Hi, I'm just in the progress of altering the hole in the motor block on older locos (with either large or small disk armatures).

Some loco frames have enough metal around to increase the hole size from 2 mm to 5 mm (ball bearing) and some of the motor bogies do not have metal to do this.
I've bought a putty usually used in the automotive industry, its a compound you knead until the 2 compounds are mixed together and you than apply it to the area. after it gets hard like steel and you can drill it, sand it etc etc. it does not bond on painted surfaces.

any my first attempt was last night and aI applied the compound to the area of the motor bogie (diesel loco Märklin 3074) you can form it to the shape you like and usually it only takes you about 10 minutes to do this, let it sit for 4 hours and than start drilling the hole.
Well I let it dry for more than 12 hours and took my drill with a centred drill bit (5mm) and started drilling from inside out, my centre drill bit unfortunately wasn't long enough to go right through the metal frame so I tried if from the outside, unfortunately at the end the compound came loose from the motor bogy and I've glued it back on again with superglue, it wasn't my intention to do this, I've taken the paint off but for some reason it didn't stick to the metal motor , I don't think it will make much difference, there is a solid 2mm metal thickness and the rest (compound will support it even more. I'm still waiting for my 5mm ball bearings so I can't show you the end result but will do so in the near future when the ball bearings arrive.
I will continue the progress with other locos such as the 01 097 (3097) 23 014 (3009 = DA 800), 3011, 3013, 3016, 3028, 3023, 3046, 3047, 3054 and the list goes on, I'm slightly concerned about the BR 24 (3003), if the compound doesn't stick and I'm trying to drill a 5mm hole it could finish up in a disaster as the current area around the hole is big enough just for a 2mm shaft (current size of shaft) and to build around the surface area I need at least 7 or 8mm of compound around the existing 2mm hole. the room is there to extend it but if it breaks off there wouldn't be anything there to hold on to and by drilling a 5mm hole the drill bit may shift to another centre position which than makes the whole exercise a disaster.

Matt, I never saw your posting and you've done it , I bought some centre drills and they are terrific, they drill perfectly into the bruhs plate leaving no residue and the same with the motor block, did one on a costumer's loco (BR 86 (3096) and it went well, I don't have these special tools like you have I drill my holes by hand with a drill and line the hole up vertical and horizontal, at very low speed, I start from the inner side and than the outer side. my centre drills aren't long enough to drill it all from the inside.
the locos you've mentioned there is enough metal around to drill a 5mm hole without the worry it may go beyond the diameter of the existing hole like the BR 24 as mentioned.

I've tried mine before hand, only drilled the brushplate hole (4mm x 1.5mm) and left the motor block hole at 2mm and you can hear the armature isn't running as smooth so there is quite a bit of friction still noticeable (BR 216) whereas with 2 ball bearings it runs freely (BR 86)

John

Howard, anything is better than the rotor being stuck in a metal to metal situation, my 5mm x 2mm basll bearing the shaft is not as tight as I would wish but it does the job with other words no its not a tight fit and I don't think any of them are. they fit into the ball bearing without any trouble, so long the rotor shaft is turning without too much resistance I have had no trouble with over 200 locos being fitted with ball bearings.

John

Howard, I'm using Dynasteel, where do you get Devcon ? I'll have a look under google search.
thanks John

Matt, should have done this years ago but I have to be satisfied what I've got (5 pole motors) and the conversion isn't cheap comparing taking out the 5 pole motor and replacing it with a SB-Modellbau motor.

there are a few modelers who have gone down this path and with great success especially the quite run of the loco(s).

John

For those who may have missed it, there is A LOT of info in John's thread here: https://www.marklin-user...ving-parts--motor-shield

Matt, I have received some brush plates this time around (various conversion sets) and the brush plate seems to be ok, they may have altered the tooling to make sure the brush
holder is sitting tight against brush plate, with these conversion sets now we are experiencing another problem, there are parts missing, either the longer screws are missing or the solder pad is missing or both. quality control, where are you ?

John