Electronics Tech

[CronusTRD]

I went through my second 645mg at the end of the comp. It's just the gears that are stripped, so I'm going to go ahead and fix them for spares or use in some of my other trucks.

That being said, I'll probably go with a HT-7955 for my steering.

I'm running a Tekin Rebel 2 and 8 cell 1500 mah packs, and use between 35T-55T integy lathe motors. I'm not planning on going to Lipo anytime soon.

Since I also plan on adding a DNA Dig w/ a mini-servo shortly, should I go ahead and add a Castle Creations BEC? The Rebel 2 has a 6V BEC in it already. I also did not seem to have any problems when I ran rear steer with dual 645mg servos.

[nathanschmoekel]

The 645mg is a pretty tough servo...how long are the gears lasting? You might want to double check your linkage for binding. Is your servo horn longer than one inch?? long horns make the servos job harder. Make sure your end poinst on the radio are set-up to allow the servo to "relax" at the max steering input.
Another over sight I have seen has to do with the relationship of the horns attatchment point relitive to the end that attaches to the steering nuckle. As the servo sweeps side to side the horn at some point starts to also travel upwards. Usually the "pushing " direction is the most effected in this relationship. I like to set my gear up so the steering rod slopes DOWN to the servo horn so the horns movement is always pushing...never lifting.

[CronusTRD]

Originally Posted by nathanschmoekel

The 645mg is a pretty tough servo...how long are the gears lasting? You might want to double check your linkage for binding. Is your servo horn longer than one inch?? long horns make the servos job harder. Make sure your end poinst on the radio are set-up to allow the servo to "relax" at the max steering input.
Another over sight I have seen has to do with the relationship of the horns attatchment point relitive to the end that attaches to the steering nuckle. As the servo sweeps side to side the horn at some point starts to also travel upwards. Usually the "pushing " direction is the most effected in this relationship. I like to set my gear up so the steering rod slopes DOWN to the servo horn so the horns movement is always pushing...never lifting.

Both lasted about 2 years. One was used for rear steer. Both stripped the thin bronze gear.




My linkage isn't binding. My horn is a 1" plastic hitec arm. When the steering is centered, the draglink is nearly parallel with the draglink. When my knuckles hit their max steering angle, the horn is at the end of its stroke, and not lifting. Even if I max out the EPA, there is no binding.

[nathanschmoekel]

Two years!! ?? Thats a hell of a good run...Nothing lasts forever, I made it a year before replacing my geartrain and thats TWICE as long as most I hear about!!
Reguarding the BEC question....I have been running the castle for more than a year and like it fine. Make sure you also get the Castle Link so you can program it for desired output. oh and READ THE DAMN DIRECTIONS!! It is amasing how many ways people have come up with to f-up the installation of such a simple device

As far as the BEC fixing the geartrain problem, I think that giving the same servo more power under the same conditions would just kill it faster. I can say a digital servo (even of equal power) would be better. The way the power is "pulsed" in a digital servo is vastly more accurate, this difference in how signal is delivered to the servo motor provides more power more smoothly, therby recucing the stress to the geartrain.

[JOOTZ]

what servo arm you guys recomend for the 645 to be used on my MRC, thanks

[nathanschmoekel]

jootz...Its never black and white, so there is not a concrete answer.
This may help though....manufacturer stated servo power is figured based on a load placed one inch from the output shaft (thats what the horn attaches to). If you want to increase power use a shorter horn. The fflip side is that a short arm may not move your wheels far enough. Also realize that a longer or shorter steering arm (the part that attaches to the wheels) will have the opposite effect on servo power and travel.

The way I figure it out is to start with a one inch horn and maxed out steering EPA (end point adjustment) on the radio...If the wheels reach max turn before the servo maxes out I shorten the arm, more power without affecting travel is always best. If the servo maxes out and the wheels can go farther then go longer on the horn or look into shortening the steering arms, use caution and pay attention to the drag link, moving it too close to the axel housing will cause new problems.

Keep in mind ,concerning EPA, that some final adjustment should be made to ensure the servo is adjusted to "rest" at the max point of steering input. If you pick up the front end and radio for full steering the servo should be silent at the end of the stroke. Neglecting this final EPA will result in a short life span for your servo.

[nathanschmoekel]

Jootz...If your real question was plastic or metal.....I say use the stock plastic. They are plenty strong and can often "bounce back" if impacted. The aluminum is stronger from a not breaking off standpoint, but they do bend easily from impact. If you drive in comps aluminum is less risky...If you are non competitive plastic is fantastic.