Brand New Tech: The Sequence Downhill Bike - Crankworx Les Gets 2018
I met Vladimir Yordanov on a chairlift two years ago in Morzine. I was testing brand new downhill bikes and he was riding a ratty old Mondraker Summum with a Manitou Travis fork and Marzocchi Rocco shock. We had a huge chat about bikes, geometry, and suspension tuning, and he was seriously into it. The reason that he rode that bike? Because everything was adjustable including the suspension which was fairly easy and cheap for a student to open up, tinker with, and play with the shim stacks.
Last night he messaged me a picture of this bike and asked if I want to take a look at it. Yes, preceded by the f-word was my response and we met this morning. It was one run old when we met, literally one run down from Morzine to Les Gets and it didn't even have a name when he arrived. He decided on 'Sequence' during our meeting. So I present you the Sequence downhill prototype.
One man and his bike. Vladimir started this project in 2011 and finally rode it down the mountain this morning. That might seem like a long process, but between University, work placements and more than full-time employment, it's a fantastic achievement.
History
At 26 years old, Vlad moved to the UK in 2011, studied at Loughborough University to do product design and always wanted to make bikes. He said he never used the workshop for the assignments he was meant to do, but started carving foam models of frames and then rendering bikes with CAD. Previously, Vlad has designed some crazy looking aero road racer for Reap Bikes in the UK. He is also working on jet skis, trials bikes, and automotive parts for various companies.
 | I had been on a placement at Vax vacuum cleaners just doing renderings which should have been 12 months, I just got bored of that and then met Martin from Reap Bikes, I showed him a foam triangle hand carving of this bike and he told me he would help me make a downhill bike if I designed him a road bike. I quit the Vax placement after six months and went to work for him. Of course, I started with geometry and we found some things we didn't like, so we did the usual longer/lower/slacker, haha. Everyone was pushing me to buy a bike [because he didn't have one to ride], and then I made a drunk decision on a Friday night after six pints to commit one full week to make. I made a hardtail frame because I already had the parts to fit it, the foam core collapsed when curing it, and I was gutted. Paul from Easy Composites in Stoke provided all the materials to help me to commit to building this downhill bike and get the project moving. |
Vladimir said he basically didn't sleep for the last seven days, laying up the rear triangle over last weekend that took three days. He spent this week getting the linkages machined, (which still have a rough finish due to time constraints). Then his car broke down before the drive over, so he booked a flight and boarded four hours later, arriving late on Saturday night.
The front triangle took a whole week a few months ago, built when he last took a week's 'holiday.' In total, it took around 100 hours to laminate the complete frame. He had his layup planned, but as soon as it started, Vlad says he realised a few things were different to what he expected and ended up with around 30% more material than he planned to use, part of this was a belt and braces approach that was called for on this first bike to make sure it survives the following week shredding in Les Gets and Morzine.
| If this survives a week in Morzine, which it should do with the amount of carbon I used, I am going to hang it on the wall with all of the mud from this week. Then laminate a new one and ride that! |
The method he used is different to the way most bikes are made, but he wouldn't let on to too many secrets, yet. Basically a way to get around using a giant CNC-machined mold like production bikes use. Six machined epoxy master molds in a positive form, opposed to the negative shape and alloy mold, a more labor intensive but works out cheaper in the end.
Geometry and Suspension
Sequence Prototype Details:
Intended use: Downhill
Size: Medium
Travel: 200mm
Linkage: Dual link design
Wheel size: 27.5"
Reach: 440mm
Chainstay: 444-460mm
Wheelbase: 1250mm
Head Angle: 62.5º
BB Drop: 0mm
Headset: ZS56/56
Intended use: Downhill
Size: Medium
Travel: 200mm
Linkage: Dual link design
Wheel size: 27.5"
Reach: 440mm
Chainstay: 444-460mm
Wheelbase: 1250mm
Head Angle: 62.5º
BB Drop: 0mm
Headset: ZS56/56
Vlad thinks the geometry is pretty old school compared to modern standards, but I think it looks pretty spot-on for a medium sized bike. He had the linkage and geometry design locked in since 2012. There is 200mm of travel, with a few more in the longer 460mm chainstay length. He opted for the largest ZS56/56 headset to give some room for reach adjustment and +/-3º of the head angle using various cups.
A ZS56 headtube at this length can offer up to three degrees of head angle adjustment either way.
The chainstay can be adjusted between 444mm and 460mm with the flip chips, there are two sets of holes to receive the IS brake mount.
Vlad describes the dual link suspension design as quite progressive in the beginning up to 100mm, the leverage ratio drops from 3.4 to 2.5. After 100mm upto 200mm, it backs off gently up to 2.6 to work with the air shock. The anti-squat values start high at 250% at zero travel, but in the sag zone it is closer to 120/130%. After 100mm of travel, it drops of below 100% to avoid pedal kickback under big hits. There is a maximum of 5º kickback, then falls to relatively nothing. The anti-rise is fairly neutral starting at 120% dropping to 90%.
The upper link is machined in two parts, then bonded and bolted together.
The frame currently uses all steel hardware, and the axles pass through 12mm molded holes in the carbon. The bearings are all pressed into the linkages and all the threads are in the axles. The 6000 series EnduroMax bearings are standard and all the same size, so finding replacements should be easy.
Moving Forwards?
Vlad says he is not sure if he wants to start the brand, as he has so many other projects, but the molds are ready to use, and he says if 5-10 people really want one, he will start making them, so let him know what you think in the comments. There is still some optimization to do with the layup, and then stress testing and real-world testing, but for a first bike out of the mold it's impressive to behold, the finish looks better than many production bikes, only let down by the unfinished cable routing and quick release rear axle – but hey when you build something like this in your spare time you can't have it all when you want it. Vlad has no idea how much it would cost at the moment, but he says it would be incredibly difficult to sell it under £5000, absolute minimum. To make it in the UK, labor alone for one frame would cost £1000.
Vlad would like to thank Reap Bikes, Easy Composites for the frame build. And We Are One Composites and Swinnerton Cycles for helping with building the bike.
Author Info:
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I don’t think we can ever talk about proper production with this bike. I am definitely making a short run of prototypes which would be available to buy. This will give me the option to do minor layup tweaks for every different rider, and also keep the quality to the standard I want.
Cheers
"Started in 2011"
Cheers
Vladimir, after finalizing kinematics, when did you finalized frame shapes design? It is very timeless. Overall, the the frame is functionally simple, yet there is some stunning beauty incorporated. The admitted carbon top layer is beautiful.
What tool did you used for stress analysis?
Inventor/Fusion allows you to do that as well, but you must have the assembly constraints properly set-up. Otherwise it'll lead to wrong results. I don't know how Solidworks handles this.
Cheers, Vlad
@paulaston he moved to the UK, from where?
I know it's late but come on! I wanna know!
There was also the usual activities that everyone goes through, but I've always preferred to spend my time riding or modifying frames to change leverage ratios, geometry, stiffen up areas with a welded plate or two, which were usually ridden until their death..
And don't be too harsh on @paulaston ... I'm amazed how he managed to do this whole article in a such a short period of time!
Cheers
Pretty cool, you've come a long way - from welding reinforcements to a carbon prototype of your own design, respect!
Looking forward to seeing what comes out of the project!
Ah, that was meant to be a tongue and cheek poke, sorry if it can even across as hostile @paulaston
Help me understand how a suspensions leverage ratio increases through the travel?
"quite progressive in the beginning up to 100mm, the leverage ratio drops from 2.3 to 2.5. After 100mm upto 200mm, it backs off gently up to 2.6 to work with the air shock"
The quote above is stating the leverage ratio rises from 2.3 to 2.6 to 1 as you go through the travel meaning the leverage ratio is increasing which means the springrate and damping do less.
On the other hand a progressively valved shock means the higher the shaft speed the more damping force.
When i think of a progressive frame design I was led to believe the leverage ratio would digress to give the rider more support.
Where am I missing the boat?
It starts from 3.3 then drops down to 2.5 at 100mm of travel and after that gently goes up to 2.6 at 200mm
so many home built or low volume bikes look awkward in some way but this genuinely looks like it could have come from one of the major player quite easily.
Also if this is meant to be a medium it is nice to see a 440mm reach, i still think many frames are too short in the reach, at 5'8" it seems crazy that i should need a large or extra large in some cases to feel comfortable on the bike.
Respect is definitely due for this build!
Take yourself out for a pint and toast to you're excellent skills & perserverance!
On the other hand this head angle numbers are just a numbers. They will vary based on dynamic SAG /when bike is moving and dampers start controlling suspension/.
Serious question here. Is Vlad talking £5000 complete bike or frame only?
How tall is Vlad? Will there be sizes other than medium? 29er? LOL
And about the sizing, I’m 180cm tall, so 440 reach with a 50mm stem feels just right for me. There is always the option of extending the reach 8-10mm with cups so this can bring you to 450 reach.
After figuring out a layup that I’m happy with, another size for the front triangle can be made. All I need is 6-7people to commit and agree between each other on a preferred reach value, so I can recover the cost of making a 29er 480 or 490 reach front triangle mould. Rear triangle would stay the same.
Cheers
The frame only pricing is too rich my blood. I wish you success in your frame building adventures.
www.youtube.com/watch?v=UWSePEV88tw
Cheers
The reason I put saints is because I ran them on my previous bike and I wanted to see if my feet are gonna stay easier on the pedals or they are gonna be all over the place. It is just a test!