Do you know of any issues which would arise if I just use high chain speed on a middle gear (my 22 tooth gear for example)? That way I could use the gears with good teeth engagement, would have a small load on the motors and chain, and I would still be able to have the rolling speed that I want. I'm thinking, 2 or 3 (300rpm for simplicity) times the normal max cadence of a human. The chain would move at ~11mph which seems quite reasonable.
That process sounds intimidating and it would probably be challenging enough for me to worry about doing. I think I'd rather not do it just so that problems that my bike ends up having are things I can fix on my own. Learning how those motors work and learning to troubleshoot their problems doesn't seem to be outside of the realm of possibility though.Well, it's not beyond what you'll be doing if you run two motors with one controller--you'll have to do that in order to do so.
(assuming they're not brushed motors).
I'm on an FRC robotics team we work with entry level robotics equipment meant specifically for FRC. We get most of our spur gears from West Coast Products and our planetary gearboxes from Rev which also make the motors we use. Some of these motors are terrifying! We use Kraken x60s and they are hardly larger than the hobby rc motor that I mentioned above, but they're rated for 360a and can put out 7nm of torque. That along with the fact that the ESC is built in and they have very accurate continiuous encoders means they're very capable, and very expensive. They could be worth it to be if I could know for sure that I could keep it cool.
I'm not really sure what you mean, the 22 tooth on the cassette? That kinda defines pretty low chain speed because you can't make the front drive cog (which from your design is separate from the pedaling chainring?) that much smaller than that so you have a very small amount of reduction so unless you are going very fast the chain won't be moving that fast and will be under a lot of tension with those small cogs pushed to their limits to have a serious amount of real wheel torque. If you absolutely will not give on the derailleur it is possible to remove the smallest cogs and shift it over, modifying the mech as needed so you have fewer gears, all on the larger end and all closer to being in ideal chainline. Then with a small driving front cog you can have speeds and some amount of torque.
But the controller itself is also much simpler than a BLDC (brushless DC) controller (which you're already using iwth typical RC motors)That sounds like a challenge.
The Kraken x60 looks interesting, is apparently a low-kV low-rpm type of motor from the first couple results on a web search, which is why it takes such a high current, all relative to the typical RC motors that have a high kV and use thousands of RPM to get the power output they do. So they'll be quieter just because they are not spinning as fast, even if they are still using gearboxes (of which I saw several types specifically made for them, including some that drive small (aimable with a separate servo motor?) caster wheels).
Huh that is interesting, also VESC controllers can use all manner of encoders sin/cos included.
Right, that is clear to me. I just mean that I do not understand how brushless motors work and while it may be within my ability to learn how they do work, I worry that even that knowledge will not let me fix the problems that may come up with that setup. It feels a little too far from what I'm familiar with so I will probably not design around that setup.
You are quite right. Our competition matches are only 3 minutes long. When we are testing our robot for long periods of time, they can be plumbed up to forced air cooling. No water cooling though unfortunately. That's because they're actually outrunners under the ourter cover which I can only assume is cheaper.
I just mean that I will treat my 22 tooth gear as if it were my fastest gear. Then I would adjust the gear ratios or the motor that I eventually choose to go with to make it so that I comfortably reach my design speed in that gear. I would optimize my chainline to use only the 1gear to the 6th gear (22 tooth)
Sorry, I misspoke. The X60 has an absolute encoder, not a continuous encoder. As far as I can tell, continuous encoders do not exist or at least is not a term that is widely used.
endless-sphere.com
Ah. I don't know the terms used for all the various encoder types, but continuous is as good as any for a SIN/COS type, where there are two sensors 90 degrees apart on a ring that is magnetized in a continuously variable pattern of a repeating sinewave of strength/polarity. These may have the same number of peaks as rotor magnets, or it may be more or less than that such that the controller must be designed to do more math to determine rotor position from sensor position.
Ah yeah that works better but I still suggest you slide the cassette over if you can to improve chainline. I mean my rear drive is all bike parts, the rear cog is a standard 58T narrow wide chainring with an adapter to the HG spine. My bikes are very much designed to be bikes and not motorcycles in terms of how I feel when riding them. I don't think the driveline parts really change that but other parts certainly could.
I totally agree, I was browsing for a motor last night and realised that since I am still using a few gears on my casette, I shouldn't have to worry about using as much power as I was asking for. I think looking for 2kw will be plenty since I like the headroom to keep temperatures low.
I also arrived at this conclusion, leaning toward belts but gears are a fallback since I know they'll work. I have used HDT15m belts before but they're just not made for this kind of torque. I'm looking onto other belt profiles, I could probably get away with 5mm powergrip GT3 or GT2. I'm worried about the belts skipping since I'll end up with at least one smallish gear. I might need a tensioner to improve belt tooth engagement. I'm also looking for a place to buy the small front gear that'll drive the chain and be connected to the end shaft of the gearbox.
Yeah, motorcycles mixed with traffic is something I stomach for commuting but wouldn't recommend otherwise. (Honestly, nothing mixed with traffic, while we're at it. Cars just suck.). Offroad is much more fun anyway.
I mostly agree, but that is also my point, launching yourself 1m up on a bike weighing a couple hundred pounds is not exactly safe. But those also assume you have the skill to do those things, my bike is still well more capable then my current skills and that is probably the case for most no matter what you are riding. I enjoy pushing myself on as hard of obstacles as I can find and doing so in a more dangerous way when either way I don't have the skill to fully take advantage of what the bike can do only slows things down since I'm less likely to take risks.That's true to a certain extent, but if EMTBs only had benefits over enduro motorcycles, everyone would take them to Erzberg
Heavier machines, while requiring much more skill, expertise and to a certain extent strength, can cross terrain completely unavailable even to powerful eMTBs. A proper enduro bike has enough power to launch itself onto or over obstacles of 1m height or higher, from no kicker whatsoever, has tyres with enough grip to keep traction during that, has wheels strong enough to absorb the bump and a lot of suspension travel to keep you in control both on landing and at higher speeds. Going lighter means sacrificing all of those things, unfortunately. As long as the terrain you ride through is passable on a lighter machine, though, and you have no ambitions to progress to harder obstacles and steeper climbs, I generally agree that lighter is typically better.
Exactly, and I think we will see more parts like this over time but may be slow. I think though as battery energy density keeps improving this weight range will make more and more sense.
Doing two motors even if on the same shaft with one controller seems more complicated than just using one bigger motor. Thr 83100 motor has some of the best parts available and u can get it unbuilt so can wind whatever kv
Woah, that bike frame looks sweet! I agree with your opinion opinion of using two motors but I was thinking that I would have to compromise if I wanted to get the power I need without a really thick motor.
The motor doesn’t stick out much and not a problem with pedaling
Feerchobby and flipsky have exceptionally bad reputations (they also sell several of the same rebranded motors). How much cheaper does the unwound motor cost compared to pre-wound motor? Have you had issues with QC or with motors being finicky? Maybe throwing a magnet or bad tolerances?
I’ve gotten many motors from them and all are fine. The ingredients are second to none with .15mm laminations.
