Digital.Complex: [mod] Traxxas 2075 servo metal gear swap - Digital.Complex

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[mod] Traxxas 2075 servo metal gear swap Power HD 9001MG

#1 User is offline   aotsukisho 

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Posted 07 June 2011 - 02:51 PM

I had recently stripped the gears in a TRX 2075 servo used in O-Revo's steering. Rather than fallback on the weak plastic gears, I searched around to see if there were any popular metal gear replacements. The general consensus that I found was that metal gears were not really meant to be in the 2075, and whoever managed to fit a different servo's gears in the 2075 had to do some modding.

Amainhobbies had several replacement gearsets available, with the Power HD 9001MG set most closely matching the original Traxxas ones (I used photos to compare tooth count, etc). At $0.89 a pop, I was willing to drop a couple bucks in the hope that they could possibly be used.

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here is my servo next to the brand new metal gears

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opening up the 2075

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a couple of teeth missing on the output gear

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second gear comparison

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third gear comparison

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output gear comparison

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first gear comparison. despite the photo on Amain's website, the supplied first gear is plastic.

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the two output gears, and the different methods of mechanical stop.

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the + on the bottom of the Traxxas gear is for the pot shaft to fit into. There is no such shaft holder in the 9001MG's output gear, which is nice for 360° modifications (no pot interference at all) but not so nice when we need shaft position feedback.

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first three gears fit into the 2075 case nicely. I had to use the Traxxas first gear, as the Power HD one would not mesh with the motor (too small)

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mockup of the gearset without bearings

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there is a slight problem regarding this bump on the post, it causes the second gear to mesh only with the upper half of the first gear output teeth.

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a minute or two of Xacto work later

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it's not much, but every little bit helps.

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mesh is still not 100%, but it's much better. I would've filed it down more, but then the mesh with the third gear would suffer too.

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the servo horn screw for this metal gear thankfully is standard M3 (are you listening, Hitec!?)

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threaded all the way down, in preparation for my pot feedback solution...fill it up with hotglue

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and shove it down before it cools. It does not have to stick particularly hard, since the pot has virtually no torque resistance. The only thing I can think of that will break the glue is heavy vibration or impact if the glue did not make a clean contact with the brass. There shouldn't have been any considering the gearset is new, and I wiped off all the grease on the pot shaft (but not the surrounding areas) as well.

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2075 reassembled. output spline is standard Futaba (25t). time will tell if the hotglue solution is fine.

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now it weighs in at around 52g, up 7g from the standard plastic gears.

I also took two videos demonstrating the successful gear swap. The first one is testing with the case still off, and the second one is testing with the servo fully reassembled.





I am extremely happy with the results. There is as little play in the gears as before despite it being MG now, and at this price I can't complain about anything. Unfortunately there is only one gearset left in stock at Amain. I just have to see if the hotglue will stick hard enough, and even if it doesn't I have replacement adhesives available.

I will try to do a side-by-side comparison on the modded 2075 servo with a standard one, but that will have to wait until I do a teardown on O/B-Revo.
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#2 User is offline   aotsukisho 

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Posted 06 June 2013 - 10:54 AM

I should point out that this servo has been used for a long time for the e-conversion Revo chassis as the mechanical brake servo, and it's still working well.
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