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Hey I'm trying to build some magnetic bike brakes for my GCSE project, if you could take this survey so I could get an idea of my target market and what you care about I would greatly appreciative, it is early days and this is just a simple survey so please tell me if there are any improvements I could make.
https://www.surveymonkey.co.uk/r/MJ5PMCX
Many thanks
Henry
Done.
You need to work on:
spelling
all of your questions are ‘leading’ in that you ask if something positive would be good. The answer, of course, is ‘yes’.
Its a a nice idea though - magnetic brakes on a bike.
If you want to make an effective magnetic brake then look up electric motor braking. That is how industrial machines are braked (friction brakes are unreliable and messy) and regenerative braking on electric cars works.
Also in response to one of your questions heat does affect anything magnetic and will cause magnets to loose their performance. In order to brake you will be converting kinetic energy to another form in some way, eg charging a battery or heat. If you get a DC motor and then connect a resistor across it and use it as a brake it converts kinetic to electric and heat and then all the electric ends up as heat in the the resistor.
Done.
Would these be eddy current brakes? Braking surface (medium?) wouldn’t need to be steel if they were, just something conductive. Very very reliable and often failsafe. Lots of fairground rides use them.
Look up electric retarders https://www.telma.com/produits/fonctionnement
Spelling, grammar and consistent capitalisation.
A magnetic braking system would mean that the heat outputted wouldn't affect performance, does this sound like a helpful thing?
Really needs rewording completely. But performance needs defining (see below)
Would you be okay with the fact that a magnetic braking system is heavier than other methods of braking?
Your questions need some sort of reference ... how much heavier vs what type of braking?
You didn't mention what you are trying to solve or how you define performance*.
You infer brake fade but haven't asked if this is a problem?
I appreciate that at this point you don't know how they will perform for a given weight but you can ask.
I'd also suspect that your market may end up being specific bikes (e-bikes*) but you didn't ask what type of bike.
Performance
Stopping power ... Well 200mm rotors on 4 pot's ... I'm not sure we need more unless we make bigger and bigger tyres but 220mm is only a tiny weight difference but how much better % vs how much heavier %? (i.e. a 20% heavier brake giving 40% more stopping power)
Modulation ... probably the most important if you don't care too much about weight? Would the user be able to tune the modulation?
Fade ... probably important sometimes and probably people who care less about weight?
Altitude and Rain?
What are you doing to do with the excess energy? Can you dump it into a battery?
You haven't asked about maintenance costs. How much do people spend on new pads/rotors?
Done, might be useful for high wear conditions. Motor vehicle brakes may go that way to reduce particulates.
You infer
No. He implies, you infer
OP - please go read this.
Thanks Brant, looks interesting, just ordered
Done. Good luck with the project. And as mentioned go and look at the vertical drop fairground rides. They use Eddy currents as a failsafe mechanical braking system which require no power.
You'd need to dump a ton of heat. Probably a few kW. Think about a 1kW electric fire then imagine having one of those on your bike as you come dowb an alp.
Hybrid cars have real brakes too precisely because you can only use electric braking up to a point.
But that's probably not the point of this exercise, so I'd say don't lead people with he questionnaire. An idea needs to be accepted because it's a good idea, not because you want it accepted.
You’d need to dump a ton of heat. Probably a few kW. Think about a 1kW electric fire then imagine having one of those on your bike as you come dowb an alp.
A friction-based system manages to dump the heat coming down an Alp, is a magnetic-based brake going to have to deal with more for some reason?
Well that's a good point, that I just thought of too. But perhaps the heat being dissipated into something very thin and flat is able to lose heat to the atmosphere quickly enough. But for hard stops from speed that don't take very long you have the heat capacity of the mass of the materials to work with. That's how you can do an emergency stop in a car without boiling the brakes.
So maybe with a big enough heatsink you could manage it... dunno. But perhaps there is some other limit as I cannot imagine a magnetic brake causing as much retarding force as friction pads. Might do a calculation later.
The moving conductor could easily be a disc and the magnets mounted in a caliper, giving similar heat dissipation properties to a conventional disc brake. I confess I'm also pretty dubious about the amount of retarding force relative to friction braking but I don't know much (anything really!) about the subject so maybe I'm wrong about that. The braking force available would also taper off as the conductor slows so they'd be cock-all use for Trials riding (or even holding your bike on a slope at all!).
Done! Questionnaire read more as a sales pitch than a research document. I left you a comment about lever feel for your consideration. Good luck with the project, and don’t be disheartened by any criticism. It’s all constructive and if you can take any of it on board, it could lead you to a better outcome.