Coker V-Frame

It finally rained in Seattle this weekend, so I was able to finish welding up my first Coker frame project. This is a modified Hunter, adding a vertical front support tube, at the top of which is a bike stem and my regular road handlebars. As you can see, I prefer my bars way out in front. I wasn’t quite sure where to attach the 2 joining tubes, so I put them at different angles to see how it would look. The smaller diameter was all that was neede to provide adequate strength. But next time I’ll try parallel joiners. I used TIG brazing with silicon rod on 4130 tubing.
Anyway, here it is, the paint is still drying…


Wow, looks very interesting. I would think the handles are too low, but I can’t wait to hear how it works for you.


Pete likes the low handles to give him a more aero profile. Here’s a picture of his Hunter and handlebar setup before the operation: Pete’s Hunter

It’s definitely a different setup than what most other riders use. I should have gotten a picture of Pete riding it to show the body position and the riding profile.

Cool new frame! I think this is a glimpse at the future of road unicycles. The handlebars may look low, but compare to a road bike. The seat is usually much higher than the normal hand position.

The only problem with such an aero position on a unicycle is what happens when you lose control? I worry about this in my much less aero position on my Coker. You will have a harder time running out of any crash in that position.

But the frame looks really nice.

my groin groans at what could happen to the grawn.

I was just wondering if a saddle more like one from a bike would work better? My legs are quite thick (too much squatting :)) and I tend to get chafing from unicycle saddles. Just thinking about something like a road bike that have really thin saddles.

I think so. A unicycle saddle is definitely not intended for the tuck position of a road bike. Expect chafing to be more of an issue. And what Jagur said. You can deal with this to a certain point by tilting the saddle forward, but if you have a good handlebar setup you may not need a unicycle seat any more.

My ultimate road unicycle would still have a handle in front of the seat, for upright riding. You would use this for starting and stopping, riding through crowds, and over questionable surfaces. But this handle would not need to be part of, or attached to, the seat, allowing for a smaller, lighter seat. With a body-friendly handlebar setup, a good portion of your weight would be supported on the handlebars, leaving less of it on the seat (like a bike). So you wouldn’t need as much seat for that either.

Scot Cooper has a bike seat on his Coker. There are pictures of his Coker and bike seat in some of Nathan’s albums.
Album one Look at the Twin Peaks with Market Street photo
Album two Look at the first and third photo

If you use a bike seat you’re going to need some sort of handle setup. And Scot has mentioned that the bike seat makes it more difficult to climb steep hills than with a standard unicycle seat.

Kris mentioned at the CA Muni Weekend that the KH seat is going to be made with a narrower front to help reduce leg rubbing and chafing. I think this change is in the new seat with the Fusion seat cover. If not, the change will be in the next version of the saddle.

My general understanding was that bike seats do not provide enough control. I think (maybe mistaken here?) that Ed Mosiman tried them and ultimately rejected the idea?? But the only way to find out is to try a few different seat styles, so I think I will. There’s no doubt that the connection with the bars is an altogether different dynamic than just riding upright.

Ed Mosiman, and many of the other riders in his area, used downhill bike saddles. Downhill bike saddles are bigger and than standard bike saddles. Some more info about his seats is here on his web page. Note that I don’t think he is making unicycles any more (at least for now).

I tried his unicycle with a DH bike seat and it is something that definitely feels different. I only tried it for one very very quick ride so I can’t comment on comfort. But it’s definitely something that you would have to get used to if you switch to that type of seat.

Others that I know of that have tried bike seats:

Several years ago, Lloyd Tabb tried a DH seat for Muni and ended up not liking it.

Scot Cooper still sometimes uses a women’s road saddle on his Hunter36 for touring. But he can only do this because he steers with an exotic handle extension - otherwise there is not enough control. I don’t think it would work for him without the handle.

The search for the perfect unicycle seat goes on…


Adding this technology to an already expensive type of unicycle will make it an expensive tool in a unicyclists arsenal. Though i think it may very well be worth it. Good idea and hopefully we’ll be seeing this type of design pop up in the near future for purchase.

As for bike seats, I concur that they are only going to be viable in situations where you have one or more handle positions on the front of the unicycle. Without a handlebar system, you will not like a bike seat!

I rode this coker for a half-hour today, and I really like it. I do prefer a somewhat bent riding position for road, so this fills the bill. While this frame places the bars the most forward I’ve ever tried, on the level and uphills I still had my hands at the front of the bars. On downhills (I went down the long SR-520 hill in Redmond) I tended to move my hands back a bit, but still comfortable within the fore/aft grip range of this bar position.
On my previous version (see John’s pic above), I used an extended stoker stem to mount the bars, which was OK in terms of feel, but not super-rigid. With this V-frame, the feedback from the bars was more direct and instantaneous, and I needed less independent correction input with my arms. I felt I was using my whole body more as a unit to control the wheel. So bottom line is that I’m very pleased with the design and feel of this frame.

I’m already working on the next model, which will have an even wider “V”, so that I can mount the bars directly on top of the front upright tube (we need a name for this new tube), thereby eliminating the bike stem part. I plan to use a shortened recumbent-type straight riser stem that will insert into the front upright tube, using the same seatclamp as with the seatpost on the rear seat tube. So the bars can still be adjusted up & down.

Also thinking of an aluminum frame of this design, to lighten it up more and presumable make it more maneuverable…I would think all these coker frames would benefit from light weight just like bicycle frames.

I like the design. Do you have a top view of that thing? I’m curious to see what the handle looks like from the top.


So far all my handlebar designs have been cut & bolted together from bike parts (like bars & bar-ends). Tip: don’t use Profile Design aero bridges as the “first-strike” part at the front of the bars, they shatter on the first hit. This one’s a Syntace. Here’s a view from higher up:

Thanks, that pic really helped. I like the way it looks, though (I think) it would look a lot better if there were only one of the skinny tubes connecting the front and rear part of the V. Another thing that might look cool is if you had two connecting pipes, but had them side-by-side at the level of the wheel (or just below).

Nice work,

For frame shape, I’m thinking in terms of the rear triangle of a bicycle frame. Same basic idea. From there, the goal would be to eliminate excess material or complexity (and weight) from the design. This would make it easier to build. There could be height adjustments for both seat and handlebars at each end. Then you could devise a system to make the handlebars adjustable to the front and rear, to adjust for rider size.

For the next model, I’m gonna set the spacing between the vertical tubes at 8", measured at the tire top. That should allow me to mount my bars directly on top of the front tube. I’m gonna cut both the front & rear tubes at the same height, with the front carrying a sliding aluminum handlebar clamp. This first model has the upright spacing set at 5" at the tire top.

John, I love the idea of a fully-adjustable frame! Another idea is to allow the spacing between the vertical tubes to be adjusted by splitting the horizontal tube, with one half sliding inside the other half, and a std. seat tube clamp to set it. But what to do with the top bearing holders to allow the front hoop to rotate slightly to follow that spacing adjustment?

Daino, I used 2 of the skinny horizontal tubes here because I felt that one tube, even a big one, would have been insufficient to prevent flex. I’m having Hunter build another frame right now for my geared coker (more on that later), using for the horizontal tubes the same tubing as the hoops. But still 2 horizontal connectors.

I’m also researching and selecting aluminum tubing for yet another model.


Here’s the updated V-frame (the “Red Menace”), which has an even more responsive but pleasingly stable ride! Yesterday I cut off the 2 horizontal tubes, and TIG-brazed on longer ones (this time parallel) to extend the V separation to 8", measured at the top of the tire.