Wow, it is so great to see power numbers to compare with! If you are interested, here is some rough analysis I did with your numbers.
Road Climb estimates
I estimated your CRR 0.005, and CDA 0.42, to match up your climbing road race power and times.
For me on a 29er, I’m estimateing 0.004 CRR and CDA 0.40 to match my power and time.
Theoretical 36" Tire Performance
For fun, assuming the CRR/CDA are correct, and ther ewas skinny and thin 36 tire with similar CRR and CDA as my 29er, you would be more than 1 minute faster!
Of course, with even slight weight inaccuracies for each of us, such as +/-0.5kg for water, sweat, clothing, etc, that could be +/- 20 seconds difference and affect the CRR/CDA estimates…
I think the 36er is the best choice at your riding level though. Going to a 29er for the better tire and weight probably isn’t worth it since 51:00 would be about 130rpm and likely impact your power output. Though, you spin that fast for the 10k/marathon so maybe…??
Marathon
Using the same numbers for your marathon results, would give a schlumpf efficiency of 87% which seems way too low
Conclusion
All of these are pretty rough guesses since we don’t know the exact weight, speed variations throughout the races, etc. But, CDA around 0.40-0.46 seems normal, so I think the power data is quite accurate and a good reference. Really glad to see your power meter working, and the numbers seem good. I always wonder if mine is working normally or if something might be off, but this is reassuring!
I found out my 3d printed platform adaptors had cracked after getting home.
They were making noises especially after riding the cross country course, but I thought it was just normal play in the fit.
The small rectangular blue/black pieces are pushed into the main plastic piece to keep it from sliding out.
However, around the rectangular hole, there are cracks on both pedals.
The left side (with blue part) has slid out a few mm.
The right side (with black part) has a thin visible crack, but the main piece has not slid out significantly yet.
Thank you for your analyses!
I’m not familiar enough with all these numbers, but I’m amazed at the total power difference between our 2 performances.
That’s a lot! I think that to improve the performance on the road, you would need a 36" tire with a width of 2" (I don’t think it should be narrower) and really slick.
This is off topic, but what rim and tire do you use? I’m planning to build a new G29 to travel in the Pyrenees with a hooked 25mm carbon gravel rim and a schwalbe g one speed 28*2" tire mounted in tubeless.
I don’t know if we can use my 10k and marathon rpm as a reference. I develop much less power than on the hill race.
In training, I could see that in my favorite segment (2.5km with a 1% slope), the days I had a more favorable wind (and was going faster), my power on the segment was lower. I would have to make a graph with the power and the cadence on this segment.
I would have imagined that at this speed, there was more W for rolling resistance and less for aeropower…
In your calculations, the weight has no influence on the 10km and the marathon? Maybe it does a little? My total weight on the marathon is at least 4kg heavier than during the climbing race, and a little less than 3kg for the 10km. I had a waterbag of about 1kg for the marathon and the hill race, I had planned 1L and 0.75L respectively, and I didn’t even drink half of it on the 2 races. And the weight difference between my 2 unicycles is 4kg (9.5 for the G36 & 5.5 for the 36").
Otherwise the fact that I didn’t have a brake for the hill race must have saved some W.
Loving your nerd discussions guys! Keep it up, really fascinating stuff.
My replacement SRM X Power Pedals have been sent to me, but not riding until October I don’t think due to school commitments.
After that I will have time to do whatever I want. I very much want to record a hockey game in real time which means I will get both positive and negative torque and can calculate a positive and negative(?) power for eccentric work. I will need to do it in R though as the sampling rate is extremely high on real time data collection. I think the csv files are around 18mb per 10 minute match.
True, I don’t think “skinny” is really necessary. Just lighter with good rubber!
Skinny just makes it more aerodynamic, and a bit lighter though. Rolling resistance is theoretically better with wider tires even.
This website has a nice graphical interface to see the different drag contributions. It should be exactly the same as my spreadsheet, just no cadence/wheel size comparisons.
My rolling resistance estimate could be low; it might be more like 50 W instead of 30 W, given how knobby and thick 36" tires are… However, aero drag will still be the main componen at 33kpht. The weight will increase rolling resistance, but it is linear. For your example, 70kg total vs 74g total is 6% difference. So rolling resistance at the same speed would increase by 50 W * 6% = 3W.
Definitely something that matters, and is included in the equations. However, in real life using the right tire pressure, right tire, and body position/aerodynamics will be more important for speed on flat ground; I would almost completely ignore weight.
Weight on a climb though, is of course a big deal. It is proportional to the power to overcome gravity…And gravity is taking around 200W. Even 0.2 kg of brake is worth 0.3% * 200W = 0.6 W. About 7 seconds for your road climb race time! I took my brake caliper and lever off too to save those few seconds, no reason to not use a lighter unicycle and parts… However, rolling resistance is probably just as important if not even more… the 1 minute saving I mentioned above is probably almost all in the rolling resistance. Of course, finding the “fastest” tire is a lot harder than finding a lighter component.
Now for the off topic portion! 29 Tires
I loved my 29x2.0 Marathon Supreme. It scored well for rolling resistance. However, it is a bit heavy for uphill races. It is also not tubeless compatible. It is great for turning on all my rim widths though. I like to use this for my G29 riding in general since it turns well. However, for a big trip, I would definitely want something tubeless. Marath Supreme rolling resistance
For my ungeared uphill races, I have been using the Big One Liteskin 29x2.35. Great for most uphill races ungeared, since it is a bigger diameter. It is super light and scores extremely well in rolling resistance. I set it up tubeless, so I think this might be the lightest and lowest rolling resistance tire out there. However, it doesn’t seem to be available anymore. Big One rolling resistance
The new G-One Speeds, which are what replaced the Big One, do not seem to score well for rolling resistance. G-One Speed rolling resistance
The newest version (G-One R and G-One RS) use a different rubber compound, and seem faster, so maybe you would choose this instead of the G-One Speed. Maybe, they will come out with a slick version soon too… G-One R Rolling Resistance G-One R G-One RS
I recently bought and used Rene Herse Antelope Hill 29x2.2" Ultralight Casing with a latex tube. Rene Herse has narrower widths, and the model name for each width is different. It should be comparable weight and rolling resistance to my older Big One. However, I have read people have problems with tire blowouts when using the ultralight casing, high pressure, and tubeless. I have not tried it tubeless yet.
However, if you use a narrower version, like 48mm, that should help with tire blowouts.
The 2.2" version does not turn too well though for me. I had it at 45psi on a 25mm internall width rim. 29x2.2 Antelope Hill 700x48mm Hatcher Pass Rolling resistance for Rene Herse Slick Tires
If I had time and money to test for a long Guni trip in the mountain, I think the Rene Herse 48mm might be something to look into.
Rims:
I used the narrowest MTB rim from light bicycle they had at the time for my ungeared 29.
The used to advertise at 70psi max, but changed it to 40psi. I usually run my Schwalbe Big One Liteskin 29x2.35" at 45 psi tubless. There was no flyweight version when I bought mine. At 45 psi, the spokes lose a lot of tension (rim compresses). I would not go to the flyweight version on an asymmetrical disc brake hub.
Their newer 29" mountain bike rims look very nice though, asymmetric to help with spoke tension, and a little bulge so it is not a straight hookless profile. I just worry it might be too weak. They are very flexible with customizations though if you email them, so maybe if they could do a reinforced version, this would be a very good choice. 250grams, with around 100 grams reinforcement would still be 350 grams!
I use this gravel rim on my guni. Mine is hookless, and I regret not getting hooked! (On my bike, I’m happy with hookless though, since I do pinch the tire and hit the rim when I hit holes very fast) I run exactly at their max pressure rating of 55psi with a 32mm Continental Grand Prix 5000 for uphill races. A bit higher pressure would be better for sure with such a thin tire. Even if you use 2.0" tires, I think the extra reassurance will be good with a hooked version.
My G29 uses the standard weight version. My gravel bike has the flyweight versions. Again though, there is considerable spoke tension loss when you inflate the tire. I would not feel safe using the flyweight version on a unicycle, even at my body weight. It will be a tiny bit heavier than the mountain bike rims since it is a deeper cross section, but I think it looks cool
I have emailed them about drilling the holes offset, and they said they can do it. 1mm offset is no problem. 2mm offset, and they would add 30 grams to the spoke hole reinforcement layers.
I am a bit disatisfied with my flat pedal setup… It forces my feet to be further apart, which I don’t like. (At least 16 mm per side)
Few things I will try
custom cranks that are a lot narrower to move the pod inwards.
clipless pedals… will need to work on my unicycling skills before I try them again
If these don’t work, then I’ll have to look at the SRM X Power Pedals again! I think the high sampling rate data would be cool for road riding too.
This decreases the Q-factor from
100mm hub +
12mm bearing +
6x2mm spacer +
27x2mm crank width -
16x2 mm powermeter pod
= 210mm, down to 199mm (-11 mm)
This is still a bit wide, but now within what fat bikes use.
road/gravel bike = ~150mm
mtb = ~170mm
fat bike = ~200mm
Another interesting thing I learned from this exercise is that standard “0-Q factor” unicycles with 100mm hubs have a Q-factor of 178mm. This is wider than a mountain bike, and much wider than road bikes. I almost never ride my mountain bike because the extra 20mm Q-factor feels very uncomfortable to me…
Unfortunately, the Favero Assiomas do not give “platform center offset” data. Garmin Vectors give this data. It seems it might be interesting to compare to bikes given the different Q-factor.
Looks good, that 3d printed filing guide is a neat idea. That powermeter pod really does look big, but with the modified cranks it looks like a similar offset to many normal pedals now.
That’s why I’m always confused that some people like “high Q-factor cranks” on unicycles.
regarding Q - perhaps sometimes (eg in muni) feet catch on cranks unexpectedly (mitigated by outward curved cranks), or fat tires rub against legs (or maybe some people walk like ducks?).
I really like a high q-factor crank because my heels will always hit the crank otherwise. On my square taper cranks with just a slight q-factor I rubbed most of the paint off and they rust if I don’t use them enough to wear off the rust. I suppose I do walk like a duck also. The outer edge of the heal of my shoe soles gets worn down first. I only have 100mm hubs though, so perhaps I wouldn’t like high q-factor cranks on a 125mm hub, but I haven’t tried that yet.
Made some 3d printed platforms that are thick enough so that I stand on top of the pod without touching it. No I don’t have to modify my cranks (which was not possible with hollow bicycle cranks)
I am not sure how robust I can make them. One good thing is it can be super custom… but with a new challenge of figuring out what type of pedal shape and pin placements are best. Did my best for now to just look similar to other pedal designs.
If anyone is interested, I could share the other files/parts.
Tried the first version (larger, clear/white colored) one indoors on my bike, and it worked fine. Hopefully I can find time to ride them more soon
I have to say a very appreaciative “Thank you” to Unicycle Harry for the 3D print model.
The local bike Shop had a sale on Powermeters, and I got a Favero Assioma Duo Powermeter. (Both pedals have power sensors)
My son printed the Pedals on his new 3D Printer - Anycubic Kobra 3.
I just installed the right pedal Power Meter, installing the bearings in the 3D printed pedal. Finished printing it this morning - took approx. 8 hours (material: PETG) Needed just a slight bit of sanding and the bearings have a firm push fit.
My Wahoo computer connected with the Assioma’s but it only has a minimum crank length setting of 140mm.
I’m using 110mm cranks on my G36, so in the Power meter app I set crank length to 140mm with a 1.25 power scale factor.
Just some feedback on my 3D printed pedals with the fusion files. The geometry is great, as a starting point, especially the fitting of the Favero Assioma Power Meter and bearings.
On my first trial of the pedals, they lasted 3km.
First one smashed to pieces on impact from a simple upd. To be fair, I didn’t print at 100% fill and that contributed to the structural failure of the pedals. But also the geometry of the pedal has many thin sections.
Version 2.0
Is currently being printed - 23 hours printing time. I modified the 3D model in AutoCAD. Changes include:
Print at 100% fill
Simplified shape with flat sides.
Component will be a solid block.
Bolt an aluminium 3mm plate to the outside face of the pedal. Add rubber on top… Should resolve the weakness of the Printed PETG with impacts of the pedal with ground in UPDs.
Image of a failed print - filament melting temp too low. Sitting on top of 3mm Aluminium bar I will cut to fit.
I don’t think it is the best solution. Looking at how it broke, I would say the main problem is the print orientation. It broke by delaminating, to avoid this kind of braking, you should print your pedals flat on the plate instead of standing up. You might end up with poor print quality inside the sensor hole.
I should add that PETG, ABS and PLA might not be the good choice of materials. I would personnaly use nylon or hard TPU (at least 95A or 50D). This way it wouldn’t shatter on impact (and ideally I would put an insert inside to fit the hub as well as possible, and then the actual plastic around).
Hi,
Here is a picture of the 4th iteration of pedal that suits me. I 3D printed in the same orientation as Unicycleharry to get a good circular internal diameter for the bearings. I have tried printing with the pedal flat but the 3D printer prints supports in the bearing internal diameters and they leave residue that leaves an imperfect internal diameter, even after filing and sanding. I don’t want to be forcing the bearings in.
Anyways, 4th version has more area, I needed for foot placement and felt so good in test run yesterday.
I am just loving having a Power meter that gives me a number at the end of the ride.
watts/kg
With my Unicycling progression, I have always enjoyed the feeling of the “micro” improvements as I adapted and improved. I feel this is a natural progression of that.
My main form of Unicycling is commuting to work and I enjoy looking at my data after each ride.
Now I have a definitive measure of my progress with fitness. I understand that having a power Meter gives me the same information as if I am going to the gym and knowing size weights I am lifting.
The best thing of all is I feel I can compare my cycling to any other cyclist in Strava who has a Power meter.
That is: Max power at for 30sec, 1min, 5min, 20min, 30min, 1 hour etc). I can directly see the two Power curves on one chart.
This is such a motivating thing for me.
The Power curve below from Strava compares my Max power (grey line) at respective time intervals with a work colleague (purple line)
His power curve is from a workout of similar time, about 5hours and elevation climb, 1400m.
This power data on my Wahoo Elemnt is the first screen I look at now, after a ride.
I can see if I have improved/worked on my short, med and long term effort and fitness.
Screen 1, my normal commute
145w for 60min. Quite consistent and the number I want to slowly increase for general fitness.
