Sometimes I think Quality Control is a totally unknown concept in certain parts of the far-east. Some of the stuff is high quality, but there are a LOT of times when what you actually get is a kit of mostly usable parts. ALL of the SCX10 rear axles I ordered came from different vendors, but the same supplier, and none of them were really usable when the arrived. All of them are almost impossible to turn. I chased that problem back to the fact that they arrived with an interference fit between the spider gears in the differential. I had to remove 0.3mm from the backside of each axle gear before things started to work properly. BUT, they are fixable.
I ordered some plastic bushings for the knuckle pivots on the powered steer axle I'm building. They were SUPPOSED to have a 3mm ID, it's under 2.8mm. Fortunately the OD is correct so they also are fixable.
I ordered drive shafts from 3 different manufacturers, 2 out of the 3 suppliers have the knuckles properly phased to minimize vibration. The third supplier... not so much. The knuckles are are least 10 degrees out of phase, and I'm not sure if there's going to be any fixing it.
And then, I've got a gotcha that's kinda my own creation. ALL of the drive shafts that I ordered are SUPPOSED to fit an SCX10, come with a 5mm bore and have drive pins that are threaded M4 on one end with the other end turned down to 2.5mm. My axles are SUPPOSED to be SCX10 replacement axles, but they all have holes for 2mm drive pins in the 5mm OD pinion shaft. I could bore the pinion shafts out to 2.5mm, since the Kong axle that I have has a 5mm pinion shaft with a 2.5mm drive pin hole. The Unimog replacement twin motor/2-speed gearbox that I got as a power unit has 4mm OD output shafts that are threaded M2.
So, here's my first dilemma, do I modify the pinion shafts? Or, do I modify the drive pins? Initially I was leaning towards modifying the drive pins, now I'm not so sure. If I modify the pinion shafts, I just punch the drive pin holes out to 2.5mm and call it a day. If I modify the drive pins by turning them down to 2mm, then I also have bush the hole in the drive shaft down to 2mm. Otherwise they'd be, to quote Wes from Watch Wes Work, "floppin' around like a hot dog in a hallway." Metal fatigue would probably cause the 2mm pin to break off in a short time. I think I just talked myself into modifying the pinion shafts.
My second dilemma is that the output shafts on the Unimog transfer case have a 4mm OD. Bushing the transfer case end of the drive shaft down to 4mm is no problem. They also have a pre-machined flat that is threaded M2. My first thought was to bore the M2 threads out to 2mm, since they are effectively that size now. I was planning on just having one drive pin that would work on either end, but that's just gonna make a lot of extra work for myself. I think what I'll do for the transfer case drive pins is cut a chunk off the 2.5mm end of the pin and turn the stub down to about 1.5mm - or whatever will fit in the M2 threads. The set screw on the flat will be the actual clamping/driving force, the little stub is just extra insurance if the set screw comes loose.
Don
