Capacitors on motors

[mrbassman]

Is it really necessary to use the capacitors on the motors? Everything I'm reading says to use one across the terminals and one from each terminal to the case. I'm building a warship that will have 4 Speed 400's, (one driving each prop), and I'm wondering what the correct capacitors would be, if they're needed at all.

Thanks, Ken

[patmat2350]

Look inside a running brushed motor... see the sparks? Those make e-noise, which can confound your receiver. Capacitors help reduce that.
AM radios are most susceptible, FM way less, FM-PCM (including 2.4 GHz), way way less.

[der kapitan]

Bassman, it's best to install them---.

[JOHN SCALE BOAT]

Yes, you want to use 3 caps on each motor. The spec is .01 uf (micro farad). These can be picked up at your local radio shack or electronics supply house. Looks like these- http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXBJ87&P=ML

[BigDutch]

What method do you guys use to solder cap leads to the motor case? I can rarely seem to get the solder to stick to the steel.

[johnmca72]

What method do you guys use to solder cap leads to the motor case? I can rarely seem to get the solder to stick to the steel.
I drill & tap a #2-56 hole in the case, in a location where there's clearance underneath. Then I screw a #2-56 screw (short - about 1/8" is plenty) into the hole, with capacitor leads wrapped around the screw as if it were a terminal.

I solder the capacitor leads to the motor terminals, along with "pigtail" leads with appropriate connectors. Trying to use the existing terminals after they've had capacitor leads soldered onto them usually doesn't work very well.

JM

[JOHN SCALE BOAT]

To get solder to stick to the motor case. First take a file and lightly ruffen the area. Then use a 60+ watt soldering iron and flux to apply solder to the case. In rare cases use a drop of acid flux. Then clean of the flux when finished.

[Olscuzbut]

I just use a spade lug under the mounting bolts on the engine mount for the case contact.

[Rob_P]

The notes that came with my Graupner Speed 500 said that they were already installed. They are not visible outside the can but I have noted a fine wire coming out of the can to each terminal.
I'll give it a go and see how it holds up before adding "additional" ones.

[pkboo]

To get solder to stick to the motor case. First take a file and lightly ruffen the area. Then use a 60+ watt soldering iron and flux to apply solder to the case. In rare cases use a drop of acid flux. Then clean of the flux when finished.
This is also the way I do it. You need a 60+ watt iron because the can needs to get good'n hot. I do recommend flux but then you need to clean it up afterward and varnish the spot to avoid rust. This does not work on aluminum cans. Great pointer John :) Boo

[pompebled]

The notes that came with my Graupner Speed 500 said that they were already installed. They are not visible outside the can but I have noted a fine wire coming out of the can to each terminal.
I'll give it a go and see how it holds up before adding "additional" ones.

The Graupner motors that come with capacitors installed, only have two; from the terminal to the can, this will work in most applications if the signal leads can be positioned far away from the motor leads.

In a cramped FE, I always install a third capacitor between the motorleads.

Regards, Jan.

[McDuck]

This picture my help in the location of capasitors.[IMG]

[mrbassman]

The .01 uf that John Scale Boat recommended in post #4, is that universal for all size motors, or do different size motors need different size capacitors?

Thanks for the help guys.

Ken

[McDuck]

The model dockyard do Motor suppressors
there Ref: EL100 in the motor mount & suppressor section
They are more than suitable for what you want.

[mfr02]

The .01 uf that John Scale Boat recommended in post #4, is that universal for all size motors, or do different size motors need different size capacitors?

Thanks for the help guys.

Ken
A wide range of values works with pretty much all motors. Its the type of construction of the capacitors rather than the capacitance that is important for suppression of RF.
Unless the motors are very high voltage, the same capacitor does for all.

[johnmca72]

A wide range of values works with pretty much all motors. Its the type of construction of the capacitors rather than the capacitance that is important for suppression of RF.
Unless the motors are very high voltage, the same capacitor does for all.
Note that you'll want to use NON-polarized capacitors. In other words, if there's a stripe, a "+", or 1 lead longer than the other, don't use them.

Also, pick a voltage rating that's several times your nominal voltage. Since you're trying to filter spikes, it stands to reason that those spikes are liable to be 3-4 times or more whatever your voltage is. For example, I run 6V systems almost exclusively, & use 35V or higher-rated capacitors.

JM