# Thread: Theory of Diminishing Weight Savings

1. ## Theory of Diminishing Weight Savings

Posited: that for a given rack location, the sum of the weight of the bike and the weight of the appropriate lock is a constant.

Not yet proven but supported by anecdote.

2. Why would the weight of the bike vary with the rack location? The weight of the lock, I can see that.

3. I agree. I've heard that your bike and lock(s) should weigh 40 pounds. I can see where rack location could make a difference.

I my small town, I would leave my 20 pound bike with one U lock and cable, but I would not do the same in a downtown metro area.

4. Ratio is : fancier the bike , the heavyer the lock you need,

in order to have it there when you come back to where you parked it.

now where the Bike Rack on the street, is does make a difference ..

Ever seen a frame locked up and every other part stripped ?

Now if you have where the rack you park your bike is a Variable factor..

then, if, there is a, say, fence around the bike-rack with its own Lock ..

or webcams and the area can be flooded with tear-gas and pepper-spray
remotely from the monitor site ,

5. This is why I leave my lock on the rack at work. If the lock required is dependent on rack location, why not leave a lock at the place I'm going most often. I keep another lock in my desk in case I want to stop somewhere on the way home.

The bike+lock weight is also somewhat dependent on how long you'll be stopped. In all but the worst areas a simple U-lock (but not a cable lock) will do for a quick stop at the convenience store. If you're leaving the bike all day, you need serious metal. If you're leaving it in the same place everyday, that probably also ups the required lock weight. How much does a bike locker weigh?

6. Originally Posted by jyl
Why would the weight of the bike vary with the rack location? The weight of the lock, I can see that.
It's the sum of the weights. Say, for instance, a 20-pound bike requires a 20-pound lock. In that same location a 30-pound bike requires a 10-pound lock and a 40-pound bike requires no lock. Of course this formula fails completely in places where bakfiets are considered nice bikes.

7. My sister-in-law locked up an old no-name three speed for 4 years in and around Oakland CA with a bungee cord. See called it the "bungee of trust". I think that bike weighed around 45 pounds, including basket, kickstand, fenders, and about 4 pounds of rust.

My sister-in-law locked up an old no-name three speed for 4 years in and around Oakland CA with a bungee cord. See called it the "bungee of trust". I think that bike weighed around 45 pounds, including basket, kickstand, fenders, and about 4 pounds of rust.
+1

9. I refuse to leave my bike outside anywhere !!! it comes inside the stores with me. if the bike has to leave so will I

10. Originally Posted by Darth Lefty
Posited: that for a given rack location, the sum of the weight of the bike and the weight of the appropriate lock is a constant.
I like your theory. My only corollary would be that losing 50 lbs of body weight makes the bike and lock mass-less. I'm working on it and ever hopeful.

11. Be free, don't carry a lock, your bike will be weightless and ever accelerating.

12. The sum of the weight of the bike and lock must always equal precisely 30 pounds. That means if you have a 15 lb bike you need a 15 lb lock, or if you have a 40 lb bike you need a -10 lb lock. Gravity is, of course, part of this equation, so if you're parking on the moon you'd need to account for less weight per unit of volume and if parking on, say Jupiter you likely won't be able to park your bike unless it's made of something with little mass, like hydrogen.

Hey, I didn't make it up: It's a universal constant, like pi.

13. This is somewhat amusing.. I'd wager I use a much heavier main lock than most people here, and my "cable lock" is probably lighter and cheaper than most here.. but I use both and haven't had a bike loss yet.

14. Originally Posted by J.C. Koto
Gravity is, of course, part of this equation, so if you're parking on the moon you'd need to account for less weight per unit of volume and if parking on, say Jupiter you likely won't be able to park your bike unless it's made of something with little mass, like hydrogen.
In order to take a bike to the moon it would have to be built to aerospace standards which means it would be made of nobendium to save weight and yet weigh, er, mass just as much as any other bike to have positive structural margins.

15. Originally Posted by Darth Lefty
In order to take a bike to the moon it would have to be built to aerospace standards which means it would be made of nobendium to save weight and yet weigh just as much as any other bike to have positive structural margins.
Good point

16. ..... and ever accelerating.
.. since 'the Big Bang'.

17. Originally Posted by Darth Lefty
In order to take a bike to the moon it would have to be built to aerospace standards which means it would be made of nobendium to save weight and yet weigh, er, mass just as much as any other bike to have positive structural margins.
Well, not quite..., or to really analyze this physically, a moon-optimized bike would have completely different specification.
Assuming the rider stays the same and delivers the same power in the same manner, gearing would need to be much wider, since the inertia to be overcome for starting doesn't change for the better (more likely is much more formidable, due to the mass of an oxygen tank breathing system, and pressure suit with cooling and dehumidification systems) . However, aerodynamic drag would be nil, and rolling resistance (assuming equivalent surface for riding as on Earth) would be reduced in proportion to the net weight of the bike + rider + moon subsystems (at moon gravity). Hence much higher speeds would be possible, at the end of the day limited only by rolling resistance and other frictional losses, or possibly, by the upper gearing limit imposed by the lower gearing requirement (as explained above) and the feasible gearing range of the drivetrain.
I also envisage that some kind of non-permanent restraint to keep the rider on the saddle when desired for high in-saddle power levels would be helpful. E.g. tight fitting shorts with a Velcro interface to the saddle. That is assuming that the environmental suit that the rider must wear does not completely negate the weight advantage of being on the moon.

18. Originally Posted by old's'cool
Well, not quite..., or to really analyze this physically, a moon-optimized bike would have completely different specification.
I was kidding and sort of complaining, but I'd love to really work out a bicycle for the moon. (Or an HPV airplane for Titan, while we're at it.) They worked out a buggy so the basic idea of wheeled vehicles in the first place is all right. Huge tires for thick dust and rocks, and it still needs to be strong enough to take the force a human can put into it. I suspect the main difficulty would be successfully pedaling while wearing a pressure suit. Their range of motion and flexibility looks terrible.

19. Might you be referring to a Moonlander???

20. Originally Posted by gregjones
Might you be referring to a Moonlander???

I saw one of these at the local bike shop. Looks like so much fun. I'd love to try one and roll over curbs.

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