What's wrong with this RMG?

[John949]

Look at the photo for a few seconds and see if you can spot the problem

 

Look at the motor just under the red wire and notice the shape of the plastic end cap / brush carrier.

This is what it looked like inside

Quite impressive really.  I was given it for spares by a friend so I don't know exactly what happened but I suspect it had been left stalled for quite some time.   

Now this is an old model (280 DL) and I don't know if the newer ones have better protection against stalling but this is what could happen if you leave your winch stalled for too long.

The electronics were 'unharmed' and all it needed was a new motor.  Good brushed 280 motors are getting a bit hard to find as everyone is switching to brushless (much more efficient).  I have temporarily used the core of a very cheap nasty 280.  The quality doesn't seem great but you can't fault the price.  I've been using one in another RMG for several months and it's still working!

https://www.ebay.co.uk/itm/263125618917

[Gordon Allison]

The motor is burned out.

The part you require to repair it is  this...

https://www.sussex-model-centre.co.uk/products/mabuchi-rc-280-motor?_pos=1&_sid=cc712a221&_ss=r

 

That is you replacing like for like. Cos that's what's in them. Quite a simple repair if the MB is still intact.

These motors are often found in childrens toys.

[Gordon Allison]

2 minutes ago, Gordon Allison said:

The motor is burned out.

The part you require to repair it is  this...

https://www.sussex-model-centre.co.uk/products/mabuchi-rc-280-motor?_pos=1&_sid=cc712a221&_ss=r

 

That is you replacing like for like. Cos that's what's in them. Quite a simple repair if the MB is still intact.

These motors are often found in childrens toys.

I'd check the pot too.

That looks damaged.

[John949]

11 hours ago, Gordon Allison said:

The motor is burned out.

NSS

I doubt that the pot would have been damaged by the burn out as it wouldn't have been subjected to a high current (if the rest of the electronics survived).

Not sure about the motor you suggest.  280 is the physical size, R means it's round and C means carbon brushes.  Nothing about the internal windings or number of poles.  If any real Electrical Engineers will shut their ears for a second I'll say that if you use a (relatively) few turns of thick wire you get a motor with high torque but low(ish) top speed, whereas lots of thin turns gives a lower torque motor with higher top speed.  Most of the 'toy' motors tend to be the latter as they are far less likely to burn out if stalled.  The fact that this motor did burn out suggests it is more towards the former type.  The most common application for high torque high quality 280 motors was for electric flight, but nowadays everyone uses brushless motors so high torque brushed 280s are getting rare.  I know that RMG had a motor supply issue for a while and I'm guessing that this was why.  The very latest RMGs use brushless motors.

To replace the motor like for like then more information in needed.  I will try to measure the wire gauge of the burnt out one or maybe someone (Bill) knows the full spec of the motor.  I haven't been able to source the one suggested on the RMG web-site.

If you do use the wrong spec of motor then the winch should still work (both the ones I have do now work) but the different motor characteristic will affect the control laws.  The one I've just repaired is very slow to approach it's target point i.e. it moves fast for a while then slows down and finally moves very slowly before stopping.  Without going into a discussion on control theory I'll just say that I think this is because the motor characteristic is not the one the system was designed for.

[John949]

Been digging a little deeper and a typical 'toy' 280 has an internal resistance of about 3 Ohms whereas the original motor has a resistance of about 1 Ohm - so it would draw about 3 times the current when stalled.  I've tried replacing the 'toy' motor with a patched up real one and the control is much improved.  Still not as fast to settle as a modern 'digital' Kingmax but better than it was.

[John949]

Measured the wire and counted the turns - pretty sure this is the correct motor

https://product.mabuchi-motor.com/detail.html?id=84

Can only find it via China

https://www.aliexpress.com/item/1005001433053867.html

Stall current is 9 Amps - no wonder it burnt out!