Super-light trials unicycle - How I became a “function first” weight weenie.

General
1

Over the last few months I’ve been experimenting with ways to lighten up my trials unicycle. I had set a (loose) goal of 10 pounds for the total weight of a trials unicycle that would still use a Profile hub.

Here’s how everything breaks down:

6061 aluminum frame - 448 grams
lower bearing holders - 80 grams
Salsa seat post clamp - 36 grams
6061 seat post - 122 grams
carbon fiber base - 210 grams
6061 aluminum handle - 95 grams
Yeti ODI grip - 46 grams
Miyata rear bumper - 52 grams
Roach nylon cover - 112 grams
air pillow - 210 grams
saddle hardware (Al and Ti) - 40 grams
Snafu pedals (sealed) - 686 grams
Profile wheel - 1980 grams
(hub, cranks, bearings, spokes, rim)
Monty tire - 976 grams
20" tube - 150 grams
rim strip - 22 grams

TOTAL - 5265 grams = 11.6 pounds

Noteworthy features:

6061 aluminum frame
- 460 mm (18”) seat tube (this looks and is ridiculously long, but I’m 6’7”)
- 25.4 mm (1”) I.D. seat tube
- 448 grams (under a pound)
- polished to a chrome like finish with “Mothers Mag and Aluminum Polish”

6061 aluminum handle
- identical geometry to “Reeder” handles available from Unicycle.com
- 95 grams (down from about 234 grams for a chromoly handle)

6061 aluminum seat post
- has Schwinn style seat plate
- 300 mm long
- 122 grams

Exotic fasteners

  • aluminum/titanium bolts, washers, and nuts
  • 82 grams (almost 3 oz.) lighter than steel

Other notes/thoughts:

I hadn’t realized how much my semi worn Monty tire weighed – over 2 lbs. Are there any other, lighter trials tires that still work well for unicycle trials? Onza? On a positive note, it does get lighter every time I ride it!

I should also mention how ridiculously tight the tire sits on the Alex rim. After breaking my composite bicycle tire levers it took silicone spray, big motorcycle tire levers, and some foul language to get it off.

The Profile wheel is definitely heavy, but in my eyes the only option for a bombproof trials setup.

There are lighter pedals than Snafus, but I prefer them over anything else I have tried for trials.

I hadn’t tried exotic fasteners on unicycles prior to this. I now have them on all my unicycles. I intend to test/ride them and see how they hold up in this application. These fasteners are, like anything, cheapest when purchased in bulk. If mine hold up and there is a demand for them, I may offer to purchase them in bulk and sell them close to at cost.

Don’t buy a digital scale unless you have the time to disassemble all your unicycles and see what each part weighs, as you will undoubtedly be compelled to do.

Summary:

My biggest fear as I was making the aluminum frames/handles and swapping out steel hardware was that the unicycle wouldn’t feel any different when ridden. I was definitely not let down here. The weight loss was immediately apparent; everything felt very quick, light, and responsive.

Some of the components are pushing the envelope, weight wise. Only time will tell if I have crossed over the “stupid-light” line.

Harper, pictures of the assembled unicycle as described will be coming in the next day or two. To hold you over, I will post pictures of a very similar, Al framed uni. I made this one for my cousin, Aaron Parker. The major differences are: a much shorter seat tube (frame weight = 390 grams), a steel seat post, and that the frame is unpolished.

al_uni.jpg
al_uni.jpg509×1294 95.8 KB

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Re: Super-light trials unicycle - How I became a “function first” weight weenie.

finally someone that can feel my pain.i have posted on this tire lever busting tightness before but no one belived me! a Monty tire and a Alex rim need serious tire levers.i also cussed a’pleanty.

3

How much weight would it add if you painted the frame or anodized the frame? :slight_smile:

Are you using carriage bolts in the seat or some other type of fastener?

4

The polished aluminum actually looks really nice. The frame in the picture had been cleaned up after welding, but at the time was not polished. I’m attaching a picture of a polished handle, though the picture doesn’t do it justice.

The fasteners are regular hex head cap screws. I didn’t look very hard, but I didn’t find any aluminum or titanium carriage bolts in the size (1/4"-20) I wanted.

polished_al_handle.jpg
polished_al_handle.jpg774×684 126 KB

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George-

Your aluminum welds are excellent. I trust one of the upcoming photos will show the bearing holder close up. There has been some recent discussion about Profile hubs having a not-so-hot bearing design or that they are loose on the axle. Did you do anything to try to address those problems (if those problems really exist)?

The seat post tube sounds just right rather than excessively long since you’re a guy of great altitude. It seems that having the joint where the seat post meets the tube at the highest possible point will give you the lightest, strongest frame.

Buying a digital scale is silly. Using one at Iowa State to weigh exotic unicycle parts makes perfect sense, though. What is the rough cost ratio for stainless steel versus titanium fasteners? Titanium is quickly coming down is cost.

There is no “stupid-light” line. Everything you do toward developing unicycle technology is on this side of the stupid line. Oh-oh … which side is “this” side?

6

One thing:

It’s NOT worth trying to lighten a trials uni by going to the Monty XL tire, which is significantly lighter than their regular trials tire. I had one for a while and had a lot of problems with pinch flats due to the thinner sidewalls, and the tire bead stretched to the point where the tire blew off the rim when I pumped it up.

-Kris.

7

George-

I calculate that you can save 24g by inflating the tire to 30psig Helium rather than 30psig Nitrogen. That REALLY lightens up the tire. You could get another 2g using Hydrogen but then there’s the extra danger of explosion.

I am now officially on the other side of the stupid line from you.

8

Oops

I REcalculate that you can save 12g by inflating the tire to 30psig Helium rather than 30psig Nitrogen. You could get another 1g using Hydrogen.

I am now both stupid AND officially on the other side of the stupid line from you.

9

Wanna dump grams?

(to paraphrase Grace):

Shave your head!

10

that frame looks really nice. is there any chance that they are going to be sold, or that you could make me one? How much would you charge? i wouldn’t need a handle, just the frame, but what a frame!

-Ryan

11

Looks great! I can hardly tell the handle is luminum, Could you also get a closeup on hte bearing holders? me dad wants to see how you made em.
Thanks

12

I had never experienced any bearing problems with my Profile, so I did not do anyting special here.

–

The seat tube (not post) should run all the way up to the bottom of the seat, like the Wyganowski freestyle frames. This means I can shave a few grams by cutting down my long 300 mm (12") seat post.

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Thanks for the tire tip, Kris.

–

Many more (detailed) photos should be up yet today

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I have heard of fixed gear track bicyclists filling their sew-up tires with helium. I don’t think the benefits outweigh the inconvenience of using He yet. Not only do you have to find helium to put in your tire, you have to find it more often because it leaks out faster!

I should mention that I kind of cheated; the mass I listed for the 20" tube was not the non-inflated mass.

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I’ll post some more information about the price/weight/strength of different fasteners in the next few days. For those of you who just can’t wait, http://www.mcmaster.com/ has a fairly decent selection.

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At this time I have no plans for production for two reasons:

I’m fairly inexperienced with aluminum. This was only a start; I dare say the best is yet to come. Also, I extensively test anything before I go to production. If these continue to hold up, I may consider it.

I would be happy to answer any questions about how the frames were made if someone out there wanted to make their own.

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About the bearing holders,

They’re machined from 2024-T4 aluminum shaft collars (from McMaster/MixMaster Carr).

Welding of 2024 is generally not recommended as the material loses its corrosion resistance when welded. A post welding heat treatment is required to restore this, though has not, and will not be done to my frame. I have instead crossed my fingers and hoped for the best.

If I was going to make the bearing holders the RIGHT WAY, I would machine them out of 6061. I’m lazy enough that I was willing to try the shaft collars, despite advice not to. For $6/ea you have 95% of your machining done for you, not a bad deal. If I ever make another frame, I’d probably start with some round, thick wall, 6061 tubing.

13

Have you tried drilling out the saddle the way bronson did? http://www.creativegeckos.com/pages/accessories.htm
The saddle on a trials is one of the least useful and heavier items. You might consider having a light plastic plate or something similar just for show.

14

Re: Super-light trials unicycle - How I became a “function first” weight weenie.

On Tue, 24 Dec 2002 13:09:10 -0600, gbarnes
<gbarnes.g6jro@timelimit.unicyclist.com> wrote:

>I should mention that I kind of cheated; the mass I listed for the 20"
>tube was not the non-inflated mass.

How is that cheating?

Klaas Bil

Left-handed people could not become knights because it was thought that they were descendants of the devil.

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Pictures are up at:

http://www.public.iastate.edu/~gbarnes/gb4/al_frame/al_uni.html

16

George-

A masterpiece. The seatpost tube looks like an integral part of the uni just like it’s supposed to and is seamless with the seatpost clamp up under the seat. Are you going to cut the seatpost down to 2-3 inches?

17

i was wondering, if i paid for materials, could i maybe help in the testing of the frame? i ride almost every day and could put it through all the stages, plus that frame looks amazing.

-Ryan

18

Harper and all, thanks for the praise and suggestions.

I will be cutting down the seatpost in the near future, this should drop about 75 grams.

I may be dropping another 288 grams by going to Wellgo’s magnesium pedals. Does anyone know how these hold up to pedal grabs on concrete and other trials abuse?

Ryan, I wish I could help you. I’m currently on internship and working 50-55 hour weeks there, and more than that in my shop. If thats all I was doing, I’d probably help you out, but I’m going back to Iowa State in January and I’m trying to get ready for that too. If you want I can send you my CAD models or if you talk hard enough some PDF format drawing files that you can take to your local welding/metal fab shop.

19

Magnesium wont hold up worth squat. I had azonic mags and they didnt even hold up for one trials ride with concrete grabs.

20

really?is it that bad?any one have pics of these failures?