Low KV motor wanted

[John Minchell]

Frank Skilbeck and I are collaborating on a little project. 

Anyone know of a small lightweight out-runner motor with a KV lower than 1000?

We found the 4Max one at 1000 KV (https://www.4-max.co.uk/A2212-13T-1000kv.htm )  but ideally want about half that - 500KV.

 

Low KV motors are available but the weight and size and cost go rapidly north.  So about a 28mm dia can and around £20 would be ideal.

 

TIA John M

[Shaun Walsh]

A Hacker geared outrunner would give you 500KV but they're not cheap! 40g 115W for the A107L

[Simon Clark]

I have no experience with this particular motor, and the info is limited, but might be worth looking at or at least giving Robotbirds a call to see what else they might have

 

https://www.robotbirds.co.uk/mt2808-660kv-ccw-thread.html

 

Simon

[Graham Bowers]

Off the wall comment. Wind your own.

[Don Fry]

Off the wall, someone is building a powered kite. Or small rubber powered old timer. 
I’m tracking a 250, 500 KV motor for a KK Falcon. So it goes nicely on a big, 18”prop. I have candidates, because the motor needs to have weight to balance the airframe. 

[Frank Skilbeck]

1 hour ago, Graham Bowers said:

Off the wall comment. Wind your own.

It's not going to be driving a prop! 😄

[PatMc]

12 minutes ago, Frank Skilbeck said:

It's not going to be driving a prop! 😄

Does that matter ? Rewinding an existing motor of the right size but higher KV with more turns of thinner wire would not be that difficult.

[John Minchell]

Pat  not difficult for you maybe, but too much hassle for me. 

An easy off the shelf motor is what I am after.  Also that makes it repeatable if anyone else wants a kit of parts to build one.

[Chris Walby]

Can't you just run the ESC at 50% or what you want, just limit in the TX max throttle setting?

[Frank Skilbeck]

1 hour ago, Chris Walby said:

Can't you just run the ESC at 50% or what you want, just limit in the TX max throttle setting?

Yes, that's plan B, but a lower Kv motor would be a neater option, but we couldn't find one so thought we'd ask if anybody knew of one.

[John Minchell]

I've been donated an AXI 2217/20, 840 Kv motor to try out.  So I'll make a test rig and do the measurements.

Thanks for your suggestions.

John M

[Phil Green]

>It's not going to be driving a prop

 

Wind generator?     🙂

[John Minchell]

Nope - an on board glider tug tow line winch drum to stop hooking the tow line on fences and hedges when landing. 

Wind the line in after the glider unhooks. 

Pay it out again after landing, when taxiing forwards to hook up the next glider.

[Chris Walby]

As motor speed is dependent on KV times voltage, how about just reducing the voltage...? 2S or even 1S...? 

[kc]

Reduction gear?   Maybe a friction drive so there is some give if the line snags?

[Denis Watkins]

Good idea KC

£5 off ebay, many speeds and voltages

 

Edited February 27, 2023 by Denis Watkins

[kc]

Well actually Denis I was remembering how old record player turntables worked - a rubber idler wheel went between motor spindle and flywheel ( turntable) to reduce speed a lot.   Didn't need too much accuracy in alignment and could slip if anything jammed.

 

 

[Phil Green]

21 hours ago, John Minchell said:

Nope - an on board glider tug tow line winch drum to stop hooking the tow line on fences and hedges when landing. 

Wind the line in after the glider unhooks. 

Pay it out again after landing, when taxiing forwards to hook up the next glider.

 

I did a 'layerer' for a club in Switzerland, their tug is in constant use

 

 

[Outrunner]

20 minutes ago, Phil Green said:

I did a 'layerer' for a club in Switzerland, their tug is in constant use

 

Nice one Phil, what does the servo on the end of the shaft do?

[Phil Green]

I think its a brake to stop it unwinding, I never saw it in the flesh 🙂

Edited February 28, 2023 by Phil Green

[Frank Skilbeck]

2 hours ago, Outrunner said:

 

Nice one Phil, what does the servo on the end of the shaft do?

 

There's a pin that runs through the center of the  spindle, the tow line is fastened onto that, with the line fully out activating that servo will pull the pin and release the line. Essential if the glider goes AWOL and can't release, happens a few times at most meetings that for some reason or other the tow line won't release from the glider.

[kc]

Very ingenious and very nicely made.

[Flying Squirrel]

Would a continuous rotation servo work in this application? around 45-50 rpm?

 

https://www.modelshopleeds.co.uk/catalog/product_info.php?products_id=19177

[Geoff S]

1 hour ago, Flying Squirrel said:

Would a continuous rotation servo work in this application? around 45-50 rpm?

 

https://www.modelshopleeds.co.uk/catalog/product_info.php?products_id=19177

 

That would be something like a sail winch used on model yachts.  They can be quite expensive but the ones for larger yachts are also very powerful.  I'm sure one would do the job of reeling in an unloaded tow line but some arrangement might be needed for emergency release.

[Max Z]

Have you considered using a small stepper motor for this application? You will need a driver (a A4988 for instance) and a specially programmed arduino board to convert a regular Rx signal to a speed regulating input to the driver, but it will have the advantage of low rpm's with maximum torque, and the possibility to control the speed of the reel depending on the length of line wound (approximately, based on the revolutions count) to slow it down when approaching full retraction.