I'm looking at rebuilding a Kato 103 chassis to fit larger wheels, but the worm wheel is integrated to axle so can't be re-used.
Anyone know a replacement worm wheel that would fit ?
Tom
The axle with the worm wheel is actually an axle muff as the chassis is in a way split-frame, and the axles run in pin-point bearings - from memory molded into the plastic side frames (I have one that runs without the metal base plate attached!) so whilst it might be possible to remove the wheels and their stub axles from their geared muffs any replacement wheels will also need to have pin point axles (or axle ends) and stub axles the right size. If you can get the right length metal pin point axles then it might be possible to cut the gear wheel out from the muff and bore it out to fit the new axles and then arrange for the pick ups to contact the backs of the wheels, but the wheel diameter might be restricted by the top of the plastic molding.
As an alternative you could use the same drive set up - worm on both motor shafts driving both axles - that the Kato and OO gauge Tenshodo spud uses. The Tenshodo gear sets are sold separately (Nigel Lawton used to sell them, not sure about now) and it might be possible to knock a supporting structure in plastic sheet (or even 3D print something if one has the time / skills/ etc.).
Quote from: JulienW on July 24, 2013, 11:01
....The Tenshodo gear sets are sold separately (Nigel Lawton used to sell them, not sure about now).....
Nigel Lawton does still show the Tenshodo gears as in stock for
Yes, my plan was to replace the upper plastic part with a 3-d printed part. I was thinking of using longer axles with outside cranks to make a steam loco chassis.
It looks as if the existing gear is straight cut, so presumably any spur gear the right size would work?
Quote from: tebee on July 26, 2013, 11:47
Yes, my plan was to replace the upper plastic part with a 3-d printed part. I was thinking of using longer axles with outside cranks to make a steam loco chassis.
It looks as if the existing gear is straight cut, so presumably any spur gear the right size would work?
If they are not to fine a pitch then yes a strait cut gear should mesh with a worm, but I think a skew cut gear will be more efficient (less wear on the gear and strain on the motor). I recently picked up some 64DP worms make many moons ago by Mike Bryant and after asking about them on the 2 mm Association's Yahoo group was told that whilst the gear does not necessarily have to be skew-cut it is not however best engineering practice, and that with the coarser 64DP gears it is not so much of an issue. Another tip was to make the gear wheel(or thin it down to) no wider than about 1/3rd the width of the worm and also 'overcut' the worm, which might have already been done with the Kato bearing in mind how narrow the gears are.
However the gears from the Tenshodo sets are skew cut (well, probably molded but same difference!) and are wide enough to show it. Those on the Kato might also be skew but from memory they are not too wide and may be too narrow so show any 'skew'.