I wrote this blog/ article using existing research on this topic. Wanted to share here to see if anyone had any feedback:

https://www.pinkbike.com/u/redfoxrun/blog/beyond-the-chain-a-look-at-gearbox-efficiency.html

Since writing that, found this link: https://roymech.org/Useful_Tables/Drive/Gear_Efficiency.html

Using the math in that link, would it be possible to match up the types of gears in a Pinion P1.18 and calculate/ approximate the efficiency?

Thanks!

Building a wacky proof of concept unicycle. my cranks are each on their own 'slave' axle. That is to say that the cranks do not have an axle that goes through to the other, but are only mechanically connected by chains each side takes to the main axle. I am wondering how out-of-phase my pedals might get with each other because of backlash. assume constant good chain tension and new chains, chainrings, and sprockets.

This image of a giraffe unicycle provides a good example: imagine if the axle that connects the cranks here were split in the middle. would the cranks be able to stay level/180 degrees out of phase from each other? how much backlash does each gear to chain interface add?

https://preview.redd.it/8kcseocm7wee1.jpg?width=750&format=pjpg&auto=webp&s=0f0aac9f147942a879f9bd678234d9a3a08ed651

I'm looking to direct the motion of a wheel to a linear path. mountain bikes and a majority of suspension electric unicycles use stanchions with bushings. there are a notable few suspension EUCs that make use of a roller system. I am also considering using teflon linear guides. I'd be grateful if anyone knew a reliable source of any of these in the 100-150mm travel range. teflon linear rails and internal-less fork stanchions are preferred.

Stanchions for a fork

Roller rails for the Kingsong s22 EUC

plastic carriage on a parkerized metal linear rail

Hi, I wrote this article because of a lack of curiosity related to the two most common MTB hub standards. I welcome any feedback or ideas.

https://www.pinkbike.com/u/redfoxrun/blog/no-more-mtb-broscience-157mm-vs-148mm.html

Gday bicycle nerds 👋

I'm trying to wrap my head around the steering characteristics between two different front-end bike setups, but I think the question can be seen as a generalised one, hopefully.

Context: I had a custom flatbar gravel bike made where the geometry was based on a bike fit. As a curiosity, I asked the frame builder if he could give me a drawing of what would change if I wanted drop bars instead. The two geo results can be seen on this BikeGeoCalc page. Note, the seat post back is identical. This only relates to the front triangle and cockpit setup.

• Hit the "swap bikes" button to switch between the two options.

• Hit the "quick fit" button to see the measurement between the nose of the saddle and the end of the stem/handlebar position.

Assumptions: Assuming the frame builder was wanting to give me similar bike handling between thew two options, and given a 70mm difference between the saddle nose/end of stem difference which might account for say a 70mm reach drop bar, the hood position would still be further out by maybe another 70mm, so the overall extra reach on the drop bar option would be much longer than the flatbar.

Question: Is this fit somehow compensating for narrower dropbars vs wider flatbars (440mm vs 740mm)? Should the steering feel from this flatbar (two hands 740mm apart and 80mm out from the steerer tube) and this dropbar (two hands 440mm apart and ~200mm out (90 stem + 70 dropbar reach + 70 hood reach (allowing for C-C tube diameters)) be similar? How does this relationship work?

For example, note that the hand position is far more over the front axle in the dropbar setup. Does this help even the feel between the two options?

Thanks for reading this far. Hopefully I've made my question clear enough :S

Thanks for any thoughts!

Are there parameteres other than the headtube length, head angle, lower headtube distance from lower bearing (offset of the weld) and bottom bracket drop which can be used to adjust the stack of a frame? I can't think of any but feel like I'm not thinking off all the possibilities.

Fellow Engineers,

I have access to a bunch of small kid bicycles (12 inchers) that are no longer needed (kids outgrew them). Being a tinkerer myself, I was planning to repurpose the rear wheels on these to build a robot chasis. . For a prototype, I am looking to build a chasis with 4 wheels, independently driven by 4 DC motors + gears + belt and sprocket, speed adjustable and reversible.

Therein lies my biggest problem though... Is there a way to reverse the wheels? I took one of the wheels apart and my plan was to remove the pawls/bearings and weld the 2 races. Not sure if this will work, or if there are easier/better options.

What would you do?

PS - I have prior experience building robots with swerve wheels. This prototype wont be a swerve, but should still be quite functional IMHO. Let me know your thoughts.

Hi everyone, curious if anyone has any experience with hydraulic disc brakes and the durability and maintenance cost/frequency of them? I’ve done my own research and they seem alright but wanted to ask the community.

I have a mechanical disc bike and truthful sort of prefer rim brakes but open to giving hydraulic disc brakes a try. Thanks!

Gday cycling nerds :)

I have a single-sided 4iiii crank-based power meter on my road bike, and a Tacx Neo 2T trainer for the off season. The 4iiii meter gives higher power numbers averaging 10–15%. Depending on effort the number will fluctuate between maybe 5–20%, so it's not a continual % shift. I ride flat pedals on all my bikes so I have a 'choppy' pedal circle with all power on the down stroke, but even with power smoothing on for 5 sec average, the % difference exists.

I've engaged both companies, and even sent the crank meter back for calibration. Both companies maintain their products are accurate within spec. I've also tested the crank arm power (w head unit) AND trainer power (w training app) at the same time on the same indoor training session.

Could the difference in location/method of power measurement account for this discrepancy? I assume the single-sided crank meter would simple double the figure from my measure crank arm to estimate total power, so I could be severely lopsided, but I wouldn't think it would be that lopsided. The indoor trainer is measuring power at the rear hub so left/right wouldn't factor in to total power.

I thought maybe r/bicycleengineering might shed some light on this from a physics/mechanical/materials angle.

Thanks for reading and for any thoughts!

TLDR: why would a front derailleur shift up better when the chain is well cleaned and lubed?

One of my commuter bikes has "2X" derailleur gearing, with friction shifting for the front. A while ago, I hastily set up the front derailleur and ended up with the limit screw set so that it's just barely able to shift onto the big ring. I could very easily address that slightly and have it perfect, but before I did that I noticed something interesting. When the chain is freshly cleaned and lubricated, it shifts up almost perfectly. But as the chain starts to get dirty and dry, the shifting gets less reliable. I need to have just the right conditions in order for it to shift up. So in the interest of science, I haven't adjusted the limit screw and have continued monitoring this through a handful of cycles of letting the chain get worse and then cleaning and lubing, and the pattern is really consistent.

My naive mental model was that I need friction between the chain and the inner surface of the big chainring to help the chain climb onto it. but as I think about it more, there's also friction between the derailleur and the chain. And given the pins and ramps on the chainring, maybe friction there plays less of a role and so overall it works better with less friction?

I can't think of a way that friction in the actual pivots would play a role, but maybe it does. there also might be friction to overcome in getting the chain to go over the actual teeth in the final step of getting engaged.

Maybe next time my chain gets dry I should try just lubricating the front derailleur cage—obviously a bad idea for chain maintenance, but maybe an interesting experiment for shifting?

So carbon fibre's greatest advantage is its tensile strength. It's really strong under tension. However, it's also very flexible under other loads since it's a weave.

Given the fact that bicycle forks are under compression, how does the carbon fibre manage to give it additional strength? What does the weave pattern look like? Do forks actually rely more on resin rather than the carbon fibre for compression loads?

Does the weave's actual role come into play when it comes to bending rather than compression?

It's something I could never wrap my head around. Thanks!

Hello friends! For a while, I wanted to use both my light and USB charger at full power on my bike. However, when the USB charger was connected to the system, the light’s intensity would drop to half. So, I separated them using an on/off/on switch. Now, I can either turn on my light or direct all the energy to the power bank. If I don’t need either, I can turn everything off as well. Now, the only thing left for me to do is to shorten this mess of cables a bit and place them inside the fork steerer tube.

https://i.redd.it/el9tpuusfdpd1.gif

https://reddit.com/link/1fj1id7/video/gzqsowdqtepd1/player

The circuit diagram I used is the one shown above.

You can see how it works.

I hope this helps spark new ideas for some, or serves as a solution for those experiencing the same problem.

I'm looking for a bolt on swing arm extender for an ebike with vertical dropouts. Do these exist or are they possible?

I realize there would be downward torque applied to the vertical axle pivot. I have some grin tech torque arms which I can install on both sides of the original swingarm to make the vertical dropout axle more rigid. Dunno how to figure out the math on that though. My bike puts out over 200nm torque at the rear wheel.

Tyia for any insight.

Hello,

Sorry if this is the wrong place to ask this question. I am working on a wacky bicycle and am wondering if there are any internal gear hubs that take input from both sides like in the picture attached. If not, any ideas how I can approach this?

Thank you.

https://preview.redd.it/xwdhocqbbujd1.jpg?width=4032&format=pjpg&auto=webp&s=8c2505774a6b134c97d6164c9a9392bb216c9982

Just getting back into biking after many years. Looking at new hybrid bikes. Question about forks: When a manufacturer says "alloy" fork (e.g., Trek on its FX2), does that imply chromoly or can it mean other alloys as well (and if so, what)? Also, Trek's FX1 features a "FX Steel" fork -- is that probably hi-tensile steel (and not chromoly)? I'm also reaching out to TREK but think I'll get a response sooner here.

Anyone have engineering experience to help work through the advantages of using a ball drive vs chain drive?

Former serious cyclist that developed limiting cardio health condition. Still want to peddle on level and downhill but need assistance on uphill and headwind. Begrudgingly gave my classic, well-appointed Kona MTB (circa 1990’s) to my daughter when we moved and I’m in the market for the right hybrid. Looking for geek quality componentry, with a bit of e-help when needed. That could be 50/50 or more ebike for awhile. Suggestions?

Given the same size rear-cassette. For simplicity, ceteris paribus

How much a single chainring (for exemple 36-28) will lose im comperison to a double crankset (for exemple 36-28)? Let's assume we can model the problem as two vector components, and the cos(x) is the % of force transmitted:

On my 1x12 34x10-51 bike:

• The chainstay is 425mm
• The chainline is 48mm
• Let's assume the chain is offset by 24mm on the granny. hipotenuse (chain itself) = 425.68

cos(x) = chainstay / hipotenuse = 0.9984
sin(x) = offset / hipotenuse = 0,0563

On my old 29er:

• The chainstay is 440mm
• The chainline for the smallring is 42mm
• Let's assume the chain is offset by 21mm on the granny. hipotenuse (chain itself) = 444.5

cos(x) = chainstay / hipotenuse = 0.9988
sin(x) = offset / hipotenuse = 0,0476

That's correct? The loss is >1%?

Why the 2x feels much more smooth?
And the 1x sounds like a coffee grinder?

In the past 36-22t was the standard for a 2x step. You could hit awsome leverege with a relative small/light cassete (22x36 or 22x40). Now 1x setups rule the earth, and the 2x is unusual. Now there isn't the 22t option, you can only get 36-26. Why?

Size of the jump? I never had a problem with this.
Chainsuck? The Shimano teeth profile almost eliminated this, I only had it with mud.
Chain tension?
Other reasons?

Why?

I've had a really hard time finding an answer to this question either in bike shops, talking to cyclists, on the various subreddits, or any other website because most answers seem to be just:

1. How fast/hard the rider pedals
2. How aerodynamic the rider is/what they're wearing
3. How much force the rider can apply based on bike geometry
4. Keeping gears, drivetrain, and shifters clean/gunk free

There's usually a comment somewhere about tires/wheels but not much information about what makes some faster than others.

So what is it that makes a $12,000 racing bike faster than, eg, my Trek Checkpoint AL3? How would I know what would constitute an upgrade for speed if I wanted something faster?

Hi all, I am a university student with not much knowledge of bikes. Could anyone tell me the exact material commonly used for bike cranks. More specifically what type of steel, or aluminium or carbon fibre is used. Currently my report uses a 6000 series aluminium alloy which needs to be redesigned to be stronger but still cheap/affordable. Thanks!

Would like opinions of the use of pinion’s C1.6i 6 speed gear box using rear electric drives. In climbing, is 6 speeds enough? What are likely disadvantages? Spoke breakage? Motor overheating? Premature gear damage?

I am trying to buy or build a no-frills touring bike on a budget. I also got a bike fitting that ended along the lines of "you might want to consider a custom frame" due to my long cycling inseam and somewhat average height. I've shopped around a bit and I'd like to have the frame built by Marino in Lima, Peru, because of the reasonable price and my fondness for Peru.

I may hire a frame designer, however, I think it's rather fun to take a crack at this myself first.

Using the search tools at bikeinsights.com, I discovered that the Salsa Vaya is a touring frame with a very upright posture.

I also discovered that BikeCad has a 56 cm 2011 Vaya in their design archive. Seemed like a good place to start.

So. I downloaded that design and made the following adjustments:

1. Reduced effective top tube from 560 mm to 500 mm
2. Lengthened seat tube from 530 mm to 550 mm

This left me with a bike that seemed likely to have a toe overlap issue. So, I...

1. Reduced the wheel size from 700c to 26"
2. Reduced the head angle from 71.5 to 70 degrees

Problems:

1. Even with these adjustments, the front center length is now 565.2 mm. I've heard that anything less than 590 is likely to cause toe overlap.
2. I realize that slackening the head tube angle will affect the handling - I'm okay with this angle. However, it may have unintended consequences for reach, and I'm not sure how to account for that.

I'm including my measurements and my current design in case anyone is willing to weigh in. Also, feel free to respond with "just leave frame design to the professionals, you fool," or "you're not special; just get a standard frame size and figure it out." Also feel free to redirect me if I'm posting in the wrong place.

I'm developing a pedal with some unique features. First production volume will be between 1,000 - 5,000. The primary area of design is the actual pedal and I assumed sourcing spindles would not be a challenge, but now I'm not so sure. I haven't engaged the big guys yet (eg Wellgo), but I am led to believe there is big wait times.
I'm based in UK and would accept paying a premium over Far East supplier if there is a reliable source in Europe. But getting stock from Far East would be ideal. This is for "town and country" bikes - so it just needs to be basic reliable design. Nothing flash, just does the job.

Early in my quest here but I assumed it would be easy - now I'm not so sure. I've been warned away from Alibaba but very open to any suggestions... either stainless steel or a lesser steel if proven and sufficient