noglider 

I believe you would burn more oxygen and fuel than the child would, because you each have to lift your arms, and your arm is heavier than the child's arm.

CliffordK

I'm glad to hear the project worked out, and hope the end result is what you desired.

What all these calculations seem to ignore is that a 100 pound rider and a fit 200 pound rider can put a huge difference of force into the pedals.

So, the 100 pounder may need a low gear to spin.
The 200 pounder would need significantly higher gearing, even if they're spinning.

And, not everyone can maintain maximum power at 100 RPM.

Like you, there are also intermediate steepness hills that I spin out on. A good tuck might take less energy, but wouldn't speed a person up.

cny-bikeman

Not sure what you mean by that statement. A good tuck reduces wind resistance and would indeed speed a person up over coasting without tucking, increasing the potential energy available to coast partially up the next hill. Furthermore, coasting in a tuck takes substantially less energy than pedaling against the wind at 40+ mph, and that saved energy is available for the next uphill.

ThermionicScott 

I was envisioning Tom Platz.

CliffordK

It depends on the hill.

There are a quite few hills that I can coast down at about 30 MPH.
I spin out at about 42 MPH (downhill).

So, I suppose if you take 2 riders descending, say a mile. One at 40, one at 30. That would only be about a 1/4 mile difference at the bottom (plus the added momentum at the bottom).

Perhaps I'll have to practice more tucking, but I'd hate to be that rider always having to make up the quarter mile at the bottom of short hills... more on longer hills.

cny-bikeman

I believe you need to think a little deeper about your scenario. They will not both be at that speed for the entire hill - in fact probably not till near the end will the difference be very large, the person pedaling would have used up significant energy to go faster downhill (the lion's share going to defeat wind resistance) and it's unlikely that a hill that can be coasted at only 30mph can be pedaled as high as 42mph. I'd hate to be that rider who used all their energy to go a bit faster downhill having to go up the next hill. Generally it's only in a race, where one needs to keep with the pack, where pedaling downhill is advantageous.

https://www.joefrielsblog.com/2010/08...-downhill.html

60_tooth_ring

Ha ha ha! 10,000 comedians struggling to find work, and here you are cracking jokes

60_tooth_ring

It's not an unreasonable estimate that the combined weight of my legs exceeds 100 pounds. I'm 5'11 and currently 292 pounds. That's 4.11 pounds per inch, so with a 31 inch inseam that's 127 pounds "on average."

bikebreak

for real? that would explain it. how did the world rotation gig pay?

60_tooth_ring

It was a tilted pay scale.

ksisler

OP; I will offer a group hug to help you get over the eye pecking resulting on your post. I have always said "if you can build it," great, but if you can "build it and also ride it" awesome. Go for it. If you can get a speeding ticket from a state trooper, post it.

CliffordK

If you're standing up.. (on one leg), then you're putting the full 292 pounds of weight into downward force at the cranks (mid crank revolution). Some people can pull up a bit. I don't know how much, but say you pull up with 10 pounds while standing, then you add essentially double that (upward plus downward force), to get over 310 lbs force into the cranks.

I suppose since the cranks are essentially falling away from you, you're not quite getting that full force, but it is pretty close depending on the cadence.

And, your legs support your body so they're used to lifting that 292 lbs (plus some if you lift weights), although full 1 legged squats can be difficult, but certainly not impossible.

Anyway, the forces you can put into the cranks might make a 100 pound rider cringe. Some of it will be taken up by it requiring more power to make the bike move, but some might also be appropriate to do more power at at slower cadence.

60_tooth_ring

I only stand up to remove a wedgie.

djb

thats a great ad.

I too spin out at about 70kph with a 50/12 and being a skinny, not strong guy with oldish knees, just cant handle lower cadences.

CityBike

Hello there. is this possible if i want to use 60 / 50t? 2 speed crank. which gear shifter do I use if appropriate? thanks for the answer.

shelbyfv

Back so soon?

Koyote

Even Ashton Lambie only used a 56 tooth chainring to win the DK 100. ‘Course, he’s a national champion and world record holder.

79pmooney

A 60-11 isn't for me. (I benefited in my race with the biggest downhill having just a 54-14 when everybody else had at least a 52-13 because it meant I couldn't work in the small group on the descent. Smuggler's Notch. I couldn't even catch up to the freewheel.)

That said, I applaud 60 tooth ring for doing the unusual with bikes. I'm the guy who had built for me a road fix gear with a forward facing dropout so I could run any track cog made without messing with chain length, then proceeded to ride Cycle Oregon on it 4 times, including the two hilliest in recent years.

Now that bike was pretty straightforward from a design/build standpoint except for the custom dropout cut from plate. My next project, using the same builder, was to make a triple chainring fix gear out of my old custom. That required custom chainring bolts and brazing two cogs together. This to have a fix gear with, like the custom frame I just mentioned, the ability to run 3 very different fix gear ratios in the mountains with fast roadside changes and clearance for big gravel-worthy tires.

These bikes aren't for everybody. I get asked all the time "why don't you just use gears?". My answer - because I love to ride fix gear. A 22 speed high end bike doesn't have even one fix gear on it anywhere. I have two/three geared bikes. Over half my lifetime mileage is on fix gears. I'm 66. My knees no longer want to and my legs are barely able to ride long climbs on the 44-17. Now I have to stop more often. But I get to ride my favorite rides still on my favorite drivetrain.

60 tooth ring, ride the heck out of this thing! (And working with builders who "get" what you want is fun, isn't it.)

Ben

Last ride 76 

News Flash... 40 mph is not exactly fast, on a moderately steep descent. Racing, neither is 50...

High speed descending is something one must learn, if racing is the goal. Learning it during a race is NOT the right time. Riding within the speed limit on known roads, with good visibility, in good conditions, with a well tuned bike is the right time. Not to be equated with gratuitous speeding on a motorcycle. Full helmet and leathers, at 110 mph, as if...funny man.


Btw, I'm not a prude, and if you weren't putting anyone else at risk, not a big deal to me. But don't compare race training, or even skilled riders choosing to descend at high speed, to your example..

djb

Asks, High speed on a bicycle on a descent on my experience is never related to gearing-- certainly not with panniers. Every time I've hit 80,90k I'm way past spinning out anyway.

As with going very fast on a motorcycle, it's all about "the right place and time"---experience, reactions, judgement and bike handling abilities all come into play.

And one persons crazy fast light speed, is another person's calm and measured speed-- but again, time and place, and never putting others at risk.

Koyote

I used to routinely hit 60+ miles per hour on a certain descent when I lived in Colorado. And once hit 75 mph on another Colorado descent during a race. Both done with a 53/12.

If anyone thinks they need a 60t chainring to hit high speeds on descents, they just don’t know how to descend.