The Crankpump is this cool kickstarter i’m backing that i thought i would try to promote. It turns a hollowtech bottom bracket into a place to store a co2 cartridge, chuck and these crazy little tire levers. Im not involved with the project at all, other then backing it on kickstarter, but I do want to see it made. So, if you want to take three more things out of your saddlebag check it out.
https://www.kickstarter.com/projects/crankpump/crankpump-the-invisible-bike-pump
It looks like tools are not needed to remove and replace the device from your crank. That means it has to be reasonably loose, which in my experience means it will slowly work itself free, which would be annoying. If you need a tool to remove it or tighten it, that kind of defeats the purpose as you’ll have to carry that with you.
I’ve never flatted and had the problem be solved by simply pumping up the tire again. You will in 95% of cases, barring a very slow leak needing just enough air to get home, need a patch or inner tube. You can just tape a patch kit to the underside of your saddle, but I think most of us carry spare tubes. If you’re carrying a spare tube in your pocket or saddle bag, it’s trivial to also carry a co2 canister (and I always carry multiple co2 canisters).
Those tire levers are not going to work on a number of wheels where the tire is tight. I’ve had wheels, like the aluminum brake track Zipps, where they broke normal tire levers just trying to get the tire removed. There is no way you’re getting these “patent pending” tire levers under a tight tire. Also, I’ve always “unzipped” the tire from the wheel with normal tire levers once they’re under. They’re acting like this is something new.
I think they’re trying to solve a problem that doesn’t exist. Do mini bike pumps really “beat up your kidneys”? In any case, compare apples to apples and compare this to putting a co2 canister and one of those mini inflators in your pocket. I hardly notice they’re there once they are in my pocket, and I have a little bag with a patch kit, tire boot, 2x co2 canisters + inflator, multitool, and spare tube that I grab every time and stays put unnoticeably in my pocket.
That said, I would buy one of these once they’re successful and out in the real marketplace (not the “donate and pray you will get something in 3-6 months” Kickstarter marketplace) because I could always use a spare co2 canister, especially on those super cold days where your fingers aren’t working right. Also, it seems pretty innovative to store something in the center of the crank and I would like to support that.
Of course, the elephant in the room is, how many watts is it going to sap spinning a CO2 cannister round and round round. I know they say “it makes negligible difference” but I NEED NUMBERS DAMMIT!
+1, seems like a pretty complex solution to a problem that doesn’t really exist. There are already plenty of tube/CO2/patch/lever/mini-pump options on the market, and there are already at least 3 places I can think of to store them - back pocket, saddle bag, water bottle - which are all pretty convenient.
While it’s a neat idea, it just doesn’t really seem to offer any advantages over the existing solutions. Even assuming it was 100% mechanically sound (i.e. no chance of your crank coming loose), could be proven to have a <1W impact on your power, and cost no more than a normal saddle bag, levers and CO2, I still don’t think I’d be interested.
I like it.
I’m currently entering my winter phase of remodeling my bike, coming up with new ways of storing bit and pieces and cleaning up the look. Nobody likes a junked up look.
The only bit I don’t like is that the tire “levers” look borderline useless. My tires rarely are as easy to remove or put back on as the one in the video.
I still think it’s a cool idea, and if I had a hollow crank, I would be on board. I would hope that it could also have space for a bigger Co2 cartridge so you could get a bit more air on a race day…
Cool gadget. Very 007 like.
Im kinda in the same place as maplesyrup, im always looking for ways to clean up my bike.
On the other hand, this does nothing to clean up your bike.
that’s pretty clever, hope it takes off.
In the meantime, you can pump up your leaky tire all day and take charge of snarling farm dogs with this unit:
It’s a solution looking for a problem.
Tire levers look like they might or might not work.
You’ll still need a place to store tubes.
Room for only one co2 cartridge since most bikes only have one
bottom bracket.
No sale.
I’m thinking of this more as a race day aid. I can’t fit a tube, Co2 cartridge, and adapter underneath my saddle. But I can fit a single tube.
And for those already with a flat kit, taking a CO2 cartridge out of the bag could make room for a second tube. (So I would be able to carry two tubes and two CO2 cartridges as well.)
Of course, the elephant in the room is, how many watts is it going to sap spinning a CO2 cannister round and round round. I know they say “it makes negligible difference” but I NEED NUMBERS DAMMIT!
Ok, brace yourself, here’s some numbers:
For spinning at a constant speed, the weight of your cranks saps no power.
It’s only when you accelerate that the inertia of your cranks makes any difference… but how much difference does CrankPump make?
CrankPump weighs 30g, and its weight is distributed pretty close to a solid cylinder of 18mm diameter.
For cylinders, inertia = 1/2 mass * radius^2 = 1/2 * 0.03kg * 0.009metres^2 = 0.000001215 kgm2
Let’s compare that inertia to pedal weight, to see how many extra grams of pedal weight would give you the same increase in inertia.
Assuming you have 172.5mm crank arms,
For a simple pendulum, Inertia = mass * radius^2, so mass = inertia / radius^2 = 0.000001215 / 0.1725^2 = 0.04g
So CrankPump has the same effect on acceleration as adding 0.04 grams to your pedal weight (that’s less than one raindrop).
Of course, the elephant in the room is, how many watts is it going to sap spinning a CO2 cannister round and round round. I know they say “it makes negligible difference” but I NEED NUMBERS DAMMIT!
Ok, brace yourself, here’s some numbers:
For spinning at a constant speed, the weight of your cranks saps no power.
It’s only when you accelerate that the inertia of your cranks makes any difference… but how much difference does CrankPump make?
CrankPump weighs 30g, and its weight is distributed pretty close to a solid cylinder of 18mm diameter.
For cylinders, inertia = 1/2 mass * radius^2 = 1/2 * 0.03kg * 0.009metres^2 = 0.000001215 kgm2
Let’s compare that inertia to pedal weight, to see how many extra grams of pedal weight would give you the same increase in inertia.
Assuming you have 172.5mm crank arms,
For a simple pendulum, Inertia = mass * radius^2, so mass = inertia / radius^2 = 0.000001215 / 0.1725^2 = 0.04g
So CrankPump has the same effect on acceleration as adding 0.04 grams to your pedal weight (that’s less than one raindrop).
I believe he was being facetious.
If it were a US-based Kickstarter I would be on board. But that is a lot of shipping for such a small item.
Plus I just switched to a Rotor 3D crank so I wouldnt be able to use it anyways I guess.
Of course, the elephant in the room is, how many watts is it going to sap spinning a CO2 cannister round and round round. I know they say “it makes negligible difference” but I NEED NUMBERS DAMMIT!
Ok, brace yourself, here’s some numbers:
For spinning at a constant speed, the weight of your cranks saps no power.
It’s only when you accelerate that the inertia of your cranks makes any difference… but how much difference does CrankPump make?
CrankPump weighs 30g, and its weight is distributed pretty close to a solid cylinder of 18mm diameter.
For cylinders, inertia = 1/2 mass * radius^2 = 1/2 * 0.03kg * 0.009metres^2 = 0.000001215 kgm2
Let’s compare that inertia to pedal weight, to see how many extra grams of pedal weight would give you the same increase in inertia.
Assuming you have 172.5mm crank arms,
For a simple pendulum, Inertia = mass * radius^2, so mass = inertia / radius^2 = 0.000001215 / 0.1725^2 = 0.04g
So CrankPump has the same effect on acceleration as adding 0.04 grams to your pedal weight (that’s less than one raindrop).
I believe he was being facetious.
But the reply he got was awesome!
I second that!!!
It could be all BS but it still would be a great response.
Of course, the elephant in the room is, how many watts is it going to sap spinning a CO2 cannister round and round round. I know they say “it makes negligible difference” but I NEED NUMBERS DAMMIT!
Ok, brace yourself, here’s some numbers:
For spinning at a constant speed, the weight of your cranks saps no power.
It’s only when you accelerate that the inertia of your cranks makes any difference… but how much difference does CrankPump make?
CrankPump weighs 30g, and its weight is distributed pretty close to a solid cylinder of 18mm diameter.
For cylinders, inertia = 1/2 mass * radius^2 = 1/2 * 0.03kg * 0.009metres^2 = 0.000001215 kgm2
Let’s compare that inertia to pedal weight, to see how many extra grams of pedal weight would give you the same increase in inertia.
Assuming you have 172.5mm crank arms,
For a simple pendulum, Inertia = mass * radius^2, so mass = inertia / radius^2 = 0.000001215 / 0.1725^2 = 0.04g
So CrankPump has the same effect on acceleration as adding 0.04 grams to your pedal weight (that’s less than one raindrop).
I believe he was being facetious.
But the reply he got was awesome!
Seriously, did someone actually figure out all of that nonsense? If so, I want to invite you to my next party! I could use a boost of nerd to equal all the sports nuts in the room! How many chicks does that guy get (huge assumption of it being a guy there) spouting that stuff at parties?!! Someone has a beautiful mind!
Years ago I was at a party with a colleage (both mechancial engineers). The wives were gossiping about something and the boys were drinking and telling lies about how great they used to be. Somehow, my colleague was trying to impress one of the non-engineer with his impressive knowledge. I quite respected my colleague at the time, but he said something I disagreed with and we got into quite an involved engineering discussion.
We ended up in his home office, pulled out a psychrometric chart (illustrates the various properties of air) and started pointing and waving our hands about. The other guys in the discussion went quiet while we discussed and worked through the problem, calculators working furiously. Eventually I convinced him he was wrong and I was right and the others were well impressed that either of us could read, let alone understand the psychrometric chart.
We were discussing differential enthalpy of air within an attic in summer, versus the air in the ducts in the attic 
I talked my colleague into understanding that he’d been wrongly designing A/C systems for years! He changed his designs from then on…well, until he left the company and reverted to his old ways. Interestingly, I had a client come to me saying the ex-colleague had designed an A/C system but it was using tons of energy to keep the place cool. I reviewed the design, found he’d done it his old way! I explained what the client should do, they did it and their energy use dropped considerably.
Engineering is fun. I don’t remember rotational inertia formulae off the top of my head, like Damon does, but I still like calculating things. Numbers ROCK! I also remember that my father (NOT an engineer) used to say “Every bit counts, says the old man as he pissed in the sea”
Great idea, if they could have a fitting to put one of these (they’re very small) in there. Or a fitting that was a version of this pump with a lower profile head. In a 30mm spindle especially, there would probably be room to spare. For non-race situations, I really prefer the manual (and repeatable) action of a pump over a single-shot CO2. Because, if your inflation attempt with the CO2 is a bust, you could be SOL and very far from anywhere …
Years ago I was at a party with a colleage (both mechancial engineers). The wives were gossiping about something and the boys were drinking and telling lies about how great they used to be. Somehow, my colleague was trying to impress one of the non-engineer with his impressive knowledge. I quite respected my colleague at the time, but he said something I disagreed with and we got into quite an involved engineering discussion.
We ended up in his home office, pulled out a psychrometric chart (illustrates the various properties of air) and started pointing and waving our hands about. The other guys in the discussion went quiet while we discussed and worked through the problem, calculators working furiously. Eventually I convinced him he was wrong and I was right and the others were well impressed that either of us could read, let alone understand the psychrometric chart.
We were discussing differential enthalpy of air within an attic in summer, versus the air in the ducts in the attic I talked my colleague into understanding that he’d been wrongly designing A/C systems for years! He changed his designs from then on…well, until he left the company and reverted to his old ways. Interestingly, I had a client come to me saying the ex-colleague had designed an A/C system but it was using tons of energy to keep the place cool. I reviewed the design, found he’d done it his old way! I explained what the client should do, they did it and their energy use dropped considerably.
Engineering is fun. I don’t remember rotational inertia formulae off the top of my head, like Damon does, but I still like calculating things. Numbers ROCK! I also remember that my father (NOT an engineer) used to say “Every bit counts, says the old man as he pissed in the sea”
And no boobies were touched that night.
