KH36" Schlumpf review

I haven’t seen anyone post a review of the KH 36" Schlumpf yet so I thought I’d post one. My Schlumpf finally arrived after three months of to-ing and fro-ing.

I started off with a wheel, then had to wait for the frame shipment, and when that arrived, it was sent down to me when I was out of the country, and then when I finally got it all together, I stuck a seatpost into the frame and it got stuck, so I had to buy another frame after I got back in the country. Anyway, I finally received all the parts I needed to build it up on Thursday. Thanks UDC NZ!

The first thing I had to do was cut down the seatpost by about 1cm. The tubing is quite thick and took some effort to cut down. There is quite a long vertical slot for the clamped area, so no need to cut a longer slot.

This frame is tough. And very stiff. If anyone doubts how stiff, we wrestled with it, bashed it with a hammer, heated it with a paintstripper, and twisted it back and forths with a block of wood, all for over an hour to get the seatpost out of my first KH36" frame before giving up. Not just me, but some big guys at the bike shop had a go. The fork legs barely flexed through all this. No cracks or anything at the welds either.

Anyway, I didn’t have problems with the second KH 36" frame so I was able to finally ride it on Thursday.

I kitted it out with my usual GB4 handle, KH carbon seatbase and modified fusion saddle. And a few other of my favourite bits :stuck_out_tongue:

Handle: GB4
Seat: KH carbon base, modified fusion
Seatpost: Schlumpf aluminium
Frame: KH 36"
Hub: KH Schlumpf
Cranks: Quax aluminium 145mm
Pedals: Gusset Slim Jims
Spokes: UDC Stainless ?14Ga
Rim: Nimbus Stealth Pro
Tube: Coker 36"
Tyre: Nimbus Nightrider

The first ride I did was at the Wellington Velodrome. It’s a 333.33m velodrome with a banked edge. I couldn’t ride it on the banking so had to go along the flat inner part of the velodrome. Did a few laps and about 7secs faster than the 29" Schlumpf over a km. This thing definitely powers along on the flat! Went down to the Basin Reserve circuit after that to try a few laps of the course I used for my 24hr record. It took alot of effort rev it up to speed, but it was pretty bumpy and I was not able to wind it up at all. It seemed to handle the bumps better than the 29" Schlumpf, but there were so many potholes and glass and people to dodge that I gave up on the speed test.

Anyway, I went for my second ride today, and probably the first real test of the Schlumpf. It’s a ?30-something km circuit to Makara Beach and back which I regularly use for time trials. Not particularly hilly, but not as flat as RTL or Unicon 14 Marathon either. There is a short sharp climb up the road, followed by a gentle descent for a couple of km, then rolling all the way down to the beach. Lot’s of twisty turns and corners, so not a fast course. I’ve ridden this route a few thousand times (have been using it since high school), so it’s a good testing ground.

The first thing to note is that the Schlumpf is heavy! If you were to build one up, make sure you have the lightest wheelset available. It took some effort to accelerate out of corners and also to decelerate. I didn’t have brakes but that may be helpful I think.

Shifting was markedly better than the 29" Schlumpf. I think the new hubs engage more positively and solidly than the old road Schlumpf hub, but it’s more than that. Having ridden Tony Melton’s 36" Schlumpf (road hub), I found that shifted easier too. It’s probably more intuitive a jump between 1:1 and 1:1.5 mode in the 36" wheelsize than on the 29".

In fact, the problem was that the shifting was way too easy. I only had to think about shifting and I would find myself in the new gear. The other problem was that I had straight cranks, which scared me silly. I overtightened the shifter button on one side, and as a result, it’s stuck and I can’t adjust the buttons inwards. So I have this button sticking out very close to my ankle that I was petrified I would tap by accident.

The first part of my ride was spent wrestling with my Schlumph and trying to ride with my foot as far out of the pedal as possible. I didn’t get confident until I was half way to the ride and found that I was still alive (no accidental shifts). Once I hit the rolling section the Schlumpf really comes into it’s own.

It rides more like a bike than a unicycle. In fact, you need to ride it like a bike. I normally ride with a pretty low position, but I think to get full power into a schlumpf hub and lower your centre of gravity sufficiently, you need to have the exact same position as on a road bike. The GB4 was way too short. Ideally something like Pete Perons V-frame design should work well. I’m not a big fan of T-7 (too upright) and other extension bars that stick out all the way from the seatpost. I’m not an engineer, but something tells me that’s not a very good design :astonished:

The bike-like effect is basically down to the smoothness with which it rolls. This thing feels stable. The 29" Schlumpf is skittish and feels like it want’s to fly into the air everytime you hits a bump. You can go at a good speed on the 36" Schlumpf without feeling like you’re going fast. Not so on the 29" Schlumpf…if it feels like you’re going fast, it’s because you are.

To extend the bike comparison further…it rides like a very heavy bike. Like a DH mountainbike instead of a roadbike. It accelerates sluggishly, it decelerates with alot of effort. I had to really stand up off the pedals out of every corner in order to get up to speed again. However, if you can get enough momentum heading into a climb, you can crest over small rises quite easily.

The next thing is the frame. It worked great. It’s stiff, fairly light, and looked tidy. The only thing I didn’t like was the square crown design. It’s not as bad as the 1st and 2nd Gen Schlumpf frames, but like all square crown designs, if you are short, it can hit the back of your thighs or leg when you pedal. I only noticed it a couple of times, but probably not good for short people with fat or muscly thighs.

I hit the beach in a time of 42:00, which I was pretty happy with after spending half that distance experimenting and trying not to hit the shifter button by accident. By comparison, my Unguni Coker times are around 40-44min (at race speed), best ever road bike time 28.50. MTB times are about 30-32min.

The ride back was more pleasant. It was also rolling, but gently uphill overall, which had me less worried about the shifter button. I found the 145mm cranks ok in high gear up to about 5% gradients, after that I had to shift to the low gear. Unfortunately 145mm cranks on a Coker feels ridiculously long. So it was a case of either powering up in big gear, or plodding up in low gear. I think 125mm cranks might be better, as the 125mm cranks are a more useable low gear, but will probably need a few more rides before I make up my mind. The other option is to go super long, such as 160 or 170mm (like a bike), which might give you the leverage to get up just about anything in high gear. Singlespeed mountainbikers I know generally use 2:1 ratios and longer than usual 180-185mm cranks. Which I think would work out a similiar sort of gear to the 36" Schlumpf in 1:1.5 mode. So maybe the trick might be to use long cranks instead.

I got back from my ride in 1:28:59, which was slightly faster than my best Schlumpf 29" time of 1:29:18. Unguni Coker time 1:32:55 and roadbike time: 1hr08min. I think it’s definitely faster, but takes a lot of effort to ride compared to the 29"Schlumpf and 36" Unguni.

I’ll post an update once I’ve done some more riding. I think once I fix the shifter problem I’ll be a bit more confident at pushing this beast :stuck_out_tongue:

Thanks for the nice write up, Ken

Amen, brother. That big 36" tire makes for a stable ride. Lightening up a geared 29er is the intuitive thing to do but I think qualitatively much more energy is expended maintaining balance with the light and relatively fast wheel.

And a photo of the new KH:

A photo of the KH and the first KH 36" frame with a stuck seatpost

Kris Holm signatures everywhere!

No no no!!!

I think the stability of the wheel comes more from the diameter (and maybe the volume of the tyre), not the weight. But I would give anything to lighten the wheel by 50%. It is VERY heavy! THe first thing I’ll be doing as an upgrade is to go tubeless, followed by shaving the tyre.

Ken, its the hub which is the heavy component in your wheel. KH-schlumpf hubs are really heavy! And there ain’t that much you can do about that. (Maybe a Ti axle upgrade option to make 'em even more expensive??)

I can see that a GB4 handle would be too short on a Schlumpf 36", but I disagree with your reasoning as to why a longer handle would be better. I’ve found that the T7 is good precisely because you are sitting somewhat upright. Particularly in those situations where you hit a bump or get out of balance and suddenly have to pour on the power in order to stay on. Here having a T7 is good because you can haul up on it really hard, giving your legs more to push against to apply the required power. I can’t help thinking that if you were super stretched out (with a Dustin Schaap-style boom handle) that it would be really difficult to pull up sufficiently hard to stay in the balance. It seems hard to imagine that you’d have the same amount of leverage as on a T7. I’m not a bio-physicist so I could be wrong here. I also think the resulting crash with a long boom handle would involve more skin loss as you’d be in less of a position to run out of a crash.

While this is only one situation where handles are useful, any handle for a Schlumpf has gotta be strong enough to haul on, much more than ungeared coker handles, which can act more as extended hand-rests. That is, unless its on a dedicated track- and flat-roads only geared unicycle.

Thanks for the extensive review Ken.

I don’t think that superlong cranks is a good option. It might be good for uphills in high gear, but you would lose spinning speed on the flat and essentially defeat the purpose of the geared hub. The TGR with 170 mm in high gear is only 4.16, the same as with a fixed 36" with 110 mm cranks.

Yep, the hub is the heavy part. But so is the rest of the wheel. Of course, for a 36" wheel, less the hub, it’s pretty good. But that doesn’t mean it’s adequate. All current 36" wheels are heavy. It’s just that with a bigger gear, you notice it much more when trying to accelerate/decelerate.

Basically 36" wheels really need to drop their weight in half to be competitive with bikes. We’re still a few years behind in technology.

Absolutely disagree with you there. The times I have used a T7 handle, I have been tucked down, trying to go fast, but my hands are up against my chest. There is no way you can get leverage or have any kind of speed when your hands are cramped up with nowhere to move. Having a lower handle let’s you straigthen your hands a bit more. I’ve found a T7 is like riding a bike with the handlebar up against your chest. If they flipped upside down I would probably get one. Or the best mod I’ve seen is Scott Wiltons roadie style extensions on a T-7.

See my comment regarding V-frames. I think the extension handles are getting ridiculously long with nothing supporting them. It would be like building a bike with a missing down-tube and seat-tube.

BTW thanks heaps for sending down the frames and for building my wheelset. The wheel felt stiff and was perfectly true right out of the box, and also after much twisting with the frame #1 debacle.

I think it depends on how much power you can get in high gear also. I’m not very fit at the moment, and I found myself itching to spin faster the whole time. I never felt myself coming close to spinning out at any time. So, in my case, I think longer cranks would let me spin faster. OTOH, if I was fitter or a stronger rider, I’m sure the 145’s would be adequate. I need to do a bit more riding to make up my mind.

I forgot to post my overall impressions:
Speed *****
Quality ****
Build**** 1/2
Shifting ***1/2 (I’m sure this will improve in subsequent models, so not a full 5 stars even though it’s the best shifting hub and wheelsize at present)
Ease of use *** (The buttons are fiddly and I’m pretty sure I rounded one of the little bolts which is why my shifter is stuck)
Cost **** (it’s good value compared to what you’d pay for a top end bike)

I liked the ride, and certainly it will be great for some of the bike races and unicycle races I do. It’s probably the fastest road unicycle out there at present, until I get a V-frame built anyway :stuck_out_tongue:

It probably will never be my everyday unicycle or touring unicycle…the 36" wheel is far too big. I ride a 29" Unguni for that.

But if you already have every other unicycle, then you need to add this to your collection. It’s a must have.

You may be right, but I’ll tell you what happened in my case. I tightened the little bolt to much, upon which the tiny allen bit snapped. The tool, now lacking the narrow ‘top’, did hardly sink into the hex hole of the little bolt. It felt as if something was rounded but actually it wasn’t. Florian sent a replacement bit for free, and that worked. So, make sure your allen bit is unscathed.

It’s actually both. The inertia is in some way related to the mass of the wheel at the radius where the mass is located. If all of the mass were located at the wheel radius the moment of inertia, I, would just be the mass, m, times the square of the radius, r^2.


The moment of inertia increases quadratically with radius and linearly with mass. Realistically, mass also increases linearly with radius since the bigger the wheel gets the more rim and tire you have to add. All other things remaining equal, a wheel of twice the diameter will be twice the mass. Were this exactly true the moment of inertia could be expressed as a constant, k, times the cube of the radius.


A 36" wheel set with the same tire and rim density as a 29" wheel set would then have a moment of inertia that is 1.9 times as great although the diameter and mass are each only only 1.24 times as great. We both know that the rim and tire densities of a 36 are much greater than a 29 so the moment is that much larger.

Regardless, the 36" wheel makes for a qualitatively stable ride.

A little amonia could have broken that seat post free I bet.

Yes, but I think it’s not just the inertia that contributes to the ride. I think the bigger diameter let’s you roll over bumps easier, and the big volume tyre also helps. That, and the bigger gear/resistance gives it a more bike like effect. Not the fact that it’s a beast of a thing to wrestle with.

Jagur…good to see you back on the forums.

I know you tried many ways to get that seat post out. Did you try inserting a piece of steel tubing-maybe a tad smaller than the diameter of the seat post-and pound it out from the bottom?

The bottom is sealed.

Basically, I’m sure it can be gotten out. The next step would be to take it to an engineer to have the tube drilled out.

But I don’t have the time or patience for that. I wanted to ride it now!

I kinda figured the bottom was sealed, but couldn’t be routed or cut open without compromising the strength? Many seat tubes are “open” at the bottom, so I’m just wondering.

That sounds like a lot of work to save $200. But I probably would have if the frame had any sentimental value.

I just wanted to get on the road, so bought another frame instead.

Thanks Ken, I think that even with my ‘fangs’ mod, I’m still not far enough out most of the time. With my mod, I can get low enough but arms want to extend themselves and they tend to cramp up if the are bent like that for any sort of distance. I want to be 10-15cm farther out and I am small (with small arm length). I would have to disagree with Tony too, I feel like I have more torque, not less with my mod. In my opinion, my best handle would be like mine, with a 10cm extension that can be removed easily. My handlebars are quite comfy for cruising, but as soon as I start to go above 20kph I want to get farther out. The extension would be for racing and faster training rides, but I would remove it for touring, fun rides, etc. Is hitting the square frame really an issues for us vertically challenged people?