Micro Machines: Tiny crank and tiny wheel Megathread

[MrHydra]

So lately I’ve been pondering about getting a pair of those 45 mm cranks mentioned in the first post of this thread… However, I’ve been perusing some alternatives before going with those being they’re not exactly a standard square taper crank (and I don’t have access to a 3D printer unfortunately so I’d have to fashion a shim some other way)

I’ve just found out about crank arm shorteners (example here) which might offer the benefit of having a smaller effective crank arm while also using standard square taper cranks. According to the description from the example I listed, Fit Kit Systems, it can shorten the crank length by 24mm, 41mm, 59mm, and 76mm(!).

I’m just thinking wildly in my head… I have a few sets of short-ish square taper cranks lying around, 90mm being the shortest…

Imagine an effective crank length of 14mm…

(Not that it would be practical… But it could be possible )

Now I haven’t looked into it too seriously, mostly because the thought of dropping $175 on some adapters for goofy crank length shenanigans doesn’t scream “reasonable decision”. But it looks like there are other companies that make similar products, so I’ll keep looking for now. What do y’all think?

[Wheelou]

Hm, might be cheaper to look for some (used) taps to shorten the crank arms yourself. Or find an LBS that can do the tapping.

[PedalSprell]

@MrHydra

Imagine an effective crank length of 14mm…

(Not that it would be practical… But it could be possible )

Well, it is really uncanny that you should mention that. Back to that later. Lets “mount” some 14 m cranks on my sons 12" unicycle:

Notice my white “3D-printed” 14 mm cranks there. Now, do you still think riding this could be possible?

Lets procede with doing the math. So the actual Gain Ratio for 12"/14mm will be:

12.7*12/14 = 10.88

For reference, riding a 36-er with 75 mm cranks is 6.10. Now reflect on this for a minute. Do you still think riding 14 mm cranks could be possible?

Now, lets do some more math:

12,7*36/45 = 10.16

45 mm cranks. On a 36-er. Do you still think riding 14 mm cranks, even on a 12" unicycle could be possible?

Well, to your great fortune, @MrHydra, this happens to be the Tiny crank and tiny wheel Megathread and I share your profound belief that this could indeed be posible! I have therefore invited Norways two best freemounters, who happen to have ridden seveal miles on 36"/75 mm, over on this very Saturday to do some shenanigans on my 16"/45mm Micromachine.

However, I have actually mounted the 45s on my other cottorless unicycle:

Notice my “3D-Printed” 14 mm cranks on the 12" unicycle and compare the visual wheel to crank length ratios in the picture. Both actually have a similar gain ratio, as stated earlier:

12.7x36/45 = 10.16
12.7x12/14 = 10.88

Since @ruari (also an expert on freemounting and ridiculously short cranks, and responsible for this whole 45 mm madness) is also coming on Saturday, I have also made some minor adjustments just for him. Your dream is about to come true:

Is riding a 36-er with 45 mm cranks even possible? Thusly making 14 mm a sensible choice? Stay tuned!

[MrHydra]

Referencing this handy chart made by @saskatchewanian,

A gain ratio of 10+ is firmly in You just don’t want to go there territory I’m interested to hear about how it goes with the tiny crank 36er. 45mm on a 36er sounds pretty mad, considering the rider’s legs will probably need the force of a hydraulic press to get going!

[PedalSprell]

Yeah, I agree! And you have to stay in balance as well somehow. But these guys have both feet firmly placed in “you don’t want to go there” territory already, so who knows? One of them even did a 144 km ride on 36/75mm.

[Eric_aus_Chemnitz]

Wasn’t there a guy competing at the Europe Marathon with a 36er with 64mm cranks? His name was Edmund and he was from Poland. I think, he competed in the halfmarathon and there was a small girl on her 20" who was faster than he was. If I remember right, he had to dismount for almost every light uphill section. Some of us tried his uni (not me) and could only ride it with for a few meters with a helping hand. @vookash and @makym, you knew the guy, right?

[vookash]

Hej, I’ve checked with Edmund and he hasn’t gone that low. On 36" he has 64, 70 and 90mm setups and he has 29" with 50mm.
And yes, it was highly inefficient on the Europamarathon

[pierrox]

@Sexy

Me: OMG it’s a complete cheat, this is not a tiny wheel!
Me 2 minutes later: where are my 75mm cranks??? they could fit my 19" trial I barely use.

[pierrox]

@PedalSprell

Where do you get disc brake ready 20" frames?

Looks like a 24" frame, but I could be wrong.

[PedalSprell]

@pierrox

Looks like a 24" frame, but I could be wrong

I think it is smaller than a 24" frame, but I could be wrong as well. Since the wheel diameter was never stated, I did a estimation of the crank-to-wheel ratio from the pictures. I concluded that it must be a 20" wheel and not a 24" wheel. And … And… Now I totally lost my track because:

I just realized I could build a 20" wheel, and mount it in my 24" frame! And fit the frame with my 3D printed brake mounts, which can be moved up and down on the frame depending on the wheel I am using! With a pair of 75s. Now THAT would be AWESOME!

[ruari]

@PedalSprell

As far as I can tell, this must be a 20" wheel. Isn’t this the exact frame you were riding with 75s, @ruari ?

If it is a 20 inch frame then yes I would assume so.

@PedalSprell

Where do you get disc brake ready 20" frames? M4O?

My daughter’s uni (which is what I was using with the 75mm cranks) is a 20 inch and has a disc tab. It is URC Muni XS frame, URC being the sub-brand of M4O.

Video of your latest ride

So @UniMyra is of the opinion that a grown man (closing on 50), cycling along at speed on a 20″ pink unicycle might be preventing some bystanders from taking us unicyclists seriously. Personally I think the only serious thing here is my obvious speed. P.S. This is one of my kids’ unicycles. Since they rarely use it, I felt the need to give it a bit of attention. It is actually surprising the pace of these little unis actually… once you mount some suitable short crank…

[Sexy]

Yes for clarification it is a 20". URC XS frame, it came as a stock 20" x 4.0 build. This is my current balance between control and speed. Once it starts rolling you get enough energy to clear most obstacles I find. The mtb tire also gives very good grip at speed.

It has taken a few years of practice to tame but it a portable way to get around the city and is lovely as a travel uni.

I have a trip to the Grand Canyon soon, and will have my actual muni with me.

If anyone else has good health insurance, I do have an extra set of 75mm isis cranks that are sane up to a 26" but extremely fun on biger wheels.

[Sexy]

So this is also due to me being mostly leg. This uni has a 400mm seatpost.

[Sexy]

@PedalSprell

What kind of handlebar and seat attachment is it you use?
Can you ride this with a two hand grip?

So the handlebar is from Jakob, specifically his mount, and then just a normal straight 22.2 mm handlebar peice of pipe. Lightweight, compact, natural hand positioning. You can do two handed, it just has a bit of overlap.

I have been using it on both my unis (see older posts for my 700c I was left unsupervised with a credit card build).

[pierrox]

@Sexy

it is a 20". URC XS frame, it came as a stock 20" x 4.0 build.

Makes sense and explains why the clearance above the tire is quite big. On most my 20" frames, I can’t fit more than a 2.1" tire! So it did look like a 24" frame on the photo.

[PedalSprell]

So the Cranky Crew has finally gotten together to really try out 45 mm cranks.

One of us even arrived on 45s

@ruari could finally try his tiny cranks with their full potential

Well, it might just happen that we have reached some kind of limit.

Well, I have developed a special arm-swing for just this occasion. Maybe that will do the trick:

Luckily the Cranky Crew can boast Norways very best and craziest on tiny cranks. The true master of 45s:

I am so happy right now. This even brought a tear to Ruarís eye. The world is ready for 45 mm cranks. Finally.

“I hearby knight you Sir Cranky. I bestow upon you these 75 mm cranks. Use them wisely.”

Or simply opt out, I guess

[MrHydra]

That brief ride on the 45s was crazy It looked like the legs were just barely moving!

[Wheelou]

Unicyclists are a pretty cool breed…

[ruari]

Your videos are HEVC (H.265) encoded. That might be a problem for some people depending on browser and OS as this is a patented codec and requires a license to decode, which costs money per user. The cost of which can be higher than the OS (for a free OS like Linux) or browser maker makes per user.

For those that struggle to play, I re-encoded the videos as webm.

@PedalSprell

One of us even arrived on 45s

@PedalSprell

@ruari could finally try his tiny cranks with their full potential

@PedalSprell

Well, it might just happen that we have reached some kind of limit.

@PedalSprell

Well, I have developed a special arm-swing for just this occasion. Maybe that will do the trick:

@PedalSprell

Luckily the Cranky Crew can boast Norways very best and craziest on tiny cranks. The true master of 45s:

[MrImpossible]

@ruari

Your videos are HEVC (H.265) encoded. That might be a problem for some people depending on browser and OS as this is a patented codec and requires a license to decode, which costs money per user.

Thanks - the originals didn’t play for me with Firefox on Windows 11.