An intro Devlin Cycles Devlin Cycles
The 2021 Handmade Bicycle Show Australia was held over the past weekend and it proved to be the usual showcase of Australia’s thriving builder scene. The Melbourne-based show certainly attracts more road and gravel bikes, a symptom of where the custom bike scene is strongest, however many of the builders come with deep roots in the mountain bike world too.
The Trinity MTB
was one of the attention-grabbing steeds on display, and then trail bikes from Devlin Cycles and TOR Bikes were well worth a closer look, too. That TOR will be covered next, but for now, let’s look at Devlin’s prototype.
Devlin Cycles Prototype DetailsFrame material:
TrailHead Tube Angle:
490mm (for 5'10" rider)Price:
AU$8,500 (approx US$6,500), painted frame with shock.More info: devlincc.com
is the creation of Brisbane-based steel frame builder Sean Doyle. Doyle is an engineering draftsman by profession, and the merger of his profession and passion for bikes dates back to the 90s when he first drew up a first full-suspension mountain bike frame.
Fast forward to today and Doyle has a number of custom-built frames to his name, all sharing steel tubing, brazed construction and a few stylistic flourishes inspired by classic lugged construction that serve as his build signature. Those flourishes are effectively carved out sleeves that sit over the steel tubes, something that is known as bi-lam construction, and in addition to looking great, they help distribute forces through the tube and greatly increase the surface area of the brazed joints.
Devlin Cycles started as a classic custom steel road racing bike maker, however, Doyle has quickly expanded his builds into other realms. His most recent creation is this yet-to-be-named trail bike that he built for himself as a prototype to help refine the concept. Long reach geo
The goal with this bike will to offer entirely custom geometry, however, the concept of that geometry centres around a long reach that ideally overcomes the need for a super slack head angle or long trail figure. Standing at 5’ 10” (178 cm), Doyle is rather average in height, and yet this 140 mm travel 29er trail bike is built with a lengthy 490 mm reach and a 1230 mm wheelbase. That’s combined with 440 mm chainstays, a 77-degree effective seat angle and a not-so-slack 66-degree head angle. Doyle had originally designed a custom 20mm bar and stem combo but is happy with the existing 35mm stem.
“I’ve gone for a moderate head angle,” said Doyle. “I’ve done a lot of reading and absorbed some of what Peter Verdone
has written about and what Sam Whittingham from Naked Cycles
discussed on the Cobra frame building podcast
regarding long reach frames and moderate head angles. I did some thinking, and thought, well let’s just do a platform that makes sense in my head. Fortunately, it’s kinda got really close first go.”
The bike also looks tall and that was by design. “The bottom bracket is relatively high, firstly, my local area has a lot more rock and steps than a lot of South-East Queensland trails. [And then] one of the ideas in my head is that with the longer wheelbase, I wanted it to be a little bit more tippy, which may be a weird way to describe it, but as opposed to being really sat down and into the wheelbase and making it hard to turn, I wanted the weight higher up to get it to flop over a bit.”
“At the moment, for me, I wouldn’t change anything in the geometry.”Suspension design and the build
Creating a new full suspension bike from scratch doesn’t come together quickly, Doyle suggests he had over 400 hours in CAD work (Doyle’s profession) before spending a further 200+ hours creating the bike.
This prototype makes use of a traditional Horst Link suspension layout, however other designs were certainly considered. “I had spoken with Canfield at one point. I had also considered the DW linkage. But I went this route as I’ve got a lot of experience with it and I think it’s a good mix of pedalling platform, bump compliance and ease of design.”
“I had initially designed the main pivot to have some adjustment for anti-squat so I could tune that but it seems the centre position was right first go, so when I rebuilt the swingarm I took that out of it.” The result is a ride that Doyle claims to be quite balanced in the amount of anti-squat it provides and is well suited to his riding area where the terrain is rolling.
As shown, the front triangle is built with a Columbus 38 mm 29 downtube that’s been flipped upside down and extended in its length. The top tube is a Columbus 35 mm Zona tube, while the seat tube is a 35 mm Reynolds that Prova Cycles
helped to bend. “I then chopped up the seat tube, the top half is a thick 1.8mm walled tube to cope with not having the brace to the top tube.”
“[The] front triangle is using my bi-lam sleeves which carry over from my road frames,” said Doyle of the design element that’s both aesthetic and function. “It creates a really thick end tube section so that when you mitre the tube to the head tube you’ve got a really big surface area that creates a lot of strength in the joint... It comes back to aesthetics in that I don’t have to have such a big fillet in there and it creates a tidier finish.”
The frame is all silver fillet brazed, however, Doyle suggests that doing so makes for an extremely expensive frame. “I may go back to doing bronze because it’s cheaper, and there is a lot of filler. Bronze is harder to pull through the sleeves, silver is a lot easier, so it might be that the head tube stays silver because of the bi-lam sleeves and the rest moves back to bronze.”
Looking to the back of the bike, this prototype uses a swingarm that’s made with 4130 Chromoly round tubing and seat stays that are actually Columbus Zona chainstays, dropouts are the Syntace model from Paragon Machine Works. “There’s a lot of manipulation with the 4130 tubes and I have a lot of scrap from getting that right. This is the second swingarm I’ve created, this one is a lot stiffer and it’s to the point that I’m thinking maybe I need to back it off a little. I didn’t expect it end up here, it’s quite direct.”
Currently, a 29 x 2.5in tyre fits in the back, but Doyle has plans to replace a portion of the manipulated 4130 tubing with a 3D printed stainless steel yoke that should more breathing room around the tyre and ease the build process, too. Doyle is considering using 3D printed stainless steel for the dropouts, too.
“I’d like to do another prototype to nail out some things. For example, the bearing configuration details, I’d like them easier to make and using less parts. That main pivot would likely annoy people to pull apart and put back together again, I’m already upset with it. So that will be redesigned so it’s simpler.”
And Doyle is still thinking through a few other elements, for example, the suspension linkage is currently CNC’d aluminium from a Brisbane-based supplier. The original plan was to use a printed metal part here, but Doyle quite likes the organic look of the machined alloy. Want one?
The fetching two-tone candy paint on this prototype is the work of Wallis Paints
in Brisbane and would add further cost to the bike. Speaking of the paint, Doyle joked that it’s not the most practical thing. “Don’t make it look like a show bike, any touch up requires a full respray.”
Doyle is clearly still sorting out the finer details but didn’t dismiss the idea of taking on orders already. Of course, a custom geometry bike with this number of fabrication hours isn’t cheap, and you can expect to pay about AU$8,500 (approx US$6,500) for a painted frame with shock.