Ryokeen

If you discovered this topic just now, there is another good one: https://www.eurobricks.com/forum/index.php?/forums/topic/92099-axle-collection-thread/

@glowytheglowbug most of the outrunner motors are for drones or planes as their nature(outside spinning parts) isn't really suited for vehicles, or if there is not enought space to fit a gearbox. But rpm wise they are also kV rated, means even a 700kv motor will get you ~5.500 rpm. Torque is mostly even higher for outrunners

Don't get you. Their motor/gearbox combo has some pinholes for mounting the motor on a chassis, but the axlehole is the only thing that is driven by the motor and will spin. So that axlehole is your only chance to directly mount a wheel. It's like mounting a Wheel just with an Axle to an PF-L Motor, it won't be mounted long :D Or like in the video from hy bricks that i posted, use lower kv motors(other form factor, flatter and i think called outrunner motors) and don't do any downgearing. With 4 of them you will still have plenty of torque and speed.

@glowytheglowbug But without any form of joints, you would have to "steer" the motors with a wheel. Can't imagine where you would put the pivot point for steering and the suspension considering that the motor+gearbox is at least 9-10 studs long. And as i said, the gearbox only got an axle hole, so you need some sort of wheelhub cause i doubt that you can access the metal shaft on which the axlehole of the gearbox sits. And even then, i would not use that as a direct wheel mount. As the axle/shaft is most likly not that much thicker as the motor shaft, putting significant load might damage the bearings and the gearbox quite fast.

@glowytheglowbug with one motor per wheel ? easy 40km/h. Just an example i use a 3250kv on a 2S LiPo, Gear reduction of 1:5 and (according to zene) 1.65:1 on the diff, that makes around 3k rpm on the wheels. With 100mm Wheels i get easily to around 50km/h. So 7.5k rpm even on regular RC 60mm wheels will get you (theoretically) up to 80km/h. But if you want to get rid of the drivetrains, where would be a gearbox ? or do you mean the gear reduction on the zene motors ? If so, that might get problematic if you want(and you will need it) suspension and ofc steering. As said the zene hubs have a massive pivot offset for the u-joints and mounting a motor behind a wheel hub might not work either as there isn't enough space to fit the motor between suspension arms. Mounting a wheel directly on the zene gearbox won't work as you could only mount it on the driven axle, so only axle to axle hole clutch power holds it. From the motor specs it's a 2.3mm thick shaft, doubt you'll find bigger wheels to mount on that thin shaft.

Great job so far, especially the 5x7 frame. For the A2212 motor mount, i'm not sure if 8:40 is needed or suited as the abs 8 thooth gears are not the strongest. Maybe that changed but i'm paranoid and try to avoid them or use metal ones :D Else i like to have several gear ratio options . But you might consider making that mount as closable parts. So that the gears are sealed from the outside. That way you prevent stones/sand getting in and also make it possible to have some lube in those gears without it flying around.

@glowytheglowbug Ah lol my bad, the rpms are without the reduction, somehow the "out" was missing. But well it's always kv*Volt. They use a 3600kv motor * ~8.2v(almost fully charged 2 cell lipo) =~ 30.000 rpm. If you want to get 4 of them, one per wheel, keep in mind that no motor has exactly the same rpm as another for the same voltage. Might not be an issue with a gyro or even without one, but one thing to keep in mind. Also you would either need 4 esc for independant controll and you need a lipo that can provide enough current. Maybe that helps you: Hy Bricks in wheel brushless Might be the better sollution as you get rid of the 4 drivetrains and get a bearing wheelhub aswell.

Without the 1:4 reduction max rpm(no load) should be around 45.000 for 3s(4.2v per cell) and for 2s 30.000 rpm. About torque, might be enough after the differential downgear, but consider that those motors are mostly for 1:16 cars but with less downgearing. But they claime to be able to move a Daytona at around 40-60km/h

@glowytheglowbug with their planetary gearing or just the motors ? Just the motors: There less than 15bucks

@FriedlS Well your car is pretty light weight so that helps, but i don't see it deforming. I would just brace the upper gear from the other side just to avoid that it might slip out and is lost on the road :D And actually having a cheap to repair point of failure is sometimes not a bad idea.

@NoEXIST well PU+ motors with their useage as gear selector and servo are a bit complicated to integrate as you need at least some logic to interface them. PF motors or in general DC motors are easy as they only require a simple esc but they can only "just" rotate :D Also in terms of power, PF motors are just not good. What 3-4 XL motors can do, one 540er motor can aswell, with at at least 10 times the rpm and it's actually only around the size of one XL motor. Buuut having something where i can just plug in an receiver, a LiPo and motor(s) would be nice. I would not suggest supporting brushless this early, cause those mostly very high(even 1000kv at 2s is almost 8k rpm) rpm need so many special/custom parts(bearings) that those ppl have already a sollution for all the electronics. Then again, the biggest question is, what marked to you want to supply ? If it's only RC car/bike/boat type stuff one esc for "driving" motors is enough. If you want to give ppl the freedom to make tracked vehicles, then it's a matter of, 1. put in 2 esc for "drive" motors (can be hard-coupled by an Y-Cable still) or 2. let ppl buy 2 boxes that are connected one receiver Oh and for that option where the receiver is separate, consider adding a UBEC as those small esc most of the time don't provide much amps(the 2s 20A esc i got only have 1A bec). Best would be 6V and around 3-5amps, so there is enough power for some stalling geekservos.

At least for the ESC input signals yes. Servos could be attached to a receiver directly as the box wouldn't do anything with the signal itself

Oe Motor spinning faster than the other is actually a big problem if you want to couple motors, like one buggy for front axle, one for rear, or just both hard coupled. Also if you physically reverse the contacts the motor will just spin the other way but still spin full power. But if the esc drives them in reverse they will(as an example) spin only at 50% throttle at max.

@NoEXIST Nice update so far. One thing that came in mind was that most esc have some sort of switch for a break functionality. Also a lot of ESCs are asymmetric, means they deliver less power in reverse than they do in forward. So you might have to keep that in mind when choosing esc's and designing the housings

@Brano honestly at this point i think the transmitter/receiver is faulty. Also the ALI-express site seems to contain wrong information. The video you posted states that the transmitter uses AFHSD and not like on ALI FHSS. Also ali states that the receiver got a gyro in it and states there is an lcd display. Sooo kinda sus. Anyways if it got a gyro in it, that can cause issues as some gyro systems not only correct the steering but also the throttle. And if the gyro is faulty, then yea. I would suggest filling a complain on ALI and get a new set, i mean you swapped everything except the transmitter and receiver and checked the manuals. If it still doesn't work chances are high that those parts are faulty. Else you could try out turning off the break function on the esc(the small soldered on lever), but i doubt that will fix anything

@NoEXIST Exactly. You would sell a box that has esc's, lego compatible ports(and standart servo ports maybe) a batterie connection port(a lipo protection is needed then) and input ports for receiver channels. And the receivers are separate. Having the esc's and the receiver separate just opens up a lot of possibilites, not only free choice of receiver. One is then also able to intercept the signals from a receiver and modify them, for stuff like range extensions for a geekservo(signal spreader). Or hooking in an microcontroller and using one receiver channel as a 2 way trigger for some coded signal sequence to servos. That also means your box wouldn't be restricted to rc receivers as any proper pwm input could be used. All in all it would make it way more flexible because you're not limited by how many chanels the build in receiver got or how much ports/esc's are in the box, you just daisy chain them and get more.

Yep Lipo packs have higher discharge rate than single 14500 style cells. Also 14500 are of Li-ion types You don't need BT for that :) just let customers choose their components. The biggest problem i see is just connecting lego motors to an RC system. You can provide a sollution for that problem, or yeah have different versions like with receivers or without. As an example, what if i have a car with propulsion(1 channel), steering(2nd channel), gearbox(3rd channel), a winch(4th channel) but also want difflock(at least 1 more channel). I can't use your product if i can't switch out the receiver and just plug in a servo directly(but it will be powered by your box). I also can't just buy 2 of your boxes cause a single transmitter only binds to 1 receiver(normally). But if the receiver is not in your box, then i can use 2 of them. As i can plug in 4 channels of the receiver to box 1 and the other to box 2. Only need to watch out for the bec, so the receiver won't be powered by both boxes, but that is just a matter of using a cable with only sig and ground. What i'm saying is, don't limit the usecases by trying to make a fixed package for a fixed set of use-cases. Splitting it up gives more freedom to how it can be used and combined, broadening the possible use-cases. But that's just my opinion it's your product after all.

@NoEXIST as a side node, the two 14500 cells will, as other ppl said, give around 8.4v fully charged, that's fine for motors as i think those are rated for 9v. But a lot of 14500 cells are rated only for 10A drain, that could be a problem if you use at leat 2 30A esc. Yes they will only suck as much as the motors need, but alone the possibility that an esc can request more Amps than a battery can provide is not good. That's why most of the time you see high C-Rating LiPos in rc projects. For 2x30A esc you would preferr a lipo with lets say 2000mAh and a 30C-35C rating. But regarding what you want to squeze in and considering the marked you probably want to target, i wouldn't mind if your project was just some sort of adapter from RC to lego. Means have connections for a LiPo(deans or xt60) and input ports for signal cables from a receiver. So your product would serve as an interface between a LiPo and an rc receiver, offering PF/PU and 3-Pin servo connections. That way ppl could also use receivers they already have, switch the channel layout and you save on hardware. One would just connect the motors/servos to your thing, then connect a LiPo and a receiver. Sure not an all in one package, but that way the receiver could also be somewhere else utilizing space. Also regarding GeekServo only, even common RC servos fit quite well into the lego stud space. And honestly if a geekservo won't cut it cause it's to week, you have to go for a bigger servo ;)

@Brano rly weird. As you switched motors, esc and servo, the only constant is the transmitter and receiver. What i've noticed is that first if you use throttle the esc lights up so it get's a signal. After you used the servo, it does not or get random signals. I once had a similar behavior when i used the wrong channel on the receiver. I had a simple power switch attached that can be switched with a servo signal. It behaved very randomly cause i had it on a channel on the receiver that was not actually in use on my transmitter(6channel receiver, 4 channel transmitter). So that or some transmitters have mix modes for tracked vehicles where chan1(throttle) and chan2(steering) are mixed to drive 2 esc. Maybe check if your transmitter supports that and has that enables. Else i could only guess that the transmitter/receiver pair is faulty.

@Brano First i would try to switch channels, just to see if there is anything wrong with the receiver. Then you can check the manual of your reiceiver/transmitter, as some need to set endpositions for an esc. Then there is the possibility of a faulty esc. Might want to post which esc you use ?

Interesting concept so far, i'm just not sure if it's worth to have the battery tray for the 2 14500. As you stated the top part, where the connections are, will slide to give access and the bottom part is the one that has the stud holes. That might make buildings using this a bit complicated as the bottom part is fixed into whatever thing was build and the top part needs to have enough space to slide off and be moved enough so one can acutally access the batteries. Will be interesting to see how you will manage to make a geekservo(or any rc servo) use the same port/s as a control+ motor. From what i know control+ "simulates" a servo with their build in encoder and need hard build limits. I'm not sure if that part of the software is in the motor or the control+ hub/app. An rc servo on the other hand just uses a pwm signal mostly between 1000µs and 2000µs with 1500µs makring the center position(yeah i know some servos have a bigger range, such as the geekservo 360). Or more most RC transmitters/receivers only use that spectrum, nothing more. All the logic on how far the servo need to rotate to reach a desired position is in the servo itself.

@Gyenesvi ah that new one looks nice. I'm just curious how hot those will get as they seem to have almost no cooling. And you're right any u-joint would rub there. So a bug with integrated towballs for more space and a proper cv joint would be neccessary. That leaves us with a new needed hub, a RC car like cv-joint and an adapter part for the male cv to axle form. About the RWD sports cars, from my experiments, a suspension travel of 2 studs, one up, one down, so 2 in total, is possible. I actually have 1 stud of fixed travel in my trophy truck rear axle. It's a live axle but the drivetrain goes down 1 stud and that works fine. It worked okayish with a 5L axle between the u-joints, but had about 2mm of play.

@gyenesvi Yeah but the price is a bit higher for such esc. I mean 90bucks for a 40amps esc isn't cheap. The brushless i use would already get them to their limits. But yes there are better esc ofc, it's just a matter of money you want to spend.

@gyenesvi Only partly true. Brushless come in 2 variants, sensorless and with sensors. Sensored motors have an additional pair of cables that tell the esc the position of the motor. Those are very sensitive to throttle and can be run at low rpms quite precisely. The other type is sensorless, which i use and zene uses. Those "determine" the motor position by some sort of feedback loop over the 3 wires. Those motors have trouble at low rpm because the way of detecting the motor position works better at higher rpm. So for a crawler you either use massive downgearing so the brushless motor can run at higher rpm without moving the vehicle much, or you use sensored brushless motors.

So this is how the 1:8 Hubs look with metal u-joints. The offset makes it very hard to make a stable driven and steered suspension as the upper and lower suspension arms can't be properly connected or will block the drive axle. Cutting the u-joint isn't really an option as that would leave almost nothing of the side that needs to connect to the hub, so the torque applied to the wheel will act on very little material, around 1mm at most. I think to solve that, a custom u-joint and maybe a different hub casing might be needed. If one side of the u-joint would be an axle instead of an axle connector (where you can stick an axle in) that fits through the ball bearings it would be better. Like this, that would solve the problem and also would unify the 1:8 and 1:10 hubs as a normal hex adapter could be used for RC tires and another adapter like the breakdisc with pinholes would work for lego compatible wheels.