The oldest type is on the far left, the newest is on the far right. For the sake of a reference, lets just number them 1 thru 6 from left to right.
1. The oldest type, known for having a very low melting point. It was 3 copper segments surrounding a white low temp nylon hub and all held in place by a red fiber washer. My first attempt at rewinding was on an arm with one of these but it never ran. I melted the comm beyond use trying to solder the wires to it. These comms usually appeared on arms where the laminations (steel plates) were uneven. This kind of armature was similar to what was used in 1.5 to 3 volt toy motors. They could be found in the early Monogram X-100, Russkit 22, Revell SP500 and other similar motors. <thru 1964> The arm in this photo is that of a later type. I do not have an armature with the uneven plates any more.
2. The brown comm, for me, was a BIG improvement. Although not bullet proof, it was made to withstand higher temperatures and rpms and you could solder the wires to it without melting it down. You could find these on the later production runs of the above motors as well as Cox TT-X100 and even some of the early can drive 16D's. I have an original Monogram X-110 that has a brown comm in it. <1965>
3. The first generation green comm. Shaped identically to the previous brown one. While I don't have any specs to back it up, I'm speculating the green ones were made to withstand higher temperatures still. We weren't having trouble with the comms melting (that problem had now moved next door to the endbells) we were having trouble with them shattering and coming apart due to the progression of winding arms with fewer turns of bigger and bigger wire. Our radio/tv solder wasn't staying on as well either due to the increased temps and revs. I really don't think the Mabuchi engineers ever had a clue that their little toy slot car motors would ever be pushed to the electrical and mechanical limits American teenagers and young men were hurling at them. But why should they care? The more we burned up or blew up, the more product they sold...for now. <1965-1966>
4. Second generation green comm. The only thing I see here is that they reduced the bulk of the comm below the solder tabs. Why? Reduced rotating mass of the comm? Maybe. It certainly opened up more area near the comm for the wires to be wound. It looks like the same green material (bakelite?) as the previous one. I have no way of telling if they tried to "up" the internal strength of the comm with this design. I blew them up too! <1966-1967>
5. Third generation green comm. Now the copper segments were fully submerged into the green material instead of being cut. This has to have been done to get the comms to withstand yet more rpms. It would not make any sense to update a design if you weren't trying to improve it. It was around this time that Mabuchi redesigned almost everything on the 16D except the endbell. The can had new oval cooling holes, there were redesigned comms, there were better magnets and there were faster winds being wound on the arms. Heck, they even installed ball bearings in their motors although the quality wasn't there. Even the price for all these improvements hardly went up. But it might have been too late. Good ole American ingenuity and know how from Georgia and California, Champion and Mura respectively, as well as hundreds of motor rewinders from coast to coast were turning the focus to American made parts and less and less to stuff from Japan. This comm., in a slightly shorter length, were the first ones installed on the new 26D's. <1967-1968>
6. Purple comm. To my knowledge, purple comms were only installed in 26D's. These were slightly shorter in length than their regular comm. to accommodate the motor's slightly shorter length. <1968>
This is by no means the "be all to end all" on Mabuchi's comms. I'm sure Dokk will have some interesting things to add. But, I thought I would gather as much as I could and get it all in one spot. Thanks for viewing.
