this for safety reasons in a similar way to the move to doing smooth edge discs for road use (in response, I think, to the UCI ban on disc brakes for safety reasons at one point).
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The notches are the equivalent of the holes in the middle of the wear surface. Clearing dust, and giving any gases that the brake pads create when they heat up a chance to escape. How important that is in practice I’m unsure about, but I would include them.
Not all disks follow this, but I also heard that it is generally advised to make the percentage of hole to solid as even as possible for any given radius (To creates more even pad wear). Notches extend this to the ends of the disk.
I will revise to a 9 spoke design, should be quickly done. (Luckily I kept that part of the CAD model clean and parametric) 
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