Hi CB,
Re 'Faraday Cage: I see what you're getting at, of course you are correct that a sealed and grounded metal box would shield the surroundings from spark generated RFI. The 'box' would need to be 'hermetically and electrically sealed', not easy with prop shaft an' all. One hole is enough and Whoops, all those nasty waves have escaped😡.

But actually a Faraday Cage works the other way round!
It's purpose is to protect people and 'things' inside the cage from outside influences such as high voltage discharge (e.g. lightning) or unwanted radio or other high energy waves by conducting them around the outer skin of the cage to ground.
I sat in one during my years of development of mobile radio systems to try to make sure that my test measurements weren't being falsified by external influences. I also didn't want to ruin the tests and alignments my 'bods' were doing on the current production equipment just outside😉

I also had the pleasure 🤔 about 30 years ago of standing inside one at the Deutsches Museum while about a million volts was fired at it!
Hair raising😲 but I'm still here to tell the tale😊 and bore the pants off you all😁
Happy suppressing all, cheers Doug 😎

Hi All. all good advice for the normal brushed motors in cans with carbon brushes. But the Taycol is a totally different animal! it has no carbon brushes. They are simply stamped thin copper or phosphor bronze sheet.
Contrary to carbon brushes they need OILING to reduce the wear and sparking!
Attached are some pics from my Taycol Target renovation and modification to graphically illustrate the point. Pic one 'Before', pic 2 the new phosphor bronze brushes I made.

BTW: don't EVER put oil on your carbon brushes! Try it if you're curious, but then buy a new motor or try to find some replacement brushes 😉

If you run the Taycols dry they wear the brushes through until they have a hole in the middle and spark like crazy Pic 1. You can put what capacitors you like on, you'll still get interference especially at 27MHz.
Pic 3 shows the effect this has on the commutator. Pic 4 shows the renovated commutator, there was more 'meat' left on it than I expected😊
Pic 2 shows the new brushes I made from phosphor bronze sheet.

The spark energy density spectrum peaks in the HF band (e.g. 27MHz!) and falls off rapidly in the VHF band (30MHz upwards) to virtually nothing in the UHF and Gigahertz bands. That (and the frequency hopping process the 2.4Gig sets use) is why they don't suffer such interference.
BTW: as a matter of probably no interest 😉 most sets only use 16 or 32 of the 85 frequencies available in the band! 😲

The capacitor values given above are unusual and will only work with a 'canned' motor, which the Taycol ain't! The norm for a standard canned motor with carbon brushes would be 0.1µF across the terminals and 0.047µF from each terminal to the can, which with a Taycol you ain't got!
Earthing to the prop shaft is also a problem. Where do you connect the wire? There's no 'can'. Frame? That's paxolin! try soldering to laminated iron core if you want. Good luck. Won't achieve much even if you manage it🤔

Once again I ask which Taycol you have, as the construction varies and hence the suppression methods / connections.
Imperative is the condition of the brushes and commutator to minimise the intensity of the spark generation in the first place!
Also important is how you are controlling the speed: also 'Period' with a Bob's Board or resistor coil and servo driven wiper??
These can also be spark sources😡 Never mind wasting precious battery power as heat😲

If you want to convert to using an ESC with proportional forwards and reverse, which Taycol field motors can not do without reversing the polarity of EITHER the field coil or the rotor coil but not both, I can show you how.
I did it with Dad's old Taycol Target, see my Build Blog 'Sea Scout Jessica'. Pic 5 shows my Taycol target dismantled, before the renovation.
Pics 6 & 7 the reassembled motor after renovation.
Pic 8 shows the motor voltage across the terminals before the conversion, complete with gigantic sparks of amplitude 100% of supply voltage.
Pics 9 & 10 show the waveform on the terminals of the modified motor at slow and fast speeds, hence different pulse width; broad pulse more speed, narrow less speed.
BUT: virtually NO SPARKS😊 and no capacitors😊
Trick is in the bridge rectifier used to connect the motor to a standard brushed ESC. The diodes in the rectifier suppress the sparks😊
Pic 11 shows the wiring 'lash-up' I made to test the motor before mods. Pic 12 the PSU used for the tests. ESC is a 30A Graupner Navy.
Instead of TX and RX I used a simple servo tester to drive the ESC.
Scope used speaks for itself! As expected speed control was possible but no reverse.

Media File 1 Vid shows the renovated motor running but unmodified, complete with sparks😡 Sorry Dave_M, I can't upload the ozone smell🤔
Media File 2 shows the scope display of the unmodified motor test, complete with the sparks that cause the kind of interference you are suffering from.
Wanted to add the final vid showing the clean waveform after the mods but it's too big for the site: 30MB max and the vid is 47MB 😭
Penultimate pic shows the circuit used to connect to a standard ESC (Brushed!) for full remote control proportional forward and reverse.
Final pic shows the test set up for the fully modified motor. Note 4 connections: 2 to field coil, 2 to brushes (i.e. rotor coil) as per circuit diagram of the interface board.
Have fun, cheers Doug 😎

Could try general suppression capacitors arrangement, I have also seen the can or frame of a motor connected to earth via a wire soldered to the brass propshaft.

You could shield the motor by enclosing it in a metal box, be careful not to short circuit anything, similar to Faraday cage .

Presumably you have looked at the Taycol site? This page looks like the one you need... http://taycol.tk/install.html

Hi RAFCRASHTENDER, still waiting to know which Taycol you have!
Depending on the model the mods to make these old 'one way' field motors go forwards and backwards and suppress the interference, are a little different! Cheers Doug 😎

HI Mate, welcome to Mayhem, just a thought, I to prefer a period transmitter with my older models, I have a Macgregor trany which our club guru converted to 2.4gh with a Futaba module, works brilliantly, best of both worlds

Mark

Hi RCt! which Taycol is it that you have?
On this site you can find my posts about converting a 1960s Taycol Target to run both fore and back under RC. There were several Taycol motors at that time. I can also advise on converting other types.
The conversion also solves the interference problem 😊
Cheers Doug 😎