View Full Version : crt.5 plastic spur?
09.06.2007, 12:45 PM
Does anyone have the ability to make plastic spurs?
I have none of the skilz required, but I'd really like to obtain a plastic spur gear for my crt.5 that is a drop in on the diff and motor mount and is 32p instead of MOD1.
Anyone know if Mike or another company could make a custom gear like that?
09.06.2007, 12:47 PM
mike was working on one but I believe it got pushed to the side since the hardend steel pinions were working very well.
09.06.2007, 12:51 PM
re: the hardened pinions. That's good to know - I've done the metal/metal thing before with a hardened pinion/spur on a 1/8 buggy and all it did was shred the pinion after about 1 hours running. I was assuming the same with the CRT.5, but maybe since it is a lighter truck it is easier on the hardened pinions. My truck has only been run lightly a couple of times testing the BL conversion and setup, so no major pounding on the gears yet.
I would still prefer the 32p, and a nice plastic spur would make for a quieter ride.
09.06.2007, 01:17 PM
Running steel on steel is entirely possible IF the following two criteria are met:
- The mesh is correctly set and consistent. This requires a mount that does not flex causing the mesh to vary. Using a mount integrated with the center diff is ideal because any chassis flex will shift the motor and spur at the same time maintaining a consistent mesh. Designs which have the motor attached elsewhere on the chassis cause inconsistent meshing during chassis flex.
- The tooth geometry of both spur and pinion are compatible. If you take a look at the regular steel pinions vs the hardened ones Mike sells, you'll notice the teeth are shaped differently. The regular pinions bind and catch on steel spurs because of this. This pic helps illustrate this:
You can see the width of the tooth tops are different as well as the shape and angle of the slopes.
This thread (http://www.rc-monster.com/forum/showthread.php?t=4383) discusses some of the finer points on the subject.
Anyway, using a plastic spur requires a whole new design to be made, which is only compatible with the CRT.5. The typical Kyosho 44/46T spur is overall thicker so it pushes the CD mount requiring new chassis holes and center shafts. Also, different bearings are used.
As Gixxer said, Mike was looking into it (and still is, unless things have changed), but the steel/steel solution works well, so it was put on the back burner for now.
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