Wireless solenoid bicycle brake project

Discussion in 'The Projects Forum' started by Lloydcr, Oct 27, 2014.

  1. Lloydcr

    Thread Starter New Member

    Oct 27, 2014
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    This may be a long shot, but I was wondering if this would work:
    I wanted to create a wireless bicycle brake, with a button on the handlebar to switch them on.
    I read that the braking force of bicycle brakes are around 5n. If I used the internals of an RC car and replaced the motor with a 12v 5newton pull solenoid (to connect the brake cable to) and then connected a 12v battery, would that work? Or would the 12v running through the RC car's receiver just break it's components?
    Someone please tell me if this would work or if not, another way it could be done.
     
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Why wireless? Do you want all on / all off? Not a fun way to bike. Braking is a delicate activity with lots of training - training that an experienced cyclist or driver doesn't even realize he developed. A combination of force and feedback sensing through the brake pedal or lever. As for your next question, how to do it better? Well, there are many but complicated methods.
     
  3. Lloydcr

    Thread Starter New Member

    Oct 27, 2014
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    I knew someone would mention this, I didn't want to come across as a kid on a BMX. But I would not use the brakes for riding from A to B. The sport of freestyle BMX is based purely on doing tricks, so yes I would want the brakes to be on/off. Also I want them wireless because there is a trick called a barspin, where the handlebars spin the whole way around and the brake cables often get tangled. If they were wireless I would not have this problem.
     
  4. wayneh

    Expert

    Sep 9, 2010
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    Are we to guess which receiver you are talking about? I'm guessing there are some 12V systems out there that would be fine. I'll further guess that you'll need to add a MOSFET switch to handle the current flow to your solenoid. That's guessing that a toy may not be designed for enough current to drive your solenoid.
     
  5. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    why do you want to re-invent the wheel, if it ain't broke, dont fix it.
     
  6. Lloydcr

    Thread Starter New Member

    Oct 27, 2014
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    Alright, I'm guessing the RC car I have wouldn't handle 12v, how about buying a transmitter and receiver? like this one: http://www.amazon.co.uk/315MHZ-Button-Wireless-Transmitter-Receiver/dp/B00HG7I9F8 would that work?
     
  7. Lloydcr

    Thread Starter New Member

    Oct 27, 2014
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    Yes but there is a problem/annoyance which I intend to fix...
     
  8. wayneh

    Expert

    Sep 9, 2010
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    That could be fine, because the power to operate the solenoid can be isolated from the power for the RC parts. You're planning on a 12V supply, right? If you need to bring down that voltage for the RC parts, you could use a simple voltage regulator to do that. Or just buy the 12V RC kit if you don't want to mess with it.
     
  9. alfacliff

    Well-Known Member

    Dec 13, 2013
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    on off brakes mean a lot of "stoppies" the staple of the cable tv joke shows. also known as the "head plant" when you lock up the front wheel.
     
  10. Lloydcr

    Thread Starter New Member

    Oct 27, 2014
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    Yeah thanks, I think I will just buy the 12 RC kit when i have some spare money, haha. Also yes of course, would this be suitable or am I being stupid again? http://www.cameras-cctv.com/Battery_Pack_blue_12V_Rechargeable_and_Mains_Charger
     
  11. Lloydcr

    Thread Starter New Member

    Oct 27, 2014
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    As I said before... BMX bikes are used for tricks, therefore most only have a rear brake, some are even brakeless.
     
  12. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Ok, your RC stuff will work and we can help you modify that stuff. You just need an electric brake that will fit your space and weight limitations. Then you need a battery (both on the front fork). Control can be wireless but power by wireless is not ready for prime time (at these current levels).
     
  13. wayneh

    Expert

    Sep 9, 2010
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  14. Lloydcr

    Thread Starter New Member

    Oct 27, 2014
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    Alright, I'm just going to post a loa of links to everything I think I need and that should clear things up.
    Solenoid:
    http://www.amazon.co.uk/gp/aw/d/B00HR8FDXW?pc_redir=1413731768&robot_redir=1
    RC receiver and transmitter:
    http://www.amazon.co.uk/gp/aw/d/6040387718?pc_redir=1412463379&robot_redir=1
    Battery:
    http://www.ebay.co.uk/itm/like/3209...3=1&ff11=ICEP3.0.0-L&ff12=67&ff13=80&ff14=108
    I shall then use some 2.1mm jacks to wire to the receiver and battery to enable me to charge the battery with this:
    http://m.ebay.co.uk/itm/400792649782
    I think that's all I need, really. I only intend to use this for a rear brake and will figure something out in terms of mounting it to the bike and attaching the solenoid to the cable.
     
  15. RichardO

    Well-Known Member

    May 4, 2013
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    Some things to think about:
    I think the battery pack might be hard to mount because of it's long thin shape. You may want to consider one that is more cube shaped.

    The battery is going to be heavy. This requires a very strong mounting method.

    Since the bike is used for tricks, there will be a lot of inertial forces applied to the battery mount. This makes the strength of the mounting scheme even more important.

    I have not run any numbers but my gut feel is that the solenoid is not big enough. Background... I have probably squeezed a (road) bike brake lever millions of times and have some feel for how hard I have to squeeze. :D

    I think I have seen bikes that activate the front brake through a mechanism that allows the fork to rotate freely. Maybe you can do something similar for the rear brake. No electronics needed.

    You might be able to get rid of the wireless requirement by using a slip ring to connect the signal from the brake lever to the solenoid.
     
  16. Lloydcr

    Thread Starter New Member

    Oct 27, 2014
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    Wow, well actually, I have a large pocket in my seat which the battery should fit inside, and the rest of the parts, I should be able to mount underneath the seat somehow; something I'll have to think about!
    I was worried it wouldn't be big enough too, but apparently the force of brakes is around 5n, and that's what the solenoid is quoted to have the force of so hopefully it should work.
    And another reason I wanted to create something wireless is to eliminate the brake lever. This is because there are many tricks that involve letting go off the handlebars and sometimes, when grabbing hold of the bars again you can catch your hand on the big lever. I think I button would be great as it would definitely not get in the way.
     
  17. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Wait a minute!!!

    So you have a need to get rid of brake cables so you can do a bar spin but now you can put the battery under the seat?

    How will you get the power from the battery to the solenoid on the front brake without wires? Signals can be wireless but power, not so much.


     
  18. Lloydcr

    Thread Starter New Member

    Oct 27, 2014
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    I've said twice now, most BMX bikes only run rear brakes.
     
  19. Sensacell

    Well-Known Member

    Jun 19, 2012
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    My front teeth fell out just reading this thread.
     
  20. wayneh

    Expert

    Sep 9, 2010
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    That solenoid needs ~1.2A as far as I can tell. So it'll put a pretty big load on your batteries. The cells will need to be AA equivalent or bigger. I don't think a AAA-equivalent can cut it.

    The pull length of that solenoid is just 1cm. Is that enough? If you need a longer pull, you'll need to lever it up and that will require a larger pull strength.
     
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