The new unibokk retro saddle

This is my latest project with regard to achieving a more sustainable and comfortable riding posture for riding long distances.

The saddle is the KH Zero saddle with the post bolt system relocated so that saddle is shifted further back on the seat post.

The handle bar is extended to it’s max position. But with the saddle moved
back, the sitting length is more extended than would be possible with the standard saddle position. :D:D

Also, moving the saddle back makes for a more balanced distribution of body weight. I’ve been riding on the beach with this set up and it’s rather like cycling a b*ke .

It feels really balanced and comfortable.


Good work, though… Am I the only one that immediately imagine it breaking at the first occasion if you go down a curb or any drop ?

@ uniDreamerFR

Hello unidreamer.

This set up is as firm as the normal KH zero set up. I was expecting some flex but have experienced none. I’ve cycled over some bumpy terrain and done some UPDs on tarmac with no problems.

This set up is mainly for road riding. I wont be doing any high jumps etc :astonished:

This is my answer to finding a more comfortable posture for riding long distances on roads and other smooth terrain.

Near where I live there is a long coastal cycle path that goes on for miles, which is where I’ll be cycling.

I wouldn’t cycle my uni on busy roads because I think it’s too dangerous.

I would love to see either Kris or Roger develop something for the long riders and road racers out there.:stuck_out_tongue:

Roger does some high speed road racing. Maybe he will read this and be prompted to put his genius to work.

Stable, comfortable, streamlined posture…

C’mon Roger. Think about it.

I should add.

I narrowed the internal rotating block so as not to compromise the strength of the saddle structure too much. I made other minor adjustments to ensure that the saddle set up is firm and strong :slight_smile:

I hate to be the naysaying engineer guy, but it really doesn’t matter what path the connection from seatpost to frame takes. The most sensible path is the direct one from the center of your weight to the axle, since that’s the shortest and strongest.

But you can attach the seatpost anywhere on the saddle, and take any old path to the axle, and nothing else would change - not the saddle position, not your riding position, nothing.

I made a little photoshop of your picture, and moved the seatpost to the other end of the saddle. What I’m saying is that if I could do this switch underneath you, with you in the saddle, you would never notice anything. Maybe I should photoshop a rider into the photo, too!

seat position.JPG

For a long term durability, because of the geometry of this setting, I would add a line to secure it, I mean the hypotenuse of the imaginary square triangle joining the point under the back side of the seat to the low part of the seat post, don’t know if i’m clear.
Cause a good part of your body weight is on the back of the seat I guess, and even if it is well fixed, it seems to me that it will bend, eventually.

I was obviously speaking about the op pic by the way.

Mr impossible: good point, I thing you are right, you can also take the example of the second version of the nimbus nightfox that has an offset saddle, also the hachtet.

I’ve debated the dynamics of this in the "unibokk Long rider thread.

I can only say that this set up feels more stable and comfortable than having the length of everything stretching out in front of the seat post.:slight_smile:

Your photo shopped version is interesting. It reminds me of the hatchet uni.

Yep. You make a good point there. It’s something I considered and may yet do.:slight_smile:

Exactly what I was thinking seeing this - in fact moving the saddle backwards and forwards on the seatpost results in exactly the same effect as rotating it on the seatpost. Given the handlebar is attached to the front of the saddle in the normal place, then exactly the same relationship between the unicycle, saddle and handlebar could be achieved with the seatpost in the usual place. Any perceived difference is purely imaginary.

…hmm, and having found the long rider thread, it appears we’ve already had this discussion

Ok, let me give a simple explanation,

The handle bar extension (boom) generates torque, (i.e. leverage).

The further it extends out from the seat post the more torque/leverage, it generates, just like a long crank on it’s axle.

This extra torque/ leverage, puts considerable stress on my arms as I have to react to bumps and rolls etc.

However, by shifting the saddle backwards I am effectively shortening the front boom, thus reducing the torque effect on my arms, whilst still allowing a long riding position.

I suggest you guys make a long rider with the saddle shifted back and try it for yourselves. :smiley:

The torque works the other way - a longer handle bar means your arms have more leverage on the bumps, not the other way around. It’s more stable with a longer bar.

It works the same way that longer cranks give you more leverage on the wheel, and shorter cranks give the wheel more leverage on you.

And I don’t understand how moving the seatpost connection affects how long a bar extension you use. You can choose whatever handlebar length you want, no matter where you decide to attach your seat.

I mean, it’s a cool project, and it’s great that you ended up with something you like, but it’s not working out for the reasons you think it is.

You should check out Turtle’s V unicycle for comparison - he ends up with a similar extended riding position using almost the opposite concept, by moving the seatpost backwards instead of forwards.

If we consider saddle and handle as one solid unit, the seat post should be in the following position for minimum flex:
The ration of the distance between seatpost and seat to the distance between the seatpost to the handle should be the reverse of the ration of the weight you put on the saddle to the weight you put on the handle.

PS: Nice Project! Could you please post a detail pic of how you attached the seat to the post?

Position of Seatpost.jpg

@ MrImpossible

When I began using handlebars. I learnt on a grassy trail. I found that with every bump my arms were being thrown left and right and I couldn’t control it.

So I decided to shorten the handlebars and found that my arms weren’t being thrown about as much.

Over time I moved onto the cycle path using the handlebars at full length.

But even now if I’m going on rough terrain, I use much shorter handlebars.

I have checked out Turtles V frame before and just like my idea the V frame effectively shifts the saddle back, aft of the axle. This allows the rider to lean forward more whilst his body’s centre of gravity is more directly over where the axle is, resulting in the rider having to make less, correction of balance, moves.

Moving the seat post connection doesn’t alter the overall length but it increases the length aft of the seat post.

@ Eric aus Chemnitz

Thanks Eric. I’ve just been reading your post. Your explanation sounds good to me. :slight_smile:

I will post some detailed photos soon.

Yes, definitely interesting. As has been pointed out, it is the relative position that is important and not where it is connected… but I do like this. There are quite a few broken zero saddles about and this would bring them back in to use. Also… you could make the saddle so it does actually flex! I think that could work well with the handle being solid and a little vertical flex on the saddle. What do you think?

One thing I am working on is looking at cycling position created during a dynamic fitting for a bike frame. This data, along with a calculation on the bodies centre of mass (my guess is that this should be directly above the hub) should produce some interesting data. I will feed here when I have some diagrams.


Which is the only difference the seatpost position makes, and the only advantage of moving it - yet flex isn’t something being mentioned by unibokk as an issue. The advantages he is mentioning are all achieved simply by tilting the saddle forwards with a normal seatpost position and then rotating the whole unicycle bckwards around the hub.

Thanks Roger :smiley:

Yep, vertical flex sounds great. It may pave the way for lighter and less bulky tyres and allow for higher psi tyres whilst still comfortable on the lower back.

I have some photos of how I assembled the Retro. I’ll try and post them today.

Hello Aracer

I am not an engineer, I am just an enthusiast who is always searching for improvement, especially for long distance riding.

But, as always I do enjoy debating with you.

Thanks for your contribution.