Dot Physics

Flywheel in a bike. What is up with the gyrobike?

Posted by Rhett Allain on July 11, 2009
(6)
More »

My friend J sent me a link to this gyrobike (http://www.thegyrobike.com/index.php). From what I can tell, it’s a flywheel that you put in the front wheel of a bike. The site claims that this will help kids learn how to ride a bike.

So, what do I think? Clearly, this is a real product, but I am not so sure how effective it would be. As I mentioned in a previous post, it’s not really about angular momentum that prevents you from falling over. Well, actually I didn’t really say that. I referred to an excellent article on the physics of bicycles, David E. H. Jones and published in Physics Today in 1970 (The Stability of the Bicycle 23 p34-40.) (you can find a link to that article at The Physics and Bicycle page) Jones tested the idea that angular momentum keeps a bike up. To do this, he created a bike with an extra counter rotating wheel. This made the total angular momentum of the bike zero (the counter rotating wheels had opposite angular momentum). From this, he found the bike was easily “ridable”.

i-844655de8761c5ce5ad53a357c126373-jones_bike_bwpdf_page_2_of_7.jpg

So, if reducing the angular momentum doesn’t make the bike more difficult to ride, I would imagine that increasing it wouldn’t make that much difference either. One thing he did find was that the zero angular momentum bike didn’t ride well as a ghost-rider bike. It just fell over. So, maybe the gyroscopic action of the wheel may add to stability in the case of a low mass bike. However, when a rider is on there it might not make much of a difference.

Here is a video of the Gyrobike people testing the ghost-riderability of the gyrobike.

If you want to learn how to ride a bike, I recommend just removing the pedals. This allows a child to learn how steering and balance on the bike works without having to worry about pedaling. This is what other’s recommend.

Further, if you want to make a super stable bike, I have a better idea:

i-84a4fc73c328b94dd0b35aa77e5d8b7f-google_image_result_for_http_farm_3staticflickrcom_2444_3612519899_1139d_15bacjpg.jpg

This biker uses a long pole to help balance. The pole makes the rider have an object with an extremely large moment of inertia. You could do this with a kids bike also, but it might be difficult to pass through narrow openings.

Let me just emphasize that I don’t know the gyrobike doesn’t make a difference, I am just suspecting it doesn’t make a difference. I totally could be wrong, it happens all the time. Maybe the gyrobike does work as a placebo effect.

Keywords: , , ,
(6)
More »

Comments

  1. #1 Chris
    July 11, 2009

    My youngest daughter is now a bike rider, thanks to your blog and the “no pedals” thing. It took a few days tooling around with no pedals, and then, once the pedals were put on, she was instantly riding. It saved me a lot of running behind the bike trying to balance it by holding onto the back of the seat.

    Thanks for the suggestion!

  2. #2 phoebe
    July 11, 2009

    My 5 year old daughter was one of the testers for Gyrobike – believe me, this thing is incredible. She could not get off training wheels, and Gyrobike had her riding in about an hour (and she is NOT coordinated and had acquired a lot of bad habits).

    Contact the company to try it – I’m not kidding.

  3. #3 Rhett
    July 11, 2009

    @Chris,

    I am glad your daughter learned to ride a bike – but I just want to say I didn’t come up with this no pedals thing. I also found it on the internet. I got the idea from Sheldon Brown’s bike riding site.

  4. #4 J D Loyd
    July 13, 2009

    Rhett, sounds like a bike buster mission??

  5. #5 Ron
    August 26, 2009

    In a few days, I’ll be writing an article on the stability of a bicycle, hopefully with the use of Matlab. Just one or two attibutes cannot explain bicycle stability, as found by people who study bicycle dynamics. Anyway, follow my feeds. My blog is here http://cozybeehive.blogspot.com.

  6. #6 randomray
    October 10, 2010

    LOL ,guess what ? David E H Jones is wrong .The real reason is that the wheels aren’t heavy ” massive ” enough and they aren’t spinning fast enough to have enough effect to make any difference . A kid learning to ride , I imagine there is zero effect . Way back in 1910 Louis Brennan built a number of Working prototypes of a Gyro monorail which just happens to use two counter rotating gyroscopes with horizontal axis’s just like bicycle wheels and they worked perfectly according to many sources .As always empirical data trumps theory every time .Frankly a bicycle wheel is too light be a good gyroscope . If you care check this link [:http://www.catskillarchive.com/rrextra/odgyro.Html and [http://www.aqpl43.dsl.pipex.com/MUSEUM/LOCOLOCO/brennan/brennan.htm]

    I just take the kids to a grassy hill where they can mostly just coast down the hill with out worrying about pedaling and tell them if they start falling to steer in that direction . That worked well for my kids and it’s aways good to remember that all children mature at different rates .So if they don’t get it now , don’t make a big deal about it and just try later .”It hurts less to fall on the grass .”