Autopilot motor brushes

[KAM]

Before I make some I was wondering if anyone knew a supplier of very small leadless brushes. Dimensions 3.5 x 2 mm. Failing that any tips for cutting bigger ones down. Was thinking I might need to make a jig.

 

[PaulRainbow]

Might find something here : Carbon Brush spare parts | TDSpares

2mm sounds thin ?

 

[MontyMariner]

Also try Carbon Brushes with Shortest Side up to 5mm - Free Delivery - Carbonbrushes.uk

 

[Plum]

Before I make some I was wondering if anyone knew a supplier of very small leadless brushes. Dimensions 3.5 x 2 mm. Failing that any tips for cutting bigger ones down. Was thinking I might need to make a jig.

The electric motors in autopilots are often standard off the shelf ones such as this MFA 719RE-540/1 4.5-15V 3 Pole DC Motor 14500RPMDefault Title
What make and model is your autopilot? Are there any markings on the motor?

 

[KAM]

The motors in my rams have 2.3mm diameter shafts. Which aren't so easy to source. I replaced one probably 5 years ago it's been quite reliable but I've found the planetary gearbox gears have started to wear. I suspect it's due to the cheap replacement motor not being centred correctly as it does not have the same locating shoulder and spigot. I did get a couple of replacements recently but they were even cheaper and worse quality (race to the bottom). The motor in my second ram looks in very good condition but is starting to fail due to worn out brushes. If I can clean up the commutator and replace the brushes it should have a few more years left.

 

[fisherman]

I used to get them from a specialist supplier, they were silver-rich apparently and expensive, £50. My local electrical engineers found them, so a bit of googling might help you. There are brushes galore on Ebay, of many sizes, got some for a router recently. Not that small though

 

[KAM]

None that small. Might raid the toy box in the attic. There's a few old electrical toys with motors.

 

[fisherman]

micro brush supplier
Micro Carbon Brushes - Anglo Carbon & Contacts Ltd

 

[KAM]

Bought some cheap brushes and easy enough to cut down to the right size. Seemed to fit OK but the motor refused to run. As a last resort I dismantled the motor and cleaned the commutator. Now running with the original brushes. The attempt at new brushes may have contaminated the commutator but not sure. I should have changed back to the original brushes before opening up.The autopilot is running fine now but no doubt will fail again at a critical moment.

 

[MontyMariner]

Try using one old and one new in turn to see if you have one dodgy one or both are rubbish.

 

[rotrax]

The Italian motor used in the Raymarine autopilot ram has no slots in the brush boxes. The springs are unable to apply pressure when the brushes wear a small amount as they hit the edge of the brush boxes.

I cleaned the commutator and bent the brush springs so they had a vertical bit to press the brushes onto the commutator.

Worked great.

I sourced some VW wiper motor brushes of the same dimensions as spares, never used them.

 

[KAM]

There are no markings on my motor but the brush boxes have slots. Not sure what the length of the brushes should be. They looked about 30% of the box height. The symptom was that every couple of hours the motor would just stop. I had thought maybe the brushes had worn so short there was insufficient spring tension left but could just have been the commutator slots clogged up.