The world's second best unicycle seat (for tightwads)

Unicycles and Equipment
1

Inspired by Pete’s Flatfish, I wondered if it was possible to make a standard base flat. I have an old style Velo base which I’d taken apart in order to trim the foam and thought I’d have a go at flattening it by heating - it appeared to be a thermoplastic material which would bend when heated. I hope I’m not stealing your thunder here, Pete as your base is still lighter, stiffer and nicer, but this is a way for tightwads like me to make a flat seat.

Using a pan of boiling water I put one end of the base in at a time and then turned the base upside down and stood on it to flatten it. This resulted in a nice flat base - unfortunately I found that a lot of the flattening had happened in the area where the seatpost mounted, so that no longer fitted properly. So I reheated the base and found it has memory - it returned to much the same shape it was before.

So then I bolted a seatpost in place to retain the shape in that part of the seat and repeated the process. As I’d now got the steel reinforcing plate in place to hold the seatpost I used some wooden blocks to protect the floor - this also allowed me to flatten the base a little more as before the flattening had been stopped by the middle of the base hitting the floor (with it then springing back a little when I released the pressure). To flatten the nose I reversed the reinforcing plate so that the full force was going into the base, not the plate - its important that you flatten the back first in order to get the plate to fit.

A few important tips - the pan of water needs to be boiling and you need to leave the base in for a few minutes to heat through as the material doesn’t conduct heat that well and it seems it needs to be that hot in order to deform easily. You need to keep standing on the seat for several minutes as it takes a while for it to cool down and set in place. When mounting the seatpost you want to have it as far forwards as possible with the nose of the saddle as low as possible, as it’s harder to flatten the nose of the saddle than the rear in order to get it low enough - my saddle also bent around the front of where the seatpost was mounted, so if you mounted it further back you might not be able to get the nose any lower later. I found the sides flared out a bit during flattening, so used a vice to push them back in whilst the base was still warm (after the initial flattening had set).

I’ve not tried fixing the foam back on mine yet as I’m looking to get longer bolts for the front handle to use with a T-bar, but pushing the foam on by hand I seem to have got a similar profile to what people are getting with a Flatfish. It’s certainly a lot flatter than a standard saddle.

I’ve only tried with an older base so far, but I understand it is also possible to flatten a newer style base in the same way…

Here are some pics: the original base; with the reinforcing plate reversed to flatten the nose; in the pan of water; on the wooden blocks ready to stand on; the final flattened base.

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2

Nice job! Let us know how it works when foam and cover are added, and you’ve ridden it a few times.

3

I was going to wait until that point before posting, but it’s taking me a while so I thought maybe I should give some initial info - especially given that some people were already aware of what I was doing and I’m no longer alone in this project. Hoping to sort out my bolts tomorrow and maybe get foam on with a ride in the next few days.

I should probably mention that this is from an old Nimbus Gel saddle, so I have the foam which seems to be recommended.

4

Yeah I used the nimby gel foam I took from my oregon and put it on my flatfish for my century ride. Surprisingly, it wasn’t noticeably any more comfortable than my standard fusion freeride saddle, which I used on my last century. Maybe it was the foam, and maybe not, but it was a very good, solid fit. I was going to use the freeride foam but I couldn’t keep it from going down at the back, even with a foam wedge.

5

that’s an interesting idea!~

I didn’t realise it could be remoulded so easily.

Do you think it can be bent downwards?

I’ve been toying with the idea of an inversion seat for a while. Not so much a reverse curve, but more flat with the nose section angled downwards.

6

I was a non believer, but when Aracer suggested boil the bases, the gears started turning…

I also started with a Velo base from a Nimbus Gel and had the same issues with the seat post mounting area losing it’s curve. The Velo base is surprisingly easy to flatten and the only distortion came with some inward buckling on the sides, between the seat post mount and the nose. This is a good base to start with, but I wanted a base that was more substantial, so for round two I used a new KH Freeride Base.

After a number of boilings and “floor flattenings”, I clamped the seat base in my table vice and let it cool:

The seat base is not 100% flat, but this is a good thing because the rear of the seat is just raised enough that I didn’t need to add a wedge of foam to make the seat pad flat. Also notice that I cut down the sides for a lower profile; and cuz it looks cool:

I decided to try cutting down the Freeride foam on top, thinning the channel so it was the same depth through the middle of the seat (stock FR foam is progressively deeper toward the middle of the seat). I ended up cutting down the rear portion of seat, these pictures were at an intermediate step:


Here’s the steel plate, the top plate is from the Velo (uses carriage bolts), the bottom plate with welded in T Nuts is from the KH Freeride. This picture was taken before I bent it flat to match the seat base.

In order to get the inner steel plate with the welded T Nuts to line up in the base holes, I had to do some creative dremmeling, but it worked out fine:

And the final product mounted on my 36er:

And here’s the flattened KH Freeride compared to a stock KH Freeride:

The only thing I’d do differently next time is to use a Nimbus foam pad or similar, as I think the KH Freeride foam is too bulky and the channel is not necessary once you flatten the base.

Oh, and Aracer, you need a bigger pot! :stuck_out_tongue:

7

I wanted to do this myself but I figured if I ever did I would wait for someone else to attempt it to see how well it goes. I don’t think I’ll bother for a while, but when the time comes I might.

8

I’m just wondering how long it’ll be before we can buy flat saddles that don’t need to be CF and shipped all the way from New Zealand. I’d love one but it’s an expense I just can’t justify.

9

That’s the whole point of this thread - most people capable of transplanting the foam and cover from one base to another ought to also be capable of flattening their own base. No expense at all involved (apart from the cost of gas/electric for heating the water) in getting a flat seat this way. Of course it’s still harder than just buying a flat seat, but I think those are some way off yet (there’s definitely a gap in the market for somebody to create specific foam for a flat base and sell complete saddles, but I doubt they’d be that cheap even using modified bases and I’m pretty sure the market is too small to build a business around!)

10

So do you have a issue with saddle flex with the ghetto flat seats?

11

As mentioned above, I’ve not ridden mine yet (and won’t now finish building for a few days as I’ve not been able to get bolts today because I’m stuck at home with sick kids). So I’ll defer to Ben for practical experience. However the structure and the amount of material is no different from a standard saddle base, so there should be no difference in stiffness. The heating and bending don’t affect the material properties (Young’s Modulus aka stiffness) of the plastic, nor do they make a significant difference to the thickness of the plastic.

Clearly it’s not going to be as stiff as a Flatfish though, so you’ll need to use a reinforcing plate with a T-bar.

12

I will be using mine for urban and trials so i was worried about having a super flexy saddle

13

I can’t do a direct comparison because my other Freeride seat is not mounted, but when I hop around on my ghetto seat it is fairly stiff, and that’s with one of my handles which put a lot of torque on the seat.

I think all seats flex, mostly at the leading edge of the seat post plate. I don’t know that this could be fixed nor do I think it needs to be fixed. A certain amount of flex prevents breakage and I don’t have enough flex in either the Flatfish or the ghetto seat to be noticeable when riding.

The new KH seat base is much stiffer when flattened vs the older Velo.

15

You say the plastic has positional memory? Be careful riding if the temperature is hot enough, the seat might pop back into original position without warning! Yikes, that would pinch. :astonished:

16

When the seat sprang back, the steel plate had not been bent and added back in. Also, if you’re getting that hot down there, you have other issues to worry about. :roll_eyes:

17

We’re talking about heating to over 200F here - as suggested if your saddle is getting anywhere near that hot you have other things to worry about!

18

Use oil vs water. You can get it a lot hotter without it boiling. I use this method when I make fishing lures :wink:

19

No need - boiling water is plenty hot enough (and a lot safer!)

20

water is not only safer than Oil, it is cheaper and I’m sure it is easier to get off once you are done.

21

Will boiling the plastic release any toxic fumes?