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RON
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Joined: 12 Jun 2017, 15:09
Location: Stokesley North Yorkshire

Help!

Post by RON »

If you need any help whatsoever then just let us know, Don't be shy. The members of this forum just love to help each other out
G0MBV Class A Radio Amateur, North Yorkshire
Tigerman01
Posts: 10
Joined: 17 Feb 2018, 14:24

Re: Help!

Post by Tigerman01 »

Hi Ron. Can you tell me why when I leave the site I am automatically logged out even though I tick the remember me box and don't delete cookies?.
Mike.
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RON
Site Admin
Posts: 613
Joined: 12 Jun 2017, 15:09
Location: Stokesley North Yorkshire

Re: Help!

Post by RON »

Hi
It’s more than likely something in your browser settings.
Sorry I can’t be anymore help.

Ron.
G0MBV Class A Radio Amateur, North Yorkshire
Tobe
Posts: 665
Joined: 16 Feb 2018, 06:19
Location: Varberg or Stockholm, Sweden

Re: Help!

Post by Tobe »

Many browser have in setting an option for resetting passwords and / or logging everytime the browser is closed down. Look in settings/ properties and the advance section and hopefully you will find. Suggestion is to try a different browser
Cheers,

Tobe
Nick M
Posts: 92
Joined: 19 Dec 2018, 20:39
Location: Camberwell london

Re: Help!

Post by Nick M »

Hello All

Bit of a weird one - but I know that you will have (multiple) useful suggestions...

I'm building a marble run that has to run fairly continuously - any genius ideas about an electric motor what will last?

The way of hoisting the 2.5 cm ball bearing is a bicycle wheel (large) which picks up the ball bearing on a magnet. This is 'prised off at the top of the arc

The drive at the moment is an electric drill / screwdriver with a 1 cm rubber cog which rests on the rim of the wheel.

This works well - but I need to run the run the marble run 12 hours a day for about a month

(Background: I'm part of a volunteer group that puts 'installations' of vague engineering interest at Denmark Hill Station (in London) - I posted a video of sit up Santa automaton in the Covid thread before Christmas)

I tried an old 12v motor - geared - from a rc paraglider - must have been some time in the 90s. Worked if it runs fast but not enough torque when run at the right speed to allow the marble to be picked up / released

The screwdriver has to run fairly slowly

Would prefer to keep a drive on the rim of the wheel rather than use a chain on the cassette - ie like a bike

So - would the screwdriver last me a month before it burns out?

Alternatives?

Not a mode zero / rc post - apologies - but know you will know the answer - I'm trying to install it (on my own, as exercise, socially distanced, etc) in feb
Nick M
Posts: 92
Joined: 19 Dec 2018, 20:39
Location: Camberwell london

Re: Help!

Post by Nick M »

Marble run centre section



-----------------------

Nick I've moved your MOV file onto YouTube to keep file size down on the forum - Mike_K
MaxZ
Posts: 330
Joined: 31 Jan 2019, 11:48
Location: Boskoop, Netherlands

Re: Help!

Post by MaxZ »

Something automotive, like a W.Wiper motor or a cooling fan motor? They are 12V and should be built to last......

I love marble runs :D

Cheers,
Max.
Martin
Posts: 744
Joined: 16 Feb 2018, 14:11
Location: Warwickshire

Re: Help!

Post by Martin »

What sort of RPM does your drill chuck run at? Probably in the 1000 to 2000 range? Do you want to stick with the same size (about 1cm diameter) drive wheel?

A Nema 17 stepper motor, as used on 3D printers, should be fast enough, provide sufficient torque, and it has a ball raced shaft, so it should last for ages, providing it doesn't get wet. There's only one moving part (the rotor) in a stepper motor, and no brushes or commutator to wear out. They work at any speed from stationary, up to a few thousand RPM. They produce maximum torque at low speed, and the torque falls off as the speed rises. You need higher drive voltages to produce more torque at higher speeds. The driver boards have a little pot, or other means, of setting the maximum current - and you need to set this below the motor's maximum rating or the motor can overheat and burn out. Unless you need the full torque the motor can produce, you can set this maximum current much lower than the motor's rating - the motor will then run very cool.

They're roughly cube-shaped - about 42 mm square, and a bit longer, maybe 48 mm, depending on which one you get. The length doesn't include the output shaft - 5mm diameter, and sticking out about 22 mm. There's a flat on the output shaft to tighten a grub screw against. The motor has 4 convenient mounting holes on either end, threaded M3. Look on the web and you'll find lots of sellers, drawings, different types (the longer ones have more torque, but if you don't need it, the shorter 'pancake' ones are smaller and lighter).

Only problem is, you need a driver board to drive them and set the desired speed - you can use an Arduino, or similar to produce the step pulses - and you'll need a driver board to amplify the pulses to provide higher voltage and current capacity. There are loads of very cheap driver boards, because, as I say, every 3D printer uses 4 or more such motors and drivers. You can also buy gadgets a bit like a servo tester, with a dial to adjust the speed.

Depending on the speed and torque you want, a 12V supply may be okay, but if you need high speed and high torque at the same time, then a higher voltage supply - up to about 48V, is better. High speed in Nema 17 terms is anything above about 750 rpm. You'd do better at lower voltages by running the stepper motor at half the speed, and doubling the diameter of the drive wheel - this would also reduce the wear on the drive wheel and motor bearings.

You can buy the motors and associated mounting brackets, driver boards, etc from places like Polulu, or Ali Express. You can probably buy everything you need from Ali Express for £30 or so - and maybe double that if you go to a more local supplier for faster delivery and better support.
Spike S
Posts: 181
Joined: 16 Feb 2018, 14:59
Location: Salisbury UK

Re: Help!

Post by Spike S »

Robotshop have a huge range of motors and gearboxes. I have used these window winder motors for rugged applications as Jib sail winches for Sailability dinghies. Several years use without any problems and could be what you seek for that "Harry Tate" application.
https://www.robotshop.com/uk/power-wind ... -left.html
Many other motor/gearboxes on that site.
Spike S
(Tune for maximum smoke)
Nick M
Posts: 92
Joined: 19 Dec 2018, 20:39
Location: Camberwell london

Re: Help!

Post by Nick M »

Knew I had asked in the right forum...

I estimate the rpm to be closer to 100

I tried bigger and smaller driving cogs (ranging from heat shrink tube on a spindle to 3cm and 5cm foam wheels off a plane)

If too small the contact area is smaller - but works, larger and the bike wheel spins too fast

so both are possible with right rpm (electric motor from paraglider wouldn't run slow enough reliably, drill fine but better at a reasonable drill speed

I'll look at all 3 options now

Nema 17 might be beyond me unless there is a one purchase box like a servo tester - speeds and torque sound ideal

Preference is always to make something that lasts - probably going to run the marble run as a schools competition in the future and so drive can be used again.

Stupid question - I have some fairly beefy metal geared servos (but in locked down school) and smaller https://www.rclife.co.uk/Corona-DS238MG ... -Servo-22g - Stall Torque: 4kg.cm / 4.6kg.cm - would they work / burn out?

Thanks all - will keep you posted! -

Next installation is an optical illusion so have some time - just finished a nichrome how wire cutter and waiting for bluefoam (now black) to arrive
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