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Need some help on RC motor setup for cable drive system

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I tried looking for RC specific groups but they seemed inactive if anyone has a better suggestion please let me know. If figured a forum of engineers would be able to help!

I want to have a carriage driven by a pulley on a cable or rope (550 para), I have the carriage design, arms and motor mount printed and tested with some old quadcopter parts I had laying around. Problem is the only motor I have is 2605 kv brushless so the thing either screams or doesn't move due to torque constraints.

I am pretty familiar with driving brushless motors with ESCs from a flight controller but other than that I am kind of clueless as to what motor I would need for this purpose. Maybe something related to combat robots that is slow and torquey? I have looked at the car brushless motors and they are still 1500 kv which is still moving really fast.

I have no problem going brushed or geared I just can't find any information on those. I think maybe because in the RC community they are antiquated at this point? Not sure, just trying to figure out how have a slow motor controlled by an RC transmitter! I didn't think I would be this lost lol.

Thanks for any information you can provide,

Elliott

Have you considered a 12v gearmotor? I use them for RC in conjunction with reversible brushless speed controllers all the time.
There are two sizes I think might fit the bill for you.;

25mm diameter ones such as this:-
https://pulsar.ebay.co.uk/plsr/clk/0/SADS/9?pld=%7B%22mecs%22%3A%222535516647249e541e69a4dd42c290d90b1c66efc74e%22%2C%22enc%22%3A%22AQADAAAC8BkojIFHYtWT%2BANpG6F7t2GSJrdGvXyLywIf2DAeizBIdYfpYJlCalmcXXoShwbkB27EI0jbXWm4cWEzZKZV3BkHfbdPuXHDcwjaidtx8q%2BJAOwjcq82eadwpaAzC8A42T1yxfpQ4snUvTY6VxtDtvzLQo8DWWWbfr%2BpBLxR0iIAjo0k08n5WE2uTxFUqpGQNwmCnE8fH9l1e7yt6yekgpIgpw6h1Di7xUNuZpgt76O926MV7GlhLVaD7tbeNPD7%2BuwSyVtguNyD%2B2KMQTyN4Eg1LO0ENLa4lS6RlmXaxtflu1SewTRyL1j3xxqVwsgaVTaRLb89IixJxhVve0Vqz%2FrPwWbmbKKWPAOQMNk3KgrLzdoshZ%2F%2Fzw4%2FB%2FjQk08%2BK0hF9oVzjOCBte2COnwj6YbBvN2PE%2FSC43D%2F6hfQC0X4El6FHIa5a9678MKlsBCYC9oJ2w51PRVpHYSJ7rIasr5ZltFNBNIe1%2FAaPC7qm08ScAZ2BRZM21Isl3%2F%2FKLQHWsgHowggjnF%2F7%2FA%2FwWQC3wGTMEEYyFLfokOMAJ3wz1jjVziL5Gjo6H97i6rJMXIAPmxaOrxepnk8blJ56FLcR79jH8OnZQHmMg%2Bn7CLb9iMuqoqW3ix0eTHt%2BSadiQsTFr3rFbZKf3QR3KjBcMCaObqAEKYEkqLcefGer3RVf1hHtReyqAWfkKU0eLWlpFvLRsANIi4wkDstlYBe2%2FAkVzZHHJESCrmF%2B%2FIGzqQmU7OSeGWBNuN4Ciq7bn40HuYsKVuAGwxSaifC7Czj%2BI6gbtoiRU1sZxJhxaGLIeO7r2qMH0mwLA3h7n10sGSx11z1tvCId9R6J2PvPUyG940bBwN4Je20B3Be7ih3YQIynnSAjsJnT9OprpU9KNSI2C4iL2hz8wIG75457gfR6zE7SxIs28K%2FFo9DaIcv10E%2BV3qlqGE%2FZE1ET4nVTllDNPvAgsGk82%2FIaqfq3zOiISpxdhxmjReZr%2BpdYnJkQkxyxSeO%22%7D

and 37mm diameter ones with a bit more grunt such as these:-
https://www.ebay.co.uk/itm/12V-200RPM-Gearbox-Replacement-DC-Gear-Motor-37mm-Gear-Box-Motor-High-Torque/182827528778?hash=item2a915eb24a:g:I3MAAOSwhHlapHFs:rk:2:pf:0

Either one comes in a range of gear ratios though the vendors usually state it in terms or rpm on the output shaft.

One of the things to look out for is that your speed controller gives full power in reverse... many of the don't (20% speed in reverse is common) on the assumption that they'll be used in rc cars and boats where reverse needs to be done slowly.

Colin

Thanks for the suggestion! I ran into these econ gear motors: https://www.servocity.com/485-rpm-econ-gear-motor

I modeled in a mount for them as a test and they work great except that I am running on 2S because of a low voltage ESC. I'm trying to track down a low cost ESC for over 12V but it seems like it's a bit tough. Thanks for the links, I'll check them out!

You should check out hobbyking... I used to buy rc parts from there all the time. They have USA warehouses for quicker shipping, and a ton of choices of esc's that can handle higher voltages.

hi, I would suggest using a straight stepper motor. Plenty of control schematics online if you look. I use one for binding fishing rods. it simply sets the number of bindings and speed and away i go, you can also use Arduino boards that have inbuilt stepper drives and write code to set speed and such, even link them to buttons(i.e. like a button auto transmission).
https://www.jaycar.com.au/stepper-motors-and-their-driver-circuits/p/BM1510
This is just one i quickly googled

Thanks for the suggestion, I haven't found anything about running a stepper on an RC transmitter with the analog output. I have seen people post it working on youtube but nothing in the description with no reply in the comments. I am working on figuring it out now. Thanks for the link I will check it out.

k. i see a lot of suggestions requiring motor-drivers for the motors in question. why not just source a used wiper-motor. they are 12V, geared, have decent torque, are cheap, and their speed is regulatable by adding a potentiometer, and playing with the voltage. i used one recently to make my hand-metal-saw, saw automatic. see my things. grtz.

I think the wiper motor may be too large for my application. The whole carriage is less than 140mm large. Also i will be controlling it with a rc reciever which i think will require a motor driver anyway, i think please correct me if im wrong on both accounts.

ok. if ure apps torque doesnt exceed pulling half a bag of sugar over a table,(450-500gr) u can both use
(1)ure current brushless motor, but you would need to gear it, about a 200:1 ratio, to be applicable on the lowest remote throttle speed.
(2) as any average 3d printer stepper driver up to 1A.
the brushless option would be the most dangerous as it would still go quite fast, and have decent torque.(1kg for your BM @12V&200/1gearbox)
Since the whole carriage is 140mm length, i suggest an (1)Ardu Uno, a (2)Uno cnc driver stepper expansion, (3)a stepstick driver and a (4)1A bipolar 4lead stepper (nema17 class)
ure rc reciever gives out PWM signals, and there are a couple ways to Rome when one considers going about translating your Recievers Tx output, into regulating a stepper. search online for RC controlled stepper, find your closest match, and monkey-see-monkey-do the same.

Thanks for the tips, I eventually built this without knowing this existed...Oh well it's much cheaper. Looks like they went the brushless gimbal route as well you can see a turnigy gimbal motor in the kickstarter picture not sure how they are getting the torque out of the brushless motor my ESC doesn't allow for this.

https://www.kickstarter.com/projects/1332617026/wiral-lite-the-easy-cable-cam-for-impossible-film.

I may try the stepper route again.

hi, eh not neccessarily, just found THE instructable, that i learned from, back in the day. https://www.instructables.com/id/Brushless-Gimbal-with-Arduino/
A BLM or Steppr are basicly the same motors. A BLM actually resembles more to an industrial 3 fase ACmotor.
The point is that it is a question of regulating pulses.
The more steps you define in the firmware, the more accurate the BLM is, the smaller steps it takes, BUT the weaker its torque gets.
Defining less steps in the firmware/controller makes the BLM take bigger steps, but with a higher torque.
It all depends on how many coils you power up and for how long. Pulse With Modulation.
If you got time you can research and read the road Alex Moss took with his simpleBGC.

Comments deleted.

NC20 gear motors would actually do the job quite good, it's easier to control. The brushless gimbals don't have much force (the NC20 doesn't have much force either, but in might run much smoother).

Thanks all for the help on this. I think I got something that should work decent. I tore apart an old budget 3 axis gimbal, the motors were brushless (so not that old maybe 2 years), I connected the gimbal motor to an Aerostar RVS esc and a 4s lipo and it works pretty well, maybe 50 rpm on the low end. The motor stutters a little at the start, only sometimes and then smooths out after that. I think it could result from just a temporary wiring situation I did not solder them on yet. I will have to redesign the carriage for the new motor. The form factor on the gimbal motor leaves a little to be desired as the front mounting screws are M1 but I think I should be able to get it to work with a printed cowling. One flip of an accessory switch on the transmitter and it goes in reverse! I think this should work great to move the carriage up and down the line.

Thank you everyone for the insight in motor control saved me quite a bit of money trying to piece together a solution. Although I didn't commit to the geared DC path I bought all the parts to control them in the future as a cost effective tinker kit. Hopefully I'll look at paper printers and toy cars differently in the future!

Don't use the brushed gearbox on something else... at least not yet. Maze is right... a problem with brushless position control (aka brushless gimbal motors and the algorithm used for their control) is known for having very weak torque. Depending on your application they may work fine, but if there needs to be aggressive motion, heavy loads, impact loads, etc... brushless may let you down.

Yeah I'm running into that problem now, I had the gimbal motors ripped off the old gimbal and printed a new version. Everything is working 10 times better than I expected except the thing cannot get through the initial torque to move the carriage from a resting position. It makes tones and won't move the carriage until I give it a little push forward and then it takes over and runs the rest of the line perfectly.

I'm not 100% sure if the motor is good or not, this is one I have been using for testing and I did spark it accidentally when I was dead bugging it before I put it all together (it was late, I was tired, the moon was in new phase...you know the usual excuses).

I think I'll give a different motor off the same gimbal a go, hopefully the motor is the problem. If not I have some L298N coming in the mail and I will try to track down a gearbox motor.

Hi,

For low KV brushless motors check out this site: https://alienpowersystem.com/
They make motors as low as 60kv. As people said before brushless gimball motors are good choice too and probably cheaper.
You can easily control brushless motor ESC with PWM signal, all you have to do is to connect servo tester to your speed controller, then desolder potentiometer and you have 3 pin PWM input.

Awesome! Thanks for the suggestions, I'm looking into how I can get my hands on some BLDC gimbal motors.

I agree a brushed gearbox is simplest, however there are low kv motors out there... particularly for brushless gimbals. That said brushless in general is more prone to problems when it comes to implementation. Otoh, a properly setup brushless is maintenance free compared to brushed... so depends on what it is I used for and how often it is used. For something that will see repeated daily use, investing time to design a bldc setup that works may be worth it.

On a side note, I used to be active at rcgroups when it was a pretty big thing. Are they getting dormant over there? Sad if they are... the power system sub forum was a goldmine of info for me when I was learning how to rewind motors and design power systems..

Thanks for the tips, I found a setup on gimbal motors that might work pretty well. I can't seem to find affordable gimbal BLDC motors in the US though, I'll do some more poking around, otherwise I have an older 3 axis gimbal that I programmed for a stabilizing stick instead of drone mount, I could hack that apart and see if they are actually gimbal motors and not regular brushless. I had to reprogram the board on that to invert the mount and I really don't want to have to do that again anyway lol.

Thanks again for sparking that thought in my head I appreciate it!

I'm not sure about all the different RC thingiverse groups but I tried to search RC in the search field and all the ones with many members only had a few topics with no responses. But this is thingiverse so the search engine could have lead me astray!

Failing finding a gearbox, I would use one of the lowest KV motors I could find and print/build a belt drive for it, or do a worm gear drive, lots of reduction but reasonably simple to build.
Best option for that though would be a stepper motor, also fairly simple to drive and setup for smooth movement, with tons of examples on the net.
Depending on the size you're using, you could also use a car window winder motor, although they tend to be big, but there are also a lot of small geared DC motors available online for much less than your 2605 brushless.

Thanks for the help! I looked around a bit at the geared DC motor option which looks promising. It looks like I can just drive them with a simple code from Arduino and a L298N H bridge, I ordered some bridges just to have as back up if I can find the right geared DC motor for the application.

I like the idea of a stepper motor but from my research it looks like a big deal to get it to forward/reverse with an RC transmitter at least with a stepper the size I would need. I have been playing around with a small uni-polar 28BYJ-48 stepper that would work well for size but getting it to respond to digital input instead of analog has me stumped.

I think the problem I am running into most is the form factor I need for the project.Smaller is better and torque is better lol, two things that never really match up. I'll keep trying the stepper and geared DC angle!

Glad I could help. Ironically enough, if you're reading an RC signal, the mapping to make the DC motor reverse etc. is much the same as the stepper, the only difference being that you would change the PWM to step frequency pulses and change direction on the stepper driver chip based on the length of the PWM pulse. I personally prefer the DC motor option for what you are doing, because they're a lot smoother than the steppers from the camera's perspective, if you don't step absolutely smoothly, the camera tends to pick up on the pulses and you can see it in whatever footage you're taking. If you need some help with the coding, PM me and I'll cough something up to get you going.

Yup, you sold me on the DC motor route. I can model up a new carriage design for the motor mounts once I find a geared motor that would work. The circumference of the drive pulley is 87.96 mm so I think anything over about 60 RPM should work pretty well. I'm thinking I will mount a 2 axis gimbal to the carriage so it should help with any jittering or stop starts, I have a 3 axis somewhere but I would like it to be as smooth as possible if other people want to print it out and not use gimbals.

Thanks again for the help, once I get some parts I might have to take you up on the coding help offer. I'm ok with nuts and bolts...not so much with the 1s and 0s.

hi have you tryed your local rc shop for addvice i use wheelspin models in cannock for my rc bits and addvice

sorry just found out your in the usa but still try your local hobby shop
mike

Thanks for the suggestion, I've been to my local a few times but it's more of a "D&D, Magic and one shelf of RC parts" kind of place. I may try again though for this project maybe they will have something! Never know, until I go.